Axis Wakeboard Boat Forum

I have a 2011 A22 with the MTX amps and speakers. One of the amps got wet and went out so I got a Rockville RXM-F3 1600 Watt Marine/Boat 4 Channel Amplifier from a buddy and also installed a new sony receiver (mex-m72bt) as the volume went out on the Sony stock radio. I am pretty clueless as far a audio goes so a buddy hooked up the new amp, but I have no sound to the tower speakers and the sub is very quiet. It looked like there were some Rca splitters but not used now as he said the new sony has three outputs instead of two on the stock unit. The power light is on the new sub.

This is how it is hooked up now.

Sony (mex-m72bt )receiver has 3 outputs left right and sub. The RCA cables from left and right output go to the MTX Amp and power the boat speakers. The sub RCA cables go to the new amp channel 1 and 2 and the speaker wire is bridged ( i think that is what it called ) to positive on 1 and negative on 2. The 4 tower speakers are on channel 3 and 4. I am assuming the tower speakers are tied together somewhere since there are only 2 sets of speaker wires coming to amp.

Questions
1. What should power the Tower Speakers since there is no RCA coming into channel 3 and 4?
2. I would like to have it set so the tower speakers can be faded to have sound coming from tower only
or boat speakers only but also have all on at once as well.
3. I have a mulitimeter but have no idea what setting or how to test for signal.
4. What should the x-over switches be set to on the back?


thanks for your help

looking at the manual for the head unit, you should have 3 sets of RCAs. 1) Front (right/left) 2) Rear (right/left) and 3)Sub (right/left).

There are a couple ways you can make this work. But here is what i would do...
Front (R/L) RCA from head unit to the MTX to power the boat speakers.
Rear (R/L) RCA to the new amp Ch 1/2 to power the tower speakers.
Sub (R/L) RCA to new amp Ch 3/4 to power the sub

New amp settings:
Freq Multiplier button OUT (x1)
Ch 1/2 switch to HPF
Ch 1/2 Filter - 9 o'clock position (roughly 80-100 hz cutoff)
Ch 1/2 input level - 1/4 sweep range (to start)
Input mode - 4 ch
Ch 3/4 Crossover - LPF
Ch 3/4 input level - 1/4 sweep range (to start)
Ch 3/4 Bass Equalizer - mid range
Ch 3/4 High Pass filter - full counter clockwise (15hz)
Ch 3/4 Low Pass filter - 9 o'clock position (roughly 80-100 hz cutoff)

Tower speakers are wired together inside the tower. Use the wires you have to connect them to the Ch 1/2 outputs on the amp. Your sub needs to be bridged (like you did...Ch3 +/Ch4 -)

The only way you can control the cabin speakers and tower speakers seperately (without adding another device) would be to use the FADE function on the stereo to fade the sound all more to the rear only (if you are trying to turn down boat speakers). Otherwise, you would have to add an RCA Gain Level Controller (PAC LC1) inline with the RCA cables feeding the MTX amp. Also, if you are using connecting the tower and sub to the same amp, if you do turn down the boat speakers, the sub will still be at the same level as the tower speakers are playing. If you want the sub to be able to be turned down with the boat speakers, you need to flip/flop the speakers (MTX powers the tower, Rockville powers boat/sub).

Additionally, you can set the Filter functions on the amps to FULL and use the filter settings of the head unit. Im certain there are numerous settings in there that will do the same job. You will need to play with the input level settings on both amps to get the right balance of volume. Set your radio volume level to roughly 3/4 full blast. Adjust your amp inputs to the max desired listening volume....then add a tad more. Be sure you scroll through the settings in your radio. Im going to assume it has settings for high and low pass filters. This would allow you to set the filter/crossover on the amp to FULL and just adjust everything from the radio. General rule for filters i use....high pass (boat/tower speakers) no lower than 80hz. Low pass (sub) no higher than 100hz. There is also likely a setting to turn up the output gain for the sub as well as an on/off setting.