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Multi-Way Conventional loudspeakers with crossovers

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Old 25th March 2013, 08:53 PM   #21
tvrgeek is offline tvrgeek  United States
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Quote:
Originally Posted by dayvo View Post
Here's the listening position frequency plot.

Honestly, the plots jump all over the place depending on orientation of the mic. This is using AudioTools on my iPad.
Now you are seeing first hand how important the room is to your measurements and the limitations of some tools. To see what the speaker itself is doing, you need to get outside AND learn how to use gated measurements for the high end, sweeps low, and merge them. H-B transform for the phase and then see what the simulators can help with for the crossover. Oh yea either a very flat mic, or a calibrated one. Most condenser mics are pretty flat in the crossover region, so calibration really only helps understand the lowest and highest octaves. I have no idea how flat the iPad mic is.
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Old 26th March 2013, 01:30 AM   #22
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“NB can you expand what direction you went in?”
Oh me !!!!!!!!!!!!!
I usually see when someone says norman……..

I sent you (dougbo) an email.
I don’t want to get off topic.

I like where this is going.
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Old 26th March 2013, 09:41 AM   #23
ODougbo is offline ODougbo  United States
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I couldn't take the pressure I ordered a pair of the 8" 8ohm.

Don't tell - you know who....

Will try some test boxes, various sizes.
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Old 26th March 2013, 02:07 PM   #24
dayvo is offline dayvo  United States
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I started looking at the impulse response measurement option in AudioTools last night. Thanks for the suggestions. It will take me a couple of days to get back to it and reach the point of taking more measurements.

I can't hear any sound from the pole piece vent in the 8", but it is quite a bit more efficient than the 6.5", and with my low power SET amp, it's probably below a watt of power almost all the time.
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Old 26th March 2013, 07:11 PM   #25
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8" 4ohm sound great to me.
I'm crossing 24db@2khz LR (for directivity).
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Old 26th March 2013, 09:54 PM   #26
sreten is offline sreten  United Kingdom
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Hi, Line level passive BSC is probably a very good idea, rgds, sreten.

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Old 29th March 2013, 02:34 PM   #27
dayvo is offline dayvo  United States
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Here's my first attempt at an impulse response based measurement. This is in-room and smoothed at 1/3 octave. It was taken about 4 feet in front of the center of one speaker - only that speaker operating. Looks like better data than my previous attempts. Makes me think the tweeter should be padded down a few dB.
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Old 29th March 2013, 06:57 PM   #28
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Looking at the link I posted on the last page again, I noticed it says it only lets you trim down to 0.5 seconds. You need more like 0.005 s, so that ain't gonna work for removing reflections.
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Old 3rd April 2013, 02:02 AM   #29
dheming is offline dheming  United States
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The DM944 pair I had back in 2008 used a 3.3uF PX Clarity Cap and the polarity on the tweeter was inverted. The port tube measured 2.05" ID x 3.58" L and the internal dimensions of the enclosure were: 8.50" D, 7.28" W, 14.50" H. Not sure of what changes were made for the DM945 model.
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Old 3rd April 2013, 03:32 PM   #30
dayvo is offline dayvo  United States
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The DM945 has external dimensions of 9" x 10" x 16" so, assuming 3/4" material, internals are 7.5 x 8.5 x 14.5. That works out to 15 L (.53 cu.ft.), which coincides exactly with the Silver Flute recommendation on the Madisound site. I built using a 2.0" ID x 3.75" long port tube (actually 4" long with a 1/4" radius on the outside end).

I used a 3.9 micro F Clarity Cap (SA) to shoot for 3 dB down at about 8kHz. The 3.3 you mention seems like too high a crossover freq., but what do I know?

I also inverted the tweeter connection, but that was because of a comment on the Parts Express website saying that the Hi-Vi tweeter terminals are marked backwards. The logic given was they expect people to use 2nd order crossovers which have 180 degree phase shifts, so they compensated with the markings. Not sure I believe that, but subsequent response measurements confirm that the inverted connection is correct.

dhemming, how did you like the sound of the 944's?
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