Some questions I just cant find answers for...

[Fortiori]

Ok so I've spent a few hours looking through the stickys and while they have helped greatly there is still a few things I don't understand...

Background: I have a VX Exec (2000 model) with a Pioneer DEH-P5150UB which has seperate RCA out for Front, Rear and Subwoofer.

I am planning/considering putting in a Kenwood kac-m845 (4 channel 720w) amp which has the following outputs:
• 60W x 4 at 4ohms (20-20kHz 1.0% THD)
• 90W x 4 at 2ohms (1kHz 1.0% THD)
• 180W x2 at Bridged 4ohms (1kHz 1.0%THD)
(FYI: Using a Kenwood 3012box 12'' Sub)

To me that looks like 4 60w speakers, 4 90w speakers and 2 sub woofers but I'm guessing that is wrong?

Also, as I am doing the install myself, I have a couple noob questions about installation. Is there anything wrong with mounting the amp under the parcel shelf? Also, when fitting splits where is the best place to mount all the components?

Thanks heaps for any help

[paynetrainvy]

In regards to mounting the amp there will be people who will say yay or nay, I myself mounted my clarion amp upside down on the parcel shelf I've had it there for 12 months an it has never missed a beat or got extremely hot.

[HCVP]

Your getting yourself confused with the impedance levels (ohms) and the amount of outputs the amplifier has.

The amp has 2 different power ratings for each of it's 4 channels, as it is stable at 2 different impedance levels, both 4 and 2 ohm.

The 2 ohm rating is pretty much irrelevant as the majority of aftermarket speakers have a 4 ohm impedance anyway.

What is the amp supposed to be running? I ask because you mentioned a 12'' sub, nothing about speakers, and then a 4 ch amp.

Exactly what components are you reffering to with regards to installation? A bit more detail is requited until we can ask your questions in full.

[Fortiori]

Thanks for al your replies.

At the moment I have the pioneer h/u with Front and rear door speakers that came with the h/u (cheap 25w). I want to replace the front speakers with 6'' splits (thats what i meant by components) and have these and the sub running off the amp while keeping the rear speakers running from the h/u.

[acarmody]

The only change I would make is just leave the rear door speakers unplugged. If they are crap than don't mess up the better quality of the front splits by having the rears foul up the air.

Other than that, make sure the splits are capable of handling about 60wrms at 4-ohms, to utilise the amp, and the sub about 180wrms, and make sure it is a SVC (single voice coil) 4-ohm sub, or a DVC (dual voice coil) 2-ohm sub. Though I'm guessing most of the lower end subs will be 4-ohm SVC subs.

[Fortiori]

acarmody,
The splits I have in mind have a 120 RMS at 4 ohms and the sub is a 400 RMS SVC at 4 ohms although it does say something about a '2- layer voice cone'.

My real question right now is how much can I actually run off this amp? Just the front splits and a sub? Or do I make provision for some rear splits / 6x9s?

[acarmody]

Just the fronts and the sub, and even there you are seriously underpowering them all.

You might want to seriously consider getting some bigger amps.

And don't worry about the '2-layer voice cone' thats just marketing.

[HCVP]

Have you actually bought the sub yet or just picked it out? SVC subs can make it difficult when trying to find an amp on a tight budget that offers enough power to really drive a 400 watt rms sub.

Their are plenty of entry level subs that will be rated continously around the 400 rms mark, but as far as amps go, you won't find a entry level amp that will produce those kind of figures at 4 ohm which is what most SVC subs are. Opting to spend just a little more getting a DVC sub can save you money when purchasing an amp.

Also as mentioned, that amp is WAY to small for the task, limiting the performance of both your front speakers and your sub.

[Fortiori]

Thanks heaps for your help so far... EDIT: Also the penny has finally dropped on why I was reading the specs of the amp wrong... Thanks

The only thing I've actually bought is the H/U at this stage and everything else is planning as I knew I'd screw up somewhere in the figures.

What would you recommend? Obviously I'd like to run the front splits somewhere a lot closer to what they were designed for... And I dont mind spending a little more for a DVC sub. Can you recommend a amp/sub combo to suit?

[Fortiori]

Ok I've done some hunting and come up with the Fusion CA-AM41200 amp and Pioneer 308D4SB 12" Subwoofers In Box. The amp's Specs are: 110W RMS x 4 @ 4Ω 1%THD+N; 150W RMS x 4 @ 2Ω 1% THD+N; 300W RMS x 2 @ 4Ω Bridged 1% THD+N and the sub is 400w RMS with 2 ohm DVC.
What do you think?

... I'm assuming I can bridge 2 channels to run 300W RMS to the sub and leave 2 channels to run the front speakers at 110W RMS? And how does it work if the amp produces 300W RMS @ 4ohm, does it then produce more at 2ohm?

[Fortiori]

Hey if anyone could clarify that last question for me that would be great...

[acarmody]

Yes that amp can run the front speakers and be bridged to run the sub, as long as its the dual 2-ohm version like you said. Model should be TS-W308D2SB.

And when the amp is bridged like that, channels 3 + 4 are already running at 2-ohm each, internally the amp is running the two channel in series to create the 4-ohm impedance. So if you try and hook up a 2-ohm sub to the bridged channels, you are effectively running those channels at 1-ohm each and the amp can't do that.

[Fortiori]

Thanks heaps!
I haven't bought the sub yet so I'll just make sure its a dual 2 ohm voice coil design. The one in the link was dual 4 ohm, thanks for picking that up.

[acarmody]

No problem. Once you have the sub make sure you wire it up properly or you will prsent a 1-ohm load to the amp, which means 0.5-ohms per channel. If the protect doesn't kick in, it will be VERY loud........for about 2 seconds.

[Fortiori]

Yeah will do... Don't feel like being deaf or blowing anything up. Just checking I Know what im doing with bridging... You just connect the positive terminal to one channel and the negative to the other right?

[acarmody]

The positive from the sub goes to the positive on channel 3 and the negative from the sub goes to the negative of channel 4. And then the sub is wired like this,

[Fortiori]

Awesome, thanks again.