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Multi-Way Conventional loudspeakers with crossovers

Newbie Question on tweaking Mission M71
Newbie Question on tweaking Mission M71
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Old 10th November 2005, 05:43 PM   #1
ewhale is offline ewhale  Malaysia
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Join Date: Nov 2005
Lightbulb Newbie Question on tweaking Mission M71

I am new to DIY and am thinking of tweaking my Mission M71 bookshelf speaker. The speaker sounds quite harsh. I got it second hand and some ppl are suggesting that I should recap it. I'm new to all these so I'm here to ask for opinions from you gurus here. Please let me know what should be changed. Thanks for any help. Here are the details about the speaker:

L1: ELYTONE 2000L.39
C1, C3 : ELYTONE 10uF +- 10% 63V NP
C2 : 5.0K 100V
R1, R2: 5W 2.2 Ohm JF

Enclosure type: 2way reflex loaded
Freq Response: +-3db 65Hz to 20kHz
Crossover Freq: 2.8Khz
Nominal impedance: 8 Ohm compatible
Recommended Amp: 25-75 W/ch

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Old 14th November 2005, 08:05 AM   #2
ewhale is offline ewhale  Malaysia
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I have opened the speaker box already. There were six screws at the back of the speaker holding the plastic panel with the terminals. The crossover is attached to the plastic panel. The felt inside is quite thick. It is about half an inch thick. I did not replace the felt. I have however tried replacing the capacitors (two in each box) with Solen caps. The change in sound is very noticeable. A small sound stage started to emerge. The music sounded more fluid. The bass tighter. Overall, the sound is more musical and dynamic. Some CD still sounded very bright but it is more bearable than before. I have only played them for less than 10 hours. I'm not sure how the sound will change further as I burn in more.

As the Solen caps are much much bigger than the stock caps, I did not mount them. They are now sticking off the crossover board. I worry this might cause problem down the road. Is there any ways that I can improve the situation? I'm thinking of using the thick white glue that we sometimes see on PCB but I don't know what is it and where to buy. Tried blue tack but they are not strong enough. I'm thinking of making paper caps with spandex at the opening so that I can wear them like condoms over the big Solen capacitors. I don't think the paper will russle. Anyway, any other tips?
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Old 14th November 2005, 08:33 AM   #3
Scottmoose is offline Scottmoose  United Kingdom
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Location: UK
Aha! The old headache-inducing Missions again. Mission speakers have never been a favourite of mine for the very reasons you've come across -they are very, very bright. At least, the ones built over the last few years have been, and it's not helped by this daft notion that's taken off recently of 'wide bandwidth' for the speakers, and particularly, the amplifiers. Still, that's another story. Onto sorting out your headache... oops, I meant speakers ;-)

Two suggestions.

1) Add a 1 to 1.5 Ohm resistor in series with the tweeter. That'll take the top end down. You may have to play with the values to hit upon one you find most suitable. Alternatively, junk the existing internal cable to the tweeter, and use a run of 24AWG magnet wire instead. Similar effect.

2) Pull the crossovers out of the cabinet completely (you'll probably need to get a couple of replacement terminal plates as you say the corssovers are glued tot he existing ones, but that shouldn't be too expensive. Alternatively, just blank it off with a piece of MDF or the like. They can go in a plastic (NOT a metal!), or a nice, oiled wooden ciagar box on the floor behind them, or better, with the rest of your hifi gear. This achieves a few things: a) it removes them from the worst possible place a crossover can be: the speaker cabinet. Far too many nasty vibrations in there. Tannoy cottoned on to this 30 years ago, so it's not a new idea, and what's good enough for Tannoy... b) it gives you more space to optimise components. I'm no believer in fancy 'audiophile' gear, but higher quality componets (which need not be expensive) do make a subtle difference, and they tend to be bigger than originals. c) It allows you to optimise the cable runs for each driver. 12 - 10AWG copper zip-cord for the mid-bass (well, mid, if we're being honest) driver, 24AWG magnet wire for the tweeter would be a good place to start. (as they're already biwireable, you could try the magnet wire for the tweeter as it stands)

3) Try adding a little stuffing to the cabinet. Pillow-stuffing or some such should help here.

4) Brace the mid-bass driver against the rear cabinet wall with a length of dowel-rod between the magnet and the back of the cabinet. Should cut colourations a little.

Hope some of this helps. All of it is completely reversible, so play around.

"'That'll do", comes the cry of the perfectionist down the ages.' James May -The Reassembler
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Old 3rd December 2005, 07:35 AM   #4
Joe-HT is offline Joe-HT  Thailand
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Join Date: Dec 2005
Location: Near Bangkok
Hey ewhale! I'm interested in comparing notes with you!~ I have the M71 and the m71i with the improved crossover and cabinet bracing. The i is really nice sounding, but I;m going to upgrade caps anyway to help ward off upgrade fever! if you're still around, I could post the differences in the two versions of crossover.
ps- the white stuff is hot glue. You can buy it in any dept. store or market! The gun is only $5 or so!
Have fun! I'm off to look for caps here in Bangkok.
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Old 3rd December 2005, 02:39 PM   #5
amperex is offline amperex  United States
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Join Date: Feb 2005
Location: MI
Default Sorry.....

I have bought a pair of those speakers years ago & they suck. Find some DIY designs with good drivers that suit the box size & built it. Forget saving $ on salvaging the cross-over.
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Old 13th June 2019, 05:29 AM   #6
eli17 is offline eli17  United States
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Join Date: Nov 2017
Location: American Canyon CA.
I know this is an old tread but I found it! I have a pair of M71i speakers and if you just plug the vent holes they compare favorably with my MB Quart ones.. changing out electrostatics is ALWAYS an improvement as ALL of those suck but the best caps (film and foil) are very steep.. you can settle for metalized polyprop with ok results I think the dude that says they suck has bose ears or or dolby in the chain I have built large arrays with focal and scan speak drivers and missions are the best budget speaker there is my amp is a VTLst85
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Old 13th June 2019, 10:10 PM   #7
eli17 is offline eli17  United States
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Location: American Canyon CA.
i meant electrolytic not the speaker type electrostatics in my previous post
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