5-ohm OPT with small 4-ohm speakers?

[Sonance'84]

I'm looking at a Manley Labs 75+75 power amp. Everything I've read states that the Manley OPT's are optimized for a 5-ohm load, from the factory. One review said this prohibits them from being used with loads that dip below 3-ohms in the bass.

My speakers are M&K S-2b, rated at 4-ohm and sensitivity is about 90db. Power recommendation is 10-200 wpc. Freq. response is 65-22KHz (+/- 3db). They're a smaller 2-way design with a 1" soft dome and 6.5" mid/woofer. Rebuilt crossovers, so all new parts.

At times, I like to crank the system up to loud volumes, but never ear-bleeding levels or into distortion. I sit about 9' from the speakers and the room is fairly large with a high ceiling.

My concern is whether or not my speakers are capable of dipping down so low, below 3-ohms. Do you think these speakers would dip that low? Is that even something to worry about with a 6.5" woofer? Would this be a safe pairing?

 

[larryderouin]

If M&K are still in business call or email them and ask for an impedance vs. frequency graph. This will show what changes the impedance takes and at what frequencies.

 

[Sonance'84]

If M&K are still in business call or email them and ask for an impedance vs. frequency graph. This will show what changes the impedance takes and at what frequencies.

The original M&K company isn't around anymore, but the original designer Ken Kreisel is around and might be able to provide that info. Probably a long-shot, I'll email him and see if I can get some more info.

 

[MurrayLives]

I use 4 ohm speakers with Manley’s, no problem.

 

[Sonance'84]

I use 4 ohm speakers with Manley’s, no problem.

What model(s)?

 

[MurrayLives]

What model(s)?

AR3’s with Neo-classic 250’s.

 

[Sonance'84]

Good news, everyone!

I emailed Ken Kreisel (original designer) yesterday and although he didn't have an impedance curve, I received a reply this morning saying this:

"I am sure the S-2B portion of your SV-200 does not dip to 3-ohms or below.The impedance is probably more like the 5-ohms that the Manley amp "likes."I bet the Manley amp will sound awesome."
So, I think I'm gonna give the Manley amp a try and see if it jives with my system.

On a side note...I love the fact that certain speaker and amp designers are still around to share some knowledge and are happy to do so, even if I'm not asking them about one of their current products. I know there's quite a few of them out there that still help out the DIY community. The same thing happened when I emailed Manley the other night, I received a reply fro EveAnna Manley within a few hours and she was very helpful. I dig it.