How do you match an amp to a speaker?

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XAXAU
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Joined: Fri Jan 29, 2016 2:27 pm
Location: Sweden

How do you match an amp to a speaker?

#1 Post by XAXAU »

I´m thinking of building 2x T30´s with Eminence 3012LF´s in them and I´m wondering what kind of amp to match that power with.

Do you have more wattage in the speakers or in in the amps or equal in both.

For example the 3012LF´s can take 450WRMS, how much amp do you use for that? Let´s say you´d want to drive them flat out!

The amps I´m looking at (LAB GRUPPEN) list their power in Watts, I assume that´s their peak wattage before going into clipping.


Thanks!

Ryan A
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Location: Minneapolis, Minnesota

Re: How do you match an amp to a speaker?

#2 Post by Ryan A »

Find one that'll do a little more then your speaker's power rating.

When it comes time to set it up, you will limit with voltage, and you'll want the voltage limiter to kick in before you amp goes into clipping.

An amplifier something like 500 or more watts per channel RMS at 8 Ohms should do the trick.

commander_dan
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Location: Perth, Western Australia

Re: How do you match an amp to a speaker?

#3 Post by commander_dan »

A useful tool you can use is this:

http://www.rapidtables.com/calc/electri ... ulator.htm

Using that you can determine what an amp is putting out in terms of voltage at a given resistance. It's also good to see what various amps will do at 8, 4 and 2 ohm loads. You want an amp that will put out between 10 and 20 volts more than what your voltage limit will be set at, to give the amp some headroom so that it's not running at maximum when your system is. Amps running at or close to maximum will have a shortened life.

In your case, your limiter will be set to 50V, so you're looking for an amp that will put out between 60-75ish volts at 8 ohms. Also make sure to check what the amp does at 4 and 2 ohms in case you plan to expand your system in the future.. it's a case of diminishing returns as the impedance load drops.

Crown, Crest, Peavey, QSC are all top notch products.
Built:
6 T30 (24", 3012LF)
2 OT12 (MA, 3012HO)
2 T24 (18", 3010LF)

Running:
DCX2496
XTi 2002
XTi 4002
TRAKTOR Z2
TECHNICS 1210 Mk5's

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BrentEvans
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Re: How do you match an amp to a speaker?

#4 Post by BrentEvans »

commander_dan wrote: Crown, Crest, Peavey, QSC are all top notch products.
Definitely good enough for most of our uses, not top notch. The Lab Gruppens previously mentioned are one of a few that occupy that "top notch" slot.

That said... LGs are for concert tours. They're crazy good. There are reasons they are as expensive as they are. The LG E12 is probably the closest one, but there's no reason you can't use an Crown Xli2500, Crest Prolite 3.0, Peavey IPR2-5000 or QSC GX7. They're all quite competent products at this level of speaker systems, and priced far less than the LG.
99% of the time, things that aren't already being done aren't being done because they don't work. The other 1% is split evenly between fools and geniuses.

XAXAU
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Joined: Fri Jan 29, 2016 2:27 pm
Location: Sweden

Re: How do you match an amp to a speaker?

#5 Post by XAXAU »

Thanks guys!

I´m having a hard time finding any RMS numbers for the Lab Gruppen amps.

15 years ago I heard 2x 15 horns being driven by an old Lab 1000 amp and it was seriously loud. The same amp has figures like this in the manual:

8ohms
FTC 20 Hz-20 kHz @ 0.1% THD: 350W
EIA 1 kHz @ Clip (1% THD): 380W
IHF Peak Power 20 ms burst: 450W
Calculated Peak Power: 500W

Does it mean that it can do peaks @ 350W or is that RMS?

Spec sheet here: http://www.manualslib.com/manual/290508 ... e=2#manual

Grant Bunter
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Re: How do you match an amp to a speaker?

#6 Post by Grant Bunter »

XAXAU wrote:Thanks guys!

I´m having a hard time finding any RMS numbers for the Lab Gruppen amps.

15 years ago I heard 2x 15 horns being driven by an old Lab 1000 amp and it was seriously loud. The same amp has figures like this in the manual:

8ohms
FTC 20 Hz-20 kHz @ 0.1% THD: 350W
EIA 1 kHz @ Clip (1% THD): 380W
IHF Peak Power 20 ms burst: 450W
Calculated Peak Power: 500W

Does it mean that it can do peaks @ 350W or is that RMS?

Spec sheet here: http://www.manualslib.com/manual/290508 ... e=2#manual
I made the peak power bold.
I would treat that as 350W average power.
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" KL3010LF , 2 x 28" 3012LF.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

XAXAU
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Location: Sweden

Re: How do you match an amp to a speaker?

#7 Post by XAXAU »

After some research I found out that the Lab 1000 amp above puts out about 52Vrms. If the 3012LF´s are limited at 50V then I should be able to drive them "all the way" without breaking stuff (on paper), right?

commander_dan
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Re: How do you match an amp to a speaker?

#8 Post by commander_dan »

XAXAU wrote:After some research I found out that the Lab 1000 amp above puts out about 52Vrms. If the 3012LF´s are limited at 50V then I should be able to drive them "all the way" without breaking stuff (on paper), right?
Yes, but with only 2V of headroom, that amp will be running right on it's max output. I would go for something beefier if it was me. Are you intending to ever expand to 4 Tubas?
Built:
6 T30 (24", 3012LF)
2 OT12 (MA, 3012HO)
2 T24 (18", 3010LF)

Running:
DCX2496
XTi 2002
XTi 4002
TRAKTOR Z2
TECHNICS 1210 Mk5's

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Bill Fitzmaurice
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Re: How do you match an amp to a speaker?

#9 Post by Bill Fitzmaurice »

XAXAU wrote: The amps I´m looking at (LAB GRUPPEN)
Unless you have a source to get them at cost or just won the lottery look elsewhere.
there's no reason you can't use an Crown Xli2500, Crest Prolite 3.0, Peavey IPR2-5000 or QSC GX7.
+1.

XAXAU
Posts: 14
Joined: Fri Jan 29, 2016 2:27 pm
Location: Sweden

Re: How do you match an amp to a speaker?

#10 Post by XAXAU »

I´m looking at old, proven, solid, and perhaps rundown (visually) Lab Gruppen amps. The new ones are out of my league. However, in Sweden where the old Lab amps where made there are gems to be found. Mint Lab 1000´s may be found for as little as 300USD. And while they are heavy, noisey they are reliable and have very fast slew rates.

Anyway, my initial question was: how to match an amp to a speaker.

So if the amp can do 52Vrms and the 3012LF can do 56Vrms, you guys are saying that´s not enough?

My feeling is that is that I´d probably prefer to have way too much power but not break a sweat. But what power? Speaker or amp?

Remember, I´m just asking here! I´m a noob!n Thanks for your input!!

commander_dan
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Joined: Sun Feb 16, 2014 7:19 pm
Location: Perth, Western Australia

Re: How do you match an amp to a speaker?

#11 Post by commander_dan »

In a T30, the 3012LF can safely take 50 volts, so you should ignore what it is rated for out of the box; effectively for you, that's the figure. It doesn't "do" any volts, as volts are fed to it. We talk in volts around here because they can be easily measured (with your standard AC multi-meter), whereas watts are much harder to measure; in a pinch, they can only be calculated.

As previously mentioned, it is not best practice to have your amp running at max output, so when you match your amp to your cab, you should ensure you have enough headroom so that your amp doesn't run on the bleeding edge of its capacity, but not so much that your brick-wall limiter can't bring the voltage down to the set limit.

I'm not saying that an amp that can only put out 52 volts can't take the T30 to full noise, it can. But how long it would last being asked to do that for hours on end is anyone's guess.

Hope that helps answer your question :)
Built:
6 T30 (24", 3012LF)
2 OT12 (MA, 3012HO)
2 T24 (18", 3010LF)

Running:
DCX2496
XTi 2002
XTi 4002
TRAKTOR Z2
TECHNICS 1210 Mk5's

XAXAU
Posts: 14
Joined: Fri Jan 29, 2016 2:27 pm
Location: Sweden

Re: How do you match an amp to a speaker?

#12 Post by XAXAU »

I agree on using Volts, Watts are confusing to me. How have you guys arrived at the max V for specific drivers?

Using an amp at its limits should also sound bad right? Maybe it´s best to have way more power than is needed? That approach should be the same for drivers too right?

Bruce Weldy
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Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: How do you match an amp to a speaker?

#13 Post by Bruce Weldy »

XAXAU wrote:I agree on using Volts, Watts are confusing to me. How have you guys arrived at the max V for specific drivers?

Using an amp at its limits should also sound bad right? Maybe it´s best to have way more power than is needed? That approach should be the same for drivers too right?
Bill determines the amount of voltage that a driver can handle in any particular enclosure. This varies based on the size of the chamber, how low the box goes, and pressures that are created to make that happen. That's for the subs. Tops are a different matter as you can hear them distort and know to turn 'em down.

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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