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Amps with Adjustable Crossovers/Bi-Ampable?
- Thread starter Count Bassie
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Well I'm glad I asked... Lol seriously, hadn't thought about the actual distance a note has to travel through that horn before it gets realized by a set of ears...
the variablilty of the phase response inherent in the inbuilt variable active crossover is way over my paygrade. As far as the intended range of the folded horn goes, BFM specifies a low cross for the placement in PA application. His own passive filters for bass guitar back line stacks are more like 150hz. They rise in sensitivity progressively through the low mids which would tend to get honky if too high a crossover point is used.
Not an integrated head, but the old Ashley PB41 pres had a crossover -- will have to check the frequency range. Some power amps do -- the DSP ones, obviously, but even the simple Crest ProLites will let you run each side full range, sub-100 Hz, or 100 Hz on up -- you can do that with any pre or using the head of your choice as a preamp.
I haven't tried the GK amps bi-amped. Might have to give that a shot. The 1001 needs a GK cab but sounds like the 800 RB does not -- is that correct?
And a merry Christmas to all.
I haven't tried the GK amps bi-amped. Might have to give that a shot. The 1001 needs a GK cab but sounds like the 800 RB does not -- is that correct?
And a merry Christmas to all.
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Yes the 800RB does not need any special cab, only that you do not go under the 8 ohm minimum on the 100 watt amp. The other RB's were better ID'ed as H.M.S. (Horn Management System) than Biamp (except the 2000RB). The internal crossover is set at 5KHz, non adjustable to the smaller horn amp (50 watt @8 ohms, 75 @ 4 ohms) accessible from the 2+,2- connection of the speakon ONLY. With the HMS heads the "Boost" control does NOT go to the horn amp keeping it clean (as dirt in horns sounds pretty bad).
Passinwind
I know nothing.
- Dec 3, 2003
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31.5Hz-3.1KHz, second order. And it's actually the Ashly BP-41. Link Removed
I guess "bass preamp" makes more sense than "peanut butter" in this case, ho, ho, ho.
Okay, had to read it a few times. 100W @ 8 Ohms up top, 300 W @ 4 Ohms down low, adjustable crossover or full-range mode, using one or both amps.
GK amps (Chili Peppers) were a big part of the sound in my head as I was starting to play, but back then I was more a 75 Watt Gorilla combo kind of guy.
An older friend had a big GK stack that was great but seemed unfathomably massive and excessive at the time (not sure of the head, but the cabs were GK). Then I stopped playing for a long time -- when I started again, six years ago, stuff like the 800RB wasn't in vogue, but I might owe it to myself to track one down and experience directly what I only heard as a teenager. I did try an old 2000RB for a few days when I was starting up again -- sounded righteous, but it hadn't been taken care of and seemed to be on its last legs, or else I'd have bought it.
Not a "head" but if you go with a pre/power combo, the Crown XLR series power amps have an adjustable built-in crossover. I have an XLS 1500 that I pre with an all-tube SVP-Pro. From the manual:
"Crossover Mode: When using the “Crossover Mode”, the amplifier is configured to use a LowPass Filter on Channel 1 and a HighPass Filter on Channel 2."
"Crossover Mode: When using the “Crossover Mode”, the amplifier is configured to use a LowPass Filter on Channel 1 and a HighPass Filter on Channel 2."
I'm always a little wary of running a dedicated subwoofer for backline support...you're better off using a simpler full-range system and re-assigning the sub to FOH duty. That being said, it does sound like a fun project but, as others have pointed out, there are elements of application which need to be considered.
Checked my gear and I have (4) pieces which have variable crossovers...but none are dedicated bass heads: H&K preamp, Rane DC24 compressor, Crown Drivecore power amps, and a dbx DriveRack. The DriveRack is kinda cool because it offers the aforementioned variable crossover(s), delays, slopes, and pass filters. They're also dirt-cheap on the secondhand market in the advent of newer technology. They're more easily installed in a preamp (or mixer) / power amp configuration.
As far as setting delays, I believe the procedure goes like this if using a DriveRack or similar device:
*Set your crossover at 100 hz. The default slope is usually LR24.
*Reverse the polarity on one of the two enclosures, not both.
*In some way / shape / form, pipe 100 hz (I use a CD) through the system. Balance the volume between the 210 and T24.
*Now, slowly add delay to the top 210 enclosure. You'll know you hit the sweet-spot when the combined volume drops dramatically which indicates the the enclosures are aligned but 180 deg from one another. This creates profound cancellations, nulls, voids which can easily be detected by ear. The procedure may take a few delay sweeps to pinpoint and repeatedly reproduce the nadir. It's also a good idea to position yourself a healthy distance from the enclosure array.
*Correct the polarity so both enclosures are in-phase and you're good to go.
Riis
Checked my gear and I have (4) pieces which have variable crossovers...but none are dedicated bass heads: H&K preamp, Rane DC24 compressor, Crown Drivecore power amps, and a dbx DriveRack. The DriveRack is kinda cool because it offers the aforementioned variable crossover(s), delays, slopes, and pass filters. They're also dirt-cheap on the secondhand market in the advent of newer technology. They're more easily installed in a preamp (or mixer) / power amp configuration.
As far as setting delays, I believe the procedure goes like this if using a DriveRack or similar device:
*Set your crossover at 100 hz. The default slope is usually LR24.
*Reverse the polarity on one of the two enclosures, not both.
*In some way / shape / form, pipe 100 hz (I use a CD) through the system. Balance the volume between the 210 and T24.
*Now, slowly add delay to the top 210 enclosure. You'll know you hit the sweet-spot when the combined volume drops dramatically which indicates the the enclosures are aligned but 180 deg from one another. This creates profound cancellations, nulls, voids which can easily be detected by ear. The procedure may take a few delay sweeps to pinpoint and repeatedly reproduce the nadir. It's also a good idea to position yourself a healthy distance from the enclosure array.
*Correct the polarity so both enclosures are in-phase and you're good to go.
Riis
That's more than I can do at this point, but maybe I can work out a way to do it. Of not, and it doesn't work out, well it's another duct-tape-and-ratchet-strap solution!
Happy holidays!
Happy holidays!
Little overboard, eh? Not terribly practical given your needs. I would stick with a preamp / poweramp for maximum flexibility, though. A dedicated bass amp with biamp capability may appear to be the way to go but what if you find the preamp section is a real dog? The majority of the newer power amps have DSP which provides the desired control and are cost-attractive...think Crest, Crown, Peavey, etc. Complement with a secondhand preamp of choice and you'll have the power-on-tap and tonal options that you prefer. Don't care for a particular preamp after all? Sell it / trade it for another without sacrificing the entire rig.
Riis
All great advice. I'm just trying to live within meager means though; I recently scored an old QSC US850 from Craigslist that had been through a House fire, for $70! The thing works, and the front panel is all kinda burned and crusty black so there is a funky cool-factor here...
I do have my Trace 250SMX head, non-bi-ampable, but could just go get a Rolls Tiny Crossover, and voila, minimalist/Spartan bi-amp rig. I just have access to a few things via a trade deal that I've got pending, which presents a few possibilities, so I thought I'd pose a question or two.
One possibility is a Hartke 5000, which would be enough power (BFM horn-loaded cabs don't need massive power) and actually ain't a bad amp anyway. But I get the power amp thing. I should find out if the QSC has a crossover, but I don't think it does.
This is a correct procedure but it has an assumption built in that all components are in polarity to begin with. Usually a pretty safe bet when using the same brand and series of speakers but not when mixing brands.
Additionally various crossover designs have different phase and polarity artifacts. As I mentioned with the GK 2000RB, flipping the polarity of one of the speakers may be beneficial. In my use, I was using two identical 12s and had confirmed they were polarity matched. Flipping the polarity of one of the speakers made a noticeable increase in bass response. Using disimilar drivers may produce different results.
you seem to confuse polarity with phase response. No assumption resides in the procedure. It works for any and all combination of reversed leads speaker wiring and phase response.
It's my conjecture that your success in flipping polarity on proven matched cabs indicates your amp or a cable was miswired.
old QSC had filter dip switches iirc. You have to wonder how hot it got in the fire and how that might be a failure in waiting.All great advice. I'm just trying to live with means though; I recently scored an old QSC US850 from Craigslist that had been through a House fire, for $70! The thing works, and the front panel is all kinda burned and crusty black so there is a funky cool-factor here...
I do have my Trace 250SMX head, non-bi-ampable, but could just go get a Rolls Tiny Crossover, and voila, minimalist/Spartan bi-amp rig. I just have access to a few things via a trade deal that I've got pending, which presents a few possibilities, so I thought I'd pose a question or two.
One possibility is a Hartke 5000, which would be enough power (BFM horn-loaded cabs don't need massive power) and actually ain't a bad amp anyway. But I get the power amp thing. I should find out if the QSC has a crossover, but I don't think it does.
You do have some kind of crossover on board the Trace. The fx loop can send a highpass. It has just gone through the high compessor at that stage. Afaik it's a parallel blend back at the front panel knob so setting that at nil would leave the bass coming from the Trace amp. Fire the fx send to the QSC and see what gives.
I agree and disagree with BFM.
Assume a 100 hz crossover
Here's where I disagree.
A 100 hz wavelength is a little over 10 feet long. Sound travels a little over 1 foot per millisecond. A five millisecond delay between the high range cabinet and subs will put them almost 180 degrees out of phase at the crossover point. 100 Hz falls about midway between G and G sharp. I believe a bass player would easily notice if the speakers in his rig were 180 degree out of phase in this range because the notes around 100 hz would be greatly diminished in level and response of the system would be extremely uneven in this range.
Here's where I agree.
From the audience perspective the misalignment will be far less noticeable when the performance is indoors. The reason is because as the distance between the listener and the speakers increases, the listener begins to hear more and more secondary reflections and less direct sound. Because the secondary reflections travel a longer path than the direct sound, it creates multiple phase problems that tend to mask the improper alignment in the crossover region.
I believe if one was running a system outside (where one hears primarily direct sound), the 180 degree misalignment at 100 hz would be readily apparent in an A/B test to anyone with a decent ear. Outside of an A/B test few people would notice, but I would personally do my best to properly time align the subs and mains anyway. YMMV
