Suggestions? Efficient speakers for a Sumo Nine (65w 8Ω) under $500??

ak_47_boy

Member
2006-09-24 4:27 pm
Just fixed a Sumo Nine for my uncle. Was three blown output transistors. Changed the opamps to a 2604, coupling caps to poly film, changed a few resistores that were out of spec, and i'm going to put a few low esr electrolytics across the power supplies too.

He is looking for speakers, he used to have big electrostatics; acoustat's i think not sure. Might have been quads. This was a long time ago, the amp has been sitting. I'm assuming he just wants to buy some new dynamics though, probably under $500, decent sensitivity, and nothing small because he won't have a sub. I don't know whats available. Maybe i'll tell him to look at the used market. Is my dislike of small speakers unfounded? Wouldn't JBL 4343B's be nice. Oh lord.

I think i'm just weird, my ears can't tell the difference between my HD600s and HD555s nor opamps usually but i can be walking along hear a rustle and walk over to a bush and pull a baby rabbit out without ever seeing it. I love subs but they never blend in and it drives my brain nuts. Maybe that's why i love big speakers. Maybe the big old paper cones add some warmth to the sound? I know i like tube distortion. I don't know. If hes used to vintage speakers are modern ones going to sound tinny and cold?

I think what i'm looking for is somthing like JBL CF120's 96db is nice. http://www.kijiji.ca/v-electronics/city-of-toronto/jbl-cf-120-speakers-250w/1151136181

Would appreciate any input. Thanks
 
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eriksquires

Member
2013-05-10 4:11 pm
In terms of commercial speakers, try the Monitor Audio silver series. Used you should find quite a bit under the $500 range that sound great and musical.

65 Watts is nothing to sneeze at by the way, unless it's a large room most speakers with 88 dB or better should be plenty. If you must have high efficiency, try the Hsu

Subwoofers are a giant pain to integrate properly. "Well integrated" they are awesome, but only about 5% of the people who buy them get to "well integrated." The rest just have crappy loud bass.

Best,


Erik
 
Just fixed a Sumo Nine for my uncle. Was three blown output transistors.Thanks

From what I have read, the Sumo Nine is set for about 5-watts of static Class-A bias, and uses a sliding bias circuit which monitors increases in the input voltage to increase the Class-A bias current to meet the projected increased speaker power demands. The cooling fan is not operating at the low 5W power.

Do you know how much Class-A bias you set after your repair? Sumo Nine repair notes mention the importance in getting exact replacement parts, and the complexity of setting the two bias controls to achieve the initial static bias current and the sliding bias slope.

A high efficiency speaker like the Heresy III would likely stay under 5-watts except for unusual transient head room. No fan noise.
 

ak_47_boy

Member
2006-09-24 4:27 pm
Do you know how much Class-A bias you set after your repair? Sumo Nine repair notes mention the importance in getting exact replacement parts, and the complexity of setting the two bias controls to achieve the initial static bias current and the sliding bias slope.

Just set the bias today. I found 2 more bad transistors shorted base to collector, missed them because the other 3 where shorted base to emitter. All fixed now, no more blown fuses. I set bias to 700ma on all 4 supplies cold. I didn't touch the "current limit" pot, they were both set the same on my ohm meter when i had it apart. I ran the traces over top each other on my scope and they are clean and the same amplitude. Hooked it up and it sounds good. Really nice amp.

They must have added a fan relay circuit in the nine plus. On this nine the fan is hooked right to mains through a 390ohm resistor. Its fairly quiet though.

I looked up the Klipsch Forte and noticed it was 4 ohms. The Sumo manual states 120 watts into 4 ohms. That must be loud as hell at 99dB sensitivity. I think i've been suckered into the wattage war though if 5 watts will do just fine.