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-   -   70V right to speakers? (http://www.diyaudio.com/forums/solid-state/156420-70v-speakers.html)

 fretknowmore 8th December 2009 06:40 PM

70V right to speakers?

so here is what i am wondering
I have a TOA 900 power amp, and i am going to utilize it mostly for playing bass through,
as well as my studio sound,
i am using a 220k input port to the mixer, a TOA 900 as well
but my real question is, would it be alright to hook up a pair of speakers in series at 8 ohms each, straight to the 70 v tap?
there is a 70v, 25, 4 ohm and 8 ohm, with an "ot in" that's bridged to the 4 ohm + terminal.
the speakers are pyles, 18 1000 watt, each, 70V over 8 is 700 watts, well in reason, and how often would i crank it!@!
can anyone help me figure out the best way to get the most power out of this set up,? thank you in adance

 djk 9th December 2009 02:19 AM

A pair of 8 ohm speakers should be hooked to the 4 ohm tap for the most power output.

 ashok 9th December 2009 04:17 AM

Don't forget that the secondary windings will reflect the speaker load back to the amp = speaker impedance/n^2 where n is the turns ratio. Looks like your amp is a 30 watt amp ( into 4 ohms ).
That would mean the output voltage of the amp is about 11 volts ( 11^2/4 = 30 watts approx.)
So the turns ratio for the transformer for the 70 volt tap must be 6.36 .
If you connect 8+8 ohms = 16 ohms at the 70 volt tap the amp will see it as a 16/6.36^2 ohms load = 0.395 ohms !:eek:
The protection circuit will probaby kick in before you get out any meaningful signal. AND you cannot get more output than the amp specifies !
If you connect two 8 ohms in parallel you will get 4 ohms. That connected to the amp will give you the rated output of the amp. That's 15 watts to each 8 ohm speaker.

 multisync 9th December 2009 05:12 AM

the 70 volt tap is not ment to drive speakers directly. There are speakers made for 70volt distribution. ie paging system all over an office. The speakers used in a 70volt system will have a step down transformer mounted on each speaker. The reason is simple if you are going to run speakers all over an office for paging, or musac or whatever you would have to use very thick wires other wise the signal loss would be high. So the solution is to take the amplifier output and step up the output voltage and lower the output current at the same time thereby allowing the use of long skinny wire runsand much lower power loss. Modern highpower amplifiers can drive 70volt lines directly, but there would still be a step down transformer at the other end or a speaker with a very high voice coil impedance.

here is a link that explains it. or search " 70volt speaker systems

Yorkville Sound: 70 Volt Systems Explained

 fretknowmore 9th December 2009 01:32 PM

70 volt to speakers

nobody mentioned the 4 ohm tap.
and 30 WATTS is a little small for this amp
it's a 240 output
there was a TO bridge to the 4 ohm tap,
this was taken out,
two 8 in series, in parallel with 8