Dual Voice Coil Wiring... Again

[Jake]

I am sorry to be the 1,000,000th person to ask about DVC's, but after
scouring the entire internet, i need an answer.

Can a 4-ohm DVC sub be wired with an impendence of 4 ohms? It seems
that 2 ohms and 8 ohms are the only options.

I have a Type R and kenwood amp that pushes 500 watts rms at 4 ohms.
Just perfect for the 500 watt rms sub.i dont want to give it ~300 watts
at 8 ohms or 900 watts at 2 ohms.

I didnt do my homework and i already bought the 4 ohm DVC sub when i
should have got the 2 ohm.

How can it be wired at 4 ohms and 500 watts rms?

Since my mono amp has 2 positive and 2 negative terminals for output,
can i just connect each + from the amp to each + on the sub, and do the
same with the negatives to get 4 ohms?

Thanks,
Jake

Sub: Alpine SWR-1242D
Amp: Kenwood KAC-9152D

[Low-Hz]

You can only wire a dvc 4 ohm sub to 2 or 8 ohms.

Sorry.


--
Low-Hz

[hvnd4speed]

maybe this is me being stupid in my thinking and maybe this isnt a
correct way......but why not just use only the one set of terminals,
thus running at 4ohms only....i have wired up a cheapie DVC sub before
just playing around with it and it worked fine as far as sound output


--
hvnd4speed

[Low-Hz]

hvnd4speed;658933 Wrote:
> maybe this is me being stupid in my thinking and maybe this isnt a
> correct way......but why not just use only the one set of terminals,
> thus running at 4ohms only....i have wired up a cheapie DVC sub before
> just playing around with it and it worked fine as far as sound output

Yes, you can wire just 1 VC on a sub. I believe Wiggins actually wrote
a paper on it awhile back, but don't quote me if I am wrong about that.


First off, his sub is rated at around 500rms. And his amp puts out
around 500rms at 4 ohms. So if he wired 1 VC he would give 1 VC 500rms
and that is not what he wants to do. Not to mention most people would
want to wire both VC's.

What I would do, is wire the sub down to 2 ohms and just set your gains
correctly so that the sub is only getting around 500rms. If the amp is
2 ohm stable problem solved.


--
Low-Hz

[Jake]

Alright, thanks for the speedy feedback.

I am pretty sure that i saw warnings left and right NOT to wire only
one VC, so i dont think id wanna do that. I may have to do with taking
the gain down a few notches.

But while you are here, i have another semi-related question.

My mono amp has 2 positive and 2 negative outputs. is it just acting as
a splitter by creating this, or is it actually two seperate channels of
the same exact sound?

Someone at Best Buy said i could achieve 4 ohms by bridging my mono amp
into 8 ohms, and then bring it back down to 2 ohms with the DVC. Are
they hittin the crack pipe, or is there some logic to this?

i dont even know how to bridge my amp...

[D.Kreft]

On Nov 26, 9:13 pm, "Jake" > wrote:

> I am sorry to be the 1,000,000th person to ask about DVC's, but after
> scouring the entire internet, i need an answer.

Not sure where you scoured, but the JL Audio tutorials have been on the
JL Audio website since I wrote them back in 1995 or 1996:

http://mobile.jlaudio.com/support_pages.php?page_id=141

There are two tutorials there of interest to you: "Wiring Your
Subwoofers" and "Dual Voice Coils". Please read them carefully.

> Can a 4-ohm DVC sub be wired with an impendence of 4 ohms? It seems
> that 2 ohms and 8 ohms are the only options.

They are the only two options. Wiring just one VC is *NOT* a good idea.
The tutorials should cover it, if memory serves.

> How can it be wired at 4 ohms and 500 watts rms?

It cannot.

> Since my mono amp has 2 positive and 2 negative terminals for output,
> can i just connect each + from the amp to each + on the sub, and do the
> same with the negatives to get 4 ohms?

No, absolutely not...unless your amp's paperwork (manual) says you can,
and I find that highly unlikely.

Just use the subs as 8 Ohm a piece...the result will be less power than
what you expect, but you'll have the benefit of a cooler-running
amplier and increased damping factor, which means that the amp will
have better control over the subs. And remember, doubling the power
only results in a 3dB gain in SPL...it's not a huge difference. So
don't try to do anything silly (or even stupid).

-dan

[D.Kreft]

On Nov 26, 11:19 pm, "Jake" > wrote:

> I am pretty sure that i saw warnings left and right NOT to wire only
> one VC, so i dont think id wanna do that. I may have to do with taking
> the gain down a few notches.
>
> But while you are here, i have another semi-related question.
>
> My mono amp has 2 positive and 2 negative outputs. is it just acting as
> a splitter by creating this, or is it actually two seperate channels of
> the same exact sound?

I'm not familiar with your amp at all, but when you say "mono amp" that
says to me that your amp has *one* channel ("mono" == "one"), so I'm
not sure what kind of beast you're describing with two channels. It
sounds like perhaps you're using a two-channel amplifier in a "bridged"
configuration (e.g. by using a "+" from each channel or a "+" from one
channel and a "-" from the other).
A somewhat technical explanation of what's going on here can be found
on wikipedia:

http://en.wikipedia.org/wiki/Bridged_amplifier

In essence, you combine the two channels such that the the voltage
swing across the two terminals is double that of a single channel--a
feat which can be accomplished, by the way, ONLY on amplifiers designed
for this mode of operation. These days, almost all car audio amps are
bridgeable, but I say this to be thorough.

> Someone at Best Buy said i could achieve 4 ohms by bridging my mono amp
> into 8 ohms, and then bring it back down to 2 ohms with the DVC. Are
> they hittin the crack pipe, or is there some logic to this?

*toke* *toke* *toke* "The colors, man....the COLORS!" Either your
recollection of what "someone at Best Buy" (was this a customer???)
said, or the individual you spoke with is seriously confused. It sounds
like someone's been reading too much Car Audio & Electronics without
having actually worked on an electrical circuit of any sort.

When you bridge an amplifier, each half of the bridged pair "sees"
exactly half of the load. So, if you present a nominal 4 Ohm load to a
bridged amplifier, each channel "sees" 2 Ohms--this is why you always
see amplifier power specs say something like "100W x 2 @ 2 Ohms; 200W x
1 @ 4 Ohms". A bridgeable amp that is "two Ohm (stereo) stable" can, at
most, be 4 Ohm mono stable. Make sense?

So, if you have a single subwoofer to run with a single amplifier, you
have three options:

1. Run the amp in "stereo" (unbridged) mode with a mono
(non-stereo) input. This
will present a 4 Ohm load to each side of the amp;

2. Wire the voice coils in series to produce an 8 Ohm load and
bridge the amp, hooking
it up to the subwoofer as directed by your amplifier's manual.
This presents an 8 Ohm
mono load to the amp, which is identical to option #1, above;
or

3. Wire the voice coils in parallel to produce a 2 Ohm load, thus
presenting a 1 Ohm load
to each channel, which will almost assuredly void your warranty
and lead to seriously
shortened life expectancy of your amp's power supply and output
transistors.

4. Exchange your sub for the one you need.

The lesson to take away from this is DO NOT GET GREEDY. If you try to
get more out of your amp than what it was designed to produce, you
*will* pay for it...and it won't be cheap.

-dan

[Atomic Fusion]

Just for informational purposes, you can run a subwoofer fine on one
coil, so long as you know the results.

* You will suffer a 20-30% reduction in power handling (not 50%).
* Qes will double
* Sensitivity will drop by 3db

You can rectify the doubling of Qes by simply shorting the unused coil.
The closed loop of the coil create EMF when it moves through the flux
field of the motor, creating a restoring force, and thus returning Qes
to its normal state.

You can 'dial in' a new value of Qes for the subwoofer of any value
higher than Qes, and not higher than 2*Qes. Rather than shorting the
unused coil, if you place a resistor across the coil, it will offer
different degrees of restoring force, and thus different values of Qes.

If you put an Lpad (potentiometer) across the unused coil, you can
actually dial in different values on the fly, allowing you change the
box Q of a sealed enclosure (thus altering sound quality verses low
frequency extension verses output, and so forth) by simply turning a
dial.

Adam


--
Atomic Fusion

[Brandon Buckner]

Jake wrote:
> Alright, thanks for the speedy feedback.
>
> I am pretty sure that i saw warnings left and right NOT to wire only
> one VC, so i dont think id wanna do that. I may have to do with taking
> the gain down a few notches.
>
> But while you are here, i have another semi-related question.
>
> My mono amp has 2 positive and 2 negative outputs. is it just acting as
> a splitter by creating this, or is it actually two seperate channels of
> the same exact sound?
>
> Someone at Best Buy said i could achieve 4 ohms by bridging my mono amp
> into 8 ohms, and then bring it back down to 2 ohms with the DVC. Are
> they hittin the crack pipe, or is there some logic to this?
>
> i dont even know how to bridge my amp...
>

Sounds like the BB person is confused or ignorant or both. If you do
indeed have a mono amplifier, it cannot be bridged. The two sets of
speaker connectors are purely for wiring ease and aesthetics. If you
connect one VC to one output, and the other to the second, it will be
the same as wiring both to one output. I.E. parallel wiring. All my mono
Class D sub amps since 1999 have been this way.

Brandonb

[GregS]

In article >, Brandon Buckner > wrote:
>Jake wrote:
>> Alright, thanks for the speedy feedback.
>>
>> I am pretty sure that i saw warnings left and right NOT to wire only
>> one VC, so i dont think id wanna do that. I may have to do with taking
>> the gain down a few notches.
>>
>> But while you are here, i have another semi-related question.
>>
>> My mono amp has 2 positive and 2 negative outputs. is it just acting as
>> a splitter by creating this, or is it actually two seperate channels of
>> the same exact sound?

You would have to look it up. Some amplifiers can be paralled. Its not common.

greg

>> Someone at Best Buy said i could achieve 4 ohms by bridging my mono amp
>> into 8 ohms, and then bring it back down to 2 ohms with the DVC. Are
>> they hittin the crack pipe, or is there some logic to this?
>>
>> i dont even know how to bridge my amp...
>>
>
>Sounds like the BB person is confused or ignorant or both. If you do
>indeed have a mono amplifier, it cannot be bridged. The two sets of
>speaker connectors are purely for wiring ease and aesthetics. If you
>connect one VC to one output, and the other to the second, it will be
>the same as wiring both to one output. I.E. parallel wiring. All my mono
>Class D sub amps since 1999 have been this way.
>
>Brandonb

[Jake]

Well at best buy yes, it was an employee. Probably just a christmas
rush one hired for the holidays. i do explicitly remember saying after
he told me "wow i did not know a mono amp could be bridged", and he
said yes it could.

And I did read the JL tutorial oh DVC's. It wasvery informative and it
did indeed tell me everything i CAN do, i just needed to be sure that
what i wanted to do was impossible, which it sounds like it is. well
except of course for the potentiometer method, but i dont tihnk i want
to get into that. so thanks for that info everyone.


This is my amp:
http://www.kenwoodusa.com/products/ListProduct.aspx?k1=2&k2=42&k3=155&pr=2012

and thank you brandonb, for explaining the purpose of the dual speaker
connectors. if both sets of speaker connectors were used, then it would
knock it down to 2 ohms right? NOT keep it at 4 for ohms each pos/neg
wire set. becasue its acting as a splitter... and thats what splitting
a speaker wire does...

i hope i am getting some of this right.

i will most likely run the sub at 2 ohms, and if i choose to buy
another, i will run them at one ohm combined.

while on the one ohm topic, is there any advantage to it, in general?
since amps seem to output the same RMS wattage as at 2 ohms with one
ohm? i know that there is a slightly higher thd% and it can cause
overheating in amps not designed for it...

[Brandon Buckner]

Jake wrote:
> Well at best buy yes, it was an employee. Probably just a christmas
> rush one hired for the holidays. i do explicitly remember saying after
> he told me "wow i did not know a mono amp could be bridged", and he
> said yes it could.

To give him the benefit of the doubt, he was probably just confused that
paralleling and bridging are NOT the same thing.

> And I did read the JL tutorial oh DVC's. It wasvery informative and it
> did indeed tell me everything i CAN do, i just needed to be sure that
> what i wanted to do was impossible, which it sounds like it is. well
> except of course for the potentiometer method, but i dont tihnk i want
> to get into that. so thanks for that info everyone.
>
> This is my amp:
> http://www.kenwoodusa.com/products/ListProduct.aspx?k1=2&k2=42&k3=155&pr=2012

Now that we know the specific amp you're using, just forget about trying
to get a 4-ohm load off the 1 DVC sub. Your amp can handle both with ease.

> and thank you brandonb, for explaining the purpose of the dual speaker
> connectors. if both sets of speaker connectors were used, then it would
> knock it down to 2 ohms right? NOT keep it at 4 for ohms each pos/neg
> wire set. becasue its acting as a splitter... and thats what splitting
> a speaker wire does...

I double-checked the manual for that exact amp before replying. You are
correct, impedance to your 4-Ohm DVC sub would be a 2-ohm final load as
it would be the same as paralleling it. Also, having looked at the
manual, your amplifier is 1-ohm stable, so you really have no problem
connecting your sub in parallel anyway. Just put it to 2-ohm and have at
it. You could even put two of those same subs in all parallel and have
the amp still be happy at 1-ohm.

> i hope i am getting some of this right.
>
> i will most likely run the sub at 2 ohms, and if i choose to buy
> another, i will run them at one ohm combined.

This is fine as the amp is stable at 1-ohm.

> while on the one ohm topic, is there any advantage to it, in general?
> since amps seem to output the same RMS wattage as at 2 ohms with one
> ohm? i know that there is a slightly higher thd% and it can cause
> overheating in amps not designed for it...

I'm definitely not the person to give you the proper technical answer to
this. Suffice it to say, not all monoblocks are rated as such. The
majority that I've seen will usually say approximately double at 1 than
at 2. My amp of choice for the past few years is the Directed 1100d.
That Kenwood operates very similarly in that they both have the dual
connectors for wiring ease, and also are externally bridgeable to an
identical amp. It is also known as "strappable" Kenwood's term for this
is "Dual Mono Drive". If you don't have two of these amps, you can just
skip over that part. The extra speaker connectors come into play in a
funky way while using that configuration as well.


Brandonb

[Jake]

Brandon Buckner wrote:
>Jake Wrote:
> > while on the one ohm topic, is there any advantage to it, in general?
> > since amps seem to output the same RMS wattage as at 2 ohms with one
> > ohm? i know that there is a slightly higher thd% and it can cause
> > overheating in amps not designed for it...
>
> I'm definitely not the person to give you the proper technical answer to
> this. Suffice it to say, not all monoblocks are rated as such. The
> majority that I've seen will usually say approximately double at 1 than
> at 2. My amp of choice for the past few years is the Directed 1100d.
> That Kenwood operates very similarly in that they both have the dual
> connectors for wiring ease, and also are externally bridgeable to an
> identical amp. It is also known as "strappable" Kenwood's term for this
> is "Dual Mono Drive". If you don't have two of these amps, you can just
> skip over that part. The extra speaker connectors come into play in a
> funky way while using that configuration as well.

Alrighty... thanks again.

I guess i am curious as to why the kenwood amp has the same RMS at 1O.
Maybe the manufacturer just keeps it there to prevent the THD from
going over 1%. If they can even rate their own amps output...

reminder: i have an alpine type-r, 500 watts RMS.

So would i be better with keeping what i got and going 900 RMS at 2O
with one sub, and then 450 RMS each with two subs at 1O if and when i
get another one...

OR

should i try to get some money back for the 4O DVC and get the 2O DVC
model. Then i would have 500 RMS at 4O with one sub, and again, 450
RMS each at 2O with 2 subs, and a little less THD.

would i even be able to tell the differece?
i as never worried abotu hurting my amp as i knew it was 1O stable, i
just wanted SQ.

thanks man, you're helping me out a lot here.

[Brandon Buckner]

Jake wrote:
> Alrighty... thanks again.
>
> I guess i am curious as to why the kenwood amp has the same RMS at 1O.
> Maybe the manufacturer just keeps it there to prevent the THD from
> going over 1%. If they can even rate their own amps output...

IIRC its usually up to the manufacturer/marketing company to rate them
and while there is technically an ISO standard (someone else can help
with the number) there is nothing forcing anyone to use it or to comply
with it. What happens is that many find numbers to suit their marketing
agenda. The more reputable brands are usually pretty similar to each
other however. I believe there's a rant by JD out there somewhere for
this newsgroup explaining the whole thing from a couple years ago.
Otherwise, I'm horrible with the math to properly explain what's going on.

> reminder: i have an alpine type-r, 500 watts RMS.
>
> So would i be better with keeping what i got and going 900 RMS at 2O
> with one sub, and then 450 RMS each with two subs at 1O if and when i
> get another one...
>
> OR
>
> should i try to get some money back for the 4O DVC and get the 2O DVC
> model. Then i would have 500 RMS at 4O with one sub, and again, 450
> RMS each at 2O with 2 subs, and a little less THD.
>
> would i even be able to tell the differece?
> i as never worried abotu hurting my amp as i knew it was 1O stable, i
> just wanted SQ.
>
> thanks man, you're helping me out a lot here.
>

Just keep what you've got. You can always turn it down or up to suit
your needs. Having a bit of overhead is a good thing. It reduces the
possibility of clipping which may or may not cause the sub to exceed
mechanical/thermal limitations, possibly damaging or shortening its life.

Just use the basic gain setting procedure and you should be good. Here's
a good one to follow:

http://www.installer.com/tech/gains.html


Brandonb

[KU40]

the engineers that design the amp actually decide if it's going to put
out similar power at different impedence levels. There are pros and
cons of doing it, but the biggest reason for doing it is to appeal to
more buyers. If a guy has a sub that's a 4 ohm DVC and wants a mono
amp, he can only choose from those that put out max power at 2 ohms.
if a guy has a 2 ohm DVC, he can only choose from amps that put out max
power at 1 or 4 ohms. by covering both bases, you can potentially get
both buyers.

The ratings are then done by another team, who can basically say
whatever they want. They can do it strictly by a guideline, maybe at
the exact point that the amp reached 1% THD and rate it for that. Or
they can rate them at different input voltages, or even basically just
make up their own number somewhere around what it tested at within some
parameters they want (like.....16 volts at 5% THD or something). I've
seen secondary tests show an amp underrated by about 75%, and others
overrated by 75%.


--
KU40