Installing new stereo head (Kenwood KMR-M308BT) with amps

[newcomlr]

Audio noob here. Old stereo head unit gave out. Purchased a new Kenwood KMR-M308BT Marine head unit. Below is a pic of the back of the unit. Has normal wiring harness with wires for speakers and one set up output jacks for rear/subwoofer connection. The port to the left of the output red jack is for a Sirius tuner.

My question is I wanted to hook up one amp for speakers and one amp for subwoofer. Doesn't appear possible? I have one two channel amp...can I use one channel for subwoofer and the other channel for the speakers? The only other option would appear to direct connect the speakers so they are only powered by the head unit amp (50W) and then connect an amp to only power the subwoofer.

Am I missing another option?

 

[Tail_Gunner]

Re: Installing new stereo head (Kenwood KMR-M308BT) with amps

Kenwood KMR-M308BT Marine digital media receiver at Crutchfield.com


General
CEA-2006 Compliant No
RMS Power Output 22 watts
Peak Output 50 watts
RMS Power Bandwidth 20-20KHz
Preamp Outputs 2-channel
Sub Preamp Outputs No.................................:friendly_wink:
Switchable Rear Preamp Outputs Yes
Preamp Voltage 2.5 volts
Display Color White
Key Button Color Blue
EQ Bands 3
Wireless Remote No
Steering Wheel Control Compatible Adapter required
Parts Warranty 1 Year
Labor Warranty 1 Year
Expandability

Type and model number of your amp

 

[newcomlr]

Re: Installing new stereo head (Kenwood KMR-M308BT) with amps

So what can I use the Preamp Output 2-channel output for?

I'm okay if either the speakers or the sub are not powered by a separate amp. But assumed I could hook up at least one amp..possibly a two channel amp. Can I use one channel for subwoofer and the other channel for the speakers?

 

[OllieC]

Re: Installing new stereo head (Kenwood KMR-M308BT) with amps

Does your AMP have a set of pre-outs? Can you bridge the 2 channel AMP you have now for the sub? If not get a 4 channel AMP for your regular 6.5" speakers, with a PRE-Out - run the PRe-Out to the 2 channel AMPs input, and bridge the L&R channels to your sub. It's very important that you run the correct size TINNED marine power cabe for the AMPs. 4/0 for both +&-.

JL Audio M400/4 Marine amplifier — 75 watts RMS x 4 at Crutchfield.com

 

[Tail_Gunner]

Re: Installing new stereo head (Kenwood KMR-M308BT) with amps

Jbl 4 Channel 160W amp - Prospec MA6004

Same

 

[bruceb58]

Re: Installing new stereo head (Kenwood KMR-M308BT) with amps

Those pre amp outputs are for a sub woofer. If you want an amp for your primary speakers, buy a head unit that gives you more pre amp outputs.

Marine | CAR ENTERTAINMENT | Kenwood USA
The top 2 have them.

 

[Tail_Gunner]

Re: Installing new stereo head (Kenwood KMR-M308BT) with amps

Those pre amp outputs are for a sub woofer. If you want an amp for your primary speakers, buy a head unit that gives you more pre amp outputs.

Marine | CAR ENTERTAINMENT | Kenwood USA


The top 2 have them.

That jbl should work fine..just plug the pre-out to the head unit into the amp..take short jumper cables run from the amp's preout to the rear channels input .....select the hp filter and viloa one has a sub channel

Marine Certified Yes
Amplifier Class AB
Number of Channels 4
Total RMS Power Output 320 watts
Maximum Input Gauge Size 4 AWG
Minimum Impedance Unbridged 2 ohms
Minimum Impedance Bridged 4 ohms
THD at Rated RMS Power 1%
Speaker Level Inputs No
Preamp Outputs 1 pair........:joyous:
Built-in Crossover Low-pass (LP).....
High-pass (HP)..........:joyous:
Full (AP)...............
High-Pass Crossover Frequency 32 - 320 Hz
Low-Pass Crossover Frequency 32 - 320 Hz
Signal-to-Noise Ratio 80 dB
Bass Boost 0 - 6 dB
Bass/Gain Remote No
Fan Cooled No
Fuse Rating 25A x 2
CEA-2006 Compliant Yes
Warranty and Return Policy

 

[bruceb58]

Re: Installing new stereo head (Kenwood KMR-M308BT) with amps

That jbl should work fine..just plug the pre-out to the head unit into the amp..take short jumper cables run from the amp's preout to the rear channels input .....select the hp filter and viloa one has a sub channel

So...how does he implement a fader?

The next more expensive head unit that has 3 sets of preamp outs is an additional $40.

 

[Tail_Gunner]

Re: Installing new stereo head (Kenwood KMR-M308BT) with amps

Good question i assume he's on a budget maybe not. but that unit has gain control's and will run quite nicely for a two or speaker's with a sub..just no fader option.

 

[Slide]

Re: Installing new stereo head (Kenwood KMR-M308BT) with amps

Audio noob here. Old stereo head unit gave out. Purchased a new Kenwood KMR-M308BT Marine head unit. Below is a pic of the back of the unit. Has normal wiring harness with wires for speakers and one set up output jacks for rear/subwoofer connection. The port to the left of the output red jack is for a Sirius tuner.

My question is I wanted to hook up one amp for speakers and one amp for subwoofer. Doesn't appear possible? I have one two channel amp...can I use one channel for subwoofer and the other channel for the speakers? The only other option would appear to direct connect the speakers so they are only powered by the head unit amp (50W) and then connect an amp to only power the subwoofer.

Am I missing another option?

View attachment 229912

The RCAs on your head unit will supply a full range signal. You can connect them to any amplifier and use the amp's built-in high/low-pass filters to adjust for your speaker or sub range.

Many amplifiers include a set of pass-through RCA outs that carry the original full range signal through to the next amplifier. This would be the best option for your system. A less ideal option is to run a Y splitter at the end of your RCAs from the head unit and connect those to your two amplifiers.

You will not get fader functionality or be able to adjust the levels or filters individually for your front and rear channels. If they're all the same type of speaker it's not really a big deal.

Also I saw someone recommend 4/0 gauge power/ground cables, this is MAJOR overkill. This page at Crutchfield describes how to size your wiring.

 

[newcomlr]

Re: Installing new stereo head (Kenwood KMR-M308BT) with amps

All great feedback. Yes..on budget. Hooked sub amp up to pre-outs, speakers to pigtail wires. Subs sounds awesome. Speakers sound like crap. Checked and changed polarity. No difference.
Noticed the large cone of the speakers (KFC-1652MRW 6.5" 2-Way Marine Speaker) not moving. Checked equalizer settings and even boosted mid range to max. No change. Essentially all I'm getting is tweeter output.

The reason I bought the new head unit was because I deduced that both speakers didn't suddenly go bad while parked last year. Now I think the speakers are bad. Going to borrow somebody's spares and test.

Back to the amp, one of my amps (old Kicker ZRX) has what I believe is pass thru outlets so I should be able to test that.

 

[newcomlr]

Re: Installing new stereo head (Kenwood KMR-M308BT) with amps

Any reason why I can't/shouldn't use a line out converter? Leave sub amp hooked to factory RCA pre-outs on head unit. Attach head speaker wires to Line Out Converter, plug second amp to the LOC.

 

[Slide]

Re: Installing new stereo head (Kenwood KMR-M308BT) with amps

Any reason why I can't/shouldn't use a line out converter? Leave sub amp hooked to factory RCA pre-outs on head unit. Attach head speaker wires to Line Out Converter, plug second amp to the LOC.

That's another possible solution, just more complicated. Your signal may not be as "clean" either.

 

[newcomlr]

Re: Installing new stereo head (Kenwood KMR-M308BT) with amps

For now I just elected to install decent low watt speakers (Pioneer TS-MR1640) direct to the head. Sound great! Did have to reduce the gain on the sub amp. Maybe in the future I'll add some higher watt speakers and connect to the 200RMS Watt amp.

I went ahead and bought a line-out converter at walmart or I can try the pass through output on the subamp. I'm sure one of those options will work.

Thanks for the input!

 

[tlgrooms]

Hi all, I am a noob also when it comes to using an external amp. I have this same head unit and am trying to hook this four port amplifier up to it.

http://www.ebay.com/itm/Nitro-BMWX4...pt=Car_Amplifiers&hash=item461ed1ecd1&vxp=mtr

I am trying to use this on a motorcycle with four 5 & 1/4 inch speakers. I have tried hooking 2 RCA Y splitters to the ports on the amp and then
hooking the speaker wires from the amp to the speakers. No matter how I hook it up the sound is always stronger on the left set of speakers.

Is it possible to use this amp with this head unit?

Thanks for any help/suggestions.