Sealing Cornwall I Back Panels ?

[SonofJames]

I'm getting some air escaping from the backs of my 78 Cornwall I. Would you seal them with a window strip insulation, something else ?

Cheers

[OO1]

@SonofJames   yep , good idea   , or foam ,  gasket  material or  , any type of product  that does not stick  permanently to the wood   

[costerdock]

I can't imagine even knowing if this is happening - I have 77 CWs and with all the screws around the plywood back - it is in place pretty damn tight.

 

So not something I'd worry about.

[muel]

Use gasket tape.

https://www.parts-express.com/Speaker-Gasketing-Tape-1-8-x-1-2-x-50-ft.-Roll-260-542
 

[opnly bafld]

3 hours ago, costerdock said:

I can't imagine even knowing if this is happening - I have 77 CWs and with all the screws around the plywood back - it is in place pretty damn tight.

 

So not something I'd worry about.

 

Agree

12 screws and they have big holes in front.

[jcn3]

11 hours ago, 82 Cornwalls said:

 

Agree

12 screws and they have big holes in front.

 

yep, the front ports make using gasket tape on the back panel an unnecessary exercise.

[CWOReilly]

16 hours ago, SonofJames said:

I'm getting some air escaping from the backs of my 78 Cornwall I. Would you seal them with a window strip insulation, something else ?

Cheers

I’d say just verify all screws are tight and not stripped in the wood, but unless it’s rattling it’s probably fine since it’s a ported speaker and not sealed like a Heresy I. 

[Shakeydeal]

The removable rear panels on earlier cornwalls and Crites cornscalas were a weak point in the design. These speakers tend to have a somewhat boxy sound and loud midbass notes can even make the cabinets resonate. It's one of those things you just have to live with, but once you hear it, you can't unhear it.

 

 

[Audible Nectar]

On 9/29/2022 at 9:52 AM, Shakeydeal said:

The removable rear panels on earlier cornwalls and Crites cornscalas were a weak point in the design. These speakers tend to have a somewhat boxy sound and loud midbass notes can even make the cabinets resonate. It's one of those things you just have to live with, but once you hear it, you can't unhear it.

 

 

 

I rebuilt six of my Cornwalls recently (Cornwall Is) using the aforementioned Parts Express gasketing tape and new stainless steel screws with eyelets. The screws are a half inch longer than original, but slightly more "meaty" though the threading yet with identical "pitch" to the thread. These being the "Hillman" brand -  seemed to work out really well. Spent considerable time selecting them to make the best of the rebuild. The eyelets help a great deal to "fasten" the board to the mounting space and the gasketing (thicker/more substantive than it would first appear online) served to really seal that off and curtail that "resonance" issue.

 

I was sold a set of otherwise all original Cornwalls on this forum some years ago that had this done, and noted how well that seemed to work, so I duplicated it in essence and got same results. But yes, if unattended that aspect of the speaker is really audible, and once it's "disappeared" you go "oh wow that really was an issue huh????"

 

The eyelets really seemed to be a big part of it too - really "grips/locks down" the board edges and prevents vibration, and the added screw length/slightly more "filled out" thread made for a solid grip.

 

The rear board will actually be offset/"stick out" about 1/8-3/16ish from the gasketing all the way around instead of flush, the gasket has substance and actually creates a bit of resistance....and it seals nice and tight. That gasket material is pretty good stuff.

[jcn3]

32 minutes ago, Audible Nectar said:

 

I rebuilt six of my Cornwalls recently (Cornwall Is) using the aforementioned Parts Express gasketing tape and new stainless steel screws with eyelets. The screws are a half inch longer than original, but slightly more "meaty" though the threading yet with identical "pitch" to the thread. These being the "Hillman" brand -  seemed to work out really well. Spent considerable time selecting them to make the best of the rebuild. The eyelets help a great deal to "fasten" the board to the mounting space and the gasketing (thicker/more substantive than it would first appear online) served to really seal that off and curtail that "resonance" issue.

 

I was sold a set of otherwise all original Cornwalls on this forum some years ago that had this done, and noted how well that seemed to work, so I duplicated it in essence and got same results. But yes, if unattended that aspect of the speaker is really audible, and once it's "disappeared" you go "oh wow that really was an issue huh????"

 

The eyelets really seemed to be a big part of it too - really "grips/locks down" the board edges and prevents vibration, and the added screw length/slightly more "filled out" thread made for a solid grip.

 

The rear board will actually be offset/"stick out" about 1/8-3/16ish from the gasketing all the way around instead of flush, the gasket has substance and actually creates a bit of resistance....and it seals nice and tight. That gasket material is pretty good stuff.

 

i can certainly see how the new screws would do a better job of holding the back panel in place.  if the screws are doing their job, i just don't see how the gasket tape would make a difference.  of course, i haven't done this and you have.

[opnly bafld]

Maybe the spl one listens at makes a difference???

[muel]

It is easy to imagine that our 40 or 50 year old Cornwalls vary in their condition.  My 54 and 55 year old pairs both benefitted I think... one pair came with thin strips of Dynamat trimmed to fit and the other I installed the 1/8" thick gasket tape.  Both backs compress to fit flush to the sides.  There is a nice tight feel to the cabinet back.  I had the backs off dozens of times as I've played with alternate horns and crossover setups.  Some kind of finish washer might be a good idea as it seems the screws like to dig a bit deeper into the panel.  

It would be interesting to give it a knock test on the back before and after you apply the tape and install the back.  

[Audible Nectar]

On 10/1/2022 at 9:51 AM, jcn3 said:

 

i can certainly see how the new screws would do a better job of holding the back panel in place.  if the screws are doing their job, i just don't see how the gasket tape would make a difference.  of course, i haven't done this and you have.

 

 

Most of these speakers have had the backs off a time or two. If anyone bought Cornwalls used and didn't pull the backs first that's also recommended and another reason they get removed, etc....to make sure what's in there should be 🙂

 

When the backs are removed, or just simply mounted for 30-50 years without alteration, yet with 100db woofer pounding over it's life there's bound to be a bit of vibration. Without a "cushion" - think "window seal" there's going to be a chance for a smidge of rattle or vibration.

 

The gasket isolates that, the finish washers widen the screw head to make sure the back bonds to the now cushioned fitting such that it seals and does not vibrate.

 

I lay the speaker on it's face, remove the screws, clean the inset where the back resides, apply the gasketing along the bottom inside edges (no gaps), then re-install the newer screws/finish washers. I suggest doing this by hand (don't use power drills, you want to guide the new screws in) and do it in a fashion where you "tension them" in a half turn at a time once you get close, to seat the back evenly/gradually as you fasten it down (think auto lug nuts and "cross tightening).

 

BTW the Hillman screws came from Lowes in the blister packs, the stainless steel types. Take the old screws with you and match them up, even selecting a half inch longer version to assure the threads don't become loose. In extreme, worn out mount hole scenarios I've seen carpenters wood glue mixed with sawdust, then squeeze a bit in the old screw holes to fill the "wear out".

 

Now also in an ideal world you would do this AFTER any and all repairs, crossover work/replace, anything one plans to do inside the cab should be done, then seal them up for the next number of years. 

[opnly bafld]

I just played some bass heavy music and placed my hand on the back panel, I could barely feel it vibrating in the middle and on the edges by the screws there was absolutely nothing at all.

 

I'm not running a dance club, so I won't worry about sealing the back panel and just use the 12 screws supplied by Klipsch.

 

FWIW, YMMV, etc.

Edited October 3, 2022 by 82 Cornwalls

[SonofJames]

On 10/3/2022 at 8:44 AM, Audible Nectar said:

 

 

Most of these speakers have had the backs off a time or two. If anyone bought Cornwalls used and didn't pull the backs first that's also recommended and another reason they get removed, etc....to make sure what's in there should be 🙂

 

When the backs are removed, or just simply mounted for 30-50 years without alteration, yet with 100db woofer pounding over it's life there's bound to be a bit of vibration. Without a "cushion" - think "window seal" there's going to be a chance for a smidge of rattle or vibration.

 

The gasket isolates that, the finish washers widen the screw head to make sure the back bonds to the now cushioned fitting such that it seals and does not vibrate.

 

I lay the speaker on it's face, remove the screws, clean the inset where the back resides, apply the gasketing along the bottom inside edges (no gaps), then re-install the newer screws/finish washers. I suggest doing this by hand (don't use power drills, you want to guide the new screws in) and do it in a fashion where you "tension them" in a half turn at a time once you get close, to seat the back evenly/gradually as you fasten it down (think auto lug nuts and "cross tightening).

 

BTW the Hillman screws came from Lowes in the blister packs, the stainless steel types. Take the old screws with you and match them up, even selecting a half inch longer version to assure the threads don't become loose. In extreme, worn out mount hole scenarios I've seen carpenters wood glue mixed with sawdust, then squeeze a bit in the old screw holes to fill the "wear out".

 

Now also in an ideal world you would do this AFTER any and all repairs, crossover work/replace, anything one plans to do inside the cab should be done, then seal them up for the next number of years. 

 

If you might have the part # for those screws that might be very helpful. Cheers

 

 

I'm playing jazz mostly at moderate volume and can feel air escaping from mine in the back when there are deeper notes. YMMV

Edited October 6, 2022 by SonofJames

[SonofJames]

On 10/3/2022 at 10:09 AM, 82 Cornwalls said:

I just played some bass heavy music and placed my hand on the back panel, I could barely feel it vibrating in the middle and on the edges by the screws there was absolutely nothing at all.

 

I'm not running a dance club, so I won't worry about sealing the back panel and just use the 12 screws supplied by Klipsch.

 

FWIW, YMMV, etc.

 

I'm playing jazz mostly at moderate volume and can feel air escaping from mine in the back when there are deeper notes. YMMV

[billybob]

17 minutes ago, SonofJames said:

 

I'm playing jazz mostly at moderate volume and can feel air escaping from mine in the back when there are deeper notes. YMMV

Time to fix it.

[billybob]

Will not hurt to fix both or just the one?

Have a mono smaller speaker front ported whose rear panel I could tighten against an air leak.

Besides, sounding like it bugs you, until you do.

[jcn3]

2 hours ago, SonofJames said:

 

If you might have the part # for those screws that might be very helpful. Cheers

 

 

I'm playing jazz mostly at moderate volume and can feel air escaping from mine in the back when there are deeper notes. YMMV

 

there's nothing special about the screws -- just take one to your local hardware store and match it up.  if you're looking for something bigger, just get one size up.

[SonofJames]

3 hours ago, jcn3 said:

 

there's nothing special about the screws -- just take one to your local hardware store and match it up.  if you're looking for something bigger, just get one size up.

@Audible Nector   was speaking about an alternative screw he successfully used, thats why I was asking him for the part number. Thank you.