Let me clarify a few points as it seems there is a lot of mis information on this post.
Quote from: Bigg Dogg.
"I believe that Wetsounds WS420 has basically used 2 separate bass knobs as to independently control tower and cockpit speakers. This is the conclusion I have come to studying their product. I don’t see the need to spend the money on their rather simple design."
Bigg Dogg, You couldn't be farther from the truth on what the WS-420 is. I am sure you are just mistaken on it by the studying you have done. The WS-420 is a lot more than a couple of bass knobs.
The WS-420 is in fact a very complicated unit. And the only unit like it on the market. It is so unique that we won the Innovations Award for 2008 for engineering and design for the WS-420.
Here is the best way to describe it. The WS-420 is TWO equalizers in one chassis plus a microphone built it. A completely separate equalizer for the tower and a completely separate equalizer for the in boats. As well as separate volume for the in boats and separate volume for the towers. So 2 EQ's in one chassis. Plus it adds bass boost and sub freq adjustment. The built in microphone is where it gets very complicated on the design side. The microphone has it's own volume control. It also mutes the towers speakers when the key is pushed and you can talk over the tower speakers. Once the mic key is released. It is a 5 second delay and the towers begin to play again. It only goes through the tower speakers and not the in boats. It is a high voltage line driver as well providing higher voltage to the amps. It has an aux in for an i pod so it can be used without the need for a head unit. It also has a feature we call "boat link" It has an aux output allowing you to link up to other boats and play one source to multiple boats.
So to do what the WS-420 can do in a half DIN chassis. You would need to buy. Two separate line driver equalizers. Plus an add on microphone. And that would still not give you the boat link ability but you can do that with outboard line drivers and y adapters etc…So you would be way more in terms of cost to be able to do what the WS-420 can do.
To the original poster.
What was described as a bass boost knob. Is not correct as just a bass boost knob will not control just any amplifier. Also, most bass boost knobs only work with intended amplifier. Most only work for sub amps or when in low pass mode.
What is the proper way to described it is to add a "universal amplifier level control" and some are called “universal bass remote level control. PAC makes one called the LC-1. This is a passive unit. On the sonic site posted, there is one from schose, rlc. I just wanted to make sure that was clear so you did not order a bass knob that only worked for a specific amp. Make sure it is universal.
If you have 3 amps in a system. You would add one for each amp. But this would only work in a system with a head unit or eq.
JL makes an active one called the CL-RLC. What is better about this one is it is active. So it has line voltage from the source.
You do not want to just go from an ipod to the amps. The ipod does not have enough voltage to drive the amplifiers. There is also impedance issues but I will not get into that.
So you will need something to provide voltage.
So in your set up with no head unit. The pacs or passive ones will not work. (they will in a system with a head unit or eq)
The cheapest solution is to get two of the JL CL-RLC. They are about $60 each. You will use an ipod to rca plug into a Y into both. Then one will go to tower amp and one to the in boats and sub amp. You can add a 3rd if you want sub control as well.
It may be as cheap to do a single eq like the clarion. But this will not give you complete control of the in boats and towers separate. But will allow you to fade from in boat to tower and give you a line driver.
Next option is to add the WS-420 of course as this will give you the control of towers and in boats and line driver and ipod input etc...
But remember when doing it. Add something that has voltage into the amps. DO NOT just plug the ipod in.