you could if you bought a crossover do a sub and mid bass set up with your 18's and 12's
small room vs large room acoustics
- Thread starter IceBurghDJ
- Start date
i'm working on understanding specs and what they mean, or don't mean. Still don't understand 'half space' in the list of measurements...
http://www.electrovoice.com/product.php?id=2596 is the 18" sub.
http://www.electrovoice.com/product.php?id=1170 is the 12' sub.
Each have builtin crossovers - the 12" is not adjustable but the 18 is, my tops are as well I beleive. I also have an EQ that can be put inline to a sub to force it into the range i want.
http://www.electrovoice.com/product.php?id=2596 is the 18" sub.
http://www.electrovoice.com/product.php?id=1170 is the 12' sub.
Each have builtin crossovers - the 12" is not adjustable but the 18 is, my tops are as well I beleive. I also have an EQ that can be put inline to a sub to force it into the range i want.
Generally, fullspace (or freespace) is a measurement of the driver by itself suspended in the air. Half space is the boosted measurement the driver gets when in proximity to either the floor or a wall. Quarter space is the double boost a signal gets when coupled closely with a wall and floor.
Something is screwy with these measurements. The 12" sub has a peak at 107hz?? That's above it's crossover frequency of 100hz. Not even EV is that screwed up!
Careful - good way to blow a sub.
Probably not. Both crossovers and EQs are useful tools, but they are not interchangeable.
Crossovers have "slopes" that can be used in high/low pass filters. Anything steeper than -24dB/oct is sufficient to "force" a frequency range crossover between cabinets, or as a high/low pass.
EQ has an absolute boost/cut of a frequency - but some do have a special "minus infinity" setting that can be used. Most 31-band EQs operate with 8/16/24 dB ranges of boost/cut. BUT 1/3 octave away from the slider, the net effect is 0dB change.
The crossover BETWEEN cabinets or drivers is interesting. The highpass frequency that prevents content that is too LOW for a subwoofer is another element that is needed to protect the driver. It is common to exceed the Xlim (mechanical limit) of a driver with content that is too low.
I play a 75hz tone and watch the spectrum analyzer see tones around it, but not 75hz exactly.
So..is the tone not 75? Is there something in my signal path altering it? (just a mixer...but is neutral on the tone controls truly neutral?) Are the speakers coloring the tone? Is the room to blame? or the SA? (an app on my phone so I won't expect scientific accuracy).
now I play music and watch the results...now are the crossovers at issue? Since the tops can produce down to 100 (lopass set to 100, can try 120 also) maybe the tops are strong at the 107 freq? It's resonating in the room, reinforcing that point?
MANY variables - hence my tendency to test outside. But then I'll be playing in a room, SOME room. And when we test there we all test in an empty room - which is never empty when we're playing. So in reality we adjust by ear - the same way we choose speakers in the first place.
So..is the tone not 75? Is there something in my signal path altering it? (just a mixer...but is neutral on the tone controls truly neutral?) Are the speakers coloring the tone? Is the room to blame? or the SA? (an app on my phone so I won't expect scientific accuracy).
now I play music and watch the results...now are the crossovers at issue? Since the tops can produce down to 100 (lopass set to 100, can try 120 also) maybe the tops are strong at the 107 freq? It's resonating in the room, reinforcing that point?
MANY variables - hence my tendency to test outside. But then I'll be playing in a room, SOME room. And when we test there we all test in an empty room - which is never empty when we're playing. So in reality we adjust by ear - the same way we choose speakers in the first place.
What you are seeing, in a general sense is the inherent distortion associated with signal processing. The nature of the distortion depends a bit on the source of the distortion. In very broad terms....
Total Harmonic Distortion is part of the electronic noise that is added to the signal at each stage of the signal chain. The A/D and D/A converters are not "perfect," there is some cross talk between channels on a mixer, and so on. THD in each stage of the signal chain typically adds "uniform" noise to the final signal.
No physical woofer can "exactly" reproduce the input signal. Driver/cabinet combinations will produce distortion in the form of overtones of the test frequency. The overtones tend to be multiples of the test frequency.
Room modes will add constructive and destructive interference to the signal. These tend to be peaks and nulls in the final signal. Depending on the frequency, moving a measurement mic by as little as 1" can dramatically alter the signal >10kHz. There are some nice charts on this link that illustrate the magnitude of the issues that room modes can cause.
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I prefer to set the test tones at least 1/3 octave away from any high/low/crossover frequencies.
Setting a baseline outdoors, and tweaking in the room is the best practice.