How do I minimize dipole interference of ESL on the cheap?

woodsyi · « **on:** 6 May 2005, 06:19 pm »

Some of you may know that Jacobob was giving away a pair of Soundlab A-5 speakers. I was the lucky one who got them along with a pair of SVS subs, Sampson amp and a Marchand x-over. A-5 are smaller than A-3's but still huge. I have the electronics over at Soundlab getting updated. The panels were upgraded just two years ago. The A-5 are going in a very acoustically live room 18x22x8 -- tile floor, panelled walls over cinderblock and non-acoustic ceiling tiles. No furniture, yet, with wine bottles on one side wall. I plan to put corner bass traps but am looking for ways to deaden the back wall which is paneled. Sound lab suggests using Sallie http://www.soundlab-speakers.com/accessories.htm but I want to find a solution for less if I can. Any suggestions?

John Casler · « **Reply #1 on:** 6 May 2005, 07:30 pm »

Get some of these and make your own Sallie

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=3278&item=7319221992&rd=1

Although these "show" 12"x12"x4" the test says 24"x48"x4"

woodsyi · « **Reply #2 on:** 6 May 2005, 08:26 pm »

Thanks John,

I got the foam and 3 cans of spray glue. I am thinking of using 1/2" plywood in the middle to glue the foam on each side. Do you think the foam orientation would make a difference? If I want it 24" wide I would have to cut each in the middle to have horizontal wedges like Sallie. If I put vertical wedges, I can just glue on 2 on each side. What do you think?

John Casler · « **Reply #3 on:** 6 May 2005, 08:49 pm »

I have some of the 24"x48"x3" foam and it is cut so the wedges run the 24" width, so if the 4" is cut the same it should put them at running horizontally.

But, that said, I cant see either orientation having any distinct advantage I can think of.

I think these things look very cool, and would love to see your finished product.

What did you save $899?

woodsyi · « **Reply #4 on:** 6 May 2005, 09:05 pm »

Yes,

It is amazing what a little DIY can do. I guess that makes it about 650% markup. I just have to build a base for each "Sallie". I will post a picture once I get them built.

Thanks for the link.

Ethan Winer · « **Reply #5 on:** 7 May 2005, 03:56 pm »

John,

> Get some of these and make your own Sallie <

As a vendor of acoustic products I need to tread carefully here, but I am now certain of the facts so here goes:

I recently discovered that Foam by Mail uses fraudulent data to make their foam appear much better than it really is. I first discovered this last year when I bought and tested 16 pieces of their corner foam. The specs for this foam are identical to Auralex LENRDs, yet in lab tests they performed very poorly. They were so poor that I became suspicous and recently bought and tested genuine LENRD corners. The LENRDs measured much better than what Foam by Mail sells even though the specs are virtually identical.

Although my company has nothing to do with foam, and we hardly consider anything made of foam as competition, I believe it's important for guys like you and me, who offer advice on acoustics and treatment, to know the truth. If you'd like to see the lab data, email me and I'll gladly send it to you.

--Ethan

woodsyi · « **Reply #6 on:** 7 May 2005, 05:36 pm »

Oh, oh,

Ethan, I plan on getting a pair of mondos on stands for this room for bass. John's not taking customer away from you.

Wouldn't this foam by mail product still work in diffusing and absorbing some (maybe even at half their published spec) for attenuating back waves on a full ESL dipole speaker?

Ethan Winer · « **Reply #7 on:** 7 May 2005, 08:22 pm »

Woodsyi,

> John's not taking customer away from you. <

I never thought that. But I see so many people recommend Foam by Mail, having no idea that it's junk because the specs look pretty good (for foam, anyway), that I finally decided to say something.

> Wouldn't this foam by mail product still work in diffusing and absorbing some <

No, and that's my whole point. What they are selling is cheap packing foam cut to resemble real acoustic foam, and using fraudulent absorption data to make it appear better than it is. If you care enough to check this out, look at the specs Foam by Mail shows on their site, then compare that to the data on the Auralex web site. All of the FBM numbers are 0.01 higher or lower, to make it seem like they ran their own tests and got results similar to Auralex's. However, the corner foam we tested from both companies shows that Foam by Mail's is barely 1/3 as effective.

I'll also point out that we too were suckered by this scam! Last year, when we wanted to see how our products compare to corner foam with the same corner mounting, we bought from Foam by Mail for the same reason everyone else does: It claims the same specs as brand name acoustic foam but for much less money. So until I actually paid to test both foam products myself I assumed what everyone else assumes. The numbers differing by exactly 0.01 should have been a tip-off to me, because real-world tests vary by more than that even when testing the exact same material twice in a row in the same lab on the same day.

(By the way, just for accuracy, foam is an absorber, not a diffusor.)

--Ethan

John Casler · « **Reply #8 on:** 8 May 2005, 03:14 am »

Quote from: Ethan Winer

Woodsyi,

> John's not taking customer away from you. <

I never thought that. But I see so many people recommend Foam by Mail, having no idea that it's junk because the specs look pretty good (for foam, anyway), that I finally decided to say something.

> Wouldn't this foam by mail product still work in diffusing and absorbing some <

No, and that's my whole point. What they are selling is cheap packing foam cut to resemble real acoustic foam, and using fraudulent absorption data to mak ...

Hi Ethan,

Thanks for pointing that out. For the record, I have nothing to do with FBM and will now suggest some other (more reputable) vendor.

Not having any test equipment to do what you did, I did feel that the 3" foam was rather low in performance, when I could use my Infrared remote to fire right through it!!!

I used to set a piece in front of my equipment, and I could still use the remote, by simply firing it right through the foam.

That said, it still was not a way to determine how effective it is.

And I have always had to use additional layers of various materirals to acheive a reasonable result.

Again, thanks for pointing that out.

Ethan Winer · « **Reply #9 on:** 8 May 2005, 02:40 pm »

John,

> Not having any test equipment to do what you did <

Understood, and this is part of what perpetuates the problem. After all, even lousy foam will change the sound, and depending on how much someone puts up it could appear to be absorbing well. So first reflections might be reduced some, but not truly eliminated, etc.

> I could use my Infrared remote to fire right through it!!! <

Yeah, that's one indication!

--Ethan

John Casler · « **Reply #10 on:** 8 May 2005, 03:37 pm »

Ethan,

Do you know which foam companies "DO" live up to their published specs?

I saw you mentioned Auralex.

jgubman · « **Reply #11 on:** 8 May 2005, 04:01 pm »

Ethan, did you test only the FoamByMail corner "bass trap" pieces shown here?
http://www.foambymail.com/CornerSolutions.html

Did you do any testing on the plain vanilla wedges like the ones shown in John's photo?

ctviggen · « **Reply #12 on:** 9 May 2005, 05:46 pm »

So, what is the price difference? I was going to get foam by mail stuff, but I could buy Auralex stuff instead. Auralex does not list the price, though. Also, it's a bummer that you have to buy it from a dealer -- not because a dealer sells it, but because I'll now have to call the local dealers to ask them if they have what I want in stock, then go get the stuff. I'd rather just order it and have it delivered.

jgubman · « **Reply #13 on:** 9 May 2005, 05:55 pm »

Not too much more expensive:

http://www.musiciansfriend.com/srs7/g=home/search?q=AURALEX&d=tp

John Casler · « **Reply #14 on:** 9 May 2005, 06:20 pm »

Also look on e-bay

http://search.ebay.com/_W0QQfgtpZ1QQfrppZ50QQsassZmetroQ2dmusicQQssPageNameZDBQ3aOtherItems

Ethan Winer · « **Reply #15 on:** 9 May 2005, 06:42 pm »

John,

> Do you know which foam companies "DO" live up to their published specs? I saw you mentioned Auralex. <

The only two brands of foam I've ever measured are Foam by Mail and Auralex. So I can't vouch for any others. My guess is that most vendors are honest, and in the case of Auralex I know their chief engineer Jeff Szymanski. I can't imagine anyone with more integrity than Jeff. Likewise, I really doubt RPG would fake anything.

--Ethan

Ethan Winer · « **Reply #16 on:** 9 May 2005, 06:46 pm »

JG,

> did you test only the FoamByMail corner "bass trap" pieces shown here? <

Yes, that's what we tested.

> Did you do any testing on the plain vanilla wedges like the ones shown in John's photo? <

No, mostly because lab tests are very expensive! It's a big financial burden for a small company like RealTraps to test our own stuff, let alone test everything from every competitor. The only reason we tested Auralex LENRDs is because we found out after our original tests that Foam by Mail corner foam isn't what it claims to be.

--Ethan

woodsyi · « **Reply #17 on:** 9 May 2005, 07:09 pm »

Quote from: jgubman

Not too much more expensive:

http://www.musiciansfriend.com/srs7/g=home/search?q=AURALEX&d=tp

12 4" x 2' x 4' foam goes for $127 at FBM whereas 6 of the same size Auralex goes for $239 there or at http://truesoundcontrol.com/products/4SFW24.html. So, there is considerable price difference. I guess the old adage you get what you pay for applies here.

I will chalk it up as a learning experience and hope that FBM stuff at least is good for packing!

John Casler · « **Reply #18 on:** 9 May 2005, 07:35 pm »

Quote from: woodsyi

Quote from: jgubman
Not too much more expensive:

http://www.musiciansfriend.com/srs7/g=home/search?q=AURALEX&d=tp

12 4" x 2' x 4' foam goes for $127 at FBM whereas 6 of the same size Auralex goes for $239 there or at http://truesoundcontrol.com/products/4SFW24.html. So, there is considerable price difference. I guess the old adage you get what you pay for applies here. I will chalk it up as a learning experience and hope that FBM stuff at least is good for packing!

All may not be lost.

If (because of the low price) you ordered excess foam, you could probably incrase the effectiveness, by "tripleing" the thickness. This is easily done and it actually ends up being only "twice" as thick (not three times).

You simply place two of the foam strips "facing" each other (the wedge of one will fit into the valley of the other, and then mount the wedge out layer on those.

Hope that makes sense. I did that on my wall.

Also go to e-bay and search for "acoustic foam" to find online Auralex Dealers.