Bi-amping Basics

[Hibernator69 47]

Setup: 2-M1.0t bi-amping my towers. Pre-amp line out to RCA splitter to power amp on each channel.

 

Does it make a difference whether you use one amp for the woofers and the other for the mid/high or one amp per tower (say L channel is woofer, R channel is mid/high)?

 

I've tried both and can't say I notice any difference, other than maybe turn off thump and click (but that may have to do with my new power sequencer and whether I have the sequence backwards or not).

[jazzman53 1,280]

I think it does make a difference whenever the music demands high power output.  And I think it's best to have the bass on one amp channel and the mids/highs on the other channel of the same amp (vertically bi-amp'd).  The premise here is that bass frequencies typically require more power, and even though there are separate power caps for each channel, ultimately both channels are supplied by a common transformer; thus, the portion of the total power not being drawn by the mids/highs channel would then be available to the bass channel.     

[zumbini 6,153]

Another viable option is to vertically bi-amp but reverse L and R on either the tweeters or woofers.

(One amp drives the L mids/highs and the R lows; the other drives the R mids/highs and the L lows.)

[Hibernator69 47]

OK, makes sense and was kind of thinking that could be true. That probably also means I've got to re-check my AC connections and startup/hut down sequence. Started getting loud clicks/thumps when I set it up vertical, but I also hooked up a Furman PS-8R (15amp version, no 20 amp circuits in my movie room) at the same time. This is dumb, but I can never remember if its amps on first or last. Picked up two of the PS-8Rs for an avg $80 delivered recently, but just started using the first one yesterday.

[zumbini 6,153]

I start my preamp 1st, then EQ and XO, then sources, then amps. I reverse that sequence for shutdown. 

[Hibernator69 47]

LOFO - last on first off

 

I've doing FOLO and that probably explains it then. Somehow got it in my head I need to make it nice and quiet (I.e. shut everything else off) before turning off the amps ... The rest followed from there.

 

 

[Papajoe 221]

I always have gone by the power amp 'on' last and 'off' first. I learned my lesson when I was setting up the mixer for one of my wife's Spring Performances. The theater had a pair of M1.5 Ts powering their array and I turned the mixer 'off' before the tech had turned the amps 'off'. The loud 'click' brought the stage manager running out of the wings saying some very descriptive language. From that point on I always double checked that the amps were off first, even at home.

But, now that I am using the 12V trigger on the TG IV to start and stop my Furman sequencer. When I hit the TGIV 'on' button, it trigger the Furman to powers up 1,2,3. But, when I power down the TGIV, the Furman uses the same sequence 1,2,3. That worried me a lot until I gingerly tried to power down the amps with the TGIV still on and found that it does not matter. I think that the TGIV has a clamping circuit that shuts down the output as soon as the power button is pushed.

Papajoe

[Hibernator69 47]

Can you explain the last part again? How is it that the 12v trigger reverses only the Furnman's power down sequence? And what is a clamping circuit (which power button do you mean, the master Furman on/off on the front, or the amp's own power switch)?

 

My new receiver has 12v triggers and I hadnt noticed whether the Furman PS-8R (not II) has them, but that would be cool to be able to do the whole she-bang with just one remote control click.

[BarryG 2,859]

I think when I get my amps MKII mods done, I will try the verical bi amping to see how that works with one M-500T to each speaker One channel for Highs and other for Lows.  But after I get my M1.0T with Option two.  I will use that for the Lows and One M-500T for the Highs.  Either way, I am still investigating active crossovers to add, looking at a few on ebay and Craigslist.  I am leaning towards an Ashly, ony other ideas?  This will be for my newly rewired Magnepan MG-3a's!

 

[zumbini 6,153]

My new receiver has 12v triggers and I hadnt noticed whether the Furman PS-8R (not II) has them, but that would be cool to be able to do the whole she-bang with just one remote control click.

Yes, your Furman PS-8R has barrier strip connections for a 12 volt trigger.

Just keep in mind that it's rated for 15A and Carver amps can draw that much in-rush current (briefly) on start up.

If you don't push them too hard you can probably get away with powering 2 amps as long as you delay one of them. 

(I only use my PS-8R II to power accensories [EQ, XO] and sources [cassette deck, 2 CDPs, TT, tuner].)

[zumbini 6,153]

...I am still investigating active crossovers to add, looking at a few on ebay and Craigslist.  I am leaning towards an Ashly, ony other ideas?....

Ashly and Rane both make highly rated crossovers but you can get a Behringer with the same functionality for 1/2 the price.

The Behringer is less likely stand up to professional use on the road, but I've found them more than adequate for home use.

 

If you plan to use equalization you should take a look at a digital loudspeaker management system like the Behringer DCX2496.

It has 3 ins/6 outs, selectable XO slopes (6-48dB/oct), independantly configurable graphic AND parametric EQs, and lots more.

[Papajoe 221]

Zumbini and Hibernator-

The Furman PS-8R II has multiple ways to trigger the unit. The TG IV has a 12 V trigger signal that goes on and off with the power. They talk different languages, meaning different uses of the 12 V. In order to have the two unit talk to each other, I used a 12 V relay to do the translation.

As for the power handling capabilities, I have PS-8R II which can handle 20 Amps. I am using the unit in this way: step: '1' powers up 2- M4.0Ts, step '2' powers up my Sunfire Sub and step '3' powers up 2 more 4.0Ts. I actually was powering up the 2 Silver 7Ts this way also. Because of all the power in the Carvers, with all the units on and running at theater volume, I am drawing only 10 Amps. I did not find that out till I actually measured the amp draw. It surprised me.

Papajoe

[zumbini 6,153]

According to the rear panel and owner's manual the PS-8R (II) is rated for 15A. 

 

 

 

I copied these specifications directly from Furman's website: 

Current rating:	15 amps
Operating Voltage:	90 to 140 VAC
Over Voltage Shutdown:	140 VAC typically
Spike Protection Modes:	Line to neutral, zero ground leakage
Spike Clamping Voltage	188 VAC peak @ 3,000 Amps, 133 VAC RMS (tested to UL-1449 and USA / CIDA A-1-1, 6,000 VAC @ 3,000 Amps)
Response time:	1 nanosecond
Maximum surge current:	6,500 amps
Noise attenuation:	10 dB @ 10 kHz, 40 dB @ 100 kHz, 100 dB @ 10 MHz Linear attenuation curve from 0.05 - 100 Ohms line impedance
Dimensions:	1.75” H x 19” W x 10.5” D.
Weight:	11 lbs. (5 kg.)
Construction:	Steel chassis, .125” brushed and black anodized aluminum front panel; glass epoxy printed circuit boards
Power consumption:	6 watts
Safety Agency Listings:	CE, NRTL-C

 

[Nahash5150 10,984]

The 15A is continuous current, so max continuous load shouldn't be more than 11A if we use the root-mean-square law for total safety. So I certainly wouldn't connect more than two 1.0t's or M-500t's on that thing.

 

If you're using a few amps, you're going to have to deal with cycling them on because as Z pointed out, the in-rush currents are very high. Just be sure to keep ALL your gear grounded to the same point with about equal power cord lengths to avoid ground looping. It's a big mistake to use separate outlets on different breakers if those wire runs are far apart or run at different lengths. No wire is zero ohms, so the best you can do is match the impedance by 'daisy chaining' grounds and connections. IMO it's best to plug your high power stuff right into solid copper (the wall), and manually turn each one of them on. Or, you can use a power sequencer with big relays.

 

The more stuff you use the more complicated things get, so use caution. I can't imagine the crap Z must go through setting up a clean live environment... 

[zumbini 6,153]

The more stuff you use the more complicated things get, so use caution. I can't imagine the crap Z must go through setting up a clean live environment...

Amen brother! That's why sound checks can take longer than shows, and why sound techs are 1st in and last out.

[Hibernator69 47]

Haven't turned it off yet tonight, but I switched around the plugs:

 

 

Plugged in the front: cheapo BD-player temporarily

No delay:

- Pioneer SC1522k receiver and aTV3

First delay:

- NHT SA-2 sub amp and DirecTV box

Second delay:

- M1.0t

Third Delay:

- M1.0t

 

Didn't know where to stick the TV in all this, so it's going into a different AVR into a different wall outlet. The aTV and the DirecTV should probably be in an in switched outlet and I would like to use the 12v trigger on the Pioneer to turn on and off the other amps at least (start the sequence forward and backward).

 

Eventually I can see a good BD player being added to the list. More big amps are possible if I score the NHT 2.9 or 3.3 speakers, since that means I could move my 2nd pair of VT-2s into the movie room and would want another pair of M-500/M1.x or something to drive them (PM1.5 viable here?).

 

Should I just stick the smaller and always on items like aTV, DirecTV on the other AVR and reserve the Furman unit for the Pioneer receiver and big amps?

[Papajoe 221]

Z-

When I purchased the Furman, there were two offered a 15 amp one and a 20 amp one. The 20 amp one what I got.

As for the power draw:I am not sure what speakers you guys are pushing or how loud you are playing them. My system is comprised of all Vandersteens and, with the surround sound running and the listening level perfect for me, my four M4.0Ts never go higher than the bottom two lights on the power meters.

To keep this in perspective, my theater is only 8' X 12', so not much power needed. The volume level on the TG IV is usually in the range of '35' to '28' . So, not much power being used; but, lots more if I need it.

Papajoe

[Hibernator69 47]

I'm going to show off my 4th grade electrical grid knowledge for a minute here:

 

Don't you have to have a 20 amp circuit with the special wall outlets to use the PS8R II (20 amp version)? That, and the fact I got a great price on the 15 amp version is why I bought it.

 

My M1.0ts also never much blink above the 2nd light bi-amping the VT-2s. The Pioneer receiver handles the rest of the speakers and the NHT SA-2 amp isn't even turned up halfway. That one suprised me a little, but I used the Pioneer's autosetup, so maybe I could have turned up the sub amp higher and the Pioneer would have just compensated for it. Will have to check, lol, maybe it is compensating for it being turned down so low.

 

 

 

[Papajoe 221]

H.-

Yes, that 20 Amp one has the funny looking plug on the end.

When I started using the Carver amps, I installed a dedicated 20 amp breaker and ran a new line to feed the 20 amp receptacle that I put in the floor behind the cabinet. So, I was ready when this one arrived.

Papajoe

[Hibernator69 47]

This is a picture of my TFM-35, but it pertains to the question at hand.

 

 

 

 

In my listening room I've got my M4.0t driving the VT-2 full range right now, but feel there's not enough base.  I have used the TFM-35 in addition to the M4.0t in various bi-amp and sub/sat configs.  Someone touched on balancing output levels and the issue of the built in crossover freq in another thread.  I think that's making more sense to me now.  Here I just wanted to discuss some of the cabling options:

 

- connected to the inputs right now is a splitter that I would hook up to my old Denon AVR-3600 sub out (internal crossover set of whatever Denon offered that was closest to 125 Hz.  I know this will result in some signal loss, but I can get it to sound pretty good and it's not too hard to match loudness for sub and sats the way I feel is good.

 

- the cables laying out (used some black tape to show right vs left channel, oops, forgot to to black on one of the connectors at the splitter) are how I could bi-amp using only the built-in pre-amp outs.  In this case though (I haven't actually tried this with these two amps, but it is *exactly* how I've set up the 2 M1.0ts in the movie room), balancing the output level depends pretty much all on the dial on the front of the TFM-35.  Also in this case I think putting the M4.0t on the sub would make things easier. But I just can't get past thinking the M4.0t is supposed to sound like some kind of heavenly unobtainable tube amp ... why am I not trying to use it to where I can benefit from this?  So I prefer to have the TFM-35 drive the subs and the M4.0t drive the mid/high.  Now we're slinking back into the active crossover/DSP thoughts from the other thread though I think.  Hmm, I'll have to give the Behringer dbx2496 a try maybe.  Haven't really done much more than unpack it, was really bought to help with a long term DIY project.  If I understood correctly from the other thread I would set a LPF at 150 HZ or so (above where the VT-2 internal LPF is) and a HPF somewhere around 100Hz (below the internal HPF setting).  I can probably mess with signal levels too to balance the output power.  If this works well, is there a cheaper solution I can insert here so I can put the 2496 back into my DIY workroom?

 

 

 

 

 

[zumbini 6,153]

When I purchased the Furman, there were two offered a 15 amp one and a 20 amp one. The 20 amp one what I got.

I've been using Furman products since the late 70's and that's a new one on me Joe.

Perhaps you have a PS-PRO or PS-PRO II. Does it have a key switch on the front panel?

 

 

[zumbini 6,153]

 

 

This is a picture of my TFM-35, but it pertains to the question at hand. 

 

 

- the cables laying out...are how I could bi-amp using only the built-in pre-amp outs.  In this case though...balancing the output level depends pretty much all on the dial on the front of the TFM-35.  Also in this case I think putting the M4.0t on the sub would make things easier. But I just can't get past thinking the M4.0t is supposed to sound like some kind of heavenly unobtainable tube amp ... why am I not trying to use it to where I can benefit from this?  So I prefer to have the TFM-35 drive the subs and the M4.0t drive the mid/high.  Now we're slinking back into the active crossover/DSP thoughts from the other thread though I think.  Hmm, I'll have to give the Behringer dbx2496 a try maybe.  Haven't really done much more than unpack it, was really bought to help with a long term DIY project.  If I understood correctly from the other thread I would set a LPF at 150 HZ or so (above where the VT-2 internal LPF is) and a HPF somewhere around 100Hz (below the internal HPF setting).  I can probably mess with signal levels too to balance the output power.  If this works well, is there a cheaper solution I can insert here so I can put the 2496 back into my DIY workroom?

 

I would have no qualms about using the M-4.0t to drive your subs. If nothing else give it a try and let your ears decide.

 

I assume that dbx2496 is a typo and you actually have a Behringer Ultra-Drive Pro DCX2496.

That's a nifty little processor, the Swiss Army Knife of  crossovers, with lots of EQ options built-in.

The problem is that it has SOOO many options that it takes a bit of getting used to.

 

If you don't want to "waste" the DCX2496 for this application pick up a Behringer CX2310 for $80-100.

It's a 2-way stereo/3-way mono electronic crossover that'll do HP/LP and provide gain trim for each band.

 

[Hibernator69 47]

 

 

I would have no qualms about using the M-4.0t to drive your subs. If nothing else give it a try and let your ears decide.

I assume that dbx2496 is a typo and you actually have a Behringer Ultra-Drive Pro DCX2496.

That's a nifty little processor, the Swiss Army Knife of crossovers, with lots of EQ options built-in.

The problem is that it has SOOO many options that it takes a bit of getting used to.

If you don't want to "waste" the DCX2496 for this application pick up a Behringer CX2310 for $80-100.

It's a 2-way stereo/3-way mono electronic crossover that'll do HP/LP and provide gain trim for each band.

 

 

Yes, the Ultradrive Pro. Caught the $199 Xmas time sale!!! Thought dbx was odd, DCS LOL.

 

Thanks for recco for the smaller Xover. Saw it, but wasn't sure that's what I needed. For $80 that's a pretty easy way to go ... except for the whole XLR thing. Hmm, buy adapters, make adapters, buy Carver Pro amps. WWWOCCDD?

 

I've had the M4.0t on the subs and the TFM-35 of the sats (probably only using sub preout, not beamed). Sounds better than the other way around. Guess I was just expecting the M4.0t to turn my speakers into some kind of audio nirvana. Actually did notice something new in a familiar recording once recently. That kind of did surprise me.

[Hibernator69 47]

 

 

 

When I purchased the Furman, there were two offered a 15 amp one and a 20 amp one. The 20 amp one what I got.

I've been using Furman products since the late 70's and that's a new one on me Joe.

Perhaps you have a PS-PRO or PS-PRO II. Does it have a key switch on the front panel?

 

 

 

This one:

 

http://www.furmansound.com/product.php?id=PS-8R

[zumbini 6,153]

Thanks for recco for the smaller Xover. Saw it, but wasn't sure that's what I needed. For $80 that's a pretty easy way to go ... except for the whole XLR thing. Hmm, buy adapters, make adapters, buy Carver Pro amps. WWWOCCDD?

My C-11 has balanced outputs. If your preamp is single-ended you have a few choices:

1.  Buy (or make) appropriate RCA to XLR adapter cables to get in (1 pair) and out (2 pairs) of the XO.

While this is the simplest solution, and it works MOST of the time, it can result in a ground loop.

No way to know for sure until you try it....

 

2. Purchase a crossover with RCA inputs and outputs that is designed for consumer audio.

Sounds easy but they are often hard to find (DBX), relatively expensive (Marchand), or require DIY skills.

 

I've owned a couple Audio Control Richter Scales designed to add a subwoofer to an existing full range speaker.

They come up on ebay pretty regularly for $80-150 (original model) and $160-250 (Series III).

The original offers 2 XO frequencies (100Hz and 600Hz), a 1/2 octave EQ and warble tone generator.

(You'll need the original condensor mike, or equivalent, to take advantage of the built-in analyzer.) 

 

 

 

The Series III can be adjusted for any XO frequency using readily available plugin resistor modules.

The unit I bought in the 70's came with 80 and 120Hz chips and a postcard you could send in to get a 3rd chip free.

Most of the units I see on ebay don't mention the 2nd module but often it's taped to the PCB inside. 

(Again you'll need the original condensor mike, or equivalent, to take advantage of the built-in analyzer.) 

 

 

 

 

3. Convert your preamp to balanced outs with an internally mounted PCB (about $30 worth of parts).

Here's the circuit and PCB BillD designed for my C-2 and C-11. (I have a parts list too if you are so inclined.) 

 

 

 

4. Add an external balance box (aka DI or direct-interface box) to convert from single-ended to balanced.

Before I switched to a balanced peramp I used this Aphex Model 124 to feed my balanced EQ and XO.

I still use it to feed the output of my SD/A 490t CD player into my PA system. (Without it she hums like crazy!)