Anyone heard of MDL Electronics Capacitors? .. thinking I may need to improve?

[Deaf Cat]

Hi wondered if you may be able to help,

I'm starting to think I need a little more clarity from my tweeters, found my crossover, and it seems quite simple with a total of 6 components.

There is a 5.6uF 5.0V NP +-10% MDL cap which I'm thinking if changed may help my tweeter to give a bit more clarity...?

(MDL web site: Professional manufacturer of Non-Polar, Bi-Polar Aluminum Electrolytic Capacitors for speaker Xover. )

There is one inductor that looks like a coil, with no figures on it, there is what I think is another inductor with 0.90MH on it.

There is what I guess is a resistor with 6.0K 100V on it, another one with 5W 3.9OhmJ stamped on it, both made by MDL.

Last of all there is what I think may be a cut out of some sort, looks the same as the thing put in an amp when converting it to 240V from 120V, if it draws too much it blows. A little round flat thing with two legs.

So sorry for the terrible discriptions of things, quite clearly I'm a beginner, learning by a bit of diy here and there.

Many thanks for any comments or thoughts,
Cheers
DC

[dabbler]

A great deal of what you hear from your tweeter is room and baffle reflections / diffractions. Experimenting with felt blocks, room treatment or waveguides will have far more effect than changing capacitors.

[wintermute]

One thing to be aware of is that a 5.6uF electrolytic capacitor will have quite a high esr, much higher than a 5.6uF film cap. If you change to a "better" cap it could affect the crossover function assuming the original design took into account the esr of the electro.

The small flat round thing sounds like a polyswitch. polyswitches make a good cheap speaker protector. They go open circuit when their current rating is exceeded, and when they cool down they start conducting again. A bit like an automatic resetting circuit breaker. They are most useful if the speakers are ever likely to be sujected to abuse (for instance at a party).

Tony.

[Deaf Cat]

Thanks dabbler for the tip, I discovered that a while ago, quite amazing when you have not come across the room treatment thing before, but, I already have the room as treated as much as possible, well, as much as I am allowed ;-)

Tony, thank you for the info, very good to know! I'm guessing the only way to tell is to try a film cap and see or hear if its messed up the sound or not... or have another look at the crossover and work out what is exactly in the path for the top and bottom ends, and learn more :-)

I'm guessing the speakers would clip/distort a bit before the polyswitch tripped?
The only slight distortion that I have come across was sorted with stopping the room reflections, as the speakers have never tripped in 10 years or so, I guess removing the polyswitch may cut one item in the signal path out.... and not be too destructive :-o never know I may get a bit of clarity ;-D Possibly worth a test..?

Cheers :-)

[sreten]

Hi,

A pair of Solen polypropylenes are not expensive from Falcon Acoustics, £2.77 each.

rgds, sreten.

[Deaf Cat]

Cheers for that they seem a nice reasonable cap, however, I've taken the back of the speaker again just to follow the tracks, Oh glad I did!! the thing I thought was a cap is a cap but it is on the low freq + going to the low freq - on the crossover circuit board. I don't seem to be able to tell what is the cap on the high freq side :-(

So I've taken a pic

The hi freq - comes back from the speaker, top left hand corner of the board and follows along the top of the board on a nice wide track to the top right hand corner of the board, being connected to a wire from the cotton real coil on the way across the board.

The hi freq + from the amp is just below the hf - on the right hand side of the board, first the hf + goes through the polyswitch, then through the large yellow cylinder thing that has 6.0K 100V on it, then the other wire from the cotton real coil connects to the hf+ (goes to the hf- via the coil) then through what I guess is a resistor the white rectangular box with 5W 3.9OhmJ stamped on it then out to the driver.

I was expecting to find a cap to block the low freqs on the hf bit of the board - yes I'm confused and would love to know what is going on - Please

On the lf side there is a coil which blocks the hf, but what is the cap for, going from + to - ?

Really love to understand what is going on in my speakers - not as easy as first thought :-) Interesting stuff though!

Very much look forward to knowing what is going on..

Cheers
DC

[Deaf Cat]

Ok I think the big yellow cylinder is a Metallized Polypropylene Film Capacitor, only seen electrolytics before, Yeepeee so no worries about going from electrolytic to film with a lower esr possibly causing trouble then :-) as we have a film already.


I'm guessing the 6.0 is the uF figure and the K is 10% tolerance...


Ah just thinking the blue electrolytic on the lo freq lets the h freq signal back to the amp so the woofers don't try to do the hi freqs too.. :-)

Slowly making sense :-D As long as I'm on the right lines....

[sreten]

Hi,

The "big yellow thing" is a film capacitor, so the tweeter has a series
polyswitch, series cap, parallel aircored inductor, and series resistor.

I think its value follows a convention for film capacitors
of indicating a multiplier of 1nF, so its actually 6uF.
Certainly polypropylene, I can't tell if its metallised or foil.

The bass mid has a series ferrite cored inductor and a parallel non-polar
electrolytic capacitor. the jury is out on whether upgrading would make
an appreciable difference, might do if it was old but IMO probably not.

Some will insist the bass inductor needs to air-cored, it won't be
cheap with the same value and DCR, here of course you wouldn't
use a bipolar electrolytic, that just wouldn't make sense.

A simple tweak would be to change the value of the tweeter
resistor to say 3.3R for more treble detail, the paranoid
would probably remove the polyswitch, I wouldn't.

Without knowing the speaker model and performance ambition
of the box and the drivers, its hard to say what is the best option.

rgds, sreten.

If you upgrade the tweeter cap, use the old one in the bass section.

[Deaf Cat]

Thank you for that :-)

...hope you don't mind another question or two

The big yellow film cap blocks the lo freq to the tweeter, but what is the parallel air core inductor for.. just to make double sure no lo freq get through to the tweeter?

6uF cool i'll have a look around for some :-)
does it matter if it is film or foil?

yes I'm with you on leaving the parallel elec cap on the low side, for me, keep things simple to start with.

"Some will insist the bass inductor needs to air-cored, it won't be
cheap with the same value and DCR, here of course you wouldn't
use a bipolar electrolytic, that just wouldn't make sense"

Sorry just checking I understand, so if at some point I go air core on the lo inductor, I would swap the electrolytic for a film cap, or would not need a parallel cap at all?


"A simple tweak would be to change the value of the tweeter
resistor to say 3.3R for more treble detail, the paranoid
would probably remove the polyswitch, I wouldn't."

Would a 3.3 improve clarity (make things a little more crisp), or just give more detail..
Given the wire used from binding posts to crossover I also think I will leave the polyswitch, and maybe change that wire.

"Without knowing the speaker model and performance ambition
of the box and the drivers, its hard to say what is the best option."

Ah ha, they are Ditton AV3's, just looking for a little more clarity up top, with out loosing the smoothness - not that I'm fussy ;-) They seem to have started to give a nice 3D image after the last few system tweeks, I've had some CDM 1NT's running yesterday and today, top end is clearer more detail, technically more complete I'd say, maybe more real sounding, but 2D image, and lacking life and 3d that the AV3's seem to have...

Tried to have a look in the CDM 1NT's to see what caps etc was in there but could not see, did not want to remove the driver.


"If you upgrade the tweeter cap, use the old one in the bass section."
Good, I don't like throwing things away, Just swap out the electrolytic, even though it's 5.6 and the yellow is 6..

Cool learning lots today, even thinking maybe I should build a complete crossover rather than mess up my existing working ones with soldering and re soldering... hmmmm maybe just start with the hi film cap

Thanks for your time &
Cheers for all the interesting info!!

[sreten]

Hi,

TBH I wouldn't change the tweeter capacitor, looks fine to me.

You have 2nd order electrical filters on both drivers, an inductor and
a capacitor, in opposite positions for the low pass and high pass.

I'd try 3.3R resistors first, and possibly 2.7R.

rgds, sreten.