What does 375 watts do to SDA-1B's

[wingzam]

The reason I ask is that I just hooked up a Soundcraftsmen RA7501 amp to my SDA's with 375 watts@4ohms and at half volume the amp starts clipping, a little more and it cuts out.I'm using the preamp from a Pioneer SA-9500II and 12 gauge wires.I have'nt owned either of these components (amp,speakers) before so don't know what to expect.I havent heard 375 confirmed watts since 1985 on my Phase Linear 400.Am I expecting too much from 375watts on these speakers?They just are'nt screaming yet!!!

[danger boy]

is that Soundcraftsman a pro amp? if so.. that may be the problem.

Use another amp like your Pioneer SA-9500II and see what the results are.. even though the Pioneer doesn't have much power either.

Turning an amp up to half way seems way to much to begin with.. so something ain't right there.

[wingzam]

Just realized the Pioneer(80 watts@8ohms) started clipping at half volume also!And yes the Amp is a Pro model,whats the deal with that?

[george daniel]

I think that the deal is that some of the "pro" amps are designed for P A systems, not you typical home/high end type audio systems,,I did as you did once,many years ago and it sounded like ****. If you can, get a good/used amp such as an Adcom555,B&K,,etc,, you should be able to get a good used amp with plenty of "clean" power for your system for about 300.00 these days,, good luck and enjoy those 1B's :)

[ben62670]

You want good clean power. It's about current not watts with SDA's. Also your pro amp is probably not common ground which is a big no no with SDA's. Don't keep clipping the amps like that or a tweeter will blow. Maybe worse.
Ben

[wingzam]

Oh ****...blew my wad on this thing so will just have to plod along with it until I find something else or perhaps someone diagnoses the problem to a speaker component..not so bad,system is powerfull enough for generall listening,there's just those times when I want to split atoms...

[wingzam]

The amp is a three prong unit.Is this what you're talking about?My place is a two prong house and i've got it plugged into a surge strip.I do have one outlet thats 3 wire,will this help

[ben62670]

Common ground amps mean the speaker grounds are tied together. If you take a multi meter, and measure the resistance across the amps ground speaker terminals it should read next to 0 with a common ground amp. I recommend you contact the manufacture, and find out if the negative speaker terminals can be tied together. Disconnect your IC cable that runs from one speaker to the other for now. I'd look for a used Adcom GFA-535,545, or 555. Don't et the wattage numbers throw you off. Even the 535 will drive those 2B's without a problem. If you really like to crank it get a 555. Also look into Parasound, and a few others. Sell that Pro amp to fund your new amp. Like George said you can get a 555 for $300 now all day long. Try Audiogon.com, and search for Adcom. The plug has nothing to do with common ground.
Ben

[wingzam]

There is 1 ohm resistance.Is this low enough to indicate a common ground?Up till now i've read all good reports on the soundcraftsmen,now the reports are all bad!Welcome to the world of Hi-Fi I guess...

[ben62670]

1 ohm between the black speaker terminals on the amp with the no speakers hooked up to the amp? Sorry I have to double check.

[wingzam]

Yes thats right.

[ben62670]

I think that is too much resistance. If you tie the negative speaker terminals together, and it works you would be real happy, but if you blow your amp you won't. Like I said disconnect the IC cable that runs between the two speakers, and run the amp pretty hard. See how the amp behaves. Don't run the amp anymore with the IC cable connected you can blow the input boards or worse. Also call the manufacture. Listening to me, or anybody else who has not owned the amp, and run SDA's with it can lead you down the path of destruction. If the manufacture says you can tie the grounds together just take a short heavy gage speaker wire, and tie them together.
Ben

[wingzam]

With the neg's tied together would I then rehook the IC cable?This mfr is out of business but I think there's a forum site,will check that out.First i'll run it without IC cable and see how it goes.

[ben62670]

Well I did a little research on that amp, and it is a Class H amp with TO3 output transistors, Darlington pair input boards, and 22,000uf of capacitance. The SDA's would soak up the juice pretty quick. I can not find if it is common ground, and due to the age I am pretty sure you can not get tech support for it. This brings us back to run it without the IC cable, and see how it does. You can call Ken at Polk CS, and he may know. He has been with Polk for a while, and is a wealth of knowledge. Make sure you talk to him on this one, and let him know about the 1 ohm across the amps negative terminals.
Ben

[ben62670]

With the neg's tied together would I then rehook the IC cable?This mfr is out of business but I think there's a forum site,will check that out.First i'll run it without IC cable and see how it goes.

Please don't tie the negs together till you find out if it is common ground!!!


here is MTX's info. MTX bought out Sound Craftsman.
Soundcraftsmen
4545 E Baseline Rd., Phoenix Az 85044-5306 800-225-5689 Www.Mtxaudio.Com

[wingzam]

Affirmative on that DON'T!Have removed IC and am getting the volume level another 8th of a turn up.Thanks for taking the time to find out about the amp,much appreciated!!Will call Ken and see what he says.

[ben62670]

No Problem. I would hate to see you damage something. Polkies have helped me bunches here, and I am just passing it along;)
Enjoy.
Ben

[wingzam]

By the way,you say the sda's soak up the power pretty quickly,would there be a remedy for this in changing the amp TO3 output transistors and/or capacitors.I probably would'nt do this so if you've got the answer just off the top of your head it would be good to know,otherwise don't worry about it.Going after the Adcom appears to be my best bet if tying the negs can't be accomplished.

[wingzam]

Once again,with (if) the negs will tie together do I rehook the IC cable?

[ben62670]

By the way,you say the sda's soak up the power pretty quickly,would there be a remedy for this in changing the amp TO3 output transistors and/or capacitors.I probably would'nt do this so if you've got the answer just off the top of your head it would be good to know,otherwise don't worry about it.Going after the Adcom appears to be my best bet if tying the negs can't be accomplished.

Actually the TO3 transistors used in that amp are pretty stout, and the Darlington pair input stage is one of the better designs, but the 22,000uf for an amp rated that high in watts is pretty weak. Adcom's are one of the best bang for the buck amps for SDA's. They are very powerful, and hold up very well.

Once again,with (if) the negs will tie together do I rehook the IC cable?

Yes

[wingzam]

Right on!

[F1nut]

The problem is that your amp is clipping at that level. In fact, most amps start to clip at or shortly after the half volume position on your pre amp, whether they are 200wpc or 800wpc. Your problem has absolutely nothing to do with the amp being common ground or not. If it did, you wouldn't have gotten anywhere near half volume before things went bad.

Look at it this way. It's not much different than the redline of a car engine. You exceed the limits and bad juju happens.

Turn your volume level down and accept the fact that you can't rock out at 125dB.

[ND13]

Yeah, what he said^^^^

[Ron Temple]

Turn your volume level down and accept the fact that you can't rock out at 125dB.

+1 ... I start pegging the meters on the Carver (400 @ 4ohm) just shy of 110dbs @ 3M.

[zingo]

You guys are crazy listening at anything over 95db anyway...

[danger boy]

why anyone would go to half way on an amp is beyond me.. just doesn't make sense.. that's what the OP was trying to. no wonder his amp was clipping.

[ben62670]

I agree with everyone who says he is over juicing it, but if his readings were correct at 1 ohm between negative terminals they need to be tied(if they can). I know. My GFA-585 seemed fine turned up pretty good, but input, and feedback resistors can blow for sure. I did it twice before I figured it out;)

[Ron Temple]

You guys are crazy listening at anything over 95db anyway...

Hey, I'm not like Ben :D, I've only done this to test a couple of times and to see the drivers bounce. Mostly, I listen around 80-90:p.

[ben62670]

Hey, I'm not like Ben :D, I've only done this to test a couple of times and to see the drivers bounce. Mostly, I listen around 80-90:p.

I truly am working on this. I am tired of smoking tweeters. I have the drivers for my next project, and it will be based on sweet SQ, not lets make the dining room table walk across the floor;) I may govern them with some Poly switches to limit my OCD:o I will build an integrated amp with a tube buffer stage. Time to grow up a little. The leaves are dropping, and the sound is most likely reaching the neighbors now:o

[awe-d-o-file]

Bluebook says it's 250X2, 375 must be a "max" rating. Also there is one for $200 or best offer on C-list >New Yourk>Hudson valley. That says a lot, nothing that is good. The one ohm reading could be the meter being off or having a low battery. Check those two things. Like someone else said something would have blown up if it wasn't. Do check polarity and remember 250X2 is only 5db /ch louder than 80X2.