The KEF LS50 and tubes WOW WOW WOW!

DaveyF said:

Wouldn't this apply regardless of whether a sub was in the system or not?? Remember the sub has its own power amp...so in effect the amp for the mains is really only driving the mains.

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Frantz suggested a REL sub which goes between the power amp and the main speaker. It has a high-pass filtered output for the main speaker, and the sub has its own power amp.

mep said:

Gary-If I'm looking at the graph correctly, the impedance doesn't drop to below 4 ohms until the frequency is less than 20Hz. At around 55Hz, the impedance dips to over 5 ohms and then peaks again at around 42Hz to almost 12 ohms before the impedance starts nosediving. Sometimes when I look at the LS50s and then look at the KSA-250, I can't believe I'm driving the LS50s with that much amp. The LS50s make the KSA-250 sound like it is the most neutral amp on the planet-a real sonic chameleon that has no sound of its own. Or is it the other way around?

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Where the impedance starts to rise is where the loudspeaker starts to bottom out in its frequency response. Beyond the peak, the speaker produces no output for the input power. Hence, the need to filter out the lower frequencies to help the amplifier - not that your KSA-250 will need it.

garylkoh said:

Where the impedance starts to rise is where the loudspeaker starts to bottom out in its frequency response. Beyond the peak, the speaker produces no output for the input power. Hence, the need to filter out the lower frequencies to help the amplifier - not that your KSA-250 will need it.

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It could be a serious issue when I finish rebuilding my pair of Dynaco MKIII amps.

Davey


This may require a thread of its own. The subject is very interesting but understand that int he case of a subwoofer using the speakers output, that is the signal is taken from the amp output and the subwoofers only reads the signal from the amp, the input impedance of the sub is very high, high enough not to load the amplifier, IOW the amplifer from its point of view, sees an ope circuit. it is not really driving it. while 4 Ohms is an issue for an amp, 10,000 is seen a s an open circuit... Not a problem for most amp: A high impedance load in parallel remains for all practical purpose a non-load. Same as when you put a VOM across the speaker terminal, the behavior of any sane amp shouldn't change at all.

meanwhile the amp is still feeding current and voltage to the speaker even if the response drops to nothing. The elements/drivers of the speakers do receive this power but can;t do much with it.. It heats up the voice coil or other elements and that has negative effects on the behavior of the particular driver or drivers.

Frantz, that's a good idea, I have started a thread to discuss this.

DaveyF said:

Frantz and micro, could you tell me another subwoofer company that utilizes the same connection protocol as REL. Speakon cable to amp speaker connections.....

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I will give two: Marting Logan Descent i - I am facing it. Sonus Faber Gravis - it is upstairs. BTW, the speakon is just a professional connector for speakers.