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Gain, power and volume - a confusing ménage à trois...


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#91 alexclaber

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Posted 06 October 2015 - 09:48 AM

View PostSafetyman, on 12 August 2015 - 07:53 PM, said:

Chris b,

Distortion of the signal ( clipping )means ,effectively, that the speaker cone gets not one, but two commands from the amp at nearly the same time. This causes heat to build-up as the cone ends up not moving in either direction, due to the two opposing signals it receives all the time it's in clipping mode. As the cone is a piston, moving vast amounts of air which keep it cool, it loses the ability to move air. This makes it overheat, leading to it's destruction. If you like, effectively like a short-circuit in electrical wiring.

Cheers

Just in case anyone reads this, the following bit is 100% incorrect:

"Distortion of the signal ( clipping )means ,effectively, that the speaker cone gets not one, but two commands from the amp at nearly the same time. This causes heat to build-up as the cone ends up not moving in either direction, due to the two opposing signals it receives all the time it's in clipping mode."

NOT TRUE AT ALL!!!

However, this is kind of correct: "As the cone is a piston, moving vast amounts of air which keep it cool, it loses the ability to move air."

It isn't actually the air that the cone moves which keeps it cools, it's the smaller amount of air which is pumped through the motor (the bit at the back with the magnet structure etc) that helps cool the voice coil. But as soon as the woofer cone stops pistoning back and forth whilst still making loud sound (i.e lots of mids and treble, no low frequencies) then the air pump cooling the voice coil stops and things overheat quickly.

#92 Chienmortbb

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Posted 01 November 2015 - 01:01 PM

Alex, Duke le Jeune places his ports to enable chimney effect cooling. Have you tried this, and is there any evidence that is works? If it does of course, the benefit would be that the heat itself causes the movement of air not the low notes.

Edited by Chienmortbb, 01 November 2015 - 01:22 PM.


#93 mikel

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Posted 02 December 2016 - 11:23 AM

After reading the whole thread I am still confused. It seems even the people with relevant qualifications cant agree on what constitute "Gain, Power and Volume".

There again I dont really care. If I like the sound of an amp, and I need it, I buy it.

The way I look at it, leaving all manufacturers nonsense aside, you plug the bass into the amp. There is a volume control next to the input, lets call it the pre amp, for want of a better name. If you leave that at 0 you get nowt out of the amp, regardless of what setting the power amp volume is set at, and vice versa. The way seems to me to get a nice clean sound, regardless of the amps power, is to balance the so called pre and power amps outputs, a little of each. I am using layman's terms throughout this rant so bare with me.

I hear two distinct types of warmth or distortion, call it what you like. Pushing the pre amp means warmth at lower volume, dialing back the pre amp and pushing the power amp stage means a much more fluid and warmer sound at much higher volume. The type that valve amp guitarists love. So you can have two types of nice distortion, quiet and thin, by driving the input stage, and loud and thick by driving the output stage. Weather my names for the amp sections are correct or not its what most none techies call them.

I feel it would make things much easier if cabinet manufacturers would include sensitivity ratings so we had a starting point regarding how much volume any given cabinet and speaker configuration would produce. Power handling is nice to know but If its a really sensitive cab you would know you could get good volume results with a lower wattage amp. Powered cabs have DB ratings on them but surely thats a different thing as they also include the power amp?

#94 markstuk

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Posted 02 December 2016 - 11:45 AM

View Postmikel, on 02 December 2016 - 11:23 AM, said:



I feel it would make things much easier if cabinet manufacturers would include sensitivity ratings so we had a starting point regarding how much volume any given cabinet and speaker configuration would produce. Power handling is nice to know but If its a really sensitive cab you would know you could get good volume results with a lower wattage amp. Powered cabs have DB ratings on them but surely thats a different thing as they also include the power amp?

I think most cab makers give an SPL @ 1watt @ 1m figure. It would be nice if they gave this to us with the source frequency or type of noise (pink/white) ...

For instance my Tecamp 810 has a sensitivity of 105db/1w\1m but it appears to be pretty much identical to my Super12T with 102db/1w/1m. Theoretically the S12 should need twice as much power to sound the same as the 810, but it doesn't
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#95 Bill Fitzmaurice

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Posted 02 December 2016 - 01:39 PM

View Postmarkstuk, on 02 December 2016 - 11:45 AM, said:

I think most cab makers give an SPL @ 1watt @ 1m figure. It would be nice if they gave this to us with the source frequency or type of noise (pink/white) ...
That would constitute truth in advertising, which is an oxymoron of the first degree. Many manufacturers quote sensitivity either in the midrange or at the highest point, which isn't Kosher. Ampeg is one manufacturer that posts accurate sensitivity figures. Since the physics that apply to Ampeg apply to everyone it's a pretty safe assumption that any manufacturer making sensitivity claims substantially different from Ampeg for the same driver configuration are yanking your chain.
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#96 mikel

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Posted 02 December 2016 - 02:43 PM

View Postmarkstuk, on 02 December 2016 - 11:45 AM, said:

I think most cab makers give an SPL @ 1watt @ 1m figure. It would be nice if they gave this to us with the source frequency or type of noise (pink/white) ...

For instance my Tecamp 810 has a sensitivity of 105db/1w\1m but it appears to be pretty much identical to my Super12T with 102db/1w/1m. Theoretically the S12 should need twice as much power to sound the same as the 810, but it doesn't

But they are pretty meaningless figures to the layman. 105 db at 1 watt at 1 mtr????? So assuming I have a 100 watt amp I will be pushing 105 db in my bedroom using next to nothing of the amps power, less than 1 on the volume control. Crank it up to half way and the windows will blow out??? Possibly even the walls.

Edited by mikel, 02 December 2016 - 02:44 PM.


#97 markstuk

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Posted 02 December 2016 - 03:02 PM

View Postmikel, on 02 December 2016 - 02:43 PM, said:

But they are pretty meaningless figures to the layman. 105 db at 1 watt at 1 mtr????? So assuming I have a 100 watt amp I will be pushing 105 db in my bedroom using next to nothing of the amps power, less than 1 on the volume control. Crank it up to half way and the windows w

ll blow out??? Possibly even the walls.

Not really.,.You 're aware that things are quieter the further away they are.. So 1m is a good standardised distance.. And it's pretty easy to calculate what the SPL would be a 10/50/100w. Basically everytime you double the power you add 3dB .. So your 100W amp will do about 125 dB at 1m. It will do very small amounts of dB at 1 km ..
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#98 Bill Fitzmaurice

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Posted 02 December 2016 - 04:48 PM

View Postmikel, on 02 December 2016 - 02:43 PM, said:

But they are pretty meaningless figures to the layman.
True, but if you're here you're not a layman, you're a bassplayer, probably semi-professional, if not a full fledged professional. That makes your gear tools of your trade, tools which you should have a pretty good understanding of. There's no shortage of resources that you can use to improve upon that understanding.
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#99 mikel

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Posted 02 December 2016 - 09:26 PM

View PostBill Fitzmaurice, on 02 December 2016 - 04:48 PM, said:

True, but if you're here you're not a layman, you're a bassplayer, probably semi-professional, if not a full fledged professional. That makes your gear tools of your trade, tools which you should have a pretty good understanding of. There's no shortage of resources that you can use to improve upon that understanding.

I do have a perfect grasp of what I like to hear and what equipment I like to play, its the willfully misleading and needlessly complicated jargon used by amp manufacturers that baffles me, even the qualified on here cant agree. You seem well versed in amp and cab technology so perhaps you can explain to me the difference between valve watts and solid state watts?

I also like to spend my free time actually playing the bass, rather than trawling through technical papers regarding amplifier technology.

Edited by mikel, 02 December 2016 - 09:31 PM.


#100 taunton-hobbit

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Posted 02 December 2016 - 09:32 PM

..........valve watts have more 'heft' ? ,,,,,,,,,,,,
oops

:yarr:

#101 Bill Fitzmaurice

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Posted 02 December 2016 - 10:15 PM

View Postmikel, on 02 December 2016 - 09:26 PM, said:

You seem well versed in amp and cab technology so perhaps you can explain to me the difference between valve watts and solid state watts?
A watt is a watt, 1 joule per second. What makes valve and SS amps different is how they process the signal. At the limits of their output capability valves naturally compress the signal, SS does not. 6dB of compression can subjectively sound the same as a 4x increase in power output. That's why they sound different. You can use processing with SS to emulate what valves do. That's what TC does with their RH 450 and RH 750 amps, which they falsely rated in output based not on how they measured, but how they were perceived. They were rather famously outed for having their thumb on the scale, and while they never quite admitted to the deed, they did put up this:
http://service.tcgro...-management.pdf
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#102 mikel

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Posted 03 December 2016 - 02:56 PM

View PostBill Fitzmaurice, on 02 December 2016 - 10:15 PM, said:

A watt is a watt, 1 joule per second. What makes valve and SS amps different is how they process the signal. At the limits of their output capability valves naturally compress the signal, SS does not. 6dB of compression can subjectively sound the same as a 4x increase in power output. That's why they sound different. You can use processing with SS to emulate what valves do. That's what TC does with their RH 450 and RH 750 amps, which they falsely rated in output based not on how they measured, but how they were perceived. They were rather famously outed for having their thumb on the scale, and while they never quite admitted to the deed, they did put up this:
http://service.tcgro...-management.pdf

Cheers mate, but it still seems from your post that a 100 watt valve amp and a 100 watt SS amp, played through the same cab, would produce vastly different DB levels.

Most consumers buy an amp at least partly based on how many watt's it produces. If the DBs it is capable of producing is governed by how it processes said watt's it would appear to be fairly pointless stating wattage

#103 Bill Fitzmaurice

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Posted 03 December 2016 - 04:38 PM

View Postmikel, on 03 December 2016 - 02:56 PM, said:

Cheers mate, but it still seems from your post that a 100 watt valve amp and a 100 watt SS amp, played through the same cab, would produce vastly different DB levels.
With DSP processing the SS will deliver the same dB levels, at far less cost, size and weight than valves.
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#104 mikel

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Posted 03 December 2016 - 05:58 PM

View PostBill Fitzmaurice, on 03 December 2016 - 04:38 PM, said:

With DSP processing the SS will deliver the same dB levels, at far less cost, size and weight than valves.

Cheers, and DSP processing is.......?

#105 taunton-hobbit

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Posted 03 December 2016 - 07:08 PM

Digital Signal Processing ?
( but I suspect that's not the answer were looking for..................)

:mellow:

#106 Chienmortbb

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Posted 20 December 2016 - 12:23 PM

 taunton-hobbit, on 02 December 2016 - 09:32 PM, said:

..........valve watts have more 'heft' ? ,,,,,,,,,,,,
oops

:yarr:
No they just need more heft to move them. Now let's see who gets trolled more!





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