Posted by Stever on February 02, 2004 at 21:58:45:

In Reply to: Re: Sansui TA-500 posted by BeatleFred on February 02, 2004 at 21:15:24:

Hi B/F,

The back of the TA-500 says:

"CAUTION: Speaker impedance must be 8 ohms or more. When using two pairs of speaker systems, total impedance must be 8 ohms or more."

Sooo... hooking two sets of 8 ohms spkrs up to A and B gives you a 4 ohm nominal impedance facing the amplifier. So I figured that if I was using a 4 to 6 ohm set like the Kappas, I could only use one pair hooked up to the ouput of amp. Hooking up a second pair of anything would be "verboten" cause it would lower the total impedance seen by the amp to less than the 4 to 6 ohms.

Thanks again for info... I also just placed an order for a service manual per your directions above.

Stever

: Hi Stever:

: The thing to know is, (and what I'm not exactly clear on from what you wrote) what does it say on the back of the TA-500 and/or the manual for the TA-500, does it say its rated for 8~16 ohms, or 4~16 ohms?

:

: If its 8~16, then I would say to use only 8 ohm speakers with the TA-500. If its 4~16, then the Ren 90's wouldnt really present too much of a problem to the TA-500. Keep in mind though, that if its rated 4~16, what you should NOT do is connect two pairs of 4 ohm speakers to them, in other words - dont connect one pair of 4 ohm speakers to the A terminals and another pair of 4 ohm speakers to the B terminals, because in effect what youre then doing is putting the two pairs in parallel, and this results in the amp seeing a total impedance of '4 ohms in parallel with 4 ohms' which is the equivalent of a 2 ohm load, and the lower impedance then means the amp has to work harder to provide more current capability. And most amps dont really "like" 2 ohm loads.

: The thing to be aware of is that the impedance rating of a speaker, be it 8 or 4 ohms is NOT a fixed value. This value will vary over the audible 20-20Khz freq range. How much it varies in its impedance curve, especially at what freq's it drops low and closer to the 2 ohm region and below, is what determines how "demanding" a speaker is on an amp. The Renaissance 90 is rated for 4 ohms but drops to a low pt of 3.3 ohms which is isnt too bad. The Kappa 9 as I recall has a much lower impedance and varies more over the freq range and is a much more difficult speaker for an amp to handle. The Kappa 6 is smaller then the 9's but I dont know if its shares the same impedance characteristics as the 9's, probably theyre not quite as "bad", but I would make sure about it before I'd buy them if I were you.

: Also what should be kept in mind is that Power and Volume level is not a linear relationship. For example, a person that weighs 200 pounds is twice as heavy as a person that weighs 100 lbs - thats a linear realtionship. But a 200W amplifier is NOT twice as loud as a 100W amplifier. Our hearing is logarithmic in nature, not linear. Thus, you need to increase an amp's power by 10X in order to perceive a doubling of volume level, meaning 10W to 100W, 50W to 500W, 100W to 1000W and so forth.

: It is actually good that we hear logarithmically. Example: if you were to stand next to an airplane on a runway that had a sound presuure level of 130dB, (and thats pretty loud), what would happen if a 2nd plane came along and parked alongside it? The answer is that our ears would perceive the 2 planes to have a combined sound pressure level of 133 DB, which is logarithmic. Thus 2 planes are only 3DB louder than 1 plane. If our ears heard linearly, then we'd hear 2 planes instead as 260 (130dB + 130dB), and surely 260DB would blow our eardrums out.

: B/F