I'm digusted, Mordaunt Short,cheapskates

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Hi, don't often enter here, usually Subwoofer Forum. But, I got excited about some bass I was getting from my mains, (my sub being down), I cranked up the bass hit the Loudness, and one speaker started distorting.:bigeyes: Investigation found a vibrating cab, the back panel, I thought, was plastic covered, NOT! I removed the woofer and the stuffing and found my Mordaunt Short MS 40's look like this...
[img=http://img26.picoodle.com/img/img26/4/1/27/mikee55/t_27jan08001m_edeeee3.jpg]

Is this good practise in manufacturing of cabinets. Surely the back panel should be Dense?

iUSERTLO72p:mad:
 
Contraversial view: you got pretty much what you paid for; why be surprised? Price in the shops is 6-8x the manufacturing cost, and you have to look at the dealers for most of the mark-up. That's just the way it is.

So yes, maybe it's not what you were expecting - but is it so bad? A rigid moulding probably has less stored energy than a cheap glued MDF panel... and the excellent Epos ES11 and ES14 were built this way too; it's not an absolute-quality issue if handled well.

But if you want to ratte the house on the same budget - go DIY.
 

limono

Member
Paid Member
2007-03-02 8:04 pm
iUSERTLO72p said:
Hi, don't often enter here, usually Subwoofer Forum. But, I got excited about some bass I was getting from my mains, (my sub being down), I cranked up the bass hit the Loudness, and one speaker started distorting.




This is not the way Loudness should be used .I guess your amp was distorting like a MOFO too. I wouldn't do that with "real " speakers. MS40i was the worst POS I owned -especially in the bass area. Regards, L
 
martin clark said:
So yes, maybe it's not what you were expecting - but is it so bad? A rigid moulding probably has less stored energy than a cheap glued MDF panel...

Executed well, such a panel construction should exceed the capabilities of any MDF panel. A huge cost to tool up for it, but if you can amortise it over a huge number of speakers. The B&W DM302 had the best execution of this kind of concept that i have seen.

dave
 
Hi

This is not the way Loudness should be used .I guess your amp was distorting like a MOFO too. I wouldn't do that with "real " speakers. MS40i was the worst POS I owned -especially in the bass area. Regards, L

Well Quote me.
and one speaker started distorting
It says one speaker. Seeing as they're an identical pair both should have distorted, yes?

I cranked up the bass hit the Loudness
I didn't turn up the volume, to allow headroom.

And seeing as I mention
I got excited about some bass I was getting from my mains, (my sub being down), I cranked up the bass hit the Loudness
Suggests, I normaly listen with no bass boost or Loudness:)

one speaker started distorting
, This was my main concern.I should have said one cab was buzzing.

Anyway, whats bad in your shop bought Loudspeakers?:) (DIY speaker builders, need not apply):D
 

ShinOBIWAN

diyAudio Member
2004-02-25 9:13 pm
UK
Here's a fix if your looking for one.

I suggest first off sealing the entire interface between the plastic and the rest of the cabinet. I can see in your photo that they've spot glued every so often. Then afterwards I'll look at either 2mm bitumen panels attached to the rear of the enclosure and on the plastic or if that doesn't work then contact adhesive some 2mm lead flashing to to it.

Doing this will get rid of any buzzing.
 
Good Finking Batman:)

If I used a piece of wood,of thickness, and glue battens around the back walls of all the panel. Would it make a solid rear? I suggest the battens, because I see Volume might be changed, assuming the volume to be accurate:cannotbe: Maybe, I'll get some T/S's measured, and apply some accuracy. Whils I'm at it, my sub is a sealed cab with Linkwitz Transform assisting, the MS's are ported, I wander if I can do away with the ports:scratch2: .


iUSERTLO72p:)
 
Re: Good Finking Batman:)

iUSERTLO72p said:
If I used a piece of wood,of thickness, and glue battens around the back walls of all the panel. Would it make a solid rear? I suggest the battens, because I see Volume might be changed, assuming the volume to be accurate:cannotbe: Maybe, I'll get some T/S's measured, and apply some accuracy. Whils I'm at it, my sub is a sealed cab with Linkwitz Transform assisting, the MS's are ported, I wander if I can do away with the ports:scratch2: .


iUSERTLO72p:)


By the time you completely re-engineer and rebuild an inexpensive pair of speakers such as these, I'd opine you'd be vastly further ahead with any number of "field tested" DIY designs - but that's already been mentioned I think.

Something about a silk purse?
 
I don't think the back pannel is the main culprit in the buzzing you heard. I agree it is probably worth gluing it all round but I wouldn't try to replace it with MDF.

The most likey cause of a buzzing sound is the wire in the cabinet as this tends to start vibrating and taps against the box or drive units.

I would think the bigest bang for buck improvment you could make to these speakers would be to improve the crossover as it looks like it has a single component on each drive unit + a resistor presumably in series with the tweeter. Unfortunately to do this you are either going to need to find someone who can take some measurements or get hold of some measurement equipment.

Are you using a HT amp with this as if you are and are using the crossover in the HT amp then there isn't much point in reworking the bottom end as its not being used all that much.

Regards,
Andrew
 

ShinOBIWAN

diyAudio Member
2004-02-25 9:13 pm
UK
Re: Re: Good Finking Batman:)

chrisb said:



By the time you completely re-engineer and rebuild an inexpensive pair of speakers such as these, I'd opine you'd be vastly further ahead with any number of "field tested" DIY designs - but that's already been mentioned I think.

Something about a silk purse?

Bit of experience and fun though. Tweaking can be rewarding even if the effort expended doesn't completely justify the results.
 
In the days of the Mission 700LE, 760i etc. a common cause of buzzing was the front panel had come loose in the joint that held it to the cabinet. the front had a tongue all the way round that engaged in a groove cut in the cabinet. During construction the cabinet was folded around the front and rear panels.
Easy fix was to brace the front internally at the point where it had come loose. Better fix was to glue all around the offending panel. I used to use epoxy glue, as it seeped into the joint and when hardened was better than new.
I did a fair number of these repairs.... but never twice to the same speaker.
 
Yes interesting

Definately loose back panel, clamped with my hands, it shut up:D

I could diy a box no probs, but I shot myself in the foot. I built a pair of Jericho Horns, huge things, that I had to let go due to WAF, I got the MS's for £20odd sterling, told her indoors and she bought them.DOH:bawling:

Bloody WAF, I love:hbeat: her till I'm gone, but ............oh you know.

So you see, Silk Purse yeah, but WAF:sigh:.....

I have the capability to meaure T/S, and I'd like to BiAmp with an active Linkwitz crossover, so I could loose the passive. The only other gripe, for those who didn't know, these things are 2 boxes in one, both chambers reflexed, 2 x 6" drivers one of which the upper driver has a fixed voice coil and dust cover which are not attached to the cone. Removing Bi-Wire jumpers seperate woofers from the tweaters! And to yellow dusters, block the ports.

iUSERTLO72p:)
 

FrankWW

Member
2004-07-29 7:59 am
n/a
For $5 - $10 you could fill in those spaces with non drying modelling clay ('Plasticine', 'Plastalina' are some brand names) and you you'd have a really non-vibrating panel. I doubt very much if you would even have to fill them completely. The stuff doesn't shrink and will keep its properties for longer than the drivers will last.

I've done it.

Get it at art supply stores.
 

jnb

Member
2006-12-30 11:55 pm
Re: Yes interesting

iUSERTLO72p said:
I have the capability to meaure T/S, and I'd like to BiAmp with an active Linkwitz crossover, so I could loose the passive.

If I understand that you currently cross actively to your satellites (or plan to), then I would definately try blocking the port and tweaking the crossover to suit.
 
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