Starting off with Micca MB42X, now amp + sub? - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 13 Old 05-02-16, 06:06 PM
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Re: Starting off with Micca MB42X, now amp + sub?

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lovinthehd wrote: View Post
FWIW many subs do not have crossovers but rather only low pass filters. Your Sub-800 doesn't appear to have but a low pass filter per its manual, and I don't even see an adjustable low pass filter on the Yamaha nor any info about either a low pass or high pass filter in its manual.
Yeah, you're right. It's not a crossover, since it isn't routing the upper portion of the signal anywhere. But the Dayton does have a frequency adjustment on it. The images available on PE website show it on the amp panel. And you're right, no such adjustment exists on the Yamaha... which is why I'd pick the Dayton. I'd have a hard time believing that the Yamaha is feeding full-range signal to its driver though... there must be a LP filter. It's not hard to imagine that they just picked a frequency that would be favorable for that unit's specs and and designed a fixed LP into the amp.
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post #12 of 13 Old 05-02-16, 11:00 PM
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Re: Starting off with Micca MB42X, now amp + sub?

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Yeah, you're right. It's not a crossover, since it isn't routing the upper portion of the signal anywhere. But the Dayton does have a frequency adjustment on it. The images available on PE website show it on the amp panel. And you're right, no such adjustment exists on the Yamaha... which is why I'd pick the Dayton. I'd have a hard time believing that the Yamaha is feeding full-range signal to its driver though... there must be a LP filter. It's not hard to imagine that they just picked a frequency that would be favorable for that unit's specs and and designed a fixed LP into the amp.
Just pointing out the limits of "crossover" on subs. Better subs at best usually only have a particular crossover point of 80hz let alone being adjustable. Just can't stand the low pass filter, despite labeling by the cheap-butt sub companies, being called a "crossover"

Suum cuique Caveat emptor E pluribus unum Veni, vidi, vici....that's what I got out of 4 years of Latin in high school way back when.
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post #13 of 13 Old 05-03-16, 12:01 AM
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Re: Starting off with Micca MB42X, now amp + sub?

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lovinthehd wrote: View Post
Just pointing out the limits of "crossover" on subs. Better subs at best usually only have a particular crossover point of 80hz let alone being adjustable. Just can't stand the low pass filter, despite labeling by the cheap-butt sub companies, being called a "crossover"
Indeed. To be fair in this case, the mistake is mine. Dayton does not refer to their adjustable low-pass filter circuit as a crossover. They specifically say "... a phase switch, independent volume control, an auto on/off switch (activated by an input signal) and a variable 12 dB electronic low pass filter". I quoted enough of that description to cover another vastly more common mislabeling though: "phase"

WAY TOO MANY subwoofer manufacturers, good quality ones included, use the term "phase" when they mean "polarity". The polarity of a signal is +/- voltage with respect to ground, and manifests as the direction of cone travel for a given input. The phase of a signal is referenced to time, and is frequency dependent.

We tend to think of a signal displaced by 180deg as being the opposite, but in fact it is delayed by a half-cycle at a particular frequency. That's why "phase response" is such a tricky issue, and why you see massive cancellation at harmonically related frequencies when you look at a "phase response" curve.

A signal played back against it's polar-inverse counterpart will cancel completely, as the sum of the signals is zero because one side is asking for a series of voltages, and the other side is asking for the equal and opposite voltages.

So in reality, that "Phase 0/180" switch should be labeled "polarity".

/end rant.
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