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Old 4th June 2008, 08:21 PM   #3881
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Default Re: four Pi loudspeaker response curve

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Quote:
Originally posted by salas
What is the 0 deg reference axis? Between woofer and horn rims, or on horn's center?
It's directly between midwoofer and tweeter.

I have the Smith/Larson measurement system and LMS. Keith Larson is working on adding code to his measurement system to combine several sweeps to form a polar plot. LMS offers this feature right now. One of these days real soon I'll drag the LMS system outdoors so I can publish polars. I use psuedo-anechoic measurements to see what the crossover is doing, but never for full range. I prefer to use outdoor measurements to get the full range, including bass.

Quote:
Originally posted by gedlee
But 100 dB scale - come on!! That makes the "little" glitch at about 2.2 kHz a 6 dB hole! And nothing on this plot falls below 0 dB. Whats the lower 50 dB for anyways?
The chart settings were autoscaled by the Smith/Larson measurement system. On one hand, it helps to show the bass rolloff but on the other hand, you're right that increasing scale would show any imperfections better. I'll get another sweep one of these days soon and scale it differently, providing only 50dB range instead of 100dB.

I will remind you though that no smothing was applied, whatsoever. Just adding 1/6th octave smoothing would remove that glitch completely. That's why most people publish response curves that have been smoothed - They don't show small features like that.

It's easy to tell charts that have been smoothed - If you see a curve that doesn't have any features like that, it has been smoothed. Even if the DUT generated perfect amplitude response, you'd still see random spikes at each end of the curve where amplitude falls below the noise floor if the curves were unsmoothed. Absense of these kinds of features is evidence of smoothing.
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Old 4th June 2008, 09:13 PM   #3882
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Default Woohoo!!!


Just talked to Bill at Great Plains Audio at 405-789-0221. The 414, 416, and 515 midbass drivers are now all available with Alnico magnets. Not only that, the 288H is available with aluminum diaphragm, tangential suspension, the Hendrickson/Tangerine radial phase plug, and ... Alnico magnet. I'll be ordering a set this week. Call to get the latest price and availability quote.

Some of you may be wondering what all this Alnico madness is about. Well, for those of you who have auditioned various linestage, input, interstage, and output transformers, it sounds very much like a different transformer core - a nickel vs M6 type of difference.
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Old 4th June 2008, 09:23 PM   #3883
agent.5 is offline agent.5  United States
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Quote:
The Alphahorn, Betahorn, and Gammahorn all look interesting. There are PDF measurements of a Titanium driver and a Phenolic driver. The elliptical horn shapes are intriguing to say the least.
Interesting stuffs.

Here is the text from the Gammahorn

"the standard bass system uses a 15 inch driver in an innovative reflex cabinet, combined with frontal horn loading."

I am not sure what is an "innovative reflex" cabinet. But if it is bass reflex, then we are back to the A5, A7 land.

Also,

"we are developing a modified version for a classic altec alnico driver right now"

I guess that is what Great Plains just cooked up.
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Old 4th June 2008, 11:02 PM   #3884
agent.5 is offline agent.5  United States
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Just thinking out loud here:

What is the possibility of a modern interpretation of JBL Paragon?

JBL Paragon is essentially a 3 way speaker, with a tweeter, a mid horn, and a bass horn, for each channel. By placing the tweeter and mid horn in front of the opening of the bass horn, Paragon supposely achieves a single point source. Maybe a RAAL and an Azurahorn in front of a giant bass horn.


Catalog:
http://www.lansingheritage.org/image...967/ranger.jpg

Color pictures:
http://cgi.ebay.com/JBL-Paragon-D440...QQcmdZViewItem

Construction Plan:
http://www.paragondrawings.de/plans/index.html
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Old 5th June 2008, 12:01 AM   #3885
badman is offline badman  United States
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Except that then you have time alignment issues unless you take some pretty dramatic measures to avoid them.
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Old 5th June 2008, 12:17 AM   #3886
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Default GPA Pricing

Lynn,

Do you have pricing for GPA products? I sent them an email a few weeks ago and it went unanswered.

Thank you,

Chris
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Old 5th June 2008, 01:39 AM   #3887
agent.5 is offline agent.5  United States
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Quote:
Originally posted by badman
Except that then you have time alignment issues unless you take some pretty dramatic measures to avoid them.
Agreed. Para eq will be used, and time delay may be required. I found a thread with actual users/owners talking about its pro and cons.

http://www.audioheritage.org/vbullet...ead.php?t=7528

I just think Lynn's new speaker should be pretty enough to be displayed in a museum.
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Old 5th June 2008, 07:52 PM   #3888
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Hi,
I got drivers yestarday- GPA 399 for me is serious pieces, they are build like a tank. beautiful...
Now I need some horns to them.
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Old 5th June 2008, 07:55 PM   #3889
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Old 5th June 2008, 08:03 PM   #3890
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Just called 405-789-0221 and ordered:

One pair GPA 288-16H compression drivers with low-power aluminum 16-ohm diaphragm, Tangerine phase plug, Alnico magnet, and no bug screens (why remove them if they can be manufactured without them?). US$450 each, in a short production run now.

One pair GPA 414-16 Alnico 12" midbass drivers with 16-ohm voice coils (I may buy another pair in the near future, and GPA will make them in runs as small as two). US$320 each, custom made to order.

The 515 is available with Alnico or ceramic magnets, for those that want to go the full "Voice of the Theater" route. Price a bit below US$500, the last time I checked.

They take credit cards over the phone, and ship all over the world. E-mail doesn't seem to be a very efficient way of communicating with them, I recommend phone calls instead. Oklahoma City is located in the Central Time Zone of the USA.

You will find out during the phone call (they seemed pretty busy when I called them) that there are a lot more goodies being made than the Web-page shows - I suspect they are doing a lot of OEM business, particularly to Europeans and Asians, where the classic Altec line is held in higher regard than here in the USA.

Be kind to the person on the phone - they are very very busy, so don't ask long, pointless subjectivist questions about which is better, XYZ or ABC. Do the research on the Great Plains Audio (Oklahoma City), Altec Lansing's (Unofficial) Webpage, Iconic Manufacturing Company (Seattle), the Altec User's Board, the Lansing Heritage Forum and decide exactly which version what you want before picking up the phone.

The vintage versions of the 288 that combine the Tangerine/Hendricksen phase plug with the Alnico magnet were only made a short while before the magnet was replaced with ceramic, and command very high prices - the single one I saw on Jammin' Jersey was $800, for example. Do a little shopping, and you'll find that GPA is priced very competitively - and they recharge old Alnico magnets and refurbish the original Altecs on a regular basis.
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