revjac Posted January 28, 2007 Share Posted January 28, 2007 As I move down the road with my Cornwalls I'm hearing that (to this point) most of the recommendations regarding mods and tweaks have been a positive experience. Running a hardwood brace across the back of the motorboard (I bolted them on instead of just screwing them in from the back) was a particularly good idea. I would now like to address the rear panel. I believe that the addition of another panel will tame some of the resonant flex. What I would like to get is from the forum populace is some input on is making that rear panel a "sandwich". As in something between the existing panel and the panel I plan to add. The consideration here is that an additional panel may never fit flat against the exisiting panel and some sort of acoustic dampening material between the two could be a good idea - for any number of other reasons as well. I've done some research on some dampening material. Something viscoelastic seems to be the best route, whether that would be some sort of sheeting or a spray-on material. Then I cast my eye on a roll of thin cork sheeting I have lying about. Later that same day I chanced to be in my local big utility hardware store (RONA) and saw a roll of sound damping material , about 3mm thick, made from re-cycled natural fibres (cotton, wool, et al). I also have a quantity of thin closed-cell foam that might be worthy of consideration. All these with an eye to a minimal financial output. (I'm not exactly made of the long green nor does it fall like manna from the heavens hereabouts) Therefore lads, could I open this small dilemma to your consideration and perusal and, consequently, feedback? Quote Link to comment Share on other sites More sharing options...
IB Slammin Posted January 28, 2007 Share Posted January 28, 2007 As I move down the road with my Cornwalls I'm hearing that (to this point) most of the recommendations regarding mods and tweaks have been a positive experience. Running a hardwood brace across the back of the motorboard (I bolted them on instead of just screwing them in from the back) was a particularly good idea. I would now like to address the rear panel. I believe that the addition of another panel will tame some of the resonant flex. What I would like to get is from the forum populace is some input on is making that rear panel a "sandwich". As in something between the existing panel and the panel I plan to add. The consideration here is that an additional panel may never fit flat against the exisiting panel and some sort of acoustic dampening material between the two could be a good idea - for any number of other reasons as well. I've done some research on some dampening material. Something viscoelastic seems to be the best route, whether that would be some sort of sheeting or a spray-on material. Then I cast my eye on a roll of thin cork sheeting I have lying about. Later that same day I chanced to be in my local big utility hardware store (RONA) and saw a roll of sound damping material , about 3mm thick, made from re-cycled natural fibres (cotton, wool, et al). I also have a quantity of thin closed-cell foam that might be worthy of consideration. All these with an eye to a minimal financial output. (I'm not exactly made of the long green nor does it fall like manna from the heavens hereabouts) Therefore lads, could I open this small dilemma to your consideration and perusal and, consequently, feedback? jac, Cover the back, with 3/4" plywood. It will be smaller than the original panel so that the access screws will not be covered. Should take +/- 12 screws. Be sure to miss the back of the K55!!! On the inside of the motor board, I used 1-1/2"X1-1/2" steel angle. Do not allow it to touch the side panels. The steel is more rigid than wood. I dampened the steel. Screw and glue everything. To my thinking, overkill is the way to go with screws. The side panels are so small that deflection would not be expected. IMHO, this bracing is worth it. Shoot me an email and I will send you some photos. tcruse@fspecinc.com Welcome to the Cornwall Mod fraternity, Pi Slamma Jamma. I will teach you the secret hand-shake at a later date.[H] Regards, Terry Quote Link to comment Share on other sites More sharing options...
Guest " " Posted January 28, 2007 Share Posted January 28, 2007 On models that have removable rear panels, i have glued and screwed a second panel from the inside, smaller than the first, so that it will fit nbetween the cross bracing. I drilled out a hole large enough to allow for the k-55 driver. Quote Link to comment Share on other sites More sharing options...
IB Slammin Posted January 29, 2007 Share Posted January 29, 2007 ..................."i have glued and screwed a second panel from the inside,"................. Looks like installing from the inside would reduce the cab volume by almost 50 cubic inches......?? tc Quote Link to comment Share on other sites More sharing options...
Guest " " Posted January 29, 2007 Share Posted January 29, 2007 ..................."i have glued and screwed a second panel from the inside,"................. Looks like installing from the inside would reduce the cab volume by almost 50 cubic inches......?? tc Any speculation on what changes in frequency response this reduction might result in? I could increase my cabinet sizes going forward if it was significant. Quote Link to comment Share on other sites More sharing options...
revjac Posted January 29, 2007 Author Share Posted January 29, 2007 It would never have occurred to me to change the interior cabinet dimension on purpose by adding the 2nd rear panel from the inside. Hmmmmmmm. I would think that making those changes would be too much of a hit-miss venture. Even with some sort of box plot software involved the whole scenario smacks of too much of a skill level I do not possess. Just the fact that I'd like to remove the current "paper" batting and replace it with (my favourite) old-style natural fibre (wool) batting is giving me some pause. I have every intention of doing it but the original paper batting will be stored carefully just in case it needs to be re-installed. I do expect that adding that that second rear panel will have a positive effect. Don't ask me how I know this - just call it a gut instinct - although I've been wrong and right before it hasn't been 100% one way or t'other. I think I've been more right about these instincts but that's only because of a pile of research and some considered input from others higher up the R/D chain than I. I do believe that making a layered acoustic sandwich on that back panel is a good idea. Where I'm stuck is determining what the filling in that sandwich will be. I know quite a few higher-end speaker designers have incorporated at least a variation on that idea so it's not like I'm coming up with something new. As well, my thinking and past experience says that the cabinet resonances might be well-served by having the second additional panel at least of a different thickness than the original and most likely also of a different material. The thought process here being is that different thickness and material will serve to dampen/absorb different resonant frequencies than those being handled by the original panel. It's all speculative. And I like it. Quote Link to comment Share on other sites More sharing options...
IB Slammin Posted January 29, 2007 Share Posted January 29, 2007 ..................."i have glued and screwed a second panel from the inside,"................. Looks like installing from the inside would reduce the cab volume by almost 50 cubic inches......?? tc Any speculation on what changes in frequency response this reduction might result in? I could increase my cabinet sizes going forward if it was significant. Wish I knew what kind of FR change it would make. Could be inaudible, insignificant, or an improvement. That is the reason that I didn't use wood for the motor board or change much of anything on the inside. tc Quote Link to comment Share on other sites More sharing options...
Good2BHome Posted January 29, 2007 Share Posted January 29, 2007 Duplicate??? Quote Link to comment Share on other sites More sharing options...
Good2BHome Posted January 29, 2007 Share Posted January 29, 2007 As well, my thinking and past experience says that the cabinet resonances might be well-served by having the second additional panel at least of a different thickness than the original and most likely also of a different material. The thought process here being is that different thickness and material will serve to dampen/absorb different resonant frequencies than those being handled by the original panel. It's all speculative. And I like it. What you have stated above is the way you want to go. Applied to the exterior. You do not want to change the interior volume any more than you have already with the brace you applied to the motorboard. I have other ideas, but not the time tonite. Welcome, Mike Quote Link to comment Share on other sites More sharing options...
johnyholiday Posted January 30, 2007 Share Posted January 30, 2007 http://www.progressive-engineering.com/klipsch/cornwall_mod.htm Quote Link to comment Share on other sites More sharing options...
Guest " " Posted January 30, 2007 Share Posted January 30, 2007 Great link. To get the full article you have to go to the site and click the image on the right. Quote Link to comment Share on other sites More sharing options...
revjac Posted January 30, 2007 Author Share Posted January 30, 2007 Mike - anticipating any ideas you bring forward. I have no intention of changing the interior size unless I absolutely have to but there's gonna' be a panel on the back. Quote Link to comment Share on other sites More sharing options...
revjac Posted January 30, 2007 Author Share Posted January 30, 2007 It is a very good article. I've read it several times but other than the addition of the back panel doesn't really address my issue. I'm not looking for lower bass frequency particularly. In fact I'm quite happy with the bass output. Perhaps, if I used the Cornwalls for home theatre applications, then that might change things but I am only using the speakers for 2 channel stereo reproduction so there's not a lot below 40hZ that I care much about. And my collection of pipe organ music is very minimal. Except I do have "Antiphone Blues" and that needs some bottom. I would like what great sound there is now to become a trifle more taught in the nether frequencies. If and when I finally find Ray Brown's "Soular Energy" album I want his bass to talk to me in well-enunciated and articulate tones. Quote Link to comment Share on other sites More sharing options...
Guest " " Posted January 30, 2007 Share Posted January 30, 2007 Mike - anticipating any ideas you bring forward. I have no intention of changing the interior size unless I absolutely have to but there's gonna' be a panel on the back. Are you going to cover the Klipsch Label? Quote Link to comment Share on other sites More sharing options...
revjac Posted January 30, 2007 Author Share Posted January 30, 2007 noooooo! Unless I steam it.... nope - ain't gonna' doit. [] Quote Link to comment Share on other sites More sharing options...
colterphoto1 Posted January 31, 2007 Share Posted January 31, 2007 Cabinet volume is pretty critical. Installing an additional panel from the inside reduces cabinet volume by approx 17%, I'd consider this a no-no. Also if you install another horn like a 811B Altec, that has considerably more displacement than the 600 horn. Woofer, Volume, and port are intertwined. You cannot change one without changing the others. Thiel/Small parameters-look em up people. If you aren't a better engineer than Klipsch has or can understand these concepts, please leave the Cornwalls alone. Please. Quote Link to comment Share on other sites More sharing options...
IB Slammin Posted January 31, 2007 Share Posted January 31, 2007 Cabinet volume is pretty critical. Installing an additional panel from the inside reduces cabinet volume by approx 17%, I'd consider this a no-no. Also if you install another horn like a 811B Altec, that has considerably more displacement than the 600 horn. Woofer, Volume, and port are intertwined. You cannot change one without changing the others. Thiel/Small parameters-look em up people. If you aren't a better engineer than Klipsch has or can understand these concepts, please leave the Cornwalls alone. Please. .................If you aren't a better engineer than Klipsch has or can understand these concepts, please leave the Cornwalls alone. Please........................ Well, the bottom end anyway.[][][] Terry Quote Link to comment Share on other sites More sharing options...
revjac Posted January 31, 2007 Author Share Posted January 31, 2007 I have not, nor did I ever, intend to make a significant change to the interior dimensions of the cabinet. Nor do I have any idea how my original premise and consequent inquiry manage to slide off into this sidebar - oh wait - yes I do know - speaker guys. We're speaker people here. Of course the subject matter is going to change. It's what we do fer cryin' out loud! Phew! I almost forgot there for a second. And now, for me at least, back to considerations of a constrained dampening layer for the rear panel. Quote Link to comment Share on other sites More sharing options...
colterphoto1 Posted January 31, 2007 Share Posted January 31, 2007 As I move down the road with my Cornwalls I'm hearing that (to this point) most of the recommendations regarding mods and tweaks have been a positive experience. Running a hardwood brace across the back of the motorboard (I bolted them on instead of just screwing them in from the back) was a particularly good idea. I would now like to address the rear panel. I believe that the addition of another panel will tame some of the resonant flex. What I would like to get is from the forum populace is some input on is making that rear panel a "sandwich". As in something between the existing panel and the panel I plan to add. The consideration here is that an additional panel may never fit flat against the exisiting panel and some sort of acoustic dampening material between the two could be a good idea - for any number of other reasons as well. I've done some research on some dampening material. Something viscoelastic seems to be the best route, whether that would be some sort of sheeting or a spray-on material. Then I cast my eye on a roll of thin cork sheeting I have lying about. Later that same day I chanced to be in my local big utility hardware store (RONA) and saw a roll of sound damping material , about 3mm thick, made from re-cycled natural fibres (cotton, wool, et al). I also have a quantity of thin closed-cell foam that might be worthy of consideration. All these with an eye to a minimal financial output. (I'm not exactly made of the long green nor does it fall like manna from the heavens hereabouts) Therefore lads, could I open this small dilemma to your consideration and perusal and, consequently, feedback? Yes, add the motorboard brace. If I were to do this I would use a piece angle steel for strength and less reduction in cabinet volume. Add stiffening members to the back or double the back panel- but outside the cabinet. As to the materials inside, understand that is is just to reduce standing waves. The original can be found at various sellers of packing materials. Seems like the name Kim-Pak comes to mind. I'd stick to the original. Quote Link to comment Share on other sites More sharing options...
Deang Posted January 31, 2007 Share Posted January 31, 2007 ! Quote Link to comment Share on other sites More sharing options...
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