Speaker HELP please for a know-nothing.

[DaveK]

Hi Guys,
I am no audio technician so I need basic help please.
I have two Mini-T amps and I am trying to replace my Cyrus Power amp with them. I've got them both coupled up and everything works, (LEDs light up and the on/off switch and volume controls work fine). My speakers are Mission 773s with two sets of terminals for bi-amping.. I'm using one Min-T with a previously used speaker cable to feed the lower frequencies into the lower pair of terminals on the speakers, with the other Mini-T and my previous 4N silver cables into the upper speaker terminals. I've swapped everything round repeatedly but no matter which combination of Mini-T and speaker cable I feed them with the only speaker terminals that will give listenable sound are the lower ones. What I get with any and all Mini-T and cable combination feeding the upper speaker terminals is a very (as in very) low volume that sounds as if its coming from the bottom of a closed tin can .
I've put my cheapo multimeter across the Mini-T outputs set on the 200mV DC setting and with no inputs, (as advised by a more knowledgeable friend , to measure the DC offset) and get a reading of 82 on oneMini-T and 91 on the other. I am advised that this is too high - is it?
My multimeter's lowest AC scale has a maximum of 200v and when I try to measure the output across the Mini-T outputs it is so low that it does not register on the multimeter.
My more knowledgeable friends seems to think the crossovers in the speakers might be faulty - the speakers were purchased second hand off eBay some time ago so I guess it is possible.
If I could push my luck, can you keep it simple please with any response.
FWIW I've switched both Mini-Ts and the Pre-amp off just in case I doing any damage as things are at the moment.
Thanks for any help.
Dave.

[chris661]

If you just use one amplifier per channel, do the speakers work? By 'work', I mean treble coming from the tweeter, bass coming from the woofer(s).



The above shows the connections you should be making. Note the bridges between the low/high terminals have been removed.

Have you connected the inputs to the T-amps correctly?

[DaveK]

Originally Posted by chris661

If you just use one amplifier per channel, do the speakers work? By 'work', I mean treble coming from the tweeter, bass coming from the woofer(s).



The above shows the connections you should be making. Note the bridges between the low/high terminals have been removed.

Have you connected the inputs to the T-amps correctly?

HiChris,
Thanks for your input.
Yes I have removed the bridges and yes, the tweeters appear to be working when only one amp is used to feed both bottoms sets of speaker terminals with the bridges re-installed.
Regarding the wiring diagram above I attach my freehand sketch which I think shows that I have made the correct connections.
The situation I seem to have is that tweeters work fine when the speakers arefed from one Mini-T but when the speakers are fed from 2 Mini-Ts (with bridge removed, the tweeters sound very thin and 'tinny'. Although, having said that, I had to struggle with my ear right up against the tweeters to hear anything when fed by one Mini-T, but having no experience of these matters I'm not sure how loud the tweeter should sound - if the tweeter sound should be very obvious then maybe I do have a crossover problem - any further thoughts?
Ain't hi-fi fun?
Cheers,
Dave.

[Andy5112405]

What happens if you swap the two 3.5mm stereo jacks with each other.

[DrDyna]

If it sounds fine driven by one amplifier with the bridges on, then it's probably not a crossover problem.

I noticed you are feeding one amplifier from the unbalanced output and the other from the balanced, have you tried using just one amp (bridges on speakers) and changing which output you use on the preamp? perhaps one or the other of the outputs doesn't work properly.

Edit: Which Cyrus pre do you have? The only one I can find states that it doesn't have balanced outputs at all.

[Andy5112405]

Originally Posted by DrDyna

If it sounds fine driven by one amplifier with the bridges on, then it's probably not a crossover problem.

I noticed you are feeding one amplifier from the unbalanced output and the other from the balanced, have you tried using just one amp (bridges on speakers) and changing which output you use on the preamp? perhaps one or the other of the outputs doesn't work properly.

That's what I'm getting at in the post above. Are the RCA and XLR outputs at the same level ?

In fact, can they be used at the same time ?

[DaveK]

Hi guys,
Thanks all for your interest, As previously stated, I'm a complete numptie at this hifi game so anything is possible in my mind, Th Cyrus pre-amp I have is a aCA7 which is no longer a current model. Whether or not it can handle simultaneous outputs from balanced and RCA terminals or at the same level I have no idea.
I can tell you that I have tried every combination of inputs, outputs and cables, all with the same effect.
Also, if I shut off the 'working amp' (feeding the lower speaker terminals), the only sound is like listening to a small speaker inside a sealed tin can with very low volume,
Cheers,
Dave.

[DaveK]

Hi Guys,
Having had a look at the back of the Cyrus I see that there are two sets of RCA ouitputs as well as the balanced 3 pin XLR outputs. So I've disconnected the XLR outputs and connected up that Mini-T amp using the second RCA outputs - result: exactly the same, very low volume tinny sound out of the tweeters and beautiful music out of the two larger speakers (Mission 773s each have two x 11cm 'large' speakers with the tweeter positioned between them).
If I gently touch the speaker cones whilst music plays I can readily feel the cones vibrating on all the larger speakers but the tweeters seem motionless. I have undone the tweeter fastening screws to get to the back of them but there is no apparent signs of any problem. The tweeter terminals are readily accessible in this situation so is it possible that someone could give me an idea of what a cheapo multimeter reading should give me with music playing, and what scale I should set the multimeter at?
My logic says that this might enable us to decide whether it's the tweeters or the crossovers that are the problem, but I know nowt, so I could be wrong .
Thanks for any help.
Dave.

[chris661]

There's nothing wrong.

The crossover on the tweeters will probably be quite high, so you won't hear much coming from the tweeters. But I'd bet if you play music, then switched off the tweeter-amp, you'll notice.

You'll need to adjust the levels (volume control on the front of each amplifier) so there's the correct amount of treble.

Speakers visibly vibrate with low frequencies only. There is a reason, but you don't really need to know it. The point is that you won't feel the tweeters moving at all. If you did, I'd be worried.

[DaveK]

Hi Chris,
I am in no position to argue with you, as I've said before, but you'd lose your bet . Turning the tweeter amp off has no noticeable effect on the music that I can perceive and it is not possible to balance the sound - with tweeter amp turned up max and and the 'bass' amp turned down to barely audible listening levels they still massively overwhelm the tweeters.
Dave.