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post #61 of 86 Old 02-08-2011, 06:39 AM
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Quote:
Originally Posted by localhost127 View Post

what is audyssey or eq going to do if you're sitting in a -30dB null? or have 500ms modal ringing at 80hz??

Bass traps cant do much to the nulls either. If you have a -30db null you need to try a different location for the sub. It would be pointless to try to fix a -30db null either using passive or active correction.

Audyssey and Anti-Mode work in both time and freq. domain. So they can reduce the ringing by increasing the decay time. If you want to correct over 80Hz use a higher cross over. 80Hz is not set in stone. Anti-Mode can correct up to 144Hz. I use a cross over at 120Hz. No that does not sound local.

I didnt use a bigger triangle because I didnt want to buy a truck load of 703 panels. The size I used have been widely used and proven to be effective. So I didnt have to do my research in acoustics to find out why it works. This is the basic idea of research. If someone has already done prior work and has provided proof that it works, people use them. It is a waste of time to reinvent the wheel. Using already proven work is not following it blindly.

Room correction is not done for 1 spot. Audyssey MultEQ allows measurements at 6 locations. XT allows 8 locations. New Anti-Mode also allows multiple locations.

Like I said before, you are wasting time arguing about things that are well documented. You also seem to argue without having tried either passive or active correction. You may try the depth/thickness you feel is right, with the material of right density and see if it works. I don't have the physical strength to do such DIY experiments. So I follow what others have proven to be effective and economical solutions. if I look back, I cant believe I cut all those panels and stacked up. I have 3 such stacks in my room at 3 corners.

This is not a thread for people to learn everything about bass traps. That is why there is that dedicated thread. In a short thread like this people have provided enough information for others to get started.

So go to that thread if you need mode information.
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post #62 of 86 Old 02-08-2011, 06:46 AM
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BTW I dont think room correction will deal with reflections. No one claims that it does. It is recommended that in addition to room correction, people use panels at the first reflection points. This is more economical and less effort compared to filling the room with panels which is not practical and expensive.

Most of your questions are answered at that thread. If you want to know how room correction works, you have to read the paper by Chris and others. Go to the sticky Audyssey thread in the receivers forum. Someone has posted links to such papers.

Like I said before, this is not the thread to argue about the pros and cons of passive and active correction. Both have their merits and it is all well documented. You would benefit more by spending your time reading the Audyssey and dedicated HT thread.
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post #63 of 86 Old 02-08-2011, 06:52 AM
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Originally Posted by dissonance79 View Post

Um so what do I use to cut into triangles to put in the corners and stack 8 feet to the ceiling?

I guess you didnt read my posts. You can buy powered kitchen knife at walmart or local departmental store for $20. I just checked the name. Proctor Silex
I would suggest a more powerful one. This would will not cut it like butter. You would need some elbow grease.
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post #64 of 86 Old 02-08-2011, 07:12 AM
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Quote:


Bass traps cant do much to the nulls either. If you have a -30db null you need to try a different location for the sub. It would be pointless to try to fix a -30db null either using passive or active correction.

Nulls can be addressed by bass trapping by reducing their relative significance.

Quote:


Audyssey and Anti-Mode work in both time and freq. domain. So they can reduce the ringing by increasing the decay time.

Time and frequency based automated equalization devices may reduce modal ringing by reducing the decay time.


Also, bass trap effectiveness can be increased by placing the material at the quarter wave point off the wall. So, if one only had "x" inches of fiberglass, placing that at the point at which the waveform velocity is at it's highest point. By placing the porous material a quarter wavelength from the wall, it will have the maximum absorbing effect because the particle velocity is maximum. Porous absorbers work by converting air motion to heat, so they work best at the point of minimum pressure, and maximum velocity.

Generally, pressure and velocity are 180 degrees out of phase. The boundary wall forms a diaphragmatic panel absorber, or a panel type trap...whereby the physical motion of the wall, excited by the LF in room, changes the air motion into structural motion, thereby damping the LF characteristics of the room. This type of trap, a diaphragmatic panel trap, needs to be at maximum pressure, minimum velocity.

The resultant point is, the effectiveness of a given thickness of material for a bass trap is increased significantly by spacing it of the wall.




Good luck

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post #65 of 86 Old 02-08-2011, 07:13 AM
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Quote:
Originally Posted by Mupi View Post

Bass traps cant do much to the nulls either. If you have a -30db null you need to try a different location for the sub. It would be pointless to try to fix a -30db null either using passive or active correction.

i dont think you understand the topic quite as well as you would like. do you even understand how nulls are formed? either modal, or comb-filtered off the rear wall (for example) ???

you really need to re-read the master acoustics thread in this forum, after making such a comment.

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Originally Posted by Mupi View Post

Audyssey and Anti-Mode work in both time and freq. domain. So they can reduce the ringing by increasing the decay time.

a reduction in decay time is a reduction in modal ringing. i dont think you understand the vocabulary.

also, please detail to me how an eq can effect time domain issues that are completely unknown to the system until the sound leaves the speaker -- how can eq modify a signal that has already left the speaker?

modal ringing / decay time is determined by the room, which is determined by the room AFTER the signal has left the source/speaker

if the eq decreases the output at that freq, then by all means yes there will be less modal ringing...but that's not the same argument as saying eq/room correction cures modal ringing issues in a room.

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Originally Posted by Mupi View Post

If you want to correct over 80Hz use a higher cross over. 80Hz is not set in stone. Anti-Mode can correct up to 144Hz. I use a cross over at 120Hz. No that does not sound local.

im talking tiem domain, not frequency response. what does crossover have to do with decay time?

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Originally Posted by Mupi View Post

I didnt use a bigger triangle because I didnt want to buy a truck load of 703 panels. The size I used have been widely used and proven to be effective. So I didnt have to do my research in acoustics to find out why it works. This is the basic idea of research. If someone has already done prior work and has provided proof that it works, people use them. It is a waste of time to reinvent the wheel. Using already proven work is not following it blindly.

every room is different. there are some general guidelines to follow, and that is what is discussed in the threads --- but blindly assuming some small corner chunks is going to have the same results as other people (in different rooms) is rubbish. every room is different and has different issues to correct. i dont think anyone has ever advocated *against* corner traps ... but to assume small corner traps are all you need to fix modal room issues is laughable.

the fact that you think you can follow a solution that was based on a certain set of design requirements for one room, and apply it to your room is blind. you dont need to reinvent the wheel, but people need to know the issues of their room before spending money and time (diy or not) doing treatments.

you don't just randomly build a solution without knowing what your fundamental problems are / design requirements.


Quote:
Originally Posted by Mupi View Post

Room correction is not done for 1 spot. Audyssey MultEQ allows measurements at 6 locations. XT allows 8 locations. New Anti-Mode also allows multiple locations.

cool. did you do this for an 1-4inches in every axis of your listening position? 6 or 8 measurements isn;t going to correct comb-filtering in the geometric space that your head can move around at the listening position.

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Originally Posted by Mupi View Post

Like I said before, you are wasting time arguing about things that are well documented. You also seem to argue without having tried either passive or active correction.

without trying? my room is full of oc703...please stop being so ignorant. the only comment i made in this thread is as you build increasingly deeper traps, you need to use less dense materials.

please detail to me what im wasting my time with arguing? you cant even point out what i am saying that goes against what Ted White (?) is saying. please be specific if you're going to repeat this nonsense. again, what is it that you think i am in disagreeance on vs the experts?


Quote:
Originally Posted by Mupi View Post

You may try the depth/thickness you feel is right, with the material of right density and see if it works. I don't have the physical strength to do such DIY experiments. So I follow what others have proven to be effective and economical solutions. if I look back, I cant believe I cut all those panels and stacked up. I have 3 such stacks in my room at 3 corners.

so then why are you agueing me about my comment that as you start to build very deep traps, you need to use less dense material?
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post #66 of 86 Old 02-08-2011, 07:16 AM
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Originally Posted by Mupi View Post


I guess you didnt read my posts. You can buy powered kitchen knife at walmart or local departmental store for $20. I just checked the name. Proctor Silex
I would suggest a more powerful one. This would will not cut it like butter. You would need some elbow grease.

I did but I was referring to what material to use because that guy was confusing me with his talk of density. As someone has since mentioned, the 703 is tried and true so no reason to overthink it and start analyzing density.
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post #67 of 86 Old 02-08-2011, 07:22 AM
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Quote:
Originally Posted by dissonance79 View Post

I did but I was referring to what material to use because that guy was confusing me with his talk of density. As someone has since mentioned, the 703 is tried and true so no reason to overthink it and start analyzing density.

that's fine.
there are many tutorials/etc on gik and realtraps web sites.
they'll explain the basics in a much better form than forum commentary.

you are asking what material to use but you haven't given your design requirements yet.

e.g. how much space do you have to work with? again, oc703 is common density for people who can't take up much real estate...but if you were building huuuuge deep corner traps/chunks, you could use the cheap pink fluffy stuff. and if you took a moment to understand how the insulation works in the first place, you would see that by bringing the absorption further away from the wall/corner, you're bringing it closer to the 1/4wavelength of the LF...hence, you're improving absorption. and the caveat was, as you continue to build very deep traps, you want to use less dense material.

check out real traps/gik/ethan's acoustics page that he commonly links to. it's very worthwhile and explained in easy to understand terms.

oc703 is more expensive than similiar density rockwool/mineral wool, but much easier to work with. if you have price constraints, you could buy cheap pink fluffy fiberglass insulation for the corner and have huge/deep traps in the corners, and then use 703 for wall panels, reflection points, cloud, rear wall, etc... this is why i asked the question. there's many variables here that need to be given some thought instead of blindly providing a '1 size fits all' solution.
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post #68 of 86 Old 02-08-2011, 07:24 AM
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Quote:
Originally Posted by Mupi View Post

BTW I dont think room correction will deal with reflections. No one claims that it does. It is recommended that in addition to room correction, people use panels at the first reflection points. This is more economical and less effort compared to filling the room with panels which is not practical and expensive.

if room correction can't deal with reflections (read: room correction cant deal with any aspect once the signal has left the speaker) -- then how do you proclaim eq/room correction helps with modal ringing/decay times???


why are you telling me to read the documentation when you haven't a firm grasp of it yourself? -- and yet you attempt to speak on authority on the issue, all while making fundamental mistakes.
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post #69 of 86 Old 02-08-2011, 07:27 AM
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Quote:
Originally Posted by FOH View Post

Nulls can be addressed by bass trapping by reducing their relative significance.


..
..
..

The resultant point is, the effectiveness of a given thickness of material for a bass trap is increased significantly by spacing it of the wall.




Good luck

excellent post. the only thing i commented on (which seemed to spark confusion / this whole debate) ... was that if you are building deeper and deeper traps (to get the absorption closer to the 1/4wavelengths), less dense material should be used.

somehow, i think Muni is becoming confused that I somehow think 703 is not effective??? which is strange, considering it's all i use
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post #70 of 86 Old 02-08-2011, 11:02 AM
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Quote:
Originally Posted by Mupi View Post

Yep GIK panels are ridiculously expensive. I could buy them if I am a ball player.

I bought the 703 panels from a local insulation dealer. It is a lot cheaper to buy the 703 from a local company than get it online. They come in a pack of 12 if I remember correctly. If you order by phone, make sure you tell them it is for HT (yes they know people use it for HT) and tell them to deliver a box with the panels in good shape. The box is basically cardboard wrapped around. First time I struggled by getting the panels in my Civic! Next time I asked them to deliver a box. They charged $20 to deliver.



You can buy the Gilford of maime cloth to cover the panels. Actually the fabric is more expensive than the 703 panels! Some say that felt cloth is also as acoustically transparent as the Gilrford of maime cloth. I didnt cover them as no one visits my house :-)

I dunno, maybe it's just me, but part of a room treatment is the aesthetics of panels. These to me give me an eye sore. I guess you could drape some cloth over it, but would you really be saving much money and time versus buying it from ATS or some other supplier? I guess it really comes down to, how much is your time worth to you really and whether you enjoy putting together paneling.
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post #71 of 86 Old 02-08-2011, 01:49 PM
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Has anyone ordered custom panels from Audimute using their own custom pictures?

http://www.audimutesoundproofing.com...ass-traps.aspx

I'm wondering how good the quality is and if they turned out nice?
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post #72 of 86 Old 02-08-2011, 02:16 PM
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Originally Posted by jonLavs View Post

Has anyone ordered custom panels from Audimute using their own custom pictures?

http://www.audimutesoundproofing.com...ass-traps.aspx

I'm wondering how good the quality is and if they turned out nice?

2'X2' for $160???!!!! OUCH! That's too rich for my blood!

Dumb enough to spend lots of cash on this junk!
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post #73 of 86 Old 02-08-2011, 02:33 PM
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Originally Posted by flyng_fool View Post

2'X2' for $160???!!!! OUCH! That's too rich for my blood!

Right, but it has a picture of your choice printed on it or a picture from their gallery.

Plus, how much was your HT system combined? Isn't this just part of the cost of a HT?
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post #74 of 86 Old 02-08-2011, 03:09 PM
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Don't get me wrong, it looks really nice. But at $160 per, that would break the bank in short order. I'm a cheapo AV nut. I buy used or refurbed. Rarely do I buy new. My DTS-10 kit was a HUGE splurge for me. If that thing wasn't in kit form, I would never have been able to own it.

Plus, I'm a DIY weirdo. If I can do it myself, I will. And when it come time for panels I'll definitely be making my own. I figure it'll run me in the neighborhood of $40 each.

Dumb enough to spend lots of cash on this junk!
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post #75 of 86 Old 02-08-2011, 07:00 PM
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Quote:
Originally Posted by localhost127 View Post

i dont think you understand the topic quite as well as you would like. do you even understand how nulls are formed? either modal, or comb-filtered off the rear wall (for example) ???

I do know that ringing is reduced by reducing the decay time. It was a slip of the tongue and it can happen to anyone.

If you want to know how Audyssey or Anti-Mode work in freq. and time domain to control the decay time, you have to read the research. It is not such a trivial topic and I would not pretend to know the answer.

Comb-filter is a fancy word. Null can be explained simply as phenomenon where the incident and reflected waves are out of phase by 180, completely canceling each other. At other angles they wont completely cancel each other so it wont be a null but the amplitude would be lower. Of course when the waves reinforce each other you get a peak. So it is not as complicated as words like comb-filter make it sound like complicated.

Corner bass traps are used since the sound pressure fluctuations is high in the corners. Go to a corner in a room and you will notice how much amplified the bass is.

It is not practical to check the wavelength of every frequency to figure out where to put the panel. That is why people use the golden rule of 38%. if you sit at 38% of the length of the room from either wall the effect would be the least. Then you could tackle the reflections by placing the panels at the reflection points on the side. These simple thumb rules would get rid of a lot of problems.

Anyway... I really dont have anything else to add to this argument. If you have already filled your room with OC703 then you may give more insight to others in this thread who are asking for information :-)
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post #76 of 86 Old 02-09-2011, 05:35 AM
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Quote:
Originally Posted by Mupi View Post

If you want to know how Audyssey or Anti-Mode work in freq. and time domain to control the decay time, you have to read the research. It is not such a trivial topic and I would not pretend to know the answer.

im just curious how eq/anti-mode can affect the signal once it has left the speaker. im not sure why the burden should be on me to look up this information; you're the one making the performance/capability claims - the burden should be on you to provide data to back up those claims.

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Originally Posted by Mupi View Post

Comb-filter is a fancy word. Null can be explained simply as phenomenon where the incident and reflected waves are out of phase by 180, completely canceling each other. At other angles they wont completely cancel each other so it wont be a null but the amplitude would be lower. Of course when the waves reinforce each other you get a peak. So it is not as complicated as words like comb-filter make it sound like complicated.

comb-filtering is a very simple concept to understand from a high-level perspective. i'm not sure why you are putting comb-filtering in the light of some hyper advanced topic... this video details it clearly....

http://www.realtraps.com/video_comb.htm

can you detail why you stated above that bass traps *cannot* help treat nulls? you stated:

"Bass traps cant do much to the nulls either. If you have a -30db null you need to try a different location for the sub. It would be pointless to try to fix a -30db null either using passive or active correction."

can you please clarify this statement?

Quote:
Originally Posted by Mupi View Post

Corner bass traps are used since the sound pressure fluctuations is high in the corners. Go to a corner in a room and you will notice how much amplified the bass is.

your ears are sensitive to sound pressure levels, yes ,,, but OC703 (porous absorption) doesn't work based on pressure of the wave, it works based on velocity of the air particle. it's best to hit the corners but i think you're still slightly confused on how porous absorption works.

Quote:
Originally Posted by Mupi View Post

It is not practical to check the wavelength of every frequency to figure out where to put the panel.

it certainly is if you have an issue at a particular frequency that you are trying to tame...then placement of the porous absorption closest to the 1/4wavelength of that frequency will be much more effective...and with very thick traps...you can hit a larger range of frequencies close to 1/4wavelength --- hence why you build deep traps or space with a large air gap from the wall.

Quote:
Originally Posted by Mupi View Post

That is why people use the golden rule of 38%. if you sit at 38% of the length of the room from either wall the effect would be the least. Then you could tackle the reflections by placing the panels at the reflection points on the side. These simple thumb rules would get rid of a lot of problems.

you say above you think comb-filtering is a fancy word (and basically reject it) --- yet you then go on to claim how important the 3/8s rule is? hmm.



Quote:
Originally Posted by Mupi View Post

Anyway... I really dont have anything else to add to this argument. If you have already filled your room with OC703 then you may give more insight to others in this thread who are asking for information :-)

this whole thing started because you kept claiming i was making statements in disagreeance with some of the experts. i asked you to please clarify what exactly i was posting that went against the grain, because as far as i know nothing ive stated is out of the ordinary.

and i did help the OP because the cheapest and still highly effective bass trap is very deep (12"+ thick) filled with loose pink fluffy stuff. the original post of this thread, he asked what was the least expensive route to take. super deep pink fluffy traps from floor to ceiling (and any other 2D/3D boundary in the room) will be highly effective from a cost/performance ratio. most people cannot afford the luxury of eating up so much real estate with thick traps, so they use more dense material like rigid fiberglass (and then space that from the wall).
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post #77 of 86 Old 02-09-2011, 06:39 AM
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you say above you think comb-filtering is a fancy word (and basically reject it) --- yet you then go on to claim how important the 3/8s rule is? hmm.

No one rejected "comb-filtering". I just said it is a fancy word. Some people may not understand such technical terms. But the phenomenon can be explained in simpler terms like I tried so most people can understand.

Do I understand thoroughly the concept behind how a DLP projector works, or how a LCD TV works or a speaker works? I dont. I just use them. Same way I use Audyssey and Anti-Mode. I buy a product and try it. If I am happy with its performance as claimed by the manufacturer I keep it. If not I either sell it or return it. I dont spend time trying to understand all the research that went into a product. It would be a futile attempt.
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post #78 of 86 Old 02-09-2011, 06:58 AM
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Originally Posted by Mupi View Post

No one rejected "comb-filtering". I just said it is a fancy word. Some people may not understand such technical terms. But the phenomenon can be explained in simpler terms like I tried so most people can understand.

so i assume you will not be quoting me or telling me what i said that was in disagreeance with the experts? ive asked repeatedly but to no response. if i am stating something wrong i want to be corrected so im not misrepresenting facts/data to others in the future. if not, let's move on.
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post #79 of 86 Old 02-09-2011, 01:04 PM
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I certainly did not read through this lengthy thread, but I did get the gist of it, which is around treating room corners with 1", 2" or 4" fiberglass panels in the corner and expecting low frequency absorption. Of course, this does not work because velocity absorbers, when mounted to a boundary, are only effective down to the frequency equaling a 1/4 wavelength of their thickness. A 100 Hz. would mean a 1/4 wavelength about 2' 10" out from the wall.

To be effective at distances less than this would require a different discipline, such as pressure, or diaphragmatic absorbers. Our company uses both in some of our products to cover a wider bandwidth in a shallow depth.

Norman Varney
A/V RoomService, Ltd.
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post #80 of 86 Old 02-09-2011, 08:24 PM
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Quote:
Originally Posted by Norman Varney View Post

I certainly did not read through this lengthy thread, but I did get the gist of it, which is around treating room corners with 1", 2" or 4" fiberglass panels in the corner and expecting low frequency absorption. Of course, this does not work because velocity absorbers, when mounted to a boundary, are only effective down to the frequency equaling a 1/4 wavelength of their thickness. A 100 Hz. would mean a 1/4 wavelength about 2' 10" out from the wall.

To be effective at distances less than this would require a different discipline, such as pressure, or diaphragmatic absorbers. Our company uses both in some of our products to cover a wider bandwidth in a shallow depth.

Norman Varney
A/V RoomService, Ltd.

Do you mean to say that the thickness of the fiberglass panels should be 1/4th the wavelength of the troublesome frequency or the distance of the panel from the wall should be 1/4th the wavelength of the frequency. Could you please clarify.

Do you sell the diaphragmatic absorbers and if so how expensive are they?
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post #81 of 86 Old 02-09-2011, 08:32 PM
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I looked at your FRP product and noticed that at 50Hz the absorption coefficient is less than 0.2 and there is also a note that the FRP is effective down to 63Hz.

Is this 20% absorption considered enough? and what about much lower frequencies like 30 or 40Hz. What kind of solution you offer for lower frequencies and how close can they be placed to the wall.
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post #82 of 86 Old 02-09-2011, 08:39 PM
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I looked at the pricing. $499 for a 35" corner trap! No thanks. I would be broke even if I have to fill up one corner floor to ceiling!

Looks like only ball players can afford them. Ironically ball players are interested in something else!

$499 for this?
http://www.avroomservice.com/product....php?img=1.jpg

Is that a regular insulation material or something proprietary?
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post #83 of 86 Old 02-09-2011, 09:18 PM
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A good link about corner traps. I used the 24" design

People who sell expensive bass traps always will say that the corner DIY traps will not work.

http://forum.studiotips.com/viewtopic.php?f=8&t=535
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post #84 of 86 Old 02-09-2011, 09:24 PM
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Yet another ridiculously expensive product. 2 pieces of 2'x2'x2' trap is $349
http://www.acousticsaudio.com/PROD/A...gory_Code=BASS

That web site above has compared the DIY 703 trap and it has pretty much same effectiveness. For $349 you could do all corners in your room!
http://forum.studiotips.com/viewtopic.php?f=8&t=536
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post #85 of 86 Old 02-10-2011, 05:28 AM
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Quote:
Originally Posted by Mupi View Post

Do you mean to say that the thickness of the fiberglass panels should be 1/4th the wavelength of the troublesome frequency or the distance of the panel from the wall should be 1/4th the wavelength of the frequency. Could you please clarify.

so did you completely ignore all of my commentary since page 1 regarding the reason for very deep traps??? porous absorption works by converting kinetic energy from particle velocity into heat as it passes through the insulation via gas flow properties of that particular material.

if you place a bass trap flat against the wall, it will do very little to tame LF. that is why an air gap is generally required...as you space the panel (absorption) away from the wall (where pressure is greatest) to an area of greater particle velocity - closer to 1/4wavelength of trouble frequencies.

and again - as i stated from page 1, once you start making very deep traps (> 12" deep)...then you need to start using lower density material (e.g. pink fluffy stuff).




Quote:
Originally Posted by Mupi View Post

A good link about corner traps. I used the 24" design

People who sell expensive bass traps always will say that the corner DIY traps will not work.

http://forum.studiotips.com/viewtopic.php?f=8&t=535

who cares what people who sell treatments are saying - you can understand how they work and how they are placed to be most effective on your own, for free. then you can choose to build your own if you have the time, materials, tools, etc... or you can chose a commercial product.

the corner traps do work, but you really should have done a 34" face. by going with the larger triangles, you're making the trap deeper, thus bringing the absorption further away from the wall. it's the same reason why if you are building normal bass trap panels, you straddle them in the corner with a larger air gap.

your 24" corner traps will help with decay time and maybe help the freq response in some aspects, but if you want to tame LF you really need much deeper traps which are spaced further / away from the walls - or use pressure based absorbers.


Quote:
Originally Posted by Mupi View Post

Yet another ridiculously expensive product. 2 pieces of 2'x2'x2' trap is $349
http://www.acousticsaudio.com/PROD/A...gory_Code=BASS

That web site above has compared the DIY 703 trap and it has pretty much same effectiveness. For $349 you could do all corners in your room!
http://forum.studiotips.com/viewtopic.php?f=8&t=536

is all of that really necessary??
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post #86 of 86 Old 02-10-2011, 06:19 AM
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Let it go already........ Nobody really cares all that much!


Dumb enough to spend lots of cash on this junk!
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