"Matt Ion" <soundy106@[EMAIL PROTECTED]
> wrote in message
news:fvsfhp$sju$1@[EMAIL PROTECTED]
> Neil Green wrote:
>
>>> The signal coming out of the deck is AC; the
>>> signal phase has to be the same in both speakers.
>>> There is no "right" or "wrong" polarity as such,
>>> they just have to be the same. A DC meter won't
>>> give you a meaningful reading.
>>
>> The AC bit is news to me, I was under the
>> impression that the current to the speakers was DC,
>> but as you can probably tell I'm more or less
>> ignorant in these matters.
>
> Not really... just a little n00bish. That's okay,
> it's always good to learn something new!
I try to do that at least once a day.
So far so good.
>
> If you feel inspired to understand it a little
> better, take a browse of http://www.bcae1.com
> ("Basic Car Audio Electronics"), specifically
> section 21 on "Audio Output".
Will do.
>
>> Anyway, the meter showed a minus sign one way and
>> not the other, and I connected the two speakers
>> accordingly.
>
> It's not unusual for an amplifier's output to have a
> slight DC offset, which is probably what you were
> measuring, but there's no guarantee it will be the
> same offset on both channels and thus not a valid
> indicator of phase.
Looks like we fluked it then.
1 in 4 chance I guess.
>
> (Hmm, it's strange there's not actually a section on
> "phase" on BCAE... it's a little crude, but there's
> a diagram and brief explanation at
>
http://www.classictruckshop.com/clubs/earlyburbs/projects/stereo/systems.htm
-
> scroll down to "speaker phase")
>
>>> That makes it a little easier then, because you
>>> can check the polarity of the connections to the
>>> deck, then confirm them at the speaker end. If you
>>> used the factory speaker wiring, just follow the
>>> wiring color codes and make sure the + and -
>>> outputs on the deck properly match the terminals
>>> on the speakers.
>>
>> My son actually had them written down (good boy!)
>> and they tallied with how we had the speakers wired
>> so it's all good as far as that goes.
>
> Excellent!
He's a good lad.
A chemist by profession, so very thorough and
everything gets documented.
>
>> The rear seats fold forward so there's nothing to
>> mount a sub on, and my son needs the folding seats
>> to stow golf clubs..
>
> Ah. Of course, folding the seats down also
> introduces the acoustic leakage problem we've been
> battling thus far, though hopefully not as severely.
> He'll have to remember that he'll probably see
> reduced bass output from the rear speakers with the
> seats down, and remember NOT to try to compensate by
> cranking the bass control.
>
>> OK, so we make up an MDF parcel shelf and kill a
>> little of the bass, that's OK.
>> The system sounds fine apart from the bass
>> distortion so I'll tell him to go easy.
>
> Turning down the bass control is the actual "fix"
> for the problem... the rest of the exercise is
> intended to improve the speakers' own bass response,
> so he doesn't NEED to turn up the knob.
>
>> Once again, thanks very much for your time and
>> patience.
>
> No worries!
The internet is indeed a wonderful place, people
willing to help just because they can.
I'm a carpenter by trade, and a year or so ago needed
to cut some radius rafters for an old fa****oned house.
The common rafters weren't a problem but the two hips
had me stumped so I left a message on a mathematics
newsgroup and had the answer within a day.
Emailed the guy some pictures of the finished article,
he was very happy to see a practical application for
his theoretical knowledge.
So thanks again, and if you need any advice on
building feel free to ask.
Neil.
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