Standard 91 radio and new hr speakers

Archives of Posts to the NZ MX5 List back in 2004
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Bill Rehm

Standard 91 radio and new hr speakers

Post by Bill Rehm » Sun Dec 19, 2004 11:46 am

My new headrest speakers are 4ohm and after reading some past posts on
the list I'm wondering:

How do I know what the original radio/cd/cassette radio puts out and how
the current original headrest speakers are wired (parallel or series).

What do I do now??


Regards
Bill

zorruno
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Standard 91 radio and new hr speakers

Post by zorruno » Sun Dec 19, 2004 12:27 pm

Bill Rehm wrote:
My new headrest speakers are 4ohm and after reading some past posts
on the list Im wondering:

How do I know what the original radio/cd/cassette radio puts out
Hi Bill, It is not so much what the head unit puts out, but what the
minimum impedance the head unit will sustain without distorting the
sound, or over driving the outputs. Generally you can present higher
impedance to the unit than standard, but lower may or may not give problems.

and how the current original headrest speakers are wired (parallel or
series).
Here's the factory diagram if it helps
(might not be at this link permanently)
http://www.mx5club.org.nz/downloads/spe ... diag_2.gif

There are a number of previous (and some quite recent) posts on this.
Also I think the latest topdown mag has info on this and some more next
issue.

http://www.google.co.nz/search?q=headre ... lub.org.nz

Here is an old one I posted in 2001 (I may have had a few changes of
opinion since then though...)
http://www.mx5club.org.nz/emaillists/nz ... g00107.sht

You can measure the impedance (in ohms) with a multimeter (it will
measure resistance, but for your purposes they are the same) from the
head unit end, looking back at the speakers - but obviously you'll need
the head unit out, and it sounds like you aren't going that far. This
is the only way to really check though.

I'm pretty sure the originals are 8Ohm - which will mean replacing them
1 for 1 with 4Ohm units will give a 2Ohm load per channel, but I've
never had headrest speakers and don't like 'em so I have never checked
personally.

So... It might be OK just replacing the speakers exactly how they were,
but you might get better results rewiring it for a 8 Ohm total load at
each input (two in series rather than parallel is one way of doing
this). It will be a bit hard wiring 4 4Ohm speakers to present 2 4Ohm
loads without $$ on impedance matching gear.

Anyone else replaced theirs with 4Ohm units driven by a factory
head unit and no rewiring?

There seems to be no consistency with polarity either, so whilst you are
in there, it is a good time to make sure they are wired around the right
way.

What do I do now??
Get the screwdrivers out? ;)

Cheers
zorruno

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Subject: Re: Standard 91 radio and new hr speakers
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There should be a sticker/stamp on the OE ones which specify 8 ohm or
4 ohm. Having said that I'd just plug the new ones in and not worry
about it too much. I expect you';ll have the level FADE'd down enough
that overheating/current won't be an issue. JMHO.


On Sun, 19 Dec 2004 11:46:52 +1300, Bill Rehm <bill@kase.co.nz> wrote:
[...]
(z)

Bill Rehm

Standard 91 radio and new hr speakers

Post by Bill Rehm » Sun Dec 19, 2004 12:57 pm

Thanks zorruno. Some of the links you mentioned I had checked out earlier
-- that's what precipitated my "mental block" as physics and electrical
engineering were not my "long suits" in university, thus all this
wiring/ohms, etc stuff is so above my head.

I would love to replace my head unit as a Xmas present to myself and
then just let "an installer do it", but then I have this empty space
problem where no one seems to know where to get a radio cubby pocket
quickly :(

I feel like I'm between a rock and a hard place i.e. a bit frustrated!

Regards
Bill

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