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Old    Zach Lear (zleartsu)      Join Date: Mar 2004       03-09-2010, 10:02 AM Reply   
I getting a really good deal on a fiberglass box that holds 3 pairs of Polk 6.5 DB651. What would be the best way to power these guys?
Old    Brett Yates (polarbill)      Join Date: Jun 2003       03-09-2010, 10:20 AM Reply   
Here is a good option.

http://www.arcaudio.com/productdescr...ies/ks3004.asp

If you want something cheap you could check out Hifonics amps and get one that is 75x4 or so.
Old    Zach Lear (zleartsu)      Join Date: Mar 2004       03-09-2010, 1:10 PM Reply   
Yeah I guess I just not sure how to wire it correctly. I don;t want to short/blow the amp. So i quess my question should be how should I wire them?
Old    Earmark Marine (david_e_m)      Join Date: Jul 2008       03-09-2010, 2:37 PM Reply   
Zach,

1.) Run the left three in series for 12-ohms, the same for the right. Bridge a 4-channel amplifier into 2-channels. Use an amplifier that generates its full power into 4-ohms, so you're not losing much of its full rated power into what will be the load equivalent of 6-ohm stereo. An Alpine PDX will work here.

2.) Wire the left three in parallel for 1.33-ohms, the same for the right. Use an amplifier that is 1-ohm stereo stable like the Boston Acoustics GT-2200.

3.) Wire the left three in series, same with the right. Parallel the two sides for a collective 6-ohm mono load. Use the JL Audio HD 750/1 monoblock.

Obviously you can run a six channel amplifier with twelve conductors up the tower but the above three scenarios, and a few other options, will allow you to maintain a four-conductor tower harness.

While the speakers may be inexpensive, you have a combination (six tower speakers) that is expensive to power reliably.

David
Earmark Marine
Old    Brett Yates (polarbill)      Join Date: Jun 2003       03-09-2010, 2:59 PM Reply   
Quote:
Originally Posted by david_e_m View Post
Zach,

1.) Run the left three in series for 12-ohms, the same for the right. Bridge a 4-channel amplifier into 2-channels. Use an amplifier that generates its full power into 4-ohms, so you're not losing much of its full rated power into what will be the load equivalent of 6-ohm stereo. An Alpine PDX will work here.

2.) Wire the left three in parallel for 1.33-ohms, the same for the right. Use an amplifier that is 1-ohm stereo stable like the Boston Acoustics GT-2200.

3.) Wire the left three in series, same with the right. Parallel the two sides for a collective 6-ohm mono load. Use the JL Audio HD 750/1 monoblock.

Obviously you can run a six channel amplifier with twelve conductors up the tower but the above three scenarios, and a few other options, will allow you to maintain a four-conductor tower harness.


While the speakers may be inexpensive, you have a combination (six tower speakers) that is expensive to power reliably.

David
Earmark Marine

Dave, is it possible to run a 4 channel amp with 2 of the channels running 2 of the speakers at 2 ohms and then the other 2 channels running 4 of the speakers at 2 ohms?
Old    Earmark Marine (david_e_m)      Join Date: Jul 2008       03-09-2010, 3:56 PM Reply   
Brett,

Absolutely. Its just more difficult to set the gains equitably so I created scenarios where this wouldn't be a challenge.

For example, A JL G4500 4-channel amp which is well under $300.00, would exceed the 651s' power rating at every terminal. It would net after gain correction over 400 watts into the collective six speakers rated at 330 watts.

David
Earmark Marine
Old    Brett Yates (polarbill)      Join Date: Jun 2003       03-09-2010, 4:25 PM Reply   
OK, that is what I thought. Does it make a difference if the amp is one in which the 2 ohm output is exactly double of the 4 ohm output. In theory then you would be running the same wattage to all the speakers and could set the gains the same. I have no idea if it actually works this way and maybe you can tell if it does or not. Would it be less of a problem on in boat speakers if you had 2 speakers in the bow running 4 ohms and 4 speakers in the cockpit running 2 ohms?
Old    Earmark Marine (david_e_m)      Join Date: Jul 2008       03-09-2010, 7:19 PM Reply   
Brett,

Actually in this case the type of amplifier that produces a premium in power at 2-ohms would be advantageous. Since the 2-ohm channels would be split between two speakers per channel, this would come closer to balancing the per speaker output with the 4-ohm channels driving a single speaker per channel.

On the tower, speakers with identical output will sum more efficiently than dissimilar speakers so its a bit more critical. Where as in the boat, the cockpit occupants don't see a benefit from bow speakers on the opposite side of the windshield. Achieving a relatively equal balance between the bow and cockpit is not as critical and easier to do. I think you can imagine how balancing six speakers on the tower with four channels is a little tedious with all speakers playing near full output in a tight proximity.

David
Earmark Marine
Old    Zach Lear (zleartsu)      Join Date: Mar 2004       03-10-2010, 8:35 AM Reply   
Dave thanks for the great advice.
So if I went with the JL G4500. I should Run the left three in series for 12-ohms, the same for the right. Bridge a 4-channel amplifier into 2-channels. Use an amplifier that generates its full power into 4-ohms, so you're not losing much of its full rated power into what will be the load equivalent of 6-ohm stereo.

is this right?
Old    Earmark Marine (david_e_m)      Join Date: Jul 2008       03-10-2010, 11:42 AM Reply   
Zach,

Not exactly. The discussion with Brent had evolved into using a less expensive option where the JL Audio G4500 would operate in the four-channel mode and require an eight conductor tower harness. Once the gains are equalized this would still produce over 400 watts total of balanced power at 14 volts and still equal or exceed the speaker ratings at 12 volt power. But this is an unregulated amplifier and I'm afraid the power would fall off too much in a 12-ohm bridged application where you could utilize your existing four conductor tower harness.

I would stay within the guidelines of one of the above four examples.

David
Earmark Marine
Old    Zach Lear (zleartsu)      Join Date: Mar 2004       03-11-2010, 7:40 AM Reply   
David,
again I want to thank you for your help. Would this work in stead of the Polk PDX?
CLARION
APX490M Marine 4 Channel 720W Amp
190W x 4 CH at 2 ohm marine amplifier, Variable High/Low pass filters, Aluminum heat sink, Coated double sided circuit board

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