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Multi-Way Conventional loudspeakers with crossovers

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Old 18th June 2012, 03:19 AM   #7741
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Quote:
Originally Posted by tomtom View Post
Lynn, I suppose in your case with lazy ribbon - the radiated power /and this is perceived at UHF/ of lazy ribbon is roughly equal of radiated power of Azura at XO, although polar are different shape. Thats why you have less pain with integration.
That is a very good point. Just by accident, the effective radiating area of the AH425 and the large RAAL are fairly similar in the 7~10 kHz range. The AH425 mimics a direct-radiator of about 3~4" diameter at those frequencies, which in turn sets the HF directivity index (DI). The RAAL ribbon is about 10" high and 0.5" wide, so the emissive area isn't all that different.

Although the polar patterns have a different shape, the overall directivity index is fairly similar. This probably results in a gentler hand-off between the two drivers than the more typical scenario of a tiny 2" supertweeter matched to a large-format horn - the horn is really directive at the top of its working range, while the compact supertweeter is radiating into a full 90-degree angle. Abrupt deviations in DI are usually audible as discontinuities in the spectrum, or at the least, a shift in spatial perspective that is frequency-dependent.

For that matter, the transition between the single 15" bass driver and the freestanding 16.5" Azurahorn is also simple, with a crossover in the 630~700 Hz range and similar directivity indexes from both drivers.

I might at some point consider a pair of 15" drivers, but if I try that, I think I'll put them side-by-side, just under the horn, and lower the crossover a bit (or use a larger horn).

Changing topics, there is a small chance that the problematic supertweeter integration in your system is an artifact of the HF power amplifier. I have had power amplifiers give the false impression of a bad or defective tweeter before - they can sound rather alike, and you're never completely sure until you try a different type of power amplifier.

One of the nastier aspects of multi-amped systems are power amplifiers with dissimilar characters for different drivers - so you're not sure that XYZ driver sounds "dry" or "wet" or if it's just the sound of the amplifier. Unlike drivers, Class AB amplifiers change distortion spectra with decreasing level, so the sonic character can change with crossover settings and musical dynamics. If the amplifier is doing this, subjectively balancing a multi-amped system can be almost impossible, since the sound of the amplifiers themselves are level-dependent.

With a single amplifier driving the complete loudspeaker, it's easy to tell if the power amplifier is a bad actor - just swap it out and see what changes. Any amplifier colorations that occur are applied to the entire loudspeaker.

With a multi-amped system, the number of potential amp/speaker colorations is very large, when combined with active crossover level-setting and frequency adjustments. Is it the amplifier, or does the level need to come down 0.5 dB, or the HF crossover moved from 7 to 8 kHz?

Last edited by Lynn Olson; 18th June 2012 at 03:35 AM.
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Old 18th June 2012, 03:25 AM   #7742
Pano is offline Pano  United States
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This can be avoided with passive crossovers.
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Old 18th June 2012, 03:44 AM   #7743
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It's enough of a hassle designing direct-heated triode PP amplifiers along with matching loudspeakers. The thought of a multi-amped system where I have to design multiple Class A amplifiers, along with all-vacuum-tube crossovers, is just too much. I have to draw the line somewhere.

I've been designing amplifiers long enough to be resigned to the fact that "uncolored" amplifiers do not exist, and might possibly never exist. They all have a sound - admittedly, it's not easy to recognize the colorations until you've designed a few for yourself. Then the "electronic" colorations become a lot more noticeable, and plenty annoying. Consider yourself lucky if you don't hear amplifier colorations.

Some amplifiers are better than others; some are worse, and there are very strange amp-speaker interactions that almost exactly mimic the sound of bad drivers. Amplifier colorations tend to be level-dependent, and colorations are typically in the mids and highs - the more zero-crossings and potential for current-slewing events, the more trouble there is.

I get around this by combining all-Class-A operation with very high slew rates and devices selected for the lowest possible inherent distortion. That doesn't make me a genius; it's just the easy way out. It also limits power to the 20~30 watt range.

Last edited by Lynn Olson; 18th June 2012 at 04:11 AM.
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Old 18th June 2012, 03:56 AM   #7744
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One last distraction, then back to our regularly scheduled programming:

Note the inductor orientations in our crossovers are nearly identical. Admittedly, I only used measurement, not my ears (they would fail me), but it appears there is safety in numbers. If addressing the question of pickup from the voicecoil/magnet, you also get a third dimension (vertical spacing) to play with, making it even easier.

Caps are glued with a flexible RTV, instead of the foam idea.
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Old 18th June 2012, 04:16 AM   #7745
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Very similar, and a lot better than what you see in high-end $80,000 speaker systems.

You also have the good taste to avoid those awful-sounding flat-pack inductors. Why anyone ever got the idea that packing an inductor with nasty-sounding plastic between the layers is a mystery to me. A conventional air-core inductor wound with (relatively) oxygen-free wire has almost zero (subjective) coloration, which is a lot better than nearly any capacitor. Not sensitive to microphonics, either.

Use good-quality wirewound resistors with a generous power rating and you are good to go.

Last edited by Lynn Olson; 18th June 2012 at 04:26 AM.
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Old 18th June 2012, 06:49 AM   #7746
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Quote:
Originally Posted by Pano View Post
This can be avoided with passive crossovers.
I have been toying with autoformers on my compression drivers and supertweeters in an otherwise purely active setup, and even a very cheap unit like the ones from parts express give very good results (with a very slight attenuation in the UHF that can be easily compensated for).
If set around -9dB or lower, the measured distortion, that mainly comes from the amplifier with normal A/B or D designs and well designed compression drivers or supertweeters, is really reduces with the autoformer, and the noise floor is also lowered by that much.

Last edited by pos; 18th June 2012 at 06:52 AM.
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Old 18th June 2012, 08:03 AM   #7747
SunRa is offline SunRa  Romania
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Quote:
Originally Posted by tomtom View Post
Since discussion that i started moves on. I attach picture of my system.
Tom, do you have more pictures? Those are gorgeous looking.

I guess I recognize AE Speakers woofers (how big?). Which horns are those? Jzagaja's? Or something custom?

Thanks!
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Old 18th June 2012, 08:43 AM   #7748
tomtom is offline tomtom  Slovakia
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Originally Posted by SunRa View Post
Tom, do you have more pictures? Those are gorgeous looking.

I guess I recognize AE Speakers woofers (how big?). Which horns are those? Jzagaja's? Or something custom?

Thanks!
Thanks
Hi these are TD12M - and horns are custom - with build in Toe-in. Part of toe in is curvature of wall and part is in horn. Speaker baffle you see is 120x100cm.
There is also 4x 15inch per side for lowest octave. - under the cloth grills.
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Old 18th June 2012, 09:58 AM   #7749
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An other request for Tomtom:

can you extend the discussion a little bit towards the eventual qualities (and trade offs) of such a flush mounted system. I mean the supposed absence of diffraction, the 2 Pi space radiation and everything related having measurable or preferably audible consequences. I already see that the toe in is embedded.

I believe that Mr Olson will not report you for hijacking, and bravo for either the concept and the innovative aesthetics.
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Old 18th June 2012, 03:47 PM   #7750
SunRa is offline SunRa  Romania
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Thanks for the reply and the additional details, I still hope for some more pictures though
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