I need more power
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Posts: 1,365
I have a krell ksa 300s amp, and it doesn't have enough power for my inefficient apogee duetta 2 speakers. Should I get another 300s and passively bi-amp or use 4 monoblocks with an active crossover. My krell blows it's breaker when I'm listening at just over 95 db. I don't do that often but once in a while it's nice to be able to let loose.
Comments
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I think you need a bigger breaker.
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My speakers were measured by stereophile at 80db/w. But they sound so good it might be worth it to try more quality power with them.
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Your speakers have a nominal impedance of 4 ohms. The Krell KSA 300S is rated at 300WPC into 8 Ohms and doubles with each halving of load impedance down to 1 ohm. So 600WPC at 4 Ohms, 1200 at 2 Ohms.
Is your amp plugged into a 20 amp circuit? A 15 amp circuit breaker can pop around 12 amps continuous. My KSA-250 pulls 12 amps idle.Salk SoundScape 8's * Audio Research Reference 3 * Bottlehead Eros Phono * Park's Audio Budgie SUT * Krell KSA-250 * Harmonic Technology Pro 9+ * Signature Series Sonore Music Server w/Deux PS * Roon * Gustard R26 DAC / Singxer SU-6 DDC * Heavy Plinth Lenco L75 Idler Drive * AA MG-1 Linear Air Bearing Arm * AT33PTG/II & Denon 103R * Richard Gray 600S * NHT B-12d subs * GIK Acoustic Treatments * Sennheiser HD650 * -
I have 6 dedicated 20 amp outlets, all wired with 10/2 wire. The breaker in the back of the amp blows.my apogee duetta 2 speakers are really inefficient at 80db.
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You need to have the Krell serviced. Those speakers are not a difficult load for that amp - not even remotely. Something is amiss within the amp, if it’s tripping to protection (breaker)."Conservative Libertarians love the country, progressive leftists love the government." - Andrew Wilkow
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It may need service, but with my sda2A's it was too loud. You would have to peel yourself off the back wall when it was hooked up to those. I never blew the amps breaker with those. It hardly ever went into the 3rd bias lights.
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Perhaps an issue with the crossover(s) within the speaker then... if both the amp and the speakers are in top form, and the amp is getting plenty of AC amperage, the protection breaker should never trip with that combo."Conservative Libertarians love the country, progressive leftists love the government." - Andrew Wilkow
“Human beings are born with different capacities. If they are free, they are not equal. And if they are equal, they are not free.”
― Aleksandr Solzhenitsyn -
I think it's just the inefficiency of the speakers. I will definitely check out the crossovers in the speakers, I wanted to upgrade them anyway. Thanks for the advice.
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The guy I bought the krell amp from was using it just for the bass panels. He had audio research 610T amps to run the mid-range/tweeter and the krell couldn't keep up. He ended up buying krell fpb 750 mcx monoblocks for the bass, and those amps keep up with the 610 T monoblocks
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Me? If I had the coin, I’d PU another 300s and enjoy separate L and R amps - I’m just crazy that way. Pardon me while I take cover from the tomatoes 🍅
However, if and only if, I had a different circuit for the other amp.
OTOH as Scomp & JT suggested your problem maybe the amp or speakers. I’d look there first. If they checked out then go 🛍ing😊.
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I'm thinking that's not a bad idea, one is almost enough but I don't like driving it to the top bias lights. I'd rather have it just up to the third set of bias lights. I've heard a properly powered pair of apogee diva's and they definitely sound better with well over 1,000 watts of quality power.
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I have 3 dedicated 20 amp circuits behind my speakers and 3 dedicated 20 amp circuits for my preamp and source gear.
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I'm no expert at this, first off. How high was the volume dial with 95dB......10 o'clock etc... Next question. What would the power required be for 1 speaker of 80dB/W sensitivity to produce 95dB? I'm calculating 32 W but maybe I'm doing something wrong? If I'm right then I'm thinking that something is wrong with the amp. If you have one of those Killa Watt (sp?) devices it would be interesting to put it into the circuit and record the Watts when the amp breaker blows, along with the dB's at that time.
PS: I realize that your protection circuit in your amp is reacting to peak power, which depending upon the musical waveform present at that moment, will be at least 2x the RMS power, which is what your dB measurement is relating to.Post edited by Gardenstater onGeorge / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
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Onkyo A-8017 integrated
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That's the problem with these large panel type speakers it's hard to get an accurate db measurement. Apogee used a 100 Watt amp at 4 meters and came up with 86db, but stereophile measured the normal way at 1 meter 1 watt and came up with 80 db. Apogee measured max db at 104db.
I have no problem with higher efficient speakers like my sda2A's, which are probably less than 4ohm with the new inductors I put in for the low pass circuit.
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Gardenstater wrote: »I'm no expert at this, first off. How high was the volume dial with 95dB......10 o'clock etc... Next question. What would the power required be for 1 speaker of 80dB/W sensitivity to produce 95dB? I'm calculating 32 W but maybe I'm doing something wrong? If I'm right then I'm thinking that something is wrong with the amp. If you have one of those Killa Watt (sp?) devices it would be interesting to put it into the circuit and record the Watts when the amp breaker blows, along with the dB's at that time.
PS: I realize that your protection circuit in your amp is reacting to peak power, which depending upon the musical waveform present at that moment, will be at least 2x the RMS power, which is what your dB measurement is relating to.[/quote -
Doesn't It depends on how much gain the preamp has and what the input sensitivity of the amp is to determine where on the volume knob you get a certain amount of db? plus the level the recording was recorded at.
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Yes absolutely! Still a valid question though. I'm not familiar with your amplifier, but we are trying to determine if something might be amiss here. The fact that it doesn't trip the protection with a much more sensitive speaker at around the same sound pressure levels doesn't mean nothing is wrong because the peak current and power from the amp would be less.George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
Gardenstater wrote: »Yes absolutely! Still a valid question though. I'm not familiar with your amplifier, but we are trying to determine if something might be amiss here. The fact that it doesn't trip the protection with a much more sensitive speaker at around the same sound pressure levels doesn't mean nothing is wrong because the peak current and power from the amp would be less.
That's exactly what I was thinking, these apogee's even the ones with a higher impedance are still very hard to get high volume out of. -
I would test your amp with a 4 Ohm dummy load and see at what actual power level your circuit breaker is tripping at, as well as what levels of bias lights are lit when it happens. If your 4th level bias light is lit when the breaker trips, that is over 253W peak power, if everything is working properly. I'm wondering how you could only be getting 95dB spl from those speakers at that kind of peak power operation.George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
Gardenstater wrote: »I would test your amp with a 4 Ohm dummy load and see at what actual power level your circuit breaker is tripping at, as well as what levels of bias lights are lit when it happens. If your 4th level bias light is lit when the breaker trips, that is over 253W peak power, if everything is working properly. I'm wondering how you could only be getting 95dB spl from those speakers at that kind of peak power operation.
I'll have to get a dummy load resistor and find out what kind of power it's putting out when the top two blue bias lights come on. Thanks for all the advice and replies from everyone.
