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Multi-Way Conventional loudspeakers with crossovers

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Old 12th March 2008, 06:52 AM   #3201
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Lynn Olson's Avatar
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Default About Caps

I only brought up the cap-coloration issue because it became an annoying factor in the Ariel crossover, requiring a half-dB adjustment because of switching brands of caps (same value, but required a tweeter level adjustment).

Right now I use waxed-paper Jupiter caps for the HP of the Ariel, but I hope the JBL biasing technique works well, allowing the use of good-quality industrial film-and-foil types with the appropriate 0.01uF bypass. I would use more than 9V of bias, though, and plan to use at least 18 or 27V of polarizing voltage (so the zero-crossing is never experienced at any reasonable listening level, and to also get the cap a bit closer to the breakdown voltage).

The Gary Pimm methodology of breaking-in the cap with 30% of the breakdown voltage at a high frequency (100 kHz) for several hours is probably worth trying as well. Our hypothetical model of what's going on with the break-in process is that the manufacturing process impresses a static charge on the film, and swinging the voltage up and down many times at a high rate of change gradually removes this latent polarization. Or something like that.

As for audibility of small stuff, I flip a switch and listen for a while. If there is no difference, then no matter. If the difference is merely a difference, i.e., just perceptible, again, so what. If the difference seems to affect a subjective quality - tonality, vividness, dynamics, intimacy, spatiality, or whatever, then more listening is called for, and at length. Many times the results are inconclusive - better in some ways, worse in others. At that point all it tells me that more work is needed, and the optimum solution has not been attained.

At other times I expect a difference and hear none, or something so small I don't care that much. I'm not very sensitive to absolute phase, for example, while other people will jump out of the their seats and say it's either terrible or wonderful. Not me. I just hear a subtle difference in timbre with certain instruments. With most records, a So What reaction.

Other times I expect to hear no difference and am dismayed to hear something large. Making small adjustments (in the 1% range) to the filament voltage of the Karna amplifiers revealed much more difference than I wanted to accept, since it implied I was going to have to spend a lot of time working on the filament supplies. This really disgusted me, frankly, and made me lose interest in all audio for about three months.

Neither outcome would be anything I predicted. Absolute phase is obvious on the scope, and some golden ears really get all wound up about it. But I just don't notice it that much - certainly not enough I'd bother to go to the effort of flipping the phase switch with every CD or record.

I was expecting some sort of audible effect as the direct-heated triodes gradually dropped in emission, but certainly not the kind of extreme sensitivity I heard. There was nothing in the literature that indicated anything like this existed.

During the rough-in phase of the loudspeaker, I won't be listening to music at all, just measuring with MLS and listening to pink-noise. Very boring and tedious, getting rid of the really big problems, chasing out resonances, and getting the time-domain to behave.

Just getting pink-noise to sound like falling water takes a lot of time - and this simple test for coloration is something most high-end speakers cannot pass. I'm not too sure many of the high-efficiency drivers are going to pass this test, for example, and I draw the line at too much notch-equalization to "rescue" a driver from gross coloration.

I don't even want to listen to music unless the speaker is reasonably flat and free of coloration - this process pretty much takes all whizzer drivers out of contention, and I expect will take a lot of time chasing out horn coloration. Maybe none of the horns will pass. I dunno. There are a lot of open variables here - all I can do to minimize the complexity is try and avoid the known-bad regions for each of the drivers.
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Old 12th March 2008, 05:10 PM   #3202
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Hello Magnetar;

Would you be able to contact me please. [ spkl350 at hotmail dot com ]

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Old 13th March 2008, 07:59 AM   #3203
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Ai (Audio Intelligence) website up; fairly in-depth information on Geddes-designed constant-directivity waveguide speakers including some imho quite impressive off-axis response curves.
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Old 15th March 2008, 02:49 PM   #3204
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Default Misc

Hi Lynn
I'm with you on the filament voltage sensitivity . Getting some amazing improvements in transparency from running the KR 300B XLS filaments at a lower voltage . More experiements on that this weekend .

On bass drivers , not sure if these have been mentioned earlier in the thread, but the BD15 custom drivers Bert Doppenberg developed for his open-baffle speaker options are certainly well worth considering.
James Doddington put me onto these the other evening when we were discussing what to use with a pair of Feastrex D5nf's .

I also noticed a link to the rather tasty Duelund capacitors, resistors etc from Bert's site. No idea what these cost of sound like, but the blurb seems interesting .

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Old 15th March 2008, 08:06 PM   #3205
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Default Duelund

They are expensive. Very. Priced in USD...

Duelund VSF

1.0 uF in aluminum = $86.70
1.0 uF in copper = $124.95
1.0 uF in silver = $1026.40

Duelund Cast PIO

1.0 uF in copper = $248.65
1.0 uF in silver = $1128.40

From what I have read they are excellent....but I would hate to think what the average pair of crossovers might cost with 30-40 components total.

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Old 16th March 2008, 10:04 AM   #3206
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Default Caps

Thanks Chris for the info .
So , somewhat more expensive than Jensen coppers then . Sort-of AudioNote - style prices .
Luckily I won't be needing 15-20 components per side in any crossover I build . Been there done that . The most impressive speakers I heard recently ( OB ) used two components per side ( one L , one C ) in a series arrangement .

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Old 16th March 2008, 11:13 AM   #3207
SunRa is offline SunRa  Romania
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Ai (Audio Intelligence) website up; fairly in-depth information on Geddes-designed constant-directivity waveguide speakers including some imho quite impressive off-axis response curves.
I wasn't aware that Dr.'s Geddes speakers were available anymore. Thank you audiokinesis!
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Old 16th March 2008, 05:40 PM   #3208
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If John Krute sees those Deulund prices he will howl louder than his new daughter... the way, congratulations John on the new addition to your family.

Non Illegitimus Carborundum
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Old 16th March 2008, 07:19 PM   #3209
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Default Duelund

Over at the HT Guide forum some of the more accomplished folks came up with an LCR design utilizing Duelund style filters. These use many components.....but not Duelund as cost was a consideration in the build.
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Old 17th March 2008, 01:48 PM   #3210
smoerk is offline smoerk  Antigua and Barbuda
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Originally posted by ro9397
I've extensively auditioned Bongiorno's Tri-naural processor in several good systems. Roger Waters' Ambisonics CD has that special wrap-around effect played back in stereo; in Tri-naural the sound field collapses into mush (only during the Ambisonic wrap-around effect).
Which Roger Waters CDs use Ambisonics?
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