Sound systems and VHF

[WindyWindyWindy]

I have two problems and find I only have the one stone...

I could use, and I do appreciate that many will find this a horrendous concept in a sailing boat, a better sound system in the cockpit for entertaining. Ideally when there's only one or two other boats in a quiet anchorage, so perhaps a kilowatt of output and multi-coloured LEDs for the full disco effect..

The other is that, perhaps due to my advanced years and a habit of listening to amplified music, the VHF can be hard to discern.

Is there such a thing that would play stuff through a couple of smallish speakers and also connect to the VHF such that it will automatically switch to the VHF when the locals start their drunken singing on 16 so that I don't miss it?

It'd be good if it worked just to amplify the VHF without using to much power as I mostly don't listen to music.

A kind of amplifier to drive two speakers, with two inputs one of which it will switch to for a period if it detects activity, I guess there's a tricky volume matching problem there too of course.

Or am I better off using two stones and having a separate external speaker for the VHF?

 

[alahol2]

You could probably use a cheap mixer (like this) to connect your VHF to one of your existing cockpit speakers.

 

[dolabriform]

You could probably use a cheap mixer (like this) to connect your VHF to one of your existing cockpit speakers.

That mixer will only work at line level, not speaker level.

The output of both the VHF and the Music Device ( Car radio I presume ) will be at speaker voltages and expect a nominal 8 ohm impedance. There are devices ( duckers ) that are used in radio to reduce the music level when the announcer speaks, but again they only work at line level.

I can't think of an easy solution that would do this at speaker voltages.

 

[alahol2]

What would happen if you just connect both units to the speaker and they both 'speak'?

 

[dolabriform]

What would happen if you just connect both units to the speaker and they both 'speak'?

They would do, sort of... for a while... but the likelihood is you will then destroy** both amplifiers, so it's not really recommended.

** depending on the design of the amplifiers, the amount of damage will vary.

 

[Aquanaught]

I would go for a separate waterproof speaker in the cockpit for your VHF. It will be much clearer than trying to hear the speaker 'down below' and avoids complications such as wiring to amps etc.

 

[WindyWindyWindy]

That mixer will only work at line level, not speaker level.

The output of both the VHF and the Music Device ( Car radio I presume ) will be at speaker voltages and expect a nominal 8 ohm impedance. There are devices ( duckers ) that are used in radio to reduce the music level when the announcer speaks, but again they only work at line level.

I can't think of an easy solution that would do this at speaker voltages.

Yes, I was wondering if any of the purpose built "marine" music systems would take a VHF input, and switch automatically.
I guess not.

I hadn't considered the speaker level problem either, which complicates the idea a bit. I guess it'll have to be separate speakers.

 

[Dellquay13]

Some Handheld VHFs have an earphone out, which could connect to a sound system IF it had an autoswitching or priority input, to flip from music to the HH input whenever it detected an audio feed from the HH, but that IF is doing some heavy lifting in this scenario.
It’s a common feature on audio in commercial applications, but I don’t know much about marine or other car derived music systems. Maybe connect the earphone out into a bluetooth transmitter?

 

[WindyWindyWindy]

Maybe connect the earphone out into a bluetooth transmitter?

I did consider this, but it's hard to find one that just turns on without faffing about. Also, I've only got speaker out.

It occurs to me that the level problem could be solved by a switch on the speaker side so it was switching the two speaker outputs.

 

[Dellquay13]

I did consider this, but it's hard to find one that just turns on without faffing about. Also, I've only got speaker out.

It occurs to me that the level problem could be solved by a switch on the speaker side so it was switching the two speaker outputs.

Someone handy with a soldering iron and a bit of circuit sense could use a voltage from an ‘rx active led’ to energise a relay to switch the wiring to a speaker IF (big IF) such a led existed. I’ve done similar using voltage from an ‘RF receive active’ led on a wireless vocal mic receiver to flip a relay, in the distant past.

 

[WindyWindyWindy]

Someone handy with a soldering iron and a bit of circuit sense could use a voltage from an ‘rx active led’ to energise a relay to switch the wiring to a speaker IF (big IF) such a led existed. I’ve done similar using voltage from an ‘RF receive active’ led on a wireless vocal mic receiver to flip a relay, in the distant past.

I'd imagine it's not too hard to sense a voltage on the speaker wires and drive a relay from a microcontroller, which would give you sensitivity and duration control.
But can you just cut off a speaker like that without any problems for the amplifier or a massive clunk?

This stuff does appear to exist, but it costs a lot more than I would have expected. I guess it's a bit niche..

 

[Dellquay13]

I'd imagine it's not too hard to sense a voltage on the speaker wires and drive a relay from a microcontroller, which would give you sensitivity and duration control.
But can you just cut off a speaker like that without any problems for the amplifier or a massive clunk?

This stuff does appear to exist, but it costs a lot more than I would have expected. I guess it's a bit niche..

Sensing a voltage on the speaker line is awkward, it’s AC and it varies massively, stopping the relay chattering would be needed. Disconnecting the amp output to open circuit shouldn’t be bad for the amp, it’s just like an infinite impedance.
It’s very niche!

 

[dolabriform]

Sensing a voltage on the speaker line is awkward, it’s AC and it varies massively, stopping the relay chattering would be needed. Disconnecting the amp output to open circuit shouldn’t be bad for the amp, it’s just like an infinite impedance.
It’s very niche!

I was also thinking about a sense circuit that then switched a relay. It's fairly easy to build a detection circuit for the voice, rectify it and compress the **** out of the signal, then add an envelope to the switching voltage that has a long release to help further smooth out the dynamics.

You could attenuate the input signal on the sense circuit to make it easier to manage.

This is essentially how noise gates are setup to work in duck mode.

 

[Dellquay13]

I was also thinking about a sense circuit that then switched a relay. It's fairly easy to build a detection circuit for the voice, rectify it and compress the **** out of the signal, then add an envelope to the switching voltage that has a long release to help further smooth out the dynamics.

You could attenuate the input signal on the sense circuit to make it easier to manage.

This is essentially how noise gates are setup to work in duck mode.

Speaker level to line level power brakes are available, even as modules to get 100v line audio into telephone systems.
It’s do able inside a 12v vhf and car audio world, but faffy. Easy with off the shelf kit if you have space for a 19” rack and plenty of 240v.

 

[WindyWindyWindy]

Sensing a voltage on the speaker line is awkward, it’s AC and it varies massively, stopping the relay chattering would be needed.

I'd hook it up to a microcontroller input. At speaker voltages, an opto-coupler should work shouldn't it? And then you can decide how much prodding it takes to switch and how long it stays switched if the line goes quiet.
I'm still unsure if just dropping a couple of hundred watts of thrash metal wouldn't require some kind of protection, there's a lot of inductance there...

I was kind of hoping for something in a nice box.

 

[Dellquay13]

I'd hook it up to a microcontroller input. At speaker voltages, an opto-coupler should work shouldn't it? And then you can decide how much prodding it takes to switch and how long it stays switched if the line goes quiet.
I'm still unsure if just dropping a couple of hundred watts of thrash metal wouldn't require some kind of protection, there's a lot of inductance there...

I was kind of hoping for something in a nice box.

I don’t know if opto couplers are available for an ac input, I have only seen them in dc circuits.
Solid state output (transistor or IC block) amps are fine with just disconnecting the speaker line, a valve amp would be a different matter. Common onstage, but a bit scarce afloat these days

 

[WindyWindyWindy]

I don’t know if opto couplers are available for an ac input, I have only seen them in dc circuits.
Solid state output (transistor or IC block) amps are fine with just disconnecting the speaker line, a valve amp would be a different matter. Common onstage, but a bit scarce afloat these days

Well the LED part is just a diode, you don't need precision with the detection, just detection. I find VHF speakers are very quiet until they receive something.

I was thinking of the speaker being dumped back onto the VHF's amp if you switched it fast enough. This isn't stuff I know much about, which is probably very obvious.

 

[Dellquay13]

https://www.amazon.com/Russound-ADP...to+line+level+converter&qid=1745263285&sr=8-3

https://www.cloud.co.uk/product/3/CX163/

Add some 240v, tap the speaker adaptor off the vhf speaker, plug the line out into input 6 on the mixer, plug your music into input 1, and the output from the mixer into your amp.