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Quest for Real Bass Traps

Curvature

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Do any acoustic treatment companies offer practical bass traps? By practical I mean this list here.
  • Clear effectiveness below 200Hz and a reasonable amount below 100Hz.
  • Clear testing method and availability of results.
  • Only a few inches deep to keep them suitable for domestic settings. This excludes electronic versions since they are the size of subwoofers and tube traps, unless you happen to like those in the corners of your room.
  • No DIY for the lazy of us, and those with no tools or space to build.
  • No broadband absorption. Enough of that as it is.
  • Ability to buy a few panels at a time for the living room or bedroom.
  • Excellent build quality.
Options:
  • RPG: Impeccable reputation. This is primarily a professional company which deals with commercial installations, studios or the odd large home theater. It's no surprise then that they have high order minimums which leave the regular consumer out of luck. Despite that I'll include these options for those who can pull those minimum together:
    • Modex LF: 5.125" depth.
    • Modex Module: 5" and 7" deep versions.
    • Modex Plate: 6" depth.
    • Modsorber: The ideal tool. 1", 2", 3" and 4" depths. 100sqft order minimum.
    • A few other products are interesting, like the Dado and Perfecto series.
  • GIK: Build quality is mediocre. Despite that they understand acoustics and offer a bunch of membrane based traps along with the usual broadband or corner contraptions.
    • Scopus T100: Tuned to 100Hz, with a depth of 4.25". Should be known that the absorption bandwidth is very narrow.
    • Scopus T70: 70Hz, 4.25".
    • Scopus T40: 40Hz, 10.25".
    • 244: FlexRange option, 5.25" depth.
    • Monster: FlexRange, 7.3".

Exclusions:
 

sam_adams

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There's no such thing as a 'practical' bass trap. Velocity-based absorbers (foam or insulation batts) have to be at least one third of a wavelength thick at the frequency of interest to damp the wave. At 200 Hz, that's 22 inches thick.

Pressure-based absorbers can be thinner, but they require a damping medium in the panel (foam or insulation batts) to work correctly. Additionally, you would need to select a range of frequencies, sizes, and locations of the panels in the room to effectively 'damp' the frequencies of interest. You would also have to consider seriously modifying the walls of your room to make them work effectively—think cutting out large sections of drywall.

Rooms that are not designed from the start with bass control in mind will perform poorly. Research into the work of both Tom Hidley and Bogic Petrovic will give some insight into how to design a room from the ground up with bass control in mind. Use the Google to research Tim's limp mass bass traps (unfortunately DIY) for the challenge of implementing mass-loaded, pressure-based absorbers.
 

FeddyLost

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Just to mention downsides.

1) RPG Modex is very heavy and expensive.

2) Pressure based absorbers can be thinner in theory, but as DIYers say, light membrane+deep box is much better than heavy membrane+shallow box.
So, any effective limp membrane absorber tuned for really low bass will be thick.

2.5) And PBAs must cover significant part of complementary wall, not few boxes here and there.
 

Purité Audio

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I use the Modex here, they are heavy but only 5” deep, they work but you need a lot of them. Easier to EQ.
Keith
 

abdo123

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the only solution i know off that satisfies your conditions is the broadsorber. The 4 inch version has balanced broadband absorption from 100Hz and up.

 

Bjorn

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I can show some measurements of RPG products used in rooms.

First with the use of Broadsorbor panels on rear side walls.

Frequency response before treatment:

Frekvensrespons før og uten sidetiltak.jpg


Added two Broadsorbor panels with dimension 120x80x10.4 cm, placed on each side wall behind each speaker. Notice the reduction of the 120 Hz dip

Frekvensrespons med to stk Broads 120x80x10cm.jpg


With two larger panels with dimension 150x80x10.4 cm, the result is better.
Frekvensrespons med to stk Broads 150x80x10cm.jpg


And here is with four panels with dimension 150x80x10.4 cm. All placed on side walls behind the speakers. Some diffusers were move, which causes a slight dip at 33 Hz FIY.

Frekvensrespons med fire stk Broads 150x80x10cm.jpg


Waterfall before treatment:
Vannfall før og uten sidetiltak.jpg


Waterfall with four panels:
Vannfall med fire stk Broads 150x80x10cm.jpg
 

Bjorn

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Modex plate exist in different options. In Europe there are two kinds. Neither of these are offered in the USA anymore. While they are expensive, they cost much less than the Modex plate offered in the USA. They are also only about 10-11 cm thick (4").

Here we can see the difference in performance between these two below 100 Hz.
Modex plate 1 and 2_T_Room_Chart.gif


These have changed some over the years. The most recent one, weighs at least 10 kg less than the previous one and is suppose to give a more consisted result. I have not had the option of comparing the former to the new kind yet.

Below is a measurement with two Modex plate type 1 in a room. The primarily goal was to reduce a resonance areound 70 Hz.

Before at ear height:
before (1).jpg


After with one Modex plate on each rear side wall.
after (1).jpg


The 70 Hz resonance was effectively reduced. The 85 Hz null was also reduced along with some other smaller improvements.


The Modex plate sold in the USA is 6" thick and cost considerably more. It's also smaller in lenght x width. Here's the absorption data of it.
Modex plate USA type.jpg



In a certain room, there was a problem with a frequency ringing at 140 Hz and was very evident. Someone mentioned here that EQ is easier. In this case the following was reported: "Equalization is an obvious first-try solution, but the required deep filter created a subjective impression of “something missing that should be there, and something there that shouldn’t be.” It just sounded bad. "

Instead two "USA" Modex plates were installed on the front wall.

Workstation-with-panels-1500x1125 (Liten).png


Measurement before looked like this (3D waterfall):
Waterfall before.jpg


And after:
Waterfall after_2 units.jpg


The 140 Hz ringing was solved and without the drawback of equalization.
 

FrantzM

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Hi

I am following the discussion with interest. I have a dedicated room, albeit small. I could play with the concept but... In many of the examples shown, it looks to me that some of the issues could have been solved or mitigated with a bit of EQ.. Am I mistaken? In term of real cost and efficacy EQ in those specific examples seemed to be the more sensible option...
I have come to think that Bass traps are, based on physics, perforce "unpractical" due to their large size. Even the notion of designing a room for good bass is , IMO, a challenge for professional, let alone the average audiophiles. The better solutions seem to rely on electronics (DSP/EQ/DRC) and/or multiple subwoofers...
Feel free to ignore me completely if this is off topics...

Peace.
 

FeddyLost

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In this case the following was reported: "Equalization is an obvious first-try solution, but the required deep filter created a subjective impression of “something missing that should be there, and something there that shouldn’t be.” It just sounded bad. "
Post-echo without echo source.
Strong EQ make a notch in "anechoic responce" and room fills it with ringing ...
I think it might sound weird for customers familiar with original sound of instruments.
 

goat76

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Hi

I am following the discussion with interest. I have a dedicated room, albeit small. I could play with the concept but... In many of the examples shown, it looks to me that some of the issues could have been solved or mitigated with a bit of EQ.. Am I mistaken? In term of real cost and efficacy EQ in those specific examples seemed to be the more sensible option...
I have come to think that Bass traps are, based on physics, perforce "unpractical" due to their large size. Even the notion of designing a room for good bass is , IMO, a challenge for professional, let alone the average audiophiles. The better solutions seem to rely on electronics (DSP/EQ/DRC) and/or multiple subwoofers...
Feel free to ignore me completely if this is off topics...

Peace.
Solving the room problems with acoustic treatment is much better than using EQ. EQ is just a two-dimensional tool trying to solve a three-dimensional problem. With acoustic treatment you get better control over the time aspects of the room problems.
 

Bjorn

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Hi

I am following the discussion with interest. I have a dedicated room, albeit small. I could play with the concept but... In many of the examples shown, it looks to me that some of the issues could have been solved or mitigated with a bit of EQ.. Am I mistaken? In term of real cost and efficacy EQ in those specific examples seemed to be the more sensible option...
I have come to think that Bass traps are, based on physics, perforce "unpractical" due to their large size. Even the notion of designing a room for good bass is , IMO, a challenge for professional, let alone the average audiophiles. The better solutions seem to rely on electronics (DSP/EQ/DRC) and/or multiple subwoofers...
Feel free to ignore me completely if this is off topics...

Peace.
Acoustic treatment is for those who want high quality. EQ alone is a big compomise. The multiple subwoofer approach only operates in a narrow frequency area and not in the most audible region. Besides, use of multiple subwoofers generally has it's own drawbacks. A subwoofer (or several stacked) only in the front with even response and great time domain behaviour is the very best solution.

Obviously we make compromises and those differ. For many, the most viable solution is using a combination of several approcahes. For example: Going after a strong 30-35 Hz resonance and peak with treatment is seldom practical or economical. Here some equalization could be used, while focusing on treatment for higher frequencies.
 
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Inner Space

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Solving the room problems with acoustic treatment is much better than using EQ. EQ is just a two-dimensional tool trying to solve a three-dimensional problem. With acoustic treatment you get better control over the time aspects of the room problems.
I agree. In particular, fixing room modes with EQ might look OK via a microphone, but it's musically dumb. Room modes are not acoustic amplifications of the signal. They are big, dumb, harmonically empty hoots triggered by the signal. Dropping the signal down into inaudibility merely leaves a smaller dumb harmonically empty hoot, which superficially looks like a smoother curve, but which sounds ridiculous - a bass line that should go note, note, note, note will sound note, hoot, note, hoot. Not satisfactory at all.

The problem is that effective acoustic treatment is fantastically huge and very expensive. I just did a room for a (fortunately rich) person, involving nearly 100 24" tube traps. It sounds absolutely wonderful (and looks surprisingly good) but is obviously a niche solution for an extreme minority.
 

FrantzM

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Solving the room problems with acoustic treatment is much better than using EQ. EQ is just a two-dimensional tool trying to solve a three-dimensional problem. With acoustic treatment you get better control over the time aspects of the room problems.

Acoustic treatment is for those who want high quality. EQ alone is a big compomise. The multiple subwoofer approach only operates in a narrow frequency area and not in the most audible region. Besides, use of multiple subwoofers generally has it's own drawbacks. A subwoofer (or several stacked) only in the front with even response and great time domain behaviour is the very best solution.

Obviously we make compromises and those differ. For many, the most viable solution is using a combination of several approcahes. For example: Going after a strong 30-35 Hz resonance and peak with treatment is seldom practical or economical. Here some equalization could be used, while focusing on treatment on higher frequencies.
O.T.

FWIW, I disagree with your points. Perhaps .. I should open a thread on the subject of DRC/EQ vs Room Treatments .... ;)
What do you all think?
I agree. In particular, fixing room modes with EQ might look OK via a microphone, but it's musically dumb. Room modes are not acoustic amplifications of the signal. They are big, dumb, harmonically empty hoots triggered by the signal. Dropping the signal down into inaudibility merely leaves a smaller dumb harmonically empty hoot, which superficially looks like a smoother curve, but which sounds ridiculous - a bass line that should go note, note, note, note will sound note, hoot, note, hoot. Not satisfactory at all.

The problem is that effective acoustic treatment is fantastically huge and very expensive. I just did a room for a (fortunately rich) person, involving nearly 100 24" tube traps. It sounds absolutely wonderful (and looks surprisingly good) but is obviously a niche solution for an extreme minority.
This again would require elaborate reply... It is all wrong. What do you mean by "musically wrong"? Seriously , music is a succession of acoustic signals, that you manage to hear in your home because, they were picked-up by microphones... So what you hear is also picked-up and more accurately , some would say "dispassionately", by, you guessed it: microphones.

Mods? Moderators? :) What do you suggest? A new thread?


Peace.
 

Bjorn

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Yes, I think you start a new thread. It's off-topic here. Anyone who understands time domain behaviour and its importance don't need to discuss it either.
 

Inner Space

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This again would require elaborate reply... It is all wrong. What do you mean by "musically wrong"? Seriously , music is a succession of acoustic signals ...
No, music is a succession of pitches and timbres. If timbres are replaced by anharmonic sines caused by resonances of air contained by rooms, then music is corrupted, even though UMIKs and REW might give you a smooth graph. That was my point.
 

FrantzM

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No, music is a succession of pitches and timbres. If timbres are replaced by anharmonic sines caused by resonances of air contained by rooms, then music is corrupted, even though UMIKs and REW might give you a smooth graph. That was my point.
I am getting lost in your semantic. According to Wikipedia:
Pitch is a perceptual property of sounds that allows their ordering on a frequency-related scale
Frequency is an acoustic property of sound. It is measurable...
And what do you mean by "anharmonic sines"? How are "timbres" replaced by anharmonic sines???

I am lost care to rephrase/explain it.

Peace.
 

Morla

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Nobody mentioned PSI AVAA, yet? I'm still thinking of buying those but.. so expensive
 

Inner Space

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And what do you mean by "anharmonic sines"? How are "timbres" replaced by anharmonic sines???
Try re-reading this part of my earlier post:
Room modes are not acoustic amplifications of the signal. They are big, dumb, harmonically empty hoots triggered by the signal.
Thus harmonically complex musical notes are overwhelmed by modes, which are harmonically bereft plain sine waves. EQing drops the harmonically complex notes into inaudibility, leaving only quieter harmonically bereft sines in the audible realm. Thus:
... a bass line that should go note, note, note, note will sound note, hoot, note, hoot.
My point is that note, hoot, note, hoot might look smooth on REW, but is musically ridiculous. Is that clearer?
 
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