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Old 28th September 2008, 12:32 PM   #1
ojg is offline ojg
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Default My Seas DXT + SS18W speaker

Hi all!

This summer I made a pair of speakers, the second set of diy speakers I have made. It's a bass-refleks floor-standing 2-way. I already had the ScanSpeak 18W/8545K00 and then I wanted to try the SEAS DXT tweeter.

The cabinet is approx 17L and 85cm tall, and has the port tuned to 35Hz built into the front of the enclosure and exits at the floor. The front slants back about 5 degrees.

The bottom of the enclosure has room for an amplifier to be built in, as an active speaker with dsp xover is my ultimate goal. However I made a passive xover so that I could start using the speakers right away.

They sound great with excellent stereo imaging and deep powerful bass in my 25m^2 room.

I hope someone finds this useful and get some inspiration from it.

Thanks,
OJG
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Old 28th September 2008, 12:38 PM   #2
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The speakers are made from 15mm birch plywood to match the furniture in the room: Improved WAF
Then bitumen is added to all the walls, and one or more layers of acoustic wool. Here is a picture taken before all the damping is added and the back is mounted.
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Old 28th September 2008, 12:49 PM   #3
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My xover deign method is maybe a bit unusual. I use a combination of LTSpice and Matlab to design and optimize the xover. I did my measurements in my living room with Dennis Sbragions rec_imp. This limits the 0.5m measurement to above 500Hz.

I optimized the xover for acoustic LR4 at 1800Hz.

Here is the woofer response spliced with nearfield response below 500Hz. Blue is the driver response, pink is the target curve and green is the simulated response with the xover.
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Old 28th September 2008, 12:53 PM   #4
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Same for the tweeter. Another design goal was to use as few components as possible since this was going to be a "temporary" filter.
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Old 28th September 2008, 12:57 PM   #5
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Here is the simulated complex summed response. I thought this looked pretty good, so at this time I went ahead and built the xover.
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Old 28th September 2008, 01:09 PM   #6
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After building the xover, it's time to verify the result. Here are the individual responses and the target curves. Not bad.
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Old 28th September 2008, 01:19 PM   #7
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And the complete speaker response this time at 1m, exept the port response is not included.

I did not have very high expectations for a passive xover design, but I was pleasantly surprised at how well it came together in the end.
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Old 28th September 2008, 01:46 PM   #8
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Finally here is the xover schematic. After doing this design I now have more respect and interest in the craft of passive xover design.
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Old 28th September 2008, 10:11 PM   #9
Elbert is offline Elbert  Norway
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Default Nice!

Just wanted to say that those speakers really look nice, a tastefull and well proportioned design in deed!

And considering the design and drivers used, I'm not surprised that they sound good to!

let us know how the active amp and filter solution turns out!
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Old 28th September 2008, 11:12 PM   #10
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Default Excellent project

Very nice speakers!

We are on the same track. I am making speakers using a SS15W and the SS6600 tweeter. The tweeters are mounted to the back of the baffles and I am carving waveguides on the front. They will function very much like the DXT waveguide. Currently my prototypes are only rough MDF boxes.

Like your project, I am starting with passive crossovers (which has been a learning experience for me too). Later I will go to active crossovers as well, but I will probably use an analog op-amp configuration.

I look forward to your results with the digital crossovers.

Thanks for posting your pictures, it is encouraging me to continue working toward a nicely finished speaker.
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