Worth upgrading to class D amps because of overheating issues?

[Dev]

Lately i've been kicking around the idea of upgrading my amps to Class D to alleviate the overheating issues i've been having. As the only source of music in my group, it can be pretty frustrating when they decide to shut down. Those of you who have made the swap - have you seen enough of a difference to justify spending the 1200$?

Current setup:

4XM9 powered by Harpoon
4 cabin speakers and a sub powered by Kicker 700.5

I'm looking at buying an Exile Javelin and Exile 30.2 amp. I like the idea of this setup because it leaves me room to grow into 6 new cabin speakers when the time is right.

Side note-currently the amps are mounted horizontally(doh) so I suspect some of the heat issues could be from the heat not dissipating properly. This will be changed regardless of whether or not I upgrade.

[MLA]

Honestly, i dont think your thermal issues are related to those two amps being class-A/B. If both amps, with their perspective loads, are going into protect mode, its like supply voltage or insufficient cable gauge.

[Dev]

Hey MLA - thanks for the reply.

A majority of the time it is only the harpoon going into protect (which happens to be situated above the Kicker). Do you think I would see a significant change in temperature once my current amps are moved to a side-by side vertical orientation?

I have 2 gauge going to the distro and 4 to the amps. Seems to happen regardless of timing or charge so I don't believe it's voltage related.

[MLA]

Does the amp need to sit off in order to return to service or does it return to service by turning down the volume? Thermal shut down, the amp need to cool a few minutes and will return to service. Other reasons for protect mode, the amp will come right back on as soon as the cause is gone. If its primarily one amp, then it could be a speaker with a low impedance or even the amps tuning. If its happening while the engine is running, that would likely eliminate a low voltage issue, but knowing what the actual voltage is at the suspect amp, when the problem occurs, would be nice.

[Dev]

The amp needs to sit for a bit to cool off before it turns back on.. It gets to a point where you can't even touch it without burning yourself. I haven't brought a multi out on the boat with me so I don't have actual voltage numbers to share, but it does happen on longer drives while the engine is running.

Each side of the tower is wired in parallel for a 2 ohm load per channel and tuned somewhat conservatively.

[Dev]

Fyi this is in the Arizona heat, where the ambient temperature at the lake can be 105+

[David Analog]

It is particularly tough on the top amp when two amplifiers are mounted horizontally and the two amplifiers are very close to one another. An amp panel tilted back at a large angle will help minimize some of this.
Several things you can do.
Re-mount the amplifiers side-by-side vertically. Place both amplifier power supplies (the end that the power wires enter) at the top.
Stand the amplifiers off the mounting surface by 1/2 inch.
Fan cool the amplifiers. A cover shroud multiplies the fan's effectiveness many times.
Separately vent and fan cool the amp compartment.
Battery voltage that does not dip below 11.8 volts when at rest.
A correctly tuned system.

As for the change to Class D. Just about every manufacturer made that change at least 5 or more years ago.
Of a 1000 watts draw a Class AB amplifier generates 500 watts in heat which must be dissipated. A Class D amplifier generates 200 watts in heat with the same draw. So a huge difference in the supply demand, efficiency and heat generation. Since Class D is only a fraction of the heat, usually the heatsinks are only 1/4th the mass which still places a limit on thermal dissipation. So if you do change over, make sure you have corrected any inherent flaw in the system execution, whether design, installation or tuning.

[Dev]

In all of this I never considered the smaller footprint would have a much smaller heatsink than my current amps. Thanks for the insight David.

My amps are mounted 1/2 in off the board with large squares cut out of the mdf behind them. I think I will change their orientation and look into installing a few fans in the compartment. Hopefully this will make enough of a difference to be satisfied for another season or two. I may add another battery as well.

Does anyone have fan recommendations?

[David Analog]

Earmark Marine sells a variety of fans so you might get with Odin. He can also get you fixed up with a relay and the wiring instructions plus any instructions on a shroud.
Again, the key to cooling fan effectiveness is the shroud. Without a shroud the fan is working to rotate air 'around' the fan instead of an exchange of air across the entire amplifier heatsink surface area.
Possibly the coolest air is in the bilge since the water temperature is always lower than the air. It would be easy to place a secondary fan and vent to funnel air through the bilge.
Measure your voltage precisely at the end of the stay at rest and before you start the engine again. That measurement will be revealing. Too much battery capacity, and too much diminished reserves, will impede your alternator's ability to restore the charge. And that can translate to a greater dependency on AC shore power charging.

[MLA]

The more this thread progressed, the more is does sound like thermal shut down of the tower amp. I do find it odd though. As large as that amp is in respect to its power output, I think it should be able able to handle that 2 ohm p/chnl load just fine, providing everything else is good. So if the gain, cross-over filter and frequency are within reason, and battery voltage is steady (should be with engine on), then look into changing the amp arrangement.

Im a huge fan of class-D amps, so by no means amd i trying to talk you out of upgrading. In most cases, heat is down on the list of reasons. Im one that like to isolate a root cause and fix stuff first. I hate talking the shotgun repair approach, you know, replace everything hit by a pellet. :p I would certainly take the advice laid out by David.