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In Reply to: RE: DIY speaker design comments posted by Satie on March 29, 2014 at 11:15:53
Satie, wouldn't it actually be better to screw the 2.5 bass driver to the heavy wooden frame as tight as possible, and then separate the mids & high acoustically from the frame?
Edits: 03/29/14Follow Ups:
... which combine a pair of 2.5 bass panels with a pair of T-IVa mid/ribbon panels.Bass panel is screwed to a separate, braced, hardwood frame from the mid panel & ribbon - so there is minimal vibration transmission between them. When the bass is pumping, you can touch the top of the bass frame and feel the vibrations; touch the mid/ribbon frame ... and there is no vibration. :-))
Regards,Andy
PS: Next on the plan is to replace the T-IVa mid panel with a string of Neo 8s.
Edits: 03/29/14
Ok, thank you very much for all of you for your comments! It seems to be quite clear that plan B with separate subs is a better choice.
One more question; both the ribbon & 2.5 basses are about 1,5m high. 6 x NEO8 would "only" be about 1,2m, so mid area would be a bit shorter than both basses & highs. Does that actually matter? Should I go for 7 or 8 NEO's, or would that just make the wiring too difficult..?
AkuAnkka wrote:
"2.5 has a bigger bass than 3.x"
I am not sure if that is really true. The 3-series uses the full width of the bas+mid driver at the bottom. This is also a reason to why the mid can be polluted by the bass while it is doing heavy work.
About the number of Neo 8. To me it would feel better with 8 drivers in a line but it will probably not be of great importance soundwice. In theory, a long line source is more of a true line source. In this case it would better match the Magnepan ribbon tweeter. The mids of MG 20-series are all shorter than the ribbon tweeter.
But how long is actually long enough to be "true line source", if the range is from 400hz to 4khz?
And, could it actually be possible to leave ~5cm gap between the NEO's, to have 145cm length with just 6 NEO's?
You don't want to introduce greater gaps in the Neo8 line if you want to operate them to 4khz. There is already a gap in the radiating surface of about 3" for the driver flanges etc. That will start having measurable comb filtering effects above 5khz - but not yet audible since the direct output of the drivers is extremely directional with hardly any vertical dispersion. If you add another 2" to the gaps then it will become audible.
The fact of the output being so directional is what allows the line array to cancel out the resonance peak at 12khz. Since the resonance output does have a vertical component - it is not direct output, but reflected from the magnet board to the diaphragm and back at least once before exiting the driver.
Ok, thanks. 7 would actually be enough, but is it anyhow possible to wire 7 NEO8's to get a reasonable impedance?
7.5 ohms with 3 parallel pairs and one parallel set of Neo8 and 3.75 ohm resistor.
Quite frankly I would not bother with a single additional driver. I would go from 6 to 8 or stick with 6.
To be honest, 1.2 m is too short for tweeters but maybe you will realize that it is okey for the midrange?
That might be easier to do and provide you with some mass damping - so long as you get intimate contact between driver and frame.
Which ever way, the midbass is going to do allot of work - so whatever scheme you come up with should separate the mid and tweeter from that high energy.
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