RF-7 biwire with 1 tube-amp

[gorilla]

Hi,

Since the Rf-7 has the odd impedance-curve I thought; "What happens if you connect the highs to the 8-ohm and the lows to the 4-ohm connection of the same tube-amp."?

That will be a Cayin a88 with KT88 tubes in the near future:-) ...played at moderate level.

Will this ,for example,damage the output transformers ?

Martin

[leok]

Martin,

I don't think it will hurt anything. The volume of the horn will be unmatched (higher) than the cones, however, because for a given Volume Control setting the 8 Ohm Voltage out from the amp is higher than the 4 Ohm Voltage out. Give it a try and tell us what you hear.

Leo

[gorilla]

O.K. ,I will, when the amp arrives.....

Thanks.

[Guest " "]

Wait one

No damage to the amp will occur provided you remove the bi-wire jumers that are on your speakers across the HF and LF section. If you don not remove the jumbers, you could damage your amp since you will be shorting out the 8 ohm tap to the 4 ohm tap. Theres voltage in them there hills...even across the 8 and 4 ohm tap.

Now, about your choice of which would go where...in your proposal if you connect the HF to the 8 ohm tap and the LF to the 4 ohm tap, you can look at it as either the HF would be +3d louder than the LF or that the LF would be -3d from the HF.

This is due to the greater voltage potential across the 8 ohm tap than the 4 ohm tap.

if you want more highs and less bass, do it as you propose.

If you want more bass and less highs, put the LF on the 8ohm tap and the HF on the 4 ohm tap.

final pointof consideration. Ideally, you would want to put your speakers or speaker sections on the tap that is the nearest to the speaker or section impedance or lower, but not higher.

[gorilla]

Yes, I know that much about it not to shortcircuit the output tranny[]

The reason to do this is the impedancedrop to 2.8 ohm on the low side and the 8 ohm rather constantly on the high side.

To equal the output, is there an easy way to level-out the higher high-output?(change something in the highpass filter?)

[Guest " "]

gorilla

Check this pdf out.

My take...use technical measurments as a guide.

Room accoustics will factor in and some tweaking may result. It is possible that you would wind up with combinations the mesurements can not explian.

For example, I once had A HF section on the 2 ohm tap, the Mid band on the 4 ohm tap, and the LF on the 8 ohm tap, even though they measured out as 6.8 ohms on the HF, 11 ohms on the mid band, and 3.8 ohms on the LF.

McIntosh%20Autoformer%20Training%20Page.pdf

[gorilla]

Hi Fritz,

Good to see that it's a concept already tried out.Thanks for the info.

Seems it all comes down to try and listen.At least it does'nt seem to damage anything and that's good to know for a start.

At the moment I Bi-amp them with a SET el84 little "Aurexx Crystal One" for the highs(switched it to triode) and a MosFet Labgruppen amp for lows.

No nice tube-mids this way,and the gain's don't match ideal; hence the Cayin....

As soon as it's arrived I'll try it out.

[rsp1068]

To equal the output, is there an easy way to level-out the higher high-output?(change something in the highpass filter?)

Put a big 5 or 6 ohm wire wound resistor in series with it off of the output tap.

[Guest " "]

gorilla

if you need to tweak furthur there are autofomers of various sizes that can be used with out increasing distortion as in line resistors do.