Mordaunt Short MS10i - Ageing?

[Bazz4CQJ]

I bought my MS10i's about 1994, originally had them on floor stands fed with a NAD3020 and was very happy with them. Domestic factors meant that they eventually were moved to wall mounts, which I never felt so happy with, but last week they came back on to the original stands.

Maybe I was expecting some big improvement, but I didn't notice it. Of course, the NAD, the speakers and I are all nearly 30 years older.

Does anyone know whether the 10i's stand the test of time well or not? Playing the NAD through a number of speakers recently, that seems to be as a good as ever.

B

[Radio Wrangler]

I think you just have to take the grilles off and give the surrounds a gentle poke.

Identify the drivers and look around for the wisdom on them. Some fresh capacitors in the crossover might be a good idea anyway.

David

[Bazz4CQJ]

Originally Posted by Radio Wrangler

Some fresh capacitors in the crossover might be a good idea anyway.

David

I have no idea what those caps consist of (never had the enclosures open) or
what is the most common effect of ageing of the crossover caps has on the speaker. They certainly don't seem (to me) to be lacking high frequency response.

A quick search of Google for comments on ageing of the 10i's revealed little, but I did not specifically search for info on the drivers.

B

[Radio Wrangler]

It's gradual, so you don't notice it over time. Expect AC rated electrolytics and they dry out, losing capacitance and raising ESR. Loss of C in the capacitor coupling the tweeter won't affect the highest end much, you get problems in the crossover frequency region, the lowpass on the bass/midrange becomes less effective and the highpass to the tweeter moves up.

Look around and you'll find generally favourable reports from sensible (non-audiophool) people who have done this to older speakers.

David

[Bazz4CQJ]

Thanks for those comments, David. I'll investigate .

B

[joebog1]

Speakers are speakers!! Like us they age. Suspension gets tired just like our knees and hips.
Spiders also age, although I have had some arguments about that. A pretty easy and quick thing to try, is unscrewing the movers from the boxes and turn them upside down. Whay was up is now down. After ( think you said 30 years ?? ) cones have fallen somewhat skewiff of how the factory made them. Its called gravity >
I just a small fortune for a pensioner on a full set of surround sound speakers, also made by Mordant Short. I am still building the class D system to drive them. BUT I must say, with black piano polished finish, and my initial testing with a bench amp, they should be superb.

AS a final test, have a CRITICAL look at surround cone suspension. It fades!!.
Like my Tannoys, after 50 years there was NO foam surround left at all. Thats why I paid $100 for a pair of Tannoy Cheviots ( re-released recently for £5999 UK for a pair ).
Go figure. CHECK surrounds and even alignment by eye.
They are nice speakers!! >

Joe

[Beobloke]

Great little speakers.

In addition to what everyone else has said, if yours have MS's 'Positec' tweeter protection system, then bypass it.

It's effectively a voltage dependent resistor that increases in value as the input level rises, in order to protect the tweeter. Sadly they age and can become unreliable as they get older, thus gradually cutting off the treble.

Assuming you're not intending to explore head-banging levels with the speakers, then it's perfectly safe to solder a wire link across it.

[Bazz4CQJ]

Thanks for comments. I seem to have made some substantial improvements just by changing the layout. Initially, I'd just made a guess, but I got a tape measure and plotted the layout on paper and realised that things were not what I thought (I know it sounds daft, but there we are!). So having done no more than that (yet) I'm much happier with them.

I've been searching Google for info on ageing, and most of the comments seems to relate to installing new caps (3.3 and 7uF) and removing the Positec protection device. What would be a good make for replacement caps? I guess that 6.8uF will do if 7uF cannot be found? There's a wirewound 4.7R resistor in there too which can go high. I also realised I have the 10i Pearl editions, which seem to be desirable variant (slightly larger cabinets and some other nice-to-have features). I recall buying them from a local shop in Headington (Oxford) and it seems that I got good advice; as above, the MS10's were rated for their price and I also see comments that they very much suited the NAD amps.

I've seen comments that MS were bought out and and the new company did a poor job; not sure about that.

B

[Bazz4CQJ]

Seems like not all MS10's had the same crossover networks; mine have two caps in parallel and an inductor - nothing else.

B

[Radio Wrangler]

As crossovers go, that looks disappointingly crude. Single-order networks, 6dB/octave roll-off. No level or time equalisation. Compare with the LS 3/5A crossover!

Might be worth checking that there isn't anything more on the way to the drivers.

I wonder if this is a case of a reasonable speaker where later models were savaged by accounta... er, subject to intensive value-engineering?

David

[dave cox]

Film caps

Air-cored inductor

[Bazz4CQJ]

Yes, nice components, but not many of them. Further investigation get's a bit harder. The tweeter can be taken out (forward) of the front panel, but I think the woofer may be held in place with adhesive; there are no screw fixings visible at the front. The cabinet is quite densely packed with fibrous material, which looks like you might get it out but have hard time getting it all back.

B

[PJL]

On the other hand your hearing may have aged rather than the speakers?

[dave cox]

Although a crossover might only contain a handful of components (re) designing one needs the ability to measure the resulting frequency response / dispersion. This comes down to owning a known / calibrated microphone, and for practicality a computer (with a reasonable ADC) plus software to do all the smoothing / plotting. Even with all that it's still not trivial!

Is there any notable differences between each speaker when playing in MONO ?

dc

[Bazz4CQJ]

During the period since my last post, I have been pursuing the problem of my disappointing sound system, generally making little progress....until I decided one day to press the 'loudness' button on the NAD, going from off to on.

Transformation! The change was very dramatic, sound quality changed from being "thin to full". In all the time I've had the NAD, I don't recall setting the control to ON previously (perhaps momentarily).

The NAD user manual suggests its use for low to mid level volume settings, and this is certainly where I am. I'm now looking at the schematic trying to figure out exactly what the switch does (clearly it changes 'equalisation' components in line). Could it be possible that components in the OFF circuit have aged badly and are affecting sound quality, but setting it to ON "side steps" those components? I really do think that something is "suspicious" here.

Re the MS10's, one thing that I did do was turn them upside down, as suggested by Joebogs (woffers now at the top). Now, I am reluctant to go on record as saying that this improved things.... but they do remain upside down relative to their original orientation . The plastic trim with the MS logo on it easily permits removal and re-orientation, which I hadn't expected.

B

[stevehertz]

I can't speculate about any potential fault in the NAD, but since the dawn of time operating the loudness button on a hifi amp can subjectively 'improve' the sound. I would wager that's what you're experiencing, no more. But if it's a/the solution, don't feel 'wrong' leaving it on. As has been said, our ears change over time, and this, maybe coupled with frequency response changes in the ageing drive units can be the cause of your disappointment.

[Uncle Bulgaria]

The loudness button is there to increase the subjective "fullness" of the sound at lower volume levels as you describe - when the volume's turned down, the quality of the sound alters as there's not enough 'oomph' compared to your expectations of the same instruments played live. With the Loudness on, it comes back to more what you expect, restoring the subjective balance of frequencies. I believe it boosts the bass mostly.

[Bazz4CQJ]

Whatever the reason, though I never used to engage loudness, the system sounds so much better with it on. I think things are back to "normal".

B

[Radio Wrangler]

Loudness controls are intended to allow you to compensate for the change in frequency response of the average human ear at low levels.

Fletcher & Munson produced curves showing the frequency dependent sensitivity of normal hearing at several levels. They showed decreased sensitivity at bass and treble ends with the effect getting stronger progressively at lower levels.

So the 'loudness' control was introduced on various amplifiers to compensate. Serious manufacturers used tapped volume controls so that the bass and treble boosts with loudness on, were dependent on volume pot position. The effect being made to diminish as you turned the volume up and the response of your ears changed.

The idea was to let you listen to music quietly, and get the same apparent frequency content as if you'd wound the wick up.

Later amplifiers cut corners, and where a loudness switch was provided it gave a pre-set bass and treble boost with no linkage to the volume pot position. It saved them the cost and availability difficulties of a tapped pot. You are assumed to switch it out yourself when choosing to listen to loud stuff.

It's one of those things you have to make your own mind up about whether you like it, rather like all other varieties of tone controls. It's worth knowing whether you have tapped volume pots, though, so you can know whether the effect is varied or fixed.

Has something gone wrong in your system, that poking the loudness button seems to compensate, or is it simply a subjective thing that you like? I suppose it's unlikely that similar failures have happened in both channels at once, so maybe you've just discovered the loudness button and like the effect.

David

[Bazz4CQJ]

Thanks David, the NAD does indeed have centre-tapped pots and one of the things the loudness switch does is open/close a circuit from the tap to ground via a 5.6k resistor and 0.1uF cap in series. However, that switch also does other things too early in the pre-amp stage. I've never looked at the NAD schematic previously, and there's a lot of it and the PDF copy I have is not great, so slightly heavy going. For anyone who is interested, loudness is set by switch S301, though 301 contains two switches in one component; one does loudness the other sets mono-stereo.

I am open-minded (or empty minded?) about what the true explanation of what has gone on here, but the bottom line is that I've got things back to working in a manner I can live with. A bolder man might want to delve inside the NAD, but I take the view that 35 year old amplifiers are best left unmolested unless intervention is absolutely necessary.

I'd seen centre-tapped pots and wondered where they fitted in to the grand scheme of things.

B