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Old     (wakebrdr38)      Join Date: Sep 2006       02-24-2009, 6:21 AM Reply   
The boat is a 86 ski nautique 2001. They didnt come with a stereo but the previous owners had one installed by Buxton Marine in Lewisville. It has a Kenwood deck that is pushing two MTX outdoor all purpose speakers. (like the ones people hang on their patios) The speakers are 8ohm and are rated for 50 watts rms. The deck has just never pushed them the way they should sound. I have always had to take out all base and by the time they are loud enough to hear while driving, they get really distorted.

I have a 600 watt rms marine amp that is 4 channels. Id like to bridge two of those channels and run a sub. My main question is how do i wire the other two speakers into that amp so they are running at 8ohms and keeping it in stereo? Or will 4 ohms and a ton of power work?

Thanks for the input, i know these wiring threads get really old, but site is down and its time for some spring projects!
Old     (jonyb)      Join Date: Nov 2008       02-24-2009, 8:07 AM Reply   
On the speakers you have, connect the + and - of each speaker. That'll be a 4 ohm mono load on 2 channels of the amp.
Old     (philwsailz)      Join Date: Feb 2009       02-24-2009, 8:12 AM Reply   

If we assume that the amp you have is 600 watts RMS at 4-ohms, we can infer that it delivers 150 watts RMS per channel into 4-ohms. Since you have 8-ohm speakers, you will roughly halve the power to each speaker if you put one speaker on each amplifier channel. As a result, and based on these assumptions, your amplifier will put out somewhere around 75 watts into the speakers you have. If the amp is 600 watts PEAK output, the real output might be more like 200 watts RMS, for 50 watts a channel into 4-ohms, and around 25 watts a channel into 8 ohms.
You ask about 4-ohms; there is no way to do that and have stereo with these two speakers; the speakers would have to be wired in parallel to a single channel.

If you were wired only to the head unit with these 8-ohm speakers, you might have been making maybe only 6 watts of power to each speaker.

I am somewhat interested in what you find if and when you install the amp. My hunch is that you will need to engage a hi-pass crossover at 50 - 70 Hz or so, and you will maybe still be dissatisfied. You probably will want to do a more traditional installation with the normal complement of 4 or 6 in boat speakers, and one or two subwooofers. Still, let us know!


(Message edited by philwsailz on February 24, 2009)

(Message edited by philwsailz on February 24, 2009)
Old     (alanp)      Join Date: Apr 2001       02-24-2009, 8:23 AM Reply   
kevin i would say for your amp you'd be better off to just run the speakers you have. i think you'd need a much bigger amp(actually a seperate amp) to make your sub sound decent. what type of sub and what type of amp do you have?

if you wanna run a single amp i would leave channels one and two alone to power the tower speakers and bridge channels 3 and 4 on the amp into a single channel to power the sub. on my amp is i would use the left+ of channel 3 and right- on channel 4 to bridge the amp.
Old     (salty87)      Join Date: Jul 2002       02-24-2009, 9:26 AM Reply   
get another pair of 8 ohm speakers
Old     (wakebrdr38)      Join Date: Sep 2006       02-24-2009, 3:39 PM Reply   
thanks for the info. some of that stuff is confusing to me still. The amp is 1000 watt max but it puts out 600 rms. Max doesnt count for anything so im going to stick with 600 watts rms. I only have 2 speakers and I dont want to add any more. Id rather not mention amp brands or what not because it always ruins these threads. I can say that It has previously run 4 6.5" speakers on the tower and they screamed! So power shouldnt be an issue. Ill try running them to channels 1 and 2 individually. And yes Phil whoever did the install ran them off the head unit, which explains why they sounded like crap when turned up. For the aplication these speakers look great, ill mess with it in the next couple weeks and see what i can do and ill post results back up.

oh and to address Alan, these are for in boat not on a tower. I just want to be able to hear over the straight exhaust when we are cruising around. And your idea of powering the sub is exactly what I was thinking. Its an old sub from my old truck and it doesnt use much power.
Old     (mikeski)      Join Date: Aug 2003       02-24-2009, 11:50 PM Reply   
Add a four channel amp bridged to two channels running the 8 ohm speakers. This nets out to design load on the amp.

You can also run a two channel amp in mono mode with speakers wired in parallel but you will lose the stereo image.

Unfortunately the dummy diagrams that come with amplifier manuals don't usually address this application.

Impedence halves when wired in parallel, doubles when wired in series.
Old     (wakebrdr38)      Join Date: Sep 2006       02-25-2009, 7:24 AM Reply   
can you explain the difference between wired in parallel and in series? Ive always just had 4 ohm speakers and run a speaker per channel according to what each speaker required.
Old     (philwsailz)      Join Date: Feb 2009       02-25-2009, 7:27 AM Reply   
Here is a picture showing the difference between series and parallel speaker wiring

Old     (wakebrdr38)      Join Date: Sep 2006       02-25-2009, 7:38 AM Reply   
intersting...that makes the wiring in a boat rather difficult to do either when the speakers are across from each other and theres no really good place to hide the wire to connect the two that occurs when in series.

Running them at 4ohm wont hurt them right? Sorry again, I just never understood electrical stuff. The pics helped a lot, thanks Phil
Old     (salty87)      Join Date: Jul 2002       02-25-2009, 7:59 AM Reply   
most car stereo and boat stereo speakers are 4 ohm. 8 ohms are more common for home speakers.

this is a layman's description, you can get as technical as you want and prob more accurate, but consider the ohms to be the load on an amp. the ohms are dictated by the speaker. 8 ohms is twice the load of 4 ohms so you're getting less output from the amp with the 8 ohm speakers.

the wiring in a boat with 4 ohm speakers is pretty straight-forward. 8 ohm speakers can't be run at 4 ohm although you can add 2 more 8-ohm speakers and make them look like a 4 ohm load to the amp by wiring them correctly.
Old     (wakebrdr38)      Join Date: Sep 2006       02-25-2009, 8:02 AM Reply   
when the dealership did this for the previous owner they just wired the speakers right into the head unit. Im almost positive the head unit is 4 ohm.
Old     (philwsailz)      Join Date: Feb 2009       02-25-2009, 8:24 AM Reply   

Yeah, the head unit is designed to operate into a 4-ohm load per channel. All mobile head units, (that I know of anyway) are.

Series wiring can be easy too. The picture at the right show the schematic representation of series wiring, but if you think about it, you can accomplish this electrically rather easily. If the wires are run from the speakers to the amp or the radio, you can just take the "+" wire from one, and the "-" wire from the other and tie them together like this:

See how the wires can still be tied together, regardless location? It really is not big deal when the speakers are opposite each other, as long as the wire goes to the same place at the amp or head unit. Tie them together right there by the amp or head unit; no big deal.
Old     (salty87)      Join Date: Jul 2002       02-25-2009, 8:30 AM Reply   
the speaker dictates the ohms, the head unit has to deal with whatever impedence (ohms) the speakers are.

your speakers are 8 ohms, they are a higher impedence than 4 ohm speakers. either switch to 4 ohm speakers or add another pair of 8 ohm...those are really your only choices. more amps with 8 ohm speakers doesn't make any sense, $$ wise.
Old     (wakebrdr38)      Join Date: Sep 2006       02-25-2009, 8:32 AM Reply   
NOW i get it...thanks for all your help. That makes sense now :-)

so ill run them in series and bridge that series. Then use the other 2 channels left to run a sub that is bridged. Thanks again so much guys. Ive been meaning to do this project for 4 years now and just never got around to it.
Old     (philwsailz)      Join Date: Feb 2009       02-25-2009, 8:37 AM Reply   
No no no... Hang on a minute...

If you wire them in series to a pair of bridged amp channels, the power you get out of the amp will be the same as if you just put one speaker on each amp channel. PLUS series wired to a bridged amp will yield a mono signal out of both speakers.

Just wire each speaker to its own amp channel. That will give you stereo sound.
The amp you have will deliver roughly 75 watts to each of the speakers if you just connect a speaker to each amp channel, and use the other half for the sub. It really is just that easy.

I just showed series vs. parallel as there was a question about which was which.

Sorry if I have confused the issue!


(Message edited by philwsailz on February 25, 2009)

(Message edited by philwsailz on February 25, 2009)
Old     (wakebrdr38)      Join Date: Sep 2006       02-25-2009, 8:40 AM Reply   
ok i thought by all the diagrams people were saying to do the series thing.
Old     (philwsailz)      Join Date: Feb 2009       02-25-2009, 8:43 AM Reply   
SO sorry man...

hee hee hee... I didn't want to confuse, and I went and did it!

No, this stuff makes my head spin sometimes, but in this instance, with this product you already have, the simplest thing will in fact be the best!

Thanks for being patient with me!

Old     (david_e_m)      Join Date: Jul 2008       02-25-2009, 10:22 AM Reply   

Your application is safe and it would appear you have plenty of power based on the ratings and impedances.

If the MTX speakers are the model 41 (single 4" & 1/2") or 42 (dual 4" & 1/2") then they are designed strictly to run high-pass from 110 Hz and above.

When you go from head unit to external amplifier, you should have power to spare.

Simply run channels 1 & 2 stereo high pass to the MTX satellites and channels 3 & 4 bridged into the sub (provided the sub is rated at no lower than 4-ohms).

Here's a link to an installation that shows how we installed four conventional coaxials where there were no factory provisions.

Also, here is a diagram that should help clear up your wiring question. Niether series nor parallel should be relevent in your system.

David E.M.

(Message edited by david_e_m on February 25, 2009)
Old     (wakebrdr38)      Join Date: Sep 2006       02-25-2009, 11:50 AM Reply   
thats exactly what mine looks like. The speakers look somewhat different though but the same location! THANKS to everyone for their help!


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