Re-wiring a Supra GG sound system

lakeboarder · Posted: May 03, 2006 6:58 pm Post subject: Re-wiring a Supra GG sound system

I have a Kenwood KDC-MPV5025 head unit and two Kenwood KAC-8401 amps (640 w each) which are installed in a 2004 Supra Gravity games boat. Today I re-wired the system from the way the factory had installed it to get better control. There are 8 speakers and a sub installed. Four are Kenwood speakers (4 ohms) and are installed two in the bow and two in the main cockpit. Four are MB Quarts (4 ohms) as provided by Mako industries as tower speakers for wakeboarding. The factory install had the front and rear outputs run to one amp with the line out feeding the second amp. The first amp had the bow speakers on channel A and the cockpit speakers on channel B. The second amp had all four tower speakers hooked up in parallel on channel A and the sub on channel B. This worked OK but the fader control worked on the bow and cockpit speakers with no control for the sub and tower speakers. If you cranked it enough to hear it behind the boat it was way too load in the cockpit and/or bow. This also put way more wattage into the bow and cockpit speakers than to the four tower speakers since one side of the amp was powering all four tower speakers and the two cockpit and two bow speakers each had side.

Anyway, I wanted to use the fader to increase the volume to the tower without blowing out the people in the boat. I re-wired the system as follows; amp 1 is now fed from the front output from the head unit. Amp 2 is fed from the rear output from the head unit. Amp 1 is set up as a single input four channel system with the four boat speakers wired in parallel and powered off of channel A. The sub is powered off of channel B (bridged). The amp has some crossover filters so I set the high filter on for channel A and set it at about 150 Hz as recommended. Channel B has the low filter on and is set to 150 Hz and has the bass boost on.

Amp 2 is set up as a single input bridged two channel system and feeds all four of the tower speakers again wired in parallel. The high filters are on and set to 150 Hz.

The fader now works like I want but at what seems like a fairly high but not excessive volume the speakers start cutting out. The amp specs call for 2 ohms or greater for stereo and 4 ohms or greater for bridged connections. So I’m thinking I should re-wire the tower speakers in series which should give them an 8 ohm load?

I’m pretty good with home audio gear but don’t have much experience with 12 volt stuff. Any ideas? Does re-wirring for 8 ohms sound like the right fix?
Any help is appreciated.

By the way I'm thinking about replacing the MBQ's with two kicker SS65.2's (componants) and two SSMB6's (Midbass) but I want to sort out the problems first.

lowdrag · Outlaw Joined: 28 Aug 2003 Posts: 188

Your amps should be stable to 2 ohms as long as you're not running it bridged. How about running your tower speakers in pairs to amp 2. Running 2 speakers in parallel to each channel of the amp would give you a 2 ohm load unbridged. Other than that, you could run a parallel series with all 4 speakers which would bring them back to 4 ohms and allow you to still run the amp bridged if you want to.

If you're running all 4 tower speakers in parallel to one bridged channel on the amp, I believe it would be running at .5 ohms which would most definitely send the amp into a protection mode when you turn it up.

lakeboarder · Posted: May 03, 2006 9:13 pm Post subject:

I'm running the 4 channel amp bridged to two channels. I would run all four speakers to seperate channels but the tower wiring is two channels split at the top of the tower. Sounds like I should try running in series. Wouldn't that give me 8 ohms though, not 4?

tmbrown · Outlaw Joined: 03 Jul 2004 Posts: 218 City: East Roseville

keep in mind with most amps, as ohms drop, wattage increases - and vice versa... you could be over or under powering your speakers. 4 ohms is the basic standard for 12V stuff... if you can keep it there, you should get what the amp is rated for. Trying the 8ohms would tell you if you're overpowering - or possibly run 2 more wires and just take advantage of all four channels...

One other option may be to bridge down to one channel - then run each pair of speakers in series - then parallel those into the amp - that'll cut the amps, then double them back up = leaving you right back at 4 ohms.

Worth trying.

lakeboarder · Posted: May 04, 2006 4:24 pm Post subject:

I went ahead and re-wired the speakers in series. Everything is working great! I hadn't thought about bridging to one channel. I suppose stereo separation isn't an issue 80 ft back with the speakers spaced about 18" on center! Anyway the system sounds way better that it did before. The music behind the boat is much clearer without all the distortion. I was about ready to just replace the entire thing and spend a few thousand up-grading. Now I might replace a few of the speakers but otherwise it sounds great. A nice up grade for just a few hours work.

lowdrag · Outlaw Joined: 28 Aug 2003 Posts: 188

Sorry, I guess I gave you some bum advice before. I did a quick look and thought it was only a 2 channel amp and not a 4. That's why I mentioned bridging to one channel. You'd probably get a little more out of it if you could run all four speakers seperately to the four channels at 4 ohms, but if its doing what you want it do now thats what counts. Enjoy!