DIY: Dipole 8" array with Neo 130cm Ribbon

[Bent]

Well, all i can say is that i will have to test and measure. I figured some sins might be forgiven by using a 1st order slope initially and almost brickwalling at a certain point above/below that.

Currently the top of the ribbon is at ear level however will sit 40mm higher than the photo shows.

My experience with my RD75's was the increadibly limited verticle dispersion and for this reason, with the much shorter ribbons, I specifically built the speakers to be suitable for someone up to 6'1" to be able to stand within 1m of the panel and not loose too much top end. Thats my theory anyway, lets see what the reality brings......

Additionally I also tried to get the listening position about right. This might be a rehash of an earlier post....I can't quite remember.

[Few]

Test and measure, indeed. That's the name of the game. (Of course there's listening too, but I consider that part of the testing.) The "shallow slope at the crossover point with steeper slope at some distant frequency" trick was used by Apogee, as I recall. That would put you in good company. My first listening experience with Apogee Duettas remains clear in my memory. It was in the top two or three audio "holy crap!" experiences I've accumulated. A lot of supposedly VERY high end systems have left me flat, but the Duetta demonstration I heard really did it for me. They didn't have very tall mid/treble ribbons, by the way... Nonetheless, when I first walked past the door leading to the Duetta listening room I was compelled to turn around and figure out what was making such lifelike music.

Are you planning to tilt your speakers back at the top, or just raise the ribbon away from the floor?

I think there's an unjustified preoccupation with "textbook" filter curves--those that fit some analytically convenient definition--leaving other promising options untapped. So more power to you! I'm looking forward to hearing what you find when you start firing things up. By the way, what system will you be using for the crossover and room correction?

Few

[Bent]

I totall agree FEW, however I am trying to not reinvent the wheel, there is science behind the design. I have a couple of areas of compromise that I am hoping will not manifest as an audiable detraction from the goal.

Areas such as: distortion in 60-150Hz range of Dipole (Could be less with Seas Excel drivers etc), length of ribbon, output in Bass (only 500w rms available per side and small 100L cabinets).

In a nutshell, I have applied "good enough" where "optimal" was not available or would not fit into the non audio criteria such as appearance, size and cost. Already the components alone are ~ the AUD $5K mark and I bought very well......

It is good to be aware of possible deficiencies in the system because I may not be aware of them. That being the case, my basis of design did not account for them. Better to know now before I complete should minor changes lead to significant benefit.

So, I welcome all critique.

As mentioned, I have a powerful DSP built in to the amps on both channels. All manner of crossover slopes are available. Importantly I can daisy chain parametric equalisers, step filters, delays, you name it and these can be done pre or post crossover as well!

I am hoping that the cut corners were cut where it counts for little......we will see.

[Bent]

Regarding verticle dispersion, I dont think I hardly go any floor or ceiling bounce with the RD75's....that was one of the beautiful things. Horizontal dispersion was wide, but not at all frequencies - got quite directional above 5-8K if I recall correctly... Nonetheless, they are a speaker I would use again though a 600w rms/ch 8ohm amp would be used! (This is what I used last time and it made perfect use of it!)

ALSO: The panel in the photos is 1835mm tall and will sit on 25mm base + 15mm feet. Total Height 1875mm. Ribbon looks like it starts 20mm from top but actually starts 65mm from top, so that the top of the ribbon is 1810mm ~ 6'0.375" off the floor.

I may try tilting back but I dont think I will need it, maybe tilting forward though when sitting down??

Test, listen measure and repeat many times....!

[Baldin]

Hi cowanaudio

Could you tell us a bit more about your panels.
You say it's made by David Graebener, so it's maybe a prototype for the Rush models?
How wide are the ribons playing area?
How wide are the whole driver panel?
Does in incorporate extra tweeter windings in the middle of the panel (like some of their patents suggests) including a filter?

How high are the panels?

I once heard the Rush M75, and must say it's some og the best sounding speakers I have ever heard

More pictures would be great

I've planned to build someting like these for some time ..... will have to do some real work about it soon
Thanks in advance

Beat regards Baldin

[Calvin]

Hi,

when placing basses in close proximity to and on the same baffle as dipolar radiating ribbon or ESL the Ribbon/ESL moves with the soundwaves. This is especially problemtic when the bass hits the resonance frequency of the planar driver. ESL-diphragms may hit the stators, ribbons may undergo large excursions. In any case, there might be a quite sharp null in freq-response (so sharp indeed, that most diy measuring stuff doesn´t even recognize it!).
One measure against this is to have separated baffles for bass and planar drivers, or at least kind of ´slot´ between them.

8x 8" drivers work well in a dipole cabinet for rooms up to ~35-40m²
You probabely won´t need any dedicated subwoofer. But if You use a sub anyway smaller drivers (7"-5") would have been a better choice.

The amplitude response of a dipolar bass is far from linear and has to be equalized. Especially so, when You use a folded baffle to get more bass extension.
Best would be to keep the bandwidth rather small, i.e. don´t go up too high in crosssover-frequency. The lower You can cross over to the planar the better it sounds. Raising cr-freq You have to keep an eye on the distance of bass and planar.

jauu
Calvin

[cowanaudio]

G'day Baldin

[QUOTE]Originally posted by Baldin
[B]Hi cowanaudio

>You say it's made by David Graebener, so it's maybe a prototype for the Rush models?

The panels have little in common with his commercial offerings. Sensitivity is higher than the Rush.

>How wide are the ribons playing area?

~38mm

>How wide are the whole driver panel?

102mm

>Does in incorporate extra tweeter windings in the middle of the panel (like some of their patents suggests) including a filter?

No.

>How high are the panels?

There are three that make up a 2M tall array.

>I once heard the Rush M75, and must say it's some og the best sounding speakers I have ever heard

David has been involved in some excellent products over the years.
I've not heard his latest offering, the Wisdom L150i, but I'd put my money on it being an excellent real world solution for high end audio and home theater.

Cheers

William Cowan

[cowanaudio]

G'day again Graeme

Have you had a chance to fire up your new system yet?

Cheers

William Cowan

[Clarkcr]

Hey Bent, looking good. How deep will your cabinet be? How did you calculate it. Are you worried about wrap-around and soundwave cancelation?