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dirtk38
04-26-2011, 11:10 PM
Looking to do some upgrades to the sound system, and I've got two questions that are probably stupid. As an engineer, I'm almost ashamed that I have to ask them. But I'll swallow my pride!

1. I've got 4 3-ohm speakers in the boat, and 4 4-ohm speakers on the tower (all full-range, no subs). Can I power all of these with a single 6-channel amp? I know Pyle isn't exactly a high-quality brand, but I picked up one of these for cheap: http://www.pyleaudio.com/itemdetail.asp?model=PLMRA620. My thinking is that I could wire the 3-ohm speakers in 4-channel mode, then bridge channels 5 and 6, and wire the 4 ohm speakers to present a single 4-ohm load (wire each pair in parallel, then connect the pairs in series). Will that work or am I crazy?

2. Assuming I can wire the tower speakers as described above, I was trying to find a clean way to get the wires through the hull. I came across this plug from Perko: http://www.perko.com/catalog/category/lighting_fixtures/product/357/ This would let me easily remove the unplug the speaker wires when i have to fold down or remove the tower. Question here is whether the plug can handle the power that will run through it. According to Perko, the plug is "Rated for 15 Amps at 12, 24 and 32 Volts." If the speakers are wired for 4 ohms, and the amp puts out 400W RMS at 4-ohms in bridged mode, will I melt the plug? I calculate Voltage=sqrt(400W*4ohm)=40V, and Current=40V/4ohm=10A. Since I'm comfortably below the 15A limit, will it kill the plug to handle 40V?

Thanks!!

Thrall
04-27-2011, 01:16 AM
"As an engineer, I'm almost ashamed that I have to ask them." I'll have to send this to my buddy that went to Auburn! haha
Just joking man!
Your theory is correct with the resistance the amp will see and you don't want to parallel the 3ohm speakers, it will fry the amp. I'd bet a Pyle amp isn't even 2ohm stable (says it is though:confused:).
Looks like that amp is basically a 100W/ch RMS amp (probably at 14.4V input too which is ideal, not realisitc). If your 3ohm spkrs are high quality and can handle 100W RMS and the 4ohm tower speakers are weak, then set it up how you described, just to get a little sound out of the tower spkrs.
If the amp is 2ohm stable, why not parallel 2 tower speakers each to ch 5 and 6, will present a 2ohm load to each channel, and maximize "safe" power output from the amp.
Or if you want more volume out of the tower speakers, wire each pr of 3ohm speakers in sereies to 2 channels (6 ohm load the amp sees, easy on the amp but not the most power output) and go 1:1 to the tower speakers.
I'm an engr too, but check out this cheat sheet!
www.bcae1.com

I see no reason that plug wouldn't handle your original configuration but do you really want to put holes on the deck for something that isn't an ideal setup?
Most tower wiring is hidden from the tower leg into the deck, hole under the center of the tube. See if this is possible before adding more connections in the speaker wire.

dirtk38
04-27-2011, 08:27 AM
"As an engineer, I'm almost ashamed that I have to ask them." I'll have to send this to my buddy that went to Auburn! haha
Just joking man!.
In my defense, I studied wireless engineering at Auburn...this stuff involves wires!!

Thanks for confirming my theory. One of my goals with that setup was to minimize the number of wires that I had to run down the tower. However, if I can find a good way to run two pair, then I may do what you suggested (each tower speaker on its own channel). The 3-ohm speakers are some nice Polks that are currently running on a mediocre Sony amp, but the tower speakers are crappy kenwoods that werent hooked up when I bought the boat. So, I'm just trying to make a little sound...not trying to blow everyone out of the water!

I've still got more investigation to do on the wire running, but so far I don't see a clean way to get the wire from the tower leg to beneath the observer seat without drilling a hole somewhere.

rspiecha
04-27-2011, 11:38 AM
I studied wired engineering at Auburn, and fluid dynamics of cold, wet, yellowish liquid while inverted :)

Rob

JimN
04-27-2011, 12:05 PM
In my defense, I studied wireless engineering at Auburn...this stuff involves wires!!

Thanks for confirming my theory. One of my goals with that setup was to minimize the number of wires that I had to run down the tower. However, if I can find a good way to run two pair, then I may do what you suggested (each tower speaker on its own channel). The 3-ohm speakers are some nice Polks that are currently running on a mediocre Sony amp, but the tower speakers are crappy kenwoods that werent hooked up when I bought the boat. So, I'm just trying to make a little sound...not trying to blow everyone out of the water!

I've still got more investigation to do on the wire running, but so far I don't see a clean way to get the wire from the tower leg to beneath the observer seat without drilling a hole somewhere.

You can't do it wirelessly?:D C'mon! Look at what Tesla did with high voltage!

Is 3 Ohms DC resistance or is that the rating provided by the manufacturer? I have yet to see a speaker rated that way and if you measured 3 Ohms, they're 4 Ohm speakers (nominal). That Pyle amp, being MOS-FET, limits the current to the outputs if the impedance drops too low or it goes into thermal runaway and because most manufacturers buy goods made in China (meaning they come from a small number of factories), they're mostly the same with differences coming from sacrifices made because the name-brand wants to cut costs further. If you were to wire this amp with thin wire and bad connections, it would never develop anything close to the specified power and would cook your speakers before long and this applies to all amplifiers.

If you really want clean sound without having to worry about wiring configurations, use one channel per speaker, even if it's not 1.21 JigaWatts total. 50W/speaker going to 8 speakers will sound a lot better than 900W going to 8 speakers with extremely high or low impedance and clipping. If the speaker wire runs aren't more than 12'-15' and you're sending high pass signal (tower speakers don't need deep bass), you could use the same kind of 16ga 4 conductor wire used in home theater installations, rather than PVC insulated zip cord (this stuff doesn't do well with water and actually corrodes the bare copper wire) and the 16-4 has an outer jacket to protect the wires. You could run one cable up each side of the tower and it would only require a small hole and grommet. Use a waterproof connector- if your amp sees a dead short, it may be curtains for the amp.

dirtk38
04-27-2011, 12:06 PM
Rspiecha, always great to meet another Tiger. War Eagle!

Are you originally from Memphis? I was born and raised there, but I moved to Little Rock after graduating 3 years ago. What lake are you boating on?

rspiecha
04-27-2011, 03:13 PM
From all over the north, till the late 70's. Been here since, except the wonderfull 6 years at Auburn. Boating is done at Pickwick and the Tom Bigbee waterway. I graduate a little before you, 1991 :)

dirtk38
04-27-2011, 03:20 PM
Boating is done at Pickwick and the Tom Bigbee waterway.

Right on. I pretty much grew up on Pickwick lake. Parents still go there, and my family has a cruiser docked at the state park marina by the dam. It may not be as quiet or scenic as the lakes in Arkansas, but it feels like home and I try to get back there every chance I get!

Thrall
04-27-2011, 07:19 PM
Your avatars are confusing me!

What type of tower do you have on the boat? If possible, remove the tower (if needed) and drill a hole in the deck under the tower leg so the wires get into the boat "hidden".
Typically you'll have to have a plug or 2 somewhere to allow the tower to fold down, but personally I'd shy away from drilling visible holes unless thats the only way.

robin
04-27-2011, 08:42 PM
All that ohms talk and engineering talk gives me a head ache, but then again any math above 5+5 does.....im a police officer and semi-retarded when it comes to math. I will say if you are looking for a great 6 channel amp, id recommend the JL xd 600/6. Its very small, very stable, runs cool, uses little power and is versatile. JL is top notch. Dont skimp on your amp..its the heart of your system.

dirtk38
04-27-2011, 09:25 PM
What type of tower do you have on the boat? If possible, remove the tower (if needed) and drill a hole in the deck under the tower leg so the wires get into the boat "hidden".
Typically you'll have to have a plug or 2 somewhere to allow the tower to fold down, but personally I'd shy away from drilling visible holes unless thats the only way.

I had that thought too...I'm going to take a look and see if it's possible. I've got a Monster Tower.

JL is top notch. Dont skimp on your amp..its the heart of your system.

Love the small size of that amp. Normally I'd say the same on not skimping, but there wasn't a whole lot left in the budget after all the other stuff I've had to buy for the boat this year. If/when that Pyle blows, I may be taking another look at that JL.

Thrall
04-28-2011, 01:47 AM
Yeah with a Monster tower you won't be able to run hidden wires into the deck as you suspected becaue they mount solid with heim joints bolted through the deck. Take a look at the pictures on Monster's website. Looks like most of the speaker wires exit the rear leg(s) just above the deck and then go thru the deck in a visible location. The plug you looked at would probably work well for your application provided you really want to series/parallel 4 speakers into 1 pair. If you ever upgrade tower speakers this will not be an ideal setup, but you could parallel 4 spkrs into 2 and have a plug on each side of the boat.
Do the rear legs detach for folding? If not, just run your wires continuous out the tower and thru the deck with a rubber grommet in the deck hole, leave a little slack for folding.
If the rear legs detach then you could use a duetsch connector to unplug all the wires in the same location and minimize the size of the hole drilled in the deck.
Just some ideas.