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Experiments with semi-active bi-amping seem to give quite interesting results so far: first amp full range driving the speakers passive 3way networks (ALK Universal), with a 6ohm resistor replacing the woofer; second amp fed trough a Cabre AS45 active crossover, low-pass 460Hz, driving the folded bass horns; plus a subwoofer plate amp driving a Beyma 15inch driver in a bass reflex enclosure for frequencies under 50Hz.Sounds good - even tho I use the cheapest amp I could find on the bass horns at the moment, as i'm in trial period
I took some RTA measurements with some app on my iphone - I understand it's very basic but it gives an idea and correlates what I'm hearing.
It sounds better than with the passive first order slope between bass and midrange, for sure
I did some trials with a full active set-up but there was no apparent benefit ( the amp feeding the mid and treble horns has more than enough headroom for a domestic use, even when fed full-range...) and I couldn't stand the electronic colouration and the loss of resolution the active crossover was bringing to the mid and high ranges. it sounds much better like it is now!!!
All I need is a decent amp for the bass - the el cheapo 80's akai integrated i'm using there at the moment sounds decidedly muddy down there.
So I feel I might just be very lucky, and having a crossover frequency lower than 500Hz helps for the set-up, I'm sure, but if there are phase or timing issues, i certainly cannot hear them, and they don't seem to appear on my very basic measurements.
Here's what it looks like in the sweet spot:
Edits: 09/14/16Follow Ups:
I've used pro amps, specifically a SoundTech A1000 to drive passive subs with great results. I would assume it would work just as well here driving the bass drivers, plenty of grunt with very quick transients. The trick is to find a pro amp without a noisy fan.Have you considered vertical biamping with a pair of stereo amplifiers?
I've been biamping, triamping, active, passive, you name it for decades, it started with my car system back in the 70s.
With that said my ears tell me I get the best results in my home with a passive vertical arrangement, what many consider "fools biamping", their term for any kind of passive biamping. With vertical passive biamping the stereo amps are arranged in a quasi mono block setup, only with stereo amplifiers.
One amplifier uses one channel to drive the woofer and the other channel to drive the mid & tweet. The same with the other amp on the other side. With this arrangement all of the benefits of using a mono block setup are realized plus the added benefits of further divorcing the high frequency drivers from the woofers signal path. Not to mention the sonic and monetary gains of having speaker wires 18" long.
I'm currently using two modified Dynaco ST-120 amps to biamp a modified set of Klipsch Heresys to great affect. Anyone thinking Heresys are bass shy needs to take another look. And the gains in articulation are not subtle.
Martin
In the above pic I have my Heresys sitting on top of a pair of Dayton Sub1200s, plenty of bass without them, but to get that last bottom octave the subs will pick up any slack. With the subs only coming online at 52hz and below, the Heresy sound is preserved, ONLY BIGGER. And they make great speaker stands elevating the Heresy to the perfect height.
Edits: 09/17/16 09/17/16 09/17/16 09/17/16 09/17/16 09/17/16
It is the best of the limited number of amps I have tried on them.
I did connect a FIRST WATT J2 to them for awhile and that sounded good but not very powerful.
The CRESTs look toy like but they have tonal complexity - they do not make all sound liek sine waves.
And here's what it looks like measured 1m from the left speaker, axis of the midrange horn
Phase and timing issues dont seem to be that audible below 500 or so. Look at the KHorn. 3 or 4 feet difference between the mid and the bass, and a big difference between the mid and high, too.
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