Re: Anyone else bi-amping?

"bear" <bearlabs@[EMAIL PROTECTED]
> wrote in message 
news:fqc0ig01jv6@[EMAIL PROTECTED]
> jamesgangnc wrote:
>> I updated my setup to bi-amp last year.  I was wondering if any others
>> in the group is doing this now and what your set up and experiences
>> were?
>>
>> I'm using a dbx 223 crossover usually at 700hz.  I play around with it
>> a bit but keep it between 500 and 1k.  The lower end I'm running to an
>> adcom 555 connected to 4 ten inch moderately priced woofers in closed
>> cabinets, two woofers to a side wired in parallel.  The high side I
>> have going to an adcom 535 with a pair of 5 1/4 midwoofers and one
>> ribbon tweeter on each side also in closed cabinets.  The passive
>> crossover on the high side is just a simple 6db centered at 5k.  Of
>> course it is subjective, but I feel like moving the bass out of the
>> rest of the signal improved overall clarity.  The two adcoms, when I
>> experimented with them independently also seemed better suited to the
>> separate tasks.  Besides the obvious power difference the 535 seemed
>> to have a better sound at mid and highs than the 555 when listening to
>> them with a full signal range at about the same sound levels.  Of
>> course the 555 is obviously the choice for the low end anyway due to
>> the power difference.
>>
>> For a signal source I'm using a technics sh-ac500d as a preamp and
>> either xm radio or itunes acc ripped at 256k via a squeezebox.  The
>> setup doubles as part of my surround sound as well hence the ac500d.
>> I mostly listen to old and new rock but occasionally anything else as
>> well, except country.  I'd like to take some measurements as well.
>> I've got a signal generator and a scope but don't have a good high
>> quality mic.
>>
>> As I suspect most of us are, I'm trying to decide what to change next
>> as well :-)
>
> I'd get a higher order filter on your ribbons first.
>
> The distortion increases in typical ribbons when the excursion below the
> useful rolloff does not decrease substantially. A first order filter in
> practical terms tends to make the excursion *remain the same* below the
> inflection point of the "rolloff". That means that you've got excess
> deflection/excursion. I'd consider a 24db/oct filter there... most
ribbons
> can not handle a first order filter.
>
> Then use one of the various freeware FFT programs and a halfway decent
> mic to measure the freq response of the mid/HF combo. Take note of the
> off axis response and the waterfall as well. Look at the impulse
> response of the two drivers together.
>
> You may need to adjust the xovers and do other things to arrive at a
> best compromise response for the mid/tweeter combo.
>
> Then you can look at the relation****p between the woofs and the upper 
> range.
>
> After that I'd say that with the "average" sort of ripped music, it
> probably won't make much difference what else you do. BUT, once you get
> the speakers optimized you may start to hear larger differences in terms
> of source material - then it may make sense to think about upgrading
other
> parts of your system.
>
> Btw, the difference you are now hearing is likely due to two things:
> - different amplifier & load to the amp
> - different crossover slope & Q
>
> Until then, enjoy the experimenting! :_)
>
>                 _-_-bear

Thanks.  Interesting.  The low end on the ribbons is around 2k so I was 
thinking that I would get way with the 6db crossover because I was so far 
above it.  Given that would you still recomend the 24db crossover or maybe
a 
12?  Some of what I have read on the topic suggested keeping the mid/high 
crossover simpler.  In all honesty I'd probably think a little bit about 
switching to a three way active to get a 24db crossover rather than using 
passive.

I'm clueless in the mic world.  But I would like to be able to really test

rather than rely on subjective listening. Can I hook the mic directly to
my 
scope or should I have a preamp on it?  I realize I will have to power the

mic if I do not have a pre-amp involved.  What mic brands tend to be
decent 
and what kind of dollar level should I be shopping at?  tia