# Gap in my response



## subby (Aug 17, 2007)

Hi

I just moved into a new house and my HT room is way bigger now then my previous. I have the SVS PB10. After weeks of work in the new hous I finally got some time to calibrate my sub yesterday. Unfortionatly I got a very weird measure result.

 
 


As you can see the graph peaks at 20Hz and at 25Hz it just drops down and comes back up only about 50Hz. I tried moving it around a bit in the front from left to right but it doesn't change much. for now the sub was only positioned in the front corner of the room. Maybe I have to try to position it behind or a couple of meters aside the listening position. The problem might be that my room is not only much bigger (8m x 5m), but as you the ceiling also goes downwards at the sides like a roof of house (see pic 3, it's a view from the side) and there are 4 windows so there is kinde of a niche on each window (see pic 3). Maybe the frequenties above 25Hz get lost in the window niche right next to the sub? 

Do you have any tips where I can try to position my sub?
And is it a good idea to boost the gap of frequenties or will it stress the PB10 too much?

sorry for my poor english but it's not easy to explain. :scratchhead:


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## brucek (Apr 11, 2006)

*Re: gap in my graph*



> Do you have any tips


You're using a rather exaggerated vertical scale in your graph that make the situation look worse than it is.

Post your graphs in the standard we normally use here at HTS.

Vertical scale = 45dB-105dB.
Horizontal scale = 15Hz-200Hz.
Be sure to show the target at the crossover frequency you are using.

brucek


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## subby (Aug 17, 2007)

*Re: gap in my graph*

ok, I'll try to do another measure next weekend because I'm only home in the weekends.


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## JBravo (Jun 20, 2007)

*Re: gap in my graph*



subby said:


> ok, I'll try to do another measure next weekend because I'm only home in the weekends.


you shouldn't need to remeasure unless you didn't save your measurements. You can just reload them and change the graph settings, then re-save your graph and repost here.


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## subby (Aug 17, 2007)

*Re: gap in my graph*

I left my graph at home. I only took the JPG with me. I'll change the settings over the weekend.

cu then


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## Wayne A. Pflughaupt (Apr 13, 2006)

*Re: gap in my graph*


In the meantime:



> And is it a good idea to boost the gap of frequenties or will it stress the PB10 too much?


You really can't stress that subwoofer because it has a built-in limiter. Boosting will reduce the amount of headroom you have, which means you won't be able to get as much SPL as you would otherwise. But let's wait and see what your new graphs looks like...

Regards,
Wayne


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## subby (Aug 17, 2007)

*Re: gap in my graph*

Ok, did another measure today.

 
 

I found a picture of my room before we moved into the house. In the right corner where the sofa is located, behind the soccergame table, that's where my sub is now located. Just to give you an idea how my room is shaped. So I did a new measure of the same graph from last week and did the settings as you asked, but not much changed.

 

then I moved the sub to the window corner right next to the hall (see top shot scetch of my room at the top of this page). Out of this measurement came this graph. The gap is much less But I lose out a few frequenties at the bottom end.

So look like I have to choose. keep the sub's current location and have the 20Hz but with a gap after 25z, or have balanced line but lose the bottom end frequenties. Maybe I've come to the limits of the pb10 and my room is too big for this decent but entrie model. Either way, I was hoping to upgrade to the pc13 if my poor student budget allows it somewhere in April or so.


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## brucek (Apr 11, 2006)

*Re: gap in my graph*

I'd keep the current location with the extended bottom end....

The dip (gap?) will not be as noticeable as a loss of bottom end... 

brucek


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## JBravo (Jun 20, 2007)

*Re: gap in my graph*

that original with your dip doesn't look that bad. If you have an eq, you could cap some of those peaks and smooth things out a little bit. But that sub looks like it is handling the room fine.

I would read up on adding a house curve next.


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## subby (Aug 17, 2007)

*Re: gap in my graph*



Buknakyd said:


> that original with your dip doesn't look that bad. If you have an eq, you could cap some of those peaks and smooth things out a little bit. But that sub looks like it is handling the room fine.
> 
> I would read up on adding a house curve next.


Where would you change the peaks?

I've heard of a house curve before, but don't have a clue of what it is or how to do it.


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## JBravo (Jun 20, 2007)

*Re: gap in my graph*

here are the links to Wayne's articles on house curves:

House Curve: What it is, why you need it, how to do it. 

Minimal EQ, Target Levels, Hard-Knee House Curves.


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## brucek (Apr 11, 2006)

*Re: gap in my graph*



> Where would you change the peaks?


Simply lower them with a BFD. REW will recommend the filters to use..

brucek


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## subby (Aug 17, 2007)

*Re: gap in my graph*



brucek said:


> Simply lower them with a BFD. REW will recommend the filters to use..
> 
> brucek


I already tried, but it always says: "there are no peaks to be equalised" or something like that. I must admit that I haven't worked with REW for over a year so I probebly overlooked some steps. unfortionatly I also have very few time left these days as school projects are requiring more and more time as the hollidays near.


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## Wayne A. Pflughaupt (Apr 13, 2006)

*Re: gap in my graph*




> I already tried, but it always says: "there are no peaks to be equalised" or something like that.


That's because REW looks for peaks in relation to the Target Curve. Your first graph had the signal so low that it was all below the Target:












Your new graph has the levels up where they should be, and as you can see the peaks are now above the Target Curve. REW will recommend filters this time.












Regards,
Wayne


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## subby (Aug 17, 2007)

*Re: gap in my graph*

I just tried the "assign filter" button and it still says "there are no peaks to be corrected".


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## brucek (Apr 11, 2006)

*Re: gap in my graph*

Hopefully, you pressed FIND PEAKS first?

brucek


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## subby (Aug 17, 2007)

*Re: gap in my graph*

Ok thanks, I set the filters. I only should do another measure to see if the result of the filters are really as good as REW predicts. 

I don't want to seem lazy. But can you tell me in short what a house curve does and how I can do it? I really have very little time on my hands these days and I don't want to get it all to technical.


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## tenzip (May 4, 2007)

*Re: gap in my graph*

The short, very simplified version of "Why do I need a house curve?" is:

The human ear is less sensitive to lower frequencies, so you need to reproduce them louder to make them seem as loud as the higher frequencies.

The even shorter version is:

It will sound better.

As for how, and a more detailed explanation, read the links that Buk gave in post #11 above.


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## DrWho (Sep 27, 2006)

*Re: gap in my graph*



brucek said:


> You're using a rather exaggerated vertical scale in your graph that make the situation look worse than it is.


Can you please explain how changing the vertical scale changes the data in the measurement?

Subby, what mic are you using for your measurement? Also, can you post some waterfall plots? Behavior like you're seeing is very typical of room modes - the most reliable band-aid will be moving your listening position and subwoofer.


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## DrWho (Sep 27, 2006)

*Re: gap in my graph*



tenzip said:


> The short, very simplified version of "Why do I need a house curve?" is:
> 
> The human ear is less sensitive to lower frequencies, so you need to reproduce them louder to make them seem as loud as the higher frequencies.
> 
> ...


I would argue that the non-linearity of human hearing is compensated for during the recording process...even in the most simplistic of recording techniques, you're still choosing the mic location with your ears.

I'm not saying that flat response after room gain is the ideal, but I do find that a "house curve" following the Fletcher Munson curves is going to be way way overexagerated. I think the ideal lies somewhere with the effects of the group delay from room gain...


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## brucek (Apr 11, 2006)

*Re: gap in my graph*



brucek said:


> You're using a rather exaggerated vertical scale in your graph that make the situation look worse than it is.





DrWho said:


> Can you please explain how changing the vertical scale changes the data in the measurement?


It doesn't, those are your words. Re-read the sentence. 

Graph scaling is a major cause of data misinterpretation, and is often used in many fields (and particularly advertising) as a tool to exaggerate or support an argument that the data alone doesn't.

A great many new members have little or no experience with graphs and require instruction on interpretation in a language they understand.
To that end we have decided to use a standard scale set for all REW graphs (unless someone wants to specifically point out a section of data). 

The scale we chose is quite appropriate for the audio data it represents and has been chosen as the default in REW software. This allows everyone to represent their data in a way for easy comparison without confusion. You need to be aware that not everyone is as experienced as you obviously are in interpreting graphs.

Even with this policy, I have many examples where new members have posted inappropriate scaling for their graphs, and as a result have received incorrect advice from rather seasoned members who misinterpreted the graphs.

As an example, here are three graphs using the exact same REW mdat file, with difference scaling chosen. I have seen all these scales used here at HTS. I suspect that someone who is new to interpreting graph data might think the data is derived from different measurements.




























Subby, I apologize for hi-jacking your thread. I thought the info might be useful.

brucek


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## tenzip (May 4, 2007)

*Re: gap in my graph*



DrWho said:


> I would argue that the non-linearity of human hearing is compensated for during the recording process...even in the most simplistic of recording techniques, you're still choosing the mic location with your ears.
> 
> I'm not saying that flat response after room gain is the ideal, but I do find that a "house curve" following the Fletcher Munson curves is going to be way way overexagerated. I think the ideal lies somewhere with the effects of the group delay from room gain...


Mike, I'm not going to argue any of your response, but I will say that lots of people seem to be very happy with house curves. I've never seen one that looked like an equal loudness curve or F-M curve.

If you can show us a better way, lead on, man, lead on!


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## DrWho (Sep 27, 2006)

*Re: gap in my graph*



brucek said:


> It doesn't, those are your words. Re-read the sentence.


I'm not saying that a standard for comparison is a bad thing - in fact, it's great for quick comparisons. 

I brought it up because there is an underlying mindset that a "good graph" somehow validates the performance of a system. A perfectly flat frequency response can actually sound quite horrendous...it just means the frequency response is the wrong tool for identifying the problems. So what's the point in comparing against other plots?

Isn't the whole point of measuring to identify and then fix problems? If you're not going to fix anything, then what's the point? Extending from that, proper scaling is pretty much just zooming in on the problem so that it can be identified when it is fixed.

I guess I just don't see the sense in asking for less resolution when the original plot was scaled quite appropriately? What extra information is to be gained? Are you archiving plots or something?


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## DrWho (Sep 27, 2006)

*Re: gap in my graph*



tenzip said:


> Mike, I'm not going to argue any of your response, but I will say that lots of people seem to be very happy with house curves. I've never seen one that looked like an equal loudness curve or F-M curve.
> 
> If you can show us a better way, lead on, man, lead on!


Man, I just keep coming off negative in this thread...

Why try to validate house curves by referencing the F-M curves, when it is quite clear the house curves aren't addressing equal loudness? That was my original point...and I only commented on it because it can lead to future misinformation.

As far as providing a better way, it's way easier to be negative  I believe there was actually a recent article in AES on this subject, but I haven't gotten around to finding it at work (bloody deadlines). I think it will actually end up being source material specific and therefore some compromise will always be required....so then it starts to become purely subjective.


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## tenzip (May 4, 2007)

*Re: gap in my graph*



DrWho said:


> Man, I just keep coming off negative in this thread...


Mmm, maybe 'firmly assertive' would be better. :yes:



> Why try to validate house curves by referencing the F-M curves, when it is quite clear the house curves aren't addressing equal loudness? That was my original point...and I only commented on it because it can lead to future misinformation.


I am no expert, spewing misinformation from time to time is my lot, I fear. Maybe I should have engaged brain before applying fingers to keyboard, and let someone else answer the OP's question. I am willing to learn, and I have no doubt that you've forgotten more of the stuff from your school and work than I have time or energy to learn. That pesky life stuff just keeps 'asserting' itself. :bigsmile:



> As far as providing a better way, it's way easier to be negative  I believe there was actually a recent article in AES on this subject, but I haven't gotten around to finding it at work (bloody deadlines). I think it will actually end up being source material specific and therefore some compromise will always be required....so then it starts to become purely subjective.


And isn't all life? Shoot. I hoped you had a silver bullet.
I recall your information was always very interesting and informative when I read the Klipsch forums, I haven't had time to stop by for quite a while, unfortunately.


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## subby (Aug 17, 2007)

ok, I ordered myself a PC13 after the holidays to replace my PB10. Just did a measure and I got a really weird result. The bass just dropped after 25Hz. The PC13 normally should go below 20Hz. I already tried 15Hz mode but that only gives a slight bass increase at 70db. My listening position is the same as in the painting of my first post above. And the pc13 is located at the window (in the small hole) left of the listening position. I don't have much placement possibilities. If I locate it at the position like in the painting I'll have a lot of bass and vibrating in front of the room but quit some loss in bass at listening position. 
I have the parametric EQ of my pc13 set to OFF.

I can say that the peaks and wholes in the 25 - 35hz frequenties are gone so that's a good thing. But I lose much bass beneath below 25Hz wich is very similar to what happened when I had my PB10. The grapg I have now is quit similar to the ones I posted except for the dip between 25-35hz then. My walls are going up diagonally to the ceiling because I sleep under the roof. Is it possible that the bass concentrates at the lower part of my room? Or is it maybe a wrong setting in REW?


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## subby (Aug 17, 2007)

Ok, I just moved the pc13 to the front of the room as in the original painting was added. Surprisingly I get a better graph although the dib between 25-39hz is now back (that probably the loss in bass I heard from my listening position before. 
 
Any recomodations you have for me to boost or trim down?

I also tried to assign filters but REW said it didn't have any peaks to correct, although I did set the target level to 75db. any advise?

regards
Bert


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## JohnM (Apr 11, 2006)

subby said:


> I also tried to assign filters but REW said it didn't have any peaks to correct, although I did set the target level to 75db. any advise?


Did you use "Find Peaks" before "Assign Filters"?


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## subby (Aug 17, 2007)

woopes, didn't see you could click those words. :nerd:

Just did some new measures and tests. As I pointed out in my previous post I located my sub back in it's original position as you can see in my scetch in my first post. Like I had with the PB10, I also now have a nice boost at 20hz and even 16hz in "15hz mode". But after 25hz the frequenties lose some gain and I stumble upon a gap between 25-40hz. First I tried to increase the frequenties in the gap but my PC13 made a loud popping sound during the subsonic heartbeats at the start of Pirates of the carrebian 2. So that wasn't a good solution.

 
 
as you can see on in the graph REW only sets filters for frequenties above 40hz. But the peak under 25Hz is totally ignored. I don't mind some serious subsonic bass but I also want to hear the frequenties above 25Hz instead of only feeling bass and rattling the whole room and being underwhelmed by all the audible bass. Because most bass in movies is above 25Hz.

I set some filters manually and did a new measure. Then I came upon this:
 
don't know if it will be better now. I still had to increase the 30-40hz a bit but I also decreased the 15-25hz zone a lot so I don't know if the pc13 will still be stressed. I also had to push the sub's volume a bit on my receiver. My sub's gain is set to 9 o'clock if that information helps. So what do you think? Woeld this improve the sound?


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## brucek (Apr 11, 2006)

> Woeld this improve the sound?


You're asking us? How would we know? That is something you have to decide for yourself. Everyone likes their sound different. 

brucek


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## JohnM (Apr 11, 2006)

Also after assigning filters don't forget to click "Optimise PK Gain & Q"


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## subby (Aug 17, 2007)

brucek said:


> You're asking us? How would we know? That is something you have to decide for yourself. Everyone likes their sound different.
> 
> brucek


k, kinda expected this kind of comment. Of course you're right. But I ment what the standards are for most HT users and pro's. I thought it was best to get a flat responce in the end. Is there a possible way to lower the 15Hz peak? I want some subsonic bass but not to overpower all the upper 25hz frquenties wich is most used in movies and music.

I did the "optimise Pk gain & Q" but I din't see much result in my filters.


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## Wayne A. Pflughaupt (Apr 13, 2006)

subby said:


> But after 25hz the frequenties lose some gain and I stumble upon a gap between 25-40hz. First I tried to increase the frequenties in the gap but my PC13 made a loud popping sound during the subsonic heartbeats at the start of Pirates of the carrebian 2. So that wasn't a good solution.
> 
> I still had to increase the 30-40hz a bit but I also decreased the 15-25hz zone a lot so I don't know if the pc13 will still be stressed. I also had to push the sub's volume a bit on my receiver. My sub's gain is set to 9 o'clock if that information helps.


Most likely the sub will still be stressed now if it was before. For the purposes of amplifier headroom, cutting or boosting the EQ is academic, because with cutting you end up increasing the sub's level to make up for the loss in overall SPL - just as you did.



> So what do you think? Woeld this improve the sound?


Well, you dealt with all the ups and downs, which will give an improvement. On the other hand, response is now very flat, which many people think sounds anemic. If you end up with that impression, try a house curve.



subby said:


> k, kinda expected this kind of comment. Of course you're right. But I ment what the standards are for most HT users and pro's. I thought it was best to get a flat responce in the end. Is there a possible way to lower the 15Hz peak? I want some subsonic bass but not to overpower all the upper 25hz frquenties wich is most used in movies and music.


To reduce the 15 Hz peak, you'd need an equalizer that will allow you to set filters that low.

By the way, it won't hurt our feelings if you make your graphs larger. A lot larger.

Regards,
Wayne


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## DrWho (Sep 27, 2006)

The graphs are really small on my screen, but it looks to me like the rise in response below 30Hz is due to room gain....looks to be a rather classical example too.

I did find that article on room gain, but it's copyright so I don't think I can just post it...it was basically talking about algorithms for detecting room gain so that all these new auto EQ products can learn to ignore it....the implication being that psychoacoustic research indicates that you want to leave the room gain alone. I haven't had a chance to read up on all the references yet (and I don't have the article on this computer and can't remember the title).

I don't know how John's peak finder works, but I can't help but wonder if you want to ignore the 25Hz EQ it suggests and then just leave everything else below that point alone. You might also try setting two presets on your EQ device so you can toggle back and forth....I think you'll be surprised by how little of a difference it makes _most_ of the time.

It would also be interesting to see how well your xover to your mains is working. I find that has a much larger impact on the sound.

Btw, how high off the ground was the microphone during the measurements?


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## subby (Aug 17, 2007)

sorry for the pics, I posted them and thought you could click on the so they would get bigger. So you can't click on them or are they still too small when you click on them to get bigger?

I use the SPL radioshack meter and have it set at 75db as is advised in the REW help file. crossover is set to 100hz as is adviced on many forums.

I measured at a low position because my listening position is low to the ground. About 1 meter above the floor.

I'm trying to read through the house curve article but it's not easy as my english and technical knowledge isn't that great. So I'll have to spend some more time on that.


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