[smccull]

I have a pair of RM30s, which I love, and want to experiment with passive biamping. I've never biamped, so your help with my newbie questions is much appreciated.

I have a tube integrated I plan to use for the ribbons and a SS amp for the woofers. Is it as simple as splitting the output from my pre and sending it to both amps, then connect the amps to the speakers without the jumpers? From what I read, I may need to adjust the volume on the integrated to match the woofer, but I should be able to run it with the midrange pots all the way up and the tweeters down from there a bit.

Am I missing anything?

Thanks!

Steve

[BobM]

From your description it sounds like you've got it. Clearly one amp will probably be stronger than the other one, so you will need to adjust and balance the voilume down on one to match it correctly.

Here's a trick I used - run the speakers with the lower sounding amp, connecting the speaker cable to one of the binding posts (i.e. bass) and jumping the binding posts (to the tweeter) with a piece of wire. Get a level on the music, then disconnect the first amp and try it with the second, louder amp - then adjust the volume down on this amp until the sound is at the same level of the first amp. Clearly a sound pressure meter would make this easier, but using this method by ear should give you a reasonably good balance point between the amps when they are biaming together.

One warning that I found out after trying biamping for a couple of months. I found that there was a discontinuity in the sound that was easily resolved when I just used one of the amps to power the whole speaker. Biamping can cause a loss of cohesiveness between the top and the bottom, but by all means try it for yourself. You may not experience the problem I had.

Enjoy,
Bob

[PLMONROE]

Good point. In an ideal world one would bi amp with four identical amplifiers, however most of us want to use tubes on the top and SS on the bottom. I think its another case of synergy. In my limited experience it seems that some non identical amps just seem to integrate with each other better than others. Also I think matching the sound levels with a really good SPL meter is critical.

[warnerwh]

If your amps are within a few db of each other remember you have level pads on the back. That is how I've adjusted mine.

I'm using an Earthquake Cinenova on the woofers and a Van Alstine on the planar/ribbons. The AVA amp has a lower gain. Turning up the lpads on the back was all I needed.

It's definitely worth the effort in my experience. Running the AVA tube hybrid on top is a definite improvement over any single SS amp I've tried.

Sounds like you got it right. Just be sure to remove those jumpers!

[Delacroix]

I believe the gain match between the amps is important here. Most amp manufacturers will tell you this and provide the gain spec for their model. That said, I have had a variety of manufacturers tell me completely different things as a result, ranging from 'try it and see, it should be fine unless the gains are far apart' to 'there is no advantage to this unless you just want  SS with a tube sound on top'. One can buy attenuators to balance the sound within a 10db range, which might be the easiest way to try things out but I've never used any so I cannot tell if this works well or no.

[woodsyi]

You are good with tube integrated.  It's usually the tube amp for the ribbons that needs attenuation.  If you have a tone generator or recorded tones, just match the SPL and you are good.  You may find yourself changing the pot setting and redoing the putty after.  I did.

[Housteau]

If your amps are within a few db of each other remember you have level pads on the back. That is how I've adjusted mine.

Yes, exactly.  This what I was able to do.  In fact mine were more than just a few db apart and there was plenty of adjustment left in my L pads.

[Hipper]

Warning: this is an old thread.

If the difference between the sound levels from the two amps is only a few dBs, could that be dealt with by a digital equaliser placed somewhere in the system before the amps?

Is that a wise way of doing things or is it better to use the L pads, or a seperate attenuator?

[simon wagstaff]

I would think a digital eq would have too many bands in the area that needed adjustment and it would not provide linear attenuation. L-pads would be better.

In my experience it is the tube amp that has the lower input sensitivity. I have a Van Alstine U70 and it is definitely lower than the SS amps I have used. The ideal situation in my mind would be a SS amp with input level controls.  There are a few of them out there, some of the Parasound ones come to mind.

[Hipper]

I already use a Behringer DEQ2496 in my system.

When this is set up you have to go through a testing progamme involving pink noise and this should detect any modest differences at the listening position [for example, I could do this if I change from having the wave guides on or off (these make a 3dB or so difference to the mid and upper frequencies)].

I suppose using the L pads would give more room for manoevre on the Behringer.

[simon wagstaff]

Wouldn't that allow you to do active bi-amping instead of passive?  it would have level controls for the different outputs, or is it a different unit?

[Hipper]

You're thinking of the Behringer DCX that is used on the D-OXO.

The DEQ2496 is just a digital equaliser with a digital and parametric facilities, and some other stuff that's useful for playing music live.

[Devil Doc]

My error

Doc.

[PLMONROE]

smccull- if you want utter control and flexibility consider also picking up a DCX2496. Used ones are relatively inexpensive. Run your signal into the DEO2496 and its digital out to the digital in of the DCX2496 and you cantrol EVVVVVVVVVVVERY thing! 

Paul

[Housteau]

I think Paul is a control freak .

[PLMONROE]

In SPADES Dave! See you at RMAF?

Paul

[Housteau]

See you at RMAF?

Paul

With any luck both Frank and I will both be there, but as usual it will all depend on our work schedules at the time.  It will probably be a last minute decision once again.