"bear" <bearlabs@[EMAIL PROTECTED]
> wrote in message
news:fqi18a0aiv@[EMAIL PROTECTED]
> jamesgangnc wrote:
>> "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 relationship 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
>
> What Sonnova said...
>
> But you can get the Behringer "test" mic for $35 from most internet and
> retail
> places that sell it. Almost any mic will get you some good information,
> even if it is "relative" and not absolute.
>
> Any soundcard and any freeware - no scope - will tell you enough
> information
> to make good decisions.
>
> As far as the xover? I'd try to make an xover that gets things below 2k
> out of
> the way a bit faster... You're only about an octave down at 2.5k,
assuming
> you
> are really at the -3dB point at 5khz. 6dB down isn't all that much. So
the
> issue still remains.
>
> I doubt that you would get better fidelity, or put another way, reach
the
> full
> potential of a good ribbon tweeter using an electronic xover. Just my
> opinion.
>
> Also getting a mid up to 5khz. creates some problems in terms of
response
> and
> polar response...
>
> This is a good example of why speaker design is a complex problem with
> many
> variables, and many compromises...
>
> _-_-bear
I think you make another good point about the midbass. It's response
curve
goes to 6 but it not as flat between 5 and 6 and rolls off sharply at 6.
I
had choosen 5k because of the ribbon. Originally I was trying to make it
a
bit high to keep the vocals in the mids but your comments make me realize
that with a 6db crossover that's not happening anyway.
With a more effective crossover would you also recomend lowering the
crossover point as well?
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