[SteveRB]

Hey guys,

I just hooked an old yamaha integrated up to my Alpha 15's and it really shakes the room.

I'd like to learn more about bi-amping: any good resources, tips, recommendations out there?

(my current set up: http://www.audiocircle.com/index.php?topic=91341.0 )

[richidoo]

http://sound.westhost.com/bi-amp.htm
http://sound.westhost.com/bi-amp2.htm

[SteveRB]

Thanks for the links. They are informative, if not a bit dry. Personally, I'm missing a bit of practical application knowledge.

Perhaps someone could comment on my current set up:

the Visatons are running straight off the speaker taps on my Eico HF81 tube amp (14w per channel). Then, from the Line-Out jacks on the Eico I'm feeding the source inputs of the Yamaha integrated (60w per channel). Then, from the speaker terminals on the Yamaha to the first Eminence with a 1mH inductor in series. the two Eminence drivers are wired in parallel. After that i was simply using the volume control on the Yamaha to dial in the LF.

...as i mentioned, it can really shake the room.

I suppose the first place to start is to ensure that the gain of the amps is comparable to ensure proper crossover frequencies -- and to find a suitable quality amp for the LF. I hesitate on installing a pure sub-woofer amp just because I do want it to cross over higher than 300Hz...

I'm wondering is there a better way to hook the system together?
Am i introducing a tone of unknown variables (phase, gain, crossovers, coloration)?

What type of amps are common for this use?

Thanks again

[JohnR]

From your description, it appears that there is no lowpass filter on one of the Alphas. That might be something to look into.

You could continue to tweak it with passive crossover, or you could use an active crossover. I use the miniDSP. With your setup, though, you would be limited to using it on the woofer, as there's no way to get the line-level signal back into the HF-81 power amps (short of modifying it).

The amp you have should be fine with the pair of Alphas. It isn't the first thing I'd be looking into, at least.

In either case, being able to do an acoustic measurement is (I have to be careful how I phrase this as apparently some people are allergic to the very concept) "helpful"

Let us know if the above helps at all.

[SteveRB]

I would like to learn more about some making proper acoustic measurements. the music i listen to is all over the map, and sometime really poorly recorded. I like my system to sound good -- not necessarily correct.

the low pass filter is before both Alphas. I'm going to pickup a 2mH coil this weekend to get the cutoff closer to 300Hz. the whole thing is a little muddy -- but i'm seeing the potential.

Would the coils be better inserted before the bass amp or after? i guess i'll try both.

[Tyson]

Measurements are critical!  Get a good mic and download HOLM Impulse (free and excellent measurement software), and get a USB microphone preamp (I use the MobilePre).  It takes a bit of time, but it is absolutely worth it.  Otherwise you are literally throwing darts blindfolded.

Dialing in a speaker is somewhat difficult even with good measurements.  Without them, it's impossible!

[JohnR]

Would the coils be better inserted before the bass amp or after? i guess i'll try both.

They won't do anything (useful) before the amp. If you'd like to try doing the crossover at the amp inputs (worth a shot) here's some info:

http://www.t-linespeakers.org/tech/filters/passiveHLxo.html

With an active crossover you will get much steeper slopes and easy adjustments and eq, but the passive solution above might be a useful experiment. Will save a lot of money on big inductors too.