svs passive and adcom 555

artinaz

I am planning to drive a passive cs-ultra 16-40 with a mono bridged adcom gfa-555. Should I be worried about stability? I think I read somewhere that if the impedance dips low, a bridged amp will have problems.

Opinions, experiences welcome.

Azi

GEBBY44

You probably wouldn't have problems in most situations since the 555 is a pretty stable amp, but on very demanding passages, it might go into protect. I would recommend selling the 555 and buying a Samson or Behringer amp, which is what most people use to drive passive subs, and you would probably put a little money back in your pocket since the 555 usually goes for around $300 and the other amps are slightly less.

ben62670

For sure keep the 555 over a pro amp. They are stable 2ohms stereo, and 4ohms mono. No issues what so ever. I have done it, and broke(literally) a 15" Dayton Titanic Mark III's cone loose from the voice coil. You would be very hard pressed to overdrive the 555 without sending continuous sine waves at max output to over heat it. Keep it well ventilated and run it.

GEBBY44

I stand corrected. Why have I been so brainwashed about passive subs and pro-amps. Grrr

kuntasensei

You're probably good with the 555. The Ultra can dip down near 2 ohms when in use, but only briefly. One way to find out!

I'm running my 20-39CS+ and a Buttkicker LFE off a Samson 1,000 though, and if the Adcom doesn't work out, I can tell you that a Samson makes for a nice replacement. I've had it running for over 3 years without turning it off, and it's rock solid.

Honestly though, if you're worried, shoot an e-mail over to Ed Mullen at SVS. Even if you're not the first owner of that sucker, they're always more than willing to help owners of their subs with technical questions.

ben62670

SVS will hear a stereo amp bridged mono and laugh. The 555 is very well built. Not typical of what most home audio amps are capable of driving. Again I drove an 800wrms 15 sub with no problems at all.

kuntasensei

Man, they won't laugh, 'cause I guarantee you they've probably all been there. You forget those guys all came from the DIY scene. If you ask them if they think it'll drive it, you're likely to get some very good advice. But in my opinion, that Adcom 555 is a monster and you'll probably be just fine. Just ease into it at first and test its limits, checking occasionally for excessive heat and keeping an eye on the protection lights.

artinaz

Thank you for al the replies. Its good to knwo that I can use the 555 to drive teh sub- this means that I wont have a downtime till I get a samson to drive it (if I decide at all to go with a samson instead).

Great, one less decision to make in life.

Azi

kuntasensei

If you ever do look for better amplification for it, I believe the Ultra's nominal impedence was actually like 3.5 ohms. Make sure you get something that'll be stable down to 2 ohms if possible. I know back when SVS originally unleashed the Ultra and Plus series, they were offering the Samson 1000 and Crown K1 as options, so something similar should work nicely. Otherwise, poke around some of the DIY forums at AVS and places like that to see what people are using.