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Multi-Way Conventional loudspeakers with crossovers

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Old 30th July 2010, 09:25 PM   #6891
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Why did you hang the insulation on either side of the speaker? Are you going to use those in the final design or where you trying to remove the effects of the baffle on the speaker's response? However you put them behind the round over on the baffle, so I don't quite see the point...?
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Old 30th July 2010, 09:34 PM   #6892
g3dahl is offline g3dahl  United States
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It's not part of the design; I was just trying to minimize the impact of other stuff in the room, especially in the area behind the speakers. After taking the 90 degree measurement, I did an overlay and repeated it without the insulation. It only made a minor difference -- some of the nulls in the LF area weren't as deep.

Gary Dahl
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Old 30th July 2010, 09:54 PM   #6893
mige0 is offline mige0  Austria
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Good job - thanks for sharing some data Gary

Michael
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Old 30th July 2010, 10:11 PM   #6894
mige0 is offline mige0  Austria
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Quote:
Originally Posted by g3dahl View Post
I'm no expert when it comes to using ARTA.
Me neither
One or two remarks if you allow

If your mic is not calibrated in SPL you better state that explicitely as otherwies people would think your were measuring at the 110dB SPL shown - which most likely was not the case ??

Regarding distortion measurement - same as above (you know, distortion varies heavily with SPL).
Also distortion seems to be veeeery low, so might be something else went wrong ??
Can't figure out at the moment....

Whats the gating time for the polar plots? - from the roughly 100 Hz indecator it seems you have included a lot of room response - so you might cut shorter - roughly 3ms at best I'd guess for the setup shown. (you can check in the impulse response where first reflections arrive and slide window accordingly)

For low frequencies (below the indicator) you possibly want to make a close mic measurement too (if that department is of special interest for you)...

Michael

Last edited by mige0; 30th July 2010 at 10:38 PM.
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Old 30th July 2010, 10:57 PM   #6895
g3dahl is offline g3dahl  United States
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Hi Michael,

Thanks for your remarks. I was most definitely not measuring at 110 dB! My mic preamp gain is set up for proper calibration with the software, but the gain of the power amplifier isn't accounted for in the ARTA settings. This was the first time I had used the distortion measurement option, so I don't doubt there is more to learn about it.

The gating times were indeed long, but I don't have the figures anymore. The reflection wasn't clear, which is why I tried the insulation next to the speakers. In any event, I had to put everything away to prepare for my daughter's horn lesson this afternoon, but look forward to setting it up again and trying some more measurements.

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Old 30th July 2010, 11:42 PM   #6896
cuibono is offline cuibono  United States
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Wow, that is pretty nice. Off axis looks amazing.

One little tidbit - if I were going to do these off axis measurements, I would do them outdoors, about 10 feet off the ground, at either 1 or 2 meters - I've found that works well for mid to low frequency measurements, in terms of avoiding reflections. Gate in the area of 15 to 40 ms. I like to do them with a 2.83Vrms terminal voltage. Any idea what the sensitivity of these are?

Although I already have plenty other projects to work on, this project has me very interested!

Last edited by cuibono; 30th July 2010 at 11:44 PM.
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Old 31st July 2010, 12:58 AM   #6897
g3dahl is offline g3dahl  United States
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Originally Posted by cuibono View Post
I would do them outdoors, about 10 feet off the ground, at either 1 or 2 meters
Oof! Someone else can hoist 'em up there!

Yes, that would certainly yield cleaner measurements...

Lynn and Michael have given some suggestions (online and off), which I will put to use when I set up the next ARTA session.

Gary Dahl
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Old 31st July 2010, 01:06 AM   #6898
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Thanks Gary! Looks like a 1k max upper limit, but lower would be better. Off axis response os so telling. The first graph looked smoother on axis. Maybe I better go have another look. You could probably get that cone to settle a bit further through damping and make the crossover easier if you are crossing over high.

Oh, I personally like a 5dB scale for a bit more detail when I do graphs.

Thanks again,

Dan
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Last edited by dantheman; 31st July 2010 at 01:11 AM.
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Old 31st July 2010, 01:18 AM   #6899
g3dahl is offline g3dahl  United States
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Originally Posted by dantheman View Post
The first graph looked smoother on axis.
Yeah, I thought so too. Lynn says it's all contaminated by the long window and early reflections that ought to be minimized, so we can't tell much from the graph. I'll work on the setup some more and see if I can get things cleaned up.
Quote:
You could probably get that cone to settle a bit further through damping and make the crossover easier if you are crossing over high.
No plans to cross over high, but I do want things to be as well-behaved as possible for a good distance beyond the band I'm using.

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Last edited by g3dahl; 31st July 2010 at 01:26 AM.
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Old 31st July 2010, 02:02 AM   #6900
CLS is offline CLS  Taiwan
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Trade off, as always.

TD15M has coating on its cone already. Further damping might probably add too much mass and affect other performances (in negative ways).

And that measurement is already excellent for its size, isn't it? Or, TBH, I've never seen any better 15"er in this regard.
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