I noticed something in your post.........are you really driving a single
dual voice coil sub with two separate channels of an amp? That's a big
no-no....even if the signal fed to the amp is dual-mono. That would
definately hurt your transient response. If that is the case, feel
fortunate that the sub hasn't torn itself to pieces. I had a 12W3 in a
1.3 cu. box in my Celica, and it was one of the tightest sounding
enclosures I've ever used. Very musical, tight and deep. I hope that
you mean that two of the channels are bridged into one....that would be
OK. A larger sealed box would probably make a world of difference if
you are using a smaller sealed or ported box.


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I'm in the market for a new sub, and hopefully someone here can help
me out. Currently, I have a Sony 910 head unit, Stinger
interconnects, a Phoenix Ti 500.4 amp, Kimber Kable 4PR wire, CDT
components (I forget the model), and a JL 10W3 woofer.

What I want is a woofer that is musical. My JL isn't being worked
hard, so SPL is a non-issue. LF extension would be nice, but fast
transient response is more important. I drive a 2002 Civic Si
hatchback, so the cabin gain should help the extension. It will be
driven off two channels of my current amp, which provides 280w RMS
into 4ohms, so I will need something sort of efficient. Finally, I'd
like to keep the cost somewhat reasonable... so no Focal Utopia for
me.

Here are some speakers I've been considering, to give an idea what
direction I was thinking of heading:

- Dynaudio MW180 or MW190. I have some worries about how much box
volume the 190 will need.

- Focal 27V2 or 27KX. Again, the 27KX may take a larger box than I
want to use, and I'm unsure how the LF extension will be on the KX.

- Hsu ASW 1203. Hey, it's cheap! Anyone ever heard one of these?

- Peerless XLS 10" or 12". Also cheap. Peerless has gone with a low
Q design... will this work in my hatch?

I'm in the market for a new sub, and hopefully someone here can help
me out. Currently, I have a Sony 910 head unit, Stinger
interconnects, a Phoenix Ti 500.4 amp, Kimber Kable 4PR wire, CDT
components (I forget the model), and a JL 10W3 woofer.

What I want is a woofer that is musical. My JL isn't being worked
hard, so SPL is a non-issue. LF extension would be nice, but fast
transient response is more important. I drive a 2002 Civic Si
hatchback, so the cabin gain should help the extension. It will be
driven off two channels of my current amp, which provides 280w RMS
into 4ohms, so I will need something sort of efficient. Finally, I'd
like to keep the cost somewhat reasonable... so no Focal Utopia for
me.

Here are some speakers I've been considering, to give an idea what
direction I was thinking of heading:

- Dynaudio MW180 or MW190. I have some worries about how much box
volume the 190 will need.

- Focal 27V2 or 27KX. Again, the 27KX may take a larger box than I
want to use, and I'm unsure how the LF extension will be on the KX.

- Hsu ASW 1203. Hey, it's cheap! Anyone ever heard one of these?

- Peerless XLS 10" or 12". Also cheap. Peerless has gone with a low
Q design... will this work in my hatch?

Before I can take a stab at an answer, what is wrong with your current setup
and what, if anything, have you tried to correct it?

I'm not saying you're completely wrong.......but I have done tests on my
own equipment personally, and I found that the degradation of transient
response was very noticable when each coil was driven independently,
even when the amp recieved a dual mono signal. It's just not a good
idea, and JL will tell you (as will any manufacturer) that it will void
your warranty.


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I noticed something in your post.........are you really driving a single
dual voice coil sub with two separate channels of an amp? That's a big
no-no....even if the signal fed to the amp is dual-mono. That would
definately hurt your transient response. If that is the case, feel
fortunate that the sub hasn't torn itself to pieces.

It's not harmful to drive a subwoofer with two independent channels of
amplification. The sub can't "tear itself to pieces". Most people envision
the two coils pulling against each other when different signals are applied.
But, in fact, the coils are each experiencing the same magnetic force.
Driving two coils with different signals simply causes the magnetic fields
set up by each coil to oppose one another, not the mechanical forces. And
if he's driving each amplifier channel with the same input signal, the
difference will be negligible. If the two channels are getting different
signals it's ok too, because the fields will be summing in much the same
fashion the circuit that converts L and R to mono behaves!

"MZ" wrote in message ...
Before I can take a stab at an answer, what is wrong with your current setup
and what, if anything, have you tried to correct it?

There's nothing terribly wrong with it, I was just looking to upgrade
a bit. The JL woofer doesn't do a bad job, but it can get a bit muddy
at times. Frequency response sounds pretty smooth down to maybe 30Hz.
The woofer is in a sealed box with a net volume of about .63ft^3.
Qtc is in the .85 range, with an F3 of about 45Hz.

I made the switch a while back from an old Kicker ZX460 amp to my PG
and switched to Kimber Kable, both of which seem to help a little bit.
I have toyed around with the levels and crossover points, and moved
the speaker around a bit. Part of the problem is my midrange drivers,
which are responsible for a lot of the kick drum's kick. They could
use a bit more impact; they're next on the list of upgrades, but
that's another thread.

If I had to guess, the other part of my problem was upgrading to
Scan-Speak drivers at home. My ears may have become a bit spoiled.

Oh, regarding the setup: I have the coils wired in series, for a 4ohm
load. Two channels of my four-channel amp are bridged to provide the
power. My amp is good for about 75-80w per channel, or 280w for two
channels bridged into 4ohms. Does that make sense?

There's nothing terribly wrong with it, I was just looking to upgrade
a bit. The JL woofer doesn't do a bad job, but it can get a bit muddy
at times. Frequency response sounds pretty smooth down to maybe 30Hz.
The woofer is in a sealed box with a net volume of about .63ft^3.
Qtc is in the .85 range, with an F3 of about 45Hz.

I made the switch a while back from an old Kicker ZX460 amp to my PG
and switched to Kimber Kable, both of which seem to help a little bit.
I have toyed around with the levels and crossover points, and moved
the speaker around a bit. Part of the problem is my midrange drivers,
which are responsible for a lot of the kick drum's kick. They could
use a bit more impact; they're next on the list of upgrades, but
that's another thread.

If I had to guess, the other part of my problem was upgrading to
Scan-Speak drivers at home. My ears may have become a bit spoiled.

Oh, regarding the setup: I have the coils wired in series, for a 4ohm
load. Two channels of my four-channel amp are bridged to provide the
power. My amp is good for about 75-80w per channel, or 280w for two
channels bridged into 4ohms. Does that make sense?

To be perfectly honest, the difference between subwoofers themselves is
probably much less than you may think it is. When people change subwoofers,
the difference they usually hear is a driver that's operating differently in
the same box rather than an inherent difference between the subwoofers. It
looks like you've tried most of the first things to try. The biggest
differences tend to come from the following adjustments:

- changing the box location in the trunk (sometimes turning it to face a
different direction - not because the aiming is different but because the
position of the driver changes)
- changing the crossover point
- changing the box volume size
- changing the phase of the subwoofer (just switch the speaker leads)

Your problem may also be that you don't have enough power for your sub.

But I think the main problem could be that your midbass up front is lacking,
which a lot of people attribute to a lack of "tightness" or "punch" in the
subwoofer, when in fact it's the midbass drivers not pulling their weight.

So my suggestion to you is not to change the subwoofer, but rather to fix
your midbass issue and, if necessary, increase the power output to the
subwoofer.

"MZ" wrote in message ...
To be perfectly honest, the difference between subwoofers themselves is
probably much less than you may think it is. When people change subwoofers,
the difference they usually hear is a driver that's operating differently in
the same box rather than an inherent difference between the subwoofers. It
looks like you've tried most of the first things to try. The biggest
differences tend to come from the following adjustments:

- changing the box location in the trunk (sometimes turning it to face a
different direction - not because the aiming is different but because the
position of the driver changes)
- changing the crossover point
- changing the box volume size
- changing the phase of the subwoofer (just switch the speaker leads)

Your problem may also be that you don't have enough power for your sub.

But I think the main problem could be that your midbass up front is lacking,
which a lot of people attribute to a lack of "tightness" or "punch" in the
subwoofer, when in fact it's the midbass drivers not pulling their weight.

So my suggestion to you is not to change the subwoofer, but rather to fix
your midbass issue and, if necessary, increase the power output to the
subwoofer.

Normally, I would agree with you about replacing the components first,
but I really want a cleaner looking setup in the hatch, and want to do
it right while I'm in there. Once that's done, I will address my
midbass/midrange issues with some new speakers and more treatment to
the door (Deflex panels, more Dynamat, and maybe using something like
plexiglass to seal the door up better).

I have adjusted the crossover point and switched the phase. I
untethered the woofer box and moved it around, with no real
improvements. As for the box volume... that I haven't changed.

If possible, I would like to avoid buying another amp. A more
efficient woofer would appeal more to me, if possible.

What kind of wattage are you running to it? Is the box ported or
sealed? Aprox. volume? If you really want to get rid of the JL, I may
take it off your hands.....


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I didn't flame you bro, don't flame me. First off, I NEVER said that
giving a dual mono signal increased transient response. The amp does
that for you if you bridge the two channels.

I've been in SQ for a while, winning a few rookie trophies off my first
all-by-myself install. My tests were done the best way- by ear. I
took a tried and true old-school bass demo disc I love, Techmaster
PEB's Bass Computer, the song is called Bassgasm (the ultimate woofer
test). If you are familiar with it, you'd know how demanding the track
is. My sub did not perform as well in the lower extremes with the
coils wired separately. This is just my experience, if you want to
claim otherwise, feel free.....I was just trying to help.

To the author, your amp sound fine, in my opinion you'd be better off
with a sealed box around .8cu foot to 1.0 cu foot. I hope this helps
you out.


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It's cool man.....the disc itself is actually a very early techno album.
The bass tracks on it have been known to blow out subs who's amps
aren't set correctly for headroom. It's worth picking up just for demo
value. I'm a bit of a perfectionist, I've been told I have too much of
a golden ear, I'm too picky. I'm not saying that it was a huge
difference, and to be honest, it may have very well been that my amp
wasn't performing as well at that impedence.......my buddy (who isn't
into competition audio) said he didn't hear a difference. So, in all
fairness, it may have been in my head. I just like to play on the safe
side when possible.


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I'm not saying you're completely wrong.......

Good. Because I'm not wrong at all.

but I have done tests on my
own equipment personally, and I found that the degradation of transient
response was very noticable when each coil was driven independently,
even when the amp recieved a dual mono signal.

First of all, what kind of tests were these? Please describe them. You
don't even say whether they're psychophysical or electrical tests.

It's just not a good
idea, and JL will tell you (as will any manufacturer) that it will void
your warranty.

JL's tech support is chock full of errors. This has been well documented by
myself and others. One of their errors is the notion that transient
response is affected by driving the coils separately. The Qts (and Qes) of
the driver change, but nothing else. This is documented on the Adire Audio
website. In fact, they actually recommend doing this and they provide
instructions on how to do it best! www.adireaudio.com

So you claim that when the amp receives a dual mono signal, the transient
response increases too. Care to explain how this works?

I didn't flame you bro, don't flame me.

Didn't flame you. Sorry if I came off that way.

First off, I NEVER said that
giving a dual mono signal increased transient response. The amp does
that for you if you bridge the two channels.

I'm not sure what you mean by this exactly. You said "I found that the
degradation of transient response was very noticable when each coil was
driven independently, even when the amp recieved a dual mono signal."
That's what I responded to. In particular, I alluded to being in
disagreement with the notion that the transient response is degraded when
driven by independent amplifier channels.

I've been in SQ for a while, winning a few rookie trophies off my first
all-by-myself install. My tests were done the best way- by ear. I
took a tried and true old-school bass demo disc I love, Techmaster
PEB's Bass Computer, the song is called Bassgasm (the ultimate woofer
test). If you are familiar with it, you'd know how demanding the track
is. My sub did not perform as well in the lower extremes with the
coils wired separately. This is just my experience, if you want to
claim otherwise, feel free.....I was just trying to help.

I don't doubt your experience with that disc and that subwoofer. In short,
my point is that:
1) you won't damage a subwoofer by driving it with independent amplifier
channels - this is explained on Adire Audio's website;
2) Summing two different signals in the "magnetic field domain" isn't much
different from summing them in the "electrical domain" (ie. the preamp)
which is done to create a mono signal from two stereo signals. The only
difference is that you decrease output power of the amplifier by doing so.
The amount is proportional to how different the two signals are - which,
quite frankly, isn't very much under 100 Hz.

What you heard in your test was not a transient response issue. I presume
it was just a matter of loss of power or something, assuming you were using
a suitable LP crossover. But I'm not familiar with that test disc, so I
don't know if they do something artificially funky below 100Hz. That's why
I generally don't use test discs - they don't simulate real world conditions
well.

When you have more air volume in an enclosure, you have more air to
control it. The air acts as a spring, the more air is in an enclosure,
the more it controls the mass of the cone and drive assembly. That's
why you hear some manufacturers say if you like rock and rap to use a
smaller box, use a larger box if you like jazz. I think that that's a
poor way to put it, because I don't particularly love jazz, but I like
my bass to be crisp and tight. The other advantage you gain by more
volume is the sub will play louder at lower notes to some extent.
However, if you go to large, you lose power handling for the extended
low frequency range. I kept my 12w3 in a 1.4 cubic box and it played
low notes very well for a 12", and had excellent transient response.
You may also try to lower your crossover point, or use a steeper slope
when you uprgrade your midbass/midrange drivers. One thing you could
try if you don't want to get another box is to stuff the box with
polyfill or r-12 tpe insulation. It slows down the basswaves and will
fool the sub into thinking the box is a little larger. Dynamat is
something I have a very deep apreciation for....it really can make a
huge difference when all you hear is the speaker and not the
reverberations throught the chassis of the vehicle. I hope you get
that JL where you like it, they are some good subs....maybe not the
best, but definately a top-end contender.


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bassengine303 wrote in message news:1097555513.0Xw9tU4dCNhipV/Do94t1A@teranews...
What kind of wattage are you running to it? Is the box ported or
sealed? Aprox. volume? If you really want to get rid of the JL, I may
take it off your hands.....

About 280w RMS, using two channels of my PG Ti500.4 amp bridged. It's
in a .63ft^3 sealed box.

I'll keep you posted if/when I decide to go with a different woofer.

You recommended a larger box, in the .8-1ft^3 range. Could you
elaborate a little on that... why would a larger box help?

Thanks for the clarification.......one point I'd like to make is that in
a real-world application, you will have more boomy or sloppy bass in a
smaller enclosure (within the driver's volume range), in sealed boxes
at least. I say this for one reason, I built three different
enclosures for the same 12" JL that I owned, and played all three on
the same amp at same volume level with the same test disc. Note that
your crossover point and slope will affect these as well. With good
midbass drivers and a steep slope set relatively low, this is what I
found......The larger volume chamber (1.4 cu. ft) had better transient
response and played deeper, although it didn't have a very noticible
edge in transient response. The 1.0 cu. box had a good-all around
response, but rolled off a little sooner. The smaller box (.70 cu. ft)
displayed definate loss in transient response, and had a much more
boomy sound to it. My expererience is limited to this one sub in this
case, but I've seen and installed many other drivers that keep to that
general principal. Don't take my word for it (no one does anyway) do
your own experiments to find out for your self.....I hope this helps
the author in his original question about muddy bass at low
frequencies.


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bassengine303 wrote

When you have more air volume in an enclosure, you have more air to
control it. The air acts as a spring, the more air is in an enclosure,
the more it controls the mass of the cone and drive assembly.

Actually, you've got this backwards (sort of)
I won't be able to explain this properly but here is the reader's digest
version ...
The larger the enclosure the more efficient the driver (less control over
the movement of the cone) The pressure of a small volume will increase (and
decrease) faster then the pressure of a large volume, hence when the
speaker cone moves in it will encounter greater resistance to the movement
in a smaller enclosure. The lower the frequency that you are trying to
reproduce, the farther the cone has to travel. This means that in a smaller
enclosure you sacrifice low frequency extension (the output drops off) This
achieves a "tighter" bass and less "boom"
In summary ... the more air in an enclosure, the less it controls the mass
of the cone and drive assembly.

That's
why you hear some manufacturers say if you like rock and rap to use a
smaller box, use a larger box if you like jazz. I think that that's a
poor way to put it, because I don't particularly love jazz, but I like
my bass to be crisp and tight. The other advantage you gain by more
volume is the sub will play louder at lower notes to some extent.

This is correct.

However, if you go to large, you lose power handling for the extended
low frequency range.

More correct to say you lose power handling period (doesn't just effect LF)

I kept my 12w3 in a 1.4 cubic box and it played
low notes very well for a 12", and had excellent transient response.
You may also try to lower your crossover point, or use a steeper slope
when you uprgrade your midbass/midrange drivers. One thing you could
try if you don't want to get another box is to stuff the box with
polyfill or r-12 tpe insulation. It slows down the basswaves and will
fool the sub into thinking the box is a little larger.

A common misconception ... the bass waves do not slow down. The polyfill
absorbs heat energy that would otherwise increase the "pressure" inside the
enclosure, this creates the illusion of more air space simply because the
airspace does not diminish.

Dynamat is
something I have a very deep apreciation for....it really can make a
huge difference when all you hear is the speaker and not the
reverberations throught the chassis of the vehicle. I hope you get
that JL where you like it, they are some good subs....maybe not the
best, but definately a top-end contender.

I hope the points I made are helpful and not too confusing.

Dan

Thanks for the clarification.......one point I'd like to make is that in
a real-world application, you will have more boomy or sloppy bass in a
smaller enclosure (within the driver's volume range), in sealed boxes
at least. I say this for one reason, I built three different
enclosures for the same 12" JL that I owned, and played all three on
the same amp at same volume level with the same test disc.

I think there are more people who would claim otherwise, and who have a
larger sample size than 3.

bassengine303 wrote

Thanks for the clarification.......one point I'd like to make is that in
a real-world application, you will have more boomy or sloppy bass in a
smaller enclosure (within the driver's volume range), in sealed boxes
at least. I say this for one reason, I built three different
enclosures for the same 12" JL that I owned, and played all three on
the same amp at same volume level with the same test disc. Note that
your crossover point and slope will affect these as well. With good
midbass drivers and a steep slope set relatively low, this is what I
found......The larger volume chamber (1.4 cu. ft) had better transient
response and played deeper, although it didn't have a very noticible
edge in transient response. The 1.0 cu. box had a good-all around
response, but rolled off a little sooner. The smaller box (.70 cu. ft)
displayed definate loss in transient response, and had a much more
boomy sound to it. My expererience is limited to this one sub in this
case, but I've seen and installed many other drivers that keep to that
general principal. Don't take my word for it (no one does anyway) do
your own experiments to find out for your self.....I hope this helps
the author in his original question about muddy bass at low
frequencies.

I am not going to try and guess why you got those results, but suffice to
say that they are not typical. I suppose the definition of "boomy" might be
to blame here. I consider "boomy" to be relatively high bass content (early
to mid 40hz) I see "thunder" and "rumble" to describe the deep bass below 30
hz (which is what will generally be most deminished by reducing the
enclosure volume).

Dan Snooks

OK, here's what I'm thinking. Someone correct me if I'm off base.

I plan to start building a fiberglass box soon, before I buy the
woofer, to make sure I can get the airspace right and have room for the
woofer to sit. I have some fiberglass experience, so that doesn't
worry me much. This time around, I will go with an epoxy instead of
polyester resin, and will likely make a large front baffle out of 3/4"
MDF.

I'm shooting for a gross internal volume of 1ft^3, and plan to use a
Seas SW300. That will yield a Qtc of around .81 and a lower Fb than I
have now, which should slightly improve my LF extension. It's got a
92dB sensitivity, so I should have adequate power, given that my
current woofer isn't as sensitive and plays loud enough for my tastes.

Does this sound like a reasonable setup? I've never heard Seas, so if
anyone has input I would appreciate it.


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MZ,

you mentioned that on the Adire site, there is a paper on how best to
wire a DVC subwoofer with each voice coil wired independently. I can't
seem to find it. Do you have a url or know what the paper is called on
the site? I found the DVC wiring one that says it is OK to do so
without hurting the sub.

I am planning on running my subwoofer in this fashion and have had a
difficult time finding out any information on wiring this way. I have
already seen the JL Audio faq that is not recommended, but the way my
amp works, I may have to do it this way.

I believe the output will be a summed mono, as the manual states, "The
input signals from channels 1-4 are summed, rolled off above 80/120Hz,
then internally connected to the inputs for both channel 5 and channel
6."

The reason I do this is that my amp cannot bridge channels 5 and 6 and
by running them separately, I can get a 2 ohm output on each channel,
effectively doubling the output.

Have you heard systems set up this way? I can't seem to find any
examples of other people with setups in this fashion.

By the way, I am running a Mcintosh MC440 amp to an Eclipse 12" SW7124
2ohm DVC subwoofer.


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They've redone that website since I was last on it. They had a paper on
there at one point about doing it, and their recommendation was that you
shorted the unused coil to maintain the same Q of the subwoofer. They also
mentioned that you can "dial in" the Q you want by wiring up a potentiometer
to the unused coil.

The whole idea is that there's motional emf induced into the unused coil,
because the laws of physics basically state that a coil moving in a magnetic
field picks up a voltage proportional to the speed of motion. You can
actually see this by hooking a voltmeter up to your speaker and then quickly
pushing down on the cone - it'll register on the meter. Anyway, this
voltage also acts to influence the sub's motion in a feedback manner. This
is why it matters what you do with the unused coil.

If you're talking about hooking up both coils to two different signals, then
these issues don't come into play. But the idea here is quite simple - the
magnetic fields that are set up by the current going through the coils will
sum. Some manufacturers actually claim that this could cause the coils to
"pull against each other", but physics tells us otherwise - it would never
get to that point because the coils are basically intertwined so whatever
magnetic field is set up by one affects the other. In the end, the same
magnetic flux affects both coils. The only way they could pull against each
other would be if they were experiencing opposite magnetic fields - quite
the impossible task. They would have to be separated (not intertwined) and
magnetically shielded from one another for this to be able to happen!

The paper described all this, but I don't have a copy. If it's not on their
website, you could try emailing them.

And yes, it'll be fine to set things up the way you've described.


"SCtud" wrote in message
news:1107826248.4e9b037ebf1072f224cc16741c8a6799@t eranews...

MZ,

you mentioned that on the Adire site, there is a paper on how best to
wire a DVC subwoofer with each voice coil wired independently. I can't
seem to find it. Do you have a url or know what the paper is called on
the site? I found the DVC wiring one that says it is OK to do so
without hurting the sub.

I am planning on running my subwoofer in this fashion and have had a
difficult time finding out any information on wiring this way. I have
already seen the JL Audio faq that is not recommended, but the way my
amp works, I may have to do it this way.

I believe the output will be a summed mono, as the manual states, "The
input signals from channels 1-4 are summed, rolled off above 80/120Hz,
then internally connected to the inputs for both channel 5 and channel
6."

The reason I do this is that my amp cannot bridge channels 5 and 6 and
by running them separately, I can get a 2 ohm output on each channel,
effectively doubling the output.

Have you heard systems set up this way? I can't seem to find any
examples of other people with setups in this fashion.

By the way, I am running a Mcintosh MC440 amp to an Eclipse 12" SW7124
2ohm DVC subwoofer.


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Wow, thanks for the quick reply MZ. I have e-mailed Adire asking for the
white paper. Hopefully they respond quickly as well.

Dark1, In regards to the heat question, Adire addresses it in their
paper at the following link. It is pretty much a non-issue as the
increased heat is negligible.
http://tinyurl.com/55bpv

This is different than the myriads of posts that I have seen saying
that wiring DVC subs independently is a big no-no, with most people
referring people to the JL Audio technical faq located he
http://www.jlaudio.com/tutorials/dvc/diffsignals.html

I am really wondering if there is a noticeable effect that JL Audio
believes may occur, which is to "create undesirable non-linearities
and distortion because different input signals at each voice coil
create shifts in the speakers electrical parameters."

Any comments anybody?


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I wish there was some concrete evidence to support/debunk what JL Audio
says on their site regarding this topic, since most people, including
myself, are prone to believing whatever JL Audio says.

I am definitely looking forward to Adire's response to my e-mail
however and would very much like to hear what their take on the issues
is.


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"MZ" wrote in message
...
They've redone that website since I was last on it. They had a paper on
there at one point about doing it, and their recommendation was that you
shorted the unused coil to maintain the same Q of the subwoofer. They
also
mentioned that you can "dial in" the Q you want by wiring up a
potentiometer
to the unused coil.

The whole idea is that there's motional emf induced into the unused coil,
because the laws of physics basically state that a coil moving in a
magnetic
field picks up a voltage proportional to the speed of motion. You can
actually see this by hooking a voltmeter up to your speaker and then
quickly
pushing down on the cone - it'll register on the meter. Anyway, this
voltage also acts to influence the sub's motion in a feedback manner.
This
is why it matters what you do with the unused coil.

If you're talking about hooking up both coils to two different signals,
then
these issues don't come into play. But the idea here is quite simple -
the
magnetic fields that are set up by the current going through the coils
will
sum. Some manufacturers actually claim that this could cause the coils to
"pull against each other", but physics tells us otherwise - it would never
get to that point because the coils are basically intertwined so whatever
magnetic field is set up by one affects the other.

That's very interesting. Forgive me if I sound retarded as I am no EE. I
understand why the coils wouldn't pull on each other, but wouldn't you still
not want to ever do this because voltage on one coil would sometimes cancel
out voltage on the other coil? As I recall, speakers receive alternating
current (producing the in/out motion of the cone). If you send two
different signals to each coil one signal may be on the "in" phase and the
other may be on the "out" phase, effectively cancelling out the voltage.
Admittedly, if we are taling about the left and right channels, the
cancelation effect would likely be small, but there nonethless. Is this not
so?

MOSFET

That's very interesting. Forgive me if I sound retarded as I am no EE. I
understand why the coils wouldn't pull on each other, but wouldn't you
still
not want to ever do this because voltage on one coil would sometimes
cancel
out voltage on the other coil? As I recall, speakers receive alternating
current (producing the in/out motion of the cone). If you send two
different signals to each coil one signal may be on the "in" phase and the
other may be on the "out" phase, effectively cancelling out the voltage.
Admittedly, if we are taling about the left and right channels, the
cancelation effect would likely be small, but there nonethless. Is this
not
so?

Yes, you're right. If you drive the speaker with two out of phase signals,
the fields set up by the coils will cancel each other out. But that's sort
of the point. You're creating a mono signal out of a stereo signal by doing
this. And, in the subwoofer range of frequencies (ie. 100Hz), the signal
is mostly mono anyway, so the effect is quite small.

Another option would be to use just the left or right signals for channels 5
AND 6...

"MOSFET" wrote in message
...

"MZ" wrote in message
...
They've redone that website since I was last on it. They had a paper on
there at one point about doing it, and their recommendation was that you
shorted the unused coil to maintain the same Q of the subwoofer. They
also
mentioned that you can "dial in" the Q you want by wiring up a
potentiometer
to the unused coil.

The whole idea is that there's motional emf induced into the unused coil,
because the laws of physics basically state that a coil moving in a
magnetic
field picks up a voltage proportional to the speed of motion. You can
actually see this by hooking a voltmeter up to your speaker and then
quickly
pushing down on the cone - it'll register on the meter. Anyway, this
voltage also acts to influence the sub's motion in a feedback manner.
This
is why it matters what you do with the unused coil.

If you're talking about hooking up both coils to two different signals,
then
these issues don't come into play. But the idea here is quite simple -
the
magnetic fields that are set up by the current going through the coils
will
sum. Some manufacturers actually claim that this could cause the coils
to
"pull against each other", but physics tells us otherwise - it would
never
get to that point because the coils are basically intertwined so whatever
magnetic field is set up by one affects the other.

That's very interesting. Forgive me if I sound retarded as I am no EE. I
understand why the coils wouldn't pull on each other, but wouldn't you
still
not want to ever do this because voltage on one coil would sometimes
cancel
out voltage on the other coil? As I recall, speakers receive alternating
current (producing the in/out motion of the cone). If you send two
different signals to each coil one signal may be on the "in" phase and the
other may be on the "out" phase, effectively cancelling out the voltage.
Admittedly, if we are taling about the left and right channels, the
cancelation effect would likely be small, but there nonethless. Is this
not
so?

MOSFET


the scary part, wouldn't all the heat still be produced, without the cooling
effect of motion? *ouch*

snip
I am really wondering if there is a noticeable effect that JL Audio
believes may occur, which is to "create undesirable non-linearities
and distortion because different input signals at each voice coil
create shifts in the speakers electrical parameters."

What I believe they may be referring to with that sentence is the shift in
Qts when you leave the unused coil open because of a decrease in Qms (?). I
don't remember exactly why the Qts remains constant when you short the
coil - it has something to do with a shift in the Qes directly offsetting
the Qms when doing so, resulting in a Qts the same as using both coils.
Maybe someone else can chime in to clarify this. But there's really no such
thing as a "wrong" Q. It's a matter of personal preference, which is why
Adire talks about it being possible to tweak this value by installing a
potentiometer.

As for distortions and non-linearities, I don't see how this could occur
either by using only one coil or using the two coils to sum mono.

I'm sure the real reason JL recommends against it is because they're afraid
of user error. People may leave the unused coil open, wire the two coils
out of phase, filter one output but not the other, etc. And the power
handling capabilities of the woofer will slightly decrease when using only
one coil, which might end up in a higher returns %.

I wish there was some concrete evidence to support/debunk what JL Audio
says on their site regarding this topic, since most people, including
myself, are prone to believing whatever JL Audio says.

I am definitely looking forward to Adire's response to my e-mail
however and would very much like to hear what their take on the issues
is.

I understand. When I try to figure out the answer to a question, though,
I'm more inclined to agree with the side that gives an explanation than the
side that doesn't. Adire has given an explanation, whereas JL has
consistently remained vague. (not to mention the other factual errors on
their website which speaks volumes about their competency)

In article ,
"Dark1" wrote:

"MOSFET" wrote in message
...

"MZ" wrote in message
...
They've redone that website since I was last on it. They had a paper on
there at one point about doing it, and their recommendation was that you
shorted the unused coil to maintain the same Q of the subwoofer. They
also
mentioned that you can "dial in" the Q you want by wiring up a
potentiometer
to the unused coil.

The whole idea is that there's motional emf induced into the unused coil,
because the laws of physics basically state that a coil moving in a
magnetic
field picks up a voltage proportional to the speed of motion. You can
actually see this by hooking a voltmeter up to your speaker and then
quickly
pushing down on the cone - it'll register on the meter. Anyway, this
voltage also acts to influence the sub's motion in a feedback manner.
This
is why it matters what you do with the unused coil.

If you're talking about hooking up both coils to two different signals,
then
these issues don't come into play. But the idea here is quite simple -
the
magnetic fields that are set up by the current going through the coils
will
sum. Some manufacturers actually claim that this could cause the coils
to
"pull against each other", but physics tells us otherwise - it would
never
get to that point because the coils are basically intertwined so whatever
magnetic field is set up by one affects the other.

That's very interesting. Forgive me if I sound retarded as I am no EE. I
understand why the coils wouldn't pull on each other, but wouldn't you
still
not want to ever do this because voltage on one coil would sometimes
cancel
out voltage on the other coil? As I recall, speakers receive alternating
current (producing the in/out motion of the cone). If you send two
different signals to each coil one signal may be on the "in" phase and the
other may be on the "out" phase, effectively cancelling out the voltage.
Admittedly, if we are taling about the left and right channels, the
cancelation effect would likely be small, but there nonethless. Is this
not
so?

MOSFET


the scary part, wouldn't all the heat still be produced, without the cooling
effect of motion? *ouch*



AFAIK The 2 coils are wrapped around the same former. Once you factor in
the decreased power handling resulting from the use of only one coil,
the sub will efficiently cool itself.

--
Cyrus

*coughcasaucedoprodigynetcough*