John Warren Posted May 10, 2003 Share Posted May 10, 2003 Quote Link to comment Share on other sites More sharing options...
leok Posted May 10, 2003 Share Posted May 10, 2003 John, Nice work .. theory and implementation. Two questions: How is the sound changed? How is the dynamic range? Is there an optimal volume, above which the horns take over and below which the mids take over ?? Or, do the mids track the horns ok? leok Quote Link to comment Share on other sites More sharing options...
Deang Posted May 10, 2003 Share Posted May 10, 2003 And I thought I walked alone. Absolutely wonderful stuff John. I'm surprised you didn't mate the cabinet to the shape of the bass bin though -- still, very impressive. Quote Link to comment Share on other sites More sharing options...
Audio Flynn Posted May 10, 2003 Share Posted May 10, 2003 John, I am very impressed by the work you have done. There is some concern, subjectively by me, these phenomena you describe that contribute to distortion occur audibly at very high SPL. 10 inch university drivers were considered phenominal for an electric guitar amp by some many years ago when I was deep into that technology. Many 4 and 5 way high SPL capable rock concert PA rigs use a 10 sub mid quite sucessfully. COMMENTS "Phenolic diaphragms are tough and can take the flexing but they are dense and that affects transient behavior. The elastic modulus (stiffness) of phenolic is low (more than an order of magnitude lower than aluminum) so the HF response of phenolic is not very good." There are many different performance levels of Phenolic resins and compounds of phenolic resins with different types of mineral reinforcements for stiffness. It is like different types of bread or cookies; many flavors. Key advantage is that phenolics are dimensionaly stable with very low coefficient of linerar thermal expansion over a broad temp range one could expect a sound reproducting device to incur inservice. If the mass and density is high as you describe, and I concur it could be; you better have a beat A$$ magnet to drive the diaphram. I have never been concerned about Klipsch specified magnets. They most likely have never made their own; but appear to be very adequate. "Then the flare rate, whats the best flare rate? Tractrix, Parabolic or Cantenoid? Then the horn material, wood, cast aluminum, concrete, plastic or machined from large blocks of sandwiched sheets of MDF? And then the mechanical resonances of the horn structure itself. Horns look like bells, and like bells they ring (Altec welded braces across the mouth which minimizes this). Klipsch went to an injection molded plastic horn with large stiffeners molded into the walls, its better damped than the aluminum casting but it still sounds quite bad." STILL MOSTLY TRUE. Aluminum rings like crazy. Actualy some compounds of thermoplastic ring alot and some do not. ABS in your car instrument panle squeakes like crap. If you add an elastomer to the thermoplastic horn compound it would be a nice horn dampener. If you molded a horn in 2 steps and had the rigid plastic compound on the bell surface and a "dampener" filled material for the outer surface of the horn; you would get the best of both worlds. Aluminum cannot do this! Lead and rubber filled concrete would make a nice horn, perhaps. Just to make someone think for a minute before they tear up a vintage speaker. Your concerns with horns remain valid. I just question whether or not this distortion audibly exists at 95 db, 10 feet from the speaker in a 15 x 20 room. Quote Link to comment Share on other sites More sharing options...
John Warren Posted May 11, 2003 Author Share Posted May 11, 2003 AudioFlynn, The drivers are 10" JBLPro drivers, they are made for *hifi* sound applications. You are corect about phenolics, many types. Fabrics (glass, cotton, polymeric) are imprenated with phenolic resin that can be filled with oxides. The range of densities is large too and depends on the filler and fabric material. However, the composite modulus is still quite low in these materials and that is not good for mid-range and HF reproduction, it causes distortion. The real parameter of interest is the *specific modulus*. It it the ratio of the elastic modulus divided by the specific gravity at room temperature. This is where phenolics are problematic, the effective elastic modulus is very low. Aluminum is comparable to the density of filled phenolics but it has a higher elastic modulus so it does a better job. Beryllium is real good but the cost is insane. Phenolics are tough and corrosion resistant. Important consideration for outdoor applications in inaccessible locations. Quote Link to comment Share on other sites More sharing options...
tubelion Posted May 11, 2003 Share Posted May 11, 2003 Hi John, where to get University C15W ? how much for a pair? Any idea about Magnavox 15' alnico drivers? Thanks Tubelion Quote Link to comment Share on other sites More sharing options...
Audio Flynn Posted May 11, 2003 Share Posted May 11, 2003 "The real parameter of interest is the *specific modulus*. It it the ratio of the elastic modulus divided by the specific gravity at room temperature. This is where phenolics are problematic, the effective elastic modulus is very low. Aluminum is comparable to the density of filled phenolics but it has a higher elastic modulus so it does a better job. Beryllium is real good but the cost is insane." Specific gravity has no units of measure. Density can be represented in grams per cubic centimeter. What is the unit of measure for elastic modulus? In my segment of the plastics industry we use flexural modulus testing to an ISO or ASTM test method. I do not have the test method numbers memorized they are at work. Aluminum or Beryllium would require considerable labor intensive machining. Phenolic would be compression molded and may only require minimal machining as a secondary operation. Quote Link to comment Share on other sites More sharing options...
Deang Posted May 11, 2003 Share Posted May 11, 2003 "I just question whether or not this distortion audibly exists at 95 db, 10 feet from the speaker in a 15 x 20 room." If I'm reading what John said correctly, I believe he is saying the 'distortion' is an artifact produced by the pressure loading in the throat of the horn. I don't think the size of the room, or how far away you are would have much to do with whether you can hear it or not. I certainly can see where it would relate to SPL directly. 95db is what I feel to be the limit of what the Cornwall can do before the signature starts to go south. Lots of caulk got me to near 100db. "...But the advantage of motor linearity is more than offset by the problems that arise in the high pressures generated at the throat. Air is not an ideal gas, its pressure-volume relationship is not linear. At low pressures its not too bad, but as pressures increase it gets highly non-linear and results in audible distortion." Since I'm someone who doesn't seem to have a problem with a cone doing my midrange up to 2 kH, the above statement helps me to understand why that is. OTOH, It does seem that using superior drivers, and lenses with a larger throat area would offset much of the described problem for home use -- where SPL's rarely go over 100db. I think someone like Tom Brennen might say you are simply trading one type of distortion for another. With my feeble thinking, it does seem that IMD would be higher with the cone than the horn. What do we call the 'distortion' resulting from what you describe? Some form of doppler distortion? If I had those speakers, and knew what the hell I was doing -- I would probably like to hear them as a four-way. I have never liked the idea of bottling up the lower midrange in those bass bins, and then having it squished out. I wouldn't take the 15 incher past 200Hz. 200 to 1000 on the cones, and 1000 to 6000 on a nice squawker. I guess my point here is that I'm thinking the answer to the problem your talking about is to minimize the loading in the throat by removing the lower frequencies -- those that generate, and are responsible for the most amount of diaphram movement. Dropping the crossover points and adding another driver should allow for lower IMD in the cones, and reduce the loading distortion artifact in the squawker. Wonder what it would sound like to run two sqauwkers per speaker? Sharing the load would reduce distortion too. Neat stuff. I'd love to hear those things -- RF-7's on steroids. Quote Link to comment Share on other sites More sharing options...
John Warren Posted May 11, 2003 Author Share Posted May 11, 2003 . Quote Link to comment Share on other sites More sharing options...
John Warren Posted May 11, 2003 Author Share Posted May 11, 2003 ---------------- On 5/11/2003 12:51:16 PM DeanG wrote: "I just question whether or not this distortion audibly exists at 95 db, 10 feet from the speaker in a 15 x 20 room." If I'm reading what John said correctly, I believe he is saying the 'distortion' is an artifact produced by the pressure loading in the throat of the horn. I don't think the size of the room, or how far away you are would have much to do with whether you can hear it or not. I certainly can see where it would relate to SPL directly. 95db is what I feel to be the limit of what the Cornwall can do before the signature starts to go south. Lots of caulk got me to near 100db. Correct. Equal positive and negative pressures on an air mass do not result in equal positive and negative volume changes. Air overload in the throat causes harmonic distortion. "...But the advantage of motor linearity is more than offset by the problems that arise in the high pressures generated at the throat. Air is not an ideal gas, its pressure-volume relationship is not linear. At low pressures its not too bad, but as pressures increase it gets highly non-linear and results in audible distortion." Since I'm someone who doesn't seem to have a problem with a cone doing my midrange up to 2 kH, the above statement helps me to understand why that is. OTOH, It does seem that using superior drivers, and lenses with a larger throat area would offset much of the described problem for home use -- where SPL's rarely go over 100db. Agreed, but to really hear what a horn sounds like it must be compared to other horns and even direct radiator systems similar to the one I describe above. For this project, the goal was to improve upon the Klipschorn mid yet stay within a *reasonable* budget. I think someone like Tom Brennen might say you are simply trading one type of distortion for another. With my feeble thinking, it does seem that IMD would be higher with the cone than the horn. Agreed, distortion is everywhere and cone drivers can have considerable IMD especially if they are expected to cover a broad range but so too compression drivers. In this application, the 2123Js are barely working even at deafening volume levels. What do we call the 'distortion' resulting from what you describe? Some form of doppler distortion? Air-overload causes harmonic distortion. Neat stuff. Agreed ---------------- Quote Link to comment Share on other sites More sharing options...
John Warren Posted May 12, 2003 Author Share Posted May 12, 2003 ---------------- On 5/10/2003 8:34:37 PM leok wrote: How is the sound changed? How is the dynamic range? Is there an optimal volume, above which the horns take over and below which the mids take over ?? Or, do the mids track the horns ok? leok ---------------- There more more going on in the music, more things to hear. I can listen to this setup for a much longer time than previously. Vocals and strings sound great. An A/B comparison with the stock Klipschorn was a real eye opener. On a L/R comparison the JBL setup puts out more dBs at a fixed amp setting with warble tones but that's not a controlled test. Quote Link to comment Share on other sites More sharing options...
horonzak Posted May 12, 2003 Share Posted May 12, 2003 WARREN Did you ever consider useing JBL D-216 eight inch (16 ohm) units? IM thinking of going in this direction. First JBL Hartsfield did this. But instead of my dumping into a large horn. Just useing a mutch shorter horn on top of bass horn. I have 4 D-216 units. Yours as direct radiators may be a better way to go. Quote Link to comment Share on other sites More sharing options...
sunnysal Posted May 12, 2003 Share Posted May 12, 2003 very impressive john. one more query; why not swap the horn tweeter for a inverted dome, etc. some sort of direct radiator, to keep same "family values" for mids/highs? one of those inverted titanium dome units from focal or one of the soft domes from morel? ribbon? once you give up the mids for horn distortion why not go all the way through the treble? regards, tony Quote Link to comment Share on other sites More sharing options...
ben. Posted May 12, 2003 Share Posted May 12, 2003 How's the dispersion charactaristics? Seems to me 10"s would get beamy towards the top. I also have my reservations about trading distorion types. But.. they sound good to you, so I have no problems. My bone stock Khorns still kick my arse, so I'm sure you have no problems either! Quote Link to comment Share on other sites More sharing options...
John Warren Posted May 12, 2003 Author Share Posted May 12, 2003 ---------------- On 5/12/2003 9:34:47 AM sunnysal wrote: very impressive john. one more query; why not swap the horn tweeter for a inverted dome, etc. some sort of direct radiator, to keep same "family values" for mids/highs? one of those inverted titanium dome units from focal or one of the soft domes from morel? ribbon? once you give up the mids for horn distortion why not go all the way through the treble? regards, tony --------------- Thanks. The dual array have sensitivity similar to a horn type unit (~103dB/W/m). Dome type tweeters are in the 89-93dB/W/m sort of range, not a good match. Quote Link to comment Share on other sites More sharing options...
ben. Posted May 12, 2003 Share Posted May 12, 2003 How's the dispersion charactaristics? Seems to me 10"s would get beamy towards the top. Quote Link to comment Share on other sites More sharing options...
John Warren Posted May 12, 2003 Author Share Posted May 12, 2003 ---------------- On 5/12/2003 4:12:11 PM bclarke421 wrote: How's the dispersion charactaristics? Seems to me 10"s would get beamy towards the top. ---------------- I'm not noticing this. At first I thought that stereo imaging would suffer given the fact that *two* midrange sources per side are active, but that isn't the case. Stereo effect is very good. Quote Link to comment Share on other sites More sharing options...
John Warren Posted May 12, 2003 Author Share Posted May 12, 2003 ---------------- On 5/12/2003 8:30:37 AM horonzak wrote: WARREN Did you ever consider useing JBL D-216 eight inch (16 ohm) units? IM thinking of going in this direction. First JBL Hartsfield did this. But instead of my dumping into a large horn. Just useing a mutch shorter horn on top of bass horn. I have 4 D-216 units. Yours as direct radiators may be a better way to go.---------------- I first looked for 8" drivers for this project but I couldn't find them with the right sensitivity. An 8" driver should have better HF response. The 2123 is pretty good to about 5kHz but ideally I would like to go to at least 6kHz. I didn't think about the 216 because it has been out of production for many (many) years. Do you have any pictures of the 216s? If so post them. I knew I had a picture of these on the server somewhere. Here is a picture of the 2123Js (with magnet tires still in-place). John Quote Link to comment Share on other sites More sharing options...
djk Posted May 13, 2003 Share Posted May 13, 2003 The Be diaphragms I have seen are made by vapor deposition. A copper dome is pneumatically formed (the way aluminum and titanium ones are made), then the Be is built up in a vacum chamber, then the copper is etched away. A treated cloth or mylar edge is then attached. "How's the dispersion charactaristics? Seems to me 10"s would get beamy towards the top." You could also use an 8" pair of JBL 2118H, I got eight of these in perfect condition along with four 2404 from eBay for $500 (gloat). This is the driver set from a 4612, some theaters used these for surround speakers. Mine came out of a defunt multiplex cinema. Hartsfield set up for the 8"(D208/D216/2210). http://www.audioheritage.org/images/jbl/patents/hartsfield/page2.jpg The D216 was the 16 ohm version of the D208/2210. The 2118H is the same efficency as the D208 but has flatter response, the 2118J is the 16 ohm version. Quote Link to comment Share on other sites More sharing options...
Q-Man Posted May 18, 2003 Share Posted May 18, 2003 John, My son saw the picture of your top mod that I had laying anound and asked me what it was. I explained to him what you did and he asked if it sounded any good. I told him that it sounds better the the K55/400. Then he asked if it sounds like my 290/311 mod. I told him that I couldn't answer that question. He snickered and replied that it couldn't. He's just been exposed to too many horns around here. I told him that you were using the same JBL tweeter that I am, and that only made matters worse. See, he loves that tweeter. I told him that we would have to compare your mod and mine to find out. His next question was, " Where does he live?" With sorrow, I had to say too far away. Quote Link to comment Share on other sites More sharing options...
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