boom3 Posted October 1, 2005 Share Posted October 1, 2005 I still think it possible to make these with stereo lithography. The interior space would made first, then coated with release compound, and then sprayed to make the outer wall. I think the technique can make underrcuts as is required foir the driver mounting flange. I work with some fab guys that do the S-L stuff frequently, I'll ask them. Might make a good intern project. Quote Link to comment Share on other sites More sharing options...
Number 9 Posted October 2, 2005 Share Posted October 2, 2005 Not to make a mountain out of a mole-hill, but this "issue" of the standing waves in the CIII, resulting in the need to move the woofer up several inches, caught my attention. If the CIII has similar dimensions to the original Cornwalls and is using a similar woofer and is tuned in a similar way ... would that not mean that the original Cornwall and Cornwall II probably had the same issue? e.g. Has there been perhaps a standing wave issue with Cornwalls all along? Quote Link to comment Share on other sites More sharing options...
3dzapper Posted October 2, 2005 Share Posted October 2, 2005 Good question #9. Will anyone ever know? The CIII has, I am led to believe, a different woofer, squaker, tweeter, crossover, and internal damping as well as a redesigned port. Unless someone with megabucks test equipment tests the original for this standing wave "problem" I don't think we will ever know. Rick Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted October 2, 2005 Share Posted October 2, 2005 number nine, My understanding is quite limited technically, but my take on the plain sense of the standing wave issue means, yes, the earlier versions of CW had (have) this issue. Listening to the engineers in Hope talk about this, it was a fairly challenging thing for testing and measurement... both to ID the problem and arrive at a solution. Quote Link to comment Share on other sites More sharing options...
JJkizak Posted October 2, 2005 Share Posted October 2, 2005 Stading waves means the reverse wave is interferring with the frontal wave. I would like to see how that is measured. Seems to me that you would have to be weened from MIT or Bell Labs to figure that one out to get valid measurements. JJK Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted October 2, 2005 Share Posted October 2, 2005 JJ, I think what you mean is that it would take a hell of an engineer to do that? right? Well, Roy Delgado is da man! I'm not sure, but I think he is a grad of New Mexico State and was the right hand of Mr. PWK. Pretty good credentials and experience. Quote Link to comment Share on other sites More sharing options...
jwc Posted October 2, 2005 Share Posted October 2, 2005 Guys, what woofer are they using in the CWIII? I know the mid and tweet are different but what of the K33 in the new Corn? Quote Link to comment Share on other sites More sharing options...
BEC Posted October 2, 2005 Share Posted October 2, 2005 I think Roy said it was a new woofer and a K-39. I may have gotten that wrong. I was into information overload condition there in the lab. Bob Crites Quote Link to comment Share on other sites More sharing options...
Seadog Posted October 2, 2005 Share Posted October 2, 2005 According to Roy's explanation, finding the standing wave and fixing it required a lot of trial and error. Accelerometers were apparently used to quantify the problem and verify the resulting fix. Quote Link to comment Share on other sites More sharing options...
johnyholiday Posted October 3, 2005 Share Posted October 3, 2005 To address some points. That Big Flat Face in the CW motorboard might just be one of the reasons it projects sound forward so much. With narrower speakers, as in tower designs, doesn't some of the sound try to 'wrap around' the cabinet and not get projected forward? This is a new woofer, woofer placement, port volume and crossover. I don't know what they've done, but the transitions seem very smooth and the upper reaches of the woofer just sound tremendous. I can't wait to hear the electric bass of Chris Squire of Yes on them! I don't know exactly which mid driver is behind that 701 horn. Maybe the Atlas PD5VH (K55?) or ??? The crossover had a lot of elements in it for a three way cabinet, so perhaps there are some 12 db slopes in there as well. What you're referring to actually has a name: "baffle gain" - and it is an integral part to the designing of flush mounted monitors in the studio (flush mounting could be modelled as a baffle that extends for "infinity" in all directions, hence the name infinite baffle - IB subwoofers) [] Attached is a pic that shows the impact of the frequency response when a speaker is flushmounted. Usually a counter-EQ is implemented to bring the response back to flat, which accomplishes a design that digs a bit lower and has even less conemovement (6dB corresponds to 1/4 the excursion!) As the baffle gets smaller (like closer to the size of a speaker's motorboard), I believe it follows the same curve, but starts to drop off at frequencies where 1/4 the wavelength is larger than the width/height of the cabinet (or is it 1/2? I forget). Note the the response gets affected all the way up to 1kHz! (about 1dB) Anyways, it is a well documented phenomenon and I too believe that is one of the reasons for the cornwall's signature sound...though that large baffle connected to the motorboard makes me wonder how much the big face is being vibrated and making its own sound - I bet this might be the source for the ever so slight congestionin the lower mids. In the studio, great lengths are taken to keep the motorboard as uncoupled from the "infinite baffle" (the wall) so as to minimize sympathetic vibrations. I bet the standing wave problem they found and fixed had a lot to do with the large front face vibrations. i would hire this guy in a minute, if i was expanding my empires ,into speaker design Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted October 3, 2005 Share Posted October 3, 2005 Bob may have that right on the designation of the new CWIII woofer. The only info I remember about that is that the new woofer is currently in use in some of the pro threatre models. Quote Link to comment Share on other sites More sharing options...
Deang Posted October 3, 2005 Share Posted October 3, 2005 "I would hire this guy in a minute, if I was expanding my empires into speaker design." Yeah, Dr. Who knows cool stuff. Wish I knew what in the heck he was talking about most of the time. Quote Link to comment Share on other sites More sharing options...
colterphoto1 Posted October 4, 2005 Share Posted October 4, 2005 Dr Who is getting one heck of an education in sound system design and physics, don't know what it's called but he's into some super serious course work. You guys should sit down with him for a couple of hours, he makes my brain hurt! Michael Quote Link to comment Share on other sites More sharing options...
BS Button Posted October 9, 2005 Share Posted October 9, 2005 Nice avatar Colter! Quote Link to comment Share on other sites More sharing options...
colterphoto1 Posted October 9, 2005 Share Posted October 9, 2005 Thanks Todd. Guys, I'm trying to get the info on how to minimize the standing wave on older CW by either A) where to mount the woofer for modifying an existing CW motorboard (in my case I want to build a custom CW center speaker, so might as well put the hole in the optimum location. where to install deflector board, per early experiments in this area WIll post if I find out anything. Quote Link to comment Share on other sites More sharing options...
jwc Posted October 9, 2005 Share Posted October 9, 2005 Thanks Todd. Guys, I'm trying to get the info on how to minimize the standing wave on older CW by either A) where to mount the woofer for modifying an existing CW motorboard (in my case I want to build a custom CW center speaker, so might as well put the hole in the optimum location. where to install deflector board, per early experiments in this area WIll post if I find out anything. Michael, I know it was said earlier that the woofer moved up 6 inches. I think I heard the same port was somewhat shorter. Does anyone know how much shorter? Is the port the same width and height? By the picture, it looks the same. The more the port is shortened for a K33, the tuning of the bass goes up. Now I know the driver is different. But regardless the tuning goes up with the same volume cabinet. Now I know the curves for the K33 don't look to me like they are supposed to, but even if I were to put more data in to get the curve "flatter", the tuning still goes up in Hz. The red curve is with a port 2 inches shorter. Quote Link to comment Share on other sites More sharing options...
colterphoto1 Posted October 9, 2005 Share Posted October 9, 2005 That point is moot JC, it is no longer the K33 driver, I think it's a K39, but don't quote me. It's defintely a new animal in there though. But the standing wave problem WAS present in the old cabinets. There is a photo of an original CW cabinet with holes all over it and a new motor board with hole for TRACTRIX mid horn and the new location for the woofer. I was told personally by Chris that that box was the final test subject for locating the standing wave. Michael Quote Link to comment Share on other sites More sharing options...
jwc Posted October 9, 2005 Share Posted October 9, 2005 I wouldn't say it is moot. I know there is a driver change. Yes, I heard it was a K39. I think I heard that from Bob. I wish there were some specs somewhere. I bet it won't be much different. In any case, The tuning will be about the same. Quote Link to comment Share on other sites More sharing options...
DrWho Posted October 10, 2005 Share Posted October 10, 2005 i would hire this guy in a minute, if i was expanding my empires ,into speaker design wow, now that would be a dream come true [] btw, sorry for making the heads hurt...didn't realize I was doing it cuz I thought I was learning from you guys? lol I'm curious about the graphs jw is modelling...I had always thought the cornwall was in a much larger cabinet, but he has actually measured the internals so he's gotta be right and you get that nasty ugly response when it's modelled...I'm wondering if maybe we all have the T/S parameters for the driver screwed up??? It doesn't look anywhere near the posted response charts - even with room gain taken into account. The size of a port is a function of the cabinet so the tuning will be higher...and if klipsch is borrowing woofers from their pro-lineups then this would follow the trend of higher SPL's at the cost of extension (but we're probably only talking a few Hz). Quote Link to comment Share on other sites More sharing options...
colterphoto1 Posted October 10, 2005 Share Posted October 10, 2005 I keep hearing that the K39 (?) used in the CW3 is a from their pro line, but scouring that catalog does not show a K39 anywhere. I doubt if they would have engineered a woofer especially for this project, so I'm confused as to the origin of this woofer. Michael Quote Link to comment Share on other sites More sharing options...
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