Cornwall Backboard Foam

[Kenhorns]

Currently refinishing my '79 Cornwalls. Found some 1/8" white high density foam and decided to seal the joint between the backboard and cabinet. Cut foam into 1" wide strips, mitered the ends, and mounted in a picture frame fashion around the inside edges of the backboard. Used Elmer's White School Glue to glue the foam to the unfinished backboard wood as my pretesting proved Minwax Furniture Refinisher (stripper) with steel wool will remove the glue in case I wish to undue this addition in the future.

Now for the Technical Question; Have I messed up the sound of my Cornwalls with this addition or have I helped it in any way?

I'll try to upload a picture, but have failed in this regard in the past.....

[ZAKO]

Are you trying to winterize you speakers??? I cant see any acoustic advantage.

[HarryO]

It shouldn't change anything soundwise unless you had a "rattle" between the cabinet and rear board before.

Let us know if you notice any difference though.

Harry

[Groomlakearea51]

Inasmuch as the Cornwall is a bass reflex speaker and thus ported, there should be little, if any audible difference. In the "attention to detail" arena, however, the porting assumes that the enclosure is otherwise "sealed". So by doing what you did, there are now no leaks around the rear panel. The ports, however, are quite large and unless the rear panel was, in substance, loose, there will probably be no difference. But it's good practice if you ever get a pair of old Heresy-I's....

[Kenhorns]

Yep Maron, I thought 'winterizing' the backboards would help as it gets cold down here in Florida - below 70F today - I'm now trying to figure out how to add some anti-freeze to the crossover caps!

Seriously, my thoughts were that assuring any sounds inside the cab were 'pushed/forced' out the front bottom ports rather than 'leaked' from the backboard cracks might as Martha likes to say....."Be a Good Thing!"

I know from recent experience that this Forum has some very knowledgable and helpful folks when it comes to vintage Klipsch technology and thought I would just reach out and inquire to same.

[soundbound]

You did good. Sealing the backboard can only help. I'm surprised there wasn't a seal there already. Good job.

[Kenhorns]

Thanks Groom....may I add an additional question? same subject - Cornwall Foaming - as I said, I am redoing this pair.....

My cab sound absorption is the original phyllo type paper - see photo. What thoughts on replacing this with something else?

I've seen in other posts the use of egg crate type foam (1-2" thick stuff) and it can be sourced on the web www.foambymail.com.

As my phyllo stuff is in good shape, I really don't need to change it out (and as I wish to keep as much original as possible, I will not change out this pair) , but curious for possible future refurb jobs if I run into deteriorated phyllo.

whaddayallthink about replacing foam, with what, how do you know/assure/measure that you are not destroying the original 'Klipsch Sound' and replacing with something that is really close to the original design?

[Groomlakearea51]

I would leave it alone; reason? I'm not sure what the sound absorption characteristic properties of that material actually are. If I had to replace it, I would probably find some similar material from a packing supply source. Just my thoughts.

[HarryO]

I've used the original Klipsch insulation, carpet padding, egg crate, absorption foam, sound insulation, fibrefill, and I didn't notice any real difference. As long as you break up the cabinet reflections inside the CW you should be ok.

This is only for roughly a dozen pairs of speakers from new builds though.

Harry

[Groomlakearea51]

HarryO: Of all the "substitutes", did any one in particular seem to stand out as a good substitute?

Did some research. The original appears to be several layers of "indented Kraft paper" (www.uline.com) part number S-1556, S-2146, or S-656.

On u-line, I've found that their products are extremely useful for shipping "Klipsch" stuff....

[HarryO]

"HarryO: Of all the "substitutes", did any one in particular seem to stand out as a good substitute?"

There didn't seem to be much if any difference in anything I used EXCEPT for some 2" thick foam padding used in upholstery repairs. It came in 2'x2'x2" sections priced about $6.00 each and I used 6 of them. The cabinets "toned down" a bit but I reasoned it was from the weight of the foam mostly. I don't notice the cabinet vibration as much using the thicker foam but overall sound doesn't seem to have changed much. Even this seems minimal and nothing I would go out of my way to use again.

I did some playing around with egg crate type foams specifically designed to "deliver more bass" and there was no noticable difference there either except in my wallet. More snake oil IMHO.

My conclusion to this point is I'm not sure it's very critical what you use as long as you break up the reflections in the cabinet.

I had no equipment or meters other than my ears used in this process but I did do some a/b with different materials a couple of times and I just couldn't find anything to make me use a specific product over any other.

Durability, ease of installation, cosmetics, and price are the main factors I choose.

Carpet pad. 3/4" thick in a pillow case using 3M spray adhesive and stapled seems as good as anything I've tried to this point.

As far as U-Line products go, I use their boxes, tape dispensers, and box sizer (love the box sizer. saves big bucks), for my shipping. They have some excellent boxes for shipping electronics and speakers.

Harry

[colterphoto1]

if it's in good shape, leave it. There is value in keeping original parts for Heritage speakers.

That being said, the fellas have some good advice also. The intention is to break up standing waves in the cabinet. There are many different substances that can be used. Currently we use a soft open cell foam about 1" thick in most of our products. I should open up a CWIII to see how it's done in the modern version.

[Kenhorns]

As I said earlier..."knowledgeable and helpful folks on this Forum"!
Thank you all for the responses and information.
Colt, I agree with keeping as much original as possible - but sometimes we buy stuff from previous owners who just didn't appreciate and take care of these masterpieces.
Groom, i really like the u-line phyllo paper you found (closest to original I've seen so far) - I can see stacking 3 of those 1/4" thick sheets together and using some cotton cord (like original) to staple down like the original in my cabs if I ever run into a pair that needs the phyllo replaced.

I went to Wikipedia and and Google and searched "standing waves".....nothing related to speakers there.

What are they, and how do they get produced inside my Corns, and what's so bad about the puppies? Can you see, smell, touch, or most important, hear one of them?
If so, what do they sound like, so I can tell if I ever get them?
I assume, we all now know how to get rid of the critters - foam or phyllo paper!