Hi - does anyone have an orphan Mission Cyrus PSX (Mission Cyrus II vintage) ?? I have two Cyrus II's but just the one PSX amp.

I am wanting to bi-amp my Mission 780 II Argonaut speakers. I could use the Cyrus II without PSX for the L+R tweeters and the Cyrus II with PSX for the L+R Woofers, but even better would be the Mission recommended route of one amp and PSX per side (this needs a simple internal fix to make each amp Mono). 

Anyway, I know its a long shot, but if anyone has one please contact me, even if you keep your eyes out around the audiophile haunts over the next few months, that would be great. Thank you.

Hi
It looks like you want to horizontally bi-amp. So Left Tweeter>Amp>Right Tweeter, Left Woofer>Amp>Right Woofer. So you will be bypassing the crossover? In which case you will need some sort of active crossover.

However, what you can do is to vertically amp, so 1 amp per speaker, using the speaker crossover and driving all the cones in the speaker. No need to turn the amp mono, by the way. This one is easy to do and less expensive.

Which one is it?

Sadly I have no Cyrus kit, so the best of luck in your hunt.

Hi Jon - Mission Cyrus information on bi-amping is quite hard to find and when you do find it, it takes a few reads to get what they mean. You can do either horizontal bi-amping, or vertical bi-amping, with vertical being the Mission Cyrus recommendation. The BUT is that both left side and right side amps need to be the same for vertical bi-amping AND to turn them into mono you need to open them up and snip link X12 (basically cut one lead-out in a way that you can re-solder later if you want to return to stereo - maybe tape the end so there is no shorting) and linking the two pins marked "M” next to it - short wire to be soldered in. Do that and you have mono-blocks.

So that's ok for two Cyrus II amps, or two Cyrus II amps both with PSX power supplies, but not ok with two amps and one PSX. Horizontal bi-amping can be done with different amps (e.g. two amps and one PSX) with the amps in stereo and a Cyrus II powering left and right tweeters, and a Cyrus II +PSX powering left and right woofers.

HOWEVER in both cases you end up volume balancing the speakers manually, either horizontal bi-amping, balancing both tweeters against both woofers, or vertical bi-amping, manually balancing the left speaker against the right speaker, which is probably why Mission Cyrus prefers vertical bi-amping.

Neither is ideal but I would like to find another PSX!

Not sure what you mean by, "No need to turn the amp mono” for vertical bi-amping - how would you wire that??

DIY one?

www.diyaudio.com/community/threads/building-a-cyrus-psx.266050/

www.avforums.com/threads/cyrus-ii-psx-let-the-modding-begin.860989/

Apologies for the delay in responding! I am also confused by the myriad of different definitions of vertical and horizontal bi-amping so what follows is my version. It comes down to the position of the crossover in the intended application. In a  standard setup, the crossover is always associated with the loudspeaker, either built in or as a small separate box. It is called a passive crossover as the low and high pass filters are set by the designer. You can't really change them... fairly easy, you just plug and go!

However when you want to vertically amp or drive a loudspeaker with it's own dedicated power amp then things can get a little more complex. Note that the amps are still using the passive crossover in the speaker. It's the output from the pre-amp which gets a little more complicated. There are two options here, depending on the type of pre-amp speaker outputs that are available.

Option 1 - Single speaker output, left and right channel. Turn your power amps into mono devices and connect up left output to left amp and right output to right amp. Simple enough, even when Cyrus indicate you have to do some internal work on the power amps.

Option 2 - Dual output, as per the diagram below. What you do is connect the Left outputs on each channel from the pre-amp to the left amplifier and speaker, and the right outputs on each channel from the pre-amp to the right amplifier and speaker. Connect up and enjoy. Vertical amping is good, and is a large step up over the traditional single power amp. I am vertically amping using this method with my JBL L-300 and my Net Audio Quad 405-2s.

Extra option: madly complicated but you drive each cone with it's own dedicated mono power amp. Never done it, and given the costs not going to happen - at least for me.

The third method is to horizontally amp as you mentioned. There are a number of options and ways to go but all of them mean that you need to move the crossover as per the diagram below. That generally means an active crossover and additional complication. The plus side to active crossover methods is a marked increase in the quality of sound over a vertical or standard amp solution.

Option 1:Use an amplifier to drive a left and right woofer. Use an Amplifier to drive the Left and RIght tweeter.

Option 2: Just like Vertical amping insert mono amplifiers and drive each cone with it's dedicated amp.

I hope that clears things up a bit!

oh, yes when vertically amping, you are quite correct! Both amps should be the same.

I forgot to add, I have used horizontal amping on my World Audio Design KLS-3 loudspeakers. So the chain is as follows;

Source -> Audio M2 Line -> Marchand Active crossover (Low, middle and high pass filters) -> 3 X Quad 405-2 -> Left/Right Treble, Mid and Bass

If you can do it, I thoroughly recommend horizontal amping. Downside it costs like mad.

Thank, Jon - that's very comprehensive and I fully concur (always wanted to use that word). I use bi-amping in my 5:1 lounge set-up where the 7:1 Onkyo Receiver allows the spare channels to be linked to the L+R channels to power bi-amping. It makes a big difference to the L+R channels, whereas the Centre is only bi-wired and I am not sure if it makes much difference at all.

I will put here the Mission Cyrus II docs to show what they offer in case its helpful to someone down the track:

Bi-amp diagram


Bi-amp instructions


Mono instructions


Mono PCB picture


I am just looking for an extra PSX so I can Vertically bi-amp 

Sept 7, 2022 21:02:54 GMT 12 RdM said:

DIY one?

www.diyaudio.com/community/threads/building-a-cyrus-psx.266050/

www.avforums.com/threads/cyrus-ii-psx-let-the-modding-begin.860989/

I read those threads but ... way beyond me. Thanks, anyway.