Dayton DVC & Rythmik 250SE results

[drboyd]

You know, I've been doing this speaker calc stuff for about two seeks now. I'm a technical person, but all this is like brand freakin' new to me.

I'm taking away that I should probably leave both voice coils connected in my vented box... right? My amp runs a little warmer than I'd really prefer, but then again I'm playing it louder than my poor wife would really prefer, too....

[loudnclear]

Okay DrBoyd, I ran some numbers on your 41L (1.45cuft) vented design using BassBox software. A Dumax report was used for the T/S parameters on the Dayton 12" DVC subwoofer.

Your current 41L vented design:

Vb=1.45cuft
Fb=24hz
F3=28.9hz
Dv=3"
Lv=18.5"
Fill=normal

The curve on this design looks smooth with steep roll-off below F3. Nice curve.

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Your design using 1 voice coil (second coil left open):

Vb=1.45cuft
Fb=24Hz
F3=28.9Hz
Dv=3"
Lv=18.5"
Fill=normal

Looks good right? Wrong!!!

Your design using just 1 voice coil looks much the same numbers wise, but has a very ragged, undesirable frequency response curve that has a huge peak above F3 and a big dip below it. Can you say "boomy"? No matter what vented design I used with your 41L box, I could not improve over your design using 1 voice coil and resistively damped operation. This response curve is so ugly, it could be a modern art masterpiece.

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A 41L Sealed Box targeting Qtc=.707 by resistively damped operation:

Vb=1.45cuft
Fb=36.4Hz
F3=36.4Hz
Qtc=.707
Fill=Heavy

(Target Qes for resitively damped operation: Qes=.517)*
(Target Qts for resistively damped operation: Qts=.48)*
*Both of these number go together, try plugging one or both into a bassbox program

Value of the damping resistor across the second coil: Unknown (but I could calculate it if you really want it).

This curve is quite smooth with shallow roll-off below F3. Nice curve. With room gain, I'll bet this would be quite flat down deep. HOWEVER, this curve is about 6dB less sensitive than your current vented design. Looks quite good for musical accuracy, but may or may not meet your needs for HT. BTW, this design should be an easy load on your amp for less heat.

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Conclusion: for your 41L box, the vented design looks pretty good. If you discover your needs lean towards a sealed design, then resistively damped operation will be your Huckleberry.

Best regards,

Andy

[drboyd]

Andy, thanks for looking at it! This is my first subwoofer, and I've gotta tell you - I'm just tickled pink with it. My intention was just to piece somthing inexpensive together for about a year, at whch time my situation will change to where I'm planning to get an SVS.

But I'm very impressed with how this one turned out. Between the advice on this forum and the PE forum, quite a bit of dumb luck, and the help of WinISD, I've got something that's making me drag out my old disks and actually hear the bass track for the first time! I was anticipating that the ported design would be boomy, but I don't hear that in it at all. I'd call it solid and flat.

My main amp is a re-capped Magnavox tube type with (4) 6V6's in PP, and it does an excellent job on the vocals and high end. Main speakers are JBL L-100's. Although the JBL's are supposed to reach 27 Hz, this sub really adds the bass dimension.

Lessons learned:
A $19.95 roto-zip from Harbor Freight makes a great trim router for expanding the speaker mounting base.
An RV store will sell you some great putty tape for speaker and amp mounting.
3" abs drain pipe makes a great port.
Left-over generic tar-rubber auto sound dampening sheets do pretty well on sub-woofer panels.


Don

[loudnclear]

Drboyd, here's some more number for you.

Both Dayton DVC voice coils in parallel, sealed enclosure, Q=.707:

Vc=.811cuft
Fc=46.4Hz
F3=46.4Hz
Qtc=.707
Fill=normal

This sub will not go very low, even with room gain.
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Both voice coils in parallel, 41L (1.45cuft) sealed enclosure:

Vc=41L (1.45cuft)
Fc=37.5Hz
F3=47.3Hz
Qtc=.580
Fill=normal

This sub will not go low and will sound a little anemic with Q=.58

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My design, 50L (1.77cuft), sealed, resistively damped oper*:

Vc=1.77cuft
Fc=34.1Hz
F3=34.2Hz
Qtc=.707
Fill=heavy

*1 voice coil with a 7.5ohm resistor across terminals, 1 voice coil to the amp

This is a good sealed design with good performance. Slow roll off gives good room gain numbers.

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Conclusion:

1)The Dayton 12" DVC subwoofer likes to be in ported enclosure when both voice coils are parallelled, and conversely does not particularly like the sealed enclosure.

2) With one voice coil hooked up, the driver is begging to be in a sealed enclosure and can be precisely tuned to the box using resistively damped operation. (1 voice coil with NO RESISTOR looks good in an infinite baffle design). 1 voice coil operation does not like the ported enclosure giving a poor response curve.

3) The Dayton DVC 12" subwoofer is a versitile driver.

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Best regards,

Andy

[loudnclear]

Here's some numbers with only 1 voice coil wired up with no damping resistor. Looks pretty good for an infinite baffle design. (I'll bet Dayton's 15" IB woofer is basically a 15" DVC with only 1 voice coil.) These numbers are for the 12" DVC, 1 coil wired:

Vc=9.68cuft
Fc=24.3Hz
F3=24.3Hz
Qtc=.707
Fill=normal

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Vc=infinite
Fc=21.3Hz
F3=24.1
Qtc=.633
Fill=minimal

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This is a nice, versatile woofer. Anybody out there use the Dayton DVC woofer in an infinite baffle application?

Warm regards,

Andy