# Bass trap placement - high or low? Does it matter?



## JohnJSmith

I got a set of 4 Acoustimac 48x24x4" corner traps, and I'm wondering where to put them. Should they go up near the ceiling or down by the floor or in the middle? Or does it make any difference? I don't want them right on the ground because I don't want my cats mistaking them for scratching posts, but I don't have to put them right up against the ceiling to keep them out of claw range.


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## DanTheMan

I'd keep them away from the cats for sure. Other than that you can take measurements to see where they are most effective. Probably won't be where you hope............. None the less, more is ultimately better than few.

Dan


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## JohnJSmith

DanTheMan said:


> I'd keep them away from the cats for sure. Other than that you can take measurements to see where they are most effective. Probably won't be where you hope............. None the less, more is ultimately better than few.
> 
> Dan


Thanks, Dan. Does it matter if I have them firmly attached to the walls when I'm testing? Or can I just set them in place and take some measurements?


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## DanTheMan

Leaning should be fine.

Dan


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## kam

> Other than that you can take measurements to see where they are most effective.


But is there any general guidance on the issue of vertical positioning on a wall? 

If the ideal place was found to be in the centre of a wall (between floor and Ceiling) would it make a significant difference to place them at the lower part of the wall - would it be the case that it would not be worth having them at all if you did this, or would it for example led to a % deterioration in performace?


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## ojojunkie

good that I found this thread, next week I will be installing my DIY bass trap... :bigsmile: will check it back to get more info.. :jiggy:


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## DanTheMan

kam said:


> But is there any general guidance on the issue of vertical positioning on a wall?


It depends on who you talk to.


kam said:


> If the ideal place was found to be in the centre of a wall (between floor and Ceiling) would it make a significant difference to place them at the lower part of the wall - would it be the case that it would not be worth having them at all if you did this, or would it for example led to a % deterioration in performace?


It would make a difference. Hard to say how much as every room is radically different. I'd place them somewhere near speaker/ear height in the corners behind the front main speakers d/t their broadband nature, but others could state reasonable placement options elsewhere.

Dan


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## kam

Thanks, would it make a difference on placrement of bass traps if using these tall floor standing units? Seeing that the cones go all the way down from the upper tweeter, I was thinking that the panels would go on the walls in the same vertical area (I will of course plot the reflection points to mark horizontal positions on the walls).


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## DanTheMan

Everything makes a difference. In general, you want to absorb the whole front wall with something thick like 4" thick or so. Bass trapping the front corners with broadband absorption like John has. The next absorption point would be your first ipsilateral reflection and then the middle of the rear wall. Some people will also recommend absorbing the first reflection from the ceiling.

Dan


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## kam

Thanks, I understand that but my question is about the vertical placement of the traps at any given location. For example, on the rear and side wall reflection points, would it be ok to place them from skirting level up to match the height of the speakers shown, or do they have to be from the centre of the tweeter up?


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## DanTheMan

What effect are you going for?

Dan


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## JohnJSmith

DanTheMan said:


> The next absorption point would be your first ipsilateral reflection and then the middle of the rear wall.


What's an ipsilateral reflection?

Here's what I have so far. Looking from the back of the living room to the front, you can see I have bass traps in the front corners. They're just sitting on top of the subs right now. There's a big opening to the left that leads into the dining room.










Looking to the left, you can see the opening, and there's a big blank section of wall.










Looking to the right, you see the outside wall of the house with two windows.










And from the front of the living room to the back, you see the other two bass traps, which are just resting on chairs right now. There's another big opening at the back of the room. As far as I can tell, the cocker spaniel has no measurable effect on sound quality.










I'm thinking about getting some big movie theater style curtains for the back. I'm not sure how the dining room opening might affect reflections. That side of the room is definitely quieter. My right front speaker is at -4 dB to bring it in line with the left.


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## DanTheMan

ipsilateral--same side

Dan


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## JohnJSmith

Same side as what?


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## DanTheMan

The loudspeaker.

Dan


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## Crossblade

If you put them in the corners - as John did - as bass traps, the height doesn't matter. The standing waves are in the whole corner. See this calculator, representing the locations of the standing waves. Your panels are most effective at this places. http://www.hunecke.de/en/calculators/room-eigenmodes.html
If you absorb early reflections (put them on the left or right wall, between you and the speakers) they would ideally be from floor to ceiling. However, I'd try to cover the area of the speakers at least. In your case, put them slightly above the floor, to where they reach in height.


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## DanTheMan

The dark regions in that simulation represent high pressure regions and are technically the least effective place to put a broadband absorber to reduce bass problems. Placing them in the light regions would be the most effective--where particle velocity is at a max. If you had a diaphragmatic absorber, the dark area would be the most effective place.

Dan


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## TheGreek16

show pictures of bass traps in your room


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## liteglow

Hello 

There are so many threads about bass traps that I did not want to start my own.
But I have a question, Why should I use bass traps?

I have a 5,4x3,4m square room, and in the middle of the room I have a -10db drop at 20-50hz.
If I place bass traps in the corners, roof etc.. will that increase the volume in this frequency levels ?



cheers


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## sdurani

It's possible that your 10dB drop in level isn't actually a drop, just a normal level valley between two loud peaks. 

Bass traps work by absorbing bass energy. As such, they can't increase the volume of the dip as much as bring down the peaks on either side, giving you smoother bass response. 

Once the bass response is smooth, you can raise the bass level to whatever you like.


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## liteglow

I understand. But why make a smooth bass on the corners when I only listen i the middle og room.

So basicly i need to reduce peak in corners, smooth out the levels and then turn up the volume on the sub?


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## rkeman

Corner absorbers smooth bass response evrerywhere in the room, not just in the corners! The reason for placing absorbtion panels across a corner, as illustrated in the photographs earlier in this thread, is that it increases the bandwidth of the absorption and wide-band absorption avoids a "dead" sounding room. Using thicker (e.g. 6" or 8") and denser material also allows more effective low frequency absorption without significantly increasing the size of the panels.


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## liteglow

ok, sorry for asking maybe some obvious question for somebody, but I try to learn as much as possible.

I start to understand what you say, and I also understand about the point of place bass traps and acoustic treatment around in the room to remove echo and reflection of sound you dont want to hear where you sit.

how do I know if my subwoofer are smooth or not?
I have REW and UMIC1, done some testing and can try to make a new thread about my problem.

But if my sub (PBS 13 ULTRA) is to big for my room, is there any solution to make the bass more loudly in the center of my room, or is there no hope for me ?
The perfect sound is when I sit all the way back in my room, I can hear and feel the bass below 16hz perfect and nicely. when I sit in my couch in the center of my room it feels like a dead spot with no sound at all (sound=subwoofer) 

So my last hope is that maybe bass traps or other treatment for my room can solve my issue.
if not I feel it was a big mistake to buy a Hi End speaker if my room is to small :rolleyesno:


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## rkeman

A typical room has many areas of cancellation and reinforcement that vary by frequency. The best compromise is finding listening and loudspeaker locations that yield the least variation and yet provide good imaging. A central seating position is often among the worst choices, as you have discovered. Try moving the seat closer to the rear wall and/or the subwoofer to a different location. A relatively easy method for optimizing placement is to place the subwoofer at the listening position and listen at the various possible locations that the subwoofer could occupy. Remember that the subwoofer doesn't have to be in a corner, against a wall or even near the satellite speakers.


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## liteglow

rkeman said:


> A typical room has many areas of cancellation and reinforcement that vary by frequency. The best compromise is finding listening and loudspeaker locations that yield the least variation and yet provide good imaging. A central seating position is often among the worst choices, as you have discovered. Try moving the seat closer to the rear wall and/or the subwoofer to a different location. A relatively easy method for optimizing placement is to place the subwoofer at the listening position and listen at the various possible locations that the subwoofer could occupy. Remember that the subwoofer doesn't have to be in a corner, against a wall or even near the satellite speakers.



You see this is where my problem begins...

I have with a great help from 1 of my friend, moved my 71kg heavy sub around the room in all possible locations.
Even in the middle of the room did we test the sub.
We did measure the difference each place with my DB tool to check the variations, usually 20 and 50 hz.
At every location we tried the sub, we did also adjust the phase direction in the subwoofer EQ settings.

The end result was that no matter where we did place the sub, there was always a -10 db drop on the center of the room, and in the corner\front\rear the sound was optimized ! (as we also would suspect in many years of HiFi)

So you tell me to sit somewhere else in the room? 
I have a 110" screen in the front, the 1,5 meters on the rooms backside is where I have a work desk (this was a deal for the Lady in the house), and I have moved the couch as long forward as possible to not be uncomfortable on the screen.

So as you see, there is no room for moving the couch anywhere in the room :dontknow:

I see only 1 radical solution !!
And that is to set up a small tiny wall behind the couch to make the room even smaller, but then I will be sitting all the way back in the room, making sound better where I sit !
When I hang up a cover (moldon?) behind the couch the DB meter indicate some higher values.


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## rkeman

It sounds as though there has been much experimentation with subwoofer position and phase without any significant improvement. Although unusual, perhaps the longitudinal and axial modes are arranged such that the center listening position has a broad null from 20-50Hz that simply cannot be addressed. The next suggestion would be to lower the crossover frequency of the satellites into the 40-50Hz range and test using the "all stereo" mode on the preamplifier/processor. Multiple bass sources tend to blend the room modes attenuating deep nulls and large peaks and with all the speakers and subwoofer operating the best possible room curve should emerge. Don't use high levels for this test if the low frequency response of the satellites is limited.


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## liteglow

Sounds like there is some testing that can be done.
I think I will start a new thread about my problem, and add pictures of the room including schematic etc..  
as soon I got time...


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## sdurani

liteglow said:


> But why make a smooth bass on the corners when I only listen i the middle og room.


It is reflections from the walls that are causing the cancellation (drop in level) in the middle of the room where you sit. Placing absorption/traps on the walls reduces those reflections, thereby reducing the cancellation at your listening position. To make more efficient use of absorption, you can place the traps where walls meet (corners). 

Also, is it possible to move your subwoofer to the middle of the room where the dip is occuring?


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## Babak

sdurani said:


> It is reflections from the walls that are causing the cancellation (drop in level) in the middle of the room where you sit. Placing absorption/traps on the walls reduces those reflections, thereby reducing the cancellation at your listening position. To make more efficient use of absorption, you can place the traps where walls meet (corners).
> 
> Also, is it possible to move your subwoofer to the middle of the room where the dip is occuring?


Some helpful reading that addresses all those topics :

http://www.harman.com/EN-US/OurCompany/Innovation/Pages/WhitePapers.aspx?CategoryID=White papers

There are also very good chapters in Floyd Toole's book. 
Some takeaways for me, that could help in this discussion :

Comb filter effects (dips through cancellations) are clearly measurable.
But several listening tests showed that listeners don't perceive them very well (that can be explained by the way how our hearing works). 


Deadening all reflections is not a good thing, as reflections (mainly from 60° left and right) are crucial for spaciousness.
If one dampens all the reflections, the perceived soundstage will be flat. 

It would be better to build on the Precedence Effect :
The speakers and the listening position should be positioned where the traveling distance of the first reflections are at least 1.7 metres longer than that of the direct sound (more than 5 ms time difference). 

The reflecting walls then should be treated with diffusors rather than absorbers. 


And as Dan already mentioned :
Bass traps work best when not placed on the corners where sound pressure is at a maximum but in between, where sound velocity is the highest. 

Cheers 
Babak


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## sdurani

Babak said:


> Comb filter effects (dips through cancellations) are clearly measurable.
> But several listening tests showed that listeners don't perceive them very well (that can be explained by the way how our hearing works).
> 
> Deadening all reflections is not a good thing, as reflections (mainly from 60° left and right) are crucial for spaciousness.
> If one dampens all the reflections, the perceived soundstage will be flat.
> 
> It would be better to build on the Precedence Effect :
> The speakers and the listening position should be positioned where the traveling distance of the first reflections are at least 1.7 metres longer than that of the direct sound (more than 5 ms time difference).
> 
> The reflecting walls then should be treated with diffusors rather than absorbers.


Good info, but doesn't apply to the low frequencies being discussed in a thread about bass traps.


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## Babak

sdurani said:


> Good info, but doesn't apply to the low frequencies being discussed in a thread about bass traps.


The same for post #24.

Also your post could be understood in terms of comb filters:


sdurani said:


> It is reflections from the walls that are causing the cancellation (drop in level) in the middle of the room where you sit. Placing absorption/traps on the walls reduces those reflections, thereby reducing the cancellation at your listening position. To make more efficient use of absorption, you can place the traps where walls meet (corners).


This is a description of comb filters due to reflections canceling out certain frequencies i.e. causing dips. 

Also dips in low frequencies are not heard very well by listeners. Lo 

The main effect of low frequencies in small rooms are standing waves leading to room modes. 
Dips through comb filtering is not such an issue. 

-----------------------

Regarding modes and bass traps... 
The link that I posted (the White Papers from Harman) leads to papers regarding good low frequency performance, including the optimal number and placement of subwoofers.

The paper " Part Three: Getting the Bass Right" 
( http://www.harman.com/EN-US/OurCompany/Innovation/Documents/White Papers/LoudspeakersandRoomsPt3.pdf) 
summarises everything in a very good way. 

How to avoid exciting room modes is an important point. 
You don't need bass traps for room modes that are not excited. 

Cheers 
Babak


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## sdurani

Babak said:


> Also your post could be understood in terms of comb filters:


Not when taken in context (i.e., in a discussion about bass traps, where liteglow was asking about a drop in the 20Hz to 50Hz region). 

I don't want to dissuade you from introducing other concepts (comb filter effects, how our hearing works, spaciousness, perceived soundstage, Precedence Effect, first reflections, diffusors, etc.) into this discussion, but I hope you understand that they aren't related to this particular discussion (using bass traps to address a drop in the 20-50Hz region). 

Like I said, it is good information but is applicable to frequencies outside the bass range.


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## sdurani

Babak said:


> How to avoid exciting room modes is an important point.
> You don't need bass traps for room modes that are not excited.


That's why I asked liteglow if he could move his sub to the location of the null (would prevent that particular room mode from resonating).


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## Babak

sdurani said:


> Not when taken in context (i.e., in a discussion about bass traps, where liteglow was asking about a drop in the 20Hz to 50Hz region).
> 
> I don't want to dissuade you from introducing other concepts (comb filter effects, how our hearing works, spaciousness, perceived soundstage, Precedence Effect, first reflections, diffusors, etc.) into this discussion, but I hope you understand that they aren't related to this particular discussion (using bass traps to address a drop in the 20-50Hz region).
> 
> Like I said, it is good information but is applicable to frequencies outside the bass range.


I appreciate your input. 

Again, the topic of reflections was not introduced by me. I just responded to an earlier post. 

Also taken in the context of low frequencies, your sentence 


sdurani said:


> It is reflections from the walls that are causing the cancellation (drop in level) in the middle of the room where you sit.


describes reflections that cause cancellations leading to a decrease in sound pressure level. 

That's the same thing that leads to comb filtering and something different than standing waves leading to room modes and nulls.

It doesn't matter where the dips in the frequency response come from - comb filter effects, cancellations through reflections, narrow band filters or EQ's. 

Listeners don't hear dips in the frequency response very well - if at all. 
That is the case no matter whether it is in the high or in the low frequency region.

The reason for this lies in the way the hearing works.
Microphones work in a different way, and that's why these dips can be measured but hardly be heard. 

I hope you understand that the topic whether dips can be heard is relevant for this discussion, as liteglow wrote about dips.

However, as long as we don't know how liteglow made his measurements and how the results look like, all of this discussion is only speculation.


Cheers
Babak


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## sdurani

Babak said:


> I hope you understand that the topic whether dips can be heard is relevant for this discussion, as liteglow wrote about dips.


Again, if you want to obfuscate a discussion about low frequencies and bass traps with concepts (comb filter effects, spaciousness, perceived soundstage, Precedence Effect, first reflections, diffusors) that apply to frequencies outside that range, then that's up to you. However, if you could offer something (anything) that could help liteglow with his 10dB dip between 20-50Hz (besides telling him "listeners don't hear dips"), then that would be even better.


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## Babak

sdurani said:


> Again, if you want to obfuscate a discussion about low frequencies and bass traps with concepts (comb filter effects, spaciousness, perceived soundstage, Precedence Effect, first reflections, diffusors) that apply to frequencies outside that range, then that's up to you. However, if you could offer something (anything) that could help liteglow with his 10dB dip between 20-50Hz (besides telling him "listeners don't hear dips"), then that would be even better.


There's no need to get offensive.
Nobody wants to obfuscate anything, so please take it easy.

Maybe I was not clear.

As I wrote before, the topic about reflections was not introduced by me but I only responded to that.
So you should place your complaint about that somewhee else.

Obviously you have overread my other comments to liteglow's bass dip issue.
I also understand that some points appear obfuscating if the connections are not clear.
So I'll try to explain it in another simpler way.

--------------

The first question is, whether the dip is a problem at all-
It would help to see the measurement

There are tolerance limits for variations the room response curve.
Is the dip going below the lower limit of that tolerance range?

--------------

The second question is what causes the dip.
It would be good to know how the measurements were made.

The dip could be a measurement artefact.
Or - if it was a measurement of the room response curve - the dip can be a cancellation between direct and reflected sound.

If it is a cancellation issue it doesn't matter because the ear does not perceive those cancellations that are measured by the microphone.
Ears and microphones work differently and hence response differently to that.

--------------

The third question is whether the dip can be heard at all.

Experiments were made using dips with a certain center frequency, a certain width and a certain amplitude with peaks that have the same parameters.
Listeners perceived the peaks pretty clearly whereas they did only weakly respond to the dips, in many cases they did not perceive them at all.

--------------

So I think that this is an issue that could possibly not be relevant.

It can be a measurement artefact or a dip that is not perceivable (but measurable) or both.


As long as we don't have more details about the measurements, nothing can be added to the discussion.
There is no point in making speculations.

And there is also no point in picking words and starting a dispute about them.


Cheers
Babak


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## Babak

Hi

regarding the question, whether the dip is too big one can refer to the recommendations of the ITU (International Telecommunication Union)

*Recommendation ITU-R .1116-1
Methods for the Subjective Assessment of Small Impairments in Audio Systems Including Mulstichannel Sound Systems*
http://www.itu.int/dms_pubrec/itu-r/rec//R-REC-.1116-1-199710-I!!PDF-E.pdf

Especially interesting for this topic:
*8.3.4.1	Operational room response curve*
It reads as follows:


> The operational room response curves are defined as the *one-third octave frequency responses* of the sound pressure levels produced by each monitor loudspeaker at the reference listening position, using pink noise over the frequency range 50 Hz-16 kHz. The measured operational room response curves shall fall within the tolerance limits given in Fig. 2.
> 
> The differences between the operational room response curves produced by each of the (stereo or multichannel) front loudspeakers at the reference listening point should not exceed the value of 2 dB within the whole frequency range.


This is why I asked about details, how the measurement was made.
Was it measured with pink noise?
Was is measured in one-third octave bands?
How does it compare with the tolerance limits for operational room response curve on page 13?

It would also be helpful to see the RT60 measurements of the room


Cheers
Babak


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## sdurani

Babak said:


> As I wrote before, the topic about reflections was not introduced by me but I only responded to that.


Are you able to separate low frequency reflections in the modal range vs reflections above the transition frequency that result in comb filtering, spaciousness, perceived soundstage, precedence effect, first reflections, diffusors? I only ask because the post you responded to was about the former but the information you posted is about the latter, giving the impression you can't separate the two concepts.


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## Babak

Sanjay,



sdurani said:


> Are you able to separate low frequency reflections in the modal range vs reflections above the transition frequency that result in comb filtering, spaciousness, perceived soundstage, precedence effect, first reflections, diffusors? I only ask because the post you responded to was about the former but the information you posted is about the latter, giving the impression you can't separate the two concepts.


I don't have clue why you try to provoke me by using this offensive style.

In my point of view there is a difference between reflections that lead to cancellations (comb filtering) and room resonances blow the Schroeder Frequency causing standing waves that lead to exaggerated response and booming bass at certain frequencies (modes).

So if you really want to go down the route to be picky on terms and definitions:
When looking at low frequency standing waves (room modes) we are talking about *resonances* and *not* about *reflections*.

What is written here about reduction of sound pressure due to reflections has nothing to do with resonances/standing waves/room modes but is a comb filter effect taking place also at other frequencies.

In my understanding those are the two concepts that need to be seperated but are mixed up here.

--------------------
Regarding spaciousness, reflections precedence effect etc.:

My answer in post #29 was a reply to the posts #24.

Post #24 stated


rkeman said:


> A typical room has many areas of *cancellation and reinforcement that vary by frequency.*


That's describing comb filtering, similar to other posts that deal with reflections that cause cancellations.



rkeman said:


> The best compromise is finding listening and loudspeaker locations that yield the least variation and yet provide *good imaging*.


Good imaging is dependent on reflections and includes spaciousness. Precedence Effect plays a major role here.



rkeman said:


> Try moving the seat closer to the rear wall [...]


This would increas early reflections, probably also those earlier than 5 ms. That reduces imaging, soundstage. The Precedence Effect plays a major role here as well.
So I would reccomend not to move the seat too close to any wall.

-------------------

My other posts #31, #34, #36 and #37 did not deal with those topics at all.
Can it be that you did not read them because you are still stickig to my post #29?

-------------------

Room acoustics deals with a whole bunch of topics at the same time.
One cannot really look at optimal positioning of the loudspeakers and the seat in regards to room modes without looking at the consequences in regards to the wall reflections at the same time.
The optimization of one parameter can lead to a worse situation with a different parameter.

Maybe that is also one thing that seems to obfuscate things.
One simply cannot look at one parameter in isolation.

------------------

So, again my three main points from those posts:

It would be interesting to see the data and the graph from the measurement.
Then we could see what the observed dip really looks like and wheather it is beyond the tolerance levels.

It would also be good to know how the measurements were conducted.
Maybe the dip is more a measurement artefact.

The human ear does not really perceive dips very well. Often it does not perceive them at all.
It is more sensitive to peaks.
So maybe the observed dip is just a detail that only looks ugly in a measurement but is not relevant for the listening experience.

Cheers
Babak


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## sdurani

Babak said:


> In my point of view there is a difference between reflections that lead to cancellations (comb filtering) and room resonances blow the Schroeder Frequency causing standing waves that lead to exaggerated response and booming bass at certain frequencies (modes).


In that case, you understand that you replied to my post discussing how bass traps could help a room resonance below Schroeder by posting a reply about comb filtering, spaciousness, perceived soundstage, precedence effect, first reflections and diffusors, all of which are discussed in the context of frequencies above Schroeder.


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## Andre

wow I actually got a confusion headache reading all this :sweat: AND I had to look up "obfuscate":dontknow:

As for the original question of base trap placement, to be honest because you have an opening on one side and in the middle back I would say you would have to experiment, perhaps putting all 4 in the front on top of each other to the ceiling will sound better, perhaps none at all.

Play around with them, have a movie marathon where you change them around during a few intermissions, have a few friends over and get opinions.

Take some time and have some fun, its not work its a hobbie:bigsmile:


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## Babak

sdurani said:


> In that case, you understand that you replied to my post discussing how bass traps could help a room resonance below Schroeder by posting a reply about comb filtering, spaciousness, perceived soundstage, precedence effect, first reflections and diffusors, all of which are discussed in the context of frequencies above Schroeder.


No, you are putting that wrong.
I replied to post #24 by *rkeman*, especially beause he mentioned moving the seat closer to the wall.
Maybe that could help with the room modes and the low frequency response, but it would make other acoustic parameters worse.

I am sure you understand that.

------------------

I don't know what funny little game you want to play by sticking to this one post of mine and ignoring all others.
Please don't play the "ho-wrote-what-and-where-can-I-prove-him-wrong" game.

------------------

I'm afraid, the concepts of interference and resonance got mixed up here.

In post #28 you stated the following:


> It is *reflections* from the walls that are causing the *cancellation* (drop in level) in the middle of the room where you sit.


What you described here ist not room *resonances* but sound *interference* (between direct sound and reflected sound).
Interference is causing cancellations (rkeman also mentioned reinforcement) and is the cause for comb filtering.

You mention *interference* (reflections and cancellations) again:


> Placing absorption/traps on the walls reduces those reflections, thereby reducing the cancellation at your listening position.


Interferences don't play a significant role below the Schroeder frequency.
Below that frequency room acoustics are dominated by resonances i.e. standing waves.

So there is a mix-up between the concepts of *interference* and *resonance*.

------------------

Both interference and resonance happen at all frequencies, below and above the Schroeder frequency.
Below the Schroeder Frequency resonances dominate the acoustic behaviour of the room and interference is negligible.

No matter at which frequency - humans do not perceive dips in the frequency response very well.
Be it interferences and cancellations between direct and reflected or filters or EQs.

Above the Schroeder Frequency the acoustic of the room behaves in a more stochastic manner.
There it makes sense to work with stochastic measurements like RT60.

------------------

Regarding the *Placement of the traps* (the original question):

Your suggestion where to place the bass traps is not very concrete:


> To make more efficient use of absorption, you can place the traps where walls meet (corners).


What kind of bass traps did you think about?
Porous absorbers or resonators?

Dan put it right.
With room resonances, sound pressure is at a maximum at the walls (sound velocity is at a minimum).

Walls an corners the wrong place for porous absorbers, as that type ob absorbers works most effectively at points with high sound velocity (= low soung pressure - the nulls of the room modes).

The corners would be the right position for other types of bass traps (e.g. Helmholtz-Resonators or plate resonators)

I'll assume that you were thinking of resonators and not of (porous) absorbers ...

------------------

And again.

We don't know, what the "dip" looks like and how it was measured.

So what are you arguing about?

Cheers
Babak


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## sdurani

Babak said:


> I replied to post #24 by *rkeman*, especially beause he mentioned moving the seat closer to the wall.


You replied to post #28 by me, which can be seen quoted in your reply (post # 29).


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## HDMan

Is 100mm thick enough for bass traps?


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## Babak

You're right, my mistake. 

First rekman wrote about reflections then you also wrote about reflections, cancellations and using absorbers against the reflections.

Point given. 

Nevertheless the other points are still valid.

Are there any factual topics or do you prefer to write about me and what I wrote wrong? 

Cheers
Babak


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## ajinfla

Babak, I'm ecstatic to see someone here paying attention.:T
You're right on the money.
Perhaps Sanjay can explain how a 4" thick pillow surgically "traps" 20-50+ foot wavelengths, much less having no effect on spatial perception and timbre? I don't see how that's possible. So your info is completely relevant.
Anyone here have measured effects of 4" pillows vs 20-50' waves? From a physics standpoint, I'd be fascinated to see the results.
And yes, it's much more difficult (if not impossible) to perceive dips (cancellations) of pressure if the Q is high. Despite what your eyes "see" your omni mic measuring as pressure.

cheers


----------



## ajinfla

HDMan said:


> Is 100mm thick enough for bass traps?


You mean absorbers? For what frequency range? What material?


----------



## Babak

I recommend products by *Vicoustic*.

One can use the *Wave Wood* panels over the room corners. They then work down to about 100 to 125 Hz.

Then there are the *Super Bass Extreme* elements for getren frequencies below that. 

And there are the *Vari Bass Pro* elements that can be tuned to specific frequencies to address room modes.


----------



## ajinfla

liteglow said:


> You see this is where my problem begins...
> 
> I have with a great help from 1 of my friend, moved my 71kg heavy sub around the room in all possible locations.
> Even in the middle of the room did we test the sub.
> We did measure the difference each place with my DB tool to check the variations, usually 20 and 50 hz.
> At every location we tried the sub, we did also adjust the phase direction in the subwoofer EQ settings.
> 
> The end result was that no matter where we did place the sub, there was always a -10 db drop on the center of the room, and in the corner\front\rear the sound was optimized ! (as we also would suspect in many years of HiFi)
> 
> So you tell me to sit somewhere else in the room?
> I have a 110" screen in the front, the 1,5 meters on the rooms backside is where I have a work desk (this was a deal for the Lady in the house), and I have moved the couch as long forward as possible to not be uncomfortable on the screen.
> 
> So as you see, there is no room for moving the couch anywhere in the room :dontknow:
> 
> I see only 1 radical solution !!
> And that is to set up a small tiny wall behind the couch to make the room even smaller, but then I will be sitting all the way back in the room, making sound better where I sit !
> When I hang up a cover (moldon?) behind the couch the DB meter indicate some higher values.


Hi Liteglow, I'm a bit confused here. Your sofa is in middle of room. You moved the sub to the "middle"i.e., nearfield...and still had cancellation at the LP?


----------



## ajinfla

Babak said:


> I recommend products by *Vicoustic*.
> 
> One can use the *Wave Wood* panels over the room corners. They then work down to about 100 to 125 Hz.
> 
> Then there are the *Super Bass Extreme* elements for getren frequencies below that.
> 
> And there are the *Vari Bass Pro* elements that can be tuned to specific frequencies to address room modes.


What about nearfield placement or adding a 2nd or 3rd sub to spatially average out the dips and eq'ing down any peaks?


----------



## sdurani

ajinfla said:


> Perhaps Sanjay can explain how a 4" thick pillow surgically "traps" 20-50+ foot wavelengths, much less having no effect on spatial perception and timbre? I don't see how that's possible.


Where did I tell liteglow to use 4" thick pillows for his dip between 20-50 Hz? I explained why bass traps are placed at boundries (or where boundries meet). For his low frequency dip, I asked if he could move his sub.


----------



## ajinfla

sdurani said:


> Where did I tell liteglow to use 4" thick pillows for his dip between 20-50 Hz? I explained why bass traps are placed at boundries (or where boundries meet). For his low frequency dip, I asked if he could move his sub.


 Hi Sanjay, well here, you may not specifically mention "4inch ", but you say:



sdurani said:


> liteglow said:
> 
> 
> 
> But why make a smooth bass on the corners when I only listen i the middle og room.
> 
> 
> 
> It is reflections from the walls that are causing the cancellation (drop in level) in the middle of the room where you sit. Placing absorption/traps on the walls reduces those reflections, thereby reducing the cancellation at your listening position. To make more efficient use of absorption, you can place the traps where walls meet (corners).
> 
> Also, is it possible to move your subwoofer to the middle of the room where the dip is occuring?
Click to expand...

So what thickness "bass traps" does he need to place on his walls to mitigate the LP 20-50hz dip? And where on which walls exactly?


----------



## brwsaw

DanTheMan said:


> Everything makes a difference. In general, you want to absorb the whole front wall with something thick like 4" thick or so. Bass trapping the front corners with broadband absorption like John has. The next absorption point would be your first ipsilateral reflection and then the middle of the rear wall. Some people will also recommend absorbing the first reflection from the ceiling.
> 
> Dan


Sorry to hijack a thread but its related...
I can't place a trap or panel centred on the rear wall but I can place it +/-30" from the rear wall. Would this be worth the effort and cost?

Edit, I missed that there are 55 posts thus far in this tread, just checked the new post section and I ended up on page 1. The question relates to post #9.


----------



## sdurani

ajinfla said:


> Hi Sanjay, well here, you may not specifically mention "4inch "


They why start a post with _"Perhaps Sanjay can explain how a 4" thick pillow surgically "traps" 20-50+ foot wavelengths"_?


ajinfla said:


> So what thickness "bass traps" does he need to place on his walls to mitigate the LP 20-50hz dip?


Depends on the type of trap used. Membrane traps can be placed on the wall, where pressure is greatest. With fluffy fiberglass, it would take a couple feet thick, which would be better placed in corners.


ajinfla said:


> And where on which walls exactly?


In which room, exactly? Can you post a floor plan and some pics of the walls?


----------



## spytech

JohnJSmith said:


> I got a set of 4 Acoustimac 48x24x4" corner traps, and I'm wondering where to put them. Should they go up near the ceiling or down by the floor or in the middle? Or does it make any difference? I don't want them right on the ground because I don't want my cats mistaking them for scratching posts, but I don't have to put them right up against the ceiling to keep them out of claw range.


If truly bass traps, then best practice is 1st location placement, at the tri-corners near the ceiling and at the tri-corners near the floor. everyone needs bass traps and plenty of them, for proper mode reduction. Bass modes pile up in the corners. Their are some great room mode calculators out there that can graphically indicate the modes in your room based on dimensions and give you relative placement of the traps and the required trapping frequencies.
Ultimately, it would depend on the type of trap construction as to placement. then measure measure measure. 
Bottom line is, no matter where you put them, it will help the room. The question is how many do you have room for, and are you willing to incur the associated cost of treating the room. It is my opinion, that it is one the best investments you can make for your theater or listening room.
JMO.


----------



## Babak

Hi AJ



ajinfla said:


> What about nearfield placement or adding a 2nd or 3rd sub to spatially average out the dips and eq'ing down any peaks?


Do you mean nearfield placement of the subwoofer or nearfield placement of absorbers.

If it is the placement of subwoofers I doubt that simply putting them closer to the listening position helps with room modes.
Because the subs excite the room modes depending their position in the room and not relative to the listening position.

That's why I put thelink to a very good paper on this:


Babak said:


> Regarding modes and bass traps...
> The link that I posted (the White Papers from Harman) leads to papers regarding good low frequency performance, including the optimal number and placement of subwoofers.
> 
> The paper " Part Three: Getting the Bass Right"
> ( http://www.harman.com/EN-US/OurCompany/Innovation/Documents/White Papers/LoudspeakersandRoomsPt3.pdf)
> summarises everything in a very good way.
> 
> How to avoid exciting room modes is an important point.
> You don't need bass traps for room modes that are not excited.


I would recommend putting the subwoofer on a null of a room mode and the listening position on another.

As you proposed, using 2 subwoofers would also help to get a better bass response.
Position: in the middle of the front wall and the rear wall, respectively.

Or try to put them further away from the wall, so you get a position where 2 nulls meet.

Cheers
Babak


----------



## ajinfla

liteglow said:


> Sounds like there is some testing that can be done.
> I think I will start a new thread about my problem, and add pictures of the room including schematic etc..
> as soon I got time...


Good idea. And perhaps answer how the subs and measurement in middle of room was done.




sdurani said:


> Good info, but doesn't apply to the low frequencies being discussed in a thread about bass traps.


Again Sanjay, can you explain how in room "bass traps" can be spatial perception transparent? Thus making babaks concerns not applicable. Thanks.



sdurani said:


> They why start a post with _"Perhaps Sanjay can explain how a 4" thick pillow surgically "traps" 20-50+ foot wavelengths"_?


Because the thread (starting at post #1) is about:


> Bass trap placement - high or low? Does it matter?
> I got a set of 4 Acoustimac 48x24x4" corner traps..


Your quoted response was to niteglow, in this thread, who is asking where to place traps for his 20-50hz dip. Perhaps I misunderstood your response in the context of the thread.



sdurani said:


> Depends on the type of trap used. Membrane traps can be placed on the wall, where pressure is greatest. With fluffy fiberglass, it would take a couple feet thick, which would be better placed in corners.


Ok, you believe is is feasible and perhaps even advisable to remove the peaks around a mid room 20-50hz dip with the right "trap"? Or are other methods not involving traps more prudent?



sdurani said:


> In which room, exactly? Can you post a floor plan and some pics of the walls?


Niteglows room that you are discussing.
I'll be interested in seeing how you do your bass trap analysis based on his pics. 
Always trying to learn here, thanks.

cheers


----------



## ajinfla

Babak said:


> Hi AJ
> Do you mean nearfield placement of the subwoofer or nearfield placement of absorbers.


The sub.



Babak said:


> If it is the placement of subwoofers I doubt that simply putting them closer to the listening position helps with room modes.


I disagree, it will change things significantly. Nearer than 1m should practically eliminate all (sub) modal effects.



Babak said:


> Because the subs excite the room modes depending their position in the room and not relative to the listening position. That's why I put thelink to a very good paper on this:
> I would recommend putting the subwoofer on a null of a room mode and the listening position on another.


I know that paper well . It's specific for "listening area", as in a multi seating HT. I think niteglow is only interested in his seat/sofa.



Babak said:


> As you proposed, using 2 subwoofers would also help to get a better bass response.


Yes.:T
My position is that EQ and multiple subs is a superior LF smoothing solution, for most HT people, than anything related to "traps". Without affecting spatial perception. Or making your room smaller.
YMMV.

cheers


----------



## sdurani

ajinfla said:


> Again Sanjay, can you explain how in room "bass traps" can be spatial perception transparent?


By placing them in locations that contribute the least to spaciousness (corners or front & back walls).


ajinfla said:


> Because the thread (starting at post #1) is about:


But my two replies were to niteglow (starting at post #20), not the OP, so the 4" traps were never part of the discussion I was having with niteglow (I don't even know if he has traps yet). Hence my asking why you were linking me to 4" pillows.


ajinfla said:


> Your quoted response was to niteglow, in this thread, who is asking where to place traps for his 20-50hz dip. Perhaps I misunderstood your response in the context of the thread.


You did. If you read both my replies to niteglow, you'll see that I was explaining how bass traps work. Not once did I ask him to use bass traps, let alone 4" pillows. Instead, I asked if he could move his sub. It's in my posts, none have been edited.


ajinfla said:


> Ok, you believe is is feasible and perhaps even advisable to remove the peaks around a mid room 20-50hz dip with the right "trap"? Or are other methods not involving traps more prudent?


I believe it should first be addressed via subwoofer placement, hence my question to nightglow. If that fails, then do what is possible using traps.


ajinfla said:


> Niteglows room that you are discussing.


In that case, I'll repeat my question: Can you post a floor plan and some pics of the walls?


ajinfla said:


> Always trying to learn here, thanks.


LOL


----------



## ajinfla

sdurani said:


> By placing them in locations that contribute the least to spaciousness (corners or front & back walls).


So now you state they _will_ contribute to/affect spatial reproduction. Then Babaks spatial reproduction aspect posts _were_ indeed relevant.
I agree. Any "trap" (aka huge absorber) that would remotely affect niteglows 20-50hz wavelengths, will certainly affect spatial reproduction. Corner or not.
I'll use the term affect rather than say, "harm", since many like those sighted effects.



sdurani said:


> Not once did I ask him to use bass traps, let alone 4" pillows. Instead, I asked if he could move his sub.


Well, my reading of this:


> It is reflections from the walls that are causing the cancellation (drop in level) in the middle of the room where you sit. Placing absorption/traps on the walls reduces those reflections, thereby reducing the cancellation at your listening position. To make more efficient use of absorption, you can place the traps where walls meet (corners).
> Also, is it possible to move your subwoofer to the middle of the room where the dip is occuring?


Suggested he use traps and _also_ consider moving his sub. 
My suggestion is more subs and less "traps".
We'll have agree to disagree on effective/spending suggestions for 20-50hz issues.



sdurani said:


> I believe it should first be addressed via subwoofer placement, hence my question to nightglow. If that fails, then do what is possible using traps.


As above, agree with the relocation/placement, disagree with the use of traps instead of subs.



sdurani said:


> In that case, I'll repeat my question: Can you post a floor plan and some pics of the walls?


If niteglow sends me one I'll post it for you. I'm fascinated so see where 20-50hz traps are placed in 8 (or more) room corners.
Or are they usually full floor to ceiling height?

cheers


----------



## sdurani

ajinfla said:


> So now you state they _will_ contribute to/affect spatial reproduction.


Depends on the trap. If there is a membrane that reflects mid to high frequencies, then it won't. If the trap is a broadband absorber, then it will. You asked about placement of the latter (traps that affect spaciousness). 

BTW, you can deliberately use bass traps that absorb outside the bass range to prove bass traps affect spaciousness. But that's a tautology: use bass traps that also absorbs mid and high frequencies, then point out that the "bass trap" affected spaciousness by absorbing mid and high frequencies.


ajinfla said:


> Suggested he use traps and _also_ consider moving his sub.


Also was in addition to the explanation.


ajinfla said:


> As above, agree with the relocation/placement, disagree with the use of traps instead of subs.


Where did I say to use traps "instead of" subs? Can you quote that from one of my posts?


ajinfla said:


> If niteglow sends me one I'll post it for you.


So you're completely unfamiliar with the room (open archways, screen location, etc) but have been asking me _"where on which walls exactly"_ I would place bass traps? I hope you understand the reflexive LOL in my previous post.


----------



## ajinfla

sdurani said:


> Depends on the trap. If there is a membrane that reflects mid to high frequencies, then it won't. If the trap is a broadband absorber, then it will. You asked about placement of the latter (traps that affect spaciousness).


Yes, specifically, the surgical 20-50hz traps, now with spatially transparent reflective membrane that niteglow would use. Placed, once you see his room pics, that won't affect spatial reproduction.
I'd be very interested in those. I would guess Babak too.



sdurani said:


> Where did I say to use traps "instead of" subs? Can you quote that from one of my posts?


You didn't mention extra subs as an option. Just traps and also, maybe move his sub as I quoted you above. Is extra subs an option you forgot to mention to niteglow? Are they a viable, possibly cost effective option vs the traps he's considering?



sdurani said:


> So you're completely unfamiliar with the room (open archways, screen location, etc) but have been asking me _"where on which walls exactly"_ I would place bass traps? I hope you understand the reflexive LOL in my previous post.


Yes, I'm unfamiliar with his room, hence my fascination with your suggestions to him about 20-50hz traps and single sub relocation.
Thought nothing of it, I'm never concerned by reflexive LOLs when I banter online. 

Btw, I'm sure you're familiar with the works of Toole, Olive, or Geddes, etc. 
Have you ever corresponded with them directly about so called bass traps you speak of? Just curious.

cheers


----------



## sdurani

ajinfla said:


> Yes, specifically, the surgical 20-50hz traps, now with spatially transparent reflective membrane that niteglow would use.


Where did niteglow say he was going to use "surgical" membrane traps? And why would it need to be surgical when the dip is more than an octave wide?


ajinfla said:


> You didn't mention extra subs as an option.


He never mentioned having more than one sub. So I asked him if he could move the sub he has. You still haven't quoted where I said to use traps "instead of" subs.


ajinfla said:


> Btw, I'm sure you're familiar with the works of Toole, Olive, or Geddes, etc.
> Have you ever corresponded with them directly about so called bass traps you speak of?


Haven't corresponded with them but did get taught by Toole, Olive, Welti and Devantier as part of an ARCOS training class three years ago. When asked about bass trapping, Toole mentioned checking into BBC designs from the '70s that worked into the low bass range (as opposed to Helmholtz resonators, which he said were better suited for mid-bass frequencies). 

Never corresponded with Geddes, though I have read some of his writing (and posts on other forums).


----------



## ajinfla

sdurani said:


> Where did niteglow say he was going to use "surgical" membrane traps? And why would it need to be surgical when the dip is more than an octave wide?


His problem is at 20-50hz. Is your suggestion for traps not for that specific range? If not, why? Why would he want to "trap" or affect areas outside 20-50hz?
Again, in my view, a (or more) additional subs operating at 20-50hz to fill the hole is a superior solution to 20-50hz traps. So my initial suggestions to him would not have involved traps like yours. Simply 2 different views of the same issue.
Btw, just to clarify for readers, I don't sell subs.
May at some point, but not previously, or currently.



sdurani said:


> He never mentioned having more than one sub. So I asked him if he could move the sub he has. You still haven't quoted where I said to use traps "instead of" subs.


Well, what is your position for his issue now that I'm in the thread? Is it that he pursue the 20-50hz traps, post a photo of his room so you can advise where to place them and also, move his sub. Or instead, eschew traps and consider more subs?
I would hope I'm clear on my suggestions to niteglow.



sdurani said:


> Haven't corresponded with them but did get taught by Toole, Olive, Welti and Devantier as part of an ARCOS training class three years ago.


Cool. Was this for strictly for your own knowledge or are you in the industry Sanjay? I've seen your posts previously and you're obviously quite knowledgeable about this stuff, but didn't realize you were possibly a pro.



sdurani said:


> When asked about bass trapping, Toole mentioned checking into BBC designs from the '70s that worked into the low bass range (as opposed to Helmholtz resonators, which he said were better suited for mid-bass frequencies).


Interesting. I'll have to check out the BBC stuff. Any links?
Was Toole referencing living room setups, or...?
Was Olive asked any similar questions? His responses I've seen were a bit different, at least regarding living rooms.



sdurani said:


> Never corresponded with Geddes, though I have read some of his writing (and posts on other forums).


His "traps" are a bit different. You lose even more of the room than anything I suspect you will suggest for corner placement.
His comments about those corner things are a bit more in line with Olives, IMO....but we digress.

cheers


----------



## sdurani

ajinfla said:


> Is your suggestion for traps not for that specific range?


That's up to niteglow. If he asks why use traps and why traps are placed where boundries meet (rather than his seating location), I'll answer. If he says he's got another sub, I'll suggest a location (like I did with his current sub). If he says he's got bass traps, I'll suggest locations for those (based on what his room looks like).


ajinfla said:


> So my initial suggestions to him would not have involved traps like yours.


I didn't suggest he use traps. He asked why traps would be useful, I answered. He asked why they're placed at boundries, I answered. IF he had asked why use another sub, my answer would have been different. But just because I would have explained the usefullness of a second sub, that doesn't mean I would have been telling him to use subs instead of traps. It just means I was answering the question he asked.


ajinfla said:


> Well, what is your position for his issue now that I'm in the thread?


My position is still that I'd like you to quote where I said to use traps "instead of" subs.


ajinfla said:


> Was this for strictly for your own knowledge or are you in the industry Sanjay?


I'm merely a hobbyist.


----------



## Putz

My 4 foot high Bass Traps sit vertically on the floor behind the speakers up against the corner. I have Corner Traps mounted in all 4 ceiling corners. Is this the optimal placement? I dunno, but logistically wise, it was the only place I could put them and it definitely made a difference. If you don't have a dedicated room for your audio setup, you make do as best you can.


----------



## ajinfla

sdurani said:


> That's up to niteglow. If he asks why use traps and why traps are placed where boundries meet (rather than his seating location), I'll answer. If he says he's got another sub, I'll suggest a location (like I did with his current sub). If he says he's got bass traps, I'll suggest locations for those (based on what his room looks like). I didn't suggest he use traps. He asked why traps would be useful, I answered. He asked why they're placed at boundries, I answered. IF he had asked why use another sub, my answer would have been different. But just because I would have explained the usefullness of a second sub, that doesn't mean I would have been telling him to use subs instead of traps. It just means I was answering the question he asked. My position is still that I'd like you to quote where I said to use traps "instead of" subs.


I see. So you'd rather not suggest/recommend subs as a solution for 20-50hz dips...unless specifically asked by the person asking about traps, who may not know of the existence of the extra subs possible solution.
Got it.



sdurani said:


> I'm merely a hobbyist.


10-4

cheers


----------



## ajinfla

Putz said:


> My 4 foot high Bass Traps sit vertically on the floor behind the speakers up against the corner. I have Corner Traps mounted in all 4 ceiling corners. Is this the optimal placement?


"Optimal" for what purpose? What are they "trapping" (besides space) in those corners?



Putz said:


> I dunno, but logistically wise, it was the only place I could put them and it definitely made a difference.


I'm sure they did make a difference. But did they solve the specific set of perceptual issues you had prior to placing them there? Did any others subsequently arise?



Putz said:


> If you don't have a dedicated room for your audio setup, you make do as best you can.


I'd suspect most don't....and yes, always do the best you can.

cheers


----------



## sdurani

ajinfla said:


> So you'd rather not suggest/recommend subs as a solution for 20-50hz dips...unless specifically asked by the person asking about traps, who may not know of the existence of the extra subs possible solution.


Correct, most of the time I will try to answer the question asked and work with what the poster already has. Once in a while I'll suggest something unsolicited: e.g., niteglow never mentioned moving his sub, but I asked anyway. This was for a couple of reasons: it's free (doesn't cost anything to place the sub at a different location) and it's reversable (if it doesn't result in an improvement or makes things worse, he can always move it back). If another poster wants to spend niteglow's money, then I won't question it. Unfortunately, the reverse isn't true. 

BTW, since you mentioned Toole, I'll leave you with a quote from his book that I found reasonable: 

_"To improve the situation, room modes must be attenuated; we must insinuate ourselves into the normal “physics” of the room modes. This can be done passively, using low-frequency absorbers—“bass traps”—and lots may be needed to achieve truly excellent results. Absorbers remove energy, and so more sound must be created to produce the original sound levels. Low-frequency absorption is *always useful* because no matter what else one may do, the problem is lessened."_


----------



## ajinfla

sdurani said:


> Correct, most of the time I will try to answer the question asked and work with what the poster already has.


Which is one sub...and no bass traps. The no bass traps you intend to advise him where to place in his room based on pictures. That will help/solve his 20-50hz hole. And be spatially transparent.



sdurani said:


> e.g., niteglow never mentioned moving his sub
> 
> 
> liteglow said:
> 
> 
> 
> I have with a great help from 1 of my friend, moved my 71kg heavy sub around the room in all possible locations. Even in the middle of the room did we test the sub.
Click to expand...

Actually, he _did_. That's why I asked specifically how he measured the mid room placed sub, from his mid room LP.



sdurani said:


> If another poster wants to spend niteglow's money, then I won't question it. Unfortunately, the reverse isn't true.


Seems to me he's willing to spend money on traps, which you will help him place and not dissuade him.
I advise him to spend the same or less....and buy a sub.



sdurani said:


> BTW, since you mentioned Toole, I'll leave you with a quote from his book that I found reasonable:
> 
> _"To improve the situation, room modes must be attenuated; we must insinuate ourselves into the normal “physics” of the room modes. This can be done passively, using low-frequency absorbers—“bass traps”—and lots may be needed to achieve truly excellent results. Absorbers remove energy, and so more sound must be created to produce the original sound levels. Low-frequency absorption is *always useful* because no matter what else one may do, the problem is lessened."_


Cherry picked without context.
But I suppose we'll see if/when he follows your advice on where to place 20-50hz traps, whether his measurements show them as effective and his ear, their transparency.

cheers


----------



## Gordoj

So, let's see if I can get the posting thing right...

It seems as if the same questions is being asked without a direct answer and that is "where should I place my bass trap" so I will jump in with both feet with a direct answer to that basic question - while most people want to place a "bass trap" in the corner of a room where the "cumulative" effect seems most noticeable or against a boundary when in actuality it is the least effective placement for a trap. The corner has the maximum pressure but low particle velocity therefore corner traps are less effective. The most effective place for placement of a bass trap is when the trap is placed a quarter wave length from the nearest boundary. For 100hz that would mean approximately 1m from the boundary.

So I will duck back in the fox hole now....

Gordo


----------



## ajinfla

Hi Gordo, 
I think discussions like this are healthy, because readers get to see various viewpoints.
Thanks for pitching in...and by all means, stay on the battlefield .


----------



## Gordoj

AJ,
I agree with your ascertain that one of the best ways to deal with small room modes is through multiple subwoofers and proper placement throughout the room. There have been numerous white papers and such written about this topic due to the problem that room modes cause in a small room and the difficulty in absorption due to the size of the wave length and the limitations of room size. And unfortunately, this problem probably causes more impact to the listening environment then others and it is the most difficult to solve.

Gordo


----------



## phazewolf

Bass traps can do one thing a extra sub can't and that is help with the decay times in the bass region. That said I think in the case of this room there maybe something else going on think about it.

If he moved the sub all over the room and still has the same issue at the same frequencies then it could be several issues combining to cause the dip. Not using that line of thought maybe just maybe a trap could help more then a sub.

I am not a pro at this so take what I say with a grain of salt but this issue just screams no quick fix sense I feel it is several issues at once.

My room had a 30db peak at 57hz that could not find a way to fix with moving stuff around. When I started adding traps it helped it a lot but then show other issues that were being masked. The bass traps took care of son of the peak and moving stuff fix a lot of it too. But I ended up with a few large deep nulls that when I remove the traps are not there. 

Have you thought about the mains and how they interact with the sub? Could be the two are causing the null. Phase issues are not fun.


----------



## sdurani

phazewolf said:


> My room had a 30db peak at 57hz...


1130 ÷ 57 = 19.8

Do you have a roughly 20-foot dimension in your room? (length or width)


----------



## phazewolf

Yes I do and the width is 23.8 so from about 52 to 58 or so was a huge peak. Traps and 2 subs both helped a lot. Plus I ended up moving where I sat by 6 inches which made a world of difference too.

There now is a huge dip at if I recall 107hz that was not there before traps. As of now I have no idea where the room is at as I now own a new pair of speakers that are placed different and respond totally different then my old pair.


----------



## sdurani

phazewolf said:


> Yes I do and the width is 23.8


OK, so room is roughly 20 x 24?


phazewolf said:


> There now is a huge dip at if I recall 107hz


Are your L/C/R speakers on the 20' wall or 24' wall?


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## phazewolf

Well this room is the only one I can use. They are on the 24' wall but only half that wall is usable 12x20 is kitchen and the other half is liven room. So basically I sit on one half of the room. The right of me us kitchen and the left wall is a door wall and fireplace.

Now to make it even worse and yes it can be worse the half of the room I am in is not drywalled it has the cheep fake wood paneling that was all the rage in 1970 loosely nailed to the 2x4 studs the kitchen is plaster. Also half the room on the right side of me has kitchen cabinets both top and bottom. Oh the kitchen is over a basement the half I am in is a cement slab. 

Fun times for sure


----------



## sdurani

Tough situation for sure. For the moment it's probably best to do what you did by moving your seating out of the null. Down the road, if you can put one of your speakers at the location of the 107Hz null, you might be able to reduce the mode that is causing it.


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## phazewolf

The null goes away if the speakers are flat against the wall at least with the old ones. The new Legacy focus se who knows what is going on as I have not run REW as of yet.

When I have time I will and slide them around to find the best compromise and then place what bass traps I own back into the room and find the best locations for them. Really I only have 2 floor for ceiling corners but lots of wall to ceiling that I can use. That will allow 3 2x4 traps on the front and rear wall ceiling and I can use the the floor also on the back wall. The left wall also has 8 feet along the ceiling I can use. 

So there is a fairly good amount of area I can use for trapping. Once that is done I can play with sub locations once again.


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## Babak

Hi

before jumping on conclusions too early, I would like to understands, what the "nulls" and "dips are, how they've been measured, where they come from.

Examples


phazewolf said:


> But I ended up with a few large deep nulls that when I remove the traps are not there.


or


phazewolf said:


> The null goes away if the speakers are flat against the wall at least with the old ones. The new Legacy focus se who knows what is going on as I have not run REW as of yet.


What measurement showed the "nulls"?
How was it measured, how does the curve look like?

-------------------

The term "*null*" refers to room modes. They are nulls of the *standing waves* that appear due to *resonances* of the room.
Not the nulls cause problems but the maxima of the standing waves.

At the nulls the standing waves do not cause any increase of sound pressure.
This does not influence the direct sound from the speakers/woofers.
A sound pressure of x from the direct sound plus an additional sound pressure of zero leaves the sound pressure x from the direct sound.

The the maximum points the standing waves cause anin crease of sound pressure at the certain frequency.
This adds to the direct sound pressure.
The sound pressure x from the direct sound plus a sound preyyure of y>0 due to a maximum of the standing wave gives an increase of sound pressure at the frequency of the standing wave.

-------------------

"*Dips*" in measurements can have a different cause.

They appear if one measures the room response curve.
The room response measurement is the combined sound pressure of direct sound and the room response (reflections, reverberant sound).

If you combine/overlay the direct sound with the reflected sound, you will observe an *interference* between those two sounds - depending on the frequency and the phase delay of direct vs. reflected sound (more precise: the wavelength and the difference of travel distance between direct an reflected sound).

Interference leads to peaks for certain frequencies (where the direct and reflected sound are in phase and this add to each other) and dips for other frequencies (where the phases are shiftet by 180°, e.g. the direct sound is at high point the reflected sound is at a low point, resulting in a cancellation, zero sound pressure).

-------------------

A microphone only measures sound pressure changes.
So it does not distinguish between direct and reflected sound - but only the resulting sound pressure.

The ear distinguishes sound patterns also depending on the arrival time and their coherence.
Tu it in a simple way early arriving patterns with high coherence are identified as direct souund, late arriving patterns with low coherence are identified as reverberant sound.

The ear does not use the sound pressure.


So the microphone shows a result that is perceived in a completely different way.

-------------------

Additionally the ear responds differently to peaks and dips in the direct sound.

Experiments were made where the direct sound was manipulated.
One set of manipulations was intriducing peaks at different frequencies.
The other set had dips in the same frequencies.

The result was that listeners responden to peaks much stronger than to dips.
In many cases they did not respjnd to dips at all. Only strong dips could be detected.

So, another question is how relevant the dip is in terms of perception.

-------------------

The tricky thing is the right interpretation of measurements.

So it is inportant to know what has been measured and how it was measured (signals, microhphone setup, length od measurement widwows etc.)

It can be that dips and peaks are measurement artefacts.

-------------------

I would recommend several different measurements, for example:

Room reverberation (RT60 or RT30)
Waterfall diagram

The interpretation of those would be the basis for further thoughts.

Cheers
Babak


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## Gordoj

Not disagreeing with anything being said here - i kinda think that this problem is being over thought a little....

He already stated that the null went away when he placed the old speakers against the wall.... hence he moved the source to change the wavelength location in the small room, hence room mode.......

If when the new speakers are looked at and the problem comes back, location could then be checked and then the crossover points between the subs and the mains (and phase).

Knowing the problem is half the battle.

Gordo


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## ajinfla

phazewolf said:


> Bass traps can do one thing a extra sub can't and that is help with the decay times in the bass region. That said I think in the case of this room there maybe something else going on think about it.


Well, without having to go into a 12 page post, I'll just say no. "Bass traps" are simply absorbers that convert sound energy to heat. Fixing the frequency domain, i.e, making it smoother, will also fix you visual time "problems".
But for "audio" problems in the low bass region, you need no such things. What you can "see" in a measurement and what your 2 ears perceive, are two different things. Too many people approach acoustics "intuitively". That is the wrong approach. Perceptual science/psychoacoustics is far from intuitive.
My advice, worry only about amplitude peaks. Cut them down to avg level. Forget narrow dips. Broad ones, a combination of multiple sources and EQ is perfect for HT.



phazewolf said:


> If he moved the sub all over the room and still has the same issue at the same frequencies then it could be several issues combining to cause the dip. Not using that line of thought maybe just maybe a trap could help more then a sub.


No. Something effective for those frequencies would be enormous and physically change the volume of the room. Plus I consider it foolhardy to throw away energy at those frequencies.
Still curious about how he measured, some of it makes no sense.



phazewolf said:


> My room had a 30db peak at 57hz that could not find a way to fix with moving stuff around. When I started adding traps it helped it a lot but then show other issues that were being masked. The bass traps took care of son of the peak and moving stuff fix a lot of it too. But I ended up with a few large deep nulls that when I remove the traps are not there.


Exactly. "Traps" are big, "dumb" pieces of absorber. They're not smart enough to know exactly what frequencies to surgically remove. Active OTOH, is not...at least in skilled hands.
Why didn't you just EQ the peak? You're not one of those 2ch anti-EQ "purists", are you?

cheers


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## Babak

ajinfla said:


> "Traps" are big, "dumb" pieces of absorber. They're not smart enough to know exactly what frequencies to surgically remove.


That's right.

For narrow band reduction one can use Helmholtzresonators or plate/membrane resonators.

Or use a couple (4-6) of *Vicoustic Vari Bass *modules. They can be tuned to specific frequencies. 
http://www.vicoustic.com/hifi-home-cinema/products/acoustic-treatment/basstrap/panel/470


I can also recommend the following absorbers :

The *Super Bass Extreme *work for broader band absorption from 60 to 100 Hz.
http://www.vicoustic.com/hifi-home-cinema/products/acoustic-treatment/basstrap/panel/473


The *Wave Wood* panels also work as broad band bass traps (125 to 350 Hz) when mounted over the corners, eg between wall and ceiling.
http://www.vicoustic.com/hifi-home-cinema/products/acoustic-treatment/basstrap/panel/626

Cheers 
Babak


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## Gordoj

Babak said:


> Or use a couple (4-6) of *Vicoustic Vari Bass *modules. They can be tuned to specific frequencies.
> http://www.vicoustic.com/hifi-home-cinema/products/acoustic-treatment/basstrap/panel/470


Babak, have you used this product? And if so how well did it perform?

Gordo


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## phazewolf

For the measurements I used REW with a calibrated mic. I don't have any of the files anymore they were not recovered when the hard drive crashed so I am only going by my memory which is poor a lot of times.

The hole at 107hz was about 35db deep and if I recall went down to 103 and upto 111hz but I can't be sure.

I have no issue using a eq to fix a peak I just prefer moving everything I can first to make things as smooth as I can first.


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## Babak

Hi


Gordoj said:


> Babak, have you used this product? And if so how well did it perform?


In my room the Wave Wood panels mounted over the room corners were sufficient.
The speakers are located on 1/4 of the room length and the room width i.e. on nulls of several and the listening position is in the middle of the room, i.e. on nulls of other modes. 

So room modes are not really a problem in my room.

A friend of mine distributes Vicoustic products in Austria and I could hear the Vari Bass Pro modules
in several different rooms.
They work very well if enough of them are installed. 
4 are sufficient for small rooms, 6 for medium sized rooms and large rooms possibly need 8 of them.

They work best if they are part of a bigger acoustical concept. 
That means

measure the reverberation times of the room (RT30 or RT60)
use the broad band absorbers (Wave Wood over corners and Super Bass Extreme) to reduce the overall reverberation times at low frequencies
measure again to identify increase of bass response due to room modes
install the Vari Bass modules against specific modes. 
It is an iterative process of measuring and improving. 

So in my rooms the measurements after installing the Wave Wood panels showed that there is no real need to do anything about the modes. 

Of course the Vari Bass modules are not magic but only use physics. 
But using them are less effort than calculating, building and tuning Helmholtz resonators by yourself. 
Especially the possibility to tune them easily to every frequency makes them very convenient and flexible.


Cheers 
Babak


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## Babak

Hi 



phazewolf said:


> For the measurements I used REW with a calibrated mic. I don't have any of the files anymore they were not recovered when the hard drive crashed so I am only going by my memory which is poor a lot of times.
> 
> The hole at 107hz was about 35db deep and if I recall went down to 103 and upto 111hz but I can't be sure.


Thanks for the details.
Do you remember which kind of measurement you performed using what kind of signal? 
Do you remember the position of the mic in the room, that means in relation to all room boundaries (floor, ceiling, walls)?

Those distances could give a hint, whether the hole was caused by interference of the direct sound with the sound reelected by one of the boundaries. 

As written before... 
In my opinion one gets a better idea of the room response and room modes by measuring the reverberation times (RT60 or RT30) and a waterfall diagram of the room response curve and it's decay. 

Cheers 
Babak


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## phazewolf

The mic was at ear height 38" from the ground the location is 8' from the rear wall this had the best sounding bass other locations has large drops in bass and you could hear things missing. From the left wall I am 70" 

As I have said the room is split into 2 half's so very limited placement. 

When I get time I will measure more but what I knew of of the room was with my old Polk SDA speakers which needed to be placed with in 6 to 12 inches of the front wall to work correctly. The new speakers are placed completely different.

The sweeps were made with REW as I said and it was a normal sweep I can't really recall the rest of the details anymore.


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## ajinfla

Babak said:


> That's right.
> For narrow band reduction one can use Helmholtzresonators or plate/membrane resonators.
> 
> Or use a couple (4-6) of *Vicoustic Vari Bass *modules. They can be tuned to specific frequencies.
> http://www.vicoustic.com/hifi-home-cinema/products/acoustic-treatment/basstrap/panel/470


Hi Babak,,

Is there any data (3rd party preferably) showing the efficacy of those type products?
What is the cost?
That would be interesting to compare, vs the same cost subwoofers. Subwoofers that would increase output, lower distortion and be actively adjustable...and most likely much smaller and less obtrusive, both physically and spatially.
Of course, with subs, usually at most, only 3-4 would be needed.
I've never quite grasped the concept of going through the trouble of creating energy....only to throw it away. Seems wasteful to me.

cheers


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## phazewolf

How would adding more subs to a room deal with a room that has very slow decay that makes bass muddy? If just adding a few subs to the room was the answer then there would be no need to have traps and yet many of us use them to great effect.

Have you even been in a treated room before?


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## ajinfla

phazewolf said:


> How would adding more subs to a room deal with a room that has very slow decay that makes bass muddy?


It's not just "add subs". It's add subs, apply eq. Fixing the frequency domain, the "mud" goes away.
Can you show me a "trap" that affects time domain and not frequency? You are "fixing" amplitude with absorption, just in a less efficient manner.



phazewolf said:


> If just adding a few subs to the room was the answer...


It is the answer for smooth amplitude (and resulting perception), greater output/headroom, lower distortion and better power efficiency. All actively adjustable, not passively fixed.



phazewolf said:


> ...then there would be no need to have traps and yet many of us use them to great effect.


Well, perhaps those that do have different needs than above. To each their own if the methods gets you where you want to be.



phazewolf said:


> Have you even been in a treated room before?


Many, including the iso-wards studiophile types like to hang out in.

cheers


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## phazewolf

Trust me I run a pair of subs and it helped to smooth out the bass quite a bit but I also found that adding traps helps the room quite a bit. I however did not trap to the point to where the room is dead.


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## ajinfla

phazewolf said:


> Trust me I run a pair of subs and it helped to smooth out the bass quite a bit


Two are insufficient for spatially averaged smoothing. Three would be a minimum.



phazewolf said:


> but I also found that adding traps helps the room quite a bit.


In terms of amplitude? Any EQ? Does that mean you didn't try more than 2 subs? What was the cost of the traps? How big are they?



phazewolf said:


> I however did not trap to the point to where the room is dead.


Well, your perception and preferences are what matter most here. It may not be "dead" to you, but I doubt they had no effect on spatial reproduction and spaciousness. That's why I ask people what they hear...and what they prefer.
I know fully well that 99% do not attend symphony's/live acoustic music and may judge by unknown to me references. Their local movie theater? A high end stereo shop? Who knows?
So I ask.

cheers


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## phazewolf

Let me put it this way. The room is a audio nightmare, it sounded like a ecco chamber. You could clap your hand and hear the sound bounce around the room.

The floor is a slab of concrete and there is no carpet on it so it reflects everything more of less. The one wall is concrete with fake wood panel on it for show the kitchen wall is plaster and the other walls are wood studs which sit in front of brick outer wall and on the studs there is loosely tacked on 1/8 inch 1970's fake wood panel.

The couch is leather so that does not soak up much and there is a nice door wall that messes up things as well.

As for the panels I have they were grabbed used off of Craig's list for $150 and I got 5 GIK 244 and 1 GIK 242 for that amount so not bad.


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## Babak

ajinfla said:


> Hi Babak,,
> 
> Is there any data (3rd party preferably) showing the efficacy of those type products?
> What is the cost?
> That would be interesting to compare, vs the same cost subwoofers. Subwoofers that would increase output, lower distortion and be actively adjustable...and most likely much smaller and less obtrusive, both physically and spatially.
> Of course, with subs, usually at most, only 3-4 would be needed.
> I've never quite grasped the concept of going through the trouble of creating energy....only to throw it away. Seems wasteful to me.


Sorry, I don't have any 3rd party measurements. 

The costs are about 200 Euros reach, if I remember right. 

I also don't like the idea to create energy to throw it away. 

That's why I adopted Toole's idea not to excite room modes in the first place by placing the subs on nulls of room modes. 
And also to reduce the effect of the modes by placing the listening position on nulls of other modes. 

His following steps are 
- Add bass absorbers, then 
- narrow band EQ to reduce frequencies of remaining modes 


I don't need to absorb modes that are not being excited and that don't build up sound pressure on the listening position. 

There are also other reasons why I would always prefer full range speakers on the right positions (in regards to the modes) to subs that are separated from the sprakers by 1 or 2 meters. One single sub is also a bad solution from my point of view. 


Cheers 
Babak


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## phazewolf

Name a full range speaker that can do want sub can do in a room when placed where it will image and have good overall balance to the sound that can play down to 20hz or less when also placed on the nulls of a given room and cost under 10k

The best place for the speakers to image may not be on a room null and how often is the best most even location for bass in that spot?

And when I am talking full range I mean tested to be flat to 20hz or less without room gain being added in and not can play down to stuff that some company say but by time it is at 20hz it is down 25db


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## lcaillo

Maybe, maybe not. Personally, I don't need to get down to 20 Hz for audio only purposes. Not sure if I need it for HT. Some speakers have plenty of extension to satisfy me in their optimum placement for imaging. Most of the speakers in the last review session we did were fine without a sub IMO. You might want more extension, and a sub is needed for that, but not everyone does.


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## phazewolf

But there is a difference between a speaker and good sub and how deep it can dig. A good speaker can did deep for music we both know that but with home theater the lfe channel can have effects down to 5hz I don't think I want my mains trying to deal with such things.

My friend tried to run a book shelf speaker set to full range with no sub. Played fine at reference volume until a nice loud bomb went off in the movie and popped a driver.


----------



## lcaillo

No one is denying that there is a difference in what subs can do and what most speakers can do. The point is that many full range speakers CAN be satisfying to many people. The amount of actual signal below 30 hz is minimal actually, and not of great importance to most people.

Don't confuse your own priorities with those of others. They may not have any connection.


----------



## phazewolf

What I am saying is with no sub all of it is sent to your mains and that may not be the best idea even a small sub can be helpful. 

Not everyone want the low frequency information but they should also be shown what they are missing by giving up it too. I am still unsure if the lfe channel is redirected to the mains or not when there is no sub. Some say yes some no I would need to use a scope and take a look at what is going on I guess.


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## lcaillo

I don't disagree. I am just saying that for many, if not most people it probably is meaningless. I have done thousands of demos and installed and calibrated hundreds of systems. Most people just don't care. Even among those that care a lot about sound quality, for many purposes they don't need a sub. With my Arx A5 I am just on the edge with music of needing more extension. I don't use them for HT at this time. In my HT I certainly do want a sub, but I don't need much below 30 Hz, certainly not below 20 Hz, to be satisfied.


----------



## phazewolf

When I setup my system I did not think it would hit to where it did. With the old setup before changing my mains I was flat to 17hz

Now I have no idea as I have not measured but the subs in there new location and with better mains it may drop lower I am not sure. It by sound and feel is dipping lower then before but who knows until I can check.

I am thinking about running the subs on the Legacy on the sub input off the avr and using that for one setup for one pair of subs and the twin 18 set on the other sub channel not sure how well that would work.


----------



## Babak

Hi



phazewolf said:


> Name a full range speaker that can do want sub can do in a room when placed where it will image and have good overall balance to the sound that can play down to 20hz or less when also placed on the nulls of a given room and cost under 10k
> 
> The best place for the speakers to image may not be on a room null and how often is the best most even location for bass in that spot?
> 
> And when I am talking full range I mean tested to be flat to 20hz or less without room gain being added in and not can play down to stuff that some company say but by time it is at 20hz it is down 25db


20 Hz or less, flat?
Where does the specification come from?

The frequency range of musical instruments very rarely reaches down to 20 Hz or even below.

You will know the frequency charts like this one from gearslutz.com:








They have left out the lowest tone of the pipe organ, the subcontra c at about 16 Hz (in German it's called the humbleness pipe).
Only some pieces use that pipe, for example Richard Strauss' "Also Sprach Zarathustra".

Also room responses of concert halls don't include frequencies that low.
The famous Golden Hall of the Vienna Musikverein (if you are watching the New Year's concert of the Vienna Philharmonic Orchestra, you will know it) has a well known mode at 21 Hz. But you don't hear that as strong as a room mode in a home theater.

------------

If you read the papers by Floyd Toole and Sean Olive on loudspeaker evaluation, you might know that they also determined how listeners rated the bass response of loudspeakers.

The found out that there was no real correlation between listener preference and the "flat" bass extension (the usual -3 dB limit).

But they found a correlation of listener preference with the -10 dB point. The lower that was, the better were the ratings.

That means tha speakers don't really need a deep flat bass responde (@ -3dB), but a flat roll-off in order to reach a deep -10 dB point.

------------
There are several speakers with those specifications, also at lower prices than 10k U$.

I'm using Shahinian Obelisk peakers, they reach 28 Hz @ -3dB and have bass roll-off of -6dB/octave.

------------

Regarding the placement.

If one is really serious about good sound reproduction, he won't make any coompromises.
So he would first place the speakers (e.g. onto the nulls) and build up his equilateral stereo-triangle from that.

But I'm aware that in most cases one needs to make compromises in regards of the placement.

------------

I think it is also important to note, that only looking at what frequencies can be resproduced at which levels is not really the correct way to estimate how well the result will be for the listener.

The human ear does not work that way.
It analyses the complete sound patterns, i.e. the enevlope curves consisting of a mixture of many frequencies.
One of the important elements of that envelope are onsets. Those consist of different frequencies rising at the same time.

If one places a subwoofer far away of a speaker, the low frequency onsets arrive at different times than the higher frequency onsets.
That diminishes the onset of the envelope cuve.

Even worse, if one uses one sub that is closer to one speaker and further away from the other.
This results in different envelopes from the left and right signal, making the bass "slow".
So, if using one sub, one should place it symmetrically between the two speakers.


Cheers
Babak


----------



## Babak

By the way,

there is a system above U$ 10,000 that goes flat to 7 Hz @ 130 dB.

Listening to that is a really crazy experience ...


----------



## phazewolf

Yes I am aware that our ears can't hear all frequencies evenly and that to have the perspeced of flat the lower the bass freq the louder it needs to be to make one think that it's flat. Which is why a lot of people use a house curve to try and equalize such.

That is also why I like speakers that can play very low because if one ends up boosting the bass at the low octave to build a house curve if that is ones goal not everyone cares then you need to boost it less.

I like pipe organ music to a good low end is something that I want and look for in a speaker. 

Also sense the audio spectrum we can hear is 20hz to 20khz that is what tend call full range. I would not call a car with a governor and a go-cart motor that can only 45mph a sports car and a speaker that rolls off at 40hz I would not call full range. Low frequency responds of a speaker a lot of times not all the time though tend to roll of very fast once you hit the point where they measure the -3db response.


----------



## ajinfla

phazewolf said:


> Let me put it this way. The room is a audio nightmare, it sounded like a ecco chamber. You could clap your hand and hear the sound bounce around the room.
> 
> The floor is a slab of concrete and there is no carpet on it so it reflects everything more of less. The one wall is concrete with fake wood panel on it for show the kitchen wall is plaster and the other walls are wood studs which sit in front of brick outer wall and on the studs there is loosely tacked on 1/8 inch 1970's fake wood panel.


That seems atypical of most living rooms I've been in. Bare concrete floor?



phazewolf said:


> The couch is leather so that does not soak up much and there is a nice door wall that messes up things as well.


Well, actually it does, though it will be slightly more reflective of HF. What about the loveseat, chairs, ottomans, rugs, drapes, media storage, wall art, etc, etc, etc??
Or is this a leather couch in bare concrete floor room?



phazewolf said:


> As for the panels I have they were grabbed used off of Craig's list for $150 and I got 5 GIK 244 and 1 GIK 242 for that amount so not bad.


Not bad, but a $150 PE 3rd sub may have yielded as smooth (or smoother), over a wider area (if important), bass. With more output/headroom and lower distortion.
Of course it wouldn't function as an absorber.

Different strokes for different folks.
I did check out the GIK site and they are _very_ reasonably priced. Must have been on sale when you bought though.

cheers


----------



## ajinfla

Babak said:


> There are also other reasons why I would always prefer full range speakers on the right positions


Yes, I prefer 5 (with 40hz min capability) if you can.

cheers


----------



## Babak

Hi



phazewolf said:


> Yes I am aware that our ears can't hear all frequencies evenly and that to have the perspeced of flat the lower the bass freq the louder it needs to be to make one think that it's flat. Which is why a lot of people use a house curve to try and equalize such.


Obvisously you got me wrong.

I was not talking about the Fletcher-Munson curves or (more correctly) Robinson-Dadson curves which are the reason for people using EQs especially when playing at ow levels.

I was talking about a mecahnism of the human ear that is called "phase locking".

With subs in different locations than the speakers and with asymmetrical setup of one single sub you mess up the phase locking mechanism leading to a loss on precision.




phazewolf said:


> I like pipe organ music to a good low end is something that I want and look for in a speaker.


Not many organs do have a subcontra c pipe with 16 Hz.
And not many pieces of music use that pipe.

And also those frequencies are not present with high intensities.

I'd really like to know how many recordings you have in your collection that use that pipe.



phazewolf said:


> Also sense the audio spectrum we can hear is 20hz to 20khz that is what tend call full range. I would not call a car with a governor and a go-cart motor that can only 45mph a sports car and a speaker that rolls off at 40hz I would not call full range.


based on Floyd Toole's findings it's better to have a -6 dB per octave roll-of at 40 Hz than a -18 dB per octave roll-off at 20 Hz.


Again, the question is if one really needs it.

With driving speeds, the full range would go up to 200 mph or more. There are cars that can go that fast, and on many German Autobahns there are no speed limits, one could go with 300 mph as well if the car can go that fast.

So should people drive sports although they will not drive faster than 150 mph or more in 99,9% of their trips (even when living in Germany there are not too many opportunities to drive that fast due to the traffic)?

The same with music an low frequencies.
How many recordings does somebody listen to, that have frequencies of 20 Hz or less at high levels and where it would ruin the perceiption of the work if those frequencies are delivered at 3 or 6 dB less than it should be?

You can make some spectrum analysis from tracks to see how much there is at 20 Hz or belowm
You can also put a steep high pass filter at 20 Hz and listen to the track again to see, what the difference is.

Both can be shared in the forum.




phazewolf said:


> Low frequency responds of a speaker a lot of times not all the time though tend to roll of very fast once you hit the point where they measure the -3db response.


That's one should look at the frequency response measurements of the speakers to see where the -10 dB point is.

And still there is the question:
How often is it neccessary to play frequencies below 30 Hz at high levels?

I think that's not very often.

Cheers
Babak


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## phazewolf

J am currently at work so I can't really get into everything but I use the system for both music and home theater which is why I like the ability to dig very deep.

As for a sub that would sound good and match well what I have for $150 that spent on trap I am not sure I could find one.

The traps I got were used but in good shape.

As.for phasing the subs the auto cal my Onkyo has sets the delay for each speaker and both subs independently and I can tweak it with the calibrated mic I have using REW.


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