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Coaxial Wedge Collaboration
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<blockquote data-quote="Kimo Lewis" data-source="post: 25209" data-attributes="member: 497"><p>Re: Coaxial Wedge Collaboration</p><p></p><p>Here is a question and answer from David Gunness (who has worked for EV and EAW for over 12 years) on coax speakers. David has started his own company:</p><p></p><p><a href="http://www.proavmagazine.com/acoustics/david-gunness-fulcrum-acoustic-on-speakers.aspx" target="_blank">http://www.proavmagazine.com/acoustics/david-gunness-fulcrum-acoustic-on-speakers.aspx</a></p><p></p><p>"Sam: Your newest line of products feature co-axial loudspeakers, an old idea redeployed. Why?</p><p></p><p>Gunness: My first project as a professional speaker designer was a coax–the Musicaster 100. Since then, I've designed about a dozen others and I encountered the same set of problems in all of them.</p><p></p><p>In the last couple years, I started to realize that some of those problems were not as intractable as I once thought. The key is what I've been talking about: You have to let go of the idea of a smooth, musical-sounding axial response, and just try to make it sound the same everywhere. Then, when you fix up the axial response with DSP, it fixes it up everywhere. I have returned to the co-axial design, which when coupled with carefully applied DSP, can result in some very special things."</p><p></p><p>Here is a paper David wrote in 2005 on using wavelets and impulse response to predict and improve the non-linear affects of horn/compression drivers and woofers. Makes for great reading:</p><p></p><p><a href="http://fulcrum-acoustic.com/wordpress/wp-content/uploads/2008/03/improving-loudspeaker-transient-response-with-digital-signal-processing-2005.pdf" target="_blank">http://fulcrum-acoustic.com/wordpress/wp-content/uploads/2008/03/improving-loudspeaker-transient-response-with-digital-signal-processing-2005.pdf</a></p><p></p><p>IMHO, if we want to have a "Cadillac" coax wedge, accurate measurement of polar and impulse response in a wedged shaped box and placed on the ground while taking measurements to capture the 200 hz to 300 hz "ground bounce" often seen with wedged, is the starting point and absolutely necessary. Otherwise, our box would be one more of many coax boxes on the market and wouldn't be too much different. I have used and measured many coax speakers and I usually find off axis problem spots at 6k to 10k hz which is often associated with how the compression driver is attached to the woofer, and how the "throat" loads the compression driver. Some coaxs are ok and some are real bad, none of them are great so far. In addition, the crossover location is at times, difficult to "tame" with a coax.</p><p></p><p>I agree with David, make the coax polar response uniform, then apply DSP to make it "flat". Unfortunately, we have little control on the polar response uniformity. All we can do is pick the "best" one from select manufactures and go from there. </p><p></p><p>It would be really great if we could use DSP to correct for speaker non-linearities and improve impulse response too. That would take special knowledge of DSP filters to accomplish and probably lots of DSP horsepower. But, it would provide something in the DYI world that the professional world hasn't done much of yet. I expect that to change shortly as class D power amps and DSP become increasingly less expensive.</p><p></p><p>I have been involved with coax speakers for years and have owned and enjoyed many, mostly actively driven until running into Jack who had Too Tall build him some passive crossovers for his BMS coax 12"/1". I have used and heard Jack's boxes many times and they do subjectively sound good, cut though stage din extremely well, and rarely require external EQ to control feedback. The BMS 4552 is one of the best one inch drivers out there, both in sound quality and durability. It is a great box and hard to beat. If I was interested in getting a great working box now as a DIYer, and save myself months or years of effort with no guarantee of a better box, the BMS products would be my choice and I would buy Too Tall's passive crossover, build a wedge box and be done with it. It has a know history of working in the "real" world, with hundreds of performances to it's credit. How much is your time worth? </p><p></p><p>Best Regards,</p><p>Kimo</p></blockquote><p></p>
[QUOTE="Kimo Lewis, post: 25209, member: 497"] Re: Coaxial Wedge Collaboration Here is a question and answer from David Gunness (who has worked for EV and EAW for over 12 years) on coax speakers. David has started his own company: [url]http://www.proavmagazine.com/acoustics/david-gunness-fulcrum-acoustic-on-speakers.aspx[/url] "Sam: Your newest line of products feature co-axial loudspeakers, an old idea redeployed. Why? Gunness: My first project as a professional speaker designer was a coax–the Musicaster 100. Since then, I've designed about a dozen others and I encountered the same set of problems in all of them. In the last couple years, I started to realize that some of those problems were not as intractable as I once thought. The key is what I've been talking about: You have to let go of the idea of a smooth, musical-sounding axial response, and just try to make it sound the same everywhere. Then, when you fix up the axial response with DSP, it fixes it up everywhere. I have returned to the co-axial design, which when coupled with carefully applied DSP, can result in some very special things." Here is a paper David wrote in 2005 on using wavelets and impulse response to predict and improve the non-linear affects of horn/compression drivers and woofers. Makes for great reading: [url]http://fulcrum-acoustic.com/wordpress/wp-content/uploads/2008/03/improving-loudspeaker-transient-response-with-digital-signal-processing-2005.pdf[/url] IMHO, if we want to have a "Cadillac" coax wedge, accurate measurement of polar and impulse response in a wedged shaped box and placed on the ground while taking measurements to capture the 200 hz to 300 hz "ground bounce" often seen with wedged, is the starting point and absolutely necessary. Otherwise, our box would be one more of many coax boxes on the market and wouldn't be too much different. I have used and measured many coax speakers and I usually find off axis problem spots at 6k to 10k hz which is often associated with how the compression driver is attached to the woofer, and how the "throat" loads the compression driver. Some coaxs are ok and some are real bad, none of them are great so far. In addition, the crossover location is at times, difficult to "tame" with a coax. I agree with David, make the coax polar response uniform, then apply DSP to make it "flat". Unfortunately, we have little control on the polar response uniformity. All we can do is pick the "best" one from select manufactures and go from there. It would be really great if we could use DSP to correct for speaker non-linearities and improve impulse response too. That would take special knowledge of DSP filters to accomplish and probably lots of DSP horsepower. But, it would provide something in the DYI world that the professional world hasn't done much of yet. I expect that to change shortly as class D power amps and DSP become increasingly less expensive. I have been involved with coax speakers for years and have owned and enjoyed many, mostly actively driven until running into Jack who had Too Tall build him some passive crossovers for his BMS coax 12"/1". I have used and heard Jack's boxes many times and they do subjectively sound good, cut though stage din extremely well, and rarely require external EQ to control feedback. The BMS 4552 is one of the best one inch drivers out there, both in sound quality and durability. It is a great box and hard to beat. If I was interested in getting a great working box now as a DIYer, and save myself months or years of effort with no guarantee of a better box, the BMS products would be my choice and I would buy Too Tall's passive crossover, build a wedge box and be done with it. It has a know history of working in the "real" world, with hundreds of performances to it's credit. How much is your time worth? Best Regards, Kimo [/QUOTE]
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