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Old 28th January 2006, 03:51 PM   #1
MJK is offline MJK  United States
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Default And now for something completely different ......

..... at least for me. Not a TL this time.

(Trivia question : What TV show did that line come from? You will show your age with the answer.)

Thought I would share my latest project, my son and I wired it up last weekend and it has been tweaked several times during the past few days.

http://www.quarter-wave.com/OB_Wings_Back.jpg

http://www.quarter-wave.com/OB_Wings_Out.jpg

This is an OB system (48" tall x 60" wide with the wings out) using either the Lowther PM2C, PM2A, or DX4 driver and two Dayton 15" high efficiency woofers (JBL 2226 clones) per side. I am using a DBX DriveRack PA digital crossover, the woofers roll off at 120 Hz 12 dB/octave and the Lowthers roll in at 120 Hz 24 dB/octave, and two Rotel RB-1080 200 watt amps.

All solid state and no passive BSC filter required. My calculations indicate the efficiency is about 98 dB/w/m and reasonably flat above 50 Hz. Decent bass into the 30 Hz range but no measurements yet to prove any of these numbers.

This is a very efficient system and even at fairly loud volumes the drivers barely move, you have to touch them to convince yourself they are connected. Great dynamics and bass. Best reproduction of a kick drum that I have heard from any of my own speaker designs, they can move a lot of air. Very similar sound to my Lowther ML TL design but with better bottom end, no big surprise I guess.

More details to come on my web site when I am done tweaking and find time to documented the project,
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Old 28th January 2006, 04:53 PM   #2
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Interesting design. Given up on TLs then?

Those pics are too compressed to do the project justice though...
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Old 28th January 2006, 05:17 PM   #3
MJK is offline MJK  United States
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Quote:
Interesting design. Given up on TLs then?
I have not given up on TLs but I don't want to be totally one dimensional. I wrote an OB worksheet and just wanted to try it out, easy and quick project with drivers I had lying around. My wife hates them so I am not sure how long they will be allowed in the house.

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Those pics are too compressed to do the project justice though...
Uploaded some less compressed pictures, hope they look a little better.
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Old 28th January 2006, 05:45 PM   #4
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Ha! I like it, oh yes indeed I like it. Reminds me a bit of Bert's Quasars, albeit with the additional wings and a distinct lack of BSC requirements. Very impressive Martin.

Best
Scott
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Old 28th January 2006, 07:56 PM   #5
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Monty Python
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Old 28th January 2006, 08:20 PM   #6
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Not Monty Python....Bullwinkle!!!!!
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Old 28th January 2006, 08:25 PM   #7
ScottG is offline ScottG  United States
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Originally posted by kestrel200
Not Monty Python....Bullwinkle!!!!!
Thats:

"..and now here's something we hope you *really* like." (in Rocky's voice)
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Old 28th January 2006, 09:04 PM   #8
Rudolf is offline Rudolf  Germany
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MJK,

the pictures donīt show as much OB as their title promised. What about the "open boxes" behind the drivers? Was that what you meant by "OB"?

Nevertheless ... itīs good to see another expert of loudspeaker theory engaging in dipoles. There still isīnt an exhaustive tool for OB design under room conditions

Rudolf
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Old 28th January 2006, 10:14 PM   #9
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Quote:
or DX4 driver and two Dayton 15" high efficiency woofers (JBL 2226 clones) per side
Are those high Qts drivers or you are using active EQ? JBL2226 won't work in OB, but I suppose those Dayton are high Qts drivers.

I've been planning a similar project for a quite some time, but using two 15 inch 4 ohm car drivers per channel. Monacor has very nice 0,9-1,2 Qts, high power and long excurtion 12 and 15 inch car drivers.

Is your open baffle calculator avaiable for free?

Great project!!!

Bartek
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Old 29th January 2006, 02:42 AM   #10
MJK is offline MJK  United States
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Quote:
Monty Python
Cal gets the correct answer, vintage 1970's English humor which I watched regularly in college ..... usually with a beer or two.

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the pictures donīt show as much OB as their title promised. What about the "open boxes" behind the drivers? Was that what you meant by "OB"?
The front baffle is 48" tall by 24" wide. There are "sides" that extend 12" back and a pair of braces at the top and bottom to stuffen the structure. Then there are 18" wide wings mounted on hinges that can swing out to make the total front 60" wide. The assembly is open along the back and at the top, is that something other then an OB design? Maybe I am missing something or using a definition incorrectly.

Quote:
Are those high Qts drivers or you are using active EQ? JBL2226 won't work in OB, but I suppose those Dayton are high Qts drivers.
The Dayton drivers have the same T/S parameters as the JBL 2226 drivers, these are low Qts drivers. This is why I am using two in parallel, I get the SPL up at low frequencies using two drivers and a boost and then roll them off with the crossover. I like low Qts drivers and there is no EQ other then the volume boost.

Quote:
Is your open baffle calculator avaiable for free?
It will be one of my new worksheets planned for release starting in March, unfortunately the new worksheets will not be free. The OB worksheet takes into account the driver positions on the baffle, the crossover and boost, the baffle geometry, and the floor reflections.
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