What is the advantage of bridging two amp vs one big amp?

  1. Please expand I put my reply in the wrong place.
That is because they are better built than hifi stuff. "Pro gear" (more precisely: PA gear) is designed to drive multiple speakers at very high volume for long time periods; these units are therefore very stable and capable of delivering high currents, which is key.


Less impedance (you can't talk of "resistance" with loudspeakers) = more current demand at same voltage. This is where home hifi units fail; most of them just cannot provide the current (see above as well). Therefore, most of them actually will give more power at four ohms compared to eight, but they will break down at two.


What do you mean by "doubling"? Double the rated input power of the speakers?
IMHO, it is key to have an amp whose power rating exceeds the rated input power of the speakers by a margin. Not necessarily because of headroom (headroom is amp-internal only anway), but because of distortions: a transistor amp, driven at its limits, will emit loads of high-order distortions that are infamous for killing tweeters. Since weak amps get to the clipping point earlier, they are actually more "dangerous" to speakers than big ones (if you crank them up that is).


@avionic: no need to grab popcorn; we're all nice here. ;)[/QUOT

The basic principles are all the same whether its hi fi or pro gear etc. Assuming you enjoy high volume listening, a larger than needed amp wont damage a speaker with square wave clipping like an underpowered amp driven into clipping will..
Amps are rated for various loads for instance 100 watts at 16 ohms 200 watts at 8 ohms 400 at 4 and perhaps 1000 in bridged mono...the resistance of the speaker determines what the amp will do..or in some cases some amps have switchable configurations...if you use two 8 ohm speakers on one channel you are presenting the amp with a 4 ohm load on that channel...I do not mean this as anything other than a lighthearted fun disscusion and you seem like a good guy :)
Please understand my intent..
I dont think of this as my opinion it is fact and its called Ohms law...
 
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Crossovers add distortion...bypassing the crossover you eliminated some amount of distortion...
I can speak from my experience. I have 2 Dynaco ST-400 amps that are rebuilt to new condition. I bridged each one for approx. 600w @ 8ohms available running each speaker. Sounded very nice but not as good as I was expecting. To make a long story short, I unbridged them and did a "vertical" bi-amp. In stereo mode, one amp runs the woofers on both speakers, the other amp runs the tweets. It's audio gold and the difference in clarity is amazing.
I don't really understand the technicals about it, but it has something to do with the woofers not upsetting the crossover that's trying to regulate the high pass. All I know is that it works great. Just my $.02
Jim

Edit: It's also nice having separate gain controls for the tweeters to dial them in perfectly. No messing with an L pad
 
That is because they are better built than hifi stuff. "Pro gear" (more precisely: PA gear) is designed to drive multiple speakers at very high volume for long time periods; these units are therefore very stable and capable of delivering high currents, which is key.


Less impedance (you can't talk of "resistance" with loudspeakers) = more current demand at same voltage. This is where home hifi units fail; most of them just cannot provide the current (see above as well). Therefore, most of them actually will give more power at four ohms compared to eight, but they will break down at two.


What do you mean by "doubling"? Double the rated input power of the speakers?
IMHO, it is key to have an amp whose power rating exceeds the rated input power of the speakers by a margin. Not necessarily because of headroom (headroom is amp-internal only anway), but because of distortions: a transistor amp, driven at its limits, will emit loads of high-order distortions that are infamous for killing tweeters. Since weak amps get to the clipping point earlier, they are actually more "dangerous" to speakers than big ones (if you crank them up that is).


@avionic: no need to grab popcorn; we're all nice here. ;)
What Im saying is if your speaker is rated for 100 watts program and its impedence is 8 ohms you can use (within reason) an amp with 100 or more watts at 8 ohms...it doesnt matter what the amps capable of at 4 ohms, or bridged..
 
Except that it's probably "fool's biamping" (pardon my French, it's just the easiest way to describe it) where no crossover has been eliminated.
If you are truly bi amping I assume you arent using the speakers crossover...Are you using an external crossover before hitting the cabinets...just asking so I dont misunderstand or assume..
 
If you are truly bi amping I assume you arent using the speakers crossover...Are you using an external crossover before hitting the cabinets...just asking so I dont misunderstand or assume..

The term biamping is used a number of different ways.

1. Simply using two full range amp channels per speaker through the speaker crossover (low pass and mid/high pass sections separated by removing the jumper straps)

2. Using frequency split before the amps and no or very limited xover in the speakers.

When the term "biamping" comes up on home audio forums more often than not it is type 1.
 
Ye
The term biamping is used a number of different ways.

1. Simply using two full range amp channels per speaker through the speaker crossover (low pass and mid/high pass sections separated by removing the jumper straps)

2. Using frequency split before the amps and no or very limited xover in the speakers.

When the term "biamping" comes up on home audio forums more often than not it is type 1.
I know how it works but I didnt remember you saying how you biamped yours...I wasvtrying to clear up what you did, not the concept itself
 
I ran a pair of bridged Acoustat TNT200 driving my Kappa 9s. Much better than bia-mping them with the same amps in stereo.
That makes total sense in your case..The kappas are rated between 60 and 430 watts between 4 to 6 ohms..the TNT is 200watts at 8 ohms so running the amps in stereo mode they are on the lower side of power spec for the kappas...and probably dead in the wheelhouse when running bridged...The tnt manual I read does not have a power spec for bridged....Crown doesn' t list their bridged spec in many models either..
 
I want to re-emphasis my thoughts in post #7. Bridge amp avoids injection of high signal current into the ground. That's a definite improvement. Of cause a well design ground help a great deal. This is theoretical analysis.

The disadvantage is you need an inverting amp to drive the other half of the amplifier, I am always wary to add any additional circuit in the signal chain.

Another thing about the speaker wire length and size. I did an experiment accidentally ( not intentionally ), but the result is very surprising. Read post #57 of my finding
http://audiokarma.org/forums/index.php?threads/bi-wire-and-bi-amp.750684/page-3

I did not go any further as I have bigger fish to fry........getting my own amp up. But you can see how much 3rd harmonic increased due to the speaker cable and how much I lowered just by doubling up the 7" wire. I have no explanation and I am not about to start a debate against what the manufacturer suggested. Just read post #57 for entertainment.
 
Ye

I know how it works but I didnt remember you saying how you biamped yours...I wasvtrying to clear up what you did, not the concept itself

My comment was in regard to your post #23. Meaning, Jim Marantz is likely using method #1, wherein nothing was eliminated regarding a crossover.


Me, personally, I use a Behringer DCX2496 to send sub/LF via the pair of bridged Crown CE4000s to the pair of SR4719X subs, then low/mids via a QSC PL3.4 to the woofers of SR4732A, and mids/highs via a QSC PL236 to the horns of the 4372A.
 
The advantages of bridging, in my case at least, are quite clear. All of my Yamaha P2200 and P2201 amps, as well as my Yamaha M-2 amp, are good for about ~240wpc into 8ohms when operated in stereo. When bridged, they are each good for 700+ wpc. It's not difficult for me to use up 240wpc and cause the amps to clip, but 700+ wpc has proven to be adequate. The current limiter in the amps kicks in at 2.5ohms. None of the speakers that I use with the amps while bridged have a minimum impedance of lower than 5.7ohms so that is not an issue. The amps are built like bricks are don't seem to have any issues with being bridged. My Yamaha C-80 preamp has inverted pre-outs that help make it easy.

P2200_poweroutput.png
 
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That makes total sense in your case..The kappas are rated between 60 and 430 watts between 4 to 6 ohms..the TNT is 200watts at 8 ohms so running the amps in stereo mode they are on the lower side of power spec for the kappas...and probably dead in the wheelhouse when running bridged...The tnt manual I read does not have a power spec for bridged....Crown doesn' t list their bridged spec in many models either..
They are rated from 60 to 360. They need an amp capable of driving very low impedance loads which is what the Acoustat amps are built for. Roy Esposito who was a principal EE at Acoustat rebuilt/modded the amps for the Kappas. They make about 1100 watts rms in bridged mono according to him. They have no trouble driving the Kappas in either stereo or bridged mode. They are just more dynamic when driven in mono.
 
Apologies if your stuff has been modded, I read the manual for the Kappas and in the spec rundown it says 60 to 430 and the load is 4 to 6 ohms...( is this nominal or is it 4 on bottom 6 on top?? Or neither. If you have any info.)
Same deal with reading the TNT manual....Sounds like a cool rig either way....Id love to have a sit down for a few LP's in front of them...
 
I read the manual for the Kappas and in the spec rundown it says 60 to 430 and the load is 4 to 6 ohms..

To clarify--the specs on Kappa 9's do indeed state 4-6 ohm "nominal impedance". This is borderline on an outright lie--ask anyone who owns them and has looked at the impedance curve. I have a pair here--used to have 3 pair of the monsters--there is an impedance dip down to approx. 0.7-0.8 ohm in the upper 30 Hz range, and another dip to 0.9 ohm at approx. 7 KHz--this is where they get their "amp killer" reputation. I don't care what your amp says it can do at 8 or 4 ohms (bridged or stereo), but what matters is if it is stable into a 1 or 2 ohm load. I have vertically bi-amped mine with a pair of Aragon 4004's in stereo mode, but now use 4 Krell KMA 160 monoblocks--pure class A 160w/8ohm, 320w/4ohm, 640w/2ohm, 1280w/1ohm, and protection adjustable to lower than 1 ohm operation.
 
FWIW, sometimes "nominal" impedance is presumed something along the lines of an average. It's not. A speaker's nominal impedance rating is typically taken from the lowest point just after the resonance peak.

If the speaker has an IEC-compliant impedance rating then the lowest impedance can't be less than 80% of nominal rating.
 
To clarify--the specs on Kappa 9's do indeed state 4-6 ohm "nominal impedance". This is borderline on an outright lie--ask anyone who owns them and has looked at the impedance curve. I have a pair here--used to have 3 pair of the monsters--there is an impedance dip down to approx. 0.7-0.8 ohm in the upper 30 Hz range, and another dip to 0.9 ohm at approx. 7 KHz--this is where they get their "amp killer" reputation. I don't care what your amp says it can do at 8 or 4 ohms (bridged or stereo), but what matters is if it is stable into a 1 or 2 ohm load. I have vertically bi-amped mine with a pair of Aragon 4004's in stereo mode, but now use 4 Krell KMA 160 monoblocks--pure class A 160w/8ohm, 320w/4ohm, 640w/2ohm, 1280w/1ohm, and protection adjustable to lower than 1 ohm operation.
Love to hear what a PLX 3602 would sound like with those....rock solid down to two ohms and sh%t tons of clean headroom...and 30hz filter....
 
Ni
FWIW, sometimes "nominal" impedance is presumed something along the lines of an average. It's not. A speaker's nominal impedance rating is typically taken from the lowest point just after the resonance peak.

If the speaker has an IEC-compliant impedance rating then the lowest impedance can't be less than 80% of nominal rating.
Nice post and I agree...Its a shame the audio industry has gotten away from traditional measurement criteria, in particular RMS...I imagine if in many companies ( not those mentioned on this thread) used ratings like RMS etc. the specs would look a little weak in some situations the marketing claims might be outright lies...again not the products in this thread..they are all above board...I would love to hear what you guys think, or do we just accept "dynamic power for the meaningless stat that it is..
 
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