Deang Posted January 31, 2007 Share Posted January 31, 2007 @ 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...
colterphoto1 Posted January 31, 2007 Share Posted January 31, 2007 Thanks Dean, I'd never seen that entire article. The port mod looks interesting. Has anyone tried this? Quote Link to comment Share on other sites More sharing options...
revjac Posted January 31, 2007 Author Share Posted January 31, 2007 Dean - Thanks for going to the time and trouble of posting that article. I have read it several times over the past few weeks but other than saying that adding a panel to the rear (which I will do) will help it doesn't really address my query (making the rear panel a constrained dampening sandwich). Maybe I should just go ahead and try a few things on my own. I don't seem to be getting any specific, pertinent feedback to the proposed premise in my original post. Quote Link to comment Share on other sites More sharing options...
johnyholiday Posted January 31, 2007 Share Posted January 31, 2007 Thanks Dean, I'd never seen that entire article. The port mod looks interesting. Has anyone tried this? don't bother Quote Link to comment Share on other sites More sharing options...
johnyholiday Posted January 31, 2007 Share Posted January 31, 2007 Dean - Thanks for going to the time and trouble of posting that article. I have read it several times over the past few weeks but other than saying that adding a panel to the rear (which I will do) will help it doesn't really address my query (making the rear panel a constrained dampening sandwich). Maybe I should just go ahead and try a few things on my own. I don't seem to be getting any specific, pertinent feedback to the proposed premise in my original post. maybe Alprazolam Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 31, 2007 Share Posted January 31, 2007 re: bracing.... This is something that you can take way way too far. A perfect example would be all the coolest bridges in the world. They don't make a solid piece of steel going across, but rather do all them triangle shape things (ya, I know - butchering the analogy). Anyways, all you need to do is move the resonance frequency of every panel face into a region outside the passband of the woofer. The easiest way to do this is with cross-bracing....doesn't take much, maybe a 1" x 1" rod going across and screwed in from the sides. Ok, maybe that's ugly....pressure fit it and use glue. There are some very simple ways of determining if your panel is resonating and even the frequency involved. Everytime you cut the free resonating portion in half, you double the fundamental frequency of resonance. I know it's blasphemy to promote not going overboard - especially with audio.... If all you're concerned about is the rear panel of the cornwall, then your best bet is probably a pair of 2x4's splitting the rear cabinet into thirds (so running vertical on the rear panel). As far as the change in cabinet volume....any reduction without any changes to the port is going to increase the port tuning. The cornwall is already ported "too high", so this would be a bad move. However, changing as much as 400 cubic inches probably isn't going to be audible. Throw in a little damping material and you won't have to worry about it. Quote Link to comment Share on other sites More sharing options...
IB Slammin Posted February 1, 2007 Share Posted February 1, 2007 Dean - Thanks for going to the time and trouble of posting that article. I have read it several times over the past few weeks but other than saying that adding a panel to the rear (which I will do) will help it doesn't really address my query (making the rear panel a constrained dampening sandwich). Maybe I should just go ahead and try a few things on my own. I don't seem to be getting any specific, pertinent feedback to the proposed premise in my original post. maybe Alprazolam Works for me!!!![|-)] Quote Link to comment Share on other sites More sharing options...
Guest " " Posted February 1, 2007 Share Posted February 1, 2007 Maybe a thread on your findings..... We used to work with layered foam filled honeycombed aluminum panels during my army aviation days. Mainly due to the need for impact strenth and light weigth. Niether conditon is a design objective for stiffining the rear panel of a cornwall. Not too many bulllers get shot at the back of a cornwall. Quote Link to comment Share on other sites More sharing options...
Good2BHome Posted February 1, 2007 Share Posted February 1, 2007 Dean - Thanks for going to the time and trouble of posting that article. I have read it several times over the past few weeks but other than saying that adding a panel to the rear (which I will do) will help it doesn't really address my query (making the rear panel a constrained dampening sandwich). Maybe I should just go ahead and try a few things on my own. I don't seem to be getting any specific, pertinent feedback to the proposed premise in my original post. revjac, Sorry it took me so long to get back. IMHO bracing the back will do way more to improve the bass than it will do to improve the higher frequencies. My main idea is simular to DrWho's 2 x 4 comment. First I would use the original backs as a pattern to make new backs to use and preserve the originals for the future. Then use 4 pieces of either Ash or Hard Rock Maple 1" x 2" in a Tic-Tac-Toe pattern, with the 1" edge planed flat by a mill machine. The milled surface would be the surface next to the speaker back. Where the pieces overlap cut a 1" wide groove in each. A screw and glue would be used at each intersection. This "matrix" would then be screwed and glued to the exterior back. New damping material added to the interior side. And this does begin to approach "bridge making". The secondary idea was to epoxy 1/8" steel plates to the new backs. Different materials with different thicknesses DrWho, Did I understand your comment to mean: a stock Cornwall's interior volume is slightly too small. I have believed that for some time based on a comment Paul Klipsch made years ago which implied the same, but he didn't just come out and say it. I'm not enough of an engineer to figure it out for sure. Do you have proof and by how much? Mike Quote Link to comment Share on other sites More sharing options...
Good2BHome Posted February 1, 2007 Share Posted February 1, 2007 Thanks Dean, I'd never seen that entire article. The port mod looks interesting. Has anyone tried this? don't bother Can you expand on your answer?? Quote Link to comment Share on other sites More sharing options...
DrWho Posted February 1, 2007 Share Posted February 1, 2007 I'm not sure where I read it, but T/S parameters weren't around when PWK designed the Cornwall. He was left to designing by ear and going through a lot of trial and error. I'm sure he was trying to use some "elementary" math at the time too. Anyways, it turned out that he was within 15% of what T/S parameters dictate as ideal for the driver (I'm not sure on the actual number, but it was something like that). And then I believe it was a Klipsch engineer who was telling me about how Paul was actually heavily involved with the work of Theile and Small - the cornwall being one of the speakers under study. One of the implications of the Cornwall design is a slight bump in the frequency response before the knee (where it starts to roll off). Some might argue some benefit here as it pertains to equal-loudness, and there are some psychoacoustical effects that point to it being a more natural way for a speaker to roll off. There are also some advantages when you consider the typical nonlinear behavior of ported systems. It's interesting to note that PWK didn't change the cornwall design after the T/S parameters became popular. So I guess the answer is "yes" - but I wouldn't suggest changing the design [] Quote Link to comment Share on other sites More sharing options...
colterphoto1 Posted February 1, 2007 Share Posted February 1, 2007 I heard 3% Doc, btw good post there, do you want a job or what? Quote Link to comment Share on other sites More sharing options...
DrWho Posted February 1, 2007 Share Posted February 1, 2007 I dunno - is there an opening for a janitor? I bet the engineering wing would be kept cleaner than ever [] Was it really 3%? Does that speak more for PWK's ears or the validity of the model? [Y] Quote Link to comment Share on other sites More sharing options...
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