[*Scotty*]

don't you mean BELOW 150hz, not above

Not really,one would cross over mid-ranges above frequency X and woofers below frequency X, X being the cross over center frequency.
 The adequate low frequency capability in the example being the two 12in. sub-woofer drivers seen in the picture.
Scotty

[doug s.]

Not really,one would cross over mid-ranges above frequency X and woofers below frequency X, X being the cross over center frequency.
 The adequate low frequency capability in the example being the two 12in. sub-woofer drivers seen in the picture.
Scotty

yes, i understand that, but if the crossover frequency between the main's midrange and woofer was, say 400hz, like in the case of my speakers which were -2db at 20hz, i would still cross them over to subs, not let them run full range...

doug s.

[zeke]

If using left and right powered subs, is it better to use rca Y adaptors at the plate amp on each side, or just hookup one rca line to each sub amp .   ?? 

thought i had read somewhere that some plate amps have more gain with a double rca connection, rather than single ... ?

[*Scotty*]

With a cross over between the mid and woofer of 400Hz you could definitely lower the potential doppler distortion and THD in the frequency range covered by the woofer if you limited its excursion and how much power you asked it to handle. Thermal compression might also be lowered by getting the frequencies below, say 125Hz, out of the woofer and into the sub.

zeke, I would a connect single RCA from the preamp left channel to left sub and a single RCA to the right sub. This preserves the left and right channel separation. The sub has a volume control on it and you shouldn't need the extra gain that might come from feeding a signal into both inputs on the plate amp.
Scotty

[medium jim]

I agree with Scotty, ditch the y cord!

Jim

[roscoeiii]

I agree with Scotty, ditch the y cord!

Jim

+1

More important the higher you are crossing over

[opnly bafld]

If using left and right powered subs, is it better to use rca Y adaptors at the plate amp on each side, or just hookup one rca line to each sub amp .   ?? 

thought i had read somewhere that some plate amps have more gain with a double rca connection, rather than single ... ?

Won't hurt (or cost much) to try it.
IIRC a friend had do it to have enough gain, although he uses just one sub with the mono out on a HTR.

PS  I'm not sure everybody understood your question. 

[roscoeiii]

Ah, yes, I wasn't reading that closely.

Not sure why you'd need more gain though. More usually, a sub needs attenuation in order to blend with the mains.

[zeke]

Ah, yes, I wasn't reading that closely.

Not sure why you'd need more gain though. More usually, a sub needs attenuation in order to blend with the mains.

I think more gain may be needed to the plate amp depending on the output gain of the preamp itself.
In my case i needed more gain to my plate amp(Rhythmik) with a BAT integrated amp, but i had enough gain when i switched to a different preamp. This was with only one sub in use. I plan on building a second matching sub -- therefore my question about rca hookups to each plate amp.

[trackball02]

I have a question related to my specific set up.

Currently I am running a pair of Superfly's  (16ohm, 101 db) with my Ultravalve from the 16 ohm tap. I just acquired the new Zu Undetone sub, and am interested in hooking up with the speaker level input. Zu suggested that I just run a second pair of speaker wire from either my amp or from the Superflys. Will that change the impedance of the system?

This sub only has speaker level (in) and speaker level (out).

[DaveC113]

I have a question related to my specific set up.

Currently I am running a pair of Superfly's  (16ohm, 101 db) with my Ultravalve from the 16 ohm tap. I just acquired the new Zu Undetone sub, and am interested in hooking up with the speaker level input. Zu suggested that I just run a second pair of speaker wire from either my amp or from the Superflys. Will that change the impedance of the system?

This sub only has speaker level (in) and speaker level (out).

Should be fine, the input impedance of the sub amp is probably over 20k, your speakers are 16...

[srb]

The input impedance of the speaker level inputs is 500 ohms.  A 500 ohm load in parallel with a 16 ohm load is 15.5 ohms.  Of course that is a pure resistance calculation and not frequency dependent impedance, but still wouldn't be enough of an impedance change to matter much.
 
But when I look at the Zu Undertone on the Zu website, it does appear that it also has line level inputs.
 
Steve

[trackball02]

Steve, thanks for the reply. Yes, it has line level inputs, and that is how I'm currently running the sub.  But from my emails directly with ZU, they prefer the speaker level inputs.

[Davey]

According to the spec sheet, the input resistance on the speaker level connections is 500 ohms.  So, there shouldn't be any issues with your existing setup.

http://www.zuaudio.com/docs/Undertone-1A_Specs.pdf

I see line-level inputs on the photo's of the subwoofer amp.  You must have an earlier version that had only high-level inputs?

On most subwoofer amps, the speaker-level input/output is just a simple feedthrough and they're electrically identical.  There's an internal pickoff/divider which provides the signal for the subwoofer amplifier to process.

(Oops, sorry for the duplication.  Other posts while I was typing.)

Cheers,

Dave.