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Low Earth Orbit
DIY Audio
Steering advice for those serious about DIY speakers.
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<blockquote data-quote="Art Welter" data-source="post: 24500" data-attributes="member: 52"><p>Re: Steering advice for those serious about DIY speakers.</p><p></p><p></p><p> Funny, after realizing some design errors in horns I had built, I recently built a version of Charley's quadratic horn, it sounds very good. After an extended time spent designing and testing a passive crossover for it, (still not done to my satisfaction, and the two driver types I have to stick on it require completely different crossovers even though they are both 1 inch exit titanium drivers) I put that project aside and immersed myself in the study, design and building of tapped horns, they do better in smaller packages than standard horn designs.</p><p></p><p>There was a reason Tom didn’t mind giving away the "will be history" LabSub, which is very similar to many other bass horn designs.</p><p></p><p>Below is a list of my hours designing and building eight 2 x8” monitors using passive crossovers, built in 2002.</p><p></p><p>I did the original crossover design starting with a basic values from a crossover component chart. Then using an RTA, my ears and a lot of substitution of parts, I honed in on something that looked fairly flat and sounded decent.</p><p></p><p>I try to keep learning, I certainly knew a lot more about crossover design in 2002 than I did in the 1970s when I built my first passive crossovers. One of those lessons was a passive crossover “mistake” in the 1980’s which cost me six JBL 2421 diaphragms after about 16 hours making them, and a fair amount of cost in capacitors, inductors and L pads.</p><p></p><p>Fast forward to entry 1100 on my New Mexico work log, late 2008.</p><p>I had acquired Smaart several months before, and learned to use it. </p><p>That was easy, since I had 30 years of measuring speakers it probably took no more than 100 hours to become somewhat competent in its use. Well, maybe 200, but who's counting ?</p><p></p><p>After testing my venerable 2x8T monitors, found the low end to be consistent, but the tweeter range measured slightly different for each unit, and the crossover region on all had a big phase glitch.</p><p></p><p>First problem was to choose a representative driver, since they all measured differently, I had to choose one “in the middle” to design a crossover around. </p><p></p><p>Turned out my careful listening and RTA observations in 2002 had not caught a polarity reversal hidden at the acoustic crossover frequency between the 3.15 and 4K 1/3 octave ISO centers. However, reversing the tweeter polarity, while “fixing” the phase glitch, now made the frequency response terrible around the crossover point.</p><p>The crossovers, even though not a single client had complained in the course of six years, were not “right”.</p><p></p><p>Also found the porting I decided on in 2002 could have been improved for the range the monitors are used in, I had tuned them low, but always ended up using a cut off above the port tuning. Porting them higher would have given about 3 dB more level where it would be more useful, and make the midrange more clear as the cones wouldn’t have to move as far to produce that level.</p><p></p><p>After 17 days of part time work I came up with a crossover that used about half the parts, and had a smoother response than the old ones. After all that work, I now try to match pairs of monitors, the driver differences were such that three different crossover designs would have been needed to compensate. </p><p></p><p>Oh, by the way, two brand new drivers fit somewhere in the deviation range of the eight old ones, since they did not match each other, they became part of the "average" I designed for.</p><p></p><p>I have thought of going to an 8 inch coaxial design for my monitors, but can’t justify the cost, since no one has ever complained about my monitors.</p><p></p><p>Coaxial crossover design is even more demanding than a standard horn/cone crossover.</p><p></p><p>If I did decide to spend the money, I would probably purchase the coaxial 8” Ramsdell makes, which would also probably cost less money than building them myself.</p><p></p><p>But then I'd miss out on the endless hours of fun of DIY :^).</p><p></p><p>Art (DIY from when that was the way the big boys all dun it) Welter</p></blockquote><p></p>
[QUOTE="Art Welter, post: 24500, member: 52"] Re: Steering advice for those serious about DIY speakers. Funny, after realizing some design errors in horns I had built, I recently built a version of Charley's quadratic horn, it sounds very good. After an extended time spent designing and testing a passive crossover for it, (still not done to my satisfaction, and the two driver types I have to stick on it require completely different crossovers even though they are both 1 inch exit titanium drivers) I put that project aside and immersed myself in the study, design and building of tapped horns, they do better in smaller packages than standard horn designs. There was a reason Tom didn’t mind giving away the "will be history" LabSub, which is very similar to many other bass horn designs. Below is a list of my hours designing and building eight 2 x8” monitors using passive crossovers, built in 2002. I did the original crossover design starting with a basic values from a crossover component chart. Then using an RTA, my ears and a lot of substitution of parts, I honed in on something that looked fairly flat and sounded decent. I try to keep learning, I certainly knew a lot more about crossover design in 2002 than I did in the 1970s when I built my first passive crossovers. One of those lessons was a passive crossover “mistake” in the 1980’s which cost me six JBL 2421 diaphragms after about 16 hours making them, and a fair amount of cost in capacitors, inductors and L pads. Fast forward to entry 1100 on my New Mexico work log, late 2008. I had acquired Smaart several months before, and learned to use it. That was easy, since I had 30 years of measuring speakers it probably took no more than 100 hours to become somewhat competent in its use. Well, maybe 200, but who's counting ? After testing my venerable 2x8T monitors, found the low end to be consistent, but the tweeter range measured slightly different for each unit, and the crossover region on all had a big phase glitch. First problem was to choose a representative driver, since they all measured differently, I had to choose one “in the middle” to design a crossover around. Turned out my careful listening and RTA observations in 2002 had not caught a polarity reversal hidden at the acoustic crossover frequency between the 3.15 and 4K 1/3 octave ISO centers. However, reversing the tweeter polarity, while “fixing” the phase glitch, now made the frequency response terrible around the crossover point. The crossovers, even though not a single client had complained in the course of six years, were not “right”. Also found the porting I decided on in 2002 could have been improved for the range the monitors are used in, I had tuned them low, but always ended up using a cut off above the port tuning. Porting them higher would have given about 3 dB more level where it would be more useful, and make the midrange more clear as the cones wouldn’t have to move as far to produce that level. After 17 days of part time work I came up with a crossover that used about half the parts, and had a smoother response than the old ones. After all that work, I now try to match pairs of monitors, the driver differences were such that three different crossover designs would have been needed to compensate. Oh, by the way, two brand new drivers fit somewhere in the deviation range of the eight old ones, since they did not match each other, they became part of the "average" I designed for. I have thought of going to an 8 inch coaxial design for my monitors, but can’t justify the cost, since no one has ever complained about my monitors. Coaxial crossover design is even more demanding than a standard horn/cone crossover. If I did decide to spend the money, I would probably purchase the coaxial 8” Ramsdell makes, which would also probably cost less money than building them myself. But then I'd miss out on the endless hours of fun of DIY :^). Art (DIY from when that was the way the big boys all dun it) Welter [/QUOTE]
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