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fone.freaky
 
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Default Consequences of replacing 8 ohm woofer with 4 ohm woofer in home theater sub?

I have an Atlantic Technology 262 PBM sub woofer in my home theater speaker
setup. Its a sealed enclosure, powered 12 inch sub woofer rated at 150 watts
(I believe).

The factory woofer in it blew out recently, so I replaced it (temporarily)
with a 4 ohm Kicker C-12 car audio sub woofer I happen to have laying around
from my car audio hay-days. Now, I know the internal amp and adjustable
cross over (of the sub woofer enclosure) is obviously tuned and rated for
the original 8 ohm driver. And as I recall the lower the ohm rating of a
speaker the more power it pulls? ??? (I seem to remember something about
this when I was younger and more into car audio- when amps were rated at 500
watts @ 1 ohm ---- that kind of thing)

ANYWAY: The box sounds ok with the Kicker C12 4ohm driver installed now, it
does sound more bass'ey to me, but the sub has been blown out for several
days and of course I'm being EXTREMELY critiqueful of it right now, so it
may be in my mind (or ears as it were)

Bottom line: What are the ups and downs of replacing a home theater 8 ohm
sub woofer with a car audio 4 ohm sub woofer ?

PLEASE GIVE ME ADVICE!

Thanks in advance.
-Toaster

(remove the -NOSPAM- to send any emails)


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tempus fugit
 
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You're on the right track here - the 4 ohm sub will draw more current and
thus output more power, so all you need to do is make sure that the amp that
is driving it is capable of driving a 4 ohm load safely. You should be able
to find this out from the owner's manual, or maybe even the back of the amp.


"fone.freaky" wrote in message
...
I have an Atlantic Technology 262 PBM sub woofer in my home theater

speaker
setup. Its a sealed enclosure, powered 12 inch sub woofer rated at 150

watts
(I believe).

The factory woofer in it blew out recently, so I replaced it (temporarily)
with a 4 ohm Kicker C-12 car audio sub woofer I happen to have laying

around
from my car audio hay-days. Now, I know the internal amp and adjustable
cross over (of the sub woofer enclosure) is obviously tuned and rated for
the original 8 ohm driver. And as I recall the lower the ohm rating of a
speaker the more power it pulls? ??? (I seem to remember something about
this when I was younger and more into car audio- when amps were rated at

500
watts @ 1 ohm ---- that kind of thing)

ANYWAY: The box sounds ok with the Kicker C12 4ohm driver installed now,

it
does sound more bass'ey to me, but the sub has been blown out for several
days and of course I'm being EXTREMELY critiqueful of it right now, so it
may be in my mind (or ears as it were)

Bottom line: What are the ups and downs of replacing a home theater 8 ohm
sub woofer with a car audio 4 ohm sub woofer ?

PLEASE GIVE ME ADVICE!

Thanks in advance.
-Toaster

(remove the -NOSPAM- to send any emails)




  #3   Report Post  
Peter Larsen
 
Posts: n/a
Default

"fone.freaky" wrote:

I have an Atlantic Technology 262 PBM sub woofer in my home theater
speaker setup. Its a sealed enclosure, powered 12 inch sub woofer
rated at 150 watts (I believe).


Closed box and powered == you can replace bass unit without loosing too
much sleep over impedance concerns.

The factory woofer in it blew out recently, so I replaced it
(temporarily) with a 4 ohm Kicker C-12 car audio sub woofer


I am tired of googling for its Qt and Fs, all I got was the vague
impression that 1.5 to 3 cubic feet is a suitable size range for a
closed box for it and that its power handling is adequate.

Now, I know the internal amp and adjustable cross over (of
the sub woofer enclosure) is obviously tuned and rated for
the original 8 ohm driver.


This is not an issue, at least not in terms of frequency response.

And as I recall the lower the ohm rating of a
speaker the more power it pulls? ???


Yerp, this means that if you play it so loud that the amplifier clips
the amp could blow a fuse and that you should check just how hot the
amps assumed cooling fins get if you play it very loud for extended
time.

ANYWAY: The box sounds ok with the Kicker C12 4ohm driver
installed now, it does sound more bass'ey to me,


Is there any wadding of any kind in the box? - no? - thought so. Try
this: take the embroidered pillow on the couch, the one you got as a
gift and hate, and toss it into the box and listen again. If you want to
purchase dedicated acoustic damping material, then feel free to so do.
Even if it does contain damping material on the walls of the box, do
this or something similar that addes damping material to the box center.
Doing that will reduce the acoustic Q and make the bass tighter and more
precise. Just toossing loosely fluffed acoustilux or similar acoustic
wadding into the box will have a similar effect. The embroided pillow on
the couch that you got as a gift and hate may not be uniquely the best
material for this, but it is a fast and easy way to test if that damping
approach is likely to improve the sound.

Bottom line: What are the ups and downs of replacing a home theater 8 ohm
sub woofer with a car audio 4 ohm sub woofer ?


In a closed box, the answer is that you will probably get a change of
bass tonal balance. The impedance is not at all an acoustic issue with a
powered box, it may or may not be an issue to the amp, which may become
too hot or blow a fuse or clip at unexpected low level if made "too
tightly" for driving the original 8 Ohm unit, my guess is that it is
unlikely to be any kind of issue at all.

PLEASE GIVE ME ADVICE!


Enjoy. If you can find the Thiele-Small specs for the unit you could try
asking again and someone here may be able to suggest an optimum box for
that C-12, I have used fairly much time googling for them and not found
them.

-Toaster



Kind regards

Peter Larsen


--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************
  #4   Report Post  
Jim Adney
 
Posts: n/a
Default

On Sat, 11 Jun 2005 00:49:40 -0500 "fone.freaky"
wrote:

Bottom line: What are the ups and downs of replacing a home theater 8 ohm
sub woofer with a car audio 4 ohm sub woofer ?


For the same applied voltage the 4 Ohm speaker will draw 2 twice as
much current, which will put double the electrical power into it.

To put the same electrical power into it, you will have to reduce the
voltage by the square root of 2, which will still mean that the
current draw will be up by the same factor.

So it all depends on whether your amp can deliver the extra current or
not. If this was a unified system (sub-woofer with amp built in) then
it is unlikely that the amp is going to be happy with this. The most
likely outcome is that the output transistors will blow the next time
you turn the volume up.

I'm guessing that high volume is what blew the original speaker, so it
seems likely that you will do this again, with slightly different
results.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------
  #5   Report Post  
fone.freaky
 
Posts: n/a
Default

The box does have factory "wadding" inside. The amp's cooling fins
(heatsink) get warm, never "hot". I have no idea if they got this warm
before or not- I know I never touched them or ever payed attention

I've been on the hunt this weekend for an 8 ohm 12" sub woofer, which is
hard if not impossible to find. I may have to order it directly from A.T. if
they'll sell it to me?

The box sounds ok with the C12 installed, its just quite "bassey"


"Peter Larsen" wrote in message
...
"fone.freaky" wrote:

I have an Atlantic Technology 262 PBM sub woofer in my home theater
speaker setup. Its a sealed enclosure, powered 12 inch sub woofer
rated at 150 watts (I believe).


Closed box and powered == you can replace bass unit without loosing too
much sleep over impedance concerns.

The factory woofer in it blew out recently, so I replaced it
(temporarily) with a 4 ohm Kicker C-12 car audio sub woofer


I am tired of googling for its Qt and Fs, all I got was the vague
impression that 1.5 to 3 cubic feet is a suitable size range for a
closed box for it and that its power handling is adequate.

Now, I know the internal amp and adjustable cross over (of
the sub woofer enclosure) is obviously tuned and rated for
the original 8 ohm driver.


This is not an issue, at least not in terms of frequency response.

And as I recall the lower the ohm rating of a
speaker the more power it pulls? ???


Yerp, this means that if you play it so loud that the amplifier clips
the amp could blow a fuse and that you should check just how hot the
amps assumed cooling fins get if you play it very loud for extended
time.

ANYWAY: The box sounds ok with the Kicker C12 4ohm driver
installed now, it does sound more bass'ey to me,


Is there any wadding of any kind in the box? - no? - thought so. Try
this: take the embroidered pillow on the couch, the one you got as a
gift and hate, and toss it into the box and listen again. If you want to
purchase dedicated acoustic damping material, then feel free to so do.
Even if it does contain damping material on the walls of the box, do
this or something similar that addes damping material to the box center.
Doing that will reduce the acoustic Q and make the bass tighter and more
precise. Just toossing loosely fluffed acoustilux or similar acoustic
wadding into the box will have a similar effect. The embroided pillow on
the couch that you got as a gift and hate may not be uniquely the best
material for this, but it is a fast and easy way to test if that damping
approach is likely to improve the sound.

Bottom line: What are the ups and downs of replacing a home theater 8

ohm
sub woofer with a car audio 4 ohm sub woofer ?


In a closed box, the answer is that you will probably get a change of
bass tonal balance. The impedance is not at all an acoustic issue with a
powered box, it may or may not be an issue to the amp, which may become
too hot or blow a fuse or clip at unexpected low level if made "too
tightly" for driving the original 8 Ohm unit, my guess is that it is
unlikely to be any kind of issue at all.

PLEASE GIVE ME ADVICE!


Enjoy. If you can find the Thiele-Small specs for the unit you could try
asking again and someone here may be able to suggest an optimum box for
that C-12, I have used fairly much time googling for them and not found
them.

-Toaster



Kind regards

Peter Larsen


--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************





  #6   Report Post  
none
 
Posts: n/a
Default

On Mon, 13 Jun 2005 11:01:52 -0500, "fone.freaky"
wrote:

The box does have factory "wadding" inside. The amp's cooling fins
(heatsink) get warm, never "hot". I have no idea if they got this warm
before or not- I know I never touched them or ever payed attention

I've been on the hunt this weekend for an 8 ohm 12" sub woofer, which is
hard if not impossible to find. I may have to order it directly from A.T. if
they'll sell it to me?

The box sounds ok with the C12 installed, its just quite "bassey"

They make a transformer thingy that allows you to adjust the ohm
rating to match the recommended load rating of your amp.
They used to sell them over at madisound.

http://www.madisound.com/

Don't know if it'll change the acoustics of the driver itself though.

"Peter Larsen" wrote in message
...
"fone.freaky" wrote:

I have an Atlantic Technology 262 PBM sub woofer in my home theater
speaker setup. Its a sealed enclosure, powered 12 inch sub woofer
rated at 150 watts (I believe).


Closed box and powered == you can replace bass unit without loosing too
much sleep over impedance concerns.

The factory woofer in it blew out recently, so I replaced it
(temporarily) with a 4 ohm Kicker C-12 car audio sub woofer


I am tired of googling for its Qt and Fs, all I got was the vague
impression that 1.5 to 3 cubic feet is a suitable size range for a
closed box for it and that its power handling is adequate.

Now, I know the internal amp and adjustable cross over (of
the sub woofer enclosure) is obviously tuned and rated for
the original 8 ohm driver.


This is not an issue, at least not in terms of frequency response.

And as I recall the lower the ohm rating of a
speaker the more power it pulls? ???


Yerp, this means that if you play it so loud that the amplifier clips
the amp could blow a fuse and that you should check just how hot the
amps assumed cooling fins get if you play it very loud for extended
time.

ANYWAY: The box sounds ok with the Kicker C12 4ohm driver
installed now, it does sound more bass'ey to me,


Is there any wadding of any kind in the box? - no? - thought so. Try
this: take the embroidered pillow on the couch, the one you got as a
gift and hate, and toss it into the box and listen again. If you want to
purchase dedicated acoustic damping material, then feel free to so do.
Even if it does contain damping material on the walls of the box, do
this or something similar that addes damping material to the box center.
Doing that will reduce the acoustic Q and make the bass tighter and more
precise. Just toossing loosely fluffed acoustilux or similar acoustic
wadding into the box will have a similar effect. The embroided pillow on
the couch that you got as a gift and hate may not be uniquely the best
material for this, but it is a fast and easy way to test if that damping
approach is likely to improve the sound.

Bottom line: What are the ups and downs of replacing a home theater 8

ohm
sub woofer with a car audio 4 ohm sub woofer ?


In a closed box, the answer is that you will probably get a change of
bass tonal balance. The impedance is not at all an acoustic issue with a
powered box, it may or may not be an issue to the amp, which may become
too hot or blow a fuse or clip at unexpected low level if made "too
tightly" for driving the original 8 Ohm unit, my guess is that it is
unlikely to be any kind of issue at all.

PLEASE GIVE ME ADVICE!


Enjoy. If you can find the Thiele-Small specs for the unit you could try
asking again and someone here may be able to suggest an optimum box for
that C-12, I have used fairly much time googling for them and not found
them.

-Toaster



Kind regards

Peter Larsen


--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************



  #7   Report Post  
Peter Larsen
 
Posts: n/a
Default

Jim Adney wrote:

I'm guessing that high volume is what blew the original speaker,
so it seems likely that you will do this again, with slightly
different results.


Yes, he may blow the fuse in the amp. From the test of the C12 I did
find when googling for its Thiele-Small data the powerhandling of the
unit is substantial.

Jim Adney



Kind regards

Peter Larsen

--
*******************************************
* My site is at:
http://www.muyiovatki.dk *
*******************************************
  #8   Report Post  
Peter Larsen
 
Posts: n/a
Default

"fone.freaky" wrote:

[fixing microserf style topposting]

ANYWAY: The box sounds ok with the Kicker C12 4ohm driver
installed now, it does sound more bass'ey to me,


Is there any wadding of any kind in the box? - no? - thought
so. Try this: take the embroidered pillow on the couch, the one
you got as a gift and hate, and toss it into the box and listen
again. If you want to purchase dedicated acoustic damping
material, then feel free to so do. Even if it does contain
damping material on the walls of the box, do this or something
similar that addes damping material to the box center.


Doing that will reduce the acoustic Q and make the bass tighter
and more precise. Just toossing loosely fluffed acoustilux or
similar acoustic wadding into the box will have a similar effect.
The embroided pillow on the couch that you got as a gift and hate
may not be uniquely the best material for this, but it is a fast
and easy way to test if that damping approach is likely to
improve the sound.


The box does have factory "wadding" inside.


Read the above again, try it or not as you please, but do understand
that wadding along the walls addresses midrange issues. It is also the
only damping that should be deployed for bass reflex bins, generally
line of sight should exist between either side of the unit and the
corresponding end of the bass reflex port(s). You can only, generally at
least - there are non-ideal bass reflex designs that rely on an acoustic
resistor, ie. damping, between loudspeaker and port to reduce the
coupling, deploy damping to the cabinent center in a closed box and you
should only do it if you need to reduce the system overall Q to
linearise the bass response. From your description just that appears to
be relevant.

The amp's cooling fins (heatsink) get warm, never "hot".


Oversimplified there is not likely to be an issue then.

I've been on the hunt this weekend for an 8 ohm 12" sub woofer,
which is hard if not impossible to find.


Monacor, Seas, Dynaudio, JBL, Scanspeak, Peerless ... just to mention
the first 6 product lines that are likely to contain something useful.

I may have to order it directly from A.T. if
they'll sell it to me?


I can't comment on this other than saying: Yees, getting the original
item is what will get your the original ssound.

The box sounds ok with the C12 installed, its just quite "bassey"


Welcome to the wonderful not so simple world of the simple closed box.
Just how large is the box?- do you have a spec sheete that perhaps came
with that C12?


Kind regards

Peter Larsen


--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************
  #9   Report Post  
 
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fone.freaky said:


I've been on the hunt this weekend for an 8 ohm 12" sub woofer, which is
hard if not impossible to find. I may have to order it directly from A.T. if
they'll sell it to me?


Try the NHT1248 available from www.madisound.com or at least it was
the last time I checked. Also Parts Express has a couple of 12"
woofers made for a dealed box.

The Kicker C12 is a good woofer, but they (Stillwater) give enclosure
recomendations that are IMO to small for home subs. A box of around 3
- 4 cubic feet is about right for this driver IMO.

The NHT 1248 works to 30 Hz before room loading in 3 cubic feet.

If you have an SPL meter and a test disk you can find out what the sub
is doing and make adjustments to see if it's OK. Perhaps some
judicious tweaking of level and xover can get it to perform the way you
like.



The box sounds ok with the C12 installed, its just quite "bassey"


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