4 channel headunit powering 6 speakers

[klennop]

Hey guys,
I haven't dug into this too much yet but I noticed my head unit is a 4 channel unit. I also have the amp which powers the sub. However, does anyone know how they convert the 4 channels of the head unit to the 6 speakers? Down the road I will upgrade and I notice some manufacturers make a 6 channel head unit but I am wondering how that conversion would work without running all new speaker wire.

Also how much success has anyone had with the remote working after they upgraded.

Thanks!

[Mr Hahn]

Ok, I'm replying under the assumption that you have 4 ohm speakers because it's most likely to be the case here.

If you connect two 4 ohm speakers together in parallel the result is a 2 ohms load on your head unit. A constant 2 ohm load placed on 2 of the 4 channels of your head unit could kill it unless it's rated for this, most are not.

If you connect two 4 ohm speakers in series the result is an 8 ohms load on your head unit. This is far less hazardous to your head unit, but greatly reduces the already minimal power your getting out of it. This probably will not sound very good, but it's the safest thing to try without changing any equipment.

You could buy a small and somewhat cheap class D 4 channel amp like the Alpine KTP-445U Power Pack.
• Link: https://www.crutchfield.com/p_500KTP445 ... -Pack.html

This would give you options like:
1) Use the KTP-445U to power the 4 rear speakers and let the head unit power the pair in the bow.
2) Pair up the 4 rear speakers in series for a 2 ohm load, and leave the 2 front speakers as a 4 ohm load. This works for the Alpine KTP-445A and not on the head unit alone because this amp is stable at 2 and 4 ohms.
Also, this does not require new wires run to the speakers all of the connections would be behind the current stereo head unit, and the amp could probably be mounted back there quite easily unless your spot is extremely confined for some reason.


-Nate

[klennop]

I get the parallel/series, etc. and understand what I could do. I am not sure what the stock setup is, that is what I was wondering.

Think how weird it would be to to run 1 pair of speakers of the conventional 2 channels and then the other 2 pairs of speakers off the other 2 channels of the head unit. Seems like a odd way to do this, especially from the factory. Unless there is another small amplifier running one of the pairs that I don't know about?

[jhnmdahl]

Klen,

It's almost certainly two pairs being run in series as Mr. Hahn suggested. One easy way to check is pull a speaker and unplug a wire, and see if it kills sound to another speaker on the same side of the boat - a dead giveaway that the two speakers involved are wired in series. For checking in parallel, you can hook a 1.5v battery to the terminals at one speaker (still wired up to the amplifier, while shut off) and see if any other speakers on the same side of the boat move along with the speaker to which you connect the battery.

John

[Big Block Power]

I would say the port side bow speaker is tied into the port side front cockpit speaker. Once you peel off the panel that covers the back side of the radio you still really see some fancy wiring I ran all new wires to mine because of their fancy wiring.

[sailor55330]

Ok, I'm replying under the assumption that you have 4 ohm speakers because it's most likely to be the case here.

If you connect two 4 ohm speakers together in parallel the result is a 2 ohms load on your head unit. A constant 2 ohm load placed on 2 of the 4 channels of your head unit could kill it unless it's rated for this, most are not.

If you connect two 4 ohm speakers in series the result is an 8 ohms load on your head unit. This is far less hazardous to your head unit, but greatly reduces the already minimal power your getting out of it. This probably will not sound very good, but it's the safest thing to try without changing any equipment.

You could buy a small and somewhat cheap class D 4 channel amp like the Alpine KTP-445U Power Pack.
• Link: https://www.crutchfield.com/p_500KTP445 ... -Pack.html

This would give you options like:
1) Use the KTP-445U to power the 4 rear speakers and let the head unit power the pair in the bow.
2) Pair up the 4 rear speakers in series for a 2 ohm load, and leave the 2 front speakers as a 4 ohm load. This works for the Alpine KTP-445A and not on the head unit alone because this amp is stable at 2 and 4 ohms.
Also, this does not require new wires run to the speakers all of the connections would be behind the current stereo head unit, and the amp could probably be mounted back there quite easily unless your spot is extremely confined for some reason.


-Nate

This is some pretty good advice. I would add that for anyone who is looking at using the stock power on a head unit, do not be fooled by the wattage stated. That wattage is almost always peak wattage and not sustained. I used to dabble in car stereos a little (I had single 10 sub system in an expedition that would easily hit a measured 150db). That wattage is what the head unit can attain for one split second. If you want to drive speakers at a higher volume in a big space such as on a boat for a length of time, you're going to need more power. I would actually recommend a six channel amp. As mentioned you could wire the 4 rears for a 2 ohm load, but even though the amp suggested might be stable, it will likely produce more heat and it is more strain on the amp internally, plus heat on a boat is never good. I do like the idea of a class D amp as they usually run cooler. I would also agree with staying away from an 8ohm load in a car/boat (however, it works fine at home).

In my boat, I have the factory Rockford Fosgate system. There are two installed 2 amps--One for the main speakers (6) and one for the sub (10" I think). I will say it's actually pretty impressive for an open air sound.

When it comes to audio, there's power and then there's clean power. Good separate amps will always destroy even the best integrated head unit amp.

[Mr Hahn]

I did some checking around, most of these Cobalts from the 90's and 2000's with a 6 speaker setup seem to be wired like BB said above. Port side bow and middle are together in series, aft speaker solo on it's own channel, and then the same thing on the starboard side. No external amplifier, just the head unit powering all 6 speakers. I also learned Cobalt isn't exactly known for amazing sound systems in these years. To verify this you can do the battery test mentioned by jhnmdahl above, or you can unplug the speaker wires from the back of the head unit and do a resistance test with a multi meter. The two channels for the speaker pairs linked in series should have around 6-8 ohm resistance through the speakers and back, the solo channels should have around 3-4 ohm resistance.

Here's what I would recommend to improve the sound for you, or anybody else that reads this thread:

1) Replace the head unit. You could add an amp like I mentioned above, but if that's not enough for you then you'll just end up quickly replacing it. The head unit I recommend (and I just ordered today for my own Cobalt 232) is the Sony MEX-M100BT Marine CD receiver with Bluetooth. This head unit is pretty unique right now because it basically has one of those Class D bricks (like the Alpine KTP-445U I talked about above) built right into it and it's rated at a continuous 40W x 4 RMS and a peak of 100W x 4 all by itself. This gives you the benefit of a new amp and a new head unit in a two for one purchase with very little installation work.
• Bonus, it's a Sony like your factory head unit so it should be almost plug and play, and it's also most likely to work with your original Sony remotes without any additional equipment. You could probably call Sony or Crutchfield to verify this if you give them the model number of your current head unit. Also, I said "almost" plug and play because you will definitely want to run a dedicated power wire (probably something like 12 gauge) to the battery and to a good ground point to feed that bigger than normal internal amp.
• Another bonus, you could probably run your speakers in series OR in parallel if you want. It's not specifically rated for a 2 ohm load in the specs, but the Class D amps inside should handle 2 ohm just fine as a few car audio tests have shown. Here's a video link of it being dyno tested by Sonic Electonix at both 4 ohm and 2 ohm, and they said Sony told them that it's fine to do both. Also note that they tested the MEX-XB100BT, which internally is the exact same thing as the MEX-M100BT, just without some waterproofing for use in cars: https://www.youtube.com/watch?v=0zkLwQVHxfI
• Up until last week this head unit was $270, it just went on sale for $200 starting this week. They're probably getting rid of current stock before a new 2018 version gets released. https://www.crutchfield.com/p_158M100BT ... 100BT.html

2) Replace the speakers. New speakers with the old head unit are not going to do much, garbage in and garbage out, so that's why I placed them at number 2 on the list. You'll want to get something with a higher sensitivity (-90 db is more sensitive than -80 db) to make the most of that 40 watts of power you give them from the head unit. I've used both the JBL GTO series and the Polk DB series in the past. They both have great sensitivity and neither of them are really expensive, but they're still both good quality speakers. I like the Polk speakers better because they are rated for, and respond better to, the lower frequencies for maximum bass response without a dedicated subwoofer. These are also rated up to a continuous 120W rms and a Peak of 360W, so they'll still work really well if you go with a bigger external amp to make more noise later. I purchased a 4-pack of Polk DB651 speakers for my boat on Amazon for $120 here: https://www.amazon.com/gp/product/B00MI ... UTF8&psc=1

3) Now if you're still not happy with the sound you can add a bigger amp and/or a subwoofer and there's lots of ways it could go from here, as the OP klennop already did on his boat. Personally, I think I'll be happy with just the above on my boat. If for some reason I decide I really want a little more base I might add a single channel amp to the system. In fact, while writing this I just remembered I have an unused 10" Infinity subwoofer sitting above my garage from an old car audio project, so if I can find a cheap enclosure and a cheap mono amp that I like I'll probably blow the dust off that box add it to my boat.

I would not worry about running new speaker wires until you get to step 3 and add power amplifiers that exceed 40W rms per channel. I might on my boat if it's easy to reach and pull them though, but only because I have half a spool still sitting in my garage from my last project on a car a couple years ago.

Final tip for the readers, don't crimp or twist wires together on boats, cars, trucks, etc. If you just solder, then use a dab of liquid electical tape, and then cover it with self sealing heat shrink it really won't add too much time to the job and will save you soooooo much hassle chasing loose or corroded connections later on. There you go, sorry this post turned into a book.

-Nate

[klennop]

Thanks everyone for the insight/opinions.

Nate you pretty much read my mind. I grew up having high end audio in my vehicles, heck most of the time the system was worth more than the cars, lol! I just choose to spend my money on other things today.

That Sony unit is what sparked my interest. I am not a big Sony guy but for the power, possible remote usage, etc. it is a pretty easy plug and play. I saw that same video where they put it on a test bench and it was stable down to 2 ohm. If I recall it was like 65 or 67 RMS, that is CRAZY for a headunit. Even at 4 ohm, it was like 42 or 43 RMS, heck that is peak power on most headunits.

I don't need or want anything crazy and the Polks are great speakers. I would probably end up with JL or the Polks when I upgrade.

[Big Block Power]

K I ran into the plug and play issue on my boats. Yours is a few years newer than mine. Sony had a larger plug in during my years. The new head unit has a much smaller plug. Do you might still be doing some rewiring. Just to give you a heads up. I'm sure your ready for the task.

[Bfun220]

Looking to run new speaker wire and have a question. How are the wires run from the port side to the starboard side ? Do they run up and around the bow ?

[Big Block Power]

Looking to run new speaker wire and have a question. How are the wires run from the port side to the starboard side ? Do they run up and around the bow ?

Yes and that's how I ran them. There's conduit all the way around.

[ColinC]

Good to hear as I am planning to run new wire as part of my upgrade. Did you use the old wire to pull the new wire through the conduit? Apologies if that's a dumb question -- I'm a newb at this boat wiring thing...

[Ytmsn]

I just swapped my head unit out for one that has BT and works with my remotes. I already have separate amps for the sub. Works good!

20180405_201630.jpg

[AsLan7]

I just swapped my head unit out for one that has BT and works with my remotes. I already have separate amps for the sub. Works good!
20180405_201630.jpg

Hey, welcome to the Sony head unit club YT!

[Big Block Power]

Good to hear as I am planning to run new wire as part of my upgrade. Did you use the old wire to pull the new wire through the conduit? Apologies if that's a dumb question -- I'm a newb at this boat wiring thing...

No I left all of the old wiring in there. You can reach most of the conduit. I use conduit lightly. It's like a tube cut in half they run the wires in. They screw the tube to the rub rail area. You should be able to reach it going threw your speakers and storage areas. Look in your engine area the tube/conduit is back there too. It like clips together on top.