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Old 8th March 2008, 12:35 PM   #3181
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Quote:
Originally posted by Lynn Olson
I've been in touch with Martin, and he's willing to sell me a pair of AH-550's with a mounting plate for the Altec 288/GPA 399 driver. He also sent photos of same, shown below. I'll be buying a pair of these in the next week or two, along with either Altec 288C's (refurbished) or GPA 399's. Then I'll start measuring with MLSSA.

The old Altecs use a three-bolt pattern, while I guess the newer ones use four(?). Anyway, I'll ask Martin that the mounting plate fits either new or old versions, so I'll be measuring and auditioning many different versions (aluminum vs Pascalite diaphragms, tangential vs plastic surrounds, circumferential vs Tangerine phase plugs, different sizes vs no rear chamber, Alnico vs ceramic magnets, etc.). Since the bandwidth of interest is only 800 Hz to 7 kHz, I won't be trying to "stretch" the HF to 15 kHz, as in many other horn systems.
The altecs are 3 bolt. I've been comparing TAD 4001, Altec 290, JBL 2482 and 2440, and Plus One EC320C in several different horns and found the winner is -- the EC320C in a community 90 by 40 CD horn with oil cap compensation ran 500 up - who would have thought? I now use a two way with horn sub and six ten's dipole (almost no wings) with the top two rolled in at 200 cycles. It's spooky and extremely low compromise.
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Old 8th March 2008, 01:45 PM   #3182
FrankK is offline FrankK  Canada
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I thought I would comment since Lynn's design is similar to the Bastanis Prometheus speakers I have owned the last couple of years.

I've never heard such great soundstage and dynamics (and can play insanely loud if asked to). Sometimes I wonder if an alnico driver in lieu of the Emminance used in the Bastanis could give me better tone (not that detect a problem with it currently) and body and still retain the dynamics and high SPL capability.

The Bastanis speaker that a few critized lately from the last show was their expensive Apollo ($20k) which does in fact use alnico. I read it was slow. My relatively modest ($2k) Prometheus is anything but slow. Also I think Lynn had an issue with the high cross of the Apollo (I think 200hz to 300). The Prometheus is usually crossed at 80-110 hz.

By the way I know this would be further along with your design but things that have helped.
-remove the cover off the back of the tweeter
-add 50lb weights to stand
-Jupiter Bees wax cap (the only cap in it) lets music pour out
-still to try one sided adhesive felt (like the the under chair kind) on the underside of the baskets
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Old 8th March 2008, 01:46 PM   #3183
pk is offline pk  Denmark
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Default Which community horn?

Hi Magnetar

Sorry about disturbing the thread, but I would like to know which of the Community horns you are using with the EC320. Thanks!

Kind regards
Peter
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Old 8th March 2008, 02:20 PM   #3184
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Default Re: Which community horn?

Quote:
Originally posted by pk
Hi Magnetar

Sorry about disturbing the thread, but I would like to know which of the Community horns you are using with the EC320. Thanks!

Kind regards
Peter
I have some PC 294's that I had laying in a corner for a while and decided to try them. They have light open cell foam (not sure if it's factory) and a material like heavey grit sand paper in the throat. Once optimized with proper eq and the EC320C they are very hard to fault in my system.

The Plus One 320C has a different phase plug, magnet and diaphragm than then the previous Emilar 320, I think it is a little more transparent - not sure cause I don't have any of the old one's left to compare.
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Old 8th March 2008, 03:00 PM   #3185
pk is offline pk  Denmark
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Thanks a lot for your reply, Magnetar!

Kind regards
Peter
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Old 8th March 2008, 03:10 PM   #3186
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Quote:
Originally posted by pk
Thanks a lot for your reply, Magnetar!

Kind regards
Peter
No problem - these horns are BIG - around 30" wide - I was given them as a throw in with a pair of Emilar EC320's a couple of years ago and wrote them off without even trying them. (LOL)These sound like my 180 hz Sierra Brooks tractrix round horns (presence and dynamics to the max) but don't beam and load a little better in the low mid.

I also have the smaller versions of them buried around here somewhere I want to dig out. They may be better in the upper range but surely won't load the low mids like these.
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Old 8th March 2008, 04:24 PM   #3187
Bill F. is offline Bill F.  United States
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Interesting that you like the EC320. I have a pair that I LOVE. I suspect a lot of their magic comes from the rapid flare build right into the throat--unlike 99% of other drivers in the class.

Bill
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Old 8th March 2008, 11:10 PM   #3188
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Lynn,

How's going with the sawdust you mentioned earlier?

Hope that 1.3 yrs after your mishap (and the start of this thread) you're getting more mobile and put things in practice...
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Old 9th March 2008, 11:03 PM   #3189
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Default Vaguely ontopic ?

Did anyone hear / care to comment on the AV123 x-statik OB ? 2 x Peerless India 6.5'' caring for bass duties (box, sealed ?) + WTW in OB setup (same woofer / Peerless India 1'' dome tweeter), XOed at 200 resp 1800 Hz.

Details here


TIA for any comments / experiences.

Florian

P.S. At least the CSD should be worth commenting on
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Old 10th March 2008, 10:04 AM   #3190
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Visited the Plus One site and saw the disconcerting notice they are all booked up building sirens (for the military?) and have discontinued production of professional drivers. This "News" notice was a couple of years old - maybe Plus One should get a phone call to verify production status of the EC320?

(Please, no more eBay smoke and mirrors. Thank goodness for Iconic in Seattle and Great Plains Audio in Oklahoma City - I'd much rather support modern manufacturers than the eBay collector culture.)

So I guess Emilar has two successors - Radian and Plus One, both making pure-aluminum diaphragms with Mylar surrounds - which in turn would be the successor to the Altec Symbiotik diaphragm of the late Seventies.

Interesting that the massive EQ boosting required by THX in the early Eighties, combined with kilowatt Crown amplifiers, resulted in the destruction of the long-running Altec 288 in movie theaters and a set of the three different responses: titanium diaphragms with diamond-pattern surrounds from JBL, Pascalite aluminum-alloy (with the traditional tangential surround) and the higher-power Symbiotik Mylar surround from Altec, and traditional pure-aluminum diaphragm and Mylar surround from Emilar.

None of these adaptations were driven by sound quality (gee, I once thought THX was about sound quality), but the pressing need to make compression drivers that would physically survive the massive power assault of the new technology. Titanium has more distortion and HF breakup that starts at 4 kHz, but who cares? The jury still seems to be out on aluminum alloys and plastic surrounds, although newer phase plugs are certainly a good thing, especially if the wavefront going into the horn is more free of diffraction artifacts.

I used to think the wonderful sound of 70mm mag-track movies in the Fifties and Sixties was the result of all-tube, all-analog electronics, but I wasn't aware that the JBL-driven shift to titanium was actually a sonic step downward, driven by the absurd amounts of power being dumped into the compression drivers.

No wonder movies sound so shrill and strident - the compression drivers have 10+ dB of boost EQ so they can make it out to 15 kHz, titanium breaks up nearly an octave lower than aluminum, the constant-directivity horns have a big kink in the middle of the expansion, and the 256 kbps Dolby Digital 5.1 soundtrack has the same amount of lossy compression as MP3. Not to mention the picture area of spherical Panavision-cropped 35mm projection print is much less than a quarter of full-frame 70mm.

Oh well, considering most big-budget releases are little more than live-action adaptations of teenage-demographic comic books with lots of Xbox-grade CGI, I guess writing, acting, directing, not to mention sound and picture quality, probably wouldn't make a lot of difference. There's more money in the video game sequel, anyway. The smart money these days is in computer speakers, iPod accessories, and downloadable cellphone ringtones.

As for sawdust, I'll be contacting a local builder for the two items I want: a four-driver panel with small triangular side wings for the midbass and bass-fill drivers, and some kind of vertical stand to support the compression driver + horn and the ribbon tweeter above that. Many MLSSA measurements await before any listening and EQ attempts - mostly time-domain optimization.
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