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Driver Options for Gainclone powered Sub
Driver Options for Gainclone powered Sub
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Old 30th January 2007, 10:21 AM   #11
raromachine is offline raromachine  New Zealand
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Some new plots...

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Old 1st February 2007, 10:55 PM   #12
raromachine is offline raromachine  New Zealand
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I ended up going with a Jaycar CS2362 Sub - its an ugly affair, 12" diameter, but they were on sale for $60NZ at my local store and the specs looked better than the other models there for the price.

The magnet is pretty strong - at .5m from a CRT display there are all sorts of lovely colours and effects going on.

Unfortunately, I didn't take a copy of the specs with me, and they are old-stock (i.e. no longer on their website or in their mags). Can anyone help me?? :\
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Old 2nd February 2007, 07:04 AM   #13
raromachine is offline raromachine  New Zealand
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I found an older Jaycar catalogue, for the internet record the data for the CS2362 ( or CS-2362 ) is:

Nominal Impedance: 4ohms
Power Handling: 250W RMS
SPL: 90.2db 1 Watt @ 1m
Voice Coil Resistance: 3.8ohms
Fs: 32.5Hz
QMS: 6.338
QES: .36
QTS: .34
Vas: 59.13litres
Voice Coil Diameter: 59mm BASV
Xmax: 7.5mm
Speaker Dimensions:
A 319, B 298, C 285
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Old 3rd February 2007, 03:18 AM   #14
ocool_15 is offline ocool_15  Canada
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Quote:
Originally posted by raromachine
I found an older Jaycar catalogue, for the internet record the data for the CS2362 ( or CS-2362 ) is:

Nominal Impedance: 4ohms
Power Handling: 250W RMS
SPL: 90.2db 1 Watt @ 1m
Voice Coil Resistance: 3.8ohms
Fs: 32.5Hz
QMS: 6.338
QES: .36
QTS: .34
Vas: 59.13litres
Voice Coil Diameter: 59mm BASV
Xmax: 7.5mm
Speaker Dimensions:
A 319, B 298, C 285

That woofer is not very well suited to your intended enclosure at all. You can provide some equalization or go vented but your initial recommendations look better.
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Old 3rd February 2007, 03:33 AM   #15
raromachine is offline raromachine  New Zealand
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Sure - but it was cheap

I had planned to do a bit of experimentation - mostly down the Linkwitz transform route (see attached pic). I've checked the driver with this and found that a -3db point of 25hz means aroudn 12db. The excursion only gets to 4.5mm too.

If it turns out that I can't live with what the driver is giving me then I'll pony up the extra $$$ go and find another (better/nicer) 12" driver to suit the enclosure.

Just for completeness sake the specs sheet lists a couple of enclosures:

Small Vented Box: 25L
Tuning Freq: 36Hz
-3db point: 28hz
Port size: 66mm x 236mm

or

Large Vented Box: 60L
Tuning Freq: 29.3Hz
-3db point: 33.63 Hz
Port Size 50mm x 69mm


----

Forgot to say - thanks for your input
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File Type: png subwoofer-12inch-polycone-with-linkwitz-xform.png (38.5 KB, 142 views)
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Old 3rd February 2007, 10:33 AM   #16
richie00boy is offline richie00boy  United Kingdom
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Driver Options for Gainclone powered Sub
I think you'll find a 50mm vent tuned to 29Hz will be too noisy. I think a 66mm vent tuned to 36Hz will be problematic as well.
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Old 11th February 2007, 11:33 AM   #17
raromachine is offline raromachine  New Zealand
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Thanks Richie - I didn't notice your post, but if I do go with the venting I'll make sure I run it through the various tools out there.

In the mean time here is the box taking shape:

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Old 11th February 2007, 03:18 PM   #18
richie00boy is offline richie00boy  United Kingdom
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Driver Options for Gainclone powered Sub
Looks like a nice clean cut box.
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Old 11th February 2007, 04:29 PM   #19
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If I may throw in my two cents, be careful with the Linkwitz circuit, its not something you can throw at any old woofer. Though it does work well to extend bass flat to whatever frequency, it has the problem of using essentially a lot of EQ down low. As a result of boosting bass as it does, the woofer will draw more and more power and the cone will move more and more, taxing the xmax and power handeling. A woofer with a high power handeling, huge amplifier, and a lot of xmax handles these cuircits fine, and you get great results. However the woofer you have has very limited xmax and the power handeling and power amp situation is limited. This isn't to say it won't work, you just will be limited as to how loud you can play it. You can modle this effect in WinISD to see just how limited.

Basicly, plug in the power you want, and check xmax, keep raising or lowering the power until you hit the xmax, or are close. Then go check the spl screen, and that will tell you how loud the sub will play before exceeding xmax. It will also tell you if your amp will be adequate to drive it to that level.

How many amp chips are you running, with that chip, a stereo chip, I assume you are just going to parallel it, which will about double-120 watts, the power into 4 ohms. When you modeled it, did you put in 120 watts as the amount of signal?
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Old 11th February 2007, 10:02 PM   #20
raromachine is offline raromachine  New Zealand
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Quote:
Originally posted by pjpoes
If I may throw in my two cents, be careful with the Linkwitz circuit, its not something you can throw at any old woofer. Though it does work well to extend bass flat to whatever frequency, it has the problem of using essentially a lot of EQ down low. As a result of boosting bass as it does, the woofer will draw more and more power and the cone will move more and more, taxing the xmax and power handling. A woofer with a high power handling, huge amplifier, and a lot of xmax handles these circuits fine, and you get great results. However the woofer you have has very limited xmax and the power handling and power amp situation is limited. This isn't to say it won't work, you just will be limited as to how loud you can play it. You can model this effect in WinISD to see just how limited.
I had put the LW transform and the LP filter into WinISD - and it looked okay. I didn't quite grasp the input power thing.

At just under 12db gain and following the math on Rod Elliot's page I'm making a guess that the power the amp needs to drive the speaker to the levels for the low freqyencies doubles four times?

So 1W - > 2W -> 4W -> 8W -> 16W of power to give the same appreciable loudness at ~30hz at at ~55hz?

Quote:
Originally posted by pjpoes
Basically, plug in the power you want, and check xmax, keep raising or lowering the power until you hit the xmax, or are close. Then go check the spl screen, and that will tell you how loud the sub will play before exceeding xmax. It will also tell you if your amp will be adequate to drive it to that level.
Thanks - that's really helpful

I'm not sure exactly how I plugin the input power - I have setup the speaker with the 250W RMS specified on the spec-sheet.

Quote:
Originally posted by pjpoes
How many amp chips are you running, with that chip, a stereo chip, I assume you are just going to parallel it, which will about double-120 watts, the power into 4 ohms. When you modeled it, did you put in 120 watts as the amount of signal?
You're on the money there re: setup and output power - I've updated the thread under "ChipAmps" (linked to above somewhere) to show what I'm doing. The LM4780 is on a BIG heatsink, and at present I can't even make it warm to touch running at as much bass as I can handle - but if I need to up the supply (higher voltage + VA bigger transformer) then that's a possibility.

----

One additional q relating to matching the cross-over freq of this setup with my main speakers.

The specs on my main speakers are pretty thin on the ground - it says something like 55-20,000hz. At the moment my LP filters -3db point is 150hz - but I don't know enough about manufacturers specs to know if I should be aiming for 55hz, or slightly higher/lower?

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