Kyle wrote:
> Hi all-
>
> This is semi-OT; I'm working up a 'system' for my Buick.
>
> I've got a Profile 3channel amp, 2x75w + 1x150w (all RMS)
> for the back. This will be running a 12" sub (80hz low
> pass) and a pair of 6x9's (120hz high pass, optional).
What model Buick? What type of sub enclosure? How is the sub coupled
to the interior? A grille? Through the back seat? If you haven't
bought the subwoofer, in many cases a 10" speaker works best. As a
rule, they require a much smaller enclosure.
> My question relates to the quality and specs of 6x9's I
> need; The amp puts out 2x75 RMS, 2x150 peak, at four ohms.
I don't particularly like 6x9's. I use them behind the seats in my
Roadster, but they are woofers and not full range type. They are
limited to 80 - 400 Hz. I admit I haven't shopped for 6x9's recently,
so there could be improvements.
> Most 6x9's I've seen range from 40-60watts RMS; 100-200-
> 300 maximum watt ratings. Frequency response varies from
> 20hz-20K to 40hz-38K and everything in between.
Keep in mind that car audio specs are often "wishful thinking." There
is NO WAY a 6x9 will ever put out 20 Hz at any volume level, even in a
car (do you understand "transfer function?" The smaller the listening
area, the easier it is to reproduce bass).
> As the sub is going to pick up the low stuff, I was planning
> to cross the 6x9's over at 120hz.
It is a good idea to use a crossover mid woofers, or at least bass
blocking capacitors.
> Now, if I do that, the
> lion's share of the power (which AFAIK comes from the low
> frequencies), will not be passed on to the speakers; which
> would lower my power handling requirement from the 6x9's.
>
> Right?
Kind of. In practice, it takes more power to get bass response and you
do use the most power at the low frequencies. But if you have a 120 Hz
crossover on the 6x9's they are going to see full power above that point
(and partial power below it).
It all depends on the efficiency of the speakers, the type of music you
listen to, and how loud you like it. Your mid woofers may still see
plenty of power above 120 Hz.
A note on 6x9's. IMHO, there are many 6" or 5 1/4" that will sound
better. Consider using woofers in the back deck with separate
tweeters. High frequencies are very directional. If the tweeters are
in the 6x9, all they will do is fire up. If it hits the back window,
you will hear some highs, but that isn't the best way to do it. If the
highs don't bounce of the window, it will sound worse yet. The same
goes for front speakers mounted in the doors. If the tweeters are
firing at your legs, it won't sound good. They make tweeters in angled
small enclosures that can be aimed towards the listener's ears.
Even "cheap" tweeters ($50/pair and under) will sound much better than
two way or three way 6x9's and whatever you are considering for front
speakers.
> If that's the case, and I don't use the 6x9's for bass,
> then I figger a decent set (~$90-100) would be plenty to
> do the mids and highs. Sound okay? (that's sony, pioneer,
> kenwood, etc.) (and if I put nice seperates up front, I'll
> get most of the highs from them, meaning the 6x9's are just
> for volume and basic full range fill.)
So many variables.... Don't make the mistake of figuring that you can
skimp on front speakers and rely on the rear for mid bass. Try to put
decent mid woofers in front, also. Something that will reproduce mid
bass as well. That usual means trying to fit something bigger than 4".
Otherwise, it will end up sounding thin in front.
> However, I don't HAVE to crossover the 6x9's, and who
> knows, it might work out well to have them do full-range
> sound. So maybe the 6x9's need to be able to handle the
> full 75 RMS and have good low-frequency response. That
> puts me in $150 territory, which is fine; but I'm trying
> to stay as inexpensive as possible. (that's infiniti and
> polk as near as I can tell)
First of all, whatever you use in back for midbass, use either the
crossover, or at least a 6dB/octave capacitor as a bass blocker. It
makes no sense to send the sub frequencies to these speakers. It won't
sound good, and will just bounce the cones around, cause distortion, and
maybe damage the mid woofers.
I'd recommend going with the largest round speaker that will fit, and
not a 6x9. They just sound better. I use 6" Morel speakers for mid
bass (4 ohm MW-166, I think, expect to pay around $80 each w/o grills).
They are inefficient (need lots of power), but the handle tons of power
(3" voice coils) and sound great in tight enclosures (easily reproduce
bass to 80 Hz). They make a similar 5" woofer that works well in
doors. These speakers really like lots of power, however.
The biggest reason to compromise by using 6x9's is ease of
installation. The speakers I mention above really need an enclosure
behind them. You can find 6x9 woofers that will work okay as "free air
woofers" (no need to box in the back of the speaker).
If you are not using separate amps for the front, you must be sure that
your amp is 2 ohm stable and DON'T forget to consider the sensitivity of
the front vs. back speakers! If they are running in parallel, you don't
want to mix real efficient speakers with inefficient speakers. Some
speakers sound twice as loud as others with the same amount of power
going in. You don't want a big mismatch.
As it happens, I just got a catalog from Parts Express yesterday. With
five minutes of my nose in the catalog, here's an example of what you
can do on a budget:
Rear speakers:
Pyle Millennium PLM65 6.5" aluminum cone midbass woofers: $60/pr.
Pyle Millennium PLMT separate tweeters: $40/pr
Front speakers:
Pyle Millennium PML55 5.25" midbass: $45/pr (make sure they will fit)
Tweeters, same as above: $40/pr
Profile 3-Way Electronic Crossover QX10: $50
Profile 100SX amp for tweeters, 70W RMS into 2 ohms: $80
Your existing Profile amp.
Your existing subwoofer (if you haven't bought one yet, consider 10").
Total, $315, plus shipping, no tax. If you haven't bought your
subwoofer yet, you'll be close to $400. But consider what you get! A
separate 3-way electronic crossover with 150W feeding your sub, SEPARATE
woofers in front in back using your amp, SEPARATE tweeters with their
own new amp (your existing amp will now only be powering the mid
woofers). You will have a "high end" type of system on a budget. Try
walking into a car stereo shop and telling them the basics of this
system without brand names. They will be talking around $2k range.
Caveat: I haven't heard these model speakers, but Pyles are usually
decent. If you can demo them, you might want to consider this setup.
A note on your subwoofer: If you can get a 10", or even an 8", to mount
on your rear deck, that might be the way to go. If you listen to rap,
or the new quasi rap/rock with tons of thump, you may need a separate
enclosure. But, depending on your tastes, you can get surprising
response with a JBL 8" or 10" sub mounted "free air" style to your rear
deck. It is MUCH more efficient, since you don't have to blast through
the back seat! The better coupling between the sub and the interior,
the less the demand on power and the less annoying thump and rattles to
others as you roll down the road.
I use an 8" JBL sub in my roadster, and I have measured decent response
below 40 Hz, even with the top down. I'm sure I paid well under $100
for the speaker, I'm not talking Pro Sound JBL, just the standard car
audio stuff.
If you don't feel competent to do the installation, every major city has
independent installers who will put your stuff in. Don't feel like you
have to buy it from a shop because you can't install.
> Not a lot of room for that much 'stuff' in a roadster,
> but maybe someone has some experience with other cars to
> fall back on?
I did my roadster YEARS ago. It has: 8" JBL sub through the trunk wall
(had professionally installed), separate amp and crossover. Two 6x9
woofers in boxes behind the seats. Two 4" mids and two dome tweeters in
tiny aluminum enclosures on the side kick panels up front. I use a
portable CD player as a head unit, into a "passive" equalizer.
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