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Multi-Way Conventional loudspeakers with crossovers

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Old 26th July 2014, 12:46 AM   #11811
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Thanks for sharing your listening experience, TerryO! Gary Dahl and I have been collaborating on amplifiers and speakers since the early 2000's, and I'm really pleased that Gary has gone ahead and built the second version of the speaker (the first was built a couple of years ago in Dallas, Texas by an audio-friend).

Gary tells me his latest version has an improved crossover suggested by a French-Canadian builder who is part of the project, so you'll have something new to hear when you return to the sparkling blue waters of Puget Sound.

Last edited by Lynn Olson; 26th July 2014 at 12:48 AM.
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Old 26th July 2014, 10:04 PM   #11812
TerryO is offline TerryO  United States
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Quote:
Originally Posted by Lynn Olson View Post
Thanks for sharing your listening experience, TerryO! Gary Dahl and I have been collaborating on amplifiers and speakers since the early 2000's, and I'm really pleased that Gary has gone ahead and built the second version of the speaker (the first was built a couple of years ago in Dallas, Texas by an audio-friend).

Gary tells me his latest version has an improved crossover suggested by a French-Canadian builder who is part of the project, so you'll have something new to hear when you return to the sparkling blue waters of Puget Sound.
Lynn,

Wow! That's pretty quick I think. Just so I'm clear on this, Gary already has a new version of the crossover? We were over there just this last Saturday! I know he just finished (evidently last night, or this morning) his new stand-alone computer-based Music Server! Gary certainly doesn't stand still for very long once he has a plan.


Best Regards,
Terry
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Old 26th July 2014, 10:27 PM   #11813
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The French-Canadian builder has experimented with various supertweeters (RAAL Lazy Ribbon, EV T350, etc.), comparing them to a HF lift circuit that bypasses the autoformer at very high frequencies (and omitting the supertweeter). The HF lift circuit, as you might expect, delivers a rising response on axis, but this is corrected by listening to the AH425's 10~15 degrees off-axis (either by pointing them inwards or upwards).

Although a HF lift circuit for compression drivers is nothing new ... it was used in the Altec Model 19, and undoubtedly other speakers before that ... it takes advantage of the ~18 kHz first resonance of the beryllium diaphragm, and the much-improved breakup region above that. (The Materion beryllium foil has measurably better self-damping compared to aluminum or titanium foils.) Applying the same HF lift circuit to an aluminum diaphragm would probably introduce a measure of harshness (due to breakup) that's not there with the beryllium diaphragm. It's a clever way to take advantage of the properties of the diaphragm.

Gary Dahl modified the HF lift circuit for the different characteristics of the Slagle autoformer he's using, and the results are promising ... sweeter treble in the 3~5 kHz region, better imaging, more spacious ambience impression, etc. I haven't heard it for myself, but I trust Gary's taste and listening impressions. He is particularly critical of solo and ensemble violin tone, since his wife plays violin and Gary is an orchestra conductor.

As for my version, Thom Mackris (of Galibier Design and a neighbor) and I are contemplating a dual-woofer version with twin GPA 416 Alnico drivers in a configuration similar to the Altec Laguna of the early Sixties. 3 dB more efficiency, 6 dB more headroom, and a reduction in IM distortion compared to the single 416 version. That should give an overall system efficiency around 100 dB/meter/watt, and a closed-box F3 in the 60~70 Hz range (depending choice of system Q).

One of the great things about modern self-powered subwoofers is the main speaker no longer has to struggle for every last Hz of LF response. That was the problem back in the pre-T/S days of the Fifties and Sixties ... stretching LF response down, down, down, with no recourse to T/S theory. When the first papers appeared in the AES Journal in the early Seventies, the bandwidth/efficiency/size tradeoffs became obvious to everyone in the industry.

Last edited by Lynn Olson; 26th July 2014 at 10:53 PM.
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Old 27th July 2014, 03:59 AM   #11814
g3dahl is offline g3dahl  United States
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Hi Terry,

Yes, now you are going to have to come back for another listen!

The new version was in place by Tuesday, thanks to the assistance of our friends in Canada. In my case, the HF lift is set for flat response on axis, which reaches about 14 kHz. The tweeters are not in use at this time.

The change brought substantial improvements in some areas, but it has also resulted in the need for further work on the transition between the woofer and compression driver. Next step will be to take the whole thing outside so I can get some clean measurements. Some nice weather coming up...

Gary Dahl
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Old 27th July 2014, 06:17 AM   #11815
TerryO is offline TerryO  United States
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Hi Gary,

In Western Washington, finding a patch of nice, sunny weather is the real trick, and that's at just about any time during the year!
I wish you good luck for this coming week!


Best Regards,
Terry
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Old 28th July 2014, 10:15 PM   #11816
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BEFORE copying the Pacific Northwest Crossover, Google your local weather.

The speed of sound changes with temperature, humidity, and altitude. Frequency dependent attenuation varies with humidity. At 15Khz over 15ft distance, cold and wet Seattle can have 3db greater SPL than hot and dry Tucson. There are published graphs and on-line calculators for SPL vs. weather.


=====
“Actually, I believe that nobody outside of "Cascadia" could possibly win a Seattle speaker contest, unless they're from Eastern Washington, Idaho, Oregon, Montana or one of the Western Canadian Provinces.

The secret to winning a Seattle Speaker Contest that's held "during a normal cold, wet evening" is to use extremely "fast" drivers to compensate for the effects of humidity. It also helps to voice them for a rather dry, etched sound, as this further helps to offset the effects of our miserable, damp climate.

Best Regards,
TerryO “
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Old 29th July 2014, 12:55 AM   #11817
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Quote:
Originally Posted by LineSource View Post
BEFORE copying the Pacific Northwest Crossover, Google your local weather.

The speed of sound changes with temperature, humidity, and altitude. Frequency dependent attenuation varies with humidity. At 15Khz over 15ft distance, cold and wet Seattle can have 3db greater SPL than hot and dry Tucson. There are published graphs and on-line calculators for SPL vs. weather.


=====
“Actually, I believe that nobody outside of "Cascadia" could possibly win a Seattle speaker contest, unless they're from Eastern Washington, Idaho, Oregon, Montana or one of the Western Canadian Provinces.

The secret to winning a Seattle Speaker Contest that's held "during a normal cold, wet evening" is to use extremely "fast" drivers to compensate for the effects of humidity. It also helps to voice them for a rather dry, etched sound, as this further helps to offset the effects of our miserable, damp climate.

Best Regards,
TerryO “
The sound in the Seattle Symphony Hall isn't lacking in HF sparkle ... the hall is on the "brilliant" side ... and the listening distance the last time I was there was at least 50 feet from the orchestra. No PA system (thankfully), no electronics, and no EQ. All acoustic. If a hifi system could sound a quarter as good as that I'd be thrilled.

When I moved to mile-high Colorado, I wondered how sound would be affected by the 14% decrease in air pressure. As it turns out, the speed of sound is changed less than 1%, which kind of surprised me. But the humidity is certainly less, all year round. Do things sound different here? I'm not too sure about that ... and I lived in the soggy Pacific Northwest for forty years. The biggest difference is the surprisingly noisy high prairie wildlife (birds, prairie dogs, coyotes, owls, etc.) and the shockingly loud thunderstorms.

The biggest effect on tourists is a physiological and psychological reaction to the altitude. You don't notice much the first day, then you start to feel weird for several days afterward. I didn't really fully adapt until about three to four weeks later. This varies a lot with the person, and there's no way to tell in advance how you will react to the altitude ... and 5280, 8000, and 10,000 feet all feel quite different from one another. Also, get polarized sunglasses; the UV levels are very high compared to most other cities.

Fair warning to tourists who want to try out our newly legalized crop, the lowered partial pressure of oxygen will make the psychological effect much stronger than you might expect. There's an Oxygen Bar in Boulder if you want to feel "normal" when you visit here. I highly recommend it, you'll love the enhanced color perception and extra zip you'll get.

Last edited by Lynn Olson; 29th July 2014 at 01:24 AM.
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Old 29th July 2014, 02:57 AM   #11818
gedlee is offline gedlee  United States
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The only effect of weather on sound is HF air absorption, which, since there is very little sound > 10KHz, is virtually a non-effect. Claims to the contrary are pure fiction.

Having just returned from Seattle, they have a "crop" as well. So does Vancouver. Maybe this new trend will bring back "stereo"!! I know it was an important aspect when I was growing up.

I once went sleepless for several days in Denver. Altitude will do that. Felt fine otherwise.
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Old 29th July 2014, 08:27 AM   #11819
Elias is offline Elias  Finland
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Winter is the worst time to go to a concert. On the other hand who wants to go to concert in summer time..

Click the image to open in full size.

That's air attenuation for 30m distance. For a concert hall, attenuation is noticeable. And the reverberance field is affected heavily.


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Old 29th July 2014, 03:28 PM   #11820
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I suspect there will be some effect akin to an air cooled motorbike. Ventures out in hot weather 86 degrees F as the engine warmed it wouild eventually show some slight tailing off in power.

Will not go into the tech details here. But the same presents with the drivers units. Albeit the speaker diaphrams will move further in hot weather with lower air density epecially with lower air pressure from low pressure storm conditions, and surrounds flex more with the slight loss of stiffness and viscostatic properties. Frequencies will rise with loss of air density.

Can we hear it. You betcha. Sure if you are sensitive to it. At least string instruments can retune.

No come on lets be having you with all your ideas out there.
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