Best budget amp(s) for pair of secondhand 18" subs?

[Tim Woodle]

Hi!

First post alert... Apologies for cutting to the chase!

I've bought a pair of secondhand Martin Audio S18+ subs:

https://martin-audio.com/downloads/datasheets/s18+datasheet.pdf

TYPE Compact, vented sub-bass system
FREQUENCY RESPONSE (1) 40Hz-120Hz ± 3dB
-10dB @ 35Hz
DRIVERS 18” (460mm)/4” (100mm) voice coil LF driver
RATED POWER (2) 750W AES, 3000W peak
RECOMMENDED AMPLIFIER MA9.6K
SENSITIVITY (3) 102dB (half space)
MAXIMUM SPL (9) 130.5dB continuous, 136.5dB peak (half space)
NOMINAL IMPEDANCE 8 ohms

The rest of my system (HK Audio / db Technologies) is powered so this is my first venture into the world of independent amplification!

I understand the basic principles of ohms, watts and the like, and have been trying to research amps at the budget end of the scale that will do the job.

I know Behringer is still a relatively dirty word in the pro-PA world but here are the options / approximate prices that I've found so far. Bear in mind that the choices / availability are limited as I'm based in Dubai.

Behringer NU3000 (Assume 2 required) @ 1000AED ($270) each
https://www.music-group.com/Categories/Behringer/Power-Amplifiers/Portable-Amplifiers/NU3000/p/P0B1P

Behringer EP4000 (Maybe 2 required?) @ 1500AED ($408) each
https://www.music-group.com/Categories/Behringer/Power-Amplifiers/Portable-Amplifiers/EP4000/p/P0A37

QSC GXD 8 @ 3000AED ($815)
https://www.qsc.com/live-sound/products/power-amplifiers/gxd-series/gxd8/

Behringer NU12000DSP @ 3200AED ($870)
https://www.bhphotovideo.com/c/prod...u12000dsp_ultra_lightweight_high_density.html

My aim is to get the best suited amp(s) for the money. If I understand the basic phsyics well enough then I need a genuine 1500W per channel at 8 ohms, be that bridged or otherwise. Am I correct in saying that a single 3000W bridged amp at 4ohms would also suffice if the speakers were wired in parallel? I'm also concerned that the NU12000DSP will require a high amp electrical circuit which my regular venue will not be able to supply. Is two NU3000 in bridged mono an option? That would give 1250W at 8 ohms on both sides.

All advice much appreciated!

Cheers,

Tim

 

[Brian jojade]

The type of music that you are planning to play will determine which configuration is safe to use. If you are playing highly dynamic music, running at the peak rating will give you the most headroom. However, if you run heavily compressed music, using an amplifier that is much over the RMS rating of the speaker will cause them to burn up.

The rules are that you don't want to exceed the peak rating, ever. (3000 watts in this case) Also, your overall average power should not exceed the RMS rating of the amp, or the speaker will burn over time. (750 watts)

So, for normal music playback, it's generally accepted that 2XRMS is a good rating for someone that is smart enough not to run the amp balls open all night. With 2XRMS you can run the amp until you see clip lights flicker and be pretty safe. (again, not with sustained EDM, but normal music)

The spec sheet says that they recommend the MA9.6K amplifier. They don't say how the recommend connecting it to the speakers. If they expect you to use it in dual channel mode, that would mean the amplifier is rated at 1500 watts per speaker at 8 ohms. If you run it bridged, that would be 6000 watts at 4 ohms, which would be 3000 watts per speaker. Either configuration in the hands of the wrong operator can blow up the speakers.

Running less power is never a problem, as long as you are not clipping the amplifiers. The difference in output between 1250 watts and 1500 watts is barely noticeable.

The other thing to consider is how 'real' the power ratings of the amps are. Especially on subs, all amps are not created equal. Even though they may have high ratings numbers, the true output that they can provide may not be sustained enough at low frequencies to do the job. The QSC GXD is a fine little amp, but on subs, with a long extension cord, not going to be your friend. The Behringers get mixed reviews, but are in the same class as the QSC GXD.