Request Info & Guidance In Acoustics

Amp_Nut schrieb:

I am in the process of shifting my stereo into another smaller room ( 14 feet length x 11 feet width x 9 feet height ). One wall is a Glass Sliding window of approx 9 feet wide and 4.5 feet height. The speakers will be placed with their back to this Glass window ( Heavy Curtains will certainly be used ). I will actually be 'thrown out' of the living room next month, when it goes for renovation. However, I plan to start doing my den only in March. I will be making the room my 'Den' and therefore have a COMPLETE free hand in its layout etc A casual placement of my Stand Mount speakers, sounded Terrible, but Deaf and others have said the room could sound good. Would appreciate info from Forum members on : 1. Suggested sites that provide good, usable info on acoustic considerations. 2. What are the tech parameters to shoot for ? 3. What should the Ideal RT60 time be for this room. ( 2 channel stereo, no Home theatre ) 4. What is the tolarable RT60 ? Any and All other tips and info welcome... no APPRECIATED. I am a newbie in acoustics... so please dont skip the obvious. THANKS !

Well, all the info I'm sharing with you is NOT absolute. With that understanding....

Amp_Nut schrieb:

The speakers will be placed with their back to this Glass window

Agreed! The effect of the windows will be minimized. With so much glass in the room there could/will be some loss of bass.

Amp_Nut schrieb:

( Heavy Curtains will certainly be used )

this is good in one sense that it will negate the effect of the reflections of the sound off the glass.
However, one caution: the heavy curtains will deaden the space behind the speakers.
When I was setting up my room I learnt that the space behind the speakers must not be all dead i.e. there has to be a mixture of live & dead behind the speaker. what I found worked most awesomely was that the corners behind the speakers should be fully reflective & the wall immediately behind the speaker must be dead. The behind wall in between the speakers must be fully reflective. Tube traps work superbly for this job as they can control bass boom & also mids & highs. There is a receipe to build DIY tube traps off Jon Risch's website. I don't have it handy but I'll find it for you OR you can search it using Yahoo or Google.

Amp_Nut schrieb:

I am in the process of shifting my stereo into another smaller room ( 14 feet length x 11 feet width x 9 feet height ). ....... ....... 3. What should the Ideal RT60 time be for this room. ( 2 channel stereo, no Home theatre ) 4. What is the tolarable RT60 ?

Given your room dimensions, I note that you will have axial mode fundamental frequencies of 40.36Hz, 51.36Hz & 62.77Hz + all their harmonics. Their harmonics will have gradually decreasing power.
Your stand-mount Sonus Fabers might not be responsive to the 40.36Hz & 51.36Hz fundamentals but might be to the 62.77Hz fundamental (?). you would know this.

Re. RT60 times: this is, of course, room volume + wall material + room contents dependent. You must also expressly note that RT60 times do not take into account the idiosyncracies of the room. Hence, if you do measure RT60, measure it in 3-4 different locations & average the result. Also, note that you must measure RT60 at different frequencies between 125Hz & 4KHz. I believe that the standard is to measure it at 125Hz, 250Hz, 500Hz, 1KHz, 2KHz & 4KHz.
I've noted that for a room that is 5000 cubic feet might have a RT60=1.1 sec at 60Hz & a RF60=0.6 sec at 1KHz. However, this is a superbly treated room & might be beyond do-able in most home settings.
According to the AES, the RF60 times between 200Hz & 4KHz is given by the approx equation 0.25*(V/V0)^1/3, where V0=reference room volume=100 cubic meters.
So, if we use this above equation then, to answer question (4) above, the tolerable RF60 of your room will be 0.25*(1386 cubic feet/3531.47 cubic feet)^1/3=0.18 seconds.
Note that this is average RF60 i.e. average of several measurements in the room. You might be (very) hard-pressed to meet this number.
This AES document is located here:
http://www.aes.org/technical/documents/AESTD1001.pdf

I know that it says "MULTICHANNEL.....". However, do not let that put you off. There is a wealth of info in there that I believe id applicable to 2-ch setups.

Another thing to note: From my experience of houses/apts built in India, the walls are often painted concrete. The sturdier the wall, the higher the RT60 as the sound bounces repeatedly off these stiff walls before it dies out.

To answer (3) above:-
I found a RT60 calculator:
http://www.trinitysoundcompany.com/rt60.html
I inserted your room dimensions + painted concrete for all the walls & ceiling except "glass windows" for "Back" & calculated RT60=1.43 seconds @ 1KHz & 0.81 @ 125Hz (there goes your chance to meet the AES recommended 0.18 seconds! ).

Additionally there is some free-ware available from CARA and ETF (both German companies, I believe) that you can down-load onto your laptop or PC. I don't have their website handy but a search using your favourite engine will bring up their websites. You will need a microphone & using that free-ware you can measure the room response. I had a friend who used to own a TacT unit & he measured mine. we found that I had 2 humps at 80Hz & 120Hz. The room treatment has helped a lot but probably not eliminated it. The only way to eliminate it is to use active room control like a TacT or a Rives PARC. However, they degrade the overall sound. This is what my friend found too hence his TacT is long sold off!

OK, so there is a lot of theory here that needs to be melded with some practical tweaking when you set up the room & equipment.
Setup the parameters one-by-one so that you can evaluate what each parameter is doing. Later on this info is very helpful if you want to tweak the setup - you will know which knob to turn. It might take you longer to setup but the pain will be worth your time.

OK, I think that I've babbled enough.

bombaywalla schrieb:

OK, I think that I've babbled enough.

Please babble some more

Very informative!..this thread is on my favourites now!
Regards,
Sachi

Dear Bombaywalla,

Thanks for an informative post... I was beginning to lose hope....

I have had little to no response to my earlier posts and was beginning to wonder if most members, are here only to receive rather than share...

That said, your post was CERTAINLY not too long and I welcome any more info that you have to share. Yes, assimilating / following up on the info that you have provided will also take me a while, and probably a weekend well spent.

I have a few queries...


1.

what I found worked most awesomely was that the corners behind the speakers should be fully reflective & the wall immediately behind the speaker must be dead. The behind wall in between the speakers must be fully reflective. Tube traps work superbly for this job as they can control bass boom & also mids & highs.

Generally, the bass trap would be placed in the corner behind the speaker... the space where multiple walls tends to create reflections and resonance in the bass.. No ?

But you say

the corners behind the speakers should be fully reflective

Have I mis-understood ?


2. Yesterday I stumbled across a nice RT60 calculator on the net, while in office. I dont have the URL here on my home PC.

It was a very user friendly RT60 calculator.

It did not say anything about the ideal RT60 time but said that the RT60 for all freq from 125 Hz to 4KHz sould be equal... within 15% variation.

What are your thoughts on this ? Please advice.

Using Marble Floor + Concrete walls & ceiling ( as is present in the room ) gave RT60 times that varied in Freq from 0.65 to 1.1

However using Plaster tiles on the ceiling and everything else constant, gave me almost uniform RT60 times of appr0x 0.7 !

I know that this is only theoritical, and practice will not be so straightforward, but seems to point to a good starting point...

Your thoughts ?

3. You indicate that the space behind the speakers should be reflective, but experience shows that placing a TV there... even a Plasma / LCD is detremental to the sound !

Switch-it-on seems to have achieved success with a blank wall draped by a thin carpet ( Duree ). That provides good visual stimulation too..



I Will certainly read the AES paper that you have suggested. Chapter 6 seems to address what i need to learn.

Any more thoughts / suggestions and pointers are welcome.

Hey other forum members, could you guys also contribute ? I am sure you all have your EXPERIENCES ... if not formal knowledge....

So please do SHARE

Hi Amp Nut,

Setting up speakers in a room certainly requires quite a bit of work and experimentation. There are no hard-and-fast rules, just some guidelines. Since room shapes, and furnishings, vary so much, each location is unique and so is its arrangement.

Don't worry too much about reverberation times (RT60). Reverberation times are relevant in much larger spaces, where reflected sounds build up to a larger degree. Small rooms don't lead to predictable, even measured, reverberation times. However, for loud reproduced music, a good target RT60 would be 0.8-1.0 seconds. (A RT60 of 0.18 seconds is an absolutely dead room, one you can't even enter - imagine solitary confinement in a padded coffin!).

I suggest a normal mix of reflective and absorptive surfaces - an upholstered sofa, a carpet, and curtains should suffice.

Where you'll really have to experiment with is controlling room resonance modes for good bass reproduction. If it can't be done by positioning speakers, then you have to resort to bass traps. Deaf has already given very good tips. It also depends on how well your speakers are damped, especially in the bass frequencies. A loosely damped bass is almost impossible to control in a small room.

Viren.

Sorry, that should have read Bombaywalla.

Viren.

Alstorm make some absorbent tiles....A friend of mine did try to find out whay frequency range they would best be suited for but got no details.

Anybody have any details on such stuff ?

Manek.

Manek,

Are you refering to Armstrong brand ceiling tiles ? If so you can get tech info from their website.

http://www.armstrong.com/commclgpac/asia1/ep/in/

regards

Anil

Ani,

thanks for the correction...got a bit confused between "armstrong" and the "power generation company".

Manek.

Most acoustic premanufactured panels, from Armstrong and Anutone, absorb only the mid and high frequencies. Their efficiency of absorption is also dependent on their mounting - an air gap behind the panels. This level of detail gets to be too much for a domestic environment. You can achieve similar results with normal home furnishings.

Some hard wall panels, properly mounted, can also serve as low frequency absorbers. Again, this level of design is unnecessary for a home. Play with location of speakers for good bass response, first.

Viren.

Most acoustic premanufactured panels, from Armstrong and Anutone, absorb only the mid and high frequencies. Their efficiency of absorption is also dependent on their mounting - an air gap behind the panels.

That is an important point I learnt from Bombaywalla's post above.

Incidentally, the gap between the panel & the wall could be nice for subtle, concealed lighting, no ?

Some hard wall panels, properly mounted, can also serve as low frequency absorbers.

Viren, some examples of what can be used to create these Hard Wall Panels ?

Thanks.

Hi Amp_Nut
I would firstly like to say that what we are familiar with as acoustics, is usually large room acoustics.Even in large room acoustics there are different citeria for live and for reproduced music.What we neeed to study is small room acoustics, for reproduced music.I think that is the area we need to concentrate on.
Deaf.

Deaf said :

What we neeed to study is small room acoustics, for reproduced music

Any pointers / guidelines or references I can read on the net ?

Thanks

The speakers will be placed with their back to this Glass window

What abt inverting the scenario, put the speakers close to the wall opposite to the glass wall, it is possible, give it a try.

- Debu

Amp_Nut schrieb:

1. Generally, the bass trap would be placed in the corner behind the speaker... the space where multiple walls tends to create reflections and resonance in the bass.. No ?

there seems to be a slight misunderstanding here - I went back & re-read my post. Therein I wrote tube trap & not bass trap. The traps that I'm using are bass traps + mid/hi traps all rolled into one (no pun intended!). Hence these TUBE TRAPS can do both absorption + midrange reflection. The bass absorption happens inside the hollow cylinder & the mid/hi reflection & absorption occurs on the surface.

But you say the corners behind the speakers should be fully reflective Have I mis-understood ?

I believe so! If you use TUBE TRAPS then you can set them to be fully reflective (YES, fully reflective! - did not make a typo here) in the corners (where 2 walls meet) + fully absorptive smack behind the speaker.
This is the way I ended up in my room. The 1st time I put the tube traps in the corners, I made them fully absorptive & that deadened the room like you would not believe!

Amp_Nut schrieb:

2. Yesterday I stumbled across a nice RT60 calculator on the net, while in office. I dont have the URL here on my home PC. It was a very user friendly RT60 calculator. It did not say anything about the ideal RT60 time but said that the RT60 for all freq from 125 Hz to 4KHz sould be equal... within 15% variation. What are your thoughts on this ? Please advice.

well, this seems to corroborate w/ that AES document which also says that RT60 between 200Hz & 4KHz should vary +/- 0.05 sec.
I'm not sure that your room must satisfy this tight tolerance of RT60 times across the freq band. I'm sure that if the variation is 0.1-0.2sec, your room will sound just fine.

Amp_Nut schrieb:

Using Marble Floor + Concrete walls & ceiling ( as is present in the room ) gave RT60 times that varied in Freq from 0.65 to 1.1 However using Plaster tiles on the ceiling and everything else constant, gave me almost uniform RT60 times of appr0x 0.7 ! I know that this is only theoritical, and practice will not be so straightforward, but seems to point to a good starting point... Your thoughts ?

I don't know if I can make an intelligent comment on this except to say that the stiffer/harder the material (concrete/tile/granite, etc) the livilier the room as these stiff surfaces support the acoustic wave bouncing around surface-surface longer before they die down.
I'm surmising that in the 1st case with marble + concrete you had zero surfaces that yielded thus you had high RT60. In the 2nd case you introduced a surface (ceiling) with material softer than all the other surfaces & acoustic waves hitting the ceiling died some & contributed to a smaller RT60.

Amp_Nut schrieb:

3. You indicate that the space behind the speakers should be reflective, but experience shows that placing a TV there... even a Plasma / LCD is detremental to the sound ! Switch-it-on seems to have achieved success with a blank wall draped by a thin carpet ( Duree ). That provides good visual stimulation too..

That is correct - I meant to say that the wall behind & in between the speakers should be fully reflective. This enhances the midrange & the soundstage.
Now. remember that a tube trap is at the max 20" in diameter - more like 16" if you have the space & often 12" in diameter. So, there is a controlled amount of reflective surface in between the speakers on the behind-the-speakers wall.
How big/wide is a TV set + entertainment center? Likely wider than 20", correct?
Plus, it has a lot of glass on it, correct?
A tube trap does not have any glass reflective surface, correct?
So, we have 2 different animals here where the effect of each cannot be correlated (atleast IMHO).

bombaywalla schrieb:

Amp_Nut schrieb: 1. Generally, the bass trap would be placed in the corner behind the speaker... the space where multiple walls tends to create reflections and resonance in the bass.. No ? there seems to be a slight misunderstanding here - I went back & re-read my post. Therein I wrote tube trap & not bass trap. The traps that I'm using are bass traps + mid/hi traps all rolled into one (no pun intended!). Hence these TUBE TRAPS can do both absorption + midrange reflection. The bass absorption happens inside the hollow cylinder & the mid/hi reflection & absorption occurs on the surface. But you say the corners behind the speakers should be fully reflective Have I mis-understood ? I believe so! If you use TUBE TRAPS then you can set them to be fully reflective (YES, fully reflective! - did not make a typo here) in the corners (where 2 walls meet) + fully absorptive smack behind the speaker. This is the way I ended up in my room. The 1st time I put the tube traps in the corners, I made them fully absorptive & that deadened the room like you would not believe! Amp_Nut schrieb: 2. Yesterday I stumbled across a nice RT60 calculator on the net, while in office. I dont have the URL here on my home PC. It was a very user friendly RT60 calculator. It did not say anything about the ideal RT60 time but said that the RT60 for all freq from 125 Hz to 4KHz sould be equal... within 15% variation. What are your thoughts on this ? Please advice. well, this seems to corroborate w/ that AES document which also says that RT60 between 200Hz & 4KHz should vary +/- 0.05 sec. I'm not sure that your room must satisfy this tight tolerance of RT60 times across the freq band. I'm sure that if the variation is 0.1-0.2sec, your room will sound just fine. Amp_Nut schrieb: Using Marble Floor + Concrete walls & ceiling ( as is present in the room ) gave RT60 times that varied in Freq from 0.65 to 1.1 However using Plaster tiles on the ceiling and everything else constant, gave me almost uniform RT60 times of appr0x 0.7 ! I know that this is only theoritical, and practice will not be so straightforward, but seems to point to a good starting point... Your thoughts ? I don't know if I can make an intelligent comment on this except to say that the stiffer/harder the material (concrete/tile/granite, etc) the livilier the room as these stiff surfaces support the acoustic wave bouncing around surface-surface longer before they die down. I'm surmising that in the 1st case with marble + concrete you had zero surfaces that yielded thus you had high RT60. In the 2nd case you introduced a surface (ceiling) with material softer than all the other surfaces & acoustic waves hitting the ceiling died some & contributed to a smaller RT60. Amp_Nut schrieb: 3. You indicate that the space behind the speakers should be reflective, but experience shows that placing a TV there... even a Plasma / LCD is detremental to the sound ! Switch-it-on seems to have achieved success with a blank wall draped by a thin carpet ( Duree ). That provides good visual stimulation too.. That is correct - I meant to say that the wall behind & in between the speakers should be fully reflective. This enhances the midrange & the soundstage. Now. remember that a tube trap is at the max 20" in diameter - more like 16" if you have the space & often 12" in diameter. So, there is a controlled amount of reflective surface in between the speakers on the behind-the-speakers wall. How big/wide is a TV set + entertainment center? Likely wider than 20", correct? Plus, it has a lot of glass on it, correct? A tube trap does not have any glass reflective surface, correct? So, we have 2 different animals here where the effect of each cannot be correlated (atleast IMHO).

Bombaywalla,

With regard to making the corners reflective,
isn't this a given by nature(assuming hard surfaces all around) simpy because the audio sources create images of one anotehr.
I agree that the region immediately behind the speakers need to be deadened and the space between them should be reflective, but how reflective(varying in degrees..?) i donot know.

What about the region behind the listener?
Does it have to be refelctive or deadened, or does that depend on how close the listener sits to the back wall.

Debu,
keeping the speakers towards the wall would create an in accurate sound field due to the presence of the windows on one side and concrete on the other.
i faced a similar problem and partially sovled it by having two layers of curtains to deaden the effect of the window.
the window being more smooth than the concrete on the opposite wall is bound to be more reflective and the rough surface of the curtains help to some degree.
however, this is detremental in effect due to the absorption coefficient of the material of the curtain at 1kHz and above.

just my 2 cents..
feel free to correct me.

Sachi

Bombaywalla said:

there seems to be a slight misunderstanding here - I went back & re-read my post. Therein I wrote tube trap & not bass trap.

... & I thought that Tube traps were the same as Bass traps ! There. I learnt something. Thanks

Debu, putting the speakers with their back to the wall will be impractical, because that wall has the enterance door. The speaker wires wil not let the door open properly, and trip me as i enter.

Another thought given by Deaf, was that the window could be opened, during critical listning, keeping the heavy drapes in place . Should improve Image depth... and I am an Image freak

viren schrieb:

Hi Amp Nut, Setting up speakers in a room certainly requires quite a bit of work and experimentation. There are no hard-and-fast rules, just some guidelines. Since room shapes, and furnishings, vary so much, each location is unique and so is its arrangement.

correct! And, that's what my opening line was in my 1st post & I am cutting & pasting here:

Well, all the info I'm sharing with you is NOT absolute. With that understanding....

viren schrieb:

(A RT60 of 0.18 seconds is an absolutely dead room, one you can't even enter - imagine solitary confinement in a padded coffin!).

true! however, I calculated this from an equation in an AES standards document. The people who came up w/ this document must be thinking of something....
anyway, that equation is there FWIW.

viren schrieb:

I suggest a normal mix of reflective and absorptive surfaces - an upholstered sofa, a carpet, and curtains should suffice. Viren.

I disagree here. After having setup my room I can reassure you that these above cited items only work/add/enhance the formal room treatment that is put in place. If you take a casual approach as this, you'll get casual results. That might be just fine if that is your original intention.

Savyasaachi schrieb:

Bombaywalla, With regard to making the corners reflective, isn't this a given by nature(assuming hard surfaces all around) simpy because the audio sources create images of one anotehr.

well, you are smarter than me if you thought that it was obvious that the corners should be reflective! I certainly did not! I made them absorptive thinking that I'd get better bass control. I was wrong! After some tweaking I discovered what you have cited as obvious to you.

Savyasaachi schrieb:

I agree that the region immediately behind the speakers need to be deadened and the space between them should be reflective, but how reflective(varying in degrees..?) i donot know.

The wall behind & in-between the speakers, IMO, should be fully reflective. Right now I have bare wall behind & in between the speakers. I wanted to put some tube traps there but I have all the cabling running there as it is behind the rack.

Savyasaachi schrieb:

What about the region behind the listener? Does it have to be refelctive or deadened, or does that depend on how close the listener sits to the back wall.

The wall immediately behind the speaker should be fully absorptive. I found that sitting 6' away from the wall made the presence or absence of the tube trap much, much less. I have fully absortive tube traps immediately behind my chair but I've listened without them & the effect is minimal. If one cannot sit that far from the wall behind the listener, the tube trap will play a more important role.

The wall immediately behind the speaker should be fully absorptive.

How did you achive that Bombaywalla...through acoustic panelling or some other trick ?

bombaywalla schrieb:

Savyasaachi schrieb: What about the region behind the listener? Does it have to be refelctive or deadened, or does that depend on how close the listener sits to the back wall. The wall immediately behind the speaker should be fully absorptive. I found that sitting 6' away from the wall made the presence or absence of the tube trap much, much less. I have fully absortive tube traps immediately behind my chair but I've listened without them & the effect is minimal. If one cannot sit that far from the wall behind the listener, the tube trap will play a more important role.

I am assuming that you meant listener and not speaker in the first sentence.

The reason i want to know about this is that it is impossible for me to sit 6 feet away from the back wall, partly because i use the room for HT and mostly because my folks would not allow it .

So u mean to say that the wall should be completely deadened.
Right?

thereby no reflections from the back wall at all..this means no waves bouncing back and forth from the speakers.

bombaywalla schrieb:

Savyasaachi schrieb: I agree that the region immediately behind the speakers need to be deadened and the space between them should be reflective, but how reflective(varying in degrees..?) i donot know. The wall behind & in-between the speakers, IMO, should be fully reflective. Right now I have bare wall behind & in between the speakers. I wanted to put some tube traps there but I have all the cabling running there as it is behind the rack.

Oh!...i thought the opposite..
i figured that the wall immediately behind the speaker needs to be complelty absorbtive the the in bewtween space reflective..
You are saying that both the areas need to be reflective..

Thanks for that.
Correct me if i misunderstood it.

Sachi

Savyasaachi schrieb:

I am assuming that you meant listener and not speaker in the first sentence.

correct! I made a typo - I meant "listener" & not speaker.

Savyasaachi schrieb:

The reason i want to know about this is that it is impossible for me to sit 6 feet away from the back wall, partly because i use the room for HT and mostly because my folks would not allow it . So u mean to say that the wall should be completely deadened. Right? thereby no reflections from the back wall at all..this means no waves bouncing back and forth from the speakers.

the wall immediately behind the listener should be absorptive. The wall off to the sides should have varying degrees of absorption & reflection - just off to the sides there'll be more absorption & less reflection. As you go further & further away from the listener, there'll be less absorption & more reflection. Sort of a continuum from the full absorption that is immediately behind the listener.
Hope that this clarifies.

bombaywalla schrieb:

The wall behind & in-between the speakersbe reflective..

I can see where I might have messed you up! Sorry!
let's see if can explain this better - "in between the speakers along the wall behind them". Howzzat?
(Dead-nuts behind the speaker the wall should be absorptive).

abhi.pani schrieb:

The wall immediately behind the speaker should be fully absorptive. How did you achive that Bombaywalla...through acoustic panelling or some other trick ?

1stly, I made a typo - it should have read "The wall immediately behind the listener ......"

How did I achieve this? Tube traps.

Amp_Nut schrieb:

... & I thought that Tube traps were the same as Bass traps ! There. I learnt something. Thanks

Amp_Nut, what I found was that a bass trap was a smaller subset of a tube trap. The bass trap is a cylinder (of 12"/16"/20" or whatever you want it to be. Larger the diameter the lower the bass freq it can control) with the entire circumference to be absorptive. The tube trap, OTOH, is also a cylinder of your favourite diameter where the entire circumference is mid-bass absorptive + half the circumference is a midrange diffusor/reflector. It diffuses (usually) 400Hz & above - it is diameter of cylinder dependent.
So, with this tube trap, the user can rotate the cylinder to get a desired mix of absorption & reflection.
you remember that to get any absorption for acoustic velocity the panel needs to be half a wavelength off the wall surface?
well, since the tube trap is a cylinder & the reflective surface is facing out into the room, the reflective surface will be away from the wall = diameter of the cylinder. So, if you have a 12" cylinder, the half wavelength = 12", which means that 565Hz & above will be reflected. Similarly, if you have a 16" cylinder then 423.75Hz & above will be reflected & with a 20" cylinder, 339Hz & above will be reflected.

Bombaywalla,

There is nothing casual about my approach. I am as interested in getting good sound in a room from my equipment as you are. Normal home furnishings work the same way as purpose made acoustical products - just their absorption characteristics are a bit different. I had already mentioned that bass resonance problems may require special treatment.

If you would rather spend big bucks on custom hi-fi acoustical products that's your choice.

Viren.

viren schrieb:

Bombaywalla, There is nothing casual about my approach. I am as interested in getting good sound in a room from my equipment as you are.

ok, understood.

viren schrieb:

If you would rather spend big bucks on custom hi-fi acoustical products that's your choice. Viren.

There is a DIY receipe for tube traps which allows the user to make his/her own at home with materials available in the marketplace. Many, many people have successfully used this receipe.
One can also choose to spend one's money for custom hi-fi products.
Both options are open.
You assume too much when you wrote that I spent big bucks on custome hi-fi products. Nowhere in my posts did I write that.

Bombaywalla Said:

Amp_Nut, what I found was that a bass trap was a smaller subset of a tube trap. The bass trap is a cylinder (of 12"/16"/20" or whatever you want it to be. Larger the diameter the lower the bass freq it can control) with the entire circumference to be absorptive. The tube trap, OTOH, is also a cylinder of your favourite diameter where the entire circumference is mid-bass absorptive + half the circumference is a midrange diffusor/reflector. It diffuses (usually) 400Hz & above - it is diameter of cylinder dependent. So, with this tube trap, the user can rotate the cylinder to get a desired mix of absorption & reflection. you remember that to get any absorption for acoustic velocity the panel needs to be half a wavelength off the wall surface? well, since the tube trap is a cylinder & the reflective surface is facing out into the room, the reflective surface will be away from the wall = diameter of the cylinder. So, if you have a 12" cylinder, the half wavelength = 12", which means that 565Hz & above will be reflected. Similarly, if you have a 16" cylinder then 423.75Hz & above will be reflected & with a 20" cylinder, 339Hz & above will be reflected.

Thanks for your Very informative post. Ive soaked it all in.

Can you suggest suitable absorbtive & reflective materials that I can use for the Tube Trap ?

I guess the same acoustical absorbtive material will be used in Both the Bass and tube traps ?

Amp_Nut schrieb:

Thanks for your Very informative post. Ive soaked it all in.

good to read that it was useful info for you.

Amp_Nut schrieb:

Can you suggest suitable absorbtive & reflective materials that I can use for the Tube Trap ?

Meesa thinks you are ready to be turned loose onto this really good website:
http://www.geocities.com/jonrisch/a1.htm
http://www.geocities.com/jonrisch/basstrap.htm

hi ampnut,

my homegrown contribution that i use... a good bookshelf rack from ground level to almost ceiling height will do you a lot of good for diffusion. can be placed behind the speakers, or if you dont want to block the windows, place it on the wall behind you. will make it a 'cozy' den too a good thing to aim for i think is that no two facing walls should be treated the same. pretty obvious maybe but you asked for the obvious too so...

also something i picked up from somewhere or the other. ideal room dimensions, so you can change your room with false walls if need be.

option 1 - width=1.14xheight, length=1.39xheight

option 2 - width=1.60xheight, length=2.33xheight

option 3 - width=1.28xheight, length=1.54xheight


regards