Speaker Selector Switchbox changes audio quality?

[JohnRoberts]

Big consoles will often have two stereo line level outputs that can feed two different studio monitor amps and speakers, for independent control. I don't see much need for more than two, but there are designs floating around the WWW for monitor controllers. Probably doing all the manipulation at input signal level, but that is speculation on my part.

JR

 

[Mr. Moscode]

There are a lot of powered monitors. You'd have to switch at line level to use those.

 

[Brian Roth]

There are a lot of powered monitors. You'd have to switch at line level to use those.

Hence my question a few posts above....

Bri

 

[RoadrunnerOZ]

In a studio environment whether powered monitors or amped passives you would normally switch at line level. I worked in a studio where we had wired up Westlake monitors powered by a Crown DC300A, NS10s powered by another DC300A, Auratones powered by another amp and a gutted TV with a 5W mono amp to power the TV speaker (to get the sound of what the mixes would sound like for a weekly TV music show on an actual 6” x 4” TV speaker). There was also a PFL speaker and another feed to the studio lounge speakers running off a Bryston amp. Everything was switched at line level, balanced - all switched from the console.

 

[JohnRoberts]

This discussion has gone off into the weeds. Commercial speaker switches have been in wide use inside hifi shops for demonstrating floor models.
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At the risk of repeating myself, I never designed a speaker switch but vaguely recall some DIY switches in use inside Peavey.
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Further, one of the gadgets I was involved with was a midi controlled relay switch box. IIRC this accessory gadget had 8 relays under midi control accessed via TRS 1/4" jacks. One Peavey artist/endorsee asked if he could use this relay box to control his guitar rig to switch between different amps and cabinet combinations. I cautioned him against switching tube amp outputs this way.

Of course he could probably cold switch his rig this way without damage, but we all know what would eventually happen. The relays were a couple amps so probably would have worked long enough to blow up his tube guitar amp.

JR

 

[ccaudle]

we should not ASSume that the audio will ALWAYS be muted when a speaker-level transfer switch/relay is activated

Now I'm imagining a more complicated box that has line level input and output and speaker level input and output connections, and when you hit the switch the line level signal is muted, the speaker connection is relay switched, then the line level signal is unmuted.

Ugg, now I'm imagining arguments over whether using a microcontroller or just logic gates to control it all is "more DIY friendly." Maybe I don't want to go there.

 

[Gold]

They're not engineers, most are hobbyists who just love music.

There are also the DIY Audio types who are more like us around here. They build things.

I think what you want for speaker switching is mercury whetted relays. They do well with low power and won’t weld themselves together with high power.

 

[Brian Roth]

Now I'm imagining a more complicated box that has line level input and output and speaker level input and output connections, and when you hit the switch the line level signal is muted, the speaker connection is relay switched, then the line level signal is unmuted.

Ugg, now I'm imagining arguments over whether using a microcontroller or just logic gates to control it all is "more DIY friendly." Maybe I don't want to go there.

My "rev 1" in 1980-ish did involve clacking relays as well as line sources. One power amp would be "clacked" into different speaker pairs.

Big problem was matching levels in the various sets of speakers. I threw in the towel and said "screw this!" lol and afterwards did a "each set of speakers have their own amp" so I could tweak levels and not require high-power relays/switches.

Bri

 

[RoadrunnerOZ]

If you used 2 relays, the 1st being the Mute ON, the 2nd being the connection to the speaker with a delay (RC?) on its coil, the same 2nd relay also disengages the power to the 1st relay by passing coil power for the 1st through a set of NC contacts in the second relay. The engaging switch for a speaker provides power for both its own relays. The Mute ON mutes the line input to the amp.

 

[Newmarket]

There are also the DIY Audio types who are more like us around here. They build things.

I think what you want for speaker switching is mercury whetted relays. They do well with low power and won’t weld themselves together with high power.

Are they available now given RoHS and equivalent compliance issues ?
Benign equivalents ?

 

[Newmarket]

Now I'm imagining a more complicated box that has line level input and output and speaker level input and output connections, and when you hit the switch the line level signal is muted, the speaker connection is relay switched, then the line level signal is unmuted.

Ugg, now I'm imagining arguments over whether using a microcontroller or just logic gates to control it all is "more DIY friendly." Maybe I don't want to go there.

I was thinking along same lines. You activate a control switch and the internals do the necessary switching and timing. Whether by logic and timing circuits or under micro control.

 

[Newmarket]

In a studio environment whether powered monitors or amped passives you would normally switch at line level. I worked in a studio where we had wired up Westlake monitors powered by a Crown DC300A, NS10s powered by another DC300A, Auratones powered by another amp and a gutted TV with a 5W mono amp to power the TV speaker (to get the sound of what the mixes would sound like for a weekly TV music show on an actual 6” x 4” TV speaker). There was also a PFL speaker and another feed to the studio lounge speakers running off a Bryston amp. Everything was switched at line level, balanced - all switched from the console.

Sounds great. But that's obviously a serious studio setup. "Studio" covers a wide range from small domestic setups to the likes of Rockfield et al.
Many won't have multiple power amp options or want to go that way.
And some will explicitly want to use the same amp type for all. Eg I used to know a studio owner who was only really happy using BGW as he thought they gave him the best for his reggae biased stuff.

I offer no opinion on whether this is valid approach but it exists.
Of course, if designing for your own use you can please yourself. It is DIY after all. But still good to have advice here that might save your amp or avoid your studio being decorated with speaker cone

But yes - it's all a lot more friendly if switching is done at line level before any power stage.

 

[Gold]

Are they available now given RoHS and equivalent compliance issues ?
Benign equivalents ?

I have no idea. I’m not concerned with commercial viability so I don’t pay attention.

 

[Newmarket]

Understood. But clearly a consideration for anyone here wanting to "DIY" it.
An aside - I recall Mercury Tilt Switches used in pinball machines. Not sure what used "These Days"

 

[Gold]

Understood. But clearly a consideration for anyone here wanting to "DIY" it.
An aside - I recall Mercury Tilt Switches used in pinball machines. Not sure what used "These Days"

Mercury whetted relays are what is used in the circuit breaker in the Neumann SAL74 lathe electronics. You can still get the original part from the 1970’s from the manufacturer.

 

[Newmarket]

Mercury whetted relays are what is used in the circuit breaker in the Neumann SAL74 lathe electronics. You can still get the original part from the 1970’s from the manufacturer.

Mercury whetted relays are what is used in the circuit breaker in the Neumann SAL74 lathe electronics. You can still get the original part from the 1970’s from the manufacturer.

Is that NOS ?

 

[Gold]

Is that NOS ?

Yes, although I won’t say what they are or where to look. They are not being manufactured anymore.

 

[RoadrunnerOZ]

Yes, although I won’t say what they are or where to look. They are not being manufactured anymore.

https://mercuryrelays.com/35-amp-relays/

 

[RoadrunnerOZ]

And these guys seem to have the same:
https://www.mdius.com/mercury-relaysThey used to use mercury tilt switches for boot and bonnet light sensors in cars - the modern switches and relays have to be really well sealed but still are available in some form or other.

 

[RoadrunnerOZ]

Tend towards a more mercurial sound. Dig out the Queen albums!