Advice on stereo mod

[Craig]

Ok, first off let me apologize as I'm not a stereo guru, hence the question. Additionally I'm not looking to create a "blow your mind" type stereo system in our boat. And yes, I know that the polk db651's are not comparable with wetsounds and other high end brands. The polks are however friendlier to my wallet.

That being said, I'm planning on definitely adding two more polk db651's to my cockpit area (near the captains and co-captains seating), and would like to add two more to the swim deck area for times when we're swimming and hanging out. This would total 8 polks @ 60 watts rms. I know I would need an amp to push all 8 speakers and have been looking at the MB Quart NA540.6 which is 540 watts rms. Anybody have experiences with this brand of amps? I've not overly familiar with the brand and it seems to have decent reviews? If I understand it correctly, I can wire all 8 polks through this amp by wiring some of the speakers in parallel? Are there any issues this would cause by doing this? The alternative (which I would probably rather do anyway) is to find some way of being able to switch power from the bow speakers to the swim deck speakers. Is there an affordable way to do this?

Will running an amp help prevent the distortion I currently hear in the polk db651's while pushing it at higher volumes with my head unit (clarion cmd7 @45 wattsx4)? Is this distortion the result of the head unit being underpowered?

My last question is this, would I need to install a second battery to run the amp above? Currently we have one battery, but honestly we don't sit a tremendous amount and run the stereo. As a rule our boys keep us running with one watersport or another.

Below are the specs for the amp and speakers:
MB Quart NA 540.6
RMS Power @ 4 ohms 60 watts x 6 channels
RMS Power @ 2 ohms 90 watts x 6 channels
Bridged RMS Power 180 watts x 3 channels
Amplifier Specifications
Marine Certified -Yes
Amplifier Class-SQ
Number of Channels-6
Total RMS Power Output-540 watts
Maximum Input Gauge Size-4 AWG
Minimum Impedance Unbridged-2 ohms
Minimum Impedance Bridged-4 ohms
THD at Rated RMS Power-0.05%
Speaker Level Inputs-No
Preamp Outputs-1 pair
Built-in Crossover-Low-pass (LP),High-pass (HP)-
High-Pass Crossover Frequency 250 - 4000 Hz
Low-Pass Crossover Frequency-40 - 250 Hz
Signal-to-Noise Ratio-93 dB
Channel Separation-80 dB
Bass Boost-0 - 9 dB
Bass/Gain Remote-No
Fan Cooled-No
Fuse Rating-70A x 1
CEA-2006 Compliant-No

Polk DB651 6.5
Tweeter
Quantity1
Diameter3/4" (1.91cm)
TypeSilk/polymer composite dome
Mid / Woofer
Quantity1
Diameter6 1/2" (16.51cm)
TypeDynamic Balance driver with polymer/mica composite cone with rubber surround
Electrical
Total Frequency Response35Hz-22kHz
Nominal Impedance4 ohms
Efficiency92 dB
Power Handling
Continuous60 watts
Peak180 watts

I apologize again for my lack of knowledge in the stereo realm, but honestly it's something I've never really messed with. Any advice or feedback is greatly appreciated. Again, I'm not looking for a mind numbing stereo system, just a decent one I can hear underway with respectable sound/volume at a price point that won't break the bank. Oh, the sub will have to wait a later date. Thanks

 

[Master-Spud]

Well by no means do I know what I'm doing, but here is my plan for my 212x as of right now.

Currently have 6x Polk Audio DB651's (4 cabin, 2 swim platform) all running off the head unit.


What I plan is:

Replace swim platform speakers with something better, move replaced swim platform speakers into 2 new holes mid cabin. I think this will give me enough sound in the cabin and if I'm not happy with the performance I will then replace all cabin speakers with something better. The upgraded swim platform speakers will give the boost on shore as well as not having to replace them twice if I decide I don't like the performance of the DB651's after amplification. Seeing as you can't really hear the swim platform in the boat I don't think the mismatach will hurt too much.

I think I will be getting JL audio 8ch marine amp, gives me 100 watts per channel into 2 ohm, this will give me some breathing room if I decide to upgrade to speakers that need a little more juice.
http://www.jlaudio.ca/m800-8v2-marine-audio-m-series-amplifiers-98359

I will add tower speakers and a sub (still up in the area as to which ones.)

These will be run off another amp, again unsure what I will need for power until I decide on the units.

Will then have independent volume knobs for each amp, and hopefully a bass one as well (think that should work) This will allow me to adjust tower and cabin as well as the bass all independently.

Will also add at least one battery if not 2. Don't want to depend on one and kill it and be dead in the water. I would be very hesitant to not have a 2nd battery when doing any kind of stereo upgrade. Bare min get a booster pack!

Not sure if this helps at all and obviously a little different budget, but always seems to help to have a few different ideas floating around to build off of.

 

[Master-Spud]

Guess I should of answered some of your questions too lol

Running 6 speakers off the one amp shouldn't be an issue as long as there is enough power there. (they are already doing that on my boat with 6 speakers being run off the head unit which is 4x15watt)

The distortion at higher volumes I would almost say for sure is because they are currently underpowered.

And see above for thoughts on battery

 

[txav8r]

One thing I have learned after two stereo mods in the boats now, is that an 800w/8 channel receiver is really 60w per channel at 12.5v. The 800w rating is at 14.4v which we will never see in our boats. Our electrical systems will return around 13.3v at cruise and 12.5v at rest.

Most assuredly, you have more clipping and distortion when underpowered off a less than clean HU signal than when a clean amplified signal is present. I know many want to state that some HU's have Class D amplification at some level equivalent to some of these amps on the market. Don't believe it. For instance, my tiny little Fusion IP700i is stated to have Class D amplification over 50W RMS as well. I ask you this...why do quality amplifiers that are the size of the entire HU or larger, require the use of 4GA cable from the power source...and the HU's are typically connected to a power source with 16GA or less? It is because they do not make the kind of power that a dedicated Class D amp makes, so they don't require the GA wiring that the amps do. I am not sure what is hype and what is fact in audio advertising, so I depend on the experts to help lead me where I am trying to go.

You can certainly get better sound by powering the polks and the polks will be a great deal better than previous stock speakers or even the polks unpowered. And a mild amplification, you could certainly run the 8 speakers. But if your running 8 speakers with 4 zones, you will need about 400w of power at least, and while that won't break the battery bank, it will lean on it. While underway, you will crank your stereo much more than while at rest, more than likely, and offsetting that use with the charging system will help with that. But, you can only put back about 10amps per hour on a battery, regardless of how big the charging system is. So it is all dependent on how many amps your using from the battery as to how many batteries you actually need. Batteries not only provide capacity at anchor, but they help to buffer your use while running as well. With any modified stereo, IMO, it would be a good idea to have a second battery...again, that is only my opinion on it, but I can support that opinion as well.

 

[Master-Spud]

You sir are right about the 8 ch at 12.5V, right of JL's site if I dug a little deeper. Still enough power in my books for the speakers, but not as much as 100watts that's for sure.

Rated Continuous (RMS) Power @ 12.5 V
@ 4 Ω60 W RMS x 8
@ 2 Ω90 W RMS x 8
Bridged @ 4Ω180 W RMS x 4

 

[txav8r]

But also keep in mind, that JL amps are
Underrated, and pretty heavily underrated! Other manufacturers test optimum and claim that, JL tests and
Bases it's numbers off the lowest denominator. So you know your going to get more than stated with a JL amp.

 

[Craig]

So basically, if we're going to run a decent size amp the electrical system on our boats can't keep up with the draw from a moderately powered system?

 

[txav8r]

Sure it can...but being creative helps. Some guys will run more than one standard group 24 battery, others will run an ACR with switch and dual batteries, and still others will run dual and triple bank batteries manually. Some just use a jump pack for insurance. Moderate system is where the debate begins and how you actually use the boat is another one. While running a moderate, 700w 5 channel amp on my previous boat, David, formerly of Earmark figured I would be using 530W out of the 700, but in actuality, your also not running the transom speakers while running, just the interior speakers, so you only use about 480 divided by 13v equals a 37amp draw, assuming 30% average is only 13 to 14 amps at full volume. Your replenishing 26amp per hour too, which runs all boat systems but still can recovery and support of the running stereo. So your not just draining it, and with an ACR, your charging system will keep both batteries in the charging loop. Again, many will debate this but this works well in a moderate system. I actually have used the ACR effectively in two setups now. And...I also run two batteries, and they are group 27's so I will have plenty of reserve and capability both running and anchored. The ACR will isolate them when not running, but when charging, combined. On the new boat, I moved up a little. Instead of 6 coaxials and one sub, I have 8 coaxials and one sub, so I had to move from the 700/5, to 2 separate amps. I now have the 600/6 and the 500/3, but again, I am only using 60w for each of the 8 coaxials, and 180w for the sub...or a total of 660w. Lots of headroom, and very efficient, and I probably get the performance of a much larger amplifier setup. If I can only get the time to finish this second install!

But in actuality, it is possible to drain a single battery faster than you can keep it charged. So that is why a second battery is a good buffer for that.

 

[mgabsa]

@txav8r i just read your last post and you blew my mind, LOL. Do you wire any speakers in parallel? From what I have researched, this is a common way to get more from your amp. Im pretty sure the rear cabin and transom speakers are wired in parallel on my boat.

I added a 10" 4 ohm sub and I have a 5 channel Kicker amp, 4 channels+a sub channel, and I was highly disappointed in the result after I installed it. The points you made on your last post helped me understand why I'm disappointed. My boat has the 2 battery configuration already.

I am back to the drawing board on what I am going to do this winter to finalize my stereo.

 

[redthumper9]

@Craig .....simple answer.....the MB Quart amps are decent amplifiers. I have owned two, and although I have moved on to class D, the MB Quart amps will work for a mild to moderate system. If you are going to run 8 speakers, just parallel the transom and rear speakers together to two channels, and the cabin/bow speakers to the other two channels. You should plan on a second battery or jump pack even without a stereo mod simply for the insurance. I kept my battery configuration simple. I have a simple Perko switch. Put it on battery 1 to use that battery. If it gets weak, switch to battery 2. I personally don't do enough riding on most days to benefit from an ACR. This is how I have run for about 4 years now and it seems to work great for my application. Bottom line......plan on an extra battery.....the MB Quart amps are class A/B amp, so they will draw more current than a decent class D.