Crossover confusion


Hi All, 
  While I'm not a technical expert with stereo electronics and software, I do understand a lot of it. My problem is clipping on my woofers when playing the Stereophile test CD track 31 (20Hz 1/3 octave at -20db ). 
It would probably be best that I list my equipment from source to sound.
1.) Cambridge CXC transport
2.) Nad M51 DAC ( via fiber optic)
3.) Audio Research LS3B preamp ( all other interconnects are Kimber PBJ's ) 
4.) Bryston 10B Hi Lo crossover. ( Settings are 80 Hz for the low pass. 70 Hz for the high pass. High pass db is 0.)
5.) Low pass frequencies go to a pair of Audio Fathom F-113's which are active subwoofers
6.) Hi pass frequencies go to a Krell FPB 300 power amp
7.) Kimber T12 cables connect to PNB B741 speakers ( with two additional midranges) that have been fitted into a 
    pair of Dunlavy SC-IV's. The cables are Bi-wire that are common at the amp. The smaller conductors feed the midranges and tweeter. The larger conductors feed the woofers.
  My thoughts are that none of this 20Hz signal should  even be going to the Krell amp.  While I haven't heard any clipping when listening to music I am concerned. I was researching passive crossovers and came across Marchand Electronic's website. They make both active and passive crossover's. One of the diagrams show a hybrid setup that uses an active crossover with the hi pass going directly to the midranges and tweeter and the lo pass going to a passive crossover and then to the woofer. Before talking to Marchand Electronics I thought it would be a good idea to come here first since I've gotten a lot or good info here. If I have to use a hybrid setup, it would also be useful to know what the crossover Hz should be. The PNB B741 woofers bottom out at 25 Hz. Hope this is enough info for those that can help.
  Thanks to all concerned

















 
evelyn1

Showing 3 responses by ivan_nosnibor

I would add that if you experience the woofer clicking again with the same test you ran as before - even at low volume - that the original problem is not really power-related and is actually signal-related...and might be another finger pointing to the Bryston, perhaps.
Hi, first I’d like to know what slopes on the Bryston you’re using. The frequency choices of 70/hipass and 80/lopass should make for a rather wampy response overall, but I understand the limited selection choices with your equipment. A new standalone passive crossover will not necessarily help you any if you currently have to ’guess’ at what the frequency selections should be. It would likely be much better in this regard for you if you had a unit with much more flexibility of control in order for You to experiment enough to discover what settings will work best.

(I’m assuming that you have bypassed the active crossover in the Fathoms in order to use them with the Bryston).

Give serious consideration to holding off buying a Marchand (or other crossover, whether passive, active or hybrid), or sending the Bryston in for repair, until the true nature of the audible problem becomes verifiably clear for you.

Audible "clicking" through the woofers might be digital distortion, correct me if I’m wrong here...caused by audible dropouts in volume...not usually considered harmful unless perhaps at very loud levels. That might be a digital input level issue somewhere, if that applies to your situ. If it is actually your woofers bottoming out, then this is indeed dangerous, of course. If you haven’t already, of course, double and triple check your Bryston to see why low frequencies are apparently being passed...change slopes to see if it has any audible effect or none at all. If it has no effect, then I ’might’ begin to suspect a faulty Bryston. Change other Bryston parameters too and see if the problem remains constant.

Check back in with your findings.
Yes, erik is quite right, they're not brickwall devices. At this point, I would venture to guess that you're now on the right track and that it's just a matter of experimenting and tracking down the right settings, on the digital side of things most likely. Hopefully no need for testing.

Good luck and let us know if the problem doesn't get worked out.