Page 1 of 3 123 LastLast
Results 1 to 10 of 23

Thread: Why do many Acousticians recommend absorption for non-bass freq: Valid OR prefer dead room & Dogma?

  1. #1

    Why do many Acousticians recommend absorption for non-bass freq: Valid OR prefer dead room & Dogma?

    Why do so many acousticians recommend absorption for everything in the room, vs. just using absorption for the bass portion of the space?

    Are guys just unquestioningly going back to some research paper someone wrote a century ago? Have acousticians become accustomed to dead sounding spaces and everything else sounds wrong? Or are there valid reasons?

  2. #2
    Senior Member BobM's Avatar
    Join Date
    Feb 2014
    Location
    Long Island, NY
    Posts
    160
    there are a ton of theories on how to set up acoustic treatments, from live end - dead end, to dead room, to deflect everything, etc. You just have to do some more research and try things until something works for you.

    In my experience, with typical cone speakers, I found dead end at the speaker side and live (reflective/deflective) end at the listening side works best, with some absorption at the first reflection point.

    With panel speakers I've found the exact opposite to sound better.

    With horns you might want more dead than reflective.

    Good luck and enjoy the ride.
    Veni, Vide, Velcro - I came, I saw, I stuck around.

  3. #3
    Member Sponsor [VIP/Donor]
    Join Date
    Sep 2013
    Location
    Greater Boston
    Posts
    3,834
    Quote Originally Posted by BobM View Post
    In my experience, with typical cone speakers, I found dead end at the speaker side and live (reflective/deflective) end at the listening side works best, with some absorption at the first reflection point.
    + 1

    I had to deaden the substantial space behind the speakers up to the front wall quite a bit (my speakers are 7 feet out into the room), and liven up the space around and behind the listening position. The former was needed to bring too recessed images more forward, the latter to liven up in particular the treble. Now I have the, for my tastes, perfect balance for imaging: lots of spatial depth for orchestral and other music that benefits from it, but also very intimate, more forward imaging for a lot of small scale stuff which, however, still allows for appropriate spatial layering towards the back of the stage. Treble is not quite as extended as it could be if I'd remove the carpet stretching from the speakers to the front wall, in the dead end of the room, but this is a minor sacrifice to be made for getting the imaging optimal, which translates into more listener involvement.

    An image of the front end (dead end) of my room can be seen on this page:

    http://www.whatsbestforum.com/showth...r-system/page9

    Not quite up to date in terms of system, but the acoustic configuration is the current one.

  4. #4
    VIP/Donor [VIP/Donor] microstrip's Avatar
    Join Date
    May 2010
    Location
    Portugal
    Posts
    13,813
    Quote Originally Posted by caesar View Post
    Why do so many acousticians recommend absorption for everything in the room, vs. just using absorption for the bass portion of the space?
    (...)
    Most probably because it is much easier to do, absorption in the bass needs a lot of work, space and more money. Curiously it seems that absorption in the bass is what is more needed in most rooms.
    DCS Vivaldi 2.0 stack, Metronome Kalista / Kondo KSL DAC, Soundlab A1 Px's , EMT927, SME3012R, ARC Phono 3, ARC REF40, VTL Siegfried II, TA Opus MM2 speaker and signal, TA XL digital, TA XL gen V power cables, CenterStage footers and Nordost Qkore8's!

  5. #5
    [WBF Founding Member] Addicted to Best! JackD201's Avatar
    Join Date
    Apr 2010
    Location
    Manila, Philippines
    Posts
    10,958
    Quote Originally Posted by caesar View Post
    Why do so many acousticians recommend absorption for everything in the room, vs. just using absorption for the bass portion of the space?

    Are guys just unquestioningly going back to some research paper someone wrote a century ago? Have acousticians become accustomed to dead sounding spaces and everything else sounds wrong? Or are there valid reasons?
    Good acousticians don't make dead rooms unless that is what is needed. The only uses I can think of are isolation booths and anechoic chambers. Design should be done to suit purpose and in our case as non-professional listeners, preference. To get that preferred sound the basics are to achieve a desired reverberation time curve across the spectrum while dealing with damaging peaks and troughs whether at one spot or across a larger area. It then becomes a game of surface coverage area vs frequency and geometry. A bare space will have its own baseline parameters based on volume, shape and boundary construction which can be altered in many ways. It should be noted that objects in the room including the people in it, not just the walls have absorptive coefficients. Many forget that diffusers absorb as well. The math is straightforward but it can be very tedious because as I said, everything in the room needs to be accounted for. Then there is the proper construction and placement of the treatments ASIDE from the normal stuff, furniture, artwork, shelves, drapes, rugs, what have you.

    IMO if an "acoustician" does a dead room where that is not what is specified, he hasn't done the math and you need a refund. While I suppose many clients just say "build me a room that sounds good", a real acoustician would at least make some efforts to communicate with the client and somehow figure out what "good" means to that client. Otherwise, beware.
    Disclosure of Industry Participation

    Co-Founder and Managing Director PureSound PH - Exclusive Distributor (Philippines only) of Lamm, Von Schweikert Audio, CH Precision, Light Harmonic, Valvet, Townshend, Critical Mass Systems, EERA, KR Audio, Ambience SS, TechDAS, Master Built, Stromtank

  6. #6
    Member Sponsor [VIP/Donor] GaryProtein's Avatar
    Join Date
    Jul 2012
    Location
    NY
    Posts
    2,553
    Quote Originally Posted by BobM View Post
    there are a ton of theories on how to set up acoustic treatments, from live end - dead end, to dead room, to deflect everything, etc. You just have to do some more research and try things until something works for you.

    In my experience, with typical cone speakers, I found dead end at the speaker side and live (reflective/deflective) end at the listening side works best, with some absorption at the first reflection point.

    With panel speakers I've found the exact opposite to sound better.

    With horns you might want more dead than reflective.

    Good luck and enjoy the ride.
    I found basically the same thing.
    Listening Room: McIntosh C46, MCD500, MR78, MPI4, MC602 (2), Accuphase DG58, Pass Labs XVR1 (three-way), tri-amplified Infinity IRS Series V, TailTwister T2X rotator, AtlasSound FMA Rack, dedicated electrical sub-panel, boarded up fireplace, NO TV!

    Living Room: McIntosh C28, MC2300, MEN220, Revox B226, Tascam CD355, Thorens TD125 MKII w/vacuum platter, Rabco SL-8E, Grace F9-Ruby, McIntosh ML-2C (2) & ML-1C (4) stacked, MQ-107, SAE 2800, Nakamichi Dragon, Tandberg 64X, JL Audio f113 (2)

  7. #7
    Site Founder And Administrator Ron Resnick's Avatar
    Join Date
    Jan 2015
    Location
    Beverly Hills, CA
    Posts
    4,863
    Quote Originally Posted by BobM View Post
    . . .

    With panel speakers I've found [live at the speaker side, absorption at the listener side] to sound better.

    . . .
    An oversimplification but I largely agree with this.
    Mono and Stereo - Senior Contributing Reviewer

    turntable: American Sound AS-2000; tonearms: SME 3012R, Schröder LT; cartridges: ZYX UNIverse Premium X-SB2, Air Tight Opus-1; tape: Studer A820 Mk II; phono stage: Aesthetix Io Eclipse; line stage: VTL TL-7.5 Series III; amplifier: VTL Siegfried Series II; loudspeaker: Gryphon Pendragon; cables: MasterBuilt Ultra; stands: Vintage Audio Nothing racks, Herzan TS-140/Taiko Tana for Io, Stacore Basic+ for amps; power: Torus AVR60BAL; room: 19' wide X 24' long X 14' tall; acoustic treatment: ASC IsoThermal Tube Traps, Lumitex drapes

  8. #8
    Quote Originally Posted by microstrip View Post
    Most probably because it is much easier to do, absorption in the bass needs a lot of work, space and more money. Curiously it seems that absorption in the bass is what is more needed in most rooms.
    Agreed. That is why many acousticians prefer multiple subs and DSP EQ in the bass, with precise center frequency and Q, rather than absorption. That, and most off-the-shelf bass absorbers are not very effective below 100Hz, which is where the biggest room modal issues in dB typically occur. Check their measurements and, most importantly, measure the room!

    Floyd Toole once said he did not like absorbers because they are an inefficient, broad frequency band solution to what is typically a narrow band problem.

    Above the bass, absorption may be effective and the problems of a more broadband nature. But, even there, you gotta know what you are doing. You can come to prefer and get used to even an inferior solution. Me? I use none. I just use a thick padded rug, careful speaker placement, dipole speakers with limited vertical and horizontal dispersion, a high ceiling and full range EQ. I am very happy with that.
    Last edited by Fitzcaraldo215; 08-22-2017 at 11:53 AM.

  9. #9
    WBF Technical Expert (Speaker & Acoustics) [Technical Expert] Mark Seaton's Avatar
    Join Date
    May 2010
    Location
    Chicago, IL
    Posts
    318
    Quote Originally Posted by caesar View Post
    Why do so many acousticians recommend absorption for everything in the room, vs. just using absorption for the bass portion of the space?

    Are guys just unquestioningly going back to some research paper someone wrote a century ago? Have acousticians become accustomed to dead sounding spaces and everything else sounds wrong? Or are there valid reasons?
    Over the years most have progressed away from an oversimplification of the horrible sounding, thin absorption all over the room. The real hurdle is not a question of the gross amount or area of how much absorption vs diffusion vs reflective. In domestic listening rooms it's all about addressing the bandwidth and spectral balance of the energy in the room over time. Extensive absorption gets a harsher critique than is warranted from so many putting 1-2" thick panels everywhere in days fortunately long past. While this makes a big change to the acoustics, it does so only above 1-4kHz, leaving the rest to roll around the room, and hugely shifting the balance of energy to sound tubby and dull. If the absorption is adjusted to have a more broad band effect and less aggressive in the upper frequency range, the results are much more pleasing, with very noticeable improvements in clarity, intelligibility, image specificity, and tonal balance.

    A more reflective, diffusive solution which attacks strong reflections so they don't stand out from the crowd as much will result in an improvement in spaciousness, soundstage width, and tonal balance while making for a subjectively larger image vs the precise and pinpoint image of a less reflective room. Again this is all about addressing the full bandwidth.

    Absorption is much easier to conceptually understand in terms of wide bandwidth, and apart from the devices being necessarily deeper and bulkier, they are easier to design and deploy in room. I like to recall a tip and realization Keith Yates gave to me over a frosty beverage. Paraphrased: "Well placed, broad band absorption is the poor man's diffusion." The "poor man's" qualifier here was not as literal as it was a colloquial term, and really meaning those not investing in extensive modeling and complex, and then expensive, diffusion devices which benefit from more detailed knowledge when selecting and deploying. The point to take away and being made was that treating the right areas with broad band absorption and leaving reflective areas between can achieve the desired effect through a more empirical and straight forward approach with affordable or easily constructed devices. The key here is the broad band qualifier, where this basically means anything protruding less than 3" from the wall/surface should be scrapped. Occasionally such panels are useful in larger rooms to attack a few surfaces after other extensive treatments are applied, but the treatments that have significant, and really desirable absorption effects will be thick.

    There are products which combine some diaphragmatic and unique, resistive elements to achieve absorption below 500Hz in reasonable depths, and this is where data can be useful to qualify products. RPG's Abfusor and newer designs from Quest Acoustics combine higher frequency diffusion with mid-band absorption to better balance the high frequency and lower frequency treatment in the room, and are a very useful step beyond the 2-3" absorption panels. Another more recent trend in products more readily available (previously more so custom solutions) are those like GIK's Alpha and Impression series of thick absorbing panels where a hard face with differing area and patterns of openings maintain some reflectivity and diffusion effects above 1-4kHz, while the reduced open area on the front often enhances the lower frequency absorption. In simple terms, the idea is to limit the higher frequency absorption to better balance the 125-500Hz region.

    The lower region ~100-500Hz is typically has long decay times and significant ringing in all but the largest and most open rooms or those with many openings and lossy surfaces. Ironically the easiest absorption panels to construct and deploy are most effective above 500-2kHz, and hence it requires some thought and creativity in selecting devices and approaches to control the energy in the room, be it through absorption and/or diffusion, in a balanced manner.
    Mark Seaton

    Seaton Sound, Inc.

  10. #10
    Gentlemen, thank you very much for great responses!

    What I am still a bit unclear about is that every time I have heard diffusion, it adds spaciousness, while absorption - when used in spots where diffusion could be used - kills the room. There is even a video somewhere of Ethan Winer playing a guitar near diffusion panels and you can tell - even on youtube - that diffusion allows one to hear a more spacious sound. But then, as a seeming contradiction, when one looks at Ethan Winer's room, it has so many absorption panels, it is probablly deader than disco...

    So if diffusion positively adds to the experience in terms of hearing the spaciousness of the venue, while absorption takes away from that experience (other than in lower regions), why don't most people use it?

    Is there a room measurement that can help explain this? Or is it just preference? Thank you!

Page 1 of 3 123 LastLast

Similar Threads

  1. John storyk on room acoustics , glass aint bad , low freq .....
    By andromedaaudio in forum Room Acoustics Forum
    Replies: 11
    Last Post: 02-01-2017, 03:20 PM
  2. who would you recommend for remote room calibration
    By bebop86 in forum Room Acoustics Forum
    Replies: 6
    Last Post: 01-19-2016, 06:18 PM
  3. Definition of a Live vs. Dead room?
    By caesar in forum Room Acoustics Forum
    Replies: 8
    Last Post: 12-24-2013, 09:48 AM
  4. Can a Room 'Leak' Bass?
    By Rutgar in forum Room Acoustics Forum
    Replies: 49
    Last Post: 01-06-2013, 02:43 AM
  5. Replies: 53
    Last Post: 11-20-2010, 07:51 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •