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Amp for running 6x Oberton XB1500

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Post Options Post Options   Thanks (0) Thanks(0)   Quote njw Quote  Post ReplyReply Direct Link To This Post Posted: 13 October 2018 at 10:35pm
Originally posted by ceharden ceharden wrote:

As per the other Chris's comment, in the absence of very expensive power measurement and/or processing, the best way to avoid blowing your system up is to use your eyes, ears and common sense.

I use clip limiters set slightly above the maximum output of the amplifier so it can achieve maximum Voltage swing but stops it the signal turning into a complete square wave!  However ultimately the limiter is me.  If I'm just tickling the limit lights occasionally then I take that to be the system running at maximum level. If I start seeing more than a brief flash every few seconds then it's time to turn it down.  The only difference is if I do leave a system unattended then I'll normally wind the limiters back a few dB to a more conservative level and probably increase the release time too.

As for the question of how much headroom, well it depends of course!  Mainly on the style of music.  I do a lot of live work and for that I like lots of headroom because of the high crest factor, especially on mids and highs.



 I'm much the same, I do mostly dj nights but always run a desk between the dj mixer and lms and keep on the eye on the levels as the night goes on with maximim level being the point at which I'm getting the odd flicker of the limiter lights. If I need to leave the system the levels get pulled back a few db and the lid goes back on the desk! Smile
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 14 October 2018 at 12:27am
Originally posted by Jo bg Jo bg wrote:

-thermal limiter , very attack long times, maybe 5 6 seconds under 100Hz, kicks in only when the threshold is reached for a long time, so only with high duty cycle/low crest factor  program.

It wont work. After bass ends limiter will reset and count attack again. It may not turn on at all. Also limiter turning on after few second  of bass would be annoying. Device has to have memory.

What are the maximum temperatures you see on powersofts?
How does it change with copper VC, aluminium and CCAW?


Edited by gen0me - 14 October 2018 at 12:28am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 14 October 2018 at 12:32pm
How powersofts know ωL part of impedance measuring music signal?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 15 hours 52 minutes ago at 5:37pm
Originally posted by toastyghost toastyghost wrote:

Your drivers will still be able to be burned by 300-600w LONG TERM power. The rating alongside a driver is measured in ‘easy conditions’ with band limited high crest factor pink noise. It is not a real representation of power handling apart from in maybe a well tuned reflex box.

Originally posted by junoprobelaunch junoprobelaunch wrote:

Didn't see that last bit just got confused as to how we got on the topic of of how much power kills your drivers again. Allow me to check my understanding though... so when you connect a driver to an amp output and run power into it (say the amp gives out 1500watts),the driver resists the very vast majority of that and will only see a few hundred Watts tops? I assume the crest factor plays a part in this but am I correct in saying the above? 

You can separate speaker impedance into
ωL + Re + ~0.4%*Re*ΔT

Of which first one is inductance which affected returns power to amp. Second and third is resistance which affected changes this electrical power into heat and sound. (0.4% [Ω/°C] is temperature coefficient for copper.). You can read value of ωL from speaker impedance chart. As you know Re, rest is ωL for given frequency. 

For Vamp coming from the amp 
I=Vamp/(ωL + Re(1 + 0.004ΔT)

So power that speaker converts would be:
I*U for important resistances. R=U/I
Keep in mind manufacturers dont care about temperature coefficient. So their rating is way higher.

So knowing 2 of the following: safe voice coil temperature, voltage limiter, power limiter, 3rd one can be calculated assuming conditions in speaker are already stabilized(long term). At least for the same design.



Edited by gen0me - 15 hours 36 minutes ago at 5:53pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote junoprobelaunch Quote  Post ReplyReply Direct Link To This Post Posted: 11 hours 44 minutes ago at 9:45pm
Sorry gen0me, you've completely lost me Confused Why is that formula needed ? As in what does it actually show? I can gather a rough idea from the context but I'd ideally like more than just a rough idea ! You've also used some symbols that I've simply never encountered before such as ωL, ΔT and while we're at it what is Vamp? (the voltage an amp gives out ??).

Hard not to feel like an imbecile but I am so desperate to fully understand this that despite feeling as such, I simply have to ask. TIA
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 10 hours 52 minutes ago at 10:37pm
Originally posted by Timebomb Timebomb wrote:

Originally posted by toastyghost toastyghost wrote:

Originally posted by csg csg wrote:

in rough terms, peak limiters will protect your drivers from physical damage ( pole plating, hitting X-mech etc), RMS limiters will protect from thermal damage.

using peak limiters alone will not stop you during voice coils, and if used poorly can actually significantly increase the long term average power sent to your drivers.

without top of the range limiting, you have to think old skool - good driver / amplifier matching and listening to your rig when it is running - if it sounds happy it usually is...


And a good manufacturer does testing to set peak, RMS and also thermal, Xmax and power limiters to handle all situations, ideally with frequency shaped filtering too so that it can vary with signal content like a real speaker does.

This is currently an area I’m doing a lot of work on Timebomb - been a long time since we met, perhaps we should have coffee soon?


Yeah bob in if your up this way, im normally about,  i will do some more refined presets for my systems when the new processors are ready but its looking like the new year now... 


Doing an install in Preston sometime in the next few weeks so might make the extra hop up. Will send you a message
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Post Options Post Options   Thanks (1) Thanks(1)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 10 hours 41 minutes ago at 10:48pm
Originally posted by junoprobelaunch junoprobelaunch wrote:

Sorry gen0me, you've completely lost me Confused Why is that formula needed ? As in what does it actually show? I can gather a rough idea from the context but I'd ideally like more than just a rough idea ! You've also used some symbols that I've simply never encountered before such as ωL, ΔT and while we're at it what is Vamp? (the voltage an amp gives out ??).

Hard not to feel like an imbecile but I am so desperate to fully understand this that despite feeling as such, I simply have to ask. TIA


He's writing equation salad really to express a pretty simple concept.

If you want to know the amount of power reflected to an amplifier then you need the phase angle of the load and a little bit of simple trigonometry.

When an enclosure presents a non-resistive load to an amplifier, i.e. the bandwidth around a resonance or when the voice coil inductance becomes significant compared to the DC resistance then a proportion of the power delivered at those frequencies is reflected back to the amplifier and must be dissipated as heat. This is on top of the waste heat related generated by an amplifier being not 100% efficient that is already being disposed of. In my opinion this is important and is one of the primary factors as to why certain amplifiers are more reliable than others at sub. Generally the resonances when driving such cabinets are low, the power levels high, reflected power proportion with the wrong cabinet load could be enough to tip a design over the edge. It also depends a lot of your musical content. So a lot of variables all bunched up together.

The problem is that unless you know what you are doing and spend a lot of time with measurement gear then you'll never really know the numbers, although quite a lot can be inferred from an impedance graph of your enclosures.

Frankly it is not worth worrying about in the real world unless you have a particular fascination with making the measurements. You'd also have to integrate them over time and frequency to get real power figures making it all rather complex (no pun intended). It is something that interests me and one day I may try and get real numbers, but it'll take years to get around to.

People have given good advice. Buy decent units, run the system sensibly, use your eyes and ears. Set the limiters to keep the amps out of clip, use a good gain structure. There really is not a lot to it imo.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote junoprobelaunch Quote  Post ReplyReply Direct Link To This Post Posted: 10 hours 27 minutes ago at 11:02pm
Originally posted by odc04r odc04r wrote:

Originally posted by junoprobelaunch junoprobelaunch wrote:

Sorry gen0me, you've completely lost me Confused Why is that formula needed ? As in what does it actually show? I can gather a rough idea from the context but I'd ideally like more than just a rough idea ! You've also used some symbols that I've simply never encountered before such as ωL, ΔT and while we're at it what is Vamp? (the voltage an amp gives out ??).

Hard not to feel like an imbecile but I am so desperate to fully understand this that despite feeling as such, I simply have to ask. TIA


He's writing equation salad really to express a pretty simple concept.

If you want to know the amount of power reflected to an amplifier then you need the phase angle of the load and a little bit of simple trigonometry.

When an enclosure presents a non-resistive load to an amplifier, i.e. the bandwidth around a resonance or when the voice coil inductance becomes significant compared to the DC resistance then a proportion of the power delivered at those frequencies is reflected back to the amplifier and must be dissipated as heat. This is on top of the waste heat related generated by an amplifier being not 100% efficient that is already being disposed of. In my opinion this is important and is one of the primary factors as to why certain amplifiers are more reliable than others at sub. Generally the resonances when driving such cabinets are low, the power levels high, reflected power proportion with the wrong cabinet load could be enough to tip a design over the edge. It also depends a lot of your musical content. So a lot of variables all bunched up together.

The problem is that unless you know what you are doing and spend a lot of time with measurement gear then you'll never really know the numbers, although quite a lot can be inferred from an impedance graph of your enclosures.

Frankly it is not worth worrying about in the real world unless you have a particular fascination with making the measurements. You'd also have to integrate them over time and frequency to get real power figures making it all rather complex (no pun intended). It is something that interests me and one day I may try and get real numbers, but it'll take years to get around to.

People have given good advice. Buy decent units, run the system sensibly, use your eyes and ears. Set the limiters to keep the amps out of clip, use a good gain structure. There really is not a lot to it imo.


That was much more helpful! Don't mean to be ungrateful to Gen0me but i feel like the above needed to be read before I understood what you meant. Yes, when you put it like that there isn't alot too it but when phrases such as "burning out your voice coils" and "expensive recone bills" are used to describe a concept, I just had to make sure I understood it 110%. Thank you
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 10 hours 14 minutes ago at 11:15pm
Originally posted by junoprobelaunch junoprobelaunch wrote:

Sorry gen0me, you've completely lost me Confused Why is that formula needed ? As in what does it actually show? I can gather a rough idea from the context but I'd ideally like more than just a rough idea ! You've also used some symbols that I've simply never encountered before such as ωL, ΔT and while we're at it what is Vamp? (??).

Hard not to feel like an imbecile but I am so desperate to fully understand this that despite feeling as such, I simply have to ask. TIA
Vamp is the voltage an amp gives out.
Δ = delta = difference.

This is to show how much power of an amp that was supposed to give kW is really being taken by the speaker just in standard working conditions.
ΔT is the difference of temperature. Lets say ts parameters were measured on ambient temperature speaker in 20°C. Than when voice coil heats up to 120°C its resistance will grow by ΔT* temperature coefficient. So for copper voice coil that has temperature coefficient ~ 0,4%=0.004 [Ω/°C] and ΔT=100°C the Resistance will grow to Re + 100*0.004Re= 1.4 Re

I would love to give some real world example but for this you need to ask powersoft users about power limiter setting, max vc temperature, speaker used and cabinet. Can live without power limiter setting.

Also using above formula, test signal and 1 or 2 multimeters. Or instead of multimeters audio input connected to the pc you can figure out temperature of the voice coils during your gig.

ωL - L is the inductance. ω is traditionally named angular frequency. Important part is ωL is inductance of the voice coil at given frequency. Inductance + resistance(Re) = impedance. Which is seen on the charts of loudspeaker manufacturers.


Edited by gen0me - 10 hours 8 minutes ago at 11:21pm
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