Fwd: Re: Headrest speakers...

Voodoo · Post by **Voodoo** » Tue Sep 21, 2004 12:22 pm

Try again...

Rex Johnston · Post by **Rex Johnston** » Tue Sep 21, 2004 9:17 pm

Voodoo wrote:

Bear in mind that a loudspeaker dissipates most of its heat by the
transfer of heat from the voicecoil into the magnet assembly, this is
usually able to get rid of quite a few watts... In any case it won't be
called on to dissipate continuous power as program material is dynamic
in nature. Peaks of a hundred watts may only mean an average power less
than 10. The limiting factor is the ability of the amplifier to deliver
clean unclipped program material.

Not for the RMS rating. A speaker rated at 35WRMS should be able to
handle a sinewave voltage of
sufficient magnitude to dissipate 35 W continuously (within its designed
passband yada yada yada...).

If you are looking at music dynamics, the factor is more than 2
magnitudes. Peaks of 100W are only 12dB
above 1W. Most music's dynamic range easily exceeds this.

For an inexpensive small driver the TangBand brand may be worth a look.
They have gathered quite a reputation amongst the DIY crowd for their 3"
full range drivers.

Yup. Another good option.

Have a look here. Better value than the Vifas. (and you know where those
Vifas will be made don't you?)

Denmark, like all the other Vifa/Scan Speak/Peerless units?

Biggest problem may be the 8 Ohm impedance, however, if the headrest
speakers wire the left units (in the respective seats) in parallel, and
the right the same, an 8 Ohm driver is a better choice.

In a 2 seater? I don't follow.

Cheers, Rex

poison · Post by **poison** » Tue Sep 21, 2004 9:34 pm

Re 8ohm and two seats.. I assume (and a good point it is too) he means as
there are effectively 4 rear speakers. With 4 ohm car speakers we are usually
stuck with the parallel 2ohm or series ohm options. Using some 8ohm speakers
in parallel gives us the 4ohm load on the amp.

Gazza

Rex Johnston · Post by **Rex Johnston** » Wed Sep 22, 2004 8:31 am

Jeff wrote:

err, Rex - do you realise Gary twiddles with high-end audio gear for a
living??

Who is Gary?

How does one make a living doing 'twiddles'?

Cheers, Rex (Ex Senior Design Engineer - Tait Electronics (who make his
fair share of mistakes))

EricW · Post by **EricW** » Thu Sep 23, 2004 7:57 am

Don't you just love the English language!, Twenty emails, and I didn't
understand a single word of any of them!

Seriously, it is good to see that we have this level of expertise on the
list.

Eric

Simon Lord · Post by **Simon Lord** » Thu Sep 23, 2004 2:38 pm

As I understand it, two watts = one amp, four amps = one volt and so on.
Green is live because living things are green and brown is earth because, as
we all know, earth is brown. The blue wire is the one you dip in the water.
Or is my O-Level physics now out of date?

Seriously, I agree with Eric that the level of expertise others have and
share is great. What I will be doing with my own lack of knowledge, however,
is asking if anyone knows of a good competent MX5 experienced professional
in the North Shore area who could fit a new CD/radio and install headrest
speakers and wiring for me (no headrest speakers at all at the moment). I
say MX5 experienced because my last encounter with an electrician 'who had
fitted loads of alarms to MX5's' resulted in the little light popping up
just where I want to rest my arm, which is a pain in the ... wrist.

Second question. Having just got back from Singapore (without finding a
rattan cane supplier, sorry guys) I notice that the biting point on my
clutch is very high. A friend who drove it (I suspect highly
enthusiastically) while I was away commented that he thought the clutch was
on its way out, but as I have done less than 45,000km that seems a bit odd.
Is the clutch adjustable, does anyone know? If so, any reconmmendations for
the North Shore?

Simon
97 SR Ltd

Voodoo · Post by **Voodoo** » Thu Sep 23, 2004 3:26 pm

Hi Rex,

You're right on the dynamic range as below, I was being cautious though, and
assuming the possibility of the sort of sound that often comes from car audio
systems... compressed and loud...

It would be interesting to measure the actual current and voltage taken by the
speakers in such a system.

Gary

On Tue, 21 Sep 2004 21:17:40 +1200, Rex Johnston wrote:

If you are looking at music dynamics, the factor is more than 2
magnitudes. Peaks of 100W are only 12dB
above 1W. Most music's dynamic range easily exceeds this.

Voodoo · Post by **Voodoo** » Thu Sep 23, 2004 3:27 pm

Ahh.. Tait. I started out my electronics life working for AWA. In those days
they were Tait's prime competitor. I did a bit of work on VHF receivers...

On Wed, 22 Sep 2004 08:31:04 +1200, Rex Johnston wrote:

Jeff wrote:

err, Rex - do you realise Gary twiddles with high-end audio gear for a
living??

Who is Gary?

How does one make a living doing 'twiddles'?

Cheers, Rex (Ex Senior Design Engineer - Tait Electronics (who make his
fair share of mistakes))

Voodoo · Post by **Voodoo** » Thu Sep 23, 2004 3:28 pm

Jeff,

How do you get to be a whole year ahead of the rest of us?

Gary

On Tue, 20 Sep 2005 23:13:10 +1200, Jeff wrote:

err, Rex - do you realise Gary twiddles with high-end audio gear for a
living??

Rex Johnston · Post by **Rex Johnston** » Thu Sep 23, 2004 4:25 pm

Voodoo wrote:

How do you get to be a whole year ahead of the rest of us?

I wondered that myself. I guess he's been twiddling! <grin>

Cheers, Rex

Rex Johnston · Post by **Rex Johnston** » Thu Sep 23, 2004 4:40 pm

Voodoo wrote:

It would be interesting to measure the actual current and voltage
taken by the speakers in such a system.

Hmm - yes. I wonder what the actual available current from these head
units could be. They can't be simple
class B. Looking at the size of the heatsinks and the power ratings of
50+W times 4. Maybe they are some
sort of PWM switching design? Anyone know?

Tait? Yeah i worked mainly on the RNCs. Part of the trunking radio
networks.

Cheers, Rex

Grant · Post by **Grant** » Thu Sep 23, 2004 6:52 pm

And now some of us go out fixing the things (trunked radio systems)!
By the way, what does the I stand for with respect to current? Used it for
years but don't remember where the I comes from. Probably was taught it but
then that was in the late '60's when Tait gear had valves in it. Gosh, I
feel old!
Grant.

Rex Johnston · Post by **Rex Johnston** » Thu Sep 23, 2004 8:53 pm

The Simpsons wrote:

By the way, what does the I stand for with respect to current?

http://en.w*i*k*i*ped*i*a.org/w*i*k*i*/Electr*i*c_*current*

'60's when Tait gear had valves in it. Gosh, I feel old!

Grey hair? I know the feeling. I designed & built my first valve amp
over 20 years ago.
I've only updated it once since then, and that was to update the phase
splitter to include a
cc source in the tail.

Cheers, Rex

Grant · Post by **Grant** » Thu Sep 23, 2004 10:05 pm

The hair hasn't gone grey (yet) but the beard has. Becoming more
distinguished!
Thanks for the link. Never would have guessed it was from German, but it
does make sense now. I'm still using my transmission line speakers I built
in 1977. These two together would be almost as big as an MX5. There, that
get's it back on topic.

Grant.

Jeff · Post by **Jeff** » Thu Sep 23, 2004 11:22 pm

I'm s-p-e-c-i-a-l

??

EricW · Post by **EricW** » Fri Sep 24, 2004 8:41 am

Aah Tait Electronics,

Like you Rex, I spent a number of years working for Angus, in Auckland, with
Mike Gray, and have been competing against Tait, with Motorola, for years.
Funnily enough, my Grandfather worked with Angus in the RAF during the last
war.

Being on the sales side of the industry, I have always enjoyed hearing
technicians talk their own kind of English. I now understand most of it, I
just try not to let on!

There are a few of us radio guys on the list, maybe we are all chronic
"twiddlers" which is why we also like MX5s.

Regards

Eric

Rex Johnston · Post by **Rex Johnston** » Fri Sep 24, 2004 9:09 am

The Simpsons wrote:

The hair hasn't gone grey (yet) but the beard has. Becoming more
distinguished!
Thanks for the link. Never would have guessed it was from German, but
it does make sense now. I'm still using my transmission line speakers
I built in 1977. These two together would be almost as big as an MX5.
There, that get's it back on topic.

Heh. I couldn't take my first pair of transmission line speakers with
me when i shifted from Auckland down to Christchurch.
They were pretty big too, they wouldn't fit in (or on) the Mazda
(hatch). The cabinets ended up rotting underneath the house.

http://en.w*i*k*i*ped*i*a.org/w*i*k*i*/Electr*i*c_*current*

What happened to my URL? Is that what Mozilla calls converting to
plain-text, or did the list software munge it somehow?

Cheers, Rex

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