Bass trapping below 80hz, practical or not?

[yepimonfire]

My room is already well treated using Auralex 2” wedgies, this has vastly improved the sound and imaging above 500hz. I still have a lot of issues down around 50hz, and am wondering if it’s practical to reduce this with bass traps or not. AFAIK, sub bass frequencies require very large distances from the walls or corners in order to really be effective. The only other option would be something like an Auralex mega LENRD, which is the only foam corner treatment shown to actually work that low, and it would take up a lot less space that an OC 703 corner trap. Unfortunately, they’re also very expensive.

What solutions are there for treating sub bass frequencies that don’t require a large l a loss of space?

 

[everettT]

Is it practical in your room? That's the only question. I'd put money towards better subs before spending money on treatmeants. If your room is the weak link with your bass, it can be determined and addressed after.

 

[highfigh]

My room is already well treated using Auralex 2” wedgies, this has vastly improved the sound and imaging above 500hz. I still have a lot of issues down around 50hz, and am wondering if it’s practical to reduce this with bass traps or not. AFAIK, sub bass frequencies require very large distances from the walls or corners in order to really be effective. The only other option would be something like an Auralex mega LENRD, which is the only foam corner treatment shown to actually work that low, and it would take up a lot less space that an OC 703 corner trap. Unfortunately, they’re also very expensive.

What solutions are there for treating sub bass frequencies that don’t require a large l a loss of space?

It's not attractive, but 2" panels along two adjacent walls is effective. Attenuating bass frequencies requires mass, not distance. The issues I had in my room caused the sound to change just by moving my head to one side or thee other by only a few inches and when I moved, I could hear phase problems- if you have held a raw driver in your hand so its motion was at 90 degrees from you, you might know how this feels. It was bad enough that I decided to start by moving my speakers (after placing blue painter's tape on the carpet, to mark the original location) but that didn't cure it so I brought the panels I had made for a demo in and fired up Room EQ Wizard, so I could look at the response as I moved the panels at different spots. They're mostly 2' x 4', 2" thick with a couple that are 4" thick. I also had some that are the same height and thickness, but 12" wide, which I stacked on top of the bottom ones to cover more height. I could probably achieve the same level of attenuation with a heavy column that has absorptive material, but I already had these and they did the trick- the problem is gone and the response shows it.

 

[yepimonfire]

It's not attractive, but 2" panels along two adjacent walls is effective. Attenuating bass frequencies requires mass, not distance. The issues I had in my room caused the sound to change just by moving my head to one side or thee other by only a few inches and when I moved, I could hear phase problems- if you have held a raw driver in your hand so its motion was at 90 degrees from you, you might know how this feels. It was bad enough that I decided to start by moving my speakers (after placing blue painter's tape on the carpet, to mark the original location) but that didn't cure it so I brought the panels I had made for a demo in and fired up Room EQ Wizard, so I could look at the response as I moved the panels at different spots. They're mostly 2' x 4', 2" thick with a couple that are 4" thick. I also had some that are the same height and thickness, but 12" wide, which I stacked on top of the bottom ones to cover more height. I could probably achieve the same level of attenuation with a heavy column that has absorptive material, but I already had these and they did the trick- the problem is gone and the response shows it.

2” & 4” panels mounted flush to the walls or straddling corners? Unless you know something I don’t, 4” panels of rigid fiberglass stop being effective at about 125hz.

What I meant by distance is placing 2” or 4” panels in the corners, in order to effectively damp a given frequency, a panel must be placed 1/4 wavelength from a room boundary, at 50hz, that’s about 6’! The other option is something like a super chunk, but that still requires a good bit of thickness, especially below 80hz.

What problem frequencies did you get improvement in and how are the panels set up exactly?

I had phase and comb filtering problems similar to what you described at mid to high frequencies, but that was solved via the Auralex wedgies.

My issue is simply a massive one note buildup at 50hz.

 

[ski2xblack]

How many subs are you running? It's probably even less cumbersome to add another sub for modal smoothing than cluttering up your space with (necessarily large) bass traps.

 

[WaynePflughaupt]

I still have a lot of issues down around 50hz, and am wondering if it’s practical to reduce this with bass traps or not.

You didn’t say what kind of issues. If it’s poor frequency response, go with parametric EQ. Traps mainly reduce ringing.

Regards,
Wayne A. Pflughaupt

 

[highfigh]

2” & 4” panels mounted flush to the walls or straddling corners? Unless you know something I don’t, 4” panels of rigid fiberglass stop being effective at about 125hz.

What I meant by distance is placing 2” or 4” panels in the corners, in order to effectively damp a given frequency, a panel must be placed 1/4 wavelength from a room boundary, at 50hz, that’s about 6’! The other option is something like a super chunk, but that still requires a good bit of thickness, especially below 80hz.

What problem frequencies did you get improvement in and how are the panels set up exactly?

I had phase and comb filtering problems similar to what you described at mid to high frequencies, but that was solved via the Auralex wedgies.

My issue is simply a massive one note buildup at 50hz.

Flat on the walls.

Oh, you have a peak? I had a deep suckout.

Can you post room dimensions? You may need to move something (sub, speakers). If you haven't, use a room mode calculator to see if this is just a natural mode with positive reinforcement.

 

[yepimonfire]

Flat on the walls.

Oh, you have a peak? I had a deep suckout.

Can you post room dimensions? You may need to move something (sub, speakers). If you haven't, use a room mode calculator to see if this is just a natural mode with positive reinforcement.

Room is 12x11. I already know the issue is a room mode. The sub placement has already been experimented with, unfortunately there’s no placement solution that results in flat bass, I either have to deal with peaks, which are solved easily with eq, or cancellation, which is unsolvable.

 

[TheWarrior]

Room is 12x11. I already know the issue is a room mode. The sub placement has already been experimented with, unfortunately there’s no placement solution that results in flat bass, I either have to deal with peaks, which are solved easily with eq, or cancellation, which is unsolvable.

You're posting all over the place and providing little useful detail, or even measurements. I think there's been a dozen or so posts that could have been consolidated into one.

With that said; 1131 / (2 x 11 feet) = 51.4 hz with 103 hz being the second order mode - which explains why you think you need 'full range eq'.

Is 11 feet your width or length relative to LP, and where is the LP? Or is this a bedroom and your head is at the back wall? You have only defined two dimensions in a 3 dimensional space without instruction on where your ears/microphone are located.

Learning to manipulate subwoofers means you need to learn how and where in the room peaks and nulls occur as a result of the listeners position to defined room boundaries. EQ is extremely limited in it's ability, and the reality is if the correct number of subwoofers cannot be located in the correct places, some frequencies simply won't be heard at every seat - regardless of how flat a measured response is, flat is not the goal! If resonances are the building blocks of sound, you need to clearly define in your own measurements which resonances are resulting from room boundaries/modes, and which ones just 'are'. EQing them all out may result in a slower or dull sounding room. It becomes fun and exciting to hear/feel your room shake that you lose sight of the 'tight and fast' goal.

Sometimes all you have to do is move a subwoofer so that a peak or null is moved a few feet away from a listeners ears. It may break the visual symmetry, but form has to follow function when you are trying to overcome the control of a room.

 

[gene]

You're posting all over the place and providing little useful detail, or even measurements. I think there's been a dozen or so posts that could have been consolidated into one.

With that said; 1131 / (2 x 11 feet) = 51.4 hz with 103 hz being the second order mode - which explains why you think you need 'full range eq'.

Is 11 feet your width or length relative to LP, and where is the LP? Or is this a bedroom and your head is at the back wall? You have only defined two dimensions in a 3 dimensional space without instruction on where your ears/microphone are located.

Learning to manipulate subwoofers means you need to learn how and where in the room peaks and nulls occur as a result of the listeners position to defined room boundaries. EQ is extremely limited in it's ability, and the reality is if the correct number of subwoofers cannot be located in the correct places, some frequencies simply won't be heard at every seat - regardless of how flat a measured response is, flat is not the goal! If resonances are the building blocks of sound, you need to clearly define in your own measurements which resonances are resulting from room boundaries/modes, and which ones just 'are'. EQing them all out may result in a slower or dull sounding room. It becomes fun and exciting to hear/feel your room shake that you lose sight of the 'tight and fast' goal.

Sometimes all you have to do is move a subwoofer so that a peak or null is moved a few feet away from a listeners ears. It may break the visual symmetry, but form has to follow function when you are trying to overcome the control of a room.

Actually if multi-sub is properly implemented and reduces seat-seat variances, then EQ can be a VERY effective tool that will help all seats to reduce modal issues and SOMETIMES fix minor nulls.

See:http://www.audioholics.com/home-theater-calibration/bass-optimization-for-home-theater

Multi-sub + EQ reduces and SOMETIMES eliminates the need for LF room treatments at and below the subwoofer crossover as well. Harman does incredible demos every year at CEDIA of their JBL synthesis system with 8 subs (2/ea corner loaded) with NO passive room treatments, and the bass is linear, and consistent for EVERY seat in the demo room.

 

[TheWarrior]

Actually if multi-sub is properly implemented and reduces seat-seat variances, then EQ can be a VERY effective tool that will help all seats to reduce modal issues and SOMETIMES fix minor nulls.

See:http://www.audioholics.com/home-theater-calibration/bass-optimization-for-home-theater

Multi-sub + EQ reduces and SOMETIMES eliminates the need for LF room treatments at and below the subwoofer crossover as well. Harman does incredible demos every year at CEDIA of their JBL synthesis system with 8 subs (2/ea corner loaded) with NO passive room treatments, and the bass is linear, and consistent for EVERY seat in the demo room.

I agree that multi sub is excellent and EQ is very effective, albeit limited in it's range usefulness.

Part of my frustration is that you need to read one Yep's other threads to know that they only have two subs and may be limited in placement options, but again, lots of threads and sparse details.

 

[yepimonfire]

I agree that multi sub is excellent and EQ is very effective, albeit limited in it's range usefulness.

Part of my frustration is that you need to read one Yep's other threads to know that they only have two subs and may be limited in placement options, but again, lots of threads and sparse details.

To clarify:

This is a small bedroom setup. The room is 12x11x8, the system is oriented along the length dimension, the seats are about a foot off the back wall.

There is a closet that is semi open with sliding doors at the front left side of the room. This is a no go placement area because for whatever reason the closet causes a loss of anything below 40hz.

The two practical options for the sub is either the front right corner, which results in a 10dB peak at 50hz, or the rear right corner, which results in a 6dB peak at 50hz. I chose the front right corner because it offers a completely even response throughout the back of the room can the rear corner. It may be peaky, but it is consistently peaky everywhere lol.

The thinking behind bass trap treatments has to do with the fact it seems Audyssey has a harder time correcting the response in this room vs my larger living room, which is significantly less problematic. Here is the latest calibration results

I don’t think eq is incapable of fixing the issue, just that Audyssey is having a harder time sorting out what is a room problem that can be corrected and what isn’t because the peaks are so extreme.

Using manual parametric EQ via equalizer apo on my pc, on my front l/r speakers (no sub), I managed to achieve almost perfectly flat bass as you can see here

I will have to upload an uncorrected graph tomorrow morning, but it really boils down to nothing more than a giant 10dB peak centered at 50hz that’s about 12dB/octave wide.

So far, I have come up with a few possible solutions, I guess what I’m asking is which would be most effective while still being practical from a cost and space standpoint.

Option one:
Using a minidsp on the subwoofer to flatten the worst peaks, leaving Audyssey with less work to do and theoretically achieving better results post calibration.

Option two would be minidsps on all 7 speaker and the sub, however, that can get very costly with all the necessary external amplification.

Option three I’ve considered is similar to what @gene mentioned, multiple subs to give a perfectly even response, with a high (120hz) xover and minidsps on the subs only. The issue I am running into with this is finding a sub that is both small enough to use in multiple locations considering the limited space, while also achieving an f3 of at least 25hz.

The subwoofer currently in use is a Dayton sub 1500, which, as you can see from the above measurements, extends to 22hz -3dB and still has useful output @19Hz -6dB. The only 10” sub I’ve found so far that can achieve a decent response below 30hz is the svs pb 1000, which is too large due to the cabinet size. Most smaller subs roll of below 30hz, which seems pointless imo considering my front speakers can achieve decent output at 30hz in room with minimal distortion without the help of a sub.

If I went the multiple sub route, considering the room size, would something like 2-3 Dayton 10” ultimax subs eq’ed via a linkwitz transform to 20hz give enough output, or would it be pushing the drivers too hard? As I previously said, I will upload some more graphs and a diagram later, but with room gain I get 10dB @50hz, 5dB @25hz, and 3dB @20Hz.

 

[TheWarrior]

To clarify:

This is a small bedroom setup. The room is 12x11x8, the system is oriented along the length dimension, the seats are about a foot off the back wall.

There is a closet that is semi open with sliding doors at the front left side of the room. This is a no go placement area because for whatever reason the closet causes a loss of anything below 40hz.

The two practical options for the sub is either the front right corner, which results in a 10dB peak at 50hz, or the rear right corner, which results in a 6dB peak at 50hz. I chose the front right corner because it offers a completely even response throughout the back of the room can the rear corner. It may be peaky, but it is consistently peaky everywhere lol.

The thinking behind bass trap treatments has to do with the fact it seems Audyssey has a harder time correcting the response in this room vs my larger living room, which is significantly less problematic. Here is the latest calibration results

I don’t think eq is incapable of fixing the issue, just that Audyssey is having a harder time sorting out what is a room problem that can be corrected and what isn’t because the peaks are so extreme.

Using manual parametric EQ via equalizer apo on my pc, on my front l/r speakers (no sub), I managed to achieve almost perfectly flat bass as you can see here

I will have to upload an uncorrected graph tomorrow morning, but it really boils down to nothing more than a giant 10dB peak centered at 50hz that’s about 12dB/octave wide.

So far, I have come up with a few possible solutions, I guess what I’m asking is which would be most effective while still being practical from a cost and space standpoint.

Option one:
Using a minidsp on the subwoofer to flatten the worst peaks, leaving Audyssey with less work to do and theoretically achieving better results post calibration.

Option two would be minidsps on all 7 speaker and the sub, however, that can get very costly with all the necessary external amplification.

Option three I’ve considered is similar to what @gene mentioned, multiple subs to give a perfectly even response, with a high (120hz) xover and minidsps on the subs only. The issue I am running into with this is finding a sub that is both small enough to use in multiple locations considering the limited space, while also achieving an f3 of at least 25hz.

The subwoofer currently in use is a Dayton sub 1500, which, as you can see from the above measurements, extends to 22hz -3dB and still has useful output @19Hz -6dB. The only 10” sub I’ve found so far that can achieve a decent response below 30hz is the svs pb 1000, which is too large due to the cabinet size. Most smaller subs roll of below 30hz, which seems pointless imo considering my front speakers can achieve decent output at 30hz in room with minimal distortion without the help of a sub.

If I went the multiple sub route, considering the room size, would something like 2-3 Dayton 10” ultimax subs eq’ed via a linkwitz transform to 20hz give enough output, or would it be pushing the drivers too hard? As I previously said, I will upload some more graphs and a diagram later, but with room gain I get 10dB @50hz, 5dB @25hz, and 3dB @20Hz.

Thank you for the details!

Now, first things first, FLAT IS NOT THE GOAL! I think there's a lot of readers that would like to get a 5 dB gain at 25 hz (particularly the owners of PSA subs - I keed, I keed! Lol!) It's really a silly concept when you consider the size of wavelengths being picked up by an Omni-Directional mic, how can any two rooms measure the same? (this was also covered in Floyd Toole's "Measurement and Calibration of Sound Reproducing Systems" - a free AES article, as a further explanation of why current 'Room Correction' solutions are fundamentally flawed)

I'm really trying to drive that point home as a rhetorical question to anyone (cuz I keep having to reinforce it)- if resonances are the building blocks of all sound, why are you arbitrarily cancelling out 'peaks' that are not centered on a modal frequency?

But what you may not realize, is you're giving yourself the data you need by recording measurements with different sub positions. If positioning a pressure source at either end of the 11' wall is causing a 5-10 dB gain at a predicted frequency, congratulations, you have just influenced a room mode! Now to drive that standing wave away from your LP.

The boundaries of your room, or really anyones room are smaller in dimension than most of the bass wavelengths being reproduced. And as I've seen you post, you understand that even 1/4 wavelengths can be an issue - you just don't always seem to apply that math correctly to absorption and give thin foam waaaay too much credit.

If you search Harman White Papers you will find subwoofer integration articles from Todd Welti, who created the MSV - Mean Spatial Variance metric which defines a value for the SPL level differences, seat to seat. His research in to integrating subs in to small rooms went from 1 subwoofer, to infinity. The simple take away is the more subwoofers (regardless of size) the more even the bass distribution will be throughout the room.

So if you can provide a detailed layout of the room, speaker complement, LFE crossover, and measurements withOUT DSP or Audyssey we might be able to help you situate your equipment to save you from needing to shoehorn additional subs into a small space.

 

[yepimonfire]

Thank you for the details!

Now, first things first, FLAT IS NOT THE GOAL! I think there's a lot of readers that would like to get a 5 dB gain at 25 hz (particularly the owners of PSA subs - I keed, I keed! Lol!) It's really a silly concept when you consider the size of wavelengths being picked up by an Omni-Directional mic, how can any two rooms measure the same? (this was also covered in Floyd Toole's "Measurement and Calibration of Sound Reproducing Systems" - a free AES article, as a further explanation of why current 'Room Correction' solutions are fundamentally flawed)

I'm really trying to drive that point home as a rhetorical question to anyone (cuz I keep having to reinforce it)- if resonances are the building blocks of all sound, why are you arbitrarily cancelling out 'peaks' that are not centered on a modal frequency?

But what you may not realize, is you're giving yourself the data you need by recording measurements with different sub positions. If positioning a pressure source at either end of the 11' wall is causing a 5-10 dB gain at a predicted frequency, congratulations, you have just influenced a room mode! Now to drive that standing wave away from your LP.

The boundaries of your room, or really anyones room are smaller in dimension than most of the bass wavelengths being reproduced. And as I've seen you post, you understand that even 1/4 wavelengths can be an issue - you just don't always seem to apply that math correctly to absorption and give thin foam waaaay too much credit.

If you search Harman White Papers you will find subwoofer integration articles from Todd Welti, who created the MSV - Mean Spatial Variance metric which defines a value for the SPL level differences, seat to seat. His research in to integrating subs in to small rooms went from 1 subwoofer, to infinity. The simple take away is the more subwoofers (regardless of size) the more even the bass distribution will be throughout the room.

So if you can provide a detailed layout of the room, speaker complement, LFE crossover, and measurements withOUT DSP or Audyssey we might be able to help you situate your equipment to save you from needing to shoehorn additional subs into a small space.

I definitely agree some amount of room gain sounds natural, but 10dB at a single frequency does not lol. Harman has a shelved response from 60hz and below built into their target curve. This could easily be recreated by simply crossing my speakers at 60hz and bumping the sub up higher.

Speakers are RP-160m, response is 32hz -3dB and they are crossed over at 40hz. Placement is about 2’ from the front wall and 20” from the side wall. Center is rp 250c and it’s response is 50hz -3dB and it’s crossed over at 60hz. Surrounds are rp 150m, -3dB at 47hz and crossed at 60hz as well. Those are placed in the rear corners of the room.

Still have to upload measurements, but I have no major bass response problems with the center and surrounds. It’s mainly the l/r and sub. The sub is flush to the right front corner. Since the actual listening area is rather small, perfect response around the room isn’t necessary.

I can’t really move the speakers, placing them further from the side walls would likely help reduce the peak, but it would also wreck the sound stage, since they’re placed 7’ apart which is almost exactly 22 degrees from center reference.

I could cross the speakers at 80hz if need be, but it didn’t make a difference when I did.

 

[TheWarrior]

I definitely agree some amount of room gain sounds natural, but 10dB at a single frequency does not lol. Harman has a shelved response from 60hz and below built into their target curve. This could easily be recreated by simply crossing my speakers at 60hz and bumping the sub up higher.

I don't know what this target curve is, nor did you quote me correctly, but it sounds like you're blurring the lines between a room curve and anechoic speaker measurements. Despite that, it seems we've already found your first solution, change your LFE crossover:

If you have a resonance at 50 hz, but the sub is rolled off at 40 hz, you have no way to influence that mode!

Based on your dimensions, an 80 hz LFE crossover puts your subwoofers in control of the length, width, height modes of your room.

So it's good you posted this first before measuring! I would start with an 80 hz crossover, with no DSP or Audyssey influence.

 

[highfigh]

Crossing the L/Rspeakers at 40Hz, Center at 60Hz and surrounds at 60Hz and expecting the crossovers to have a brick wall effect will get you...... peaks where you don't want them. You need to look at this as it would be taught in a Physics class when they work with wave theory- the sound energy from each speaker will interact with the sound energy from all of the others. You can't stop that unless you only allow each to play when the others aren't, or put them in separate rooms. At any other time, the interaction will result in interference- both constructive and destructive. The thing that makes it different from the Physics class water tank is that we're working in three dimensions.

If you set the sub to 60Hz and the rest of the speakers to work above 80Hz, you won't lose anything because the crossover slope will still allow all speakers to produce sound between those frequencies. In fact, even with 18dB/octave slope on the sub and 12dB/octave on the rest, you may need to work with the range where the crossovers overlap in order to reduce the hump (or raise the surrounding frequencies and drop the overall level). If the sub is currently crossed over at 60Hz, it would explain the hump in your response. Sometimes, it's necessary to create a gap in the response in order to smooth the overall response.

Run the RTA with no crossover and only the main speakers, then the center, then only the sub, then only the surround speakers. Once you have measured for these, run the mains and add the center and look at the changes. Continue by adding the surrounds and note any changes. Hold off adding the sub- if you still see a rise in the 40Hz-60Hz region, it's an issue of room modes and mic placement. If it's smooth and you see no problems, add the sub- what happens? If the crossover is set below the range of the other speakers, introduce them to your li'l fren', errr, the HP crossover. Raise it to 60Hz, then 80Hz and watch the response. Work with the sub's crossover until you see what you want, then listen to some music and adjust accordingly.

When I had an AVR, I found that setting the increments for distance to .1 foot made it possible to tweak the sound much better- the difference between ex. 12.3' and 12.4' was slightly audible, but having .2' difference could definitely be heard. It could be seen on the RTA, too.

Remember- as posted before, flat ISN'T what you want- you want a "house curve", which is smooth, with a definite downward tilt from low frequencies to high frequencies. Flat doesn't sound good- it just allows designers to create a known response in certain conditions.

Don't worry if you think the sound of the system is better with deviations from flat and/or smooth- find a curve you like and go with it.

 

[everettT]

Again the measurements are not with a calibrated microphone so it might be better to use worksheets and an spl meter. All the back and forth without true information is a wasted exercise.

I'll add as I did in one of the other threads and as highfigh points out, the crossover to the sub is way off. At least an octave higher and more would be better. It took me a good amount of time to dial in my subs.

 

[TheWarrior]

Crossing the L/Rspeakers at 40Hz, Center at 60Hz and surrounds at 60Hz and expecting the crossovers to have a brick wall effect will get you...... peaks where you don't want them. You need to look at this as it would be taught in a Physics class when they work with wave theory- the sound energy from each speaker will interact with the sound energy from all of the others. You can't stop that unless you only allow each to play when the others aren't, or put them in separate rooms. At any other time, the interaction will result in interference- both constructive and destructive. The thing that makes it different from the Physics class water tank is that we're working in three dimensions.

If you set the sub to 60Hz and the rest of the speakers to work above 80Hz, you won't lose anything because the crossover slope will still allow all speakers to produce sound between those frequencies. In fact, even with 18dB/octave slope on the sub and 12dB/octave on the rest, you may need to work with the range where the crossovers overlap in order to reduce the hump (or raise the surrounding frequencies and drop the overall level). If the sub is currently crossed over at 60Hz, it would explain the hump in your response. Sometimes, it's necessary to create a gap in the response in order to smooth the overall response.

Run the RTA with no crossover and only the main speakers, then the center, then only the sub, then only the surround speakers. Once you have measured for these, run the mains and add the center and look at the changes. Continue by adding the surrounds and note any changes. Hold off adding the sub- if you still see a rise in the 40Hz-60Hz region, it's an issue of room modes and mic placement. If it's smooth and you see no problems, add the sub- what happens? If the crossover is set below the range of the other speakers, introduce them to your li'l fren', errr, the HP crossover. Raise it to 60Hz, then 80Hz and watch the response. Work with the sub's crossover until you see what you want, then listen to some music and adjust accordingly.

When I had an AVR, I found that setting the increments for distance to .1 foot made it possible to tweak the sound much better- the difference between ex. 12.3' and 12.4' was slightly audible, but having .2' difference could definitely be heard. It could be seen on the RTA, too.

Remember- as posted before, flat ISN'T what you want- you want a "house curve", which is smooth, with a definite downward tilt from low frequencies to high frequencies. Flat doesn't sound good- it just allows designers to create a known response in certain conditions.

Don't worry if you think the sound of the system is better with deviations from flat and/or smooth- find a curve you like and go with it.

That's a lot to unpack but while I agree that the water tank is not an accurate comparison to sound reproduction in rooms and that flat is not the goal, inducing a gap into the system playback with subs rolled off at 60 hz and speakers playing at 80 hz is not a solution that favors accurate sound reproduction.

You have to look at this as it would be taught in physics! Yep has taken measurements with the subs rolled off at 40 hz and was able to reduce SPL by 5 dB @ 50 hz by sitting between the subwoofers placed in corners to the Left and Right with the front speakers providing most of (not all) amplitude for the 50 hz modal frequency.

12' = 47 hz
11' = 51 hz
8' = 70 hz

If Yep was sitting nearer the middle of the room, they could use the front speakers down to their natural roll off if desired, but because the LP is near the back wall, only the correct placement of subwoofers can control those peaks. Or just cut off all playback to 80 hz, lose the subs and 'fahget abott it!'

 

[yepimonfire]

That's a lot to unpack but while I agree that the water tank is not an accurate comparison to sound reproduction in rooms and that flat is not the goal, inducing a gap into the system playback with subs rolled off at 60 hz and speakers playing at 80 hz is not a solution that favors accurate sound reproduction.

You have to look at this as it would be taught in physics! Yep has taken measurements with the subs rolled off at 40 hz and was able to reduce SPL by 5 dB @ 50 hz by sitting between the subwoofers placed in corners to the Left and Right with the front speakers providing most of (not all) amplitude for the 50 hz modal frequency.

12' = 47 hz
11' = 51 hz
8' = 70 hz

If Yep was sitting nearer the middle of the room, they could use the front speakers down to their natural roll off if desired, but because the LP is near the back wall, only the correct placement of subwoofers can control those peaks. Or just cut off all playback to 80 hz, lose the subs and 'fahget abott it!'

I don’t have too much issues with 70hz except with the top middle speakers, which are mounted a few inches from the ceiling.

Sitting about 38% backwards or forwards from the front or rear wall actually yields a pretty flat response. Unfortunately this isn’t practical.

Assuming I found a better spot for the sub, is an 80hz xover sufficiently high enough to avoid serious interactions from the speakers?

I may do a sub crawl with the mic vs my ears.

 

[yepimonfire]

@everettT

The mic may not be perfectly calibrated but the bass response measured in REW is pretty much identical to the uncorrected response displayed in the Audyssey app, so its good enough.