Active/Passive switching?

[Soulman]

I bought a couple of powered Wharfedale EVP-15 speakers about a year ago, during an old stock clearance sale, for an absolute bargain. Now that the guarantee is up I was thinking of trying to convert them for dual passive/active use, to provide me with back up in the event of an amp failure.

 

My intention was to wire in a speakon socket between the internal amp and the crossover, (which is separate from the amp board). I could then use the speakers passively (..unplugged of course!) with a Peavey 2600 power amp I have. They could still be used as powered speakers or monitors when required.

 

My concern is that when powered by the Peavey, the output side of the internal amps would be subject to the power being delivered to the speakers. Would this be a problem, or would I have to install an isolating switch (..double pole?...), between the crossovers and the internal amps, for use when the Peavey was connected? I’m trying to keep this as simple as possible.

 

Over more years than I care to remember, I have built many speaker cabinets and crossovers, but I have never tried a mod like this, which is straining my limited practical electronics knowledge.

Can any tekkies out there advise on this?

[gyro_gearloose]

Theres a fairly easy way around this, if you don't mind using jack plugs/sockets instead. As you may know, some jack sockets have two terminals for each pole which are only connected to each other when nothing is plugged in. As soon as you do plug something in, the circuit between each terminal on each pole is broken and one set of terminals are then connected to whatever is plugged into the socket.

 

If you were to wire such a socket between the amp and crossover, whenever you plug an external amp into the jack socket the circuit between the internal amp and crossover would automatically be broken.

[MarkPAman]

My concern is that when powered by the Peavey, the output side of the internal amps would be subject to the power being delivered to the speakers. Would this be a problem

Yes, I've seen this take out both of the amps concerned. :)

, or would I have to install an isolating switch (..double pole?...), between the crossovers and the internal amps, for use when the Peavey was connected?

As far as I can see, that should do the trick.

However, make sure that everybody who uses the system knows about the switch, what it does and when to use it.

 

Come to think of it a DPDT (2 gang) will enable you to wire it so that the socket is never connected to the amp. Perhaps that's what you meant. ;)

[Rob_Beech]

Then again you might be able to benefit from using the amp inside the box to power more than one cabinet in the event of failure, PROVIDING THE AMPLIFIER IS CAPABLE OF DRIVING THIS TYPE OF LOAD.

 

A whole range of options are there for you to try, whether any of it is worth it or not I am not sure. Probably to the having a backup amp part, but possibly not anything more complicated.

 

Rob

[MarkPAman]

I thought of that Rob, but decided it was very unlikely that the amp would have spare capacity for another speaker. I also considered using it to run only an external speaker, but that's just silly. :)

[mi-ul]

What about putting a speakon lead onto the amp output - you can patch it into the socket to use as a powered speaker and can be unplugged to power another speaker or to use a separate amp with the speakers. At least with this you know that the amp is completely disconnected if you're using a separate amp.

[Ben Langfeld]

The external amp could then be connected to the wrong NL4. The switch is the safest option.

[mi-ul]

The external amp could then be connected to the wrong NL4. The switch is the safest option.

 

The suggestion was for a speakon lead rather than an extra socket - although admittedly this could be barrelled onto a lead

[paulears]

mi-ul's idea is the one I prefer. A simple glad, short bit of cable, and maybe even a right angled speakon? Nice and neat, and reliable.

[Ben Langfeld]

The suggestion was for a speakon lead rather than an extra socket - although admittedly this could be barrelled onto a lead

Oops, you're quite right. You'd think I'd have learned to read posts twice by now :)

[mi-ul]

Oops, you're quite right. You'd think I'd have learned to read posts twice by now :)

To be fair I hadn't thought about connecting it up backwards - barreled or via a socket so it was probably a point worth making!

[Soulman]

I only joined this forum in the last few days, and am amazed at the number of helpful responses I have had from it. I’ll be passing it on to like minded friends.

Many thanks to all who have replied. Prior to posting, I had actually considered most of the suggestions made subsequently by you all, so it has been very helpful to me to get the reassurance on possible options. The final solution will depend on the space available in the speaker cabinets to mount any recessed connector plates, double pole switches etc., and also to avoid any trailing wires and plugs to avoid transit accidents.

 

Thanks for the confirmation that leaving the output stage of the unplugged internal amp effectively connected to the speaker driven by an external amp was not a good idea. That was an area in which I had no knowledge.

 

The isolator type jack socket would be the simplest most compact solution, but I’m not sure about the reliability of the connection over time in the powered speaker operation (spring contacts in the rest position), if the speaker was used regularly externally powered. When externally powered, the spring contacts are pushed apart. (Possibly weakening the spring over time?)

 

I quite like the idea of a speakon chassis socket, and 90 deg speakon plug from the internal amp, so that only one power supply could be connected at a time. This would avoid an isolator switch. Does anyone know where I can source a 90 deg speakon plug (UK) ?

 

Thanks again to all.

[Chris Beesley]

90 Degree Speakon or in component parts .... Speakon plus 90 Degree Converter

[Soulman]

Many thanks Chris.