# Help interpretation latest room curve.



## eyesandears (Apr 25, 2012)

Hello,
I need some expert opinions and suggestions on the bass response of my 2 channel system.
Here is a screenshot and data file of my most recent REW measurments. This was running the Mains + one sub.
Below is the best (flattest) curve I could obtain after hours of adjusting phase, crossover, and levels. The sub was moved to multiple locations and orientations in the front center as well as right front corner of the room both behind and next to the floor standing speaker. 

I have no equalizer. The mains -6dB point is ~43 Hz. Measurments taken from primary listening position 10.5' from the main speakers. Rear wall 7.5' behind mic. Mains are 2.5' from side walls and 5.5' from front wall.

Sub crossover ended up at ~45 Hz. Phase @ 180. The sub has only 0/180 opt. I dont completely understand how phase works. I find that the optimal phase seems to vary depending on frequency making it impossible to have a single perfect setting. Is that correct?

Nothing I tried had much effect on the large dips at 32 Hz, 90 Hz, and 150 Hz. Are room modes causing these dips?









View attachment Mains + Sub (bass only) Dec 7 16_26_08.mdat


Mains: Dyn C3.3
Sub: REL R-528
Scarlett 8i6
Earthworks M23
Dell Inspiron E1505 Win7 Pro
Room size: 24'L X 15'W X 12'H 

Thanks for any assistance!
Mark:dontknow:


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## robbo266317 (Sep 22, 2008)

What are the dimensions of your room?


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## eyesandears (Apr 25, 2012)

The room is moderate sized and rectangular. 24'L X 15'W X 12'H 
It has a 12" H X 7' D riser in the rear.


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## Phillips (Aug 12, 2011)

Please post mesurements for the mains and sub seperately + both phase.

Have you tried moving the mains a bit?
Listening position as well plays a factor especially if you can't move the mains much.
I have REL subs they prodominently prefer corner loading, but not always.
I have both mine set to 180 and this isn't uncommon with REL subs according to installers.
I found placing them not equal from each wall the right place, use odd numbers e.g. 11 inches x 7 inches. 
I was given this advise by a REL installer and it worked well.


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## eyesandears (Apr 25, 2012)

Phillips, thanks for your response.
I moved the mains around as much as possible to get the flattest curve and best sound but that was before integrating the sub. I don't have much lateral room to move them due to a large projector screen. I dont have much wiggle room on the main listening position. Only about a foot forward/back

The corner placement for the Rel did show significant boost. I only have one sub. Unfortunately due to a large peak between 40 ~ 65 Hz it required moving it out from the corner to smooth out. Worst case for this was when the sub phase was set at 0 deg. (green trace). Crossover adjustments had very little effect and if I lowered the level enough to correct it the curve began to resemble the mains without the sub.

Not sure how you prefer to look at these measurments so I will post both no smoothing and 1/6 smoothing screenshots. I also added a shot of the nearfield sub measurement at the same crossover point for comparison.

Red = sub only
Black = mains only
Green = Mains + sub 0 deg.
Blue = Mains + sub 180 deg (current setting)


Thanks


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## Phillips (Aug 12, 2011)

The reason i wanted to look at these graphs was to try to see which speaker/s was the issue.

Phase generally has effect on the crossover frequency, dips and nulls.

Can you post (with the overlay tab) the impulse response?

With looking at graphs i mainly use 6-24 smoothing.

The dip at 32hz trend seems to be in all the measurements, even the mains at alot lower level obvoiusly.

Ideally the dip is in the subs range.

Have you tried the other side, when i had just the one i tried the other side and the measurement wasn't that great?

Do you have the REL at equal distance from each wall, try what i suggested odd numbers? What are your distance from each wall in inches?

Try different crossovers, mine are set to 25hz and the floorstanders go down to 32hz. As you can see the crossovers aren't a brick wall.

Try measuring at different listening positions, i know you can't move much but worth ago to see if there are any improvements.

It took me sometime to get mine right.

Matter of interest measure each main and post.

You also use the RTA in REW to find the best position then fine tune.


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## eyesandears (Apr 25, 2012)

I havn't used the overlays function yet so I'm not sure what you want. Do you want the impulse response of one sweep or all overlayed?

The RTA I just started playing with but still not quite sure if I am using it correctly.

I have only moved the sub around in the front corner of the room from the wall to to near center.
Currently it is located exactly 39" from the right wall and 55" from the front wall. (measured to the center of the driver). If you saw that much of a difference between the two front corners and you think it will be worth the effort than I will try the left front corner. 
I suspect the ~32 Hz null is being created by an axial room mode. It's pretty close for room width of 15'. Considering both mains and the sub in different locationa all have it I would be very surprised if moving the sub will make a significant difference. I am afraid, also at that low frequency it will be difficult to get enough acoustic treatments to eliminate it. 

I need to sweep both mains again since I lost one of the files but I did notice a slight difference between them. 

I did try every crossover/level combination and this was the best I found in this positon. Initially I set it low at 30 Hz but that required a high level to even notice audibly the sub was doing anything. 

Speaker spec. FR = 32 Hz ~ 20 Khz, +/- 2.5 dB. At the listening position I am getting fall off at 54Hz with -6dB point at 43 Hz.

I will post back tomorrow with some more of the info you wanted.

Thanks again.:wave:


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## Phillips (Aug 12, 2011)

The mains and sub seperately. This will give us an idea of the phase. 
Check the polarity on your speakers. The original (1st post) looks pretty good except the trough at 32hz.

The RTA is a quicker/easier way of finding positions for speakers. Look at the bars and you will see dips/peaks etc in real time as you change crossovers/movement. Which part of the RTA don't you understand?

Your freq of your mains are 32hz which is where the trough is. I think to try and get the speakers good then enter the sub. When i originally set mine up extension wasn't that great only to 23hz, but know 16hz (even with just one) with careful setup. I have Strata 5s (down firing).

Another thought change phase back to 0 and try the crossovers, don't forget to increase the level as the crossover decreases to compensate.

The subs seem to be along way from the corner walls, RELs like corner placement. Mine are 11inches x 7inches from the walls.

When you tried every crossover/level did you change the phase, this is why RTA is good and quicker.

What are your specs of the sub? RELs tend to lock in to the room with little movement.


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## eyesandears (Apr 25, 2012)

Spent a number of hours yesterday trying to optimize the sub and main speaker settings and locations.

The mains seem to be located optimally at this time based on REW as well as listening. Interestingly, I moved them and found a slightly better spot based on the room analysis curve when run without the sub but that location was not as good when run with the sub. I even tried the recommended "Cardas" setup locations and the curves were much worse.

I found that placing the sub too close to the corner preferentially accentuated the peak from 40-60Hz making it difficult to flatten out. I tried both front corners with almost identical results. Although I really can't leave it there I tried one rear corner for curiosity. Their I was able to eliminate the dip at 32 Hz at the expense of multiple other even deeper dip at 50 Hz. So, long story short I ended up back close to the position it started in. I attached my latest curves. 1. IR 2. L, R, both speakers 3. Latest Mains +?- sub results. I am still not please with these curves. I can't seem to improve the dip in the 32Hz range without adding a large peak from 40-60 Hz. Also the dip at 90Hz remains.

You are correct. The resonant frequency of my mains are 32 Hz. I am not sure if that has any bearing on the dip at 32 Hz we are seeing or coincidental. My understanding of speaker design is limited but would't you expect a peak at the resonant frequency?

I also gained some experience using the RTA. Unfortunately, I over the weekend didn't have a long enough USB cable to get my laptop close enought to see it from the location of the sub! :hissyfit:

Here's the REL R-528 specs. Not quite as impressive as your Stentor :T but still respectable.

Passive radiator with 12", 300mm long throw front firing woofer
21Hz @ -6dB
Gain control 80dB
500 W RMS (Class D)


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## Phillips (Aug 12, 2011)

eyesandears said:


> Spent a number of hours yesterday trying to optimize the sub and main speaker settings and locations.
> 
> The mains seem to be located optimally at this time based on REW as well as listening. Interestingly, I moved them and found a slightly better spot based on the room analysis curve when run without the sub but that location was not as good when run with the sub. I even tried the recommended "Cardas" setup locations and the curves were much worse.
> 
> ...



Sorry i didn't request a near field measurement of your speakers.

The IR response wasn't the one i was after, maybe post the mdat file?

If your speakers go down to 32hz then (are they stand mount) you need to get the speakers right first, forget about the REL at the moment. With RELS the speakers have to be setup well for them to work.

Try moving the mic around with the RTA or sweep, you might be sitting in a dip?

Looking at the trend of your measurements they all represent the same.

When you move the sub close to the corner you have to adjust crossover/level.


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## eyesandears (Apr 25, 2012)

The only nearfield I posted was the sub to be sure it was working correctly. All the other curves are with the mic at the primary listening position.

I moved the mic around to survey the room. I found lots of low end energy 2' from the side walls. I confirmed the dip extends the center of the room lengthwise. 

I will reposition the main speakers to their best location and retry it. At that location they started to roll off at ~45 Hz but eliminated the large dip you can see at 48 Hz. Even with that they are still -12 dB at 32Hz. Moving the mains did not change the shape or depth of the dip at 32 Hz at all.

I posted the .mdat file on my first post. It's just below the attached pic. named " mains + sub (bass only)..."

If that doesn't work I'll try posting it again. Thanks for the all the help!


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## Phillips (Aug 12, 2011)

The mains,are they stand mount or floor standers?
You should be able to get pretty close to 32hz unless your room is big etc.

The reason for the nearfield of the main speaker is to see the extension without as much as the room as possible.

Also can you label the meaurements (left, right etc).

Don't worry about the dip at 90hz at the moment.


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## eyesandears (Apr 25, 2012)

The speakers are floor standing. 









I'll get some nearfield curves and post tomorrow. 

BTW, Where is the label function in REW?


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## Phillips (Aug 12, 2011)

eyesandears said:


> The speakers are floor standing.
> 
> View attachment 39243
> 
> ...



I checked your first post but there was only one measurement

The label is on the left of each measurement, where it gives the date, you can click in there and change.

Please post the near field measurement for the main as a jpeg.

Please post the mdat file for:

1. Left main only
2. Right main only
3. Both left & main together
4. Sub only
5. Mains & Sub combined


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## eyesandears (Apr 25, 2012)

Here are the nearfield measurements of my main speakers. They appear to be functioning normally and match similar measurments I was able to retrieve from an old Stereophile review.

FYI my speakers have two rear ports. The nearfield still has a peculiar dip at 32Hz but when you measure the rear port there is no dip and good low bass extension. This same dip was also seen on the Stereophile review measurment. I plotted one of the rear ports also on the graph.









I am in the process of repositioning my main speakers. I'll post an updated .mdat file ASAP!


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## Phillips (Aug 12, 2011)

eyesandears said:


> Here are the nearfiel measurements of my main speakers. They appear to be functioning normally and match similar measurments I was able to retrieve from an old Stereophile review.
> 
> FYI my speakers have two rear ports. The woofer still has a peculiar dip at 32Hz but when you measure the rear port there is no dip and good low bass extension. This same dip was also seen on the Stereophile review measurment. I plotted one of the rear ports also on the graph.
> 
> ...



Can you please do a near field with all main speaker drivers playing.

Those ports could be causing problems, rear ports can improve or make it worse, i can't have rear ports in my room, restricted to positioning.

Looking at your first measurement just for the sub only and this had a dip at the same frequency as well.

As a experiment have you placed the speakers along way from any boundaries (walls etc)?

Maybe bung one port (or two) with a clean sock etc, to see if that makes a difference.


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## eyesandears (Apr 25, 2012)

I'm unclear on your request. The nearfields I posted were done with the mic about 1" from one of the woofers but all the drivers in that speaker were running. Did you want the opposite speaker drivers running also?


I was also wondering if the ports were causing a problem. I still have the foam port plugs that came with the speakers. I will take some measurments with them in tonight. Would you agree that the finding that the sub had a similar dip at 32Hz might indicate either a speaker of room interaction?

I will also take some more measurments with the speakers further from boundaries. Now they are approx. 60" from front wall and 28" from side walls.


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## Phillips (Aug 12, 2011)

> I'm unclear on your request. The nearfields I posted were done with the mic about 1" from one of the woofers but all the drivers in that speaker were running. Did you want the opposite speaker drivers running also?


Ok don't worry about that request.




> I was also wondering if the ports were causing a problem. I still have the foam port plugs that came with the speakers. I will take some measurments with them in tonight. Would you agree that the finding that the sub had a similar dip at 32Hz might indicate either a speaker of room interaction?


Yeah i think so. I think it is the room interaction. With the ports (rear) plugged gives options for closer wall placement.



> I will also take some more measurments with the speakers further from boundaries. Now they are approx. 60" from front wall and 28" from side walls.


Use the general rule of thumb 3rds for speaker placement and listening positions. Also use odd numbers e.g. 3 , 5 ,7 etc.


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## eyesandears (Apr 25, 2012)

Did the port plug experiment last night. Bad news. Tried one port and both ports plugged as well as moving the speakers close to the boundaries and further away and in all cases the 32Hz dip was wider and deeper with the ports plugged than open.

I am still in the process of finding the optimal location for the mains but I can't find any position in the front half of the room that reduces the 32Hz dip. I am going to take a few more measurements and post back my latest results.


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## Phillips (Aug 12, 2011)

During that time measuring can you post the mdat files for the (don't forget to label):
Mains (each L&R) 
Combined mains 
REL only
REL with combined mains.

Then we can look at the phase of the sub.


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## eyesandears (Apr 25, 2012)

During that time measuring can you post the mdat files for the (don't forget to label):
Mains (each L&R) 
Combined mains 
REL only
REL with combined mains.

Then we can look at the phase of the sub.[/quote]

You kept me busy with lot's of homework past few days!! :R

Here are the measurment files as requested. 

View attachment Left main.mdat


View attachment Right Main.mdat


View attachment Mains combined.mdat


View attachment Mains + REL.mdat


View attachment REL only.mdat


Combined mains + REL curve with modified speaker and listening position.









I believe I made some good progress. No location of the mains had any effect on the 32 Hz dip but did improve low frequency roll off point by ~10 Hz lower. 

Moved the primary listening position forward 2.5 feet and that improved the 32 Hz problem. It is now very clear to me that the mains and primary locations for viewing movies will need to be adjusted for critcal 2 channel listening.

:T


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## Phillips (Aug 12, 2011)

1. How does it sound?

2. I looked at the files and and from 25hz to 100hz looks great, what crossover and phase settings are you using?

3. Looking at the full range graph (attached) there is a very large (sudden) increase at about 160-170hz.
The attached graph as per label gives you a idea of a target curve (there are others as well) for 2 channel music. 

4. With the high end how does it sound?


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## eyesandears (Apr 25, 2012)

Phillips said:


> 1. How does it sound?
> 
> 2. I looked at the files and and from 25hz to 100hz looks great, what crossover and phase settings are you using?
> 
> ...




I think it sounds better in the new listening position. I don't appreciate a mid or high end problem and it certainly doesn't sound bass heavy or bloated. I did not have the mic placed very precisely for the very high end response which I find the roll off very sensitive to mic positioning. I did see the low end bump start to flatten with the rest of the mid and high end curve as I moved the speakers much further into the room toward the listening position. I might experiment more with that and see how it sounds.

How did you determine your target curve? The target curve in Paul Spencer's article attached below seems more like what I am seeing except mine is perhaps a bit more exaggerated.









http://www.hifizine.com/2011/06/bass-integration-guide-part-1/

You will notice that the mains without the sub also have this interesting fall off you mention at the same frequency. What I tried to do with the sub is really just extend and smooth out the area below ~50 Hz where the speaker roll off. 

The sub is now at 180 deg. phase, crossover 11:00 and I think that is ~40 Hz. Level 12:00. It's location (measured to front mid woofer) ended up exactly 38" from both front and side walls in right front corn of the room angled diagonally pointing to the opposite rear room corner.. When I tried to move it closer to the walls it help boost it's level but increased the 40-60 Hz frequencies disproportionaltlely even at at the minimum 30 Hz crossover setting. I could never get a flat curve there.


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## AudiocRaver (Jun 6, 2012)

eyesandears said:


> No location of the mains had any effect on the 32 Hz dip but did improve low frequency roll off point by ~10 Hz lower.
> 
> Moved the primary listening position forward 2.5 feet and that improved the 32 Hz problem.


A passing comment, and pardon me if I am missing something obvious. If your graph above is illustration of your "32 Hz problem," many of us would love to have a 32 Hz problem that small. Not to minimize your right to pursue perfection (life, liberty, pursuit of perfect bass?), just that room modes at 32 Hz are not easy to deal with, and getting better than what you have could prove to be prohibitive. The whole curve looks pretty good to me. But then I have been known to chase perfection down the rabbit hole a time or two myself. Best of luck!:whistling:


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## eyesandears (Apr 25, 2012)

AudiocRaver said:


> A passing comment, and pardon me if I am missing something obvious. If your graph above is illustration of your "32 Hz problem," many of us would love to have a 32 Hz problem that small. Not to minimize your right to pursue perfection (life, liberty, pursuit of perfect bass?), just that room modes at 32 Hz are not easy to deal with, and getting better than what you have could prove to be prohibitive. The whole curve looks pretty good to me. But then I have been known to chase perfection down the rabbit hole a time or two myself. Best of luck!:whistling:


Thanks for your comments all are always welcome. I'l admit I am a bit of a perfectionist myself. :hissyfit:

I'm not sure which graph you are referring to. The latest one I posted I am very happy with and have corrected most of the low end issues I was seeing. If you look back to my first post you will see where I started out and the wide 12dB null at 32 Hz. It was clearly noticeable when listening. It required moving the listening position to eliminate. 

Cheers!


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## Phillips (Aug 12, 2011)

You are happy with the sound, so that is all that counts.

That's all we want, is perfection but rooms get in the road.


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## AudiocRaver (Jun 6, 2012)

eyesandears said:


> Thanks for your comments all are always welcome. I'l admit I am a bit of a perfectionist myself. :hissyfit:
> 
> I'm not sure which graph you are referring to. The latest one I posted I am very happy with and have corrected most of the low end issues I was seeing. If you look back to my first post you will see where I started out and the wide 12dB null at 32 Hz. It was clearly noticeable when listening. It required moving the listening position to eliminate.
> 
> Cheers!


Whoops, I was looking at the wrong curve. You _did_ start out with an ugly 32 Hz problem, and solved it quite nicely. Now you are one of the experts! And proof that it can be done!

Nice job, and happy listening.:T


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## eyesandears (Apr 25, 2012)

Phillips said:


> You are happy with the sound, so that is all that counts.
> 
> That's all we want, is perfection but rooms get in the road.


Agree! Thanks for all your help. I always learn something from these exercises.

When you get a few minutes I would like your opinion on the waterfall and decay plots.
With the exception of some bass trapping I may have created in the large riser, room furniture and drapes this room has no accustic treatments. I was wondering if some broadband bass trapping might be useful.


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## Phillips (Aug 12, 2011)

Glad i could help.

The waterfall graph looks ok considering the rise at about 170hz down.

There is a paper you can read on Acoustic Frontiers Blog (Nyal Mellor) with really good acoustic info targets.

Different house curves will sound different in other rooms.

I would still play around a bit with placement for all speakers, sub. Remember to make sure you mark where you have it now as a reference. The sub i feel you could get that extra few hz out of it. I have had the REL Stampede which was a 8 inch driver that could go down to 18hz, and RELs data was correct. I am not saying you will but after careful setup you never know.


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