Am I wasting money on the theory of Bi-amping?

@russbutton 

Now when you use an active crossover, an amp channel only has to manage a single driver. There's no passive, reactive component in between the amp and the loudspeaker driver. Then you don't need a megabuck amp to deal with it.

Indeed! It's amazing what you can get out of cheap amps when hooked up to speakers with an active crossover. With horn loading the problem is amp hiss gets highly amplified. For this reason I add a capacitor to my horn tweeters. It knocks the amp hiss down to below noticeable, helps with the EQ needed for constant directivity waveguides, and provides some protection for the tweeters. I'm not a purist.

@btbluesky 

I have 4 AHB2 bi-amp on mono-mode to JBL 4367

I have no doubt that sounds great. What differences do you notice if you just use a single AHb2 in stereo mode compared to all four in mono?

@asctim , I did just that. Starting with 1 AHB2 with a different speaker, notice the bass is tighter and it was not sterile/cold sounding. Smooth, highend, you are hearing really the upstream/preamp.

Then got another one, mono mode to each 4367, sounding great, everything falls into place. so I ordered another pair for my secondary system, but tested it biamp mono in JBL first, the realism, the "air" is just unbelievable. Diff between ya I can see the imaging, to "where did that sound come from!". Needless to say I left the pair there and got another pair for second system.

Amp hiss, is not a normal thing. It's a product of "too much gain in chain" + "not so good amp". I can crank up to over-concert level, and theres no distortion.

@asctim wrote:

With horn loading the problem is amp hiss gets highly amplified.

Indeed, but using a 16 ohm driver - if available - will help knock down hiss noticeably as well.

@btbluesky wrote:

Amp hiss, is not a normal thing. It’s a product of "too much gain in chain" + "not so good amp". I can crank up to over-concert level, and theres no distortion.

It doesn’t fall back on a "not normal thing" or a "not so good amp." High sensitivity, as has been stated just above, simply amplifies noise. If you removed the passive crossover from your JBL 4367’s and connected your amps directly to the compression drivers, I can assure you hiss would be audible to some degree - and yet your amps are the same; they didn’t suddenly get bad in the absence of passive crossovers (in fact they’d get better).

It’s great though you’ve found a good pairing amp-wise with the JBL’s.

@russbutton --

+1

Another major benefit is that you can use much, much lower powered amps when you use active crossovers. A lot of power is wasted having to push through a passive crossover. You really don’t need to push many watts into a tweeter or mid-range driver to get a lot of level out. You could even run a single ended tube amp on your tweeter, and a mid-level tube power amp on your mid-range driver, and a solid state amp for the bass driver. You have a lot of options.

Options are plentiful, yes. To me though the lesser power needed over the entire frequency range actively would be better served by spreading it out evenly, so to ideally use the same amps top to bottom, or certainly the same amp series/topology with a differentiated power approach for better coherency. To me coherency always comes first, and using similar amps is vital for this to come true in the best way.

If you removed the passive crossover from your JBL 4367’s and connected your amps directly to the compression drivers, I can assure you hiss would be audible to some degree

Nope. You are describing the scenario of what a normal system with an acceptable noise already present in the chain, but not when you are using absolute silent components. Lookup the AHB2 review from stereophile, the amp not only can adjust the sensitivity (9.8V RMS/22dBu, 4V RMS/14.2dBu, 2V RMS/8.2dBu), it has such a low distortion number, akin to the testing equipment that bench test the amp itself. If your upstream is absolutely silent, if theres noise/distortion in your horn, it's something else. Uber horn lovers pay big bucks for expensive tube amps, not just for it's tone/sound, more often it's for the silent. And they do directly connect to the compression driver with active setup.