how exactly does this test bench work? would i have to build the box to specification first, then install the speakers without crossovers and hook it up to the active crossover? cuz they would need to be in a box in order to do testing, right? then i would have to uninstall the drivers, build the passive crossovers, and reinstall everything....is this what u are saying?
A bare bones setup would be;
Portable CD player [headphone jack output] -> DCX2496 -> amplifier of your
choosing.
A better setup would be;
Home CD player [or universal DVD player] -> AV receiver [for volume control] ->
DCX - amplifier.
Put these items on a table and that is your test bench.
Buy a driver and connected it directly to the amplifier. If the driver is a tweeter
or midrnage, just leave it there sitting on the table. If you want to test bass
performance, make a test box for the midwoofer or woofers. If you want to hear
the high frequency performance, you don't really need a box. You could make
a box too to mimick a more realistic scneario.
Verify the DCX setttings for the particular driver [ie, connect the high pass output to the amp for tweeters, connect the midrange output for midrange, or connect the bass output for woofers.
Turn on the system and listen to familiar music. Prop up the driver [if it's not
in a box] to hear it on axis far away, up close, whatever. Change DCX settings
to hear what happens to the sound.
/easy
For tweeters, determine what might be a good crossover starting point
and use a 24dB slope, lets say start at 2khz. Skew the crossover higher,
as high as you want to hear what happens. But don't go too low as you
might damage the tweeters, it's a judgement call. To protect tweeters from
excess power insert an inline AGC 1A fuse. Select different filter types and slopes and sweep the frequency range to understand what sound you
are getting from each scenario. Think of it as a blind date.
For midranges or midwoofers, the audition is more complex as there are
more scenarios to try out. You should do a battery of listening tests to
determine what the driver can and can't do for you. Think of it as a second
blind date to determine how many holes are accessible //content.invisioncic.com/y282845/emoticons/veryhappy.gif.fec4fed33b4a1279cf10bdd45a039dae.gif
For example, a midrange driver in a normal design will have two crossovers,
a high pass and a low pass. The high pass cuts out of the bass, the low pass
cuts out the treble, it's essentially a band-pass crossover. If it's a midwoofer
the bandpass may be 80hz - 2khz. This is a generic region. If you use a pure
midrnage the region might be 300hz - 2khz as pure midrange drivers offer no
bass so you need to filter out the bass by raising the crossover point otherwise
you can damage the driver with over-excursion.
So.. you have this midwoofer or midranges on the table with no box, playing
in some bandpass frequency range. First thing you notice is there is no bass
because the driver is free air. Don't worry about it, ignore it. Focus on midrange
sound quality only. Off axis, on axis, different SPL levels, different crossover frequencies/slopes. Ignore the fact that there is no tweeters or woofers playing
and thing about how natural the voices sound and instruments.
To make the test more interesting, disable the low pass section of the crossover
so the midrange plays 'wide open' on the top end, meaning you aren't crossing
out the treble. Listen for the nasty breakup modes and how they annoy you
OR not. If your crossover is flexible, you can just raise the crossover point from
... lets say 2khz to 20khz and this will mimick not using a low pass. The DCX
allows this.
Later, you want to test the bass performance of your midrange so you make a
test box, sealed, ported, whatever. Put the midrange in the box and change
the high pass crossover setting. You can set it very low, like 20hz to mimick
no high pass crossover to see what the driver does as you raise power. Most likely the bass will cause cone over-excursion which will damage the driver.
Raise the 20hz setting higher in increments until you think it sounds good
and has less excursion that raises it's power handling.
At the same time, try tweaking the low pass crossover to check how the driver
sounds in a box vs. free air or open baffle.
For woofers, you need a test box and all you do is change the low pass
setting.
Tweeters are easy,
midranges are easy too but will require a test box if you want to listen to it's
bass performance.
Woofers need a test box otherwise the audition is invalid.
Listen to 20 different tweeters, midranges, and woofers, spend a few months
everyday doing this and eventually you can mix and match combinations
of drivers based on your auditioning memory.
The ideal scenario is to find drivers that have less problems 'out of the box' so you DON'T have
to EQ them as it makes your job is integrating them easier.
