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Thread: 'Freshmen' with Harbeth 40.1 (part II)

  1. #21
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    Default Check tone controls

    Quote Originally Posted by Mazokist View Post
    Dear Mr. Show,

    Thank you for time that you spend trying to find out right idea how to solve my 'room acoustic issue'. I really appreciated it.

    Reading your last post I find out that 'acoustic situation' in my room is even worse, because until now, I do not 'calculate' nothing that is on other side of curtain. Truth is that on another side is glass windows (all the way in upper part) and again sloped wall, as you can see on attached photos.

    Regards
    OK, I'll do what I can. About the amplifier and its tone control. Can you check the operation of the tone controls please? Please play some normal classical orchestral music. Whilst the music is playing press-in the Tone button and rotate the treble and then the bass control up and down. Can you definitely hear a change in sound when both controls are rotated up/down?

    Incidentally, I note from this evening's national commercial ITV, that award-winning The Cube (also here) was broadcast. It's made on Monitor 40.1s. We intend to run an article on the construction and use of the brand new ITV Leeds Emmerdale studios, which is made with the M40.1s. You can see one of the control rooms under construction. The big difference between these environments and yours is that they, like all serious professional studios, are acoustically treated to make then a relatively dry acoustic, free from echoes and with a controlled absorption at low frequencies. No great acoustics theoretical skill or fancy test equipment is required to construct such a room, although both make success more likely. What is needed is to make as high a proportion of the total surface area of the room absorptive. That means, in simple language, cover as much surface as possible with Rockwool - see picture. Can you see the white and black tea mugs in the middle of the picture on the battening? That indicates that the Rockwool is about 80mm thick.

    I fully appreciate that your listening room is not (and cannot and should not) be damped to professional standards, but to get the best of a professional speaker some attention will have to be paid to absorption. Believe me, in the cost-conscious world of TV, if studios and control rooms could be built without expensive sound treatment, they would be, but the creative staff usually win the argument over the accountants that for professional monitoring, it is really essential to separate the sonic character of the replay room from the recording itself.

    >
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    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  2. #22
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    Default I'll take a freadom and suggest conclusion of this thread

    Dear Mr. Show,

    I will follow your instruction and be focused on acoustic treatment of my listening/living room. At this moment I'm not able to do nothing in 'wall structure' but I will make research upon this topic and find out what is best solution for 'on wall treatment' . Also, I will try to make some 'acoustic vs. design' compromise and hope to get sufficient result on both field. As I rough direction can I follow some solution from attachment:

    regards and thank you again
    Attached Images Attached Images

  3. #23
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    Default Wrong solution!

    VERY IMPORTANT POINT!!

    The four pictures you provided are NOT sound absorbers. (Actually the first one, the square with the slots cut in its face may absorb to a small degree).

    You have shown pictures of sound scattering devices. Scattering sound does not absorb it. It just reflects it. Your problem may be inadequate absorption at low frequencies. These scattering devices will not help you at all. They will be invisible to high energy, low frequency sounds. Don't waste your time and money - they are designed to help with high frequency sound problems.

    Remember what I carefully explained a few posts ago: if you are to absorb low/mid frequency sound you have to convert it to heat inside a fibrous material, like Rockwool or possibly Melamine. There is NO other solution. If these alternative products you suggest worked at low frequencies, professional studios would not use expensive Rockwool lines walls and ceilings. Like them you must use soft, thick, semi-rigid material.

    What you show are hard, rigid, highly reflective surfaces - totally useless for low frequencies. I repeat: they are completely the wrong products.

    P.S. I guess that your problems are below 100Hz in frequency. As you can see from this chart even 100mm thick malamine has almost zero absorption below 100Hz. Its excellent absorption properties are at 90% + for the middle and high frequencies, say from 300Hz upwards. So, even if you completely filled your room from top to bottom, side to side with melamine, it would barely effect the low frequencies. You are back to Rockwool again as the only viable surface treatment solution.

    Proof:

    Look at this page here describing the absorption of Rockwool. Look down the left column of the first table until you find '703, plain' 4" (102mm). Now look right until you see the number in the column headed 125Hz. That number is 0.84. That means, this size/grade of Rockwool absorbs 84% of the sound falling on it at 125Hz - an impressive result. Now compare that with 100mm of the Basotect here. As the blue line is 100mm thick, follow that left to 125Hz and read off the absorption. Let's say it is 0.15, which means 15%. There is no contest between these materials: the same thickness of Rockwool is about six times more effective at absorbing 125Hz which is why it is the only solution at low frequencies. That's why studio designers use it as I showed in the picture.

    When considering absorption efficiency of a material, you only have to look at the manufacturer's published results table or graph v. frequency. That tells you everything you need to know. If no data is available, walk away.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  4. #24
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    Default Got it!

    Thank you Mr. Shaw, this time I got it.

    regards

  5. #25
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    Default Room tuning voodoo

    OK.

    Incidentally, the absorption coefficient tables/graphs are the standard way for acoustics people to compare the efficiency of various absorption methods (not scattering, absorption) according to thickness and frequency. This data is widely, internationally used when designing homes, public places, concert halls and studios. Even if you don't speak English, you can read .... 125Hz, 0.85 .... and that tells you everything you need, except for cost and cosmetics.

    From time to time various 'room tuning' voodoo gadgets appear on the market. They usually have a romantic sales story. They include mystical bells the size of an egg, magic crystals, cosmic ray neutralisers and the rest. The fact is that the absorption coefficient of these (hard) devices is certain to be zero so they cannot have any meaningful influence on the sound in the room. Why do people throw themselves at these products when inspection of just two numbers - absorption coefficient (or percentage absorption, the same thing) and frequency can comprehensively describe their entire acoustic (non-) performance?

    Professional acousticians think that the audiophile who is suckered into believing in such self-evidently non-functional products is a complete idiot. If these tweaky products actually worked, acousticians would be able to save their architect clients the cost and weight (and cosmetic impact) of Rockwool and could transform the acoustics of a public lavatory into that of a great concert hall for very little time, money and effort.

    Simple, common sense rule of thumb:

    • To absorb sound the absorber must be fibrous, or a combination of a (semi-rigid) skin + fibrous + air gap

    • The thicker it is the more sound it will absorb.

    • The more dense it is the more low frequencies it will absorb (but it may be more reflective at higher frequencies)


    Below is an article from a studio magazine which gives a hands-on guide to DIY absorbers. NOTE! In this article the absorber panels do not cover much of the total surface area of the walls. This means that their absorptive effectiveness will not be great in the lower frequencies. Also note that the Rockwool used is only 30mm thick. If you look-up the absorption coefficient of 30mm Rockwool again here, the second line in the first table (703 plain 25mm is the nearest to 30mm), then following along to the 125Hz column gives a figure of 0.11 - virtually useless - compared with the previous 0.85 for the 100mm thick material (previous post) at 125Hz. With thin absorber material you just cannot absorb low frequencies - that's physics.

    >
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    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  6. #26
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    Default DIY absorption

    The DIY thing appeals to me - I don't believe you need to spend huge amounts of money on sound absorption. Rugs, carpets, lined curtains, wall hangings and the judicious use of duvets have always been my line of attack when installing systems in troublesome rooms.

  7. #27
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    Default solution, just a sugestion

    Dear Mr. Show and hifi_dave,

    I do some research over the net and find, I hope, god compromise between function and esthetic of room acoustic elements. As you can see on this link:

    http://www.recordingstudiolondon.co.uk/acoustics

    product called 'walls' is able to reversed or remove very easily. During the listening sessions absorbing material (Rockwool) is on the 'room side' and all other time I can turn it to the wall and get nice looking wood 'sculpture'. Please, am I done a good 'homework' and what is the best place/area of application of this product (DIY, of course)?

    regards

  8. #28
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    Default My experience, now fabulous after room adusting

    Hi. I just came across this thread.

    It took me a lot of tinkering to make my 40.1 sound "great" rather than "good". I too was having bass "boom" issues and a recessed midrange. It was driving me mad!

    The way I got round this was:
    1. position my speakers according to the Cardas method.
    2. measure the frequency response of my room using the Rives audio test tones and radioshack spl meter. I then adjusted the seating position to get the best response.
    3. treat the 1st, 2nd, ceiling and floor reflection points (to the best of my ability) and use bass traps (although, I'm not convinced they make that much difference).
    4. I have also added some absorption directly behind the listening position. The seat is a bit close to the back wall, but this is where I had the flattest frequency response.

    Now things sound fabulous (without going into the normal audiophile descriptors).

    Good luck!
    Attached Images Attached Images

  9. #29
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    Default Damping

    Just try to put one matress behind the speakers (initial setup) before make any investment.

  10. #30
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    Default The Cardas method of speaker placement?

    Quote Originally Posted by teddyboy View Post
    ...position my speakers according to the Cardas method...
    Hi,

    Is there anyone that can explain to me the "Cardas method"?

    Thanks,

    Sébastien

  11. #31
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    Default The Cardas room method

    Here is a link to a pdf file explaining the Cardas method. http://www.cardas.com/pdf/roomsetup.pdf

  12. #32
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    Default Rectangular room's challenges

    Thanks Don,

    I took a look at the document that I found interesting. It's quite funny because my last two apartments had the listening room in the lounge and the shape is similar to what we see in diagram F of the document. The "problem" is that I don't have many choices regarding the position of my speakers. Well, I can play a lot with distance between them. I can easily move them 1m from the rear wall, but I don't have choice to place them against the longer wall and to place them in one half of the room.

    Nevertheless, I'm able to have a pretty good sound but still wondering what could be the better placement for my SHL5.

    Sébastien

  13. #33
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    France
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    Default Simple treatment

    I just submitted a thread with pics of my system.
    Imho those rather high angled ceilings are awful when it comes to reflections.

    I treated my room a few GIK absorbant panels, but most of all, I used pillows with great results. May e you'll see them if my post is approved. The pillows act also as diffusors. They were placed in a hazard way above the listening seat to cut the parallel surfaces.

    They made a huge effect in a very reverberant room. But of course they may "destroy" your interior. GIK art panels will be the best choice for you I think.

    Now I have a boomy bass on some recordings but imho it comes from the floor in my case and I think that better isolation between the Skylan stands and the floor will help a lot. I think that even if this may not be the main cause of your problem, you should give a try to better decoupling devices for the stands, than the small spikes they come with.
    All the best for hoping better results for you,
    Jerome

  14. #34
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    Default Bass equalisation in real-world domestic rooms

    Quote Originally Posted by Jerome W View Post
    I just submitted a thread with pics of my system. Imho those rather high angled ceilings are awful when it comes to reflections.

    I treated my room a few GIK absorbant panels, but most of all, I used pillows with great results. May e you'll see them if my post is approved. The pillows act also as diffusors. They were placed in a hazard way above the listening seat to cut the parallel surfaces.

    They made a huge effect in a very reverberant room. But of course they may "destroy" your interior. GIK art panels will be the best choice for you I think.

    Now I have a boomy bass on some recordings but imho it comes from the floor in my case and I think that better isolation between the Skylan stands and the floor will help a lot. I think that even if this may not be the main cause of your problem, you should give a try to better decoupling devices for the stands, than the small spikes they come with.
    All the best for hoping better results for you,
    Jerome

    I have a relatively well treated room (vicoustics products to first and second reflection points, including ceiling. Also, vicoustics tics bass traps). My room is approx 4x3.

    I still had a prominent node at 33.7 Hz (according to my measurements). I installed room eq (Rives PARC). The results have been amazing! Smooth, well defined and extended bass with no boom or muddying. The best audio investment I have made.

    My belief, which may be unfounded, is that unless you have the "perfect" room, or, a speaker with very little low frequency extension, or, a complex arrangement of subs, you just have to have eq.

  15. #35
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    Default Big speakers in untreated rooms

    Avoiding room nodes (cardas method) when placing the speakers and some solid bass traps in the corners should bring you a long way. You can easily experiment by putting your sofa pillows in the corners before spending money on more professional stuff. Or buy some big nice pillowcases (of acoustically transparent material) and fill them with rock wool, place in corners. Elegant and cheap solution. Effect of bass traps depend on room in my experience, was definitely required in my old room with concrete walls less so in my new apt with plastered walls.

    Big speakers like the 40.1 are a challenge in a domestic environment due to the amount of energy they put in the room. I would argue room treatment or acoustic design of the room is mandatory to realize the potential of such speakers.

    Rgds
    Svein

  16. #36
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    Italy
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    Default Rockwool or Melamine

    Hi
    Just a question about one of the remarks Alan has made: rockwool vs. Melammine.
    It is not really clear from his post if these two materials are more or less equally effective or not.

    Can someone help clarify? I am considering some additional acoustic treatment on reflections, and thought to use melammine panels...
    D

    {Moderator's comment: please study the data provided in the various posts/links as this gives you the complete answer. Remember absorption coefficient v. frequency and thickness?)

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