Loudspeakers - Choosing Speakers

[DaveySimps]

As a rule you want your amps to be 1.8 to 2x the watts of your speakers RMS rating. If you are using active speaker, of course, they have already matched the amp for you.

~Dave

[museav]

Originally Posted by DaveySimps

As a rule you want your amps to be 1.8 to 2x the watts of your speakers RMS rating.

Okay, getting off topic, but let's look at the basis for this. First, although commonly used by many people including some manufacturers, there is actually no such thing as "RMS power". What is really being referenced is the continuous power based on RMS voltage and current but even that is not always the same thing from one manufacturer to another as the time periods and test signals used can differ.

Second, this recommendation is based on touring or rental systems that may be used in a number of different venues and environments and for a wide variety of applications, so it is trying to balance having the greatest output possible available, and thus being able to work for the largest variety of venues and applications, with reliability and durability. But when you are selecting amps for a known application and fixed environment, as is typical with most installed systems, the process is quite different and is based on defining the desired results in the room, adding the desired headroom and backing into the power required for the particular speaker.

So going back to the original topic of how to select speakers, you can pick a speaker and amp and assess what performance is possible or you can identify a desired result and then use that to determine the speaker and amp requirements necessary. One approach is defined equipment and variable results, the other is defined results and variable equipment. Neither is right or wrong but they typically are applied to different situations.

[mbenonis]

Originally Posted by lieperjp

Currently, we are using two 300 watt EV Sx300 speakers(will check product number later) just aren't cutting it. Last night at a rehearsal, the sound guy had to have the vocals clipping for a band to be able to 1) hear the vocals period, and 2) be able to understand the vocals. It sounded pretty bad, too - the clipping was quite noticable.

Let's stop right there. If things were clipping, than he was overdriving the amplifier (or some gain stage before it). So I'd be curious to know what amplifier(s) was(were) powering the Sx300's? Depending on the answer, you might find that an amplifier upgrade is what you really need, and not new speakers.

[waynehoskins]

Originally Posted by mbenonis

Depending on the answer, you might find that an amplifier upgrade is what you really need, and not new speakers.

Though new speakers might not hurt.

Yes, if you're clipping, that's the the loudspeaker not being able to keep up, that's either poor gain structure or insufficient power (which is making you make something clip, being poor gain structure, to try to compensate).

What are the power amps in this case, and what processing is in-between console and amplifiers?

[lieperjp]

We are using a Crown amp, I will find out the type. I didn't see the clip lights on the amp coming on, but then again, I didn't look at the amp until the last ten seconds of the song when it was winding down. I will be sure to check that out tonight at the actual talent show.

[waynehoskins]

Clipping can happen anywhere from the mic pre to the input on the amplifier. It's very likely to happen in a DSP that's set to provide a very low output level for 0 dB input. In that case, you're clipping the A/D in the front end of the DSP, but it's not letting you make it any louder on its output, so you push it harder with the same result. Not that I've ever run into that problem .. oh wait.

[lieperjp]

Ok, so the mains are being driven by a TOA 1000 series P1060D amp.

We are using a Crown XLS602 for monitors. Just thought I'd throw that in there. Just from an initial look at the specs for both amps it seems like this is the better choice for the mains.

Also, for processing - the mics go straight to the board, then directly to the amp. No processing at all. Now that I think about it, could that be a source of the problem? Perhaps inserting a compressor or a driverack would help? (not to mention being a lot cheaper!)

Note: The clipping was constant, not just when the input spiked.

[jkowtko]

Can you confirm where the system is NOT clipping? That sounds like an important piece of info to share since everyone is guessing right now.

If you can AFL (solo) the outputs from the board on your headphones and they sound clean, then for sure it's the DSP/amp/speaker combination.

If, however you can hear the clipping on your headphones at the AFL, then solo the input channel and see how that sounds. If it's not the speakers then you should be able to narrow down where in the mix you have the problem.

[avkid]

Originally Posted by lieperjp

Ok, so the mains are being driven by a TOA 1000 series P1060D amp.

SX300's are most certainly not happy with 200 watts.

The Crown XLS 602 is also not enough for these boxes.
An XLS 802 would be the ticket.

[lieperjp]

Originally Posted by jkowtko

Can you confirm where the system is NOT clipping? That sounds like an important piece of info to share since everyone is guessing right now.

If you can AFL (solo) the outputs from the board on your headphones and they sound clean, then for sure it's the DSP/amp/speaker combination.

If, however you can hear the clipping on your headphones at the AFL, then solo the input channel and see how that sounds. If it's not the speakers then you should be able to narrow down where in the mix you have the problem.

While I cannot say for certain that the amps were clipping, I can say for certain that the mics were clipping at the board.

Perhaps I am thinking of the wrong solution for the problem we are having. The problem is that to get everything - guitars, bass, piano, various percussion instruments, etc. to come out clearly and properly throughout the entire auditorium, they have to be loud. Not overly loud, but loud nonetheless. However, when vocals are added on top of all the instruments, to get the vocals to come through at a loud and clear enough level, both the gain and the volume levels have to be set through the roof. Which then backfires on us because the vocals come in with the scratchy clipped sound. This usually does not happen when it's only one guitar and a vocalist, but it tends to happen more and more as instruments are added.

What we need to be able to do is get the instruments at a level where they can be heard and understood and still be able to have the vocals punch through where they too can be heard and understood. I had assumed that giving the speakers more power would give us more headroom to let the vocals come through. Correct me if I'm wrong.

Now, I'm not mixing this event, but I have mixed events with the same equipment in the same setting. I (or any other mixer) get the levels to where they ideally should be, but it's too quiet, not only in the back but even towards the middle and the front. What is the logical next step for a beginner sound designer like me or the others I work with? Make it louder. So then the vocals (especially the vocals) start to clip. I say vocals because it seems that it's the vocals that clip most of the time - but every once in a while the guitar feeds clip as well.

This is what makes sense to me, but I would be more than willing to admit I'm wrong. For all I know, it could be a simple mixing error. It could also be gain structure. I honestly have never heard of gain structure before, but after reading through a bunch of threads here I understand how important it is. I think I understand how to set the gain structure on the board, but not how to set the gain structure of the system.

Edit: After reading AVKid's response, it might be a good idea to get the right kind of amp and also set the right gain structure before spending anything else.