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Lower Driver Impedamce

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Tonskulus View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tonskulus Quote  Post ReplyReply Direct Link To This Post Posted: 13 June 2019 at 11:29am
And at lower driver impedance, maximum voltage will decrease. 

There is actually a design flaw in Tamp TA-series amplifiers. It has built-in limiter but it only works for 8ohm load / ch to prevent clipping.
When using 4ohms, amplifier will clip way before limiter kicks in because limiter itself has no idea about speaker output or rail voltage drop - it is only set to limit the input to a specific value which seems to be very accurate @ 8ohm loads and it works pretty well too! It barely never clips yet giving full power.

At 2ohms / ch.. even worse. Good limiter should take account the actual output too. 




Edited by Tonskulus - 13 June 2019 at 11:31am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 13 June 2019 at 1:45pm
Originally posted by gen0me gen0me wrote:

Originally posted by Timebomb Timebomb wrote:

I dont understand what you mean by "Dont calculate crest factor of a bassline/peak. Calculate crest factor bassline/sineWink"
You set up soundsystem so rated power is your 0db level. So this is your level to which you compare. Not peak voltage level which is higher. It is a comparrison of power not voltage.

I wrote sine but in fact it is not exact sqrt(2) factor. You see on K10 spec(126V*sqrt(2)~=178V not 200V)
It will be more like undistored peak to rated power factor.
Originally posted by snowflake snowflake wrote:

"The problem is the more distored and less sine looking bass waveform is - the weaker it is percived on same output."

no, quite the opposite.
Make a track with sinusoidal bass on 0db. Distort it add some compression etc. You will have to bring the levels down so overally bass will be percived more silent.


yeah, but when you play it on a system the distortion will mostly not go through the subs but through the kicks/mids. so even if the mastered track has a lower normalised bass level, you can just increase the gain relative to the other track so that the bass amps are still reaching max.

apart from that, the reduction in volume on the mastered track so that the added distortion does not lead to the voltage exceeding the normalisation threshold, is insignificant compared to the perceived increase in loudness from the distortion - this is both becuase of the steep slope of the fletcher-munson curve below 200Hz, and the psycho-acoustic perception of missing fundamental.
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Chris Grimshaw View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chris Grimshaw Quote  Post ReplyReply Direct Link To This Post Posted: 14 June 2019 at 9:45am
Originally posted by Timebomb Timebomb wrote:

Originally posted by Chris Grimshaw Chris Grimshaw wrote:

Originally posted by Timebomb Timebomb wrote:

No,  Basslines in real music pretty much always have a higher crest factor than a sinewave, they are pretty much never between a sine and a square wave, always a high crest factor than a sine.

The tune mentioned that was described as having continual sine wave when actually analysed did not,  it has dynamic, like practically all music.

Can you point me to a tune that features these mythical long drawn out sinewaves?  Ive looked, but never found one..


Kaiju - Hunter.

36Hz sine wave, but it's compressed, which adds a bit of harmonic content. IIRC, the crest factor below 100Hz is <2dB.
If you wanna cook drivers, that's my go-to.

Chris

Just analysed it,  with lowpass at 100Hz 24dB then normalised to 0dB its 6.4dB crest factor in the heavy bass section, if i hard limit at -1dB so it is slightly clipping then normalise to 0dB again its 5.39 dB crest factor across the heavy bass section, there are short bursts of around half a second that get down to about 4dB crest factor.

If you just look at the waveform you can see it does not have as high a duty cycle as a sine wave, there is some dynamic to it.  

  


Interesting. I saw someone use WaveLab (IIRC), and it reported about 2dB crest factor. Maybe they only analysed a few cycles of maximum amplitude, though, which would give that result.

Thanks for the sanity check.

Chris
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www.grimshawaudio.com
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 14 June 2019 at 7:18pm
Originally posted by snowflake snowflake wrote:

yeah, but when you play it on a system the distortion will mostly not go through the subs but through the kicks/mids. so even if the mastered track has a lower normalised bass level, you can just increase the gain relative to the other track so that the bass amps are still reaching max.
Never tested it on full soundsystem. Always only on 1amp+ fullrange. Im curious. Could be a challenge concerning it will be harder to get the same integrity of sound on crossover 80-150hz than on home audio 600Hz.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote U.Viktor Quote  Post ReplyReply Direct Link To This Post Posted: 18 June 2019 at 1:11pm
the thing is that almost *ALL* amp circuitry are based on some type of half-bridge topology (for simlicity & cheapnesss) which operates +/- rails referred to the Ground.
Unfortunately the power stage devices suffering 2V_output + 2V_drop Voltage stresses which means if you need let us say: 200V_peak output and you have '0.9 modulation capability' (due some losses in filters & semiconductors + wiring)
the effective device Voltage stress will be 200V * 1.1 * 2 = 440V
And here I did not even mention that rails would drop, not small (!) especially on low frequencies.
Switching 440V in this "Two level structure" (or above) with 50-100A @250-350KHz (which frequnecy IS required for good accurate signal reproduction) IS a problem even with today fastest semiconductor devices.
There are tricks to solve the issues like using SiC MOSFET or deploy some soft switching, but all has downsides.
Also the two +/- rails could easily go to unbalanced conditions <low-frequency, large signals!> which affects the output signal quality. All Powersoft K, X series, LabGruppens, Crown I-techs suffersing the same unfortunate event!

I better like PKN's approach with already full-bridged circuits, they have a single rail in the XE series (NO bridge ability) but everything always balanced, no rails over/undershoot issues. The H8 went even further on the same path..

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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 18 June 2019 at 5:24pm
Any H8 actually been used on a gig yet?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jammin75 Quote  Post ReplyReply Direct Link To This Post Posted: 18 June 2019 at 8:11pm


see where u goin on the way to a gig LOL



Edited by jammin75 - 18 June 2019 at 8:13pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tonskulus Quote  Post ReplyReply Direct Link To This Post Posted: 18 June 2019 at 8:38pm
Originally posted by U.Viktor U.Viktor wrote:

the thing is that almost *ALL* amp circuitry are based on some type of half-bridge topology (for simlicity & cheapnesss) which operates +/- rails referred to the Ground.
Unfortunately the power stage devices suffering 2V_output + 2V_drop Voltage stresses which means if you need let us say: 200V_peak output and you have '0.9 modulation capability' (due some losses in filters & semiconductors + wiring)
the effective device Voltage stress will be 200V * 1.1 * 2 = 440V
And here I did not even mention that rails would drop, not small (!) especially on low frequencies.
Switching 440V in this "Two level structure" (or above) with 50-100A @250-350KHz (which frequnecy IS required for good accurate signal reproduction) IS a problem even with today fastest semiconductor devices.
There are tricks to solve the issues like using SiC MOSFET or deploy some soft switching, but all has downsides.
Also the two +/- rails could easily go to unbalanced conditions <low-frequency, large signals!> which affects the output signal quality. All Powersoft K, X series, LabGruppens, Crown I-techs suffersing the same unfortunate event!

I better like PKN's approach with already full-bridged circuits, they have a single rail in the XE series (NO bridge ability) but everything always balanced, no rails over/undershoot issues. The H8 went even further on the same path..


Behringer Inuke 6000 and 12000 has also fullbridge output stages so these amps cannot be bridged anymore.  But yes, bus voltage pumping is common issue in (poorly designed) half-bridge class-D topologies.  Well, one trick is to invert one channel (180deg) out of phase but this is only suitable for stereo/2ch amp having exactly the same signal going through both channels. 



Edited by Tonskulus - 18 June 2019 at 8:41pm
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simo69 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote simo69 Quote  Post ReplyReply Direct Link To This Post Posted: 10 July 2019 at 10:09pm
E90 Mc2 will power a pair of 21DS115 at 4oms per channel

Edited by simo69 - 10 July 2019 at 10:13pm
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