Wetsounds Tower Speaker Amplifier Gain Control Setting (diagram included)

[brettskiT23]

New to Malibu Crew and just picked up a 2015 Axis T23 after about 4 years of researching.  This site has been an invaluable tool in helping me to make informed decisions and be a educated buyer, so thank you to all who post on this site.

So I have spent the last few weeks going through every single system and familiarizing myself with every piece of the boat and troubleshooting/replacing a few items that needed.  As soon as we took the boat out we noticed the 4 tower speakers were going into protection mode and cutting out when we turned the volume up about 25%.  Our head unit is a Sony CDX-H910UI with a volume control of 0-50... we were around level 20.  After doing extensive research here and elsewhere it seemed that the gain control was the issue.  Last night I got things adjusted to where everything seems to be in order.  My question to this forum is whether or not this is the correct remedy.  I have drawn a diagram of how I believe my system is wired that can be found here.  Full disclosure, i'm an architect, not an electrical engineer, but I did stay at a Holiday Inn Express last night.  Punch line of the story is that my 4 tower speakers  (Icon 8's @150RMS @ 4ohms) are running off of one amp (either a wetsounds HT1 or HT2, admittedly I didn't check).  I set all the EQ's to flat and turned the volume up to 75% (number 38 on head unit) and played a 1khz test tone at 0db gain to take my voltage readings coming out of the amp.  The initial reading came in at 30.52V out of the amplifier which using the formula SQRT(150 watts * 4ohms) = approx 24.49V seemed to be a little over powered.  However as best I can tell the speakers are wired in parallel off of a single channel which would reduce impedance to 2ohms (2-4ohm speakers) which would mean a max voltage of SQRT(150 watts * 2ohms) = 17.32V... which is far lower than what it was set at, and is almost at minimum gain.  Initally I set the gain to 17.32V and was still experiencing the same problem, and after completing the definition of insanity 6 more times, it worked fine, however the last time I believe that I inadvertently switched the left and right of the single channel (still connected + to + and - to -)... which could have affected all the wiring down the line (maybe they aren't in parallel).

Bottom line, I am unsure of whether the voltage that I have set the tower speakers at is too low (which is better than too high).  I have not found a definitive answer on whether you combine the wattages of speakers connected in parallel or just use the rated RMS wattage of a single speaker and the measured impedance to set your base tuning.   My impedance measurements of the speakers are a nominal of 2 ohms and an actual reading of 2.9ohms (both left and right pair).  Any help would be appreciated, otherwise I may just have it checked out to be on the safe side. 

Side note:  Does anyone else have a boat where the radio memory (yellow) wire is not wired directly to the battery?  When i cut my battery switch off it kills memory power to the head unit which is completely pointless... I ended up running a new 3A fused wire to the radio last night (probably need to change to a 1A but 3A was all I had on hand).

[MLA]

Id say 75% of boats have the yellow B+ wired to the boat side of the main switch. Not many people use tuner or the clock on the radio, so no real need for memory retention. 

Is the 2 chnl amp in there, not the mono

With two 4 ohm wired in parallel, you would want to use 2 ohm in your formula, not 4 ohm. The cumulative RMS p/chnl would the speaker's rms x 2. 

[brettskiT23]

Thanks for the reply.  I'm pretty sure it is the HT-2 amp.  Like you said two 4ohm in parallel would yield 2ohm which is what I based everything off of.  Weird thing is I have a friend who is the parts manager at the local malibu dealer and he said they are usually wired in series, so now nothing really makes sense.  Even though it is working now I'm thinking it may just be best to take it in for a diagnostic just to be sure everything is in good shape.  Regarding the yellow wire I just think that is a little strange... we are a Pandora only household so I snagged my Fusion BT bluetooth adapter and wired it in to this boat first thing but my OCD just can't handle the clock and settings constantly getting reset... as stupid as it sounds we also have a 5 month old and we need to keep an eye on the clock from time to time.  Good news is since this boat has a bimini (we came from a 1986 no-name I/O) the kids can nap while we continue to play.

[23LSVOwner]

1 hour ago, brettskiT23 said:

Thanks for the reply.  I'm pretty sure it is the HT-2 amp.  Like you said two 4ohm in parallel would yield 2ohm which is what I based everything off of.  Weird thing is I have a friend who is the parts manager at the local malibu dealer and he said they are usually wired in series, so now nothing really makes sense.  Even though it is working now I'm thinking it may just be best to take it in for a diagnostic just to be sure everything is in good shape.  Regarding the yellow wire I just think that is a little strange... we are a Pandora only household so I snagged my Fusion BT bluetooth adapter and wired it in to this boat first thing but my OCD just can't handle the clock and settings constantly getting reset... as stupid as it sounds we also have a 5 month old and we need to keep an eye on the clock from time to time.  Good news is since this boat has a bimini (we came from a 1986 no-name I/O) the kids can nap while we continue to play.

He doesn't know what he is talking about. Each channel is wired in parallel with 2 tower speakers on that side (4 total overall) which gives a 2 ohm load to that channel.

Edited August 22, 2019 by 23LSVOwner

[MLA]

1 hour ago, brettskiT23 said:

Weird thing is I have a friend who is the parts manager at the local malibu dealer and he said they are usually wired in series, so now nothing really makes sense.

Ive never come across a Malibu or Axis 4 tower pod setup wired in series. However, you have a meter that youve been measuring amp output voltage, no need to wonder or speculate. Measure the impedance of each pair of wires at the amp chnls.  

[David]

Brett,

Your formula of [Wattage = AC Voltage squared / divided by Impedance] is correct. If the power is already a known value (150 wpc @ 2-ohms) then you can use this method (17.32V) to set the maximum gain with the speakers disconnected.  So everything looks good. The 2.9-ohm reading you're getting is the DC resistance, since you are unable to read the actual AC impedance, which is only a nominal rating since the AC impedance varies with frequency. The DCR is the net result of the two speakers in parallel plus any series wire resistance. That (2.9-ohms) seems a bit high, which would have me wondering what just the wire + connections resistance is without the paralleled speakers. If you get a different DCR reading for left and right sides, then I would measure all the speakers independently for uniformity. Btw, are you running the HT2 in the high-pass mode? Eventually, if the HT2 is found to be in good working order, I would do this: Convert the HT6 to each channel driving a single in-boat speaker. Move the HT2 to drive the 4-ohm subwoofer in the bridged mode. Get a new amplifier, one with a bit more heft, to drive the tower. The idea of the changes aren't necessarily to add more power, but rather to operate the amplifiers more conservatively with less thermal stress. The change wouldn't lighten the load on the HT2, but would provide more headroom everywhere else. Another upgrade option: Replace the HT2, dedicate the HT6 to the 6 in-boats, add an upgrade Wetsounds series in a 4-channel (larger power supply, larger heatsinks) that would drive both the tower speakers and subwoofer.      

Edited August 22, 2019 by David

[Wilbur]

Here is the correct and easy way to set your amp gains