Hey... I just bought a $20 12" sub 700 watt on sale. Its kind of a
cheap one but that doesnt bother me. Hooked to my computer i have a 6
(5.1 same dif) channel Kenwood Amp, thats about 200 watt per channel
and i do have a 5.1 channel sound card. All ive been mising is a sub.
I know that there is no way it'll blow but my question is should i
keep this one or get the 15" 1000 watt version for the same price, as
well as does my amp have enough power to make the 15" sound decent or
even the 12" one. This is kind of a crossover question so any help
would be apreciated. My final question has do i buy a car sub box, or
do i make my own, but more importantly do i aim the woofer out into
the room or do i aim it at the floor.

Thanks in advance for any help!

"Qwerty" wrote in message
m...
Hey... I just bought a $20 12" sub 700 watt on sale. Its kind of a
cheap one but that doesnt bother me. Hooked to my computer i have a 6
(5.1 same dif) channel Kenwood Amp, thats about 200 watt per channel
and i do have a 5.1 channel sound card. All ive been mising is a sub.
I know that there is no way it'll blow but my question is should i
keep this one or get the 15" 1000 watt version for the same price, as
well as does my amp have enough power to make the 15" sound decent or
even the 12" one. This is kind of a crossover question so any help
would be apreciated. My final question has do i buy a car sub box, or
do i make my own, but more importantly do i aim the woofer out into
the room or do i aim it at the floor.

Thanks in advance for any help!

I doubt that $20 sub can handle anything near 700 watts let alone 70.
Automotive audio gear is often very overly rated by deceptive manufactures.

Also be aware of the impedance of the speaker. Some car audio gear is rated
4 Ohms. Most consumer home audio gear may not handle a 4 Ohm load properly.

John

In article ,
(Qwerty) wrote:

Hey... I just bought a $20 12" sub 700 watt on sale. Its kind of a
cheap one but that doesnt bother me. Hooked to my computer i have a 6
(5.1 same dif) channel Kenwood Amp, thats about 200 watt per channel
and i do have a 5.1 channel sound card. All ive been mising is a sub.
I know that there is no way it'll blow but my question is should i
keep this one or get the 15" 1000 watt version for the same price, as
well as does my amp have enough power to make the 15" sound decent or
even the 12" one. This is kind of a crossover question so any help
would be apreciated. My final question has do i buy a car sub box, or
do i make my own, but more importantly do i aim the woofer out into
the room or do i aim it at the floor.

Thanks in advance for any help!

$20 subs are usually very inefficient and improperly rated. Rust-bucket
autoparts stores sell them at those prices every day.

You'll need to get the speaker's parameters before you can build a
proper box. Building a box takes some effort so I'd start out using a
subwoofer of a known quality.

Speaking of improperly rated, I doubt your Kenwood is 200W. Kenwood
outright lies when it comes to power ratings. The fine print probably
states 200W per channel using two channels, which will still be
extremely optimistic.

I supose i should have been a bit more thurough, assuming kenwood isnt
lying to me it is 125 watt rms per channel as i just discoverd from
their web site this morning. Its an older amp but it is still a
pretty decent one (KM-Z1 model). The sub has two voice coils so
rather than witre them as two channels i was gonna put them in series
to get it from 4 to 8 ohms as the amp requires 6 or 8. Yeah the sub
really isnt the greatest but i got it with a bunch of rebates and
other offers, it was originally around $90 which still ist great but
it is going into a dorm room which means im in school with a very
small budget so the price was right. But now only one question
remains, what type of box? Sealed, ported, or band pass and how
precise do i have to be because im not that great at getting all the
variables to do those proper calculations. If i kinda just guess and
make it about the right size and make a hole for a port based of
dimensions i took from boxes i measured in stores will i destroy the
sound or would it be something only a true audiophile would notice?

Sorry im a bit of a newbie but i like to try and do everything myself
and learn as i go.

Thanks!
-Qwerty

"Qwerty" wrote in message
m...
I supose i should have been a bit more thurough, assuming kenwood isnt
lying to me it is 125 watt rms per channel as i just discoverd from
their web site this morning. Its an older amp but it is still a
pretty decent one (KM-Z1 model). The sub has two voice coils so
rather than witre them as two channels i was gonna put them in series
to get it from 4 to 8 ohms as the amp requires 6 or 8. Yeah the sub
really isnt the greatest but i got it with a bunch of rebates and
other offers, it was originally around $90 which still ist great but
it is going into a dorm room which means im in school with a very
small budget so the price was right. But now only one question
remains, what type of box? Sealed, ported, or band pass and how
precise do i have to be because im not that great at getting all the
variables to do those proper calculations. If i kinda just guess and
make it about the right size and make a hole for a port based of
dimensions i took from boxes i measured in stores will i destroy the
sound or would it be something only a true audiophile would notice?

Sorry im a bit of a newbie but i like to try and do everything myself
and learn as i go.

Thanks!
-Qwerty

If I was in your position, this is what I would do: I'd go with the 15"
subs
since they are the same price. If they turn out to sound God-awful, get
some other 15" speakers somewhere else (ebay?). Your Kenwood
should be able to drive them just fine (8 ohm) unless they have the worst
efficiency known to man. I'd build the sub boxes myself, speakers pointed
out, bass reflex design. (And cover the speaker with something to protect
it...
an exposed speaker WILL get dammaged in a dorm room environment - count on
it!)
In general for the sub boxes, bigger is better up to a point. I doubt you
will hit that
point due to the fact that they are going into a dorm room. Make them as
big
as you can (comfortably) and make it so you can adjust the port size
somehow.
This could be as complicated as a sliding panel (careful here...it can't
vibrate), or
as easy as a bunch of same size boards with different size cutouts that can
bolt/screw
onto the cab one at a time (not real pretty, but functional). Once in your
room, you
can "tune" the sub boxes to what sounds best to you. Good Luck!

In article ,
(Qwerty) wrote:

I supose i should have been a bit more thurough, assuming kenwood isnt
lying to me it is 125 watt rms per channel as i just discoverd from
their web site this morning. Its an older amp but it is still a
pretty decent one (KM-Z1 model). The sub has two voice coils so
rather than witre them as two channels i was gonna put them in series
to get it from 4 to 8 ohms as the amp requires 6 or 8. Yeah the sub
really isnt the greatest but i got it with a bunch of rebates and
other offers, it was originally around $90 which still ist great but
it is going into a dorm room which means im in school with a very
small budget so the price was right. But now only one question
remains, what type of box? Sealed, ported, or band pass and how
precise do i have to be because im not that great at getting all the
variables to do those proper calculations. If i kinda just guess and
make it about the right size and make a hole for a port based of
dimensions i took from boxes i measured in stores will i destroy the
sound or would it be something only a true audiophile would notice?

Sorry im a bit of a newbie but i like to try and do everything myself
and learn as i go.

Thanks!
-Qwerty

It's going to be tough to guess which box. Wire up your Kenwood to the
sub while it's not in any enclosure. Put on some bass heavy music and
crank it as loud as it goes.

If there's too much cone excursion (distorts), you'll want a ported
enclosure to load it down more. Try 4 cubic feet and a 4 inch wide
port. Adjust the port length to adjust the resonance.

If there's not much cone excursion, it's probably made for a small
sealed box. The efficiency is limited by the speaker so the enclosure
size won't matter a lot.

Anything in between is a grey area.

Don't build a bandpass. You'll never get that tuned right.

Kevin McMurtrie wrote:

If there's too much cone excursion (distorts), you'll want a ported
enclosure to load it down more.

Uh ?

Ported enclosures allow larger cone excursion than sealed ones !

Ported enclosures do *not* "load it down more" , whatever that piece of
psuedo-science you meant by that !


Graham

In article ,
Pooh Bear wrote:

Kevin McMurtrie wrote:

If there's too much cone excursion (distorts), you'll want a ported
enclosure to load it down more.

Uh ?

Ported enclosures allow larger cone excursion than sealed ones !

Ported enclosures do *not* "load it down more" , whatever that piece of
psuedo-science you meant by that !


Graham

Resonance from a ported box loads down the speaker. When tuned
correctly, it does greatly reduce cone excursion.

If you tune a ported box incorrectly, then yes, it does cause more
excursion. Grossly bad tuning is not much different from running the
speaker in open air. Fortunately it's easy to tune a ported box by
hacking off the inside end of the port off until resonance is correct.

A sealed box can be used to control excursion too. The problem is that
the poster doesn't know the speaker's parameters. Tuning by trial and
error would be extremely difficult so he'd just have to live with the
size being wrong.

Kevin McMurtrie wrote:

In article ,
Pooh Bear wrote:

Kevin McMurtrie wrote:

If there's too much cone excursion (distorts), you'll want a ported
enclosure to load it down more.

Uh ?

Ported enclosures allow larger cone excursion than sealed ones !

Ported enclosures do *not* "load it down more" , whatever that piece of
psuedo-science you meant by that !


Graham

Resonance from a ported box loads down the speaker. When tuned
correctly, it does greatly reduce cone excursion.

The port only works at / around the port tuned frequency.

Significantly below the port frequency it acts like a hole in the cabinet and
LF excursion will be greater than IB equivalent.

Since LF (over)excursion can cause damage, I thought it worth posting.


If you tune a ported box incorrectly, then yes, it does cause more
excursion. Grossly bad tuning is not much different from running the
speaker in open air. Fortunately it's easy to tune a ported box by
hacking off the inside end of the port off until resonance is correct.

A sealed box can be used to control excursion too. The problem is that
the poster doesn't know the speaker's parameters. Tuning by trial and
error would be extremely difficult so he'd just have to live with the
size being wrong.

Errr - yes - that's seems like an argument in favour of avoiding porting when
the speaker specs are unknown.


Graham