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Author Topic: Subwoofer amps - what are we REALLY hearing?  (Read 30423 times)

Alexander B Larsson

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Subwoofer amps - what are we REALLY hearing?
« on: February 05, 2008, 11:11:42 am »

I am still searching for that "big amp" for the bass boxes, but the more I read, the more contradictory the information seems...
I currently run a number of older "conventional PSU" Labgruppen amps, but having one bridged amp per driver is HEAVY!  Confused

(Finding amps for listening tests is somewhat hard in Sweden, as many of the MI shops carry only entry level stuff, like Phonic, Alesis etc.)

Normally one can find some general trends in opininons/reviews of stuff, but amps seem different? Strange, since they should actually have the smallest impact on overall fidelity of the rig, from a distorsion point of view.

Some praise the QSC RMX 4050 and 5050 for subs, while some claim their upgrade from RMX to some "switched" Crown, Lab or similar made a world of difference. Listening test (shootout) says the differences are small, but that test only included few speakers, etc...

Considering our ear's limited sensitivity to detect distorsion in the bass range, what IS it that we hear?

A guy I talked to described the lightweight Lab amps as "punchy" in the bass, but are we talking about that amp adding something that was not originally there? Or are many other amps missing the "punch", whatever that would be?

Power is clearly important, but amps that run below their clipping point should not colour sound at all, at least not detectable...

/Alexander
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Duncan McLennan

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #1 on: February 05, 2008, 11:22:54 am »

I've personally always like amplifiers with real toroidal transformers and linear power supplies.  Switching amps, although convenient for weight purposes, have never sounded as good to my ear.  That might be just me.

So is weight worth sacrificing sound quality?  I don't know.
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Nathan Schwarzkopf

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #2 on: February 05, 2008, 12:26:48 pm »

Hay alex

I have beat this to death in my own head and a little on this board as well.

I have tried a ton of different "solutions".  

I started with a rmx 5050-linear- and in my case they turned out to be total junk and sounded like ass.  So I switched to the plx 3402-switcher- Which at the time I thought I had found THE amp.  Then I discovered the 8001-linear- and guess what I fell in love again. Then came the 9200-switcher- and now I am on 10001's-linear.

We are currently in an ongoing debate about this in the shop with MC2 and 8001's also.  What it really boils down to IMO is that every am will "color" the sound.  I feel that the switchers do it less than the linear's but in some cases it is almost a desired effect.  I am on the linear boat again on the low end because there just seems to be more drive and guts for lack of a better description.  Your just going to have to take stuff out for a spin and see how ya like it.

Nathan
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Scott Smith

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #3 on: February 05, 2008, 12:46:52 pm »

Alexander B Larsson wrote on Tue, 05 February 2008 11:11

I am still searching for that "big amp" for the bass boxes, but the more I read, the more contradictory the information seems...

Yes...there does seem to be a lot of "contradictory" information out there.  

I went from a PLX3402 amp to a PL6.0 running stereo...and at any level I hear better dynamics and get punchier bass.  While I know the PL6.0 has a much beefier power supply, no one has ever been able to technically explain why this amp has a damping factor of 2000.  All people will say is that this figure is just "marketing hype" and means nothing.  Is it possible the figure is the result of the beefier power supply?

My feeling regarding this issue IS NOT supported by anyone here, or the stack of technical facts that can be provided against my beliefs.  But I know what I hear...so do most people using this amp, or other big ones like it.
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Bennett Prescott

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #4 on: February 05, 2008, 12:57:50 pm »

You have to be using the right kick drum mic to go with it, of course.

My advice: Run the biggest amp you can.
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Chuck Fry

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #5 on: February 05, 2008, 01:09:11 pm »

Scott Smith wrote on Tue, 05 February 2008 09:46

While I know the PL6.0 has a much beefier power supply, no one has ever been able to technically explain why this amp has a damping factor of 2000.  All people will say is that this figure is just "marketing hype" and means nothing.  Is it possible the figure is the result of the beefier power supply?


That damping factor is only relevant if you have the driver connected directly at the amplifier's output terminals. Use any length of cable and it's degraded. I tend to agree that high damping factors are primarily marketing hype and of little practical use.

My limited understanding is that the damping factor is more a result of a high feedback factor, and minimal impedance between the output stage and the terminals, than it is a function of the power supply.

I would love to see someone do double-blind testing of power amps at the next sub shootout.
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Scott Smith

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #6 on: February 05, 2008, 01:23:03 pm »

Chuck Fry wrote on Tue, 05 February 2008 13:09

...My limited understanding is that the damping factor is more a result of a high feedback factor, and minimal impedance between the output stage and the terminals, than it is a function of the power supply...

Ah yes... but isn't the job of the amplifier to ultimately get the power (from the power supply) to the speakers with the least amount of resistance and loss?
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Ryan Lantzy

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #7 on: February 05, 2008, 01:27:27 pm »

Scott Smith wrote on Tue, 05 February 2008 13:23

Chuck Fry wrote on Tue, 05 February 2008 13:09

...My limited understanding is that the damping factor is more a result of a high feedback factor, and minimal impedance between the output stage and the terminals, than it is a function of the power supply...

Ah yes... but isn't the job of the amplifier to ultimately get the power (from the power supply) to the speakers with the least amount of resistance and loss?


I hate to even acknowledge this with a reply... but here goes.

FOR THE LAST TIME, THE DAMPING FACTOR OF AN AMP CAN DO NOTHING TO IMPROVE THE DAMAGE THE COPPER IN BETWEEN DOES TO THE DAMPING FACTOR!

It's VERY simple math.  Look into it.
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Ryan Lantzy
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Scott Smith

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #8 on: February 05, 2008, 01:33:45 pm »

Reply as loud as you like...  I already said my belief is NOT supported. Cool
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"Percussive Maintenance" - Bang on it until it works!
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Alexander B Larsson

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #9 on: February 05, 2008, 01:46:21 pm »

Thanks for all the replies!

Don't you find it frustrating that we in this case not can quantify what we hear? And that amps that on paper are indistinguishable still do not sound the same, even within their linear operation (as in no clipping/current limiting).
Or do we fool ourselves - how big are the differences?

A few years ago I had the opportunity to pick up either of two Labgruppen amps for my bass guitar rig. One Lab 1000 or one Lab 1300. They are VERY close in spec, with most of the design the same, except the power supply. (The 1000 is a conventional and the 1300 is switched.) The price was the same, making the 1300 a bargain, as it is normally more expensive. However, there was no doubt the two bottom octaves where better with the Lab 1000.

And I have to carry the 20 or so extra pounds every time I move the thing...

/Alexander
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