DEH-P3800MP can drive a subwoofer off of HU power?

[Daniel W. Rouse Jr.]

Ok, so I'm reading the manual of the Pioneer DEH-P3800MP and it's showing
that it can drive a subwoofer just off of headunit power (70W output)? But
my research is also showing that many subwoofers need well over 100W power
RMS.

So, are there actually subwoofers out there that can be driven by this
headunit without an amp? Or is this more of "proof of concept" function
(e.g., yes, the unit can *technically* drive a subwoofer) and in all
reality, an amp is actually required (as I would expect it to be required)
to drive subwoofers to their opimum output?

[KU40]

I can't download the owner's manual because pioneer is dumb and makes
you log in, but http://tinyurl.com/yzrard says it's just the normal 50
x 4 max, 22 x 4 rms. sure you can drive a sub with it, it's just like
any other amplifier, but.....you'll only get 22 watts.


--
KU40

[bob wald]

he is wrong about getting only 22watts.you may get more/les depending on
electrical system.

[Matt Ion]

bob wald wrote:
> he is wrong about getting only 22watts.you may get more/les depending on
> electrical system.

Which is really irrelevant... the reality of it is, ANY head unit CAN "drive a
subwoofer". Whether it can drive it any usable level is the question, and the
answer is just about universally "no". A very efficient small (8") sub MIGHT be
audible with 70W of deck power, but wouldn't really give you any acceptable bass.

I wouldn't automatically say 70W isn't enough - Bob is partly right, it can vary
(a little bit) with the electrical system, but also depends on the design of the
amp. I used to have a Rodek amp that was *rated* 2x30W, but it could draw up to
10A and SHOOK my little Mazda driving only a pair of 8" Orion subs.

When I was installing in a shop, we did a system in one guy's car that used
Quart separates in all four corners, and a huge box with four 12" M&M subs in
isobaric pairs, and four 8" M&Ms off to the sides, all driven by two Autotek
amps that were *rated* at 4x22W but could run 1-ohm stable. Tuned for flat
response, the car still exceeded 140dB SPL with pink noise (the owner fiddled
with the system before he took it down to the soundoff and completely tanked
everything but the SPL comps.... idiot).

So yes, 70W COULD drive a sub... but I wouldn't count on it being able to
actually deliver that kind of power, and certainly not to deliver and sort of
significant current.

[KU40]

bob wald Wrote:
> he is wrong about getting only 22watts.you may get more/les depending
> on
> electrical system.
give me a frickin break bob. I have yet to run into a vehicle that
can't run a head unit and it's tremendous 10 amps maximum current draw.
An automotive battery by itself could run a head unit at maximum volume
by itself for hours.


--
KU40

[Daniel W. Rouse Jr.]

"Matt Ion" > wrote in message
news:YfuYg.146634$R63.73986@pd7urf1no...
> bob wald wrote:
> > he is wrong about getting only 22watts.you may get more/les depending on
> > electrical system.
>
> Which is really irrelevant... the reality of it is, ANY head unit CAN
"drive a
> subwoofer". Whether it can drive it any usable level is the question, and
the
> answer is just about universally "no". A very efficient small (8") sub
MIGHT be
> audible with 70W of deck power, but wouldn't really give you any
acceptable bass.
>
[snip...]

That's what I was thinking, but I thought I'd ask for sure.

More specifically, here's what Pioneer has in the manual under the Audio
section:

Continuous power output is 22W per channel minimum into 4 ohms, both
channels driven 50 to 15000 Hz with no more than 5% THD.

Maximum power output.......
50W x 4
50W x 2/4 ohm + 70W X 1/2 ohm (for subwoofer)

Load Impedance........
4 - 8 ohms x 4
4 - 8 ohms x 2 + 2 ohms x 1

(then a bunch of equalizer specifications)

Subwoofer:
Frequency........ 50/63/80/100/125 Hz
Slope............ -18 dB/oct
Gain............. +/-12 dB
Phase............ Normal/Reverse

Also, since I'm seeing that even the cheapest (4 ohm) sub available
(something like an 8 inch Roadmaster RSW80 which only goes down to 40 Hz and
is definitly not a high end sub by any means) is rated at 80W RMS/200W peak,
while something of much higher quality like a 12 inch Pioneer TS-W301R is
800 W max power (and I'll assume well over 100 W RMS power recommended to
get decent bass output): no I don't think I'll drive a subwoofer off of
headunit power unless I can actually find a decent 2 ohm sub that the
headunit can drive without serious clipping issues.

[MOSFET]

I don't think anyone's mentioned this yet so I will.

First, as Matt and KU40 said, ANY HU can drive a subwoofer, it's just how
much output you will get is likely to not be much at 22 watts RMS.

BUT WHAT YOU CANNOT DO WITH A HU IS BRIDGE TWO CHANNELS INTO ONE TO DRIVE
YOUR SUB (unlike most two channel amplifiers).

There are no HU's out there (that I know of) that are 2 ohm stable and if
you try to do this you will likely fry your HU (or at least throw it into
protection mode).

Perhaps you know this already. I bring it up because if someone were to try
to drive a single sub with a HU there would be a natural inclination to want
to use two of the four channels to drive the sub/subs (I mean, what do you
do with THREE left over channels?).

Of course, if you are driving two 4 ohm subs, you can simply use one channel
of your HU for one sub and another channel for the other. JUST DON'T BRIDGE.

MOSFET



"Daniel W. Rouse Jr." > wrote in message
...
> Ok, so I'm reading the manual of the Pioneer DEH-P3800MP and it's showing
> that it can drive a subwoofer just off of headunit power (70W output)? But
> my research is also showing that many subwoofers need well over 100W power
> RMS.
>
> So, are there actually subwoofers out there that can be driven by this
> headunit without an amp? Or is this more of "proof of concept" function
> (e.g., yes, the unit can *technically* drive a subwoofer) and in all
> reality, an amp is actually required (as I would expect it to be required)
> to drive subwoofers to their opimum output?
>
>

[MOSFET]

> Load Impedance........
> 4 - 8 ohms x 4
> 4 - 8 ohms x 2 + 2 ohms x 1
>

Hold the phone.....

2 ohm stable?

It appear that you CAN bridge channels 3 and 4 into one channel as those two
channels appear to be 2 ohm stable. Disregard my other post regarding
bridging.

Clearly, you WOULD get MUCH more than 22 watts for your sub if you did this
(bridge those two channels).

Matt and KU40, is that how it appears to you guys?

MOSFET

[KU40]

hmm, I've never seen a head unit that can drive that low of an impedence
load, nor one that can drop below 4 ohms if bridged (which I'm not sure
is an option yet). Especially on a 130 dollar head unit. seems a
little iffy to me, even moreso since it's not listed as a feature on
their product description.

but at any rate, driving any decent subwoofer with a head unit is not a
very good option. Just get an amp.


--
KU40

[MOSFET]

Especially on a 130 dollar head unit. seems a
> little iffy to me, even moreso since it's not listed as a feature on
> their product description.
>
> but at any rate, driving any decent subwoofer with a head unit is not a
> very good option. Just get an amp.
>
Good advice, I didn't know it was a $130 HU. Yes, that does make it sound
more iffy to me as well.

But, on the other hand, with amplifier technology becoming ever more
efficient (Class D, Class T, etc.) and smaller, WHY NOT build a HU that can
be bridged to drive a sub? It's not a bad idea.

MOSFET

[Eric Desrochers]

MOSFET > wrote:

> BUT WHAT YOU CANNOT DO WITH A HU IS BRIDGE TWO CHANNELS INTO ONE TO DRIVE
> YOUR SUB (unlike most two channel amplifiers).

That's correct. You cannot bridge HU channels because they are ALREADY
bridged by design. That's the only way to have more than 5 watts per
channel with a 12 volts supply.

Stand alone amps CAN and indeed HAVE more than this because their power
supplies kinda "fabricate" higher rail voltage. This is impossible in a
HU because of unsufficient space and heat dissipation capability, as
well as price point considerations.

> Of course, if you are driving two 4 ohm subs, you can simply use one channel
> of your HU for one sub and another channel for the other. JUST DON'T BRIDGE.

Another possibility is using a dual voice coil sub. My "short on cash"
brother use such a system in his truck and even if the sound is not that
loud, you immediately know by hearing that a 12 inches is hiding
somewhere!

--
Eric (Dero) Desrochers
http://homepage.mac.com/dero72

Hiroshima 45, Tchernobyl 86, Windows 95

[MOSFET]

Well Eric, what about this 2 ohm stable spec. that the OP gave?

Do you buy it? Do you think he can bridge channels 3 and 4?

MOSFET

[e-nigma]

"MOSFET" > wrote in message
...
> Well Eric, what about this 2 ohm stable spec. that the OP gave?
>
> Do you buy it? Do you think he can bridge channels 3 and 4?
>
> MOSFET
>
>

Pioneer has had some units in the last 4-5 years that the rear channels were
bridgeable for subwoofer

[Matt Ion]

Daniel W. Rouse Jr. wrote:
> "Matt Ion" > wrote in message
> news:YfuYg.146634$R63.73986@pd7urf1no...
>
>>bob wald wrote:
>>
>>>he is wrong about getting only 22watts.you may get more/les depending on
>>>electrical system.
>>
>>Which is really irrelevant... the reality of it is, ANY head unit CAN
>
> "drive a
>
>>subwoofer". Whether it can drive it any usable level is the question, and
>
> the
>
>>answer is just about universally "no". A very efficient small (8") sub
>
> MIGHT be
>
>>audible with 70W of deck power, but wouldn't really give you any
>
> acceptable bass.
>
> [snip...]
>
> That's what I was thinking, but I thought I'd ask for sure.
>
> More specifically, here's what Pioneer has in the manual under the Audio
> section:
>
> Continuous power output is 22W per channel minimum into 4 ohms, both
> channels driven 50 to 15000 Hz with no more than 5% THD.
>
> Maximum power output.......
> 50W x 4
> 50W x 2/4 ohm + 70W X 1/2 ohm (for subwoofer)

Okay, I see... it looks like they're actually bridging one pair of channels for
a sub output.

The fact that bridging should normally approximately double the power of those
two channels into the same load, but instead is increasing less than 50%, and
into half the load, is telling: that thing is NOT going to deliver much current.
Not surprising: there simply isn't room inside a head unit for the size of
switching power supply and high-current transistors necessary to deliver any
kind of decent power.

[Matt Ion]

Eric Desrochers wrote:
> MOSFET > wrote:
>
>
>>BUT WHAT YOU CANNOT DO WITH A HU IS BRIDGE TWO CHANNELS INTO ONE TO DRIVE
>>YOUR SUB (unlike most two channel amplifiers).
>
>
> That's correct. You cannot bridge HU channels because they are ALREADY
> bridged by design. That's the only way to have more than 5 watts per
> channel with a 12 volts supply.
>
> Stand alone amps CAN and indeed HAVE more than this because their power
> supplies kinda "fabricate" higher rail voltage. This is impossible in a
> HU because of unsufficient space and heat dissipation capability, as
> well as price point considerations.

It certainly is POSSIBLE to put a switching supply inside a head unit (to
"fabricate" higher rail voltage). It's not PRACTICAL to make one that delivers
any significant amount of current.

[Matt Ion]

MOSFET wrote:
> Especially on a 130 dollar head unit. seems a
>
>>little iffy to me, even moreso since it's not listed as a feature on
>>their product description.
>>
>>but at any rate, driving any decent subwoofer with a head unit is not a
>>very good option. Just get an amp.
>>
>
> Good advice, I didn't know it was a $130 HU. Yes, that does make it sound
> more iffy to me as well.
>
> But, on the other hand, with amplifier technology becoming ever more
> efficient (Class D, Class T, etc.) and smaller, WHY NOT build a HU that can
> be bridged to drive a sub? It's not a bad idea.

Regardless of how efficient you make the amp, output power is still a function
of voltage vs. current. Even with a 100% efficient system, power in has to
equal power out, and the output stages of the amp itself have to be able to
handle that power. That means sufficient cooling (typically big heat sinks) for
relatively large transistors in the output stage. No matter what you do,
there's just not room inside a standard head unit for an output stage that can
deliver any significant power. Maybe if you started looking at double-DIN-sized
HUs and some kind of liquid cooling for the output stages, you could get
closer... but then you're a bit out of the $150 range :)

[Eric Desrochers]

MOSFET > wrote:

> Well Eric, what about this 2 ohm stable spec. that the OP gave?

2 ohm stable have nothing to do with bridgeable. Most home stereos can
tolerate a 4 ohms load even if designed to operate at 8 ohms. That
doesn't mean you can bridge them!

> Do you buy it? Do you think he can bridge channels 3 and 4?

I'm not familiar with this unit and i'm too lazy to look-up a spec sheet
right now! Typically, HU are using BTL outputs (ie bridged). You
cannot bridge something that is already bridged!

The only way they could do it is by using a small PWM supply (like in
outboard amps) and using "normal" , non-bridged outputs. I seriously
doubt they can do it in a 150$ HU.

Maybe, just *maybe* they are suggesting using the + from channel 3 with
the - of channel 4. It won't give you any more power but will derive a
correctly summed mono channel. But please, don't try this at home
unless your owner manual clearly state you can!

Also, I think it's possible for this 4 X 50 watts (max) unit to put out
4 X 70 watts (max) into 2 ohms (ie about 35 watts rms per channel).

--
Eric (Dero) Desrochers
http://homepage.mac.com/dero72

Hiroshima 45, Tchernobyl 86, Windows 95

[Eric Desrochers]

Matt Ion > wrote:

> Regardless of how efficient you make the amp, output power is still a function
> of voltage vs. current. Even with a 100% efficient system, power in has to
> equal power out, and the output stages of the amp itself have to be able to
> handle that power. That means sufficient cooling (typically big heat sinks)

Err, a 100% efficient amp would dissipate NO HEAT, by definition.

--
Eric (Dero) Desrochers
http://homepage.mac.com/dero72

Hiroshima 45, Tchernobyl 86, Windows 95

[Daniel W. Rouse Jr.]

"MOSFET" > wrote in message
...
> Well Eric, what about this 2 ohm stable spec. that the OP gave?
>
> Do you buy it? Do you think he can bridge channels 3 and 4?
>
> MOSFET
>
>
I can confirm that I am not able to bridge the rear speaker channels, if by
bridging that means connecting (splicing) both (+) together and separately,
splicing both (-) together.

I re-checked the Installation Manual and it has the following warning:

Since a unique BPTL circuit is employed, never wire so the speaker leads are
directly grounded or the left and right (-) speaker leads are common.

[Daniel W. Rouse Jr.]

"MOSFET" > wrote in message
m...
> Especially on a 130 dollar head unit. seems a
> > little iffy to me, even moreso since it's not listed as a feature on
> > their product description.
> >
> > but at any rate, driving any decent subwoofer with a head unit is not a
> > very good option. Just get an amp.
> >
> Good advice, I didn't know it was a $130 HU. Yes, that does make it sound
> more iffy to me as well.
>
> But, on the other hand, with amplifier technology becoming ever more
> efficient (Class D, Class T, etc.) and smaller, WHY NOT build a HU that
can
> be bridged to drive a sub? It's not a bad idea.
>
That's why I'm hoping this may actually work.

For a $130 HU, this deck plays MP3/WMA/WAV in addition to standard CD's, and
also gets decent AM/FM reception, but the Front Image Enhancer (FIE)
function isn't outputting enough clear low bass (for me anyway) through rear
full-range speakers. Turning the volume up loud enough, around 42 out of 62,
with the FIE enabled starts obvious clipping when playing CD's.

The bass doesn't have to seriously boom, though, it just has to blend in
with the rest of the frequencies without being either overpowering or
underpowered.

On the other hand, I'm also prepared to start researching amps, since this
HU also has preamp outputs.

[Daniel W. Rouse Jr.]

"Eric Desrochers" > wrote in message
...
> MOSFET > wrote:
>
> > BUT WHAT YOU CANNOT DO WITH A HU IS BRIDGE TWO CHANNELS INTO ONE TO
DRIVE
> > YOUR SUB (unlike most two channel amplifiers).
>
> That's correct. You cannot bridge HU channels because they are ALREADY
> bridged by design. That's the only way to have more than 5 watts per
> channel with a 12 volts supply.
>
> Stand alone amps CAN and indeed HAVE more than this because their power
> supplies kinda "fabricate" higher rail voltage. This is impossible in a
> HU because of unsufficient space and heat dissipation capability, as
> well as price point considerations.
>
> > Of course, if you are driving two 4 ohm subs, you can simply use one
channel
> > of your HU for one sub and another channel for the other. JUST DON'T
BRIDGE.
>
> Another possibility is using a dual voice coil sub. My "short on cash"
> brother use such a system in his truck and even if the sound is not that
> loud, you immediately know by hearing that a 12 inches is hiding
> somewhere!
>
For a dual voice coil sub, that would be putting one rear channel output
into one voice coil input and another rear channel output into the other
voice coil input, right?

[Captain_Howdy]

The rear channels only, do bridge to drive a sub with a killer 70 watts peak
power rating.

[Captain_Howdy]

You can use either the rear left or rear right outputs to hook up to your sub.
Make sure that you have the HU set to rear sub mode this will place the rears
into monaural mode.




In article >, "Daniel W. Rouse
Jr." > wrote:
>"MOSFET" > wrote in message
...
>> Well Eric, what about this 2 ohm stable spec. that the OP gave?
>>
>> Do you buy it? Do you think he can bridge channels 3 and 4?
>>
>> MOSFET
>>
>>
>I can confirm that I am not able to bridge the rear speaker channels, if by
>bridging that means connecting (splicing) both (+) together and separately,
>splicing both (-) together.
>
>I re-checked the Installation Manual and it has the following warning:
>
>Since a unique BPTL circuit is employed, never wire so the speaker leads are
>directly grounded or the left and right (-) speaker leads are common.
>
>
>

[Captain_Howdy]

Unless your sub has dual 2ohm voice coils that are wired for a 4ohm load,
you're **** out of luck. If you wire the rear into anything less then a 4ohm
load, you'll be out of a hu. Some how I don't think that Pioneer has 12" subs
and dual voice coils in mind with this option.

Why is this thread so long, this is not rocket science.

>>
>For a dual voice coil sub, that would be putting one rear channel output
>into one voice coil input and another rear channel output into the other
>voice coil input, right?
>
>
>

[Matt Ion]

Daniel W. Rouse Jr. wrote:


> I can confirm that I am not able to bridge the rear speaker channels, if by
> bridging that means connecting (splicing) both (+) together and separately,
> splicing both (-) together.

Bridging is typically done by connecting the speaker to the + output of one
channel and the - output of the other. The other two terminals are common
internally.

[Matt Ion]

Eric Desrochers wrote:
> Matt Ion > wrote:
>
>
>>Regardless of how efficient you make the amp, output power is still a function
>>of voltage vs. current. Even with a 100% efficient system, power in has to
>>equal power out, and the output stages of the amp itself have to be able to
>>handle that power. That means sufficient cooling (typically big heat sinks)
>
>
> Err, a 100% efficient amp would dissipate NO HEAT, by definition.

Err... right, my bad. :)

But since 100% efficiency is impossible, the rest of my point still applies :)

[MOSFET]

> The fact that bridging should normally approximately double the power of
those
> two channels into the same load, but instead is increasing less than 50%,
and
> into half the load, is telling: that thing is NOT going to deliver much
current.
> Not surprising: there simply isn't room inside a head unit for the size
of
> switching power supply and high-current transistors necessary to deliver
any
> kind of decent power.

Well that's what I thought, too. But I have seen some pretty damn small
Class T amps. And yes, heat is an issue as there is no such thing as a 100%
efficient amp. But apparently some Class T amps are so efficient their
chassis is made of plastic (bazooka had a line of these I believe). PLASTIC
FOR PETE'S SAKE!!

So perhaps heat would not be a major issue in a HU if you used Class T.

MOSFET

[Captain_Howdy]

This thread is silly, and to compare the workings of a stand alone amplifier
to one of a head unit is just ignorant. Most head unit amplifiers consist on a
single IC that delivers 4 channels of amplification. It's just funny to see
common sense go out the window.



In article >, "MOSFET"
> wrote:
>> The fact that bridging should normally approximately double the power of
>those
>> two channels into the same load, but instead is increasing less than 50%,
>and
>> into half the load, is telling: that thing is NOT going to deliver much
>current.
>> Not surprising: there simply isn't room inside a head unit for the size
>of
>> switching power supply and high-current transistors necessary to deliver
>any
>> kind of decent power.
>
>Well that's what I thought, too. But I have seen some pretty damn small
>Class T amps. And yes, heat is an issue as there is no such thing as a 100%
>efficient amp. But apparently some Class T amps are so efficient their
>chassis is made of plastic (bazooka had a line of these I believe). PLASTIC
>FOR PETE'S SAKE!!
>
>So perhaps heat would not be a major issue in a HU if you used Class T.
>
>MOSFET
>
>

[Eric Desrochers]

Daniel W. Rouse Jr. > wrote:

> For a dual voice coil sub, that would be putting one rear channel output
> into one voice coil input and another rear channel output into the other
> voice coil input, right?

Yes, but as another poster said, check that it's a 4 onhm + 4 ohms.

--
Eric (Dero) Desrochers
http://homepage.mac.com/dero72

Hiroshima 45, Tchernobyl 86, Windows 95

[Eric Desrochers]

> Err... right, my bad. :)
>
> But since 100% efficiency is impossible, the rest of my point still
> applies :)

Of course! :)

But they are getting surprisingly close! The Eclipse XA2000 is reported
to have a 91% efficiency at 1/3 power! The thing will produce 200 watts
from only 220 watts of power! Dissipating 20 watts is not much more
than the average domelight!!

--
Eric (Dero) Desrochers http://homepage.mac.com/dero72

Hiroshima 45, Tchernobyl 86, Windows 95

[Eric Desrochers]

Captain_Howdy > wrote:

> This thread is silly, and to compare the workings of a stand alone amplifier
> to one of a head unit is just ignorant. Most head unit amplifiers consist on a
> single IC that delivers 4 channels of amplification. It's just funny to see
> common sense go out the window.

A watt is a watt is a watt.

That it comes from a tube, a transistor or an IC, Class A, B, AB or D,
what difference it makes given the allowed load is respected?

If a HU puts out 22 watts at 4 ohms, you could feed it into *any* 4 ohms
load, be it a speaker, small or big, a resistor, even a ****ing bulb
light, the 22 watts are going to be produced!

--
Eric (Dero) Desrochers
http://homepage.mac.com/dero72

Hiroshima 45, Tchernobyl 86, Windows 95

[Matt Ion]

Eric Desrochers wrote:
> Captain_Howdy > wrote:
>
>
>>This thread is silly, and to compare the workings of a stand alone amplifier
>>to one of a head unit is just ignorant. Most head unit amplifiers consist on a
>>single IC that delivers 4 channels of amplification. It's just funny to see
>>common sense go out the window.
>
>
> A watt is a watt is a watt.
>
> That it comes from a tube, a transistor or an IC, Class A, B, AB or D,
> what difference it makes given the allowed load is respected?
>
> If a HU puts out 22 watts at 4 ohms, you could feed it into *any* 4 ohms
> load, be it a speaker, small or big, a resistor, even a ****ing bulb
> light, the 22 watts are going to be produced!

Except that no speaker provides a constant impedence across its entire response
curve. A speaker at resonance has an impedence of very close to 0. An amp that
can't deliver the necessary CURRENT at that point, will wither and die before long.

[bob wald]

partly right? thats like hes partly dead.lol
either i am or not right. lol
glad i dont ask advice from you people.
lol... as if.
also you might get less than 22 if your systems weak.
also 21rms to 22.5rms is a big difference. to some.
thats per channel....1.5rms= over 6%

[Captain_Howdy]

Without any respect of how a watt is made, I guess that a watt is a watt. In
that respect we might as well compare head unit amplifiers to nuclear power
stations, since a watt is a watt.




In article >,
(Eric Desrochers) wrote:
>Captain_Howdy > wrote:
>
>> This thread is silly, and to compare the workings of a stand alone amplifier
>> to one of a head unit is just ignorant. Most head unit amplifiers consist on
> a
>> single IC that delivers 4 channels of amplification. It's just funny to see
>> common sense go out the window.
>
>A watt is a watt is a watt.
>
>That it comes from a tube, a transistor or an IC, Class A, B, AB or D,
>what difference it makes given the allowed load is respected?
>
>If a HU puts out 22 watts at 4 ohms, you could feed it into *any* 4 ohms
>load, be it a speaker, small or big, a resistor, even a ****ing bulb
>light, the 22 watts are going to be produced!
>

[zek]

MOSFET wrote:
> > Load Impedance........
> > 4 - 8 ohms x 4
> > 4 - 8 ohms x 2 + 2 ohms x 1
> >
>
> Hold the phone.....
>
> 2 ohm stable?
>
> It appear that you CAN bridge channels 3 and 4 into one channel as those two
> channels appear to be 2 ohm stable. Disregard my other post regarding
> bridging.
>
> Clearly, you WOULD get MUCH more than 22 watts for your sub if you did this
> (bridge those two channels).
>
> Matt and KU40, is that how it appears to you guys?


The confusing part, unless the HU has a power supply, 4 channels are
allready bridged, You can't double bridge. The HU companies like to
rate their components to the max. You can't really get over 20 watts
without a power supply. These HU are probably maxed out on the input
voltage when they make these claims.

greg

[Eric Desrochers]

Matt Ion > wrote:

> Except that no speaker provides a constant impedence across its entire
> response curve.

Yeah that's true but it has nothing to do with what the other poster
stated.

> A speaker at resonance has an impedence of very close to 0.

Err. Free air or sealed, at the resonance, the excursion is at maximum,
the back emf is at maximum, hence the impedance is *maximum*. The point
at which the impedance *may* fall below the nominal impedance is in the
mid bass range. Do a google search for speaker impedance curve. Here
is an fine example : http://www.churchsoundcheck.com/imp1.html

In a ported box, the *system* (driver + box + port) impedance will
indeed be low at the port resonance. It's logical since the cone motion
is nearly 0 at that frequency.

But rest assured it stays well over 0 ohms at all time. Else, amps and
HU would go in protect mode left and right.

I never heard of a 4 ohms nominal driver that goes near 0 in its curve,
maybe you have an example, I'd like to see this!

> An amp that can't deliver the necessary CURRENT at that point, will
> wither and die before long.

True. That's why those who wants better sound will use stand alone
amps. But Captain Howdy seemed to imply that HU power was somewhat
"particular" and could not under any circonstance feed a sub. Well,
it's doable and done, but obviously it's not the way to go for superior
sound quality and level.

In fact, millions and millions of HU works just fine feeding full range
coax, which *also* have a minimum impedance in their curve. Why
suddenly a sub would be worst than full range?

Hope this helps.

--
Eric (Dero) Desrochers http://homepage.mac.com/dero72

Hiroshima 45, Tchernobyl 86, Windows 95

[Matt Ion]

Eric Desrochers wrote:
> Matt Ion > wrote:
>
>
>>Except that no speaker provides a constant impedence across its entire
>>response curve.
>
>
> Yeah that's true but it has nothing to do with what the other poster
> stated.
>
>
>>A speaker at resonance has an impedence of very close to 0.
>
>
> Err. Free air or sealed, at the resonance, the excursion is at maximum,
> the back emf is at maximum, hence the impedance is *maximum*. The point
> at which the impedance *may* fall below the nominal impedance is in the
> mid bass range. Do a google search for speaker impedance curve. Here
> is an fine example : http://www.churchsoundcheck.com/imp1.html

Oops, you're correct... that's what I get for posting when half asleep.

> In fact, millions and millions of HU works just fine feeding full range
> coax, which *also* have a minimum impedance in their curve. Why
> suddenly a sub would be worst than full range?

Well, passive crossovers come into play once you start looking at most multi-way
speaker sets... not that it necessarily lowers overall impedence, but they can
start introdocing some pretty complex impedence curves, especially with more
reactive LC combinations.

[Ericfg]

bob wald wrote:
> partly right? thats like hes partly dead.lol
> either i am or not right. lol
> glad i dont ask advice from you people.
> lol... as if.
> also you might get less than 22 if your systems weak.
> also 21rms to 22.5rms is a big difference. to some.
> thats per channel....1.5rms= over 6%

God I love bob.
There. I said it. I'm "out".