Matching Amps & speakers
luiss
Posts: 35
Ok, so at this point in my life these questions shouldn't need asking......
but...
It has been a good decade since I underwent my audio training and that was 99.99% studio focused. Since then all my audio related jobs were as an operator only, with most of that in the studio performing odd things like governmental archiving. My live experience has been mostly as a monitor operator with only 1-3 gigs a week with a rig that was already configured. So......
Its time I brushed up on the fundamentals.
So.....
Here is a list of questions.
1. The system I'm currently helping to setup uses 2 x mackie 408 and 2 x 410s. We have been using an Alto amp for the subs and a Tony Lee for the tops. (I'm waiting for the specs to be emailed to me) We are running this through a Peavy crossover (soon to be a DR260).
Is it prefferable to run the sub amp as bridged? Do you actually get more power? (I feel an idiot asking this..) If this is so what is the calculation to measure the impedence of the subs.
2. Can any one reffer me to a good online learning reasorce on speaker/amp matching that starts at the very most basic and contiues through to the advanced principals?
ta!
but...
It has been a good decade since I underwent my audio training and that was 99.99% studio focused. Since then all my audio related jobs were as an operator only, with most of that in the studio performing odd things like governmental archiving. My live experience has been mostly as a monitor operator with only 1-3 gigs a week with a rig that was already configured. So......
Its time I brushed up on the fundamentals.
So.....
Here is a list of questions.
1. The system I'm currently helping to setup uses 2 x mackie 408 and 2 x 410s. We have been using an Alto amp for the subs and a Tony Lee for the tops. (I'm waiting for the specs to be emailed to me) We are running this through a Peavy crossover (soon to be a DR260).
Is it prefferable to run the sub amp as bridged? Do you actually get more power? (I feel an idiot asking this..) If this is so what is the calculation to measure the impedence of the subs.
2. Can any one reffer me to a good online learning reasorce on speaker/amp matching that starts at the very most basic and contiues through to the advanced principals?
ta!
0
Comments
The speakers are usually already rated as to their "nominal" impedance... that is kind of like an average~ The 410's for instance have a nominal impedance of 8 ohms, but @ 110 hz (usually the highest efficiency point) they are rated @ 3.8 ohms...They are rated at 750 /3000 watts...
What that means is that the speakers will handle 750 continuous watts of pink noise (12dB crest factor) 24hours a day 7 days a week...there are actually 2 other pertinent numbers here...
Program: twice the continuous rating or 1500 watts
Peak: Instantaneous peaks usually milliseconds in length only, of 300 watts...
SO what amp is best" well, in subs especially it's best to have at least the program rating, but on subs, the more power the cleaner the sound will be... make no mistake however, if you feed that 3000 watts to the speakers in program fashion (in other words use the whole 3000 watts a lot of the time) you will most definitely have a fantastic display of fireworks and you will let the smoke out of the speakers...
As for the requested info, you have come to the right place!
Here:
viewtopic.php?f=61&t=959
is a getting started with the Driverack and gain structure...
Here is an FAQ section I put together that should keep you going (between that and the links provided in the "start here" thread) for some time!
Get yourself the GUI here:
http://www.dbxpro.com/Software.php
and start working with the different modules... like read the FAQ on "What are PEQ's anyway?"
and then open the GUI and play with the PEQ section and see visually what you are doing ...
Were always here.. in one form or another...
G
So if I used a bridged amp for the subs and connected 4 x S410s I would then be running the amp at 2 ohms?
For arguments sake lets say I'm using a QSC PLX2502 that is rated at... hang on... looks like you can't run an amp down to 2 ohms when bridged....
Ok then so lets say I'm running 2 x S410s (what we currently have) as stereo. So each box is 8 ohms, allowing 775 watts from a QSC PLX3602. Would this amp then be considered well matched? The amps output creeps in just above the rms rating of the box (750 watts).
The QSC specs don't indicate RMS or peak for the power rating so I am assuming RMS.
So with the same gear I bridge the amp and show it 4 ohms from the linked subs. The amp now provides 3600 watts. I assume this dramtic increase in power output is the combination of the combined output of the amplifier channels and the decreased impedence of the boxes. With an RMS rating of 750 watts The S410s are now in danger of being overpowered? The peak handling of the boxes is 3000 watts so the amp even exceeds that.
Interestingly the QSC amp calculator came up with this (see attached) calculated as 2 subs per side.. getting ahead of myself.
They suggest running 1 bridged amp each side. Why?
Back to some calculations....
Based on what we have running now I wonder if we should bridge the Alto Mac 2.4 for the subs. We are currently running it in stereo and recieving 560 watts a channel into 8 ohms. Bridging will provide us with 3100 Watts into 4ohms. So here I am back at power levels exceeding the specs of the box...
Last question (for now)
What does EIAJ mean in relation to power specifications?
Yes.. but
Bridged amps are only safe down to 4 ohms...some amps are ok @ 2 ohms stereo...but NEVER bridge an amp and run it below 4 ohms!
Remember that when you run 4 cabs on one amp in stereo, and those 4 speakers have 4 drivers in them you need to divide the available power by 8...so 2 channels lets say the amp has 1500 watts per channel at 2 ohms stereo... 1500 /8 = 187.5 watts per driver...
@ 1500 watts program you want each speaker to get at least double that... 375 watts, and to have headroom... more than that up to 750 watts per driver.. potential.
For live music it's nice to have the headroom, for DJ work the 1500 watts is sufficient.
G
I haven't proof read it so I've probably got a few things wrong...
I'm manning my wife's stall at a childbirth expo and need some distraction...
I'm at the casino doing sound for "Doug Allen and the Chicago Mob"... 8)
When you put 2 speakers on the amp that have 8 ohms for each cabinet and you parallel them you get 4 ohms "nominal" load impedance....the amp, when bridged, takes the output of channel 1, reverses the polarity and feeds that into channel 2.
**Note**, this also increases the current draw of the amp DRAMATICALLY...
So, you have an amp that in 4 ohm bridged produces 3100 watts, and speakers that are rated:
750 RMS
1500 program
and
3000 watts (instantaneous) peak...
I already answered the question but we'll try this another way...
you now have 8-10" drivers...those each want
750 watts /4= 187.5 to meet the the "RMS" value which is the minimum you want, and that will NOT make very impressive noise...
Double that, and you get 375 watts (*per driver) X 8= 3000 watts (3100 watts adds an additional WHOPPING 12.5 watts /driver
First of all, to get twice as loud as 1000 watts you need 10X the power... that's 10,000 watts....
So, @ 3100 watts you will be feeding the speakers the rated power and will have NO headroom what, so, ever...
Live music is VERY dynamic, as opposed to canned (CD/MP3) music which is heavily compressed...
Heavily compressed music would best be served by the 3100 watts...BUT NO CLIPPING!!!
Live music would require more power to produce the same volume level... and still have headroom.. you need MORE POWER....
What they are telling you is that an amp bridged, that produces 3000 watts, would provide ample power AND some headroom...
That is a "standard" which no one really seems to pay a lick of attention to :roll:
Gadget