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Bigbopper
10-16-2010, 12:08 PM
Hi everyone, newbie here, this is a great site!

Just upgrading the stereo in my 05 Mobius LSV and looking for some advice.

Here's what I have to work with:

Kenwood KMR330 head unit
JBL MA6004 4 channel amp
6 Polk DB651 speakers.

Since I need to drive 6 speakers, but only have a 4 channel amp, I'm wondering the best way to do this.
I know the left and right rear speakers are run together from the factory but that seems cheesy to me.
Would I be best to run the 4 rear speakers off the amp and the 2 bow speakers off the head unit? Or is there a better way to maximize sound quality with what I have?

Thanks for any help,
BB

sandm
10-16-2010, 12:11 PM
there are several different ways to run that. if it was mine, I'd probably run the bow of 2 channels, then run the 4 cabins off the other 2 channels.

I'm sure that earmark will chime in soon..

Razzman
10-16-2010, 12:32 PM
What sandm said. It sounds like that's how they're run now. That's a common practice that most use to do that, but to be a little more specific run the four cabins in parallel off two channels. In other words run the port two speakers to the left channel + & - and the starboard two speakers to the right channel + & -. Just twist the pairs (+&+, -&-) together and connect at the amp.

You could run the bows off the head unit as you mentioned and the four cabins to each channel but the bows would be underpowered and really un-noticeable, it all depends on what you want.

Brianinpdx
10-16-2010, 12:45 PM
Mr big - welcome to the forums.

You have a couple of choices but to me, in the end there is really only one that makes the most sense. Some people want to maintain L and R in there boat and keep fader control ability. But it makes more effective use of the fader to run the speakers in the bow off the front section of the amp and the cabin speakers off the rear section of the amplifier. This gives you the ability to isolate sound.

Say you have a child or friends with kids and they want to crash for a bit. No problem, have them lay down up front, and then fade the system to rear and it effectively isolates that section. Most tower speakers are pointing to the rear anyway, so you are creating a quiet zone.

As for wiring, this means your amp will be running a 4 ohm load on the front section (1 pair of speakers), and the rear section will be running a 2 ohm load (2 pair of speakers).

--- side note: make sure you have your crossovers on the amplifier set to HP or high pass mode so you have the amplifier sending frequencies that are appropriate for the 6.5" speakers.

- Brian
Exile Audio

sandm
10-16-2010, 12:47 PM
thanks brian :)

Razzman
10-16-2010, 12:55 PM
Yeah what sandm said again :p I'm outta here for the day, gotta go to the VA Hospital, 90 miles each way! :mad:

cab13367
10-16-2010, 01:22 PM
Hi, welcome to the forum. The way that it's wired now is the best way to do it and is a pretty common practice as razzman pointed out. Your amp is rated 60w at 4 ohms and 80 at 2 ohms so the front speakers are getting 60w each and the rear speakers are getting 40w each (since the 80w are being split by two speakers). So for the volume of the fronts and rears to be about equal (with the fader set at 0), the gain on the rear channels should be set a little higher than the gain on the front.

You definitely don't want to use the HU's internal amp as it can't keep up with an external amp and whatever speakers u wire to it will distort long before the external amp driven speakers.

I started from scratch so I went with a JL Audio M6600 6 channel amp but a 4 channel works fine too.

BTW, the Polk db651 is a nice in boat speaker and is a popular upgrade from stock. Many of us on this site are running them.

Bigbopper
10-16-2010, 01:36 PM
Thanks for the welcome and all the great info guys! Gives me a great place to start, I'll let you know how I make out.

BB

EarmarkMarine
10-16-2010, 01:58 PM
The amplifier running all six speakers is the way to go. If you were to run the bow speakers off the head unit then you would have to gain the amplifier up inordinately high in order to keep the head unit, with much less power, from clipping prematurely or running out of juice way before the amplifier. And that would raise the noise floor not to mention create a more narrow sweep on the volume control. In the end the head can't keep pace despite the similar power ratings.
As the impedance is lowered in the cockpit due to the paralled speakers the need for amplifier input gain is reduced. This is where you will start to set your gain. Then you will move onto the bow and match those speakers at the identical output level. Technically, once you level match, all six speakers will be getting the identical 40 watts.
And yes, set all channels to the lowest highpass setting or around 50 Hz. You will not be reducing any frequency that a 6 1/2 could otherwise produce but by limiting the amplifier responsibilty and the speaker bandwidth/unnecessary
excursions, the coaxials will play louder, sound cleaner and handle more power.

David
Earmark Marine

Bigbopper
10-17-2010, 12:52 PM
Thanks David, more great info. I'll make sure to print off this thread as a guide when I get everything installed and setup.

Cheers,
BB

lewisb13
10-17-2010, 01:40 PM
I cant wait to see where you mount your amp(s). We have ZERO room in our boats...(05)

Bigbopper
11-02-2010, 07:35 PM
All done. Sounds awesome and everything tucked away nice and tidy. My old Kenwood wireless remote even works with the new Kenwood deck!!

cab13367
11-02-2010, 09:30 PM
Let's see some pics!

Bigbopper
11-02-2010, 11:33 PM
I'll have to wait till the weekend to take pics but will post a few.
Thanks again for all the help!

BB

Bigbopper
11-05-2010, 02:05 AM
Here's a few crappy pics of the completed install. Not sure what's wrong with my camera??

I did the stainless cup holders too while I was at it.....

cab13367
11-05-2010, 10:38 AM
Nice job, looks good. As far as your camera, maybe the autofocus switch is set to "OFF", if it has one.