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Author Topic: Get More Power Out of an Amp  (Read 1865 times)

Tim McCulloch

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Re: Get More Power Out of an Amp
« Reply #10 on: December 26, 2018, 06:15:42 pm »

Victor,

    Watts are not really important. Also, you cannot power a speaker at its rated peak wattage. Going back to what I said in another post, even if you double the power, you will only see a 3db increase in output. 3db is a pretty small and relatively useless gain in the grand scheme of things. For example:

If your speakers were 2,400 watts peak @ 8 ohms. you would actually only be able to realistically power them with an amp capable of about 1,200 - 1,500 watts. You probably won't find an amp that you will afford that can actually produce 2,400 watts at 8 ohms. anyway.

If you parallel the speakers, their total peak wattage doubles and you would then have a 4 ohm. load. You would need an amp capable of about 2,400 - 3,000 watts at 4 ohms. to properly power them. Let's break this down more.

There are three wattage ratings for a speaker, an ohms. rating and a speaker sensitivity rating. The three wattage specs are its peak, program and continuous rating and tells you in a nutshell how powerful of an amp to buy. The other specs basically line out what the speaker can do and make it possible to calculate the potential performance. Let's see what your speaker likely has going on for it ( this is a hypothetical because we don't know what your speaker is ).

1. Your speaker has a peak rating of 2,400 watts @ 8 ohms.

2. Your speaker has a program rating of 1,200 watts @ 8 ohms.

3. Your speaker has an RMS/Continuous rating of 600 watts @ 8 ohms.

4. Your speaker has a likely sensitivity of 98db @ 1 watt - 1 meter. This is the sensitivity of the speaker.

All this info is simple to break down. You cannot exceed 2,400 watts of power, your ideal wattage to power the speaker with is 1,200 watts and for long-term safe usage, you should not exceed 600 watts of power. That's is all the wattage numbers mean. Now for output, the math is a little more complex but easy enough. If the speaker gives you a peak SPL number it is generally easier to come up with a theoretical SPL number. Since we don't know we can use simply use the sensitivity to come up with that. 1 watt will = 98db ( in theory ). If doubling power gives us a 3db boost then 2 watts would = 101db. We have to continue doubling the power to see that 3db boost, so 4 watts would = 104db, 8 watts = 107db, 16 watts = 110db, 32 watts = 113db, 64 watts = 116 and so on. You can see how you quickly get to a point of diminishing returns. The next doubling of power is 128 watts, then 256, then 512 and 1,024 etc. etc. By the time we get to 1,024 watts, we have only doubled the wattage 10 times for a total of 30db in gain. So 98db + 30db = 128db. So what about a 2,400-watt amplifier? Well, the answer is 131.8db, or a gain of 3.8db!!!!! So that last 1,376 watts is worth less than 4db of output!

So we can now see the point of diminishing returns comes quick. You can't power that speaker with an amp that actually provides 2,400 watts of power, you are looking for one that will provide roughly 1,200 watts which will provide you with an output of roughly 128.8db. 3db less than your theoretical peak. Which then means powering the speaker with an amp that only provides 600 watts will again only be 3db lower for 125.8db in output.

It doesn't matter if you place both speakers in parallel either. You have doubled the wattage potential of the speakers and the amp, so it washes out completely and you still end up with the same output potential. You can't cheat the math on it and even if you grossly overpower the speakers you won't really gain anything. If you actually tried to power a single speaker with the full 2,400 watts, it would burn up and die in just a few moments.

You may have heard the term ' There is no replacement for displacement " as it relates to cars engines? It is exactly the same with subs. For more output, you need a speaker that can move more air, or more subs to move more air ( displacement of air ). And like a big engine needs gas to power it, wattage is needed to power a speaker. A big powerful speaker needs lots of wattage to get it to its peak performance. A smaller less powerful speaker utilizes less wattage and hence has less performance.

Responding to the text in bold...

Victor, TANSTAAFL.  Luke explains it better but read fully and carefully what he wrote.

Luke, I 100% agree about the power amp.  While there are some 2400 WPC amps out there that will produce that current for longer than a few ms, none of them are likely to meet Victor's budget.

On adding speakers in parallel - you should be able to measure a +3dB change from the doubling of the piston area with the same input voltage.  Current becomes a factor when potential (voltage) is converted to work/heat, so it's "how long can this current be supplied at X voltage."  Adding an identical power amp to the additional piston (loudspeaker) can yield a theoretical +6dB increase.

"There is no replacement for displacement" is attributed to Carroll Shelby.
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Chris Grimshaw

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Re: Get More Power Out of an Amp
« Reply #11 on: December 27, 2018, 08:09:26 am »


You have noted that the speakers have a 4800 watt at 8 ohm peak rating and a 2400 watt at 8 ohm RMS rating.  This would tend to indicate that the continuous capability of these speakers is approximately 1200 watts at 8 ohms (approximately the rating of the amplifier that you have).

I'd take it to mean the cabinet is rated for 2400w continuous, and I'd aim for an amp that'll manage somewhere around 4-5KW into 8ohm. Hint - that'd probably be something bridged, since even a K20 only manages 2700w/ch into 8ohm.

Victor, what are the cabinets you're using?
There aren't many individual drivers rated for >2KW continuous, so I'm wondering if it's a 2x18". In that case, you might find it's 2x 4ohm drivers in series, and a bit of re-wiring would mean you can feed each driver with an amp channel, with a lot of power.
With the amps you have, and single 8ohm cabinets, I'd put one cabinet on each channel, give the amps an easy time, and let them clip, so long as they're not clipping continously.

Chris
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Paul G. OBrien

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Re: Get More Power Out of an Amp
« Reply #12 on: December 27, 2018, 05:04:22 pm »

Victor, what are the cabinets you're using?
There aren't many individual drivers rated for >2KW continuous, so I'm wondering if it's a 2x18". 
Or is it a single driver DVC sub? In that case too "bi-amping".. one VC per amp channel..  is a good way to get more power into the sub and better utilize the amp.
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Victor Estrada

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Re: Get More Power Out of an Amp
« Reply #13 on: December 31, 2018, 04:36:52 pm »

I'd take it to mean the cabinet is rated for 2400w continuous, and I'd aim for an amp that'll manage somewhere around 4-5KW into 8ohm. Hint - that'd probably be something bridged, since even a K20 only manages 2700w/ch into 8ohm.

Victor, what are the cabinets you're using?
There aren't many individual drivers rated for >2KW continuous, so I'm wondering if it's a 2x18". In that case, you might find it's 2x 4ohm drivers in series, and a bit of re-wiring would mean you can feed each driver with an amp channel, with a lot of power.
With the amps you have, and single 8ohm cabinets, I'd put one cabinet on each channel, give the amps an easy time, and let them clip, so long as they're not clipping continously.

Chris

It's gonna be for a pair of Peavey Low Max speakers which are rated at 1200/2400/4800 watts each, for a total of 2400/4800/9600 watts. The amp is a Peavey IPR2 7500 that will push out 2400w at 4ohms, so that's why the question as this amp is not bridgeable. But if it doesn't really provided any extra dBs then it doesn't really matter right? I'm not concerned about pricing, just want the most power in the smallest package as my goal is to fit everything in my SUV lol
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Scott Holtzman

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Re: Get More Power Out of an Amp
« Reply #14 on: December 31, 2018, 06:48:38 pm »

It's gonna be for a pair of Peavey Low Max speakers which are rated at 1200/2400/4800 watts each, for a total of 2400/4800/9600 watts. The amp is a Peavey IPR2 7500 that will push out 2400w at 4ohms, so that's why the question as this amp is not bridgeable. But if it doesn't really provided any extra dBs then it doesn't really matter right? I'm not concerned about pricing, just want the most power in the smallest package as my goal is to fit everything in my SUV lol

I have six of those, they can't sustain the power for long and they are woefully inadequate at driving STX-828S which have similar power handling as your drivers.
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Victor Estrada

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Re: Get More Power Out of an Amp
« Reply #15 on: April 03, 2019, 11:24:59 am »

I have six of those, they can't sustain the power for long and they are woefully inadequate at driving STX-828S which have similar power handling as your drivers.

6X Peavey IPR7500s? How do you power them all? Wouldn't that be the issue?
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John Roberts {JR}

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Re: Get More Power Out of an Amp
« Reply #16 on: April 03, 2019, 11:43:08 am »



"There is no replacement for displacement" is attributed to Carroll Shelby.
The modest displacement 4 cylinder Offy engines made as much as 1000 HP with turbocharging.

Not a good analogy but modern class D amp technology delivers more power to speakers, and less to room heat.

JR

PS: I am still driving my 20+ YO mustang Cobra, but not remotely a real Shelby Cobra, not even a Shelby mustang...  RIP Carroll Shelby 
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Scott Holtzman

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Re: Get More Power Out of an Amp
« Reply #17 on: April 04, 2019, 12:49:38 am »

6X Peavey IPR7500s? How do you power them all? Wouldn't that be the issue?
Hi Victor,.  They have 30amp chassis mount IEC's.  When I got them I didn't read the specs that they are 120V only and set one on fire.

Anyway.  I have a distro panel in the bottom of the rack and each amp has a 30amp breaker.

I feed the rack with 50 amps 240v.  I added 2 amps over winter for the 5th and sixth sub.  I am going to put them in a separate rack for when I want to run two subs by themselves.  I will feed that with a 30 amp 240v.  That is my standard stage stringer cable and I have a bunch of those in main distro so it scales nicely into my master plan. 

If I run just the two and don't have anything other than 120v then one amp to a 15 or 20 amp circuit and dial the processing back as needed to keep from popping the breaker.

The take away is if I am running six dual 18 cabinets the venue will have proper power or we will order a genie.  I used four at a high school auditorium and we had a 25kva genie for that event. 

Sent from my VS996 using Tapatalk

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Re: Get More Power Out of an Amp
« Reply #17 on: April 04, 2019, 12:49:38 am »


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