output impedance of preamp into active crossover

[Dax617]

It is my understanding that low output impedance should go into high input impedance. I have a bez pre amp and wish to go into an active crossover inorder to use my hgs velodyne (18 "). The behringer is rated @ 25 k input . For the average tube preamp would this be a mismatch and would it be audible?

Thanks T.C.

[DrWho]

Usually the audible effect is a high-noise floor and loss of frequency information. In the case of a subwoofer, your biggest concern will be the gain structure. When there are impedance "mismatches" you'll either have to crank the gain to get any volume or keep the gain at just above off.

In any case, a transformer can be implemented to account for the impedance and an active unit can be implemented to account for the gain differences.

http://www.musiciansfriend.com/product/ART-CleanBOX-Two-Way-Stereo-Converter?sku=180613

[Dax617]

Thanks for the response! In my case the info is going thru th xover into (2) dynaco markIII's (the gain is fixed) as well as the sub. I am more concerned that I am hearing distortion and loss from the markIII's due to an impedance mismatch and possibly overdriving them with the signal level out of the behringer. I feel there is a difference in sound quality when using and omitting the xover. I was wondering if anyone else using a sub has had this difficulty. I believe the typical input impedance is around 25k for most units and the average output inpedance for most tube preamps is higher.

[Dax617]

I just contacted Behringer tech support. The cx 3400 xover does basically the same thing as a clean box.However it does nothing for the intial impedance mismatch ( I assume there is one)and the +22 db signal output can only be attenuated -6 db.

[DrWho]

What are you using for mains?

One thing you might try would be to attach y-adapters to the back of the preamp - sending one full range signal to the mains and another full range signal to the crossover. You can then dial in the subwoofer to fill in where the mains naturally roll-off. Perhaps even introducing a little overlap to fight possible room issues. This will get that Behringer outta the signal path of your mains and minimize your impedance issues (a little extra volume on the sub might even be needed - especially if you're running klipsch).

What kind of amp is driving the subwoofer?

[Dax617]

My main speakers are Khorns and the subwoofer is a hgs-18 velodyne. Because of the distance from the source, I use the balanced connects.I prefer this to the speaker and line level options. The hgs has an integrated class d amplifer. I usually cut the sub @ 50-60 hz. Will there be a consequence of splitting the output from the preamp such as signal loss? I can boost the input to the sub thru the active xover.

[DrWho]

No signal loss when you do a split. It's just like connecting two

speakers to the same amplifier channel. The output to each channel is

the same (same voltage) but the power being delivered doubles (same

current going to two speakers, so twice as much overall). You aren't

going to come anywhere close to the max current capabilities of your

preamp so you'll be just fine. This approach will also work pretty well

with your 50-60Hz crossover since the khorns definetly start dropping

by then.