On Mon, 3 Mar 2008 15:21:55 -0800, jamesgangnc wrote
(in article <fqi16j0aie@[EMAIL PROTECTED]
>):
> "Sonnova" <sonnova@[EMAIL PROTECTED]
> wrote in message
> news:fqegm601de9@[EMAIL PROTECTED]
>> On Sat, 1 Mar 2008 13:56:58 -0800, jamesgangnc wrote
>> (in article <fqcjfa02enj@[EMAIL PROTECTED]
>):
>>
>>> "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
>>
>> You can get a very nice condenser mike with a big 1-inch capsule and
very
>> flat frequency response that outputs directly to USB for less than
$100.
>> The
>> Samson C01U, for instance, is $89 from Zsounds and has 20-18KHz +/- 3db
>> frequency response. All you need with it is a USB cable, your computer
and
>> the freeware sound capture and editing program "Audacity" (available
for
>> Windows, MacOSX, Linux). Connect the Microphone to your computer via
USB,
>> start Audacity, set the preferences to the USB input, and start
capturing
>> audio, select a section and then then go into the "Analyze" menu and
>> select
>> "Plot Spectrum" It will even give you a cursor to look at any point on
the
>> plot.
>
> Does have a lot of sound editing capability. But what about measuring
level
> and frequency? How sensitive can it measure level? I see it does have
> multiple channels.
>
> It is different from what I was thinking, which was to hook one scope
> channel and the function generator to an rca input and the other scope
> channel plus an rms meter to the mic on a stand in front of one of the
> speakers and take readings voltage at points between 20 and 20k while
> observing the signals for distortion or phase ****ft on the scope. Not
that
> I'm against your suggestion, just didn't consider this path.
>
There are also real-time spectrum analysis tools available for most
computer
platforms, I merely used Audacity as an example of a free program. One can
also get oscilloscope programs and fast -fourier analysis programs. They
all
should work with a USB microphone, thank you.
|
