Relieving Zenith 12" of sub 120hz?

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So, I have a pair of 12" Zenith CZ full rangers in open baffles. I am thinking of buying a Dayton TPA3116 2.1 amplifier and building a passive subwoofer. The bass channel on the Dayton crosses over at 180 hz which is a bit high but might be good in this case because the Zeniths have a very limited xmax and I've been warned to not push them too hard because of this.


Would it be good to relieve the Zeniths of, let's say 140 hz and below, via a pass filter? If so would a single cap (per driver) achieve this filtering? Before I get into specifics about value of cap and so forth, do you think this is a workable situation? Thanks for any help!
 
music soothes the savage beast
Joined 2004
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Do you have some fr measurement? Like a umic and holms or rew?
I know 'microphones shmicrophones', some people here do not believe in measurements, but for me, that is the only way to achieve objective results. You can modify to subjective liking, but no amount of simulation will ever tell you how it will really sound in your room.
 
music soothes the savage beast
Joined 2004
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Yes, same thing. Yes, that's what i would get. I suggest get a pair with value above and bellow, so you can swap and compare. They are cheap. Plus, if your sub goes up to 180Hz, you may want to cross zenith little higher, as not to have too much overlap. That may create midbass bump.

Well, ideally, you would want to have two subs, close to open baffles, with variable pot for fr cutoff, volume and phase...like plate amps offer. That may be next step. One has to start somewhere.
 
STOP.

I'd think twice about using only a capacitor for a highpass filter on a full-range speaker, when it might be near resonance.

Here's why: Passive Crossover Network Design

Scroll down a bit, and you see the response curves that you get from having a crossover slope that's somewhere near the driver's resonance. The capacitor interacts with the impedance peak and actually puts a spike around the driver's Fs. For a driver with limited Xmax, that's really not good - it's actually going to see more power down there!

My recommendation would be to add a highpass filter (simple cap) at the power amplifier's input stage. That way, you get to use small high-quality caps instead of big electrolytics, and you'll avoid all the messing around with impedance curves.

Chris
 
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