I have a battery operated stereo amplifier (20 watts per channel). I'm
looking to build a woofer box (I guess the proper term would be subwoofer)
for stronger bass. I am thinking of using two 12" woofers in a ported box.
There would be a baffle inside so each driver has an independent chamber.
Each chamber will have sufficient volume for the driver, but not so large to
make the thing imobile. I hope to get a frequency range of 35-90 Hz. I'm not
looking for high accuracy bass, but it should not have serious peaks. I
suppose I have to give up some accuracy for SPL. I hope I can get at least
95 SPL 1w/1m. The speaker will have a cross over so I can connect the
satellites. The system will be for parties and home use.

My main question is: Is the ported box the way to go or should I be looking
at something else like band pass? I see those boxes the kiddies put in their
cars with the internal speakers and the plexiglas window. The box volume
looks small but maybe normal for bandpass design?

Thanks, John

JohnR66 wrote:

I have a battery operated stereo amplifier (20 watts per channel).
I'm looking to build a woofer box (I guess the proper term would
be subwoofer) for stronger bass. I am thinking of using two 12"
woofers in a ported box.

I would have thought you wanted it portable? - a pair of interesting 12"
woofers with high efficiency could end up on the heavy side of easy
portability in one box.

There would be a baffle inside so each driver has an independent
chamber.

The air space requirement is the same, I would prefer to let them share
the volume.

I hope to get a frequency range of 35-90 Hz. I'm not
looking for high accuracy bass, but it should not have
serious peaks. I suppose I have to give up some accuracy
for SPL. I hope I can get at least 95 SPL 1w/1m.
The speaker will have a cross over so I can connect the
satellites. The system will be for parties and home use.

This is not a good idea, you should get a powered sub, then the dual 20
watt amp will have a lot of mileage with a pair of say four Fostex 8"
units in column type boxes.

My main question is: Is the ported box the way to go

Bandpass reflex is the only type that meets your criteria. But you need
two of them, powered, to meet your acousic demands.

or should I be looking to something else like band pass?

I would look at 8 inch units of a suitable type in Voight horns to get a
20 watt amp to be able to do a good job at a party. That would be the
low tech approach to "fully horn loaded", and "fully horn loaded" is a
string of adjectives that go well with "battery powered".

I see those boxes the kiddies put in their cars with the
internal speakers and the plexiglas window. The box volume
looks small but maybe normal for bandpass design?

Small size is the virtue of bandpass designs. But it takes the acoustic
properties of car insides to get away with so small boxes .... you could
try a pair, but they will probably lack ooomp in open air. It is the
easiest solution, but I do not know whether it will be a usable one.

Thanks

It is also somewhat meaningless to define the subs without knowing what
the rest of the system is going to be, 95 dB at one watt and one meter
is also a demanding spec for the top boxes. Household type stuff is more
likely to end up around using 4 watts for that SPL.

It is probably a better question to ask whether there is something ready
made for the purpose on the market.

John


Kind regards & Seasons Greetings

Peter Larsen

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

"JohnR66" wrote in message
...
I have a battery operated stereo amplifier (20 watts per channel). I'm
looking to build a woofer box (I guess the proper term would be subwoofer)
for stronger bass. I am thinking of using two 12" woofers in a ported box.
There would be a baffle inside so each driver has an independent chamber.
Each chamber will have sufficient volume for the driver, but not so large
to
make the thing imobile. I hope to get a frequency range of 35-90 Hz. I'm
not
looking for high accuracy bass, but it should not have serious peaks. I
suppose I have to give up some accuracy for SPL. I hope I can get at least
95 SPL 1w/1m. The speaker will have a cross over so I can connect the
satellites. The system will be for parties and home use.

My main question is: Is the ported box the way to go or should I be
looking
at something else like band pass? I see those boxes the kiddies put in
their
cars with the internal speakers and the plexiglas window. The box volume
looks small but maybe normal for bandpass design?

Thanks, John


You could always get a pair of Bassmaxx B-Zero cabinets (107dB 1W1M) and
with 20 watts, you'll be able to slam 'em with 120dB from 35Hz on up to
125Hz. Only drawback is size and price.
Alternatively, a good pair of vented boxes with efficient drivers may do
okay. A pair of E-V EVX180Bs would give you more than the SPL you specified
and you can keep the box size down to 8 cu ft or smaller, depending on how
low you want to go. The 180B has excellent sensitivity in the bass frequency
range. A lot of drivers have similar sensitivity ratings, but they achieve
that at 1-2KHz, rather useless for bass. I've replaced a bunch of E-V 18Bs
and gained about 6-7 dB more sensitivity below 100Hz. They work
exceptionally well for the price.


--
Best Regards,

Mark A. Weiss, P.E.
www.mwcomms.com
-

Ahhh.....
I always love it when someone goes off the deep end....
Read the original post: battery operated... mobile..
though your choice is good for "no high accuracy bass, etc"
You are correct about drawbacks of size and price.... you should also
include a more relevant aspect, called "application".

(Sorry, a rant from a large-horn user)

wrote:
Ahhh.....
I always love it when someone goes off the deep end....
Read the original post: battery operated... mobile..
though your choice is good for "no high accuracy bass, etc"
You are correct about drawbacks of size and price.... you should also
include a more relevant aspect, called "application".

(Sorry, a rant from a large-horn user)

ROTFLMAO! Next thing he'll want to find a way to turn water into wine, LOL

CD

JohnR66 wrote:
I have a battery operated stereo amplifier (20 watts per channel). I'm
looking to build a woofer box (I guess the proper term would be subwoofer)
for stronger bass. I am thinking of using two 12" woofers in a ported box.
There would be a baffle inside so each driver has an independent chamber.
Each chamber will have sufficient volume for the driver, but not so large to
make the thing imobile. I hope to get a frequency range of 35-90 Hz. I'm not
looking for high accuracy bass, but it should not have serious peaks. I
suppose I have to give up some accuracy for SPL. I hope I can get at least
95 SPL 1w/1m. The speaker will have a cross over so I can connect the
satellites. The system will be for parties and home use.

You're never going to get any amount of bass out of a 20W/ch amp (unless
it's a high-current, 1-ohm-stable type car amp), so the whole question
is moot after that.

My main question is: Is the ported box the way to go or should I be looking
at something else like band pass? I see those boxes the kiddies put in their
cars with the internal speakers and the plexiglas window. The box volume
looks small but maybe normal for bandpass design?

Bandpass will probably give you the best response, although design
tolerances are a lot stricter than for standard sealed or ported
designs. With two drivers you could also look at an isobaric setup,
which will give you decent response out of a much smaller box (basically
get the same output as you would with a single driver, but in half the
volume).

rec.audio.car would probably be a better place to look for this sort of
info... but again, it's all moot without a lot more power.


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wrote in message
ups.com...
Ahhh.....
I always love it when someone goes off the deep end....
Read the original post: battery operated... mobile..
though your choice is good for "no high accuracy bass, etc"
You are correct about drawbacks of size and price.... you should also
include a more relevant aspect, called "application".

(Sorry, a rant from a large-horn user)


A little extreme, I know, but I wanted to make sure the OP has a FULL range
of choices presented. It IS practical to get real bass with less than 20W.
We run our system at -40dB below full output and at that level, we're doing
115dB+ (C-weighted) and that's well below 20 watts total power to all of our
drivers. Much above that and it starts "snowing" from pieces of the ceiling
falling down.

(That's my rant, as a former large-horn user.)

--
Best Regards,

Mark A. Weiss, P.E.
www.mwcomms.com
-

Hi Mark,

As a (still current) horn user, I would LOVE to see a system that would
do
115dB+ (C-weighted) plus 40dB as you advertise... (just from an audio
nut like me).
In a setting.... I would build them in a second! 155db, is, ummm,
rather loud....



Mark & Mary Ann Weiss wrote:
wrote in message
ups.com...
Ahhh.....
I always love it when someone goes off the deep end....
Read the original post: battery operated... mobile..
though your choice is good for "no high accuracy bass, etc"
You are correct about drawbacks of size and price.... you should also
include a more relevant aspect, called "application".

(Sorry, a rant from a large-horn user)


A little extreme, I know, but I wanted to make sure the OP has a FULL range
of choices presented. It IS practical to get real bass with less than 20W.
We run our system at -40dB below full output and at that level, we're doing
115dB+ (C-weighted) and that's well below 20 watts total power to all of our
drivers. Much above that and it starts "snowing" from pieces of the ceiling
falling down.

(That's my rant, as a former large-horn user.)

--
Best Regards,

Mark A. Weiss, P.E.
www.mwcomms.com
-

Hi Mark,

As a (still current) horn user, I would LOVE to see a system that would
do
115dB+ (C-weighted) plus 40dB as you advertise... (just from an audio
nut like me).
In a setting.... I would build them in a second! 155db, is, ummm,
rather loud....



Mark & Mary Ann Weiss wrote:
wrote in message
ups.com...
Ahhh.....
I always love it when someone goes off the deep end....
Read the original post: battery operated... mobile..
though your choice is good for "no high accuracy bass, etc"
You are correct about drawbacks of size and price.... you should also
include a more relevant aspect, called "application".

(Sorry, a rant from a large-horn user)


A little extreme, I know, but I wanted to make sure the OP has a FULL range
of choices presented. It IS practical to get real bass with less than 20W.
We run our system at -40dB below full output and at that level, we're doing
115dB+ (C-weighted) and that's well below 20 watts total power to all of our
drivers. Much above that and it starts "snowing" from pieces of the ceiling
falling down.

(That's my rant, as a former large-horn user.)

--
Best Regards,

Mark A. Weiss, P.E.
www.mwcomms.com
-