Can someone recommend reliable amps and speakers...?

[Rob_Beech]

And yet correct in others.

 

I think the issue with Roberts post is that is it a simple statement made without reason. There is nothing within the statement to back up WHY this should be done and how far this should be taken, however alot of us have mentioned this afterwards.

 

2 Examples, in which we shall use 1 pair of 15 + 2 tops, and a pair of 1 x 18 reflex subs. The tops are rated at 300 + 100 and the subs are rated at 600. All figures rms. The active crossover used will be 3 way and we shall crossover at 100Hz and 1Khz. (no need to comment on crossover points or power ratings this is purely an example). Each section is 8ohms.

 

Example 1 : Amplifiers which match 600watts 300watts and 100 watts are used. Analogue crossover is used. On a large gig we have to use all the systems headroom to keep a suitable volume throughout the venue. At times we get a peak and an amplifier clips. At the end of the night you have a compression driver not working. The Amplifier clipping has destroyed it.

 

Example 2 : Ampilfiers are rated at 1.5 times the rms power (900 + 450 + 150). a Digital Crossover with compression and limiting features is used. the same venue, the same overall volume. The peaks are within the amplifiers headroom so no clipping occurs. The system is no louder, but the amps are not working as hard, and there is headroom in the system for short peaks.

 

Heres the bit that people forget, the crossover has a slow attack limiter set at a level that theoretically matches the rms ratings of the boxes. This means that peaks above this will be allowed to keep the dynamic range of the system, but if someone starts pushing the system so it is going above this level constantly then the limiting will activate and prevent this from happening.

 

I think it goes without saying that a 1000watt amp on a 100watt speaker is over the top. However a 1000watt amp on a 100watt speaker and a limiting device is acceptable. This is what some hire companies will do, they will have a stack of amps all the same (all rather large) which are capable of driving any of the boxes they have in hire stock, they will then use processing as necessary to limit them to the necessary power for the boxes they are driving on that occasion.

The D&B D12 does this internally along with the rest of the processing, it is 750watts at 8ohms and yet when setup correctly doesn't put 750watts into a pair of E0's.

 

Rob

[StevieR]

This is what some hire companies will do, they will have a stack of amps all the same (all rather large) which are capable of driving any of the boxes they have in hire stock, they will then use processing as necessary to limit them to the necessary power for the boxes they are driving on that occasion.

This is exactly what we do. We have pretty much standardised on a couple of Lab amps for most of our stock. Our dedicated Fohhn system processors have a feature that allows them to sample the output from the amplifiers connected and, based on the loudspeakers selected, it will work out the clip points and set the maximum signal that it will allow to be sent to the amplifiers. It also allows complete flexibiliy as to which brand of amplifiers you wish to use (unlike d&b).

 

Steve