Hello, and upgrading Mission 71i speakers

[AUDIO123]

Hi everyone!

I am a total newbie to all this DIY/modding stuff and glad I bumped into this site. It certainly seems very active regarding this field and from what I've read you guys are very knowledgeable. It certainly gives me alot to think about and opens a new door into the world of diy audio as opposed to buying ready made stuff off the shelf.

Ok on to my question:

I was wondering if you guys would be kind enough to point me in the right direction regarding the upgrading of components on the second order crossovers on my Mission M71i speakers. I realise it's a basic question and they are not so great speakers and it's not entirely DIY but it is my first project and I would like to see what kind of improvements can be gained from adding better quality parts (would like to limit spending to about £30-40 for the pair). So does anybody know if there are any sites out there that can help a total novice to understand and upgrade the crossovers components and what parts would be best to use (not overkill considering the quality of drivers used). I've read some of the threads in the loudspeaker section but the posts seem to be more for people with some knowledge.

Thanks!

BTW most of the parts are unbranded except the caps (C2+C3 are elytone 10uF (10%) 63V NP, R1 is 5W 2.7ohms JB, R2 is 5W 2.2ohms JF, C1 is 5.6K 100V). Don't laugh but this stuff doesn't mean a thing to me.

[pinkmouse]

Hi Mate , and welcome to diyAudio

I have moved your post to the loudspeakers section, and retitled it, as your questions will be better answered there.

For a first suggestion for your upgrade question, you might want to open the speakers up and have a look at the size/type of components in there, as most of the upgrade components are significantly larger than stock items. Draw a circuit diagram if you can trace all the connections, that will make things easier for others to help you, and also help your understanding of what is going on.

[leadbelly]

Hope you don't consider this threadjacking, but since I have 6 M70 speakers and have considered posting such a question, I thought I would throw it in:





Looks like a basic cheapo xover; what's best bang-for-buck upgrade?

[5th element]

Well it looks as if you have a nice air core inductor on the bass driver which doesnt need replacing.

It looks like a first order slope on the tweeter and looks to have a cap thats better then a nasty non polarised electrolytic, the black cylinder on its side at the top of the xover board. Unless its a continuation of the terminal cup.

In anycase I would guess the blue non polar electrolytics you can see are either zobels or shunt capacitors and you wont really get much benafit from replacing them because they are not directly in the signal path.

The resistors are good too.

I would say your best bet is replace any capacitors that are in the signal path with a good quality ones.

[leadbelly]

No, the black thing is the inductor on the woofer. I've sketched it out to make it clearer:

[5th element]

Ah well that helps a lot, show you guess work isnt always correct!

OK well its a second order on the woofer with a bit of extra damping (the 1R resistor)

And again second order on the tweeter 2r2 providing a small amount of padding.

OK well with that in mind, leave the inductors where they are, cored inductors are not bad by any means, the only major problem they suffer is saturation before an air core would. But these speakers can probably only handle a small amount of power anyway, so coil saturation is unlikely going to happen.

The resistors, as stated before are fine and dont need to be touched.

The capacitors are less then ideal, replace the one in the signal path to the tweeter with a polyprop from say wilmslow audio.

Capacitors in shunt areas dont affect the sound anywhere near as much as caps in the signal path, you could alter the ones in the shunt section of the woofers xover if you wanted to, but due to the quality of the woofer its probably not worth it.

So like before just change the cap in the tweeter signal path to something better.

The final step would be to actually measure the drivers for both impedance and frequency in the mission boxes and first simulate what the xovers mission has built does, and then either leave the xover alone, because mission have done a good job. Or make a new xover yourself.

Chances are mission have been stingey on bafflestep to increase quoted sensativity, so a redesign could give you a more pleasing tonal balance, if you dont like what you already have.

A complete redesign seems a little overkill for such a cheap pair of speakers because it would likely cost half the price of the speakers anyway to redo the xover with quality parts.