Absorbers as bass traps - question regarding absorber's backwall.

Martin1703

Member
Thread Starter
Joined
Jul 6, 2022
Messages
19
My AV System  
Preamp, Processor or Receiver
Musical Fidelity M8s-PRE
Main Amp
Musical Fideltiy M8s-500s
Computer Audio
MacBook
DAC
Denafrips Pontus II
Front Speakers
Focal Kanta 2
Subwoofers
REL S/510
Streaming Equipment
Roon Nucleus+
Streaming Subscriptions
Quobuz
As always, thank you both for your input, support, and guidance!


Was there a question in there? If you were to have several other speakers or multiple subwoofers you might look for speaker management hardware... Personally I would not put a ~$300 A/D/A in between my gear... I guess if you had horns and bass bins to manage, or some other speaker array(s), this might be the way to go... Your not planning on any DIY mods to your Focals are you? Like deleting the internal crossovers and controlling each driver separately... So bi/multi-amping is out... Again, something for the likes of horns and bass bins... And you have a pair of nice Focals and a nice REL subwoofer... Easy peasy...
My bad.. the question in there would have been if I've understood and summarized your and Ben's points correctly.. but you've answered that anyway.

Correct, I don't plan any speakers modifications and I'll stick to 2.1 (max 2.2).
Considering the different options I will indeed go what you're suggesting, @ddude003, as opposed to the DCX2496 approach, which I'm sure is great, too, just not my personal preference at the moment.


Finally... REW Measurements - Main Listening Position... For some reason the quote feature did not work, so I will be brief... I agree that file 277.5.mdat looks the best... With 1/6th smoothing it seems pretty flat and a little Roon DSP with a room curve should clean things up... Something else you might try is moving the Focals forward and backward a few inches... Just to see how things change... What is the distance of them from the front and side walls? Sorry, I know... With those footers it will be a pain and worth it... Have you tried toeing them in at all yet?
Thank you, that helps. Great suggestions.
Here's the sequence how I would tackle things.. can you let me know if you see any obvious flaws or if you'd suggest to tailor these steps differently?

Step 1: Loudspeaker Positioning
  • Front, back, left, right.. I'll move the speakers around and measure and listen and measure and listen. I may even move some of the furniture to try out different positions. I'm sure it will be worth it!
  • When I took the measurements toe-in was 13°.. the tweeter 29.1'' from the sidewall and 60.6'' from the wall behind it.
Step 2 Absorber and Bass Trap Adjustments
  • Step 2.a I will remove three absorbers that I believe are not critical at the moment. (Currently I have a total of 10 absorbers in the room).
    • Before having taken measurements (so basically until last week), I was wondering whether my room was overdamped (even if it did and does not sound so to me..maybe because I'm quite used to it), so I was wondering if removing three of the absorbers (and maybe replacing them with diffusors) would help fight the potential overdamping. These three would be the spare absorbers I'd use to create the stacked-absorber-bass-traps (with holes drilled in the back).

    • If measurements and listening don't show any ill effects resulting from removing the three absorbers, I'll proceed to Step 2.b
  • Step 2.b Use the three spare absorbers as absorbers-stacked-as-bass-trap-thingies and see if that helps bring the peaks at 124 Hz and 213 Hz down.
Step 3 Subwoofer
  • Measure nearfield
  • Measure sub alone and sub + Focals in many different places/positions in the room.
  • Get the sub's crossover and volume setting right
Step 4 DSP
  • First, I'll create REW PEQ filters myself and load them into Roon
  • Then, I'll play around with the house curve to see what I'd like best.
  • Lastly, I'll look into Convolution.
    • Until you've mentioned it last week I wasn't even aware, that something called Convolution exists; since then I've researched and gotten myself a first rudimentary overview. Right off the bat, I'd say that REW, waterfalls, decay charts, PEQ are all concepts I trust I'll enjoy to deal with ….but handling the various convolver tools like Acourate, AudioLense, etc seems like a totally different beast to me (at least when looking at the tools that run natively on a Mac, I believe). So, for Convolution I consider employing the services of Home Audio Fideltiy / HAF, which to me sounds like a great product and probably at a quality I'd hardly get to myself.
    • What do you think about HAF?
Later steps:
  • Get a new listening seat.. mine's not as comfy as I'd like it to be.
  • IsoAcoustic Gaia II isolator feet for the Focals
  • If at all "necessary" respectively desired.... think about a second sub.
Steps taken in parallel to all of the above steps:
  • Build and/or buy diffusors and see what they do
  • New listening seat.. mine's not as comfy as I'd like it to be.. dreaming of an Eames lounge chair replica.

Hope my posts don't exceed any limits.. I know they're long.
I welcome any feedback, suggestions, and comments very much!

Thank y'all,
Martin
 

BenToronto

Member
Joined
May 22, 2017
Messages
92
Whatever you do and whatever automated EQ you try, you'll always need to fine-tune when you are at the quasi-end. Fine-tuning shouldn't be done by ear alone because that will lead to a big mess. Re-tuning begins with running REW to establish a bench-mark. Which then requires either tossing out the automated EQ or fiddling with its "black box" output; and either of which requires a DCX2496 to re-tune.

If you are allergic to DSP, the CX3400 is a swell analog electronic XO which measures perfect. Just like the DCX2496.

Ethan Winer has written knowledgeably about bass traps (that he sells) and using REW - esp to get RT (reverb time) looking good.

B.
 

Martin1703

Member
Thread Starter
Joined
Jul 6, 2022
Messages
19
My AV System  
Preamp, Processor or Receiver
Musical Fidelity M8s-PRE
Main Amp
Musical Fideltiy M8s-500s
Computer Audio
MacBook
DAC
Denafrips Pontus II
Front Speakers
Focal Kanta 2
Subwoofers
REL S/510
Streaming Equipment
Roon Nucleus+
Streaming Subscriptions
Quobuz
Whatever you do and whatever automated EQ you try, you'll always need to fine-tune when you are at the quasi-end. Fine-tuning shouldn't be done by ear alone because that will lead to a big mess. Re-tuning begins with running REW to establish a bench-mark. Which then requires either tossing out the automated EQ or fiddling with its "black box" output; and either of which requires a DCX2496 to re-tune.

If you are allergic to DSP, the CX3400 is a swell analog electronic XO which measures perfect. Just like the DCX2496.

Ethan Winer has written knowledgeably about bass traps (that he sells) and using REW - esp to get RT (reverb time) looking good.

B.
Hey Ben,
Thank you. these are good points, much agree with them.

However, the Roon Nucleus+ I have in my chain does allow me to load parametric EQ and convolution filters (as ddude003 has rightly pointed out to me).
For PEQ I can use REW to create the filters and upload them into Roon myself. I can do that iteratively as long and often as I like.
For Convolution I'd still start with REW (or something similar) but hand over the measurements to HAF who'd create the convolution filter for me. The initial filter they create is a little more costly (109 to 159 USD for what I'm looking at) and subsequent iterations 29 to 39 USD.

So in both cases I can keep on fine-tuing when I'm at my quasi-end.. or am I missing something?

One advantage the DCX2496 would have is that I can apply the cross over to each channel individually, so, also to the full-range speakers.
With Roon/Nucleus I can't do that, but that's the only downside I see so far.

Well, the proof of the pudding is in the eating.. so I'll try things out one way.. and later probably the other way. :)

Thanks also about the tipp regarding Ethan Winer, bass traps and REW.. I definitely need to read that.
When looking at the attached file .. which RT problem would you suggest I start looking at first?

Martin
 

Attachments

BenToronto

Member
Joined
May 22, 2017
Messages
92
Your freq plot looks pretty flat north of maybe 35. But to have satisfying bass, it really needs to be booster below maybe 70 Hz (and I certainly am talking about "classical music" (whatever that means today), not pop garbage.

From my own POV, your RT seems over damped for a music room and esp in the bass. Which may make your bass seem blah. But didn't you post here thinking the bass was to boomy??? Some inconsistency there?

Attached are RTs for my L and R channels added to yours (which is the lowest one). I think mine are about right for music but not achieved through any smart design on my part, as much as I'd like to claim so.

There's a button on REW that creates nice jpegs of the plots.

B.
 

Attachments

ddude003

Senior Member
Joined
Aug 13, 2017
Messages
858
Location
Somewhere Northeast of Kansas City Missouri
My AV System  
Preamp, Processor or Receiver
PrimaLuna Dialogue Premium TubePre (2 channel+sub)
Main Amp
McIntosh MC152 SS Amp (2 channel)
Additional Amp
Yamaha RX-A850 Pro (the other 5 channels lol)
Computer Audio
MacBook Pro, Custom i7 7700k De-lid 2xAsus1080ti GFX build, Audirvana+, LiquidSonics, SoX
DAC
Chord Electronics Ltd. Qutest
Universal / Blu-ray / CD Player
Sony UBP-X700 /M Ultra HD 4K HDR
Front Speakers
Martin Logan ElectroMotion ESL
Center Channel Speaker
Martin Logan Motion C2
Surround Speakers
Martin Logan Motion 4
Surround Back Speakers
Martin Logan Motion 4 (yes, another set of these)
Subwoofers
Martin Logan Dynamo 700
Other Speakers or Equipment
Cifte 12AU7 NOS & Genalex Gold Lion Tubes in Pre
Video Display Device
Samsung The Premiere LSP7T UST Laser Projector
Screen
Elite Screens Aeon CLR3 0.8 Gain 103-inch
Remote Control
PrimaLuna & Lumin iApp
Streaming Equipment
Lumin U1 Mini Streamer/Transport
Streaming Subscriptions
Roon & QoBuz Studio Premier, Amazon Prime & Netflix
Other Equipment
ThrowRug, SaddleBlankets, WideBand & BaseTraps...
Hi @Martin1703... It seems to me that you are heading in the right direction... You should be able to handle Roon parametric EQ easily... And there are several free tools to get from REW to Roon Impulse Response files for the Roon Convolution engine... And if you want to eq L and R speakers separately you create a two channel IR file... I think it is important to get you in the ballpark with your room, speaker placement and listening position before worrying too much about the types of eq and crossover designs... There a bunch of speaker management hardware and software systems out there to choose from... Take you time researching them to insure they match your long term system goals, connectivity and ease of use...

I saw you may be looking into diffusers... http://arqen.com/sound-diffusers/ may be of interest... The rest of website has a lot of information you may be interested in also... House curve research by Bruel & Kjaer https://www.bksv.com/media/doc/17-197.pdf See figure 5 on page 4...
 
Last edited:

Martin1703

Member
Thread Starter
Joined
Jul 6, 2022
Messages
19
My AV System  
Preamp, Processor or Receiver
Musical Fidelity M8s-PRE
Main Amp
Musical Fideltiy M8s-500s
Computer Audio
MacBook
DAC
Denafrips Pontus II
Front Speakers
Focal Kanta 2
Subwoofers
REL S/510
Streaming Equipment
Roon Nucleus+
Streaming Subscriptions
Quobuz
Your freq plot looks pretty flat north of maybe 35. But to have satisfying bass, it really needs to be booster below maybe 70 Hz (and I certainly am talking about "classical music" (whatever that means today), not pop garbage.

From my own POV, your RT seems over damped for a music room and esp in the bass. Which may make your bass seem blah. But didn't you post here thinking the bass was to boomy??? Some inconsistency there?

Attached are RTs for my L and R channels added to yours (which is the lowest one). I think mine are about right for music but not achieved through any smart design on my part, as much as I'd like to claim so.

There's a button on REW that creates nice jpegs of the plots.

B.
Hey Ben,
I haven't had the subwoofer on when taking the measurements.. so that'll hopefully add some of the boost you're describing.

Regarding the potential inconsistencies:
- Based on what I've read before I've joined this forum and before I took measurements, I was wondering whether it is overdamped, even if—to me—it didn't sound so.
- At my original listening position the bass was boomy.. but after having taken dozens of measurements from different listening positions I've found a nice spot where the bass isn't boomy.
So the inconsistency comes from my two statements having been made at different points in time (and relative to different listening positions).

I plan to take actions to increase RT a little bit by reducing the number of absorbers, maybe replacing others with diffusors, add scatterplates to the remaining diffusors, removing the carpet.. and see which of these actions have effect measured RT and perceived sound quality positively.. and which don't.

Best Regards,
Martin
 

Martin1703

Member
Thread Starter
Joined
Jul 6, 2022
Messages
19
My AV System  
Preamp, Processor or Receiver
Musical Fidelity M8s-PRE
Main Amp
Musical Fideltiy M8s-500s
Computer Audio
MacBook
DAC
Denafrips Pontus II
Front Speakers
Focal Kanta 2
Subwoofers
REL S/510
Streaming Equipment
Roon Nucleus+
Streaming Subscriptions
Quobuz
Hi @Martin1703... It seems to me that you are heading in the right direction... You should be able to handle Roon parametric EQ easily... And there are several free tools to get from REW to Roon Impulse Response files for the Roon Convolution engine... And if you want to eq L and R speakers separately you create a two channel IR file... I think it is important to get you in the ballpark with your room, speaker placement and listening position before worrying too much about the types of eq and crossover designs... There a bunch of speaker management hardware and software systems out there to choose from... Take you time researching them to insure they match your long term system goals, connectivity and ease of use...

I saw you may be looking into diffusers... http://arqen.com/sound-diffusers/ may be of interest... The rest of website has a lot of information you may be interested in also... House curve research by Bruel & Kjaer https://www.bksv.com/media/doc/17-197.pdf See figure 5 on page 4...
Hi ddude003,
Yes, I'll just continue on my journey and not worry too much about how to create the Convolution filters before I get to that point.
What I meant was only that — and this is purely (and maybe poorly as well) based on internet research — while REW can create convolution filters it doesn't exploit the phase related Convolution possibilities as much as Acourate, Audiolense, or HAF are able to. Anyhow.. I'll cross that bridge when I get there.

Thanks a lot for the link to B&K article and to the Arqen website which contains great information about diffusors. I can't download the free blueprints/designs, though. An error message says, "Mailing List Not Active". :sad:
Also, when asked whether I would like a free Email Mini-Course on"How to Build Diffusers and Treat Your Room" the same thing happens.
Is it the same for you?

Best Regards,
Martin
 

BenToronto

Member
Joined
May 22, 2017
Messages
92
...

I plan to take actions to increase RT a little bit by reducing the number of absorbers, maybe replacing others with diffusors, add scatterplates to the remaining diffusors, removing the carpet.. and see which of these actions have effect measured RT and perceived sound quality positively.. and which don't.

Best Regards,
Martin
Don't recall ever hearing anybody benefit from adding diffusers in a living room. Likewise, maybe all your add-on absorbers are a bit too much, but again, never heard anybody say they needed less absorbing in their living room.

The contradiction may lie in having one or two prominent bumps or close together or 50-90 Hz or in one particular location. REW should answer that.

I remain ignorant of what speakers get what signals and when you are measuring what and what not. Maybe I have been wasting ink pondering plots of dunno what. I have a feeling you are playing an unholy mush of crossed-over and not-crossed-over speakers. Mush can work if you are real lucky. For the rest of go bi-amped and use bands 3 octaves wide, and use sharp XO slopes.
 

ddude003

Senior Member
Joined
Aug 13, 2017
Messages
858
Location
Somewhere Northeast of Kansas City Missouri
My AV System  
Preamp, Processor or Receiver
PrimaLuna Dialogue Premium TubePre (2 channel+sub)
Main Amp
McIntosh MC152 SS Amp (2 channel)
Additional Amp
Yamaha RX-A850 Pro (the other 5 channels lol)
Computer Audio
MacBook Pro, Custom i7 7700k De-lid 2xAsus1080ti GFX build, Audirvana+, LiquidSonics, SoX
DAC
Chord Electronics Ltd. Qutest
Universal / Blu-ray / CD Player
Sony UBP-X700 /M Ultra HD 4K HDR
Front Speakers
Martin Logan ElectroMotion ESL
Center Channel Speaker
Martin Logan Motion C2
Surround Speakers
Martin Logan Motion 4
Surround Back Speakers
Martin Logan Motion 4 (yes, another set of these)
Subwoofers
Martin Logan Dynamo 700
Other Speakers or Equipment
Cifte 12AU7 NOS & Genalex Gold Lion Tubes in Pre
Video Display Device
Samsung The Premiere LSP7T UST Laser Projector
Screen
Elite Screens Aeon CLR3 0.8 Gain 103-inch
Remote Control
PrimaLuna & Lumin iApp
Streaming Equipment
Lumin U1 Mini Streamer/Transport
Streaming Subscriptions
Roon & QoBuz Studio Premier, Amazon Prime & Netflix
Other Equipment
ThrowRug, SaddleBlankets, WideBand & BaseTraps...
Hello @Martin1703, Sonnie, one of the guys here at AV NIRVANA, has a thread about building these Fractal Diffusers... https://www.avnirvana.com/threads/custom-diy-diffuser-panels.8367/... Sorry the Argen link did not work for you... There is also Tim's thesis at http://arqen.com/wp-content/docs/Acoustic-Diffuser-Optimization-Arqen.pdf... Or try this http://arqen.com/wp-content/docs/diffusers/Diffuser-A1LF-Fab-Drawings-Arqen.pdf... Between those sources you should be able to figure out if a fractal diffuser is for you... As with absorbers, there are many diffuser designs...

There are free tools like rePhase at https://rephase.org that will pick up where REW leaves off... Your preference, as always, is where you should be heading...
 
Last edited:

jean38

Registered
Joined
Apr 18, 2021
Messages
2
My AV System  
Preamp, Processor or Receiver
CAMBRIDGE 751
Computer Audio
NVIDIASHIELD 2019
DAC
CA
Front Speakers
ORAN 4305
Center Channel Speaker
ORAN 430C
Surround Speakers
DILIS 4205
Subwoofers
DORD 265
Video Display Device
SAMSUNG 75
Remote Control
HARMONY ELITE
Other Equipment
HD FURY INTEGRAL 2
T
53658
he mistake many people make of thinking that absorption is enough. it is necessary to think of positioning diffusers close to the zone of listening, and, between the sources. It is necessary to analyze the result is with REW by using the analysis of the wavelets.
 

jean38

Registered
Joined
Apr 18, 2021
Messages
2
My AV System  
Preamp, Processor or Receiver
CAMBRIDGE 751
Computer Audio
NVIDIASHIELD 2019
DAC
CA
Front Speakers
ORAN 4305
Center Channel Speaker
ORAN 430C
Surround Speakers
DILIS 4205
Subwoofers
DORD 265
Video Display Device
SAMSUNG 75
Remote Control
HARMONY ELITE
Other Equipment
HD FURY INTEGRAL 2
the mistake many people make of thinking that absorption is enough. it is necessary to think of positioning diffusers close to the zone of listening, and, between the sources. It is necessary to analyze the result is with REW by using the analysis of the wavelets.
53659
 

Martin1703

Member
Thread Starter
Joined
Jul 6, 2022
Messages
19
My AV System  
Preamp, Processor or Receiver
Musical Fidelity M8s-PRE
Main Amp
Musical Fideltiy M8s-500s
Computer Audio
MacBook
DAC
Denafrips Pontus II
Front Speakers
Focal Kanta 2
Subwoofers
REL S/510
Streaming Equipment
Roon Nucleus+
Streaming Subscriptions
Quobuz
Hi DDude.. sorry for a late reply.. I've been away from home and my listening room for a few weeks and won't be back for another few weeks.
Thanks for the links you've shared.. they all work fine and provide excellent information.

Hi Jean38.. thanks for the input.. I definitely plan to add diffusors.. just need to start experimenting with it..

Cheers,
Martin
 

Martin1703

Member
Thread Starter
Joined
Jul 6, 2022
Messages
19
My AV System  
Preamp, Processor or Receiver
Musical Fidelity M8s-PRE
Main Amp
Musical Fideltiy M8s-500s
Computer Audio
MacBook
DAC
Denafrips Pontus II
Front Speakers
Focal Kanta 2
Subwoofers
REL S/510
Streaming Equipment
Roon Nucleus+
Streaming Subscriptions
Quobuz
Question regarding the fractal diffuser described here: http://arqen.com/wp-content/docs/diffusers/Diffuser-A1LF-Fab-Drawings-Arqen.pdf
Is there a way to figure out the minimum distance there needs to be between the diffuser and the MLP?

My best guess is that I'm safe to use this design at the front and back wall (each about 8.5' from the MLP) but probably not so much of an option for the side walls (each about 5' 22'' from the MLP) and the ceiling, would you agree?
 

ddude003

Senior Member
Joined
Aug 13, 2017
Messages
858
Location
Somewhere Northeast of Kansas City Missouri
My AV System  
Preamp, Processor or Receiver
PrimaLuna Dialogue Premium TubePre (2 channel+sub)
Main Amp
McIntosh MC152 SS Amp (2 channel)
Additional Amp
Yamaha RX-A850 Pro (the other 5 channels lol)
Computer Audio
MacBook Pro, Custom i7 7700k De-lid 2xAsus1080ti GFX build, Audirvana+, LiquidSonics, SoX
DAC
Chord Electronics Ltd. Qutest
Universal / Blu-ray / CD Player
Sony UBP-X700 /M Ultra HD 4K HDR
Front Speakers
Martin Logan ElectroMotion ESL
Center Channel Speaker
Martin Logan Motion C2
Surround Speakers
Martin Logan Motion 4
Surround Back Speakers
Martin Logan Motion 4 (yes, another set of these)
Subwoofers
Martin Logan Dynamo 700
Other Speakers or Equipment
Cifte 12AU7 NOS & Genalex Gold Lion Tubes in Pre
Video Display Device
Samsung The Premiere LSP7T UST Laser Projector
Screen
Elite Screens Aeon CLR3 0.8 Gain 103-inch
Remote Control
PrimaLuna & Lumin iApp
Streaming Equipment
Lumin U1 Mini Streamer/Transport
Streaming Subscriptions
Roon & QoBuz Studio Premier, Amazon Prime & Netflix
Other Equipment
ThrowRug, SaddleBlankets, WideBand & BaseTraps...
Question regarding the fractal diffuser described here: http://arqen.com/wp-content/docs/diffusers/Diffuser-A1LF-Fab-Drawings-Arqen.pdf
Is there a way to figure out the minimum distance there needs to be between the diffuser and the MLP?

My best guess is that I'm safe to use this design at the front and back wall (each about 8.5' from the MLP) but probably not so much of an option for the side walls (each about 5' 22'' from the MLP) and the ceiling, would you agree?
No worries @Martin1703... http://arqen.com/sound-diffusers/faq/#listening-distance... Your in the ballpark for the distance from front and rear walls to the MPL... Front and rear walls are best for diffusion... You really want wide band absorption on your side walls first refection points... The timing of the sound from the first reflection points confuses the ear/brain...
 
Last edited:
Top Bottom