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Multi-Way Conventional loudspeakers with crossovers

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Old 26th October 2013, 09:47 AM   #71
ODougbo is offline ODougbo  United States
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That is very good news for some of us; 3 set of 40 liters boxes in the HT. I'll need to modify 6 drivers. Back in the day we used Lacquer Thinner to break the glue down for removal.
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Old 26th October 2013, 10:37 AM   #72
ODougbo is offline ODougbo  United States
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Yup....pretty easy, about 10 minutes or so.
The exposed part of the voice coil is about an 1" deep, can see why a modification is needed.
Thinking MDF mini disk, with a pointed wood dowel; paint it all black or something.
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Old 26th October 2013, 10:44 AM   #73
tvrgeek is offline tvrgeek  United States
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If you got the cap off, then just round over (1/4" radius should do) a bit of dowel. To clear the glue left after pulling the screen off the pole piece, carve a bit of relief in the back end. Then mount it with a long screw and washer through the pole piece vent. Paint as desired. I went through a lot of trouble to get a very precise side fit, but I am not sure that is really necessary.
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Old 26th October 2013, 11:17 AM   #74
ODougbo is offline ODougbo  United States
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So far so good with small disks :-)
Long screw - really? Won't a steel bolt change magnetic field or something?

1/4 in.-20 x 3 in. Nylon Hex Bolt-16388 at The Home Depot

Last edited by ODougbo; 26th October 2013 at 11:20 AM.
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Old 26th October 2013, 04:12 PM   #75
tvrgeek is offline tvrgeek  United States
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In theory, yes. In practice, not at this level. Use a brass screw if you want. They cost more. I did not use glue as I did not want to risk gluing the voice coil. Remember O BETTER CHEAPER.

I am going to model a few other crossovers this afternoon. Can I make a first order at 2500 work? Not having the Q to play with, my hunch is no, but that is what this is about, finding the cheapest solution.
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Old 26th October 2013, 06:22 PM   #76
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first order network useless for suppressing signals in tweeter's resonance range, resulting in poor performance above very low power levels.
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Old 26th October 2013, 06:50 PM   #77
tvrgeek is offline tvrgeek  United States
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Not at all worried about the tweeter resonance. With the modified woofer, I shifted the crossover up to 2 to 2.5K range. Of course, 5K is more like where I would normally look to do a first order. But in the concept of CHEAP, worth a try. Terrible results. All it cost me was my time.

I also played with best I could do. For about three times the cost, I could model (based on in-box real measurements) within a dB 100 to 10K. 13 parts and reduced the efficiency a couple of dB. Totally out of scope for budget. It can be done.

Parts I decided on are 2.7mH and 8.2uF on the woofer, 4.7uF and .55 mH on the tweet with a 5.1/4.7 pad. A little of the 3.3 breakup still shows, and a little of the diffraction hump is still there, but for a CHEAP build, I hope it will be pretty good. This is based on the slit/doped woofer. Bottom end was stronger, box smaller. Almost as good as the phase plug. Easier by a lot. Parts will take about a week to get here, so don't wait up on the results.

Woofer mod: I cut 6 radial slits from the edge of the cap to about a quarter inch from the center, Then applied a pretty heavy coat of silicone to just the cap. Resonances moved up with the slits, and back down to 3.3K with the silicone, but lower in amplitude by a lot. T/S for the entire driver did not change much.
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Old 26th October 2013, 07:28 PM   #78
system7 is online now system7  United Kingdom
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I make that about 2.6kHz crossover, which is OK. It all looks OK on frequency response too. My modelling is rough and ready, of course.

I still like my 5kHz tank on the woofer, and I think you should try it. Phase isn't IMPORTANT...it is EVERYTHING!
Attached Images
File Type: png tvrgeek-1-Circuit.PNG (8.2 KB, 66 views)
File Type: png tvrgeek-2-FResp.PNG (37.9 KB, 68 views)
File Type: png tvrgeek-3-phase.PNG (32.7 KB, 67 views)
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Well, there it is! Best regards from Steve in Portsmouth, UK.
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Old 26th October 2013, 07:49 PM   #79
tvrgeek is offline tvrgeek  United States
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Ah, you are using the unimproved OEM woofer plots. My phase plug or slit/doped version does not have the breakup at 4.4K. (it has a much smaller one at 3.3 I am going to ignore for now) By the model, a notch is not needed there.

Now on to phase, I am not really sure what I am looking at. I'll gladly take whatever help you can provide.
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File Type: jpg Solution2-amp.jpg (435.8 KB, 65 views)
File Type: jpg Solution2-imp&phase.jpg (421.7 KB, 60 views)
File Type: jpg Solution2-outputphase.jpg (469.3 KB, 8 views)
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Old 26th October 2013, 10:24 PM   #80
system7 is online now system7  United Kingdom
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I was using a TYPICAL 6" paper woofer at heart. Your sliced and doped dustcap is taking you into deep scanspeak water indeed:
Vibration analysis

I learned more from that article than almost anything I can think of apart from Lynn Olson.

Hard to say what your dustcap mods are doing. They may add a certain amount of rolloff and damping to the AAL3 resonance. You'll have to model it to see what combination of electrical and mechanical damping works best.

Phase is easy, once you get it. Keep the drivers phase aligned throughout the overlap region. I can't explain it more simply. Just occasionally, drivers play beautifully together, as below:
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File Type: png 7_Series_Filter_Phase.PNG (18.2 KB, 21 views)
File Type: png 7_system7_Time_Aligned _Filter.png (16.1 KB, 23 views)
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Well, there it is! Best regards from Steve in Portsmouth, UK.
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