Mission 753 speaker modding

[petercom]

Originally Posted by justblair

I am interested in your suggestion here Peter. I thought that since it was out of the signal path this would not be so critical. Hence I ordered a nichicon muse (ES I think). Can you tell me more as to why this cap is important?

In a speaker crossover all components are in the signal path in one way or another. For example the 10uF helps to form the crossover slope (in simple terms it bypasses the driver, so if its ESR is rising with frequency the driver will get more high frequency 'hash' than is desirable). Reducing its ESR should reduce treble harshness.

Originally Posted by justblair

I had planned to upgrade the coffin resistors. I think I may have found my choice. Do wirewounds not have their own inductance? Is this in the slightest bit relevant, or too small a value to worry about? .

The inductance of the wirewounds we supply is in the fraction of a microHenry range. So it might trouble you if you were using them for RF, or had a treble unit going up to 100KHz, but not audio frequencies.

Originally Posted by justblair

mmmmmm. I know you are talking sense here.. My curiousity is burning me, I have to admit to being influenced by planet10's site. I suspect that aesthetically the idea of solid wood phase plugs (in rosewood of course) is what appeals the most (with felt plugs on the bass driver). STUPID I KNOW! I really must try and stop thinking about this.

As for the stiffening of the cone, I am guessing that is why those that do this on fostex cones treat the cone with puzzlecoat? The 1db drop in sensitivity doesn't strike me as being a problem, I'm going to bet that I am being niave?

The crossovers AFAIK include resistors in the signal path to attenuate the different sensitivities of each section. Can the values not be adjusted to counter this?

The cost of failure on modding the drivers will probably put me off. I do wish that someone had pioneered here so I could make a more informed decision.

The reason I said it is because I actually have done that. When I joined Mission there was talk of 'upgrading' the 753. I fitted the bass units with phase plugs and the MF response went haywire.

Don't try and draw parallels with Full Range Units. These have a different set of characteristics - whizzer cones and the like - and the cone shape is designed for gradual breakup, not stiffness.

As for sensitivity the bass and mid units have no series attenuation, only the treble unit does. You could, I suppose, increase the treble attenuation to make up for the loss of MF, but you may have to adjust the crossover as well to take account of the change in response of the drive units.

I just don't think it's worth doing.