BEC Posted January 22, 2005 Author Share Posted January 22, 2005 jc, I have mostly been "testing with" the boxes rather than testing the boxes. The picture below is one I just made of the box that has provisions for switching in different tweeters. It is shown with 3 old 16 ohm T-35s that I rebuilt today for a customer being tested to see how close to each other they are in output. The switch panel on the left can select any of the three one at a time for listening comparison. These test boxes are what I usually choose for listening also. Right here in this room, I have Lascalas, Cornwalls, Chorus, and Heresys to choose from. I usually choose the Cornscalas. Bob Crites Quote Link to comment Share on other sites More sharing options...
jwc Posted January 22, 2005 Share Posted January 22, 2005 So what I hear you saying is that you prefer the sound of your cabinets verses the other speakers you mentioned? If that is the case, your idea/construction will go a long way on this forum. I have La scalas with a recent upgrade to ALK networks. They sound fabulous. In my venture to go from 2 channel audio to multichannel audio, I will want a lower end. Your design is just what I am looking for. If I remember correctly, you stated that your bass cabinet volume is slightly larger than the cornwall. Have you found that you are having to add any lining on the inside to improve your bass response. Is the setup you have now performing with a lowend as good or better than you cornwalls? Sorry to bug you so much. Your idea is making me want to spend some money jc Quote Link to comment Share on other sites More sharing options...
BEC Posted January 23, 2005 Author Share Posted January 23, 2005 jc, Right now one of the boxes is lined with foam carpet pad and the other is not. I can't really tell which one is lined and which is not with the two playing, but where I have them set up is far from optimum for listening, so I will have to withhold judgement on the padding until I can make room to set them up in better places. My shop is just too crowded right now. I would say that the Bass is at least as good as the Cornwalls and perhaps better. The Bass goes much lower than the Lascalas. That is easy to tell. And yes, I like the combination of good bass (like a Cornwall) and the midrange of the large horn (like the Lascala). Bob Crites Quote Link to comment Share on other sites More sharing options...
BEC Posted February 3, 2005 Author Share Posted February 3, 2005 bump Quote Link to comment Share on other sites More sharing options...
John Warren Posted February 5, 2005 Share Posted February 5, 2005 ---------------- On 2/3/2005 3:17:24 PM BEC wrote: bump ---------------- Bob- Pass on the carpet backing. When a gas is pressurized, it's temperature goes up. If there is a means to extract that temperature increase out of the gas and "store" it in a solid mass, the compression of the gas will occur isothermally. Likewise, when a gas expands, it cools. Again, if there is a means that can provide heat to the gas on expansion, it will expand isothermally. The advantage of isothermal compression and expansion is that the gas "thinks" it's in a larger container. In other words, without the fill, the box has to be larger. Theoretically, the box has to be about 40% larger (20%) is typical. That "means" is to stuff the enclosure with a material that has a very high surface area AND a very high heat capacity. The only two materials that perform this function exceedingly well are natural wool and fiberglass. Quote Link to comment Share on other sites More sharing options...
3dzapper Posted February 5, 2005 Share Posted February 5, 2005 John, Doesn't the carpet pad act to reduce internal reflections and cabinet resonance more than affect the percieved enclosure volume? You have me a tad confused. Of course that's easy to do. Rick Quote Link to comment Share on other sites More sharing options...
BEC Posted February 5, 2005 Author Share Posted February 5, 2005 Rick, You beat me to a question for John. My early 70s vertical Cornwalls have the large surface areas of the inside of the cabinet covered with something like multi-layer tissue paper. Looks to me like it would only be there to break up reflections and that was my intent in trying the carpet pad. The fact that I can't really tell which one has the carpet pad and which doesn't by listening has me scratching my head a bit and trying to figure out what is going on. Bob Quote Link to comment Share on other sites More sharing options...
John Warren Posted February 5, 2005 Share Posted February 5, 2005 ---------------- On 2/5/2005 9:44:00 AM 3dzapper wrote: John, Doesn't the carpet pad act to reduce internal reflections and cabinet resonance more than affect the percieved enclosure volume? You have me a tad confused. Of course that's easy to do. Rick ---------------- The question your asking is "what do I want to achieve and how to I go about doing it?" Fill materials serve two functions, the first one is described in my earlier post, make the box appear larger. The second is to attenuate sounds inside the enclosure. In the case of fiberglass, the frequencies that are attenuated most effectively are ones that have wavelengths that are on the order, and smaller than, the longest dimensions of the fill. So, for a woofer enclosure, harmonics produced by the woofer are attenuated and thus not heard. Cabinet resonance is a different matter entirely. Fiberglass fill will have no effect on this. To attenutate cabinet resonance the cabinet panel can be stiffened using a brace which will increase the resonance frequency above the driving frequency OR be made more massive so the energy necessary to excite it is sufficiently higher than what is available. Doubled-up MDF panels or epoxied sheets of lead flashing accomplish this. Having said that, I do not see how the foam carpet performs any of these tasks. Quote Link to comment Share on other sites More sharing options...
BEC Posted March 3, 2005 Author Share Posted March 3, 2005 Bringing this one back up by request. Bob Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted March 3, 2005 Share Posted March 3, 2005 Maybe I'll sell the Klipschorns and buy a pair your invention, Bob.... It would be hard to do that, but I just think what you have come up with is really a great idea. Quote Link to comment Share on other sites More sharing options...
D-MAN Posted March 3, 2005 Share Posted March 3, 2005 A thin foam doesn't have the absorbing capability to absorb any more than its thickness at best, for example 1/2" of foam COULD absorb (or effectively "dampen") a 1/4 wavelength (2") which would be something quite a bit higher than the 15" woofer is capable of producing even unfettered by a crossover band pass. So effectively, it absorbs nothing because all of the frequencies being produced by the woofer are below the foam application's threshold of absorbtion,and what it doesn't absorb, it reflects, although it may reduce some cabinet wall vibration to a degree. The point is, if more absorbtion at lower frequencies is needed, that likely means STUFFING of some sort, not a wall-adhesive sheet of thin material. DM Quote Link to comment Share on other sites More sharing options...
BEC Posted March 3, 2005 Author Share Posted March 3, 2005 ---------------- On 3/3/2005 8:05:23 PM Erik Mandaville wrote: Maybe I'll sell the Klipschorns and buy a pair your invention, Bob.... It would be hard to do that, but I just think what you have come up with is really a great idea. ---------------- Erik, Soon there will be enough sets of these things out there to start getting a number of opinions back on them. I hope some of the purchasers are of the tweaking variety and can come up with some improvements. Some will likely try different types of padding or packing in the bass bin and various other mods. I think they sound very good but are they as good as they could be? That is the fun part. You could own a speaker that has never been tweaked. Bob Crites Quote Link to comment Share on other sites More sharing options...
BS Button Posted March 3, 2005 Share Posted March 3, 2005 Bob, Send me a PM about Foam. BS Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted March 11, 2005 Share Posted March 11, 2005 Yesterday I had the chance to show up at Bob's shop/lab and listen to these bad boys. Tony Reed and I decided to terrorize another section of Arkansas, so we went up to harass Bob and Michael Crites. These speakers have a fabulous sound. As one would expect, a bass bin of cornwall volume and port size with a 15 inch woofer should have authoritative bass. Also, what is the icing on the cake in this speaker is the wide open mid range of a LaScala crossed at 400hz and K401 horn. The foot print is identical to LaScala. It's just a simple bass bin cab with motorboard extended for mounting the squawker and tweeter. The top end looks like a decorator Khorn. The result exceeded my expectations. To listen to these and not grin would be tough. They have bass that will kick butt. These speakers are simply killer and would be a pleasure to have in many applications. Thanks Bob and Michael. BTW, we forgot to put on "All My Rowdy Friends Are Coming Over". Would have been appropriate for the day. Quote Link to comment Share on other sites More sharing options...
BEC Posted March 11, 2005 Author Share Posted March 11, 2005 Dee, Thanks for the kind words. It was good to have you and Tony around the shop. Good also to have another set of valued opinions on the sounds of these beasts. Bob Quote Link to comment Share on other sites More sharing options...
John Warren Posted March 11, 2005 Share Posted March 11, 2005 ---------------- On 3/3/2005 7:25:50 PM BEC wrote: Bringing this one back up by request. Bob ---------------- That is the most elegant definition of bulimia I've read to date! jw Quote Link to comment Share on other sites More sharing options...
jwc Posted March 11, 2005 Share Posted March 11, 2005 Glad to see this thread was bumped. So Bob, what have you concluded so far with the testing of your drivers? Have you tried any different woofers besides the K-33? jc Quote Link to comment Share on other sites More sharing options...
BEC Posted March 11, 2005 Author Share Posted March 11, 2005 jc, I have really only used the boxes to test drivers that I have repaired. Haven't tried anything in an attempt to change the sound of the boxes yet. They sound very good to me. The bass goes very low. Bob Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted March 11, 2005 Share Posted March 11, 2005 ---------------- On 3/3/2005 8:05:23 PM Erik Mandaville wrote: Maybe I'll sell the Klipschorns and buy a pair your invention, Bob.... It would be hard to do that, but I just think what you have come up with is really a great idea. ---------------- That is an interesting question. There are probably some headbangers who would prefer this speaker to Khorn. It doesn't have that horn loaded bass character of a Khorn, but imagine the chest thumping bass in a Cornwall that has got the midrange smoothed out, kicked up to the next level. It is actually quite satisfying to listen to this speaker. Quote Link to comment Share on other sites More sharing options...
lorcoll Posted March 29, 2005 Share Posted March 29, 2005 Hi Bob, I'm starting to build the cornscala. Do you can tell me the exact dimensions of the bass cabinet (included the port size)? Thanks. Lorenzo. Quote Link to comment Share on other sites More sharing options...
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