PA question

franklern

Right, so say I've got 2 EV sx300 300w 12' speakers, what power amp would I need for them. The same question goes for 300w EV bass bins. I've heard you need twice the amp power for the speakers so i'm guessing 2 2x600w power amps?

Also, does anyone have any idea what are the most powerful (as in loud) 12 inch speakers on the market?

Eoin Madsen

franklern wrote:

Right, so say I've got 2 EV sx300 300w 12' speakers, what power amp would I need for them. The same question goes for 300w EV bass bins. I've heard you need twice the amp power for the speakers so i'm guessing 2 2x600w power amps?

Wattage can be measured in peak, RMS, program, or continuous power. The Peak/Max wattage is twice the RMS wattage. Make sure when you're comparing that you're comparing the same things. You also need to match impedence. 300 watts RMS at 8 ohm is not equal to 300 watts RMS at 4 ohm etc.

If you're comparing like with like, then no, the amp does not need to be twice the power. It should be the same, or slightly more.

Savman

Eoin Madsen wrote:

The Peak/Max wattage is twice the RMS wattage.

Nope, not in the case of those SX300's, they peak @ 1200w
http://www.electrovoice.com/products/202.html

wrote:

"the world's best lightweight, high-power speaker system" with 300 watts continuous, 1,200 watt peak power handling

Savman

franklern wrote:

Right, so say I've got 2 EV sx300 300w 12' speakers, what power amp would I need for them. The same question goes for 300w EV bass bins. I've heard you need twice the amp power for the speakers so i'm guessing 2 2x600w power amps?

I'd recommend sending 500-600w to each of those speakers, both the Tops & Bins, so you'd be looking at a 1000w amp for the Tops and same for the Bins. Trust me bud, you'll get nowhere sending only 300w to an EV Sx300

franklern wrote:

Also, does anyone have any idea what are the most powerful (as in loud) 12 inch speakers on the market?

Er, probably the SX300's!! As with all 12's you're very limited with regard to power and unless you're heading for high end systems (Nexo etc) you cant really get much better than the Sx300. Bear in mind they've a 1" horn, you can get 12" with a bigger horn for more high freq definition if so required but hardly any point unless you want really really big sound and you know what yer doing!

What is this "hypothetical" system being used for? Live music or DJ or wha??

Eoin Madsen

Savman wrote:

Nope, not in the case of those SX300's, they peak @ 1200w
http://www.electrovoice.com/products/202.html

Those speakers aren't 300 watts RMS. Though you're correct, I should have said that peak is twice the program power, not the RMS power - my bad.

I'd suggest using an amp that delivers about 850 watts RMS per side into 8 ohms, since that should match the actual RMS of the SX300s.

franklern

Thanks for the replies lads.

So would an amp like this one be suitable for powering a pair of sx300's?
http://www.musicstorekoeln.de/en/PA_Homerecording/6_70_PAMP2_75_PAH0002832-000/0/0/0/detail/musicstore.html

What's the difference between RMS, continuous and peak wattage and what do they mean in terms of sound quality and loudness?

This system will be used for punk gigs in venues of about 100-300 people capacity, and might also be used for djing in the future. Will there be enough punch in this system for it to be loud even at the back of a venue(loud as in the music is not significantly lower at the back than it is at the front)?

Does anyone know any good books on the subject of sound and PA stuff cos it turns out I know **** all about this sort of thing.

Eoin Madsen

I'd email musicstore and ask them if that's the "RMS" power or peak power that's given. Or something else.

Savman

franklern wrote:

So would an amp like this one be suitable for powering a pair of sx300's?
http://www.musicstorekoeln.de/en/PA_Homerecording/6_70_PAMP2_75_PAH0002832-000/0/0/0/detail/musicstore.html

Yep

What's the difference between RMS, continuous and peak wattage and what do they mean in terms of sound quality and loudness?

Wish I knew. Any "engineer" I've spoken to wasnt sure either, especially when I asked about Program power - but "continuous" and "peak" are fairly self explanatory (ie - just because the speaker's peak output is 1200w doesnt actually mean you'll reach anywhere near that). I dont understand a lot of it meself and on a lot of live sound forums its a regular argument that its very difficult to actually test what output speakers are giving in a live environment and in many cases we have to just take the manufacturers word on it. It's a whole science in itself really and not one you should concern yourself with.

This system will be used for punk gigs in venues of about 100-300 people capacity, and might also be used for djing in the future. Will there be enough punch in this system for it to be loud even at the back of a venue(loud as in the music is not significantly lower at the back than it is at the front)?

Absolutely not buddy. I used that exact system, it's the best of the affordable PA range and the SX300s are like the SM58 of the band PA speaker world. But do not expect transparency to the back of a crowded room, in fact the sound gets very uninspiring after a certain point, unless its a quiet jazz act or somethin but defo not for a live punk band!

Also those EV bins are only 12's also, nowhere near what you'd want for a full sound (that kick just wont cut thru no matter what). Dont get me wrong, its very good gear and very workable to get an entry level sound so long as you understand your limitations.

Does anyone know any good books on the subject of sound and PA stuff cos it turns out I know **** all about this sort of thing.

Ah come on, its t'internet ffs! The information superhighway! Here's a 2 second Google search http://www.google.ie/search?hl=en&q=live+sound&btnG=Google+Search&meta= and if you REALLY want good info check out the Google Groups http://groups.google.ie/groups?hl=en&q=live%20sound&btnG=Google+Search&sa=N&tab=wg

By the sounds of things you want a decent sound so you should looking at different speakers spec sheets and pay particular attention to the Sound Pressure Level (SPL), as a ballpark a speaker with an SPL of 106dB would be nowhere near as "oomphy" as one with say 130dB. That's where you're sound projection comes from so keep it in mind its not all ohms and watts.

Question: do you already have this gear or are you open to other possible set-ups?

Eoin Madsen

Ideally, your venue will be more square and less rectangular. But simply the longer it is, the greater the disparity between the volume at the front and the back. There's not a whole lot you can do about it in a venue of that kind of size. Don't book long rooms if you can avoid them.

Continuous power is the maximum power at which the speaker/amp can reproduce pink noise continuously. I gather program power is just an arbitrary judgement, since it's always twice the continuous. The idea is that program material will never be continuous and contains so much dynamic that the power will average out at only half as much as continuous over time. Or some such. Peak is supposedly twice that again, and is representative of the maximum transient response of the speaker.

I'd be more or at least as much concerned with sensitivity when comparing speakers.