Quick and dumb wiring question for a DVC Subwoofer (maybe more of a “What is your opinion” question)

**KDspiv** · **09-18-09, 03:58 PM**

My favorite sub that is going back for a warranty situation. So in the meantime I have cobbled together a sub to use in the interim. This woofer is NOT well suited to the enclosure I am going to use it in but it is already on hand and only has to last a few weeks.

Here is the needed info:

I ordered an MCM 300 watt a/ 4ohm or 200 watt a/ 8 ohm plate amp to replace the blown amp that put the sub in the garage to begin with.

The DVC subwoofer I have is dual 4ohm coils and needs about 150 watts a coil in my opinion to sound “decent”.
Xmax of 15.8mm
Fs of 30hz
Vas of 1.35 ft
(and here in lies the rub) a Qes of .65 so it doesn’t plot well in the 2.8ft ported box tuned at 27hz but it DOES sound um….ok.

It starts to roll off at exactly as the plots states when modeled (a small peak between 33hz to 44hz and steeeeep roll off after 27hz) when both coils are fed 200 watts.

Soooo…. My question is:

Will it be better to run a single 4 ohm coil at 300 watts or both coils added up to 8 ohm (2 ohm load + Plate amp = roasting marsh-mellows over burning transistors) and only give each coil 100 watts?

I know I double the Qes when running a single coil but I can always short across the other coil to act as an electrical brake and bring the Qes back down a bit. Or even install a potentiometer in place of a short to dial the damping in.

**Mike P.** · **09-18-09, 04:12 PM**

It's not recommended to run only one coil of a DVC sub. Wired in series for a 8 ohm load the amp will handle the sub just fine.

**KDspiv** · **09-18-09, 04:27 PM**

True, it is not recommended due to long term speaker damage, quality of sound suffering due to dampening characteristic and so on.

But manufacturer recommendations aside……but, for the sake of PURE volume, which is better?

My processor has the option of automatically switching between two different subwoofers according to what type of signal (2channel –vs- surround) it receives. I have a REL T3 that is used for music. But my little Sonus Concerto’s need a much bigger subwoofer to pull double duty as home theater speakers.

I guess I will just experiment and see which wiring method gives the best compromise of SPL to quality.

I thought it smart to ask none the less so thanks for your answer!

**Mike P.** · **09-18-09, 04:50 PM**

You would definitely get more SPL with 300 watts into 4 ohms compared to 200 watts into 8 ohms.

**StereoClarity** · **09-19-09, 01:39 AM**

The difference between 300 and 200 watts is less than 3db. I wouldn't risk running a single coil like that for the marginal gain. I'd rather see you run both of them.

**Ricci** · **09-21-09, 01:27 PM**

Run both coils at 8ohms. You will not gain any volume by running one coil at 4ohms. You will be halving BL and changing the overall performance of the vc / motor system.

**StereoClarity** · **09-21-09, 01:31 PM**

Josh is right. I didn't even think about the change in BL.

**Mike P.** · **09-21-09, 02:12 PM**

One 4 ohm coil halves the BL, both coils at 8ohms doubles the BL. There should be a difference in SPL. Unless I'm doing something wrong, here is the Adire Shiva as an example.

Pink is one coil, half the BL, Re 5.8 ohms of one coil,, 300 watts.
Green is both coils wired in series, double the BL, Re 11.6 ohms, 150 watts.

If this is right then my assumptions in post #4 are incorrect.

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**Ricci** · **09-21-09, 04:20 PM**

Right. Using only one coil causes changes to the following parameters...

QTS
QMS
QES
RE
LE
BL

You lose 3db of efficiency right off the bat, you half your power handling, double your Qes, lose BL, and shift the other specs as well. Basically it won't perform like the same driver at all.

**KDspiv** · **09-21-09, 04:57 PM**

Quote:

Mike P. wrote:

One 4 ohm coil halves the BL, both coils at 8ohms doubles the BL. There should be a difference in SPL. Unless I'm doing something wrong, here is the Adire Shiva as an example.

Pink is one coil, half the BL, Re 5.8 ohms of one coil,, 300 watts.
Green is both coils wired in series, double the BL, Re 11.6 ohms, 150 watts.

If this is right then my assumptions in post #4 are incorrect.

Attachment 16010

Ok, I need to figure out how to post my graphs like you folks do. But the quick and dirty are thus:

With both coils at 8 ohms

With single coil at 4 ohms and 2nd set of coils shorted to bring down Qes

I am running it with both coils at 100 watt each, the outcome is much better than I expected or even hoped for from a sub intended for automotive purposes at the parameters these subs usually have.

Using the Anthem's resonance test tones and my ear (not to mention wall picture rattle) to test, I can tell you that the graphs are about as correct as anyone could expect.

My DIY subwoofer has the sub in a downfiring driver and port arrangment so the gain there plus the room gain prop up the lower Hz. This actually makes for a decent sub for home theater use and when coupled with the Anthem's resonance notch filter sound decent on music. Not great but certainly better than expected perfromance.

I am really thinking that I need to build a monter sub though.....you know, just for fun!

On a side note: This MCM plate amp with a torrodial power supply and 2 pairs of Toshiba 2SC5200/2SA1943 output transistors is moog impressive. The Toshiba Transistors have been legendary in their sound quality (these are what made the Onkyo 919THX so great for example) and make for a very musical, medium power sub amp. I replaced op amps with Burr Brown since I have a bunch laying around but this isn't needed.....I just have fun doing this sort of thing.

**Mike P.** · **09-21-09, 06:10 PM**

Glad to hear your sub is working. You can get your post count up in the Post Padding thread and then add your graphs to the post above.

http://www.hometheatershack.com/foru...tml#post191517

**KDspiv** · **09-21-09, 08:11 PM**

I guess I should have modeled it with the proper wattage added to show true spl.

But I have added the graphs now that I have padded my post count.

Not spectacular response but enough low end to watch movies with for right now.

**Mike P.** · **09-21-09, 08:36 PM**

Quote:

Not spectacular response but enough low end to watch movies with for right now.

That's all that matters. Hopefully your warranty situation won't be too long a wait.

**KDspiv** · **09-21-09, 08:51 PM**

Actually it looks like the manufacturer is trying to tell the dealer that warranty is not going to cover the repair.

The sub is only a week old.....ggrrreeeaaaatttt. Looks like I am going to be calling a credit card company and finding out my options. Now I wish I hadn't sold my trusty old Sunfire.

So maybe it is time to brush off the parts bin, silver solder, and screwdrivers to get back into the DIY world.

@ Mike P: Thank you for all of your help especially. I have a strange feeling I may be asking questions for a complete build soon.

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