Rockville 8 Channel Amp Question

[RadioJet]

Hi all. Looking for a little help expanding my sound system. I’ve got a Rockville RXM8BTW 8 channel amp with a Garmin RA60 head unit in my 2007 SX230. Here is the current setup:

Inputs
Channel 1 & 3: White RCA from head unit
Channel 2 & 4: Red RCA from head unit

Outputs:
Channel 1 & 2: L & R Aft coax speakers
Channel 3 & 4: L & R Mid cabin coax speakers

Current setup is working correctly. I would like to add 2 additional coax speakers on swim platform, and 1 powered subwoofer (Rockville 10”). There is a single “Subwoofer Out” RCA cable available from head unit.

I’ve seen a couple other posts referring to this amp, but they used different head units with more than one set of RCA outputs, so I can’t quite sort out how to make this work. Can anybody tell me how inputs and outputs for additional speakers should be wired, along with setting selections on amp?

Thanks!

 

[scokill]

I had the RA60 and had to move to RA670 in your similar situation. RA60 is a 2 zone plus sub system but zone 2 is only speakers from the onboard amp, so you have one set of RCAs from Zone 1 to use a Y cable to split in to multiple channels of your amp, and you lose the independent zone control and really can only control L/R. Not ideal. The way the amp is setup for the inputs is not ideal either, but can be done. The RA670 is 3 separate zones all with RCA outs and a sub out. Very flexible and allows you to make one zone louder, shut off a zone, independently control sub, L/R etc. etc.

Set input mode to 8 channels. Depending on how you want to control the speakers from L/R zone one balance it would be something like Zone 1 L with a Y Splitter to channel 1/3 input on amp, Zone 1 R with a Y Splitter to channel 5/7 input on amp. You would need to a splitter on one of them for input on channel 6/8, or potentially use the pass through ouput jacks to feed 6/8. You would send the single sub RCA output from RA60 to channel 2/4 input.

In this scenario Zone 2 would be useless because no speakers would be hooked up to Zone 2 from the RA60 internal amplifier. Wiring the speakers for channels 1/3, 5/7, 6/8 would be up to you on the control you think best for L/R. Your Sub would wired bridged on channels 2/4. You would take your positive wire from sub in put in + terminal of channel 2, and negative wire from sub in - terminal of channel 4. This will give you 190W to the sub. Typically the bridging wiring would be marked on the amp, but in the manual it says any 2 channels on the amp can be bridged.

Here is the challenge. Your gain, low pass/high pass filter settings are for channels 1-4, and then for channels 5-8. If you had all boat speakers then no problem. But you have the sub. Good news is you have sub level and sub filter frequency built in to the Fusion RA60 in general settings. You will just need to have a happy medium for the gain for both the boat speakers hooked up and the sub knowing you can adjust the output on the head unit.

There are likely other ways to split the signal to the amp and wire the speakers, but at least this gives you the sub channel control and more power to a sub. Ideally you would have 3 sets of RCAs plus mono sub out, and have independent channel control on the amp for each.

 

[RadioJet]

Thanks for the quick and thorough response! I’ve also put one pair in the bow area wired to zone 2 speaker outputs on head unit, so that at least gives me some fade control. What about connecting 4 of the speakers to 2 channels in parallel? That would then leave room for the sub

 

[scokill]

Thanks for the quick and thorough response! I’ve also put one pair in the bow area wired to zone 2 speaker outputs on head unit, so that at least gives me some fade control. What about connecting 4 of the speakers to 2 channels in parallel? That would then leave room for the sub

So you will have 8 speakers and a sub? 2 powered by the head unit, and 6 by the Rockwell’s amp, and 1 sub? Or 6 total speakers and sub? The head unit is 22w, not really enough to power a quality speaker but if you have 8 total it would be OK. You have room for the sun regardless and can power it reasonably well with 2 channels bridged. I don’t see the value of wiring parallel in your setup . What are your speakers impedance and rms specs?

 

[RadioJet]

Currently 6 factory 6.5” - 2 in bow area on head unit, 4 in cockpit on amp. Planning to add 2 Polk Audio DB402 DB+ Series 4" Coaxial Speakers with Marine Certification. Spec sheet says
135 Watts Max Each, 45 Watts RMS Each
• 4 Ohms Impedance
• Sensitivity: 90dB
I using splitters on RCA cables for inputs as recommended, and intend to bridge the sub. Seems like if I bridge the sub, I’m missing either left or right channel output for the 4” Polks, so thought I might have to parallel to fit them in. This 8 channel amp is very new to me and is making my brain explode!

 

[scokill]

Ahhh…..I see. So you have 4 on the amp adding 2 more. That will fill 6 channels. You will have 2 channels free. Those will be the Channels bridged for sub. If you want L/R separation it will require some thought based on the way the inputs are shared

 

[RadioJet]

That’s my concern, how to have L/R separation. Also, with this setup, I wouldn’t use the sub output from the head unit, correct?

 

[scokill]

That’s my concern, how to have L/R separation. Also, with this setup, I wouldn’t use the sub output from the head unit, correct?

Yes. The sub output is ideal for your potential setup. The frequency filter is done by the head unit and you really need 2 channels bridged to give decent power to sub.

 

[RadioJet]

Hello again. Been a while but finally got around to solving this problem by going the route you did - never had any luck bringing the sub online, so bought a Fusion RA-670 to replace the RA60. You gave great wiring notes for the RA60, can you suggest best wiring solution for new configuration?:

RA-670 Head
RXM8BTW Amp

2 coax speakers in swim step area
4 coax speakers in main cabin (can keep these as one zone if necessary)
2 coax speakers in bow
1 sub in main cabin

Thanks in advance for your expert guidance

 

[scokill]

RA670 has a dedicated sub output so that's taken care of. Now, the sub has to be linked to one of the zones so it will go up in volume when one of the zones volume is turned up. You can also link zones 1/2. Good news is that you can separately control the volume to the zones or turn them all up or down with cycling through with volume knob push.

I would use zone 1 for the main cabin. You may have to split the outputs for the amp. You could then use zone 2 for the speakers in the bow, zone 3 for swim step area.

My set up is Zone 1 front cabin speakers, Zone 2 rear cabin, Zone 3 tower speakers. I keep zone 1/2 linked although I may unlink if someone is sitting in front and wants it quieter. I keep the subwoofer linked to Zones 1/2 almost all the time. All of this is easier to do/manage from the Fusion App on iPhone than digging in the menu structure with knob pushes and turns.

 

[RadioJet]

Ok good, confirms what I was thinking. Zone 3 will be swim step, that one’s easy - speakers direct wired to RA670 output. Zone 1 and 2 will be RCA from head unit to RCA inputs on amp. Question is, where does the sub connect to the amp? Since there are only 4 RCA inputs, are we back to splitters on one or both sets of RCAs?

 

[scokill]

Ok good, confirms what I was thinking. Zone 3 will be swim step, that one’s easy - speakers direct wired to RA670 output. Zone 1 and 2 will be RCA from head unit to RCA inputs on amp. Question is, where does the sub connect to the amp? Since there are only 4 RCA inputs, are we back to splitters on one or both sets of RCAs?

I laid out the challenge in my previous post at the start of thread. I may be missing something, but I think you will have to sum Zones 1, 2, and 3 single output (or pick Left or Right) and go into 3 of the inputs on the amp. The 4th input would be for the single sub out. I don't think you can just use a Y cable to combine them, there are converters to do it right. This is not ideal but the only way to control 3 zones and sub with that amp. I would use channels 6/8 for the sub and bridge the output. You will lose stereo separation. If you were set on 8 channel the Garmin Fusion, JLM800, etc. would have been better choice for flexibility but in the $800-$1,000 range. I have 2 amps. 4 channel for 4 cabin speakers, and 5 channel for tower and sub. 2 channel bridged for each tower and single sub channel on the 5 channel.

 

[AZMark]

You’re limited by that 8 channel amp really only having 4 channels/2 zones of inputs.

I am looking to do the exact same zoning as you and I’ve been struggling to figure out how to do it cheaply without a separate sub amp and I don’t think it’s possible.

Your sub would require 4 channels of that amp. You either have to input a dedicated sub signal into those 4 channels or use your low pass filter on those 4 channels so you don’t have the option to run any full range speakers on any of those same 4 channels.

 

[TimW451]

+1 on the advice from @scokill & @AZMark. I don’t think you have enough amps/channels for 8 speakers and a sub unless you wire the main cabin speakers in parallel. (Which I wouldn’t do.) I think the least cost option is to buy a monoblock amp for the subwoofer. That would let you use the HU and Rockville amp to drive 4 speakers each.

 

[RadioJet]

Agreed guys, and thanks. I’ve purchased a monoblock amp for the sub and (after running new 4ga wires from batt buss bar) hopefully life will be simpler and sound better! The 8 channel spec of this amp is a little deceptive; would think they’d have a better way to handle subs. But it is what it is and will work for now with the new setup. Really appreciate all the input, will send photos of all when done.

 

[AZMark]

I agree it’s deceptive on those 8 channels.

I think I’m going to do a 6 channel with 3 sets of inputs + a mono sub amp. That will give me 3 zones of speakers + the sub that can all be adjusted (or at least turned down) independently with some RCA knobs.

This is the most affordable I can find:

https://nvx.com/products/mvpa6-900w-rms-marine-v-series-6-channel-class-d-compact-powersports-amplifier

 

[RadioJet]

Sooooo… got fed up with the issues with the Rockville 8 channel, including 1 dead channel, and a broken hex wrench tip in speaker connection screw from previous installation. Now have an 800w monoblock for the sub, and have ordered the NVX 6 channel amp mentioned by AZMark. Looks like a decent amp for the money. Would love to go with Wetsounds or other high end gear but the budget doesn’t allow. Anyway, after those get installed this week, looking at adding cooling fans to move some of this hot Florida air around the area forward of the helm where the amps are. Progress report to follow…

 

[AZMark]

Sooooo… got fed up with the issues with the Rockville 8 channel, including 1 dead channel, and a broken hex wrench tip in speaker connection screw from previous installation. Now have an 800w monoblock for the sub, and have ordered the NVX 6 channel amp mentioned by AZMark. Looks like a decent amp for the money. Would love to go with Wetsounds or other high end gear but the budget doesn’t allow. Anyway, after those get installed this week, looking at adding cooling fans to move some of this hot Florida air around the area forward of the helm where the amps are. Progress report to follow…

I hope that works out great!
I was about to order one and decided to check out offerup. I found a fairly new 6 channel jl car amp for just a little more than the nvx. I don’t have to worry as much about the marine rated with freshwater and dry weather.

 

[TimW451]

Caution BOAT ahead:

Since you have a Fusion 670, you may want to consider a Fusion Apollo amp. It “pairs” with the 670 to use Fusion’s DSP tech to optimize the audio profile. This is great it you are a “set it and forget” person. There is no manual tuning, so If you like to tweak your amp you won’t like it.

 

[RadioJet]

I hope that works out great!
I was about to order one and decided to check out offerup. I found a fairly new 6 channel jl car amp for just a little more than the nvx. I don’t have to worry as much about the marine rated with freshwater and dry weather.

Good find! The NVX just showed up, surprised how small it is compared to the Rockville. Seems solidly built.