[Gordy]

Interesting, Thanks DSK   Have you ever tried closed cell or are you going by audiophile lore?  (Lore isn't the word I'm looking for) I'm asking in earnest!  My belief is that open cell/light weight foam is used only because that's what is available and or relatively inexpensive for the pro market, not due to any inheirent quality.  I believe the difference between open cell and closed cell is exactly the same as high loft fiber glass and high density fiber glass, both being the same material, high density is just that much more efficient.  I'd absolutely love to hear from others to correct me on this.  In practice, from what I've heard, it certainly does not reflect upper frequencies in any perceptable way!!!  It's merely more efficient.

Thanks,  Gordy

[John Casler]

John,

I have implemented and noticed a welcome sound improvement using your tweak. Previously, I used two piece of foam attached to each side of the speaker, parrallel to the speaker sides. I did not notice a upper bass increase at that time. I use now a 12'' deep rectangular box covered with thick carpet that fits the front of my 626R like a speaker grill. In my case, the bottom is closed as well, which I believe further increase the amount of directed bass (or delay the spreading of bass).

I have too much bass at this time and I wonder if you have tried with different depths for your tweak and noticed a difference in bass level?


My speakers are angled directly at the listening position, which I think is important, otherwise sound reflected from the inside box would reach my ears, somehow like a speaker diffraction.


Thanks again for sharing this tweak, ...

Hi Bruno,

I was wondering what a wood box would do, but felt it might, as you indicated, "add" hornlike reflection.

I essentially used the 626 speaker grill with 1) a large beach towel first layer, with a 2) second layer of the rubberized cell shelf liner.  The shelf liner being on the outside.

This was long enough to allow the beach towel and shelf liner to hang down on each side of the speaker and create a hood over the top.

The beach towel layer was absorbant/blocking HF, and the weight and density of the shelf liner worked a bit on the mids.

The two together seemed to have enough weight to also add a "very slight" bass "directive", without the mass to cause reflection.

Glad you found the tweak, and derivations of it, interesting

[DSK]

Interesting, Thanks DSK   Have you ever tried closed cell or are you going by audiophile lore?  (Lore isn't the word I'm looking for) I'm asking in earnest!  My belief is that open cell/light weight foam is used only because that's what is available and or relatively inexpensive for the pro market, not due to any inheirent quality.  I believe the difference between open cell and closed cell is exactly the same as high loft fiber glass and high density fiber glass, both being the same material, high densi ...

When I moved into a new home a few years back I read everything I could find on listening room acoustics. I had some great bookmarks that actually explained why the open-cell foam is far better for air borne absorption than closed-cell foam but lost them when my machine crashed. Much of the stuff was not written by people in the hifi industry but by acousticians/engineers etc. From memory, it was to do with the way the sound wave passes through the walls of the open cell pockets of the open-cell foam and is converted to heat as it does so (friction?). Dependent on the thickness and density of the open-cell foam, some sound will transmit out the other side of the foam panel, but less than what entered it. The difference is a combination of what was absorbed on the way through all the air pockets and what was reflected off the front surface. In contrast, closed-cell foam tends to reflect much more off the front surface and is more like a solid barrier than a filter as the sound is trying to pass through a solid mass rather than a series of air pockets with thin walls.

The denser open-cell foam is, the better it is at absorbing low frequencies (the more powerful ones) but the worse it is at absorbing higher frequencies (much weaker ones). For a given thickness, higher density open-cell foam is less air and more solids, much harder for the weaker frequencies (higher frequencies) to penetrate ...so, more are reflected instead. With closed-cell foam, there is already a far greater solids to air ratio as it doesn't have the air pockets. So, sound is less able to enter it and is reflected off the surface instead. To use an extreme analogy, it is the difference between trying to drive your car through a corn field versus through a brick wall. (a clumsy analogy I know as it implies impact, but if you think of the car as a soundwave you will get my drift).

Sorry my explanation is not very scientific but hopefully it helps.

[BrunoB]

Hi Bruno,

I was wondering what a wood box would do, but felt it might, as you indicated, "add" hornlike reflection.
...

I made a quick bass level measurement yesterday night. I used Stereophile CD bass tones (20 to 200Hz) and a RadioShack sound level meter.  With the 12'' deep box in front of my speaker (see my previous post),  I measured at the listening position an increase of 7 db at 200 Hz .  The effect decreases as the frequency goes down, below 100 Hz the sound levels are about the same.

Bruno

[John Casler]

Hi Bruno,

I was wondering what a wood box would do, but felt it might, as you indicated, "add" hornlike reflection.
...

I made a quick bass level measurement yesterday night. I used Stereophile CD bass tones (20 to 200Hz) and a RadioShack sound level meter.  With the 12'' deep box in front of my speaker (see my previous post),  I measured at the listening position an increase of 7 db at 200 Hz .  The effect decreases as the frequency goes down, below 100 Hz the sound levels are about the same.

Bruno

Hi Bruno,

Are those corrected (Rat Shack) measurments?  See chart below:

20Hz add 7.5
25Hz add 5
31.5Hz add 3
40Hz add 2.5
50Hz add 1.5
63Hz add 1.5
80Hz add 1.5
100Hz add 2
125Hz add .5
160Hz add -.5
200Hz add -.5

[lonewolfny42]

John,

Could you post a picture of this ? Thanks !! [/list:u]

     

Wasn't it Tommy who said "see me", "hear me"????

Well in this case it is "ONLY" hear me, but yes, I'll dig up my digital camera and post a pic or two. (which will also show my 4 LARGER Subs  stacked on top of each other)

Bump....

Plus I'd like to see that Sub Stack.....thanks John !! [/list:u]

[BrunoB]

Are those corrected (Rat Shack) measurments?

John,

these are uncorrected. Here is the bass response at my listening position with and without tweak (RS uncorrected):

Freq       normal    with tweak      diff
-------------------------------------------
1000          78            76           -2
 200          76            83           +7
 160          80            83           +3
 125          79            81           +2
 100          76            77           +1
  80          77            77            0
  63          76            76            0
  50          72            73           +1
  40          75            76           +1
  31.5        67            68           +1
  25          63            62           -1
  20          59            60           +1
----------------------------------------

Note that if you look only at the difference, the correction does not matter.

Bruno

[John Casler]

John,

Could you post a picture of this ? Thanks !! [/list:u]

     

Wasn't it Tommy who said "see me", "hear me"????

Well in this case it is "ONLY" hear me, but yes, I'll dig up my digital camera and post a pic or two. (which will also show my 4 LARGER Subs  stacked on top of each other)

Bump....

Plus I'd like to see that Sub Stack.....thanks John !! [/list:u]

OK,

After all this time I finally got a chance to snap a pic of this tweak.

I will post more when I get back, but remember this is not a "permanent" tweak and can be placed on the speakers for "serious" listening.

It simulates a good percentage of a LEDE room simply by blocking absorbing the dispersed sonic radiation that would notmally be bouncing all over your room.

This includes cabinet resonances.

The "LEDE sonic overcoat" sticks out in front of the cabinet at least 8"-10"

SORRY FOR PICTURE QUALITY

More later...

[lonewolfny42]

OK,

After all this time I finally got a chance to snap a pic of this tweak.

I will post more when I get back......

Thank You John !!![/list:u]

A picture's worth a thousand words....... [/list:u]

[BrunoB]

OK,

After all this time I finally got a chance to snap a pic of this tweak.

I will post more when I get back, but remember this is not a "permanent" tweak and can be placed on the speakers for "serious" listening.

It simulates a good percentage of a LEDE room simply by blocking absorbing the dispersed sonic radiation that would notmally be bouncing all over your room.

This includes cabinet resonances.

The "LEDE sonic overcoat" sticks out in front of the cabinet at least 8"-10"

 ...

John,

wouldn't it be better to cover the inner sides of your "tweak" with foam or other sound adsorbing material?

Interesting to see that your tweak looks quite different (bigger) than my implementation. I will try post a pict this weekend.

Bruno

[BobMajor]

Thanks for your tweak John (and all your other helpful posts).
I recently took delivery of a pair of 626R Signature speakers. I'm expecting the power amps in a few days.
Looking at your picture it seems that you have a considerable distance from the speaker sides to the wrap. Is this necessary or could the wrap lie against the sides of the speakers? Also it looks like the tan material which I suppose is the shelf liner is on the inside before the towel. Is this correct?
I bought a pair of 6 foot chenille throws to use (they look nice).
In one of your first posts in this thread you were sliding the wrap about six inches forward. In a latter post you were saying about 10 inches.
Did the increased distance help?
Best wishes,
Bob Major

[doug s.]

John,

wouldn't it be better to cover the inner sides of your "tweak" with foam or other sound adsorbing material?

Interesting to see that your tweak looks quite different (bigger) than my implementation. I will try post a pict this weekend.

Bruno

brun, that was exactly my thought - get the absorbing stuff on the inside.  as i said earlier, a "hood" made of 2" (or thicker) foam would be great for any speaker, imo...  watkins echo muffs were a u-shaped foam device made to stand on the floor, w/the speaker inside the "u"...  

doug s.

[John Casler]

John,

wouldn't it be better to cover the inner sides of your "tweak" with foam or other sound adsorbing material?

Interesting to see that your tweak looks quite different (bigger) than my implementation. I will try post a pict this weekend.

Bruno

Hi Bruno,

Yes, you are 100% correct, I actually had two additional (multi and different color fluffy bath towels on the inside, but removed them for the picture.

The shelf liner is best as a "layer" between layers of something less reflective.

The "size" of the tweak width wise is because of the non-reflective (covered) board I use on the top.  The height is caused by the stack of rubber covered weights that it sits on top of.

I have over 70# sitting on each 626R and another 90# dumbbell sitting on the LARGER sub.

But do use either an acoustic foam layer or a folded fluffy towel on the "inside" layer closest to the speaker.

[John Casler]

Thanks for your tweak John (and all your other helpful posts).
I recently took delivery of a pair of 626R Signature speakers. I'm expecting the power amps in a few days.
Looking at your picture it seems that you have a considerable distance from the speaker sides to the wrap. Is this necessary or could the wrap lie against the sides of the speakers? Also it looks like the tan material which I suppose is the shelf liner is on the inside before the towel. Is this correct?
I bought a pair of 6 foot chenille throws to use (they look nice).
In one of your first posts in this thread you were sliding the wrap about six inches forward. In a latter post you were saying about 10 inches.
Did the increased distance help?
...

Hi Bob,

The inside layer "can" certainly be right up against the sides of the cabinet, and probably would be more effective if they are.

I have had "MANY" incarnations of this and most of them were "multi-layered" with shelf liner, soft blankets, Fluffy Towels, and Cardboard.

The best one had foam on the inside, then a towel, then cardboard, then shelf liner, then a folded blanket.

But it was too ugly to photograph (as if this isn't )

As far as the distance, I suggest you "experiment".  My movint it forward was just that.  With the 626R woofer, which is the higher dispersion of all the drivers, I felt moving it a bit more forward would block ceiling reflections a bit more.