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Bridge mode and damping factor
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Points: 8128 		Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357- Quote  Post ReplyReply Direct Link To This Post Posted: 15 May 2020 at 1:01pm
Originally posted by Jo bg Jo bg wrote:

Still I see bridge operation as a compromise to get more sound for the buck, not a quality choice.


I would say sound quality is a factor of amp build quality, even when bridging.

IMHO, if you choose an amplifier rated at 2500wpc at 4 ohm stereo, and compared it with 2x Crest CA18s in bridge, you may actually be surprised with the difference in sound quality and accuracy from the Crests.
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Originally posted by Mikkel Mikkel wrote:

Edit: no i see where ive cocked up. You would need 8x 12" driver to load the amp the same as 2x 18" in bridge. But again the moving mass is still a factor i think.

Exactly, the two sides of the equation are the sink capability of the amp, and the total moving mass (and hence back EMF) from the drivers.

Less drivers = less moving mass = less back EMF
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Originally posted by Jo bg Jo bg wrote:

To MikkeI, I was comparing same driver in different configurations, with different drivers many variables will come into play, surface alone is not enough, you need to account for the whole speaker parameters.
Still I see bridge operation as a compromise to get more sound for the buck, not a quality choice.
Also damping factor seems more an hifi concern than a modern PA issue to me.




Fair enough, it makes sense there are more variables involved. From a laymans perspective the number of drivers hooked up to an amp=less cone control, but as you say it seems a moot point in the world of pa. I full agree with you that bridge is a compromise. Stereo nets you less power per driver and less DF but less amp stress and more SPL.
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Originally posted by Jo bg Jo bg wrote:

Still I see bridge operation as a compromise to get more sound for the buck, not a quality choice.
Also damping factor seems more an hifi concern than a modern PA issue to me.

Not my experience, and Lev would seem to concur. Best quality bass I have ever achieved has always been when using bridge mode. My theory is it's because of the damping.

Originally posted by levyte357- levyte357- wrote:

Back when I used to bridge amps, (Dec 2019 LOL), my weapon of choice was the QSC RMX 5050.

Many, many times bridged these across many modern 5" VC, 1kw+ drivers, and obtained some of the smoothest, fullest bass tones, with monumental SPL, control, sound quality, never ever going anywhere near clip.

Not even the illustrious Powersoft K20, driving 2x cabs per channel, could match the sound obtained, from 2x bridged 5050s.

But as you said before, you can achieve the same result, damping wise, by under loading the amps, which does have the added benefit of headroom.

Horses for courses I guess we all have our own way of doing things, it's the results that count. Thumbs Up


Edited by Sonic the hedge - 15 May 2020 at 2:24pm
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Mikkel View Drop Down
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When you say quality you mean spl right? 4x drivers in stereo would give the same spl as 2x 18 in bridge on the same amp but less stress. Leaving cost aside bridging feels like a compromise to me at least. But each to their own i guess.
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[/QUOTE]

Horses for courses I guess we all have our own way of doing things, it's the results that count. Thumbs Up
[/QUOTE]

Exactly Tongue
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Originally posted by Sonic the hedge Sonic the hedge wrote:


Not my experience, and Lev would seem to concur. Best quality bass I have ever achieved has always been when using bridge mode. My theory is it's because of the damping.


IMHO, I think if bridging sufficiently large amplifiers on sub, you gain not compromise in sound quality, from much increased headroom.

Just compare quality 5K amps in bridge across 2x cabs each, with 1x 2500wpc amp @ 4 ohms stereo, set to just about clip, and the difference is very, very tangible.

Also piece of mind, from never, ever clipping drivers, is priceless.

Obviously ideal solution, is buying monumentally powerful amps, at 4 ohm stereo, but not all that is promised by many modern amps, is delivered.


Edited by levyte357- - 15 May 2020 at 3:18pm
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Originally posted by Mikkel Mikkel wrote:

When you say quality you mean spl right? 4x drivers in stereo would give the same spl as 2x 18 in bridge on the same amp but less stress. Leaving cost aside bridging feels like a compromise to me at least. But each to their own i guess.

Of course SPL, but also control, tightness, transient performance, sustain of long notes. Bass performance is incomplete without any of these IMO

But of course that's just my opinion - sound quality is a subjective issue, so it depends what you are trying to achieve.
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Originally posted by levyte357- levyte357- wrote:

IMHO, I think if bridging sufficiently large amplifiers on sub, you gain not compromise in sound quality, from much increased headroom.

Just compare quality 5K amps in bridge across 4x cabs, with 1x 2500wpc amp @ 4 ohms stereo, set to just about clip, and the difference is very, very tangible.

Also piece of mind, from never, ever clipping drivers, is priceless

Agreed - headroom is very important too

Which brings me to a second point - for the same amp, bridging increases available headroom, because it presents a 100% symmetrical, balanced load on the amp's PSU.

When bridged, the caps in the two halves of the PSU (A channel and B channel) are loaded positive and negative in turn, one after the other, rather than both both being loaded positive or negative at the same time, as is the case when running dual channel. When in bridge mode, the caps recharge faster (because the cap charging load on the rectifier/SMPS is also thereby balanced) end result - more reserve when the next note drops.

I have never bench tested this, but I have seen test results claiming a 20-30% improvement, in PSU voltage stability, in bridge mode Vs dual channel.




Edited by Sonic the hedge - 15 May 2020 at 3:42pm
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I still don't get it.
As a cost limited option maybe, but talking just about sound quality, bridging opposed to single channel operation will rise distortion and Lower damping factor.
Obviously if your amp runs out of headroom  in single channel mode it could be better bridged, but we are talking about a suboptimal situation in this case.
As long the amp has enough headroom not to clip in single channel, why should the bridged option be better(maybe, like for subs, people like the grunt of more distorted sound)?
Note that I use 4 ohm sub drivers, to go 1 per  channel and get enough power. 
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Originally posted by Sonic the hedge Sonic the hedge wrote:

Originally posted by levyte357- levyte357- wrote:

IMHO, I think if bridging sufficiently large amplifiers on sub, you gain not compromise in sound quality, from much increased headroom.

Just compare quality 5K amps in bridge across 4x cabs, with 1x 2500wpc amp @ 4 ohms stereo, set to just about clip, and the difference is very, very tangible.

Also piece of mind, from never, ever clipping drivers, is priceless

Agreed - headroom is very important too

Which brings me to a second point - for the same amp, bridging increases available headroom, because it presents a 100% symmetrical, balanced load on the amp's PSU.

When bridged, the caps in the two halves of the PSU (A channel and B channel) are loaded positive and negative in turn, one after the other, rather than both both being loaded positive or negative at the same time, as is the case when running dual channel. When in bridge mode, the caps recharge faster (because the cap charging load on the rectifier/SMPS is also thereby balanced) end result - more reserve when the next note drops.

I have never bench tested this, but I have seen test results claiming a 20-30% improvement, in PSU voltage stability, in bridge mode Vs dual channel.



you can achieve the same effect even in stereo mode, reverse the input and reverse again the output on one side, isn't it? 
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A lot of amps, for example lab gruppen and powersoft and many more, do this already by design. No Benefit when bridging these in comparison to dual channel with the same signal.
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