Recommended amp for one 12" sub?

Factual Questions
1

My box fills the needed airspace, and I need an amp to power the single 12" sub only (mono, right?). Help me select a decent but inexpensive amp!

Size (IN.,CM) 12

Impedance (OHMS) 4

Max Rec Amplifier Power (WATTS PEAK/RMS) * 300/150

Sensitivity (dB 1w/1m) 88.3

Frequency Response (Hz) 27-500

Mounting Depth (IN.,CM) 5-7/8

Mounting Cutout (IN.,CM) 11, 27.9

Min Rec Sealed Box Volume (CU. FT., Liters) 1.25, 35.4

Max Rec Sealed Box Volume (CU. FT., Liters) 3.5, 99.1

Min Rec Vented Box Volume (CU. Ft., Liters) ** 1.75, 49.6

Max Rec Vented Box Volume (CU. Ft., Liters) ** 2.25, 63.7

2

There is a calculation that allows you to work out the maximum power a bass driver can safely use. This is based upon the maximum cone excursion it can manage before being damaged. However to work this out you need the Theile Small driver parameters, and the box design. These numbers are: maximum excursion, Vas (equivalent volume or air that equals the cone and suspension) Qts (total Q of the speaker, both mechanical and electrical), Fs (resonant frequency in free air) and speaker impedance. For the box, the volume of the box, and if vented, the port dimensions, or the total system Q and system resonant frequency. Then the maximum power handling can be found.

These should all be available from the driver manufacturer. There are quite a few on-line calculators or spread sheets that can tell you the answer. But without knowing these, it is impossible to know. The usual maximum number quoted for a driver are mostly useless, and typically are thermal ratings. These will usually be much larger than the maximum power needed to cause mechanical damage.

3

Seeing the acoustic range covered by the sub I would say the key factor in choosing an amplifier would be the capability to deliver clean, undistorted power. (Even cheap pro/semipro gear sounds fairly decent nowadays and probably good enough for this kind of task). A loudspeaker can suffer damage not only from too much power, but also from clipping (from an amp with insufficient power being driven beyond its capabilities). I would chose a solution with ample power reserves (to avoid clipping) but limited (perhaps by a gain selector) to match the loudspeaker’s specs.
First I thought about recommending an amp such as this (or any other like it in the “power amps” section). But then I realized that for a sub you’d probably want to bridge it. To bridge an amp into 4 ohms would require it to be able to drive the equivalent of 2 ohms/channel. Not many amps can do that. There are plenty that can, but one cannot buy one at random assuming it will.
I would go into any decent pro audio store and ask for advice. The salesmen there are usually knowledgeable and they’ll probably find something for you.
Good luck.

4

Man, is it really that hard to figure out the correct amp? I thought it would be simple!

5

I’m really over complicating things, but there is a core issue in the difference between thermal power capability and excursion limited capability when it comes to bass drivers.

Anyway, what I do see is that you have Kicker Comp 12. Telling us that would have been a good start. For interest, the manual does include the Theile Small parameters.

Nominal Impedance [Zn], 4 or 8

Resonance Frequency [fs], Hz 30

Power Handling Watts, Peak (RMS) 300 (150)
Sensitivity [SPLo], dB @ 1W, 1m 88.3
Total Q-Factor [Qts] .559
Effective Excursion [EXmaxTM] in (mm) .38 (9.6)

DC Resistance [Re], ohm 3.65

Equivalent Volume [Vas], ft3 (L) 3.36 (95.18)
Net Displacement, in3 (cc) 70.6 (1156.9)

The excursion limit depends upon the lowest frequency you will play, and so is a bit complex to work out, depending upon use.

The Kicker drivers are mostly directed at car use, and this makes a huge difference due to cabin gain. However some people do use them for home theatre, and even here room gain makes things in the bass a bit strange. In a car the cabin gain is massive.

However the speaker manual does do the basic sums, and recommends a maximum power of 150 watts for most enclosures, and you may as well run with that.

But you still have not really said a great deal about the intended use. Is it for a car? Home theatre? Music? Party speakers? Which box design? Makes quite a bit of difference. If you are building a basic sub for home use one of the many subwoofer plate amplifiers is probably the best bet. They are cheap, and exactly designed for purpose. Which you buy can depend upon where you are, and what you are prepared to spend. For a car, there are so many choices it is silly.

6

I do apologize, it is in a vented box with the min airspace required. Installed in my truck, down firing, and in an extended cab.

7

OK, since it is going in your truck the constraints are more clear. However we now get to the next set of questions. So, you want to add a subwoofer. What are you adding it to in terms of existing sound system? Is it just the stock system the truck came with? Do you already have a custom installation? What is the head unit? Does it have appropriate outputs to drive a subwoofer?

If you are just messing with the stock system you probably want to consider a system upgrade as a whole. Just adding lot (and a speaker like you are proposing installed in the cabin will produce enough bass to rattle your teeth - so we do mean a LOT) of bass, to what is likely a very mediocre existing system, won’t sound particularly great. Some of the result will depend upon your musical tastes and your likely listening needs. It isn’t hard to put together a very good sounding system for not a lot of money nowadays. Reasonable quality cheap speakers, class D amplifiers, and an iPod. All made in China, which is why so cheap. At the extreme end people go nuts, putting together systems that are not actually intended to be listened to. And there are systems whose only intent is to create a bass monster, whereas most people probably prefer a system that actually sounds good playing music.

If you are going a DIY route, there is a lot you can do to make for a much better overall result by investing some time and money in doing a really careful installation. You could do worse than have a look a some of the specialist forums. For instance this one doesn’t look too stupid.

8

It actually is pretty simple. A 2-channel bridgeable amp with decent power and a crossover is all you need and will work fine.
If you’re looking for the perfectly matched amp for that particular sub, in that particular enclosure, in that particular vehicle then you can knock yourself out with all the calculations you want.

9

Sorry. I just opened this up to see why anyone needs an amp for a foot-long sub. I’m going to step out for lunch now.

10

I appreciate your informed responses!
I have a system already with two identical 12" subs (downfiring sealed underseat box) with an aftermarket head unit and an audiobahn 1120 watt 4 channel amp.
I want to downgrade, so I bought a new box with the intentions of using only one sub. The 1120 amp will overpower the sub, and I want a smaller amp anyhow (size wise).