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Old 1st July 2012, 07:58 PM   #21
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Or Neo10. Or RD-40.
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Old 1st July 2012, 07:59 PM   #22
OllBoll is offline OllBoll  Sweden
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Quote:
Originally Posted by RockLeeEV View Post
And after gradient losses we're probably looking at even less!

FWIW the Seas M15CH002 is pretty damn good....



A 6.5 inch driver playing up to 2khz? No offense, but I think your design has some priority issues....
It doesn't seem measure that well though : /

In Zaphs 5 inch test the hexadym measures about the same as their normal magnet. And in his test with the W18NX compared to the 6ND430 is has way more odd harmonics, less xmax and less sensitivity.

The issue is the rear magnet of the 6ND430, but that might be able to be compensated hence this thread =)
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Old 1st July 2012, 07:59 PM   #23
Jonasz is offline Jonasz  Sweden
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B&G Neo10 should work well in this design, right?

BG, Neo10
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Old 1st July 2012, 08:01 PM   #24
OllBoll is offline OllBoll  Sweden
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Originally Posted by RockLeeEV View Post
In terms of importance, the forward horizontal polar / power response eclipse the back wave 0 deg response (your apparent focus).

Why not use an actual dipole driver, like the BG Neo 8 in free air? There will be no magnet structure to worry about.
The problem with them is that they only have horizontal dispersion, they are not point sources which is is what I'm trying to build.

If I wanted a line source I too would just get an RD-75 and call it done
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Old 1st July 2012, 08:04 PM   #25
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RD-75 would probably be the last speaker you'll ever buy. I mean...you wouldnt want anything else.
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Old 1st July 2012, 08:44 PM   #26
OllBoll is offline OllBoll  Sweden
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If directivity at 2 khz becomes too much of a problem I could probably cross lower, I'm off tomorrow to buy one of the tweeters I plan to use to measure myself and see how it works.

What makes me hope that the 6.5 inch driver can work up to 1800-2000 hz is the dipole peak, if the driver is used without a baffle then according to Edge the dipole peak should be right in the middle of 1800-1900 hz.
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Old 1st July 2012, 08:52 PM   #27
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It has been discussed before on this forum that the dipole peak of a nude driver will happen somwhat lower than expected, because the effective path length will be greater than just the diameter of the driver chassis.

This is a measurement of a Seas W15CH001 5" midrange, dipole with no baffle. Dipole peak around 1600 Hz....

Click the image to open in full size.
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Old 1st July 2012, 08:55 PM   #28
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Originally Posted by OllBoll View Post
It doesn't seem measure that well though : /
Where was it measured? And which parameters relevant to perception were measured?

Quote:
In Zaphs 5 inch test the hexadym measures about the same as their normal magnet.
so?

Quote:
And in his test with the W18NX compared to the 6ND430 is has way more odd harmonics
Um, sure, Here is the W18NX:

Click the image to open in full size.

and the 18 sound

Click the image to open in full size.

All distortion for both drivers is less than 50db below the fundamental in the relevant passband for a 6.5" driver mated to a flush tweeter (< 1.6khz). Neither motor exhibits any untoward issues.

The rising 3rd and 4th harmonics for the Seas are not flux or motor distortion (IE anything that might indicate increasingly audible consequences as SPL rises); they are a function of the rising frequency response magnitude caused by the cone material. It's not a perfect driver, but it's got a very good motor that keeps non linear distortion well below audibility in its passband.

No conclusions WRT sound quality or usefulness can be drawn from these H.D. charts between these two drivers, unless you listen with your eyes and not your ears.

Quote:
less xmax
Does, and How does he actually test xmax? Or are we comparing manufacturer spec - of which there are a billion different methodologies for coming to an arbritrary xmax number for the spec sheet? Either way though, the W18 Nextel somehow according to zaph has two more mm xmax than the 6ND430.

Quote:
less sensitivity.
Well yes! The W18 uses a heavy (pistonic) magnesium cone and the driver as a whole has been very well damped with SQ and extension as a priority.

You put a light paper cone on that motor and optimize the soft parts for output over excursion, you'll get your sensitivity at the cost of xmax and possibly resolution - as John Janowitz' measurements of the 18sound show:

Click the image to open in full size.

You've got a bunch of unaddressed resonances. They may not look bad on the "harmonic distortion" chart but unlike the HD, these may be evident in listening as a smearing of the sound. Here is the impedance closeup of the M15's sibling the W15LY:

Click the image to open in full size.

To me it looks like it probably has less any visible resonances.

It really doesn't affect me which driver you want to use, as I'll just have fun reading the thread etc, but I think you should be careful when you say x measures better than y. Not everyone thinks Zaph Audio measurements are the holy grail, or even that they correlate well to subjective impressions. They'll separate the wheat from the chaff and they can be used to derive FRD files but that's about it.

Anyways the M15 is a ~5 inch driver rather than an ~6.5" driver like the 18 sound. So you will lose some efficiency (about 3-4db? ). it's one price to pay for wider or more dipolar dispersion.

Quote:
The issue is the rear magnet of the 6ND430, but that might be able to be compensated hence this thread =)
And that "issue" could be addressed well........ with that "measures the same" hexadym neo magnet

Last edited by RockLeeEV; 1st July 2012 at 09:13 PM.
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Old 1st July 2012, 08:59 PM   #29
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Originally Posted by OllBoll View Post
The problem with them is that they only have horizontal dispersion, they are not point sources which is is what I'm trying to build.
huh? the Neo8 is virtually the same hieght as a 6.5 inch driver, give or take an inch or two. My Dennis Murphy Philharmonic 2s use it up to 2.8khz without "line source sound" / integration issues. If your definition of a "point source" includes using a 6.5" woofer up to 2khz, then using a ~7" or 8" tall, ~3" wide midrange is no different. Now if you want a true point source, then you need to be looking at much tighter driver spacing and significantly smaller drivers.
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Old 1st July 2012, 09:43 PM   #30
OllBoll is offline OllBoll  Sweden
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Quote:
Originally Posted by StigErik View Post
It has been discussed before on this forum that the dipole peak of a nude driver will happen somwhat lower than expected, because the effective path length will be greater than just the diameter of the driver chassis.

This is a measurement of a Seas W15CH001 5" midrange, dipole with no baffle. Dipole peak around 1600 Hz....

Click the image to open in full size.
Hmm, thats interesting.

If so then the TB75 might be the best choice after all. Best is probably to wait until I get my midbass woofers here ( got 2 W26FX002 on discount ) and see how far up I can push the crossover on the bottom end.

if I can get it up towards 500 hz then the TB75 might work instead, since I'm not trying to get cinema SPL. The TB75 should be better on the top end but then there is the problem that the dipole peak would be right in the middle of the frequency range at about 1200 hz.

Quote:
Originally Posted by RockLeeEV View Post
huh? the Neo8 is virtually the same hieght as a 6.5 inch driver, give or take an inch or two. My Dennis Murphy Philharmonic 2s use it up to 2.8khz without "line source sound" / integration issues. If your definition of a "point source" includes using a 6.5" woofer up to 2khz, then using a ~7" or 8" tall, ~3" wide midrange is no different. Now if you want a true point source, then you need to be looking at much tighter driver spacing and significantly smaller drivers.
But with a Neo8 I get a sweet height which is exactly what I want to design away. And it wouldn't be constant directivity at all since the horizontal dispersion would be awful. I want to have speakers that just spread music all over the room, so I can enjoy wherever I'm listening on axis sitting in a chair or I'm standing in the other side of the room.

And I'm not convinced that beaming at 2 khz is really a problem, so the current plan is to use 8 cone tweeters in 2 rings of 4, one on each side of the midrange(s) to ensure good dispersion up to 15 khz.

Last edited by OllBoll; 1st July 2012 at 10:04 PM.
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