Class D amps power and headroom

[Israel]

I am very tempted to ask about class d power amps
I am not very technical on electronic devices ,guys, mainly because I have the pleasure to deal with very old equipment (some of them as old or older than me) which in most cases they overpass its manufacturer expectatives sometimes greatly, so I set myself to know how to expect from them by testing it to the limit.

I recently bought a bunch of crown xls amps (the old raw model, i was tempted, very low price dont blame me now I know how Adam felt off grace )

ok here is the reason for the lettersoup off above How a class D amp deal with power??, headroom?? how much power or extra power I need ??? how it compares with other amp clases and pleasee pleaasee any personal experience (amps anon)

they are xls 402 and 602

just reading this deserves a big THANKS guys

[Sydney]

How a class D amp deal with power??, headroom?? how much power or extra power I need ???

Sizing Class D has to take into account the expected dynamic range of the program material that will be reproduced, because it is designed to maximize efficiency NOT to have power reserve waiting.
You would have to determine what sort of crest factor suits your particular needs.
However for some needing 20db+ is not totally out of the question.
This artricle works through scenarios
http://www.synaudcon.com/resources/cont ... fier-size/
Note: In that article the mention of a target 15db crest factor BUT allows for recalculation/variation based upon the program material; explained here:
http://www.prosoundweb.com/article/we_n ... is_needed/
( See notes on page 4 of the article )

Syd

[Israel]

thanks Sydney
reading that and inverting it to the amp that I recently bought which have 300rms@8ohms 450@4 having a 6db crestf (reasonable???) will give me 75w@8 and112w@4 to drive my omnitops this will be more or less 126db @ 8 132@4 per ch
am I right??

[Ron K]

thanks Sydney
reading that and inverting it to the amp that I recently bought which have 300rms@8ohms 450@4 having a 6db crestf (reasonable???) will give me 75w@8 and112w@4 to drive my omnitops this will be more or less 126db @ 8 132@4 per ch
am I right??

a 6db crest is OK for cone drivers on compressed music sources such as CDs tape etc.Live guys usually like a bit more.I know I'm in that 16db crest category for good live reproduction but some guys settle for 10db as they do compress their channels anyways. A lot of it is genre dependent and of course what the guy mixing needs and where he is trying to go with the mix.

One of the associated problems when using or allowing a very high crest is being disciplined enough to not exceed the thermal rating of the drivers since you now have a considerably large amount of available power. You can use peak limiters /rms limiters etc and adjust them to allow the nice high transients without clamping down on the signal however most guys I know who use the high crest factor do not usually use limiters myself included.With care you wont blow drivers but again I stress discipline in levels is paramount or you will end up with a bunch of recone worK!

If I am renting a rig or supplying a BE then I switch on the limiters unless i know the guy turning the knobs has the necessary chops to keep things in order. If you're new to this I'd say use the limiters as an ounce of prevention can be worth a pound of cure.

As for your above calculations they would be correct.

[Sydney]

Got busy, but Ron K took care of the answer

however most guys I know who use the high crest factor do not usually use limiters myself included.

me too

Syd

[Israel]

thank you guys. I use rms limiters, a must, many musicians here dunno how to control them most of the time. as my equipment grow I need to grow also so thats why I asked... I think im covered up to the point i usually work (clubs , Bars, small outdoor activities (thanks bfm cabs are the best)

[Sydney]

Your operating situation ( with the potential of some incompetent misusing the system ) requires protection.
Operators that are in complete control often put limiters only in the portions of the signal path where their control is weakest - including the channel strips where the vocal mics are.
Since mic skills ( or lack thereof ) can have an enormous impact on the level; limiters head the offenders off at the source, rather than clamp at the output. Minimizing any side effects of limiting to just that offender.
And taking an implementation approach of having ample power handling capacity in the drivers, so the drivers are less prone to destruction from overload.

As mentioned a knowledge of the nature of your program material and SPL demands and the capabilities of your system are the determinants.

Syd

[CafSentryGnome]

How well do class H amps handle heavy bass?

[wcriley]

The Gallien-Krueger RB series Bass amps are class H, if that tells you anything.

[Bill Fitzmaurice]

The Gallien-Krueger RB series Bass amps are class H, if that tells you anything.

In truth, it says little. There's much confusion between that which is largely irrelevant, like amp classes, and which is very relevant, like power supplies. High capacity power supplies are required for high current draw applications. Many Class D amps have low capacity power supplies, and that's a limiting factor. But it would be just as limiting with Class H, or for that matter A, A/B, etc. More so, actually, with their lower efficiencies.

[Israel]

behringer ep 2500's are class h i have one and all i can say is that they are efficient versions of a class ab amps... i have a motomaster 400w inverter in my van that can power my ep 2500 to clip at 8 ohms per side ( music)

[energie]

I recently bought a bunch of crown xls amps (the old raw model, i was tempted, very low price dont blame me now I know how Adam felt off grace )

what's wrong with the xls series?

[Israel]

I recently bought a bunch of crown xls amps (the old raw model, i was tempted, very low price dont blame me now I know how Adam felt off grace )

what's wrong with the xls series?

nothing friend it is just that the xti series are better suited for bfm cabs but i like my xls although they behave diffrent than my old class ab amps

[energie]

Oh ok. I'm planning on using the xls 602 since it's cheap good power now that they're discontinued. Just making sure I didnt make a mistake

[Charles Warwick]

it is just that the xti series are better suited for bfm cabs

Most people around here like the xti's for their extra features; since otherwise you would have to buy a separate limiter to place the HP and limiters on the subs.
But if you already have a limiter then the extra features of the XTI's are kind of moot.