04 GT Sub install (finally)

In article <D4dTd.36460$s16.20556@trndny02>, JS > wrote:

> "CobraJet" > wrote in message
> ...
> > As general commentary on this topic, let me just say a couple things
> > that address some of the fallacies in audio.
>
> I agree with Joe. Great post. I'm not an expert, but an enthusiast and a
> bit of an electronics geek. I'm more into digital tinkering than analog
> though... I don't like math all that much. ;-) I design some small things,
> and understand basic AC theory.
>
> > First, using nominal handling wattage of a speaker to describe a
> > system is wrong. Speakers do not create wattage. The proper way to
> > describe power output of a system or part of a system is the RMS number
> > of the amp(s) driven into a static 4-ohm load at a low distortion level
> > (THD). "Peak" power or Japan industry figures are misleading and are
> > solely quoted to get consumers hyped (sounds like horsepower, yes?).
>
> Definately does. I've always tried to correct guys who spoke about how many
> watts their speakers could handle claiming that their system produced that
> amount of power. Then I see the Jensen amp, and just start laughing
> wholeheartedly.

Ah yes, Jensen. I started out in High School installing Lear Jet and
Craig 8-tracks with Jensen tri-axials. That rocked in '73.

>
> > Many amps claim to be 1 ohm stable. This is not to be confused with
> > being *accurate* with a 1 ohm load; it just means there is some kind of
> > circuit protection on board.
>
> And as noted on most spec sheets, THD is either measured at a load greater
> than 1 ohm static, or if they dare measure at that load, gets significantly
> worse on all but the best amps. My grandmother has a set of Carver Silver
> Seven-t home amps that will deal with a 1 ohm load, and I'm sure do just
> fine, but I don't want to know what my grandfather paid for them.

I have a pile of Carver stuff from my dad's estate. Great stuff.
Might even hook it all back up soon when I move into my other building.
I pity the neighbors.

>
> > The higher the impedance, the more control an amp has over the fore
> > and aft movement of the drivers. Picture pedaling downhill on your
> > bicycle. If you are in high gear, you can still move your legs against
> > the resistance and maintain stability. In low gear, you are windmilling
> > your legs like mad but can't keep up with the speed.
>
> Great analogy.

And murder on the crotch, too.

>
> > To an ear striving for accuracy, the "sacrifice" in power output
> > going from a 2 ohm to 4 ohm rated load is worth it. Not only will
> > distortion come in at a much higher volume level, but the amp(s) will
> > run cooler and last longer. Note that most home speakers are 8 ohm,
> > even though the power source is more stable than a car's.
>
> I tend to underdrive not only my speakers but my amps as well for the
> reasons of sound clarity and longevity. While this isn't always a
> guarantee, I understand, it helps. In the aforementioned system that I put
> in my old hatchback (which has carried over to a rice-rocket winter beater),
> the subs were hand-me-downs, cheap 12" MTXs at 4-ohm. The amp is a mono amp
> designed to run two 4-ohm speakers. The box is sealed. I don't like the
> sound of a bandpass. I'm not real sure about the benefits of a port hole,
> I've heard a sealed box produces tighter bass at a reduced level in sound,
> which I'm willing to accept.

Sealed boxes are great. My preference, with a good amp.
>
> > Going back to subs, let me yak about driver size. Big drivers have
> > been hyped over the years as necessary to achieve "big" bass. This is a
> > marketing ploy (and a damn successful one) that skirts the physics of
> > acoustic reproduction. In home systems, large drivers are employed for
> > their ability to create low frequency sound waves in large areas. In
> > cars, these low frequency waves have a length that exceeds the length
> > of the vehicle's interior. This is why you hear "better" bass outside
> > the car; inside what you are experiencing is air movement and some
> > representation of the upper harmonics of the sub bass tones.
>
> This makes sense, and I've heard some pretty impressive things come from
> relatively small drivers. On those Carver amps, my grandmother had a pair
> of Polk Audio towers. They made amazing bass, despite only having 6"
> drivers (albeit three of them) in a room that is quite soft by most
> standards. Because the room was this way, though, there were holes in the
> sound which I'm sure could have been tuned out.

Years ago, Harman Kardon had a speaker that incorporated three
7-inch (European size) bass drivers. I think it was the Citation
Eleven. It, too, was impressive.

>
> > What to do? Simple. Run multiple small drivers. Now you have more
> > total cone mass with the added bonus of more voice coils moving it
> > faster. Phased adjoining drivers will create waves that "melt
> > together". Such an array will go low and do it cleaner than big
> > drivers, which often give that muddy one-note boom (worsened by
> > band-pass boxes) that so many of us hate.
>
> I definately have problems with my 12s concerning big gaping holes,
> especially in the sub-bass and mid-bass regions. I don't have the cash to
> spring for a bunch of small drivers though. Can you explain the phasing a
> little better? Are you talking phase shifts of a degree or two to match the
> sound being produced by a speaker located farther from the ear, or is this
> something else?

Joe answered this already.

>
> > The trend towards huge drivers leaves an inherent hole in the
> > mid-bass. They cannot move fast enough to give crisp bass transients
> > and percussion that inhabit that 100 to 300-cycle area. The "fix" here
> > is to build a four-way system that uses smaller bass drivers for this
> > area (note that 5 or 6-inch bass drivers are built differently than the
> > same size midrange). This will help the overall problem, but you are
> > still left with lazy sub bass.
>
> I've only been able to cover up the mid-bass problem so much with the other
> speakers. The Eclipse's current situation is much like the one I described
> for my Mustang, only instead of 6 amplified coaxial channels, I have a 45x4
> (RMS) amp driving a pair of 3-way coaxial 5x7's in the rear and a set of
> components up front... 6" or so in the door near the ankle, and the dome
> tweeters mounted behind the mirrors. They're facing toward each other, but
> go farther toward imaging from what I can tell.
>
> > Some of my best sounding stuff used four 8-inchers in boxes that
> > were half the size of two 12's. In most instances, a single "quality"
> > driver is all that's needed. Money is better spent on a "quality" amp.
> > Unfortunately, too many people go for multiple cheap drivers and some
> > bargain amp with a big bogus rating. Then they brag about blowing up
> > the speakers with too much power, when in reality the amp clipped when
> > overtaxed and cooked the voice coil(s).
>
> Silly kids. The Clarion was bought to do the job it does. It doesn't have
> a huge inflated rating, and I know there are much better out there, but it
> does its job pretty well and doesn't pretend to be something it's not. I've
> never hurt it, even after using it at home with a power converter in my
> dusty house... with those same 12" subs. That whole setup's followed me for
> years...
>
> > The longer you listen to music at elevated sound levels, the more
> > you tax the battery and charging system. That is, if you commute a
> > distance, the voltage level in your battery may begin to drop if it
> > cannot keep up with the "total" draw, including A/C and headlights and
> > such. As voltage drops, the amp is more likely to clip (distort) and
> > damage your speakers, usually the smaller ones first. See on your amp
> > spec sheet that most are rated at 14.4 volts or thereabouts, which is
> > what the alternator is putting out while driving. As this dips down, so
> > does the ability of the amp to maintain spec. Big systems should have a
> > volt meter that is wired at the amp(s) so you can see what it/they are
> > getting fed.
>
> All good advice... that many seem to overlook.
>
> > Tuning the system for "flat" sound reproduction? I believe it's
> > another gimmick. The fact is that humans all hear differently and have
> > different preferences in *what* they hear. I have seen people pay for
> > acoustic flattening and hate the results. If the system is properly
> > designed to start with, then fiddling around with EQ settings in the
> > deck should suffice.
>
> I agree, however, many people tend to end up overdriving with the EQ and
> distort the preamp signal... which just spells disaster for the rest of the
> system. How many times have you seen a guy crank the bass all the way up on
> the EQ thinking he's wringing one more ounce out of an already uneven
> system?

All the time. People are bass crazy.
>
> I've always been under the impression that if you're going to tune with the
> EQ, tune down from flat, or at the most, tune only very slightly up.
> Setting the amps at max volume before clipping with the head at max (on a
> fully outboard-amplified system, that is) ensures the system is never taxed
> to the point of clipping only if the EQ settings aren't tweaked way up. I
> don't have a problem with tuning to taste either... but if it's done to the
> point that you're causing distortion at the signal's source, then there's an
> issue.

Good approach.

>
> > There is much more to all this, of course. I stay out of the sound
> > newsgroup because everyone is an expert even if they don't know WTH is
> > going on. All my observations come from experience. I hope this gives a
> > little insight to anyone building up a system.
>
> I'm curious to hear your ideas about staging and tweeter placement. I like
> sound loud, and clean, and even... but only know enough to be dangerous and
> impress only those who are mostly clueless. While I'm typically happy with
> the results, I know they could be better. I'm also curious about what sub
> arrangement I should put in my winter rice-rocket to match the rest of the
> system well. I'm considering designing a custom box/amp rack for the hatch
> area.

I'll get around to it. I was hashing it around in my head today,
trying to figure out putting something you sense into practical
terminology. Not easy.

BTW, my favorite reference CD remains to this day The Best of Stan
Ridgway, "Songs That Made This Country Great", released in '92. If the
name doesn't click, he was the lead man for Wall of Voodoo. Lots of
different track styles and instruments. The bass played by Louis Cabasa
on "Salesman" will readjust some attitudes on a good stereo. Worth
digging up a copy.


>
> JS
>
>

--
CobraJet
Thunder Snake #1

In article >, Joe
> wrote:

> CobraJet > wrote in news:240220052025349565%
> :
>
> > In article >, Joe
> > > wrote:
> >
> >> CobraJet > wrote in
> >> :
> >>
> >> > In article >, Joe
> >> > > wrote:
> >> >
> >> >> Outstanding post, CJ. As a musician, I can attest that all of
> this
> >> >> is true. Everything that applies to mobile stereo (except the
> >> >> 12-volt stuff) applies to guitar, bass, keyboard, and PA rigs as
> >> >> well. It's all valid sound theory.
> >> >
> >> > Glad you liked it. I think everyone else thinks I'm nuts.
> Quiet.
> >> > And
> >> > I didn't even get into stereo imaging or tweeter placement.
> >>
> >> Saving that for next week?
> >
> > Maybe.
>
> I'll look for it.
>
> >> >> Witness the Ampeg SVT bass guitar cabinet:
> >> >> http://www.ampeg.com/products.htm?product=28&catid=11
> >> >>
> >> >> Most bass guitar cabs use 12" or 15" speakers for depth, but
> lack
> >> >> punch especially in the midbass region. I used to play with a
> guy
> >> >> who used two SVT cabs on stage; his rig had both punch and
> depth.
> >> >>
> >> >> Before I ever heard the SVT, I seriously doubted whether the 10s
> >> >> would hold up to the low bass at high power. After he played
> for a
> >> >> few minutes, all doubts immediately disappeared.
> >> >
> >> > I see they use 30-oz magnets on their 10's. Most of my car
> stuff
> >> > ran
> >> > 60-oz for 8's and 75 for 10's. This is why, with a good amp, you
> >> > only need one sub. I like DVC's a lot.
> >>
> >> With 8 speakers, they can get away with using only 30-oz magnets
> per
> >> speaker. Anything more for that rig would be overkill.
> >
> > True. You guyses don't have to deal with a 70-db noise floor.
>
> On a live soundstage it's anything but. If you're pushing it,
> distortion from a rig like that probably reaches around 25% if not
> more. But that's what gives it the "edge".
>
> >> Also of note, that cab is split inside. The top 4 speakers are
> >> separated from the bottom 4.
> >
> > I'm gonna guess cutting down the refraction area keeps back waves
> > from coloring the sound. Just a guess.
>
> You're probably right about the back waves, but I don't think it's to
> prevent sound coloration. I think it's for efficiency. On a live
> rock soundstage, these guys are pushing over 110-120 dB easy. The
> band is louder than a jet plane taking off. Cabs like the SVT are
> designed to produce maximum SPL with a kick-ass tone at probably 50%
> or higher distortion levels. It's not uncommon to push a rig to that
> level of distortion during regular playing.

And one of the reasons I stay away from live performances. It just
doesn't make it for me. I can feel the damage =80

>
> Joe
> Calypso Green '93 5.0 LX AOD hatch with a few goodies
> Black '03 Dakota 5.9 R/T CC

--
CobraJet
Thunder Snake #1