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  #21  
Old 02-28-2013, 10:02 PM
bsloop bsloop is offline
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Quote:
Originally Posted by EarmarkMarine View Post
Zach,
I would have zero problem with running a single HD1200/1 to drive two 12W6s in the air conditioned cabin of a vehicle knowing that the supply voltage will always be in the 13+ range. But keep in mind that an HD1200/1 is a major jump in power with the same heatsink mass as an HD750/1. And usually in marine things get run very hard and close to maximum with much lower supply voltage. So I like staying on the conservative side in this instance.

David
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Originally Posted by ZachDaddy View Post
But what if I do use a JL HD1200/1 what kind of negatives are there over 2 750/1's powering the subs?

My system for the summer is going to look like this:

Syn6 for the JL M770's - 2 pair

SD 4 for the pair of WS REV 410's

JL HD 750/1 or 1200/1 for 2 JL 12W6v2

I have a Pro Mariner 3 bank charger and a 2 bank Interstate series 27 deep cycle dedicated stereo batteries.

Do I have enough engine off stereo play time in the 2-3 hour range with my current setup?
David, pretty much answered your first question before you asked it. In the long play, hot marine environment, the amp will get hot faster. The way class D amps work, they dont thermal like A/B, they reduce power back to a stable level. That means, the 1200 could throttle back to half power or less. According to David, the heat sink is the same for both 750 and 1200 so eventhough 1200 might be able to put out more power at first, it can not get rid of heat any faster thus output will fall.

If $$$ are becomming an issue, stop paying so much for a name and full range power. Many other amps will perform as good or better for less money in you application.
For the same $1,000 or less, you are willing to spend on a JL1200.
You can get into an ARC KS series. the 2500 would blow a JL1200 out of the water! (and stay cool with a built in fan)
http://www.arcaudio.com/ks-amps.asp
Rockford Power 1500cp is a great option.
http://www.rockfordfosgate.com/produ...id=104&parid=2
I use 1500bd to power two 15" L7 with very satisfactory results.

As for a pair of 27 deep cycles playing for 2-3 hrs - I would say, yes, the system will play for 2-3 hrs at 80-90% volume but that will be all. It will stress those batteries to do it every weekend and big weekends, there will not be anything left when the party just gets going.
My rule is a minimum of one battery per amp. Look into a 4D or 8D Interstate if you really want to step up play time with minimal cost. A larger battery is more efficient than more of equal rating. The 3 bank will be fine charging; Start, 2 27 and Big.
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  #22  
Old 02-28-2013, 11:01 PM
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EarmarkMarine EarmarkMarine is offline
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Let's get a few facts right.
First, cutting back on the rail voltage to protect the amplifier has nothing to do with Class D operation. This is a common technique by many brands and many topologies. So that statement is totally out of context. It's just plain smart engineering. The pulse width modulated supply of a Class D or Class AB amplifier do not really differ. The difference is in the output section. Most contemporary PWM Power Supplies independently are over 90 percent efficient.

This amplifier will blow that amplifier away? Based on what? Unqualified paper specs?
Compare power at 4, 2 and 1-ohm.
Compare the JL Audio strictly regulated power at 12.5 volts to an unregulated amplifier....cause you certainly won't get 14.4 volts in a boat. That 2500 watt amplifier at 1-ohm at a 14.4 volt supply will produce 375 watts at 4-ohms at 12.5 volts where the JL Audio will deliver a minimum of 1200 watts at the same load and supply.
That internally (it has a shroud but no external sink) fan-cooled 2500 watt amplifier is not conformal coated. In a marine environment constantly running moist air over a raw and unprotected circuit board that is voltage charged may not be the best idea.

David
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  #23  
Old 03-01-2013, 12:46 PM
bsloop bsloop is offline
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Pulse Width Modulation PS are efficient an can play a longer time but sacrifice some output. How much? I have not seen much documentation or testing since it is scenario specfic but suffice it to say, coved party marine use will push it to throttle back more than most any other type of play.
Mfg give it cool names - JL calls it "Advanced Rollback Protection", Alpine PDX "Power Management" Alpine uses a graph and show the power reduction and spin it as a positive (again unknown how representative the change is)

I know mfg like the PWM PS since it pretty much dumbs down many speaker pairing and electrical questions but performance is sacrificed.
It is silly trying to use obscure cases like 4ohm with a sub amp. Many quality amps will have a "birth sheet" proving their power. Example is this T1500bdCP. At a perfect 14.4 is putting out 1910w RMS @ 1ohm and 1165 @ 4ohm. Roll power back to 12.5 and amp is still delivering 1500w.

This advice is going to the OP and his established set up of two 12w6 which are dvc 4ohm which yeilds a 1 ohm load.
I feel very confident that with the OP setup, using modern music formats - 10 audio knowledgeable people sitting on the water listening to 3 amps - JL 1200, RF T1500bdCP, ARC 2500 - JL will get the least votes by 8 out of 10 people on loudness and music impression. I have not heard the ARC 1500 but feel pretty confident in throwing that into the mix too.
OP still has money left with any of those 3 to buy more batteries that will allow the system to play longer and louder than if he had spent $1k on just a JL1200. Heck with SonicElectronix (I feel a little dirty referencing them) having the 1500bdCP at $500, OP has enough for amp, D8 battery and a full tank of gas.
JL is a great product and will sound great if a person has the coin to throw at it but others can sound better in THIS environement with excellent reliability and sound quality for less.
Right now, OP is feeling the $$ pinch and looking to cut corners. Trying to give him safe, quality, viable options.

I am not initimate with the ARC KS internals but it is my understanding they are very similiar to WS Syn line that has been around for 5 years and has a good fan base. OP thought enough to use for his JL in-boat speakers.
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  #24  
Old 03-01-2013, 02:48 PM
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EarmarkMarine EarmarkMarine is offline
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bsloop,
You have a PWM power supply confused with a pulse width modulated analog switching amplifier (Class D). Two completely different things with zero in common. The thermal management described has to do with power supplies and nothing to do with output topologies.
Amplifiers are rated at 14.4 volts but you can't get 14.4 volts in a boat. It's like rating your car's horsepower with jet fuel. It's impressive but you can't get it at the pump.

David
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  #25  
Old 03-01-2013, 03:04 PM
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EarmarkMarine EarmarkMarine is offline
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Btw, the birth certificate doesn't even specify what the frequency is. Will the amplifier produce that at 12 volts at 50 Hz? No way to tell cause the number is unqualified in several aspects. CEA-2006 only requires 1kHz.
You can bank on the fact that the JL Audio amplifier will exceed its specs at the low end of the bandwidth at any safe voltage you are going to have....real world.
PasMag recently did a review on a JL Audio inexpensive unregulated amplifier. The CEA-2006 power as tested was 35% more than rated, from an independent source! Plus, the 12.6 volt power at 4-ohms as tested equaled the 14.4 volt JL Audio rating.
So let's not compare ratings out of context because you have not seen the JL Audio birth certificate.
Also, while Wetsounds use a common platform, the difference is that the Wetsounds internally fan-cooled amplifier IS conformal coated is consideration of moist air driven through the inside of the amplifier.

David
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  #26  
Old 03-16-2013, 04:29 PM
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ZachDaddy ZachDaddy is offline
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Boat: MasterCraft, X15, 2007, MCX, Acme 5 Blade, Pair of WetSounds Rev410's, WetSounds SD6, 2 JL 12w6v2 subs in sealed box, JL HD750/1, WS402SQ
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David...I got my subs and the box installed today and I am not that impressed. Shocked I know, right.
I know I will have to allow for the break in period since both of the subs are factory new but the single 750/1 is not at all what I was hoping for.

I think my ear is ruined because of my ported 8w7 in my vehicle. Now that thing BOOM's
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  #27  
Old 03-16-2013, 09:45 PM
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EarmarkMarine EarmarkMarine is offline
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Quote:
Originally Posted by ZachDaddy View Post
David...I got my subs and the box installed today and I am not that impressed. Shocked I know, right.
I know I will have to allow for the break in period since both of the subs are factory new but the single 750/1 is not at all what I was hoping for.

I think my ear is ruined because of my ported 8w7 in my vehicle. Now that thing BOOM's
Zach,
You definitely have the right product.
There could be a number of execution reasons for the woofers not living up to their potential.
A 12W6 really likes an HD750/1 per woofer. Before adding another amplifier, first make sure that everything else is right.
The peak of a 12" downfiring sub outer surround should be elevated 3.125" off the sole at minimum. Otherwise you are creating a reduction in radiating surface area which creates a reduction in output.
Optimumly, woofers should be direct radiating.
Whatever compartment/locker the subs are mounted in should ideally be vented with an open surface area equal to that of the collective woofers which is about 156 sq.in. for dual 12"s.
Otherwise the air mass of the expansive compartment/locker plus the adjoining gunnel cavities equates to a huge compliance. Combine this with no vent or a small vent which equates to significant resistance and there is little impetus for the bass radiation to flow from the compartment.
That is an incredible amount of pressure from dual 12"s. We usually fully encapsulate the terminal cups for a double seal so there is no air escaping.
In an open field environment you select the crossover frequency & slope plus tune the sub very differently than you would in a vehicle's enclosed cabin.
Pass these comments onto your installer if he doesn't mind the input.
His work looks good so he appears capable.

David
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