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 Post subject: Re: NEW PLANAR SPEAKERS
PostPosted: January 13th, 2016, 1:32 pm 
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Joined: December 14th, 2013, 2:19 pm
Posts: 948
tomp wrote:
Stuart Polansky wrote:
As I'm attacking this project again, some details are being worked out.

It will be three-way with a shallow sealed enclosure on the inboard side for four Dayton RS180-4 midbass drivers, 60Hz-~1kHz. The line array of 6 Neo8s will take over from ~1kHz to ~6kHz, the Maggie ribbon, robbed from the Tympanis will operate from ~6kHz up.

Because of efficiency and impedance differences, this is definitely an active crossover project. Since the Neo8's can be wired as 2.7 ohms, they actually match the Maggie tweeter without the attenuating resistor. Hoping to make that XO point work passively, we shall see.

Bass below 60Hz will be in a separate enclosure.

Big questions are:

1) How close to the edge of the panel can I mount the ribbon? does panel strength alone control this, or is there a sonic issue? OB guys (Roscoe?) please feel free to comment here.

Probably what is more important here is the shape of the edges of the panel. In my situation I use a long gently curved baffle on one side and a short but rounded edge on the other. In either case, sharp edges are to be avoided but the radius of the curve depends on the frequency. A small radius is OK for high frequencies but as the frequency decreases the radius must get larger.
Edges will be rounded, but curving panels is beyond my expertise, flat will have to do. In fact, the rear openings for all of the drivers will also be "radiused".

2) Is there a detriment to using a shallow enclosure behind the midwoofers? They are 7" and will be in a sealed 2.2 cubic foot box, 6' tall, and about 11" wide, 5" deep (internal). They will be heavily braced and treated with Acoust-X.

I would not use an enclosure behind the midwoofer. With the Neo 8s being used in a dipole arrangement it is better is you can keep the radiation pattern the same by using it in a dipole configuration. The best results with speakers has always happene when all drivers have an acoustic radiation pattern that is the same or at least the same in the crossover regions. My configuration is dipole for the RD75s and mid bass drivers with the subs in a sealed box. BTW I saw that Parts Express says that they can no longer get the Neo 8s. Que Pasa?

BG stopped selling to DIY people when the company was sold. I have the Neo8s. I need to reduce my panel width, not increase it. No room do OB in the lower frequency regions. Subs will cut off @ ~60Hz, panels have to hit that and be no wider than 24". Compromises. Many a hybrid electrostatic speaker uses enclosed bass drivers, either ported or sealed. They sound pretty good to me. Granted, the XO point is probably a few hundred Hertz, not 1-2kHz.

BTW, final XO points will be chosen using multi-amps and the DCX2496. Great for experimenting, just not good for sonics.


All 0.75" birch plywood. Panel thickness is doubled. Box will be braced on 7" centers with horizontal braces, each containing two rounded edge 4" holes. Top and bottom panels will be attached to the first brace with a 1" dowel in the center of the brace.


Roscoe, IF a passive XO is built between the ribbons and Neo8s, the Neo8s will be wired for 2.7 ohms, so there will not be a significant impedance mismatch, less than 0.5 ohms. But your point is well taken, for amps with output impendances >0 (LMAO).


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