Can someone answer this one for me?

I have 2 subs (Infiinity Perfect 12.1) both 4 ohm running in parallel so the amp sees 2 ohm.

The amp (Kicker IX405D) has a sub section which outputs 390W (Dynamic Power at 14.4v / 290W (RMS at 12.2v), I have a power cap which is normally having the voltage run at about 14v

The subs are rated at 350w RMS / 1400w Peak.

Are they getting 390w (ish) from the amp EACH or BETWEEN them (i.e. 195w each).

Am I way underpowering my subs ? Should I be buying a bigger amp ? If so, what would you guys recommend at under 350 UKP.

Any advise very welcome.

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Are they getting 390w (ish) from the amp EACH or BETWEEN them (i.e. 195w each).

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Well, they are sharing the full output power of the amp between them, each getting half of it. But was the full power of the amp specified at 4 or 2 ohm load? You *probably* get more power out of it into a 2 ohm load than into a 4 ohm load - at a greater risk of blowing the amp or getting clipping/distortion.

Car amps are usually voltage-bound, with a fair bit of current reserve, so they do give out more power into a 2-ohm load - *iff* they can take it! Is your amp specified to work on 2 ohms? 2 ohms is awfully low...

I don't think you are underpowering your speaker. But how loud do you play? How much reserve do you seem to have? (How much louder *can* you play compared to how loud you normally play)

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Is your amp specified to work on 2 ohms? 2 ohms is awfully low...

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Yep, the sub channel is rated at 2 ohms 390W and is stable at 2 ohms. I'm very pleased with the IX405D. I think one of the empeg guys had the same one in a beetle ?

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But how loud do you play? How much reserve do you seem to have? (How much louder *can* you play compared to how loud you normally play)

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When SWMBO is in the car, not very loud, but when i am on my own, i like it loud sometimes.

It's more a question of quality, i listen to lot of dance music, drum and bass etc, and sometimes the notes are very low. I don't know whether the amp is running out of power or it's just too low for the subs, or maybe the MP3 doesn't have the dynamic range ? It seems that sometimes the bass notes don't get any louder, just the mid and treble, so I think it is running out of steam.

The sub section volume is all the way up, with the bass boost up about 1/3 of what is available.

Also, i am moving to a bigger car (either a RAV4 or a CRV) and I want to maintain the sound levels. Will they drop significantly in a bigger car ?

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The sub section volume is all the way up, with the bass boost up about 1/3 of what is available.

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Hmm. OK, I would start here - can you turn up the gain on the empeg, and turn down the gain on everything *except* the sub?
I suspect you are not hitting the power limit of the amp yet.

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Also, i am moving to a bigger car (either a RAV4 or a CRV) and I want to maintain the sound levels. Will they drop significantly in a bigger car?

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A car is pretty much an enclosed box, so sound levels won't be affected that much.
Convertibles/roadsters are another matter... And so are land rovers (think "sieve" rather than "box":))

I can't call it a scientific fact, but my experience is that - yes, car size does make a difference. At the stereo contests and such a small car such as an old Honda CRX can hit much higher SPL numbers than say a Suburban, and do it with less speaker area and less power. I've seen it a million times, and it is widely accepted as a fact though I can't give up any formulas to show it. All that goes out the window (literally) with the windows down though since the car is no longer an enclosure.

I'm stumped on the other half of the question - it's a good one for sure (how to tell if the amp is running out of steam). I'm trying to think of ways to measure it - dimming headlights, or maybe with some kind of datalogger to see if it's not getting the juice it needs. The cap you have should take care of that though (old school rule of thumb was 1F per 1,000W).

Gut feel says that the amp is plenty, but you know how that goes.

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can't call it a scientific fact, but my experience is that - yes, car size does make a difference.

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OK, I was making some gross simplifications. At *some frequencies* the size of the car makes a lot of difference, as the bodywork actually flexes and thansmits energy out of the car. The bigger the car, the bigger the surface area - and large areas of panel and glass let out more energy.

So an armoured car (or better yet, a tank) would be ideal from sound purposes. But parking is another issue...

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how to tell if the amp is running out of steam ... dimming headlights, or maybe with some kind of datalogger to see if it's not getting the juice it needs.

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And of course , an amp could be overloaded without running out of supply power. Just imagine a 10W amp bottoming out - it won't show much on the power rail side. The best way would be to put an oscilloscope on the output, and see if a sine wave clips.

So an armoured car (or better yet, a tank) would be ideal from sound purposes. But parking is another issue...

Somehow I think that parking stops being a problem when you've got a tank .

The amp (Kicker IX405D) has a sub section which outputs 390W (Dynamic Power at 14.4v / 290W (RMS at 12.2v)

As yet, you've not said what load impedance these power figures are delivered to as specified by the manufacturer.

If it's specced for 2 Ohm loads, then the power developed in your two subs is correct. If it's into 4 Ohms, then a 2 Ohm load will only result in half the designed power being delivered.

Hence, I would guess these power ratings are for 4 Ohm loads, and you would be better putting the two subs in series to give a total 4 Ohm load.

The 390w quoted is delivered into 2 ohms as per the manufacturers spec.

2 x 4 ohm subs wired in parallel so the amp is seeing 2 ohms.

No, no.....

Let me re-phrase. I know that you have a 2 Ohm load composed of two 4 Ohm loads.

However, the original spec you quoted just stated the power at peak, and RMS, that the amp delivered. These figures are meaningless unless they also specify the load they are designed to deliver to.

Since you have a 2 Ohm load, and each part of the load is only getting half the power, then that's correct: it implies the amp is designed to deliver 390W RMS into 2 Ohm. No problem there. But that's Ohm's law, so if you now attach just one sub (4 Ohm) you will only get the amp to produce half it's rated output, which is the sub's rated power.

I am no longer sure what you are asking for here, to be honest!

I kind of understand.

According to the specs, the amp does delivery about half that power into a 4 ohm load yes.

The orginal question was to ascertain whether i am under driving my subs. I think maybe I am, given they are rated at 375w RMS (1400w peak !! *crazy*). The amp is only giving 195w RMS .. flat out

I don't really want to run the amp flat out as it is liable to clip / distort so I think a bigger amp may be the order of the day.

Seems as though it needs to be rated at around 750w+ RMS into 2 ohms ... any ideas at under 350 UKP?

I re-read things and I see you are talking about under-powering the subs. In this case, as you have noted already, yes you are. However, 390W is not exactly trivial: even if you drive the speakers at half power, they won't be damaged by the amp. However, if you set up the amp so that it's delivering full power all the time, I would have thought this would not do much for the longevity of the amp!

Can't advise on this, as you are way above my thresholds: however, I would be setting up the amp gains so that it is *just* starting to clip at 0 dB which would set it up nicely for lower output levels.

Watch out for your ears, though - you only get one set as I am discovering to my cost.

Somehow I think that parking stops being a problem when you've got a tank .

Heh, yeah, good point. "Tow this."

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Heh, yeah, good point. "Tow this."

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The parking wardens here in Amsterdam are pretty agressive, and tend to clamp your wheels as soon as you turn your back. Well, turns out that the clamps don't fit on the 9.00x16 truck tyres (as in military truck, not Ford) on the Pink Panther. So now I just have to worry about the sun compass and the smoke grenade launchers getting stolen...

Am I way underpowering my subs

You will (and have) get a variety of different opinions. A lot of it depends on how realistic the manufacturers ratings on the subs and more importantly the amps are. Personally I am a big fan of extra wattage and keeping the gains low. That way you don't have any clipping, everything runs cool, and you are less likely to destroy an amp. I run my two 75W RMS subs off a 500 watt amp with the gains low. The amp stays reasonably cool even though it is in an enclosed space with a blanket and a tool set on top of it (not much space in my jeep) and sounds "cleaner" than the amp I originally purchased which was a closer match to the subs but had would cutout at high volumes after a while.

-Mike

To answer the first question, if the 390 Watts is for a two ohm load, then the subs will be getting half of that each.

Second question, based on my experiences with my brother's system, you are *seriously* underpowering those subs. He is running a single Perfect 10 (i.e. about a third of the cone area you have, from essentially an identical design) from a Rockford Power 500. The amp has a factory certificate stating it'll put out about 750 Watts and the sub is having absolutley no problems with it. The whole of the Perfect range very good but needs a hell of a lot of power.

Third & fourth questions, yes.

Fifth question - Based on my experiences above, these subs will take just about anything you throw at them, so you want something fcuking big IME it's not worth buying amps new, so keep an eye out on all the forums & free ads. Ebay would be a last resort as prices tend to be a bit high there. Good for selling yourold amp though...

I'm guessing you must be in the UK seeing as you quoted your budget in Sterling, if you're anywhere near Reading then you might want to come along to a meet organised by www.talkaudio.co.uk this Sunday. There should be about 30-40 cars there, and rumoured to be coverage by TCA magazine too.

Steve.

OK, let me make sure I have this straight...

-you have (2) 4-Ohm Infinity Perfect 12.1s wired in parallel to produce a 2-Ohm load
-you have an amp which will put 390W RMS into 2-Ohms
-a capacitor of some sort (you didn’t specify)
-This is in a VW Golf but might/will be moved to either a RAV4 or CRV in the not-too-distant future

OK, just so you know where I’m coming from, let me tell you what I have:

-(1) 4-Ohm dual voice coil Infinity Perfect 12.1 with the VCs wired in parallel to produce a 2-Ohm load
-an amp which puts 400W RMS into 2-Ohms (supposedly peaks @ 600W)
-no cap
-this is in the trunk of a Mazda MX-6 (not a huge car, but a bit bigger than your golf.)
-this is in a sealed enclosure that is just a bit smaller than infinity's specs. (What kind of enclosure are yours in?)

Let me say this puts out plenty of bass for my tastes. The perfects are power hungry subs and if you’re using a sealed enclosure they will want even more power (and will be able to handle it) ported enclosures are more efficient power-wise but the sub is more likely to be damaged by to-high power levels.

RAV4's and CRV's aren’t that much bigger than your golf (at least not so much that I think it will make a huge difference)

really, it sounds like you might be happy with just one of those subs and more power going to it. If you could find an amp that would put ~400W into 4-Ohms you would probably be surprised at what that one sub could do. I have infinity kappas up front with 100W running to each one and I have to keep the sub turned down just a bit to keep the bass from drowning them out. I have the gains set so that there is no clipping up to 0 db. With the windows up I rarely turn the volume past -15 dbs. You can’t listen to it at full volume with the windows up.

My point basically is, unless you’re trying to put cracks in the side walk, 2 of those w/ 1000Ws going to them is overkill. That said, right now you are defiantly not getting out of them what you could. If you are dead set on keeping both of them, then ~800Ws is what I would put to them. It will be loud, but you could set the gains low, which is always better than setting them high.

Also, setting the gains properly is very important to getting the most out of your system. I highly recommend this site for instructions on how to set them properly:

http://totoro.efiregate.net/HTMLPages/Tuning/GainSetting/GainSetting.htm

Also, I keep mine crossed over @ 85 Hz so power isn’t wasted trying to produce the higher frequencies, set yours depending on how low your fronts comfortably play, but I personally don’t think these subs sound very good above 100 Hz. I have the sub playing below 85 and the fronts playing above and everything blends nicely.

As always YMMV but I hope this helps and good luck!