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SUPPORT FORUMS FOR DECWARE SPEAKER PLANS >> DECWARE Imperial support forum >> Imperial with 16" Altec Duplex
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Message started by Michiman35 on 02/24/06 at 06:19:04

Title: Imperial with 16" Altec Duplex
Post by Michiman35 on 02/24/06 at 06:19:04

Good morning all.
My Name is Michael from Germany and im an Imperial-newbie.

I found this great site and many good informations about the Imperials in this Forum.

In the moment, i planed to use the Imperials scaled to 27,5"
wide and normal height/deep.
Ive downloaded the Imperial Drwings from Steve here on Decware.
The driver will be an Altec Lansing 904 8A Super Duplex ( Coaxial ). Its the high power version of the legendary 604 Duplex.

Now my first question : Can somebody tell me the Thiele/Small parameters from the Jensen G610 or G610B Triaxial Chassis?
Ive searched the web but nothing found.

This would be a great help.

Best wishes,
Michael

Title: Re: Imperial with 16" Altec Duplex
Post by selmerdave on 02/24/06 at 14:15:50

Michael,

Just make sure there's room behind the driver mount.  My 604E's need about 11" of clearance, perhaps the 904's don't need so much (ceramic magnets?).

Dave

Title: Re: Imperial with 16" Altec Duplex
Post by Brian on 02/24/06 at 22:09:55

Hi Michael, Welcome to the forum.  I think this is the page you want: http://alteclansingunofficial.nlenet.net/Thiele-Small.html

Title: Re: Imperial with 16" Altec Duplex
Post by Chris K on 02/25/06 at 03:00:40

At a .16Qts should be more than a stellar performer. Around 15 cu. ft. Vas. I'd love to hear a pair of Imperials with that 904-8A in them ;D

Title: Re: Imperial with 16" Altec Duplex
Post by Michiman35 on 02/25/06 at 05:16:06

Hello Guys
Thaknks for your answers.

Dave: The 908 isnt as deep as the alnico versions like your 604E. It should fit the chamber perfect.

Brian : I know this site but i search fpr the T/S Parameters of the JENSEN 610 Chassis which were used in the early 50s in the original Imperial.
Do you have an Idea?

Chris: Yes, a QTS between 0.16/0.17 should play well in the Imperials. Let us see ;-)

Nice weekend,
Michael

Title: Re: Imperial with 16" Altec Duplex
Post by Brian on 02/26/06 at 22:38:32

Hello Michael,  I was not paying good attention.  I have not found a site with the model 610 parameters.

Title: Re: Imperial with 16" Altec Duplex
Post by Chris K on 02/27/06 at 00:54:04

BTW Michiman,
From my reading of Technical papers on the Imperial of that period (mid 1950's) the Imperial folded horn like the one that Decware has "refined" is tuneable and very vesatile with regard to drivers. The throat can be extended down the front slightly to continue the taper down to effect a slightly smaller throat area. Along with adding solid mass to the inside of the compression chamber  for less volume as well as diffusion panels to "weed" out midrange frequencies from entering the throat there are many things you can do to match the horn enclosure to the driver.

Title: Re: Imperial with 16" Altec Duplex
Post by Steve_Mac on 04/05/06 at 05:40:24

Guys/Gals...
Looking for information on a bass horn with a full range speaker like the Altec Duplex. I have 2 Altec Duplex speakers and have considered making a pair but I can't wrap my head around what happens when the horn unloads and the speaker takes over. The horns in the duplexes kick in around 1500-1600Hz but what I'm talking about is the 15" woofer.

Questions:
1) What frequency does the Imperial with a 15 unload?
2) What does the phase/time alignment look like when the transition occurs?
3) What's the roll of look like when it uploads?

This is a little confusing because I can't picture a smooth transition in this setup. Maybe one of you guys have thought about this too? :) Thanks, Steve

Title: Re: Imperial with 16" Altec Duplex
Post by Steve_Mac on 04/05/06 at 05:42:46

God I can't spell...too late at night sorry
3) What's the roll off look like(3dB,6dB,etc.) when it unloads?

Title: Re: Imperial with 16" Altec Duplex
Post by selmerdave on 04/05/06 at 12:25:43

Steve, I would think the drivers would do pretty well down to somewhere around 80 - 100 hz on their own, so as long as the horn helps out around there I would think it would be fine.  I am not particularly knowledgeable about horn design so perhaps that is a useless point.  As far as the HF I've read recently that the older horns (pre mantaray) unload up around 1700-1800, while the CD horns go lower.

Dave

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