Alan Rutlidge wrote:
>
> "Iain Churches" <IainNG@[EMAIL PROTECTED]
> wrote in message
> news:10pEj.313053$3w2.14176@[EMAIL PROTECTED]
> >
> >
> > "TT" <TTencerNoSpAm@[EMAIL PROTECTED]
> wrote in message
> > news:13u337v2lp8n6ff@[EMAIL PROTECTED]
> >>
> >> "Iain Churches" <IainNG@[EMAIL PROTECTED]
> wrote in message
> >> news:zL9Ej.312731$HC6.104118@[EMAIL PROTECTED]
> >>>
> >>>> Is any of this going to be a problem?
> >>>
> >>> I make no rash promises at this early stage,
> >>
> >> Sigh....... Iain you won't make a hi-fi salesman if you keep that
> >> attitude up :-))
> >
> > :-))) I am much more interesting in seeing what
> > can be achieved in this special case, than making
> > a sale. There is no shortage of clients for high-quality
> > hand-built tube amps.
> >
> >> As you have become aware there are people doing slightly different
things
> >> in different parts of the World. Also note here
> >>
http://www.vaf.com.au/specifications.asp?audio=signature&grunt=s200r26719
> >> another Oz speaker manufacturer uses 3 Ohm impedance.
> >
> > No-one seems to be able to explain why some domestic
> > speakers are of such low impedance. One theory
> > is that manufacturers are pandering to audiophiles.
> > I am happy that Tannoy, B+W and JBL have not
> > departed from the straight and narrow. Tannoy can
> > still offer 16 Ohms as required.
>
> My Equinox Jupiters AFAIK use 4 x 8 ohm Audax bass units in parallel, 2
x Z?
> Audax midrange units and 1 x Z? Audax tweeter. The quoted Z is 2.5
ohms,
> but by how much and whare in the frequency range this occurs is probably
> only know to Rick Stadelmeier (the guy who designs and builds the
Jupiters).
> The bass and midrange units are from the Audax Aerogel range and the
tweeter
> is a fabric type (non-ferrofluid). Crossovers use custom handwound
aircored
> inductors. Not sure of the brand of the capacitors (probably Solen)
without
> getting out the screwdriver. I did have the model numbers of the
drivers
> recorded somewhere, but can't lay my hands on the bit of paper ATM.
> The cabinets are wired for tri-wire operation.
Rick's Jupiters need an amp which can do 2 ohms.
But as I have said before, you can match a well made tube amp to any
high load from
10,000 ohms right down to 0.1 ohm if you really want to.
But sensibly speaking, someone looking for something cheap to buy in the
shops
won't find many tube amps capable of handling 2 ohms
AT LOUD LEVELS. At very low levels below an average of 84dB SPL per
channel,
almost any amp will drive 2 ohms, but as soon as the level rises,
some amps will go poof all too easily, because 2 ohms is too close to
being a short circuit.
There is a very simple remedy though.
See Zero Impedance load matching transformers.
I have tested these and they have BW = 10Hz to 1MHz at high levels,
and have low winding losses and utterly negligible distortions.
Therefore it is possible to convert the 2.5 ohm Jupiter load to a load
of say
twice that or more than twice that at the amplifier.
http://www.enjoythemusic.com/magazine/equipment/0603/midmonth/zeroautoformer.htm
The great other benefit of these matching trannies is that the DF
improves
by the same amount as the Z ratio, so if the matching T
is set so its 7.5 to 2.5, and the Rout of the amp was 1ohm, typical
for a mediocre tube amp, then Rout becomes 0.33 ohms at the output
of the matching tranny.
90% of readers will not have understood what I just said.
Read it all again until you get it.
Studying transformer basics will help.
In the ancient "hi-fi" times of the late 1970s, the AR9 floor standers
with 2 x 11" woofers
in parallel and each being 4 ohms
gave a truly horridly low impedance character to drive, and these
speakers blew up
many amps.
I had a customer who bought a pair cheap which had rotted
surrounds on all 4 bass drivers.
I replaced all the bass surrounds and connected the bass in series, not
parallel.
I totally re-designed and rewired the rest of the circuit for the low
mids,
upper mids and HF tweeters using Peerless drivers.
Impedance was then about 6 ohms minimum, and any amp could drive them,
response was flat, and not horribly unflat like so many awful ****ing
1970s
brand new speakers.
The owner was delighted.
He didn't need something like the Zero Impedance trannies.
Price plus freight from the US isn't a song.
Now I am vaguely suggesting the Jupiters could be wired so
the drivers are in series rather than parallel, and many makers SCREAM
out
that the driver won't suit the box parameters and that one speaker's
impedance
is driving the others's so that the DF is ruined etc.
Its all BS.
If you have two identical drivers both sharing the same box volume
behind the cone,
then it makes no difference whether you have the 2 speakers in parallel
or series
with regard to the Fb and shape of the twin peaks of resonance with a
bass reflex design.
If ONE bass speaker fries or alters from the other, then sure, there is
an analomy,
but its safer for the amp to have the series connection.
However, with 2 series speakers, you need twice the applied voltage to
get the same SPL
as with 2 speakers in parallel.
Some makers paralleled bass speakers to lift bass performance with
respect to the mids and treble,
and since bass was so darn poor with ONE bass driver, they'd whack in a
pair in parallel, and presto,
very good bass levels, and this was loved by many listeners who prefer
too much bass rather
than a flat response, which comes across to them as too little bass.
Patrick Turner.
>
> >
> >> Also I am sure you
> >> are aware of Quad ESLs and there wildly ranging impedance curve as
well
> >
> > Yes indeed. They are one of the few that don't follow
> > IEC/EN/BS EN 60268-5
> >
> >
> >> ;-) Like a lot of manufacturers you probably need to be aware of what
> >> some
> >> people are likely to do with your gear and consequently take
precautions
> >> in design to ensure "the smoke stays inside the little bottles" :-))
> >
> > Indeed. But that's the easy bit:-)
>
> Yep, don't particularly want a Metaxas incident in my livingroom.:P LOL
>
> Cheers,
> Alan
>
> >
> >
> > Cheers
> > Iain
> >
> >
> >
> >
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