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Thread: How much room damping needed for quiet listening?

  1. #1
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    Default How much room damping needed for quiet listening?

    I am in the process of acoustically treating my 3.5m by 3.5m bedroom and am thinking of getting some Super Hl5s.

    I have got 10cm thick foam corner panels(size 4 feet by 2) for low-high frequancies BEHIND the speakers (from Advanced Acoustics) and have got regular 4cm thick panels at the first reflection points.I have ordered a 4cm thick panel to sit landscape orientation on the wall behind my ears.

    Would i benefit from more panels elsewhere with regards to tightening up the bass of the speakers? I would get more of the corner panels - but behind where i sit the corners are occupied by a bed on one side and a small bookcase the other.

    I do listen at low levels in the nearfield and love the sound of the cello.

    I also get quite bad flutter echo in my bedroom which has brick walls.I have thick carpet laid on the floor,one other small bookcase and a sofa-type armchair in my bedroom.Overall,the room looks and feels sparsely furnished.
    "No Man an Island" - John Donne

  2. #2
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    Default How much room damping needed for quiet listening?

    Thank you Alan.

    Yes this is a room treatment issue really.

    However,i was taken aback when one of the acoustic foam providers advisors asked me if the SuperHL5s were front ported or not - this led me to wondering about the possible implications.

    Also,what i really wanted to know is how much room treatment is needed for someone who listens at LOW levels in the NEARFIELD to the HL5s?
    "No Man an Island" - John Donne

  3. #3
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    Default Re: How much room damping needed for quiet listening?

    Al low frequencies the wavelengths are many metres long. However, what the port sees is a pressure build up as it pumps air so there would be a difference between a port facing the room and one facing the wall.

    I'd say you've hit the nail on the head here. The amount of energy you need to absorb is a direct consequence of the amount you pump into the room. So less in, less bouncing around and less absorption needed. I think I'd hang fire on applying any more until after some serious listening; sounds to me like you've got it about right.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  4. #4
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    Default Re: How much room damping needed for quiet listening?

    To add to Alan's comments, the ear is not as sensitive to low frequency sounds at low levels so some lift in the bass might actually be pleasing.

    Don

  5. #5
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    Default Overloading the listening room ...

    I completely agree - good point.

    In fact, since I posted, I was considering what I have heard these past few days at the CES. Walking into the hotel bedroom demo room you will be greeted by one of these experiences:


    • Ludicrously loud. The room is overloaded with energy, especially in the bass. As the room absorption is negligible the bass is muddy. Interestingly, if you fight your way through the crowded room (the bass acts as a crowd pulling magnet) then it sounds OK. The bodies absorb and break-up standing waves.


    • Just right; the demonstration is as at the maximum level that the room can take i.e. absorb. This needs a little acclimatisation to after visiting loud rooms. Visitors often ask for the volume to be increased.


    • Too quiet or narrow bandwidth music; not a common experience. Example of a speaker system which has a design optimised for a certain music/loudness and which sounds best on a few instruments at as low-ish level. Maybe they only play acoustic guitar or brass.

    Every room, treated or not, can absorb or dissipate up to a threshold loudness. Beyond that the reflected energy swamps the listener. It has opened my eyes to occasional feedback about this or that model being difficult to use in an untreated room. I now realise that if these few days experience are anything to go by, I should ask about how loud they are playing.

    I've noticed that as a general experience over many years, music demonstrations at shows are invariably too loud for the room, especially so here in the USA. A good dealer knows exactly how hard the room can be driven and the power required is always far below the speakers maximum power handling capacity. I'd guess that a normal room could only take about 25W of equivalent input power.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  6. #6
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    Default Re: Overloading the listening room ...

    Quote Originally Posted by A.S. View Post
    Every room, treated or not, can absorb or dissipate up to a threshold loudness. Beyond that reflected energy swamps the listener. It has opened my eyes to occasional feedback about this or that model being difficult to use in an untreated room. I now realise that ...I should ask about how loud they are playing.
    I agree with this. And I suspect this is why the M40.1 reportedly works very well in small rooms by users in Asia whereas some US users complain about too much bass even though their room is much larger. My theory is that in a small room, you don't have to play it loud to fill the room with music, so the bass is not over-bearing. But in a large room, they have to turn the volume up (perhaps above the designers optimal desgin) to fill the room with music, then experience bass boom.... then again, it seems those folks can fix the problem by using a $10K speaker stand!!!

  7. #7
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    Default Re: Overloading the listening room ...

    Quote Originally Posted by Will View Post
    ... And I suspect this is why the M40.1 reportedly works very well in small rooms by users in Asia whereas some US users complain about too much bass even though their room is much larger.
    This is really interesting. If you are correct it fully explains why broadcast (pro) users have never had an issue with the M40/40.1 and why I cannot replicate it in my listening room where I listen at a moderate level. I'll look into this more sometime after I return to the UK.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  8. #8
    yeecn Guest

    Default Re: How much room damping needed for quiet listening?

    My experience with C7ES3 is that the bass response is not linear with respect to to loudness. In my living room my perceived bass response of C7 remain more or less constant form whisper to moderately loud level. This would mean that bass response must be decreasing as the volume is turned up.

    In contrast I have a small active speaker where the amplifier is equalized to give an insane amout of boast to the bass. It was bearable at the lowest listening level, but as the volume is turned up the bass became completely overwhelming.

  9. #9
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    Default Re: How much room damping needed for quiet listening?

    Quote Originally Posted by yeecn View Post
    This would mean that bass response must be decreasing as the volume is turned up ...I have a small active speaker where the amplifier is equalized to give an insane amout of boast to the bass....
    Especially in the bass region we do have to be very careful to draw the right conclusions from our observations.

    If I measure that speaker in an anechoic chamber the bass output is not significantly effected by how loud the test signal is. But put the speaker in a real room and the room will definitely have an effect. That's true of all speakers in all rooms.

    It's not just level, we must be critically aware of Q.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  10. #10
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    Default Re: How much room damping needed for quiet listening?

    I wonder if it might be possible to create a CD or downloadable WAV file with music or tones or both, specifically selected to highlight various problems with the room and to allow optimization of the combined room/speaker system without the need for expensive test equipment.

  11. #11
    yeecn Guest

    Default Re: How much room damping needed for quiet listening?

    Quote Originally Posted by A.S. View Post
    But put the speaker in a real room and the room will definitely have an effect. That's true of all speakers in all rooms.

    It's not just level, we must be critically aware of Q.
    You must be right. I was just thinking that I have not considered the room reflection/damping factor after I posted my response.

    I am only just beginning to learn to discern room reflections after I started to listen via headphones recently. I was surprised by how much reflections there is in my living room.

    Given the non-linear nature of the human hearing wrt frequency and loudness plus the complex factor of room acoustics, I find it hard to believe that the bass/treble controls has been taken out of almost all amplifiers, for the sake of the elusive 'purity' of sound. I believe that most problems can be handled by some amount of equalization on the amplifier.

  12. #12
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    Default Re: How much room damping needed for quiet listening?

    Quote Originally Posted by yeecn View Post
    ...I find it hard to believe that the bass/treble controls has been taken out of almost all amplifiers...I believe that most problems can be handled by some amount of equalization on the amplifier.
    I agree. Tone controls were developed for a purpose - to help get the best from the music/speaker/room interface. Tone controls vanished. The problems remain.

    I believe that the tone control circuit when properly designed is acoustically transparent.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  13. #13
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    Default Re: How much room damping needed for quiet listening?

    Is it important that foam corner panels designed to absorb LOW,mid and high frequancies form a TIGHT FIT in the corner ?

    I do know that air behind the panels does help in their function.
    "No Man an Island" - John Donne

  14. #14
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    Default Re: How much room damping needed for quiet listening?

    First - and this is really important - a few 50cm x 50 cms pieces of absorber foam sprinkled around the room just will not do anything other make you poorer. Think about this: to make any worthwhile difference, the absorber must occupy a minimum of about 25% of the entire surface area of the room's four walls + ceiling. Two or three pieces of foam, even pretty sculptured foam, will be completely useless as a general absorber. They just don't cover enough area to make a difference.

    Then, separate issue: to absorb low frequencies you need thick, deep absorbers perhaps 1m thick or panel absorbers (see here). Therefore, it is really irrelevant whether the skimpy foam is placed tight into the corner or away - it's going to make no difference what so ever at low frequencies. It may well absorb a little in the middle frequencies and better still in the higher frequencies. But at the bass end - useless.

    If all architectural acoustic issues could be solved at a stroke with a skimpy bit of damping here and there, highly paid acoustic consultants would be out of business - project here. Architectural acoustics is big business employing the best brains and the most sophisticated measuring and computer modelling equipment. You won't find any room tuning bells used in acoustic design for obvious professional reasons.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

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