Upgrading Mordaunt Short MS15 Bookshelves

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
These were a fun buy. 20 year old MS15 speakers, designed by Robin Marshall at a guess. They have his style. :D

An externally hosted image should be here but it was not working when we last tested it.


Inside is a simple 1st order bass, second order treble filter with those polyfuse things. Elac 180NS10 paper bass unit and small (ferrofluid?) polycarbonate tweeter. Lots of stuffing and a 3.3uF non-polar electrolytic capacitor which I replaced as a matter of course with polypropylene and got a cleaner sound straightaway.

Sound is a bit muffled and it tends to sibilance at high frequencies, which I would think is cone breakup from the bass around 5kHz. I'm going to get rid of some stuffing and damp the side and top panels next in BBC style.

To this end, I've got some 4.5mm Regupol rubber and cork floor underlay and some rubber sheeting. Bass cutout is 147mm, PCD 185mm, tweeter cutout is 50mm with room for up to 72mm diameter replacement. Cabinet is 325mmx230mmx160mm, 7 Litres in golden ratio internally. Been modelling a second order crossover which looks much better too. :cool:
 

Attachments

  • Mordaunt_Short_MS15_Loudspeaker.jpg
    Mordaunt_Short_MS15_Loudspeaker.jpg
    76.5 KB · Views: 2,757
  • Mordaunt_Short_MS15_Rear_View.jpg
    Mordaunt_Short_MS15_Rear_View.jpg
    102.1 KB · Views: 567
  • Mordaunt_Short_MS15_Disassembled.jpg
    Mordaunt_Short_MS15_Disassembled.jpg
    88 KB · Views: 2,229
  • Loudspeaker_Damping_Pads.jpg
    Loudspeaker_Damping_Pads.jpg
    134.8 KB · Views: 626
  • MS15_Crossover_FR.JPG
    MS15_Crossover_FR.JPG
    60.9 KB · Views: 1,581
  • Mordaunt_Short_MS15_Crossoverr.jpg
    Mordaunt_Short_MS15_Crossoverr.jpg
    20.7 KB · Views: 1,533
Hi,

Stuffing works fine for sealed, not that good for vented, but vented
lining style has no advantages for sealed, just stuff sealed. You
don't need a foam lining for sealed. You can vary stuffing density.

I can't find anymore the cheap industrial solid self adhesive vinyl
floor tiles that are excellent in layers as cabinet wall damping.

If the tweeter is twist removable from the front plate, its the classic
and best by far Audax original, ferrofluid and edgewound formerless.

similar bass mid driver :
ELAC 5 inch hifi bass speakers woofers PAIR KEF JPW | eBay

rgds, sreten.
 
Well, you know me, sreten. I just like trying stuff. If panel damping is used by the BBC for closed box, it must do SOMETHING! The rolled up stuff is more light self-adhesive expanded foam. :D

These bass units are remarkably like the ELAC ones you quote from eBay. Just bigger dustcaps as far as I can see.

Only marking on the tweeter is TW6x9 and it's a one piece moulding AFAIK. Sound very smooth, so will persevere with them. All units are 6 ohms resistive.

Edit. Oh wait. The tweeters twist apart into two pieces of faceplate and motor/diaphragm. Hope I haven't broken the wires! LOL
 

Attachments

  • Elac, 180NS10.jpg
    Elac, 180NS10.jpg
    104.5 KB · Views: 272
  • Elac, 180NS10,speaker 002.jpg
    Elac, 180NS10,speaker 002.jpg
    101.2 KB · Views: 133
Last edited:
the original 10mm Audax were coded something like 'TW10**' so its possible they are OEMs made by Audax. These speakers certainly have something ovdar the models that followed them.

Id agree that 2nd order maybe good for the woofer but the round bezel version of the audax i bought back when maplin sold them, had a fs of something like 2.5khz. I understand the motivation to maintain simplicity, but maybe 3rd order on the tweeter, OR a zobel (i know you like these) will help. Although i liked my old audax i found that the resonance was very noticable. This was mainly due to me using textbook values for a 2nd order at 4k. My only grace was that i did use the impedance plots, and a table of values to rough it out. I dont recall the frequency response but i just remember the resonance showing through unless i crossed at 5k
 
Last edited:
Yup, it does look like an Audax TW6X9 plastic tweeter. I guess that is good. :)

I tried to allow for acoustic centres of 50mm and 10mm here. A bass Zobel worked out best on phase and flatness with more inductance. Didn't change much else apart from increasing attenuation on tweeter and tweeter Zobel for 0.1mH. Might work. Should get rid of some sibilance with more bass riolloff, and up the bass a tidge which won't be a problem.

Now must get on with ordering the parts. The crossover board has lots of room.
 

Attachments

  • Test_Circuit_MS15.JPG
    Test_Circuit_MS15.JPG
    59.4 KB · Views: 125
  • Test_Crossover_MS15.JPG
    Test_Crossover_MS15.JPG
    23.1 KB · Views: 164
Hi,

The much copied Audax tweeter is the eponymous cheap tweeter.

An externally hosted image should be here but it was not working when we last tested it.


The original and still near the best twists out for different faceplates.

The original has a formerless edgewound voicecoil in a ferrofluid gap.

rgds, sreten.

Fs is high and they are designed for a 3rd order roll-off with a single capacitor.
 
Last edited:
3rd order acoustic at 5k or beyond makes perfect sense Sreten. Back when i was a teemager these tweeters were good value, but a little difficult to use. I remember thinking that they would work better in a 3way crossed high. I found them to sound pretty good as long as their resonance was far enough out of band. However i did cut out the part in front of the dome, and that couldve made things worse. Also from recall these domes had a small nipple at the apex of the dome.
 
Last edited:
Interesting remarks on the tweeter. It looks like it has sharp natural rolloff at 3kHz and at 0.03mH vc inductance and flat won't need a Zobel. :)

This is the Audax TW010F1, but very similar apart from the faceplate. This could work very well with the woofer which will peak around 1.4kHz on a second order. A question of suck it and see, I think. I'll leave the tweeter crossover essentially unchanged. Happens it looks very good with the Visaton TW70 too, if this all goes pear-shaped.

I enclose some data for future reference. :cool:
 

Attachments

  • Audax_TW010F1.JPG
    Audax_TW010F1.JPG
    56.2 KB · Views: 167
  • Audax_TW010F1_Parameters.JPG
    Audax_TW010F1_Parameters.JPG
    96.7 KB · Views: 129
  • Audax_TW010F1_Tweeter.JPG
    Audax_TW010F1_Tweeter.JPG
    36.4 KB · Views: 149
Is it with real drivers measurements?

Nope. Just trying to sim a paper woofer with similar electrical characteristics and align it for the acoustic centre which you can measure from front of baffle to pole gap. :D

Bit rough and ready, but hey, what else an you do? Listening tests will show if phase is right, because imaging gets good when it is.

In fact, I'm revising my ideas on this, because the tweeter is not really much like the plastic dome Visaton DT94. I think I'll need more rolloff on the bass. Bass filters are quite predictable, IMO, as long as you account for woofer voicecoil inductance.
 
diyAudio Chief Moderator
Joined 2002
Paid Member
Don't assume the Z plane distance is to VC gap, its usually less than that, closer to 4/5 the cone's depth. That pole gap rough estimation comes from HF drivers and horns pro stuff quick set up practices where the scale and assembly are much different.
 
Like I say, Salas, it's all a bit rough and ready. Bass filter is going to be 1mH series, 8uF and 2 ohms shunt by the look of it. Had to resolder a broken wire on one tweeter. Teach me to take it apart. :)

The aerosol carpet glue was more fun than a box of frogs. Most of it went on me! But job done with the rubbery and cork stuff, I think. Waiting for glue to dry. :cool:
 

Attachments

  • Underlay_Artistic_Shot.jpg
    Underlay_Artistic_Shot.jpg
    100.7 KB · Views: 1,562
  • Floor_Underlay_Loudspeaker.jpg
    Floor_Underlay_Loudspeaker.jpg
    96.2 KB · Views: 290
Interesting remarks on the tweeter. It looks like it has sharp natural rolloff at 3kHz and at 0.03mH vc inductance and flat won't need a Zobel. :)
yes the FR looks fairly good. I couldnt find or recall the details at the time, but my comments about the obvious resonance if crossed too low or shallow are still relevant, in my mind at least. I have no idea what causes the effect i perceived. All i know is that i didnt like their low end reproduction. Whilst theyre a classic high value tweeter, they were cheap, so hardly flawless.

To me the most interesting thing about these is the large 'surround'. I often wondered how much contribution it made to the total output. Almost like a 20mm mylar cone tweeter, with all but the center dome covered up.
 
Last edited:
Got them back together with the cabinet changes. :D

4.5mm rubber and cork panel damping underlay on the top, bottom and sides. A single sheet of BAF wadding on the back. The BBC idea is you add damping to the smaller, more rigid panels. The front and back panels will flex more with added mass, so don't damp them.

Bass is LOVELY and smooth and deep, 4cm from the back wall as recommended. Midrange seems to have more detail. The side panels are a lot more inert. This is really what you'd do with bass reflex on accepted ideas, but this is closed box.

The top end is still letting things down a bit. Sibilant. Might be dried-up ferrofluid, or the cheap tweeter itself because the treble crossover is OK. More work to do. Enjoying this. :cool:
 

Attachments

  • Mordaunt_Short_MS15_Wadding_and_Damping.jpg
    Mordaunt_Short_MS15_Wadding_and_Damping.jpg
    88.2 KB · Views: 271
After extended listening, I have put all the the wadding back in the (closed box) cabinets. It's one of those tradeoffs that seem abound in audio, and a bit frustrating TBH.

The speakers were just TOO LIVELY without it, and fatiguing in the midrange to listen to. Maybe it's the paper bass and the lack of rolloff in the cone-breakup region due to the simple single coil bass crossover.

Maybe what I have done is balance the relatively lively paper bass with heavy damping from the wadding. It might work better with less wadding on a plastic cone. This is a shame though, because the bass is just not as clear with all the wadding.

Ah well. They are decent little speakers anyway, but I don't think I want to fiddle with them any more. Other fish to fry. :)
 
Maybe what I have done is balance the relatively lively paper bass with heavy damping from the wadding. It might work better with less wadding on a plastic cone. This is a shame though, because the bass is just not as clear with all the wadding.

Then measure them and find out. If this is the case then the crossover is not adequate and needs modification. Get the xover right and then you can go with the optimum amount of damping material for the cabinet alignment.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.