Zener diodes in the tweeter circuit

srinath

Member
2010-02-12 4:09 pm
Zener diodes are in my Infinity Kappa 5.1 crossover in the tweeter circuit, I believe it was to protect the Emit-R's. Which were killed anyway by an errant screw from a previous life.
I have dynaudio Car tweeters in it now. Its a MD100/2 variant. Its also 4 ohm. However I find its a bit weak. Lacking in SPL especially. I also have some hissing noise audible in the tweeter. I cant imagine that is in the tweeter itself, these have a good reputation. Of course I got it used, so who knows.

Would getting rid of these Zeners get me a bit more spl ? What would be the side effects ? These dynaudio's are supposedly impossible to blow, they are 100 watt with 200w transient capacity.

Thanks.
Srinath.
 

Lojzek

Member
2012-02-10 12:12 pm
Croatia
Zener diodes are effectively reducing tweeter SPL when the right condition
occurs. You'd probably get a very small increase in tweeter SPL if you removed
these. Those are 1N5348N 5W, 11V, zener diodes. Regarding Dynaudio, it can
withstand a 100 W of program power, not by itself. Thin voice coil tweeter
wire can't take much heat without being destroyed. This is a small tweeter
with not that powerful motor, so its SPL can't be very high. Manufacturer measured
close to 86-88 dB. Check the dcr, should be 5,6. Maybe the wrong XO values
additionally reduce the FR.
 
Last edited:

srinath

Member
2010-02-12 4:09 pm
I will measure it, but I think I got even lower DCR, like 3.3 ohm, making it a 4 ohm.
That was one criteria for picking it, 4 ohm dynaudio for a 4 ohm Emit-R swap.
Anyway its getting 5k and up from the values in the crossover if it is 4 ohm.
I don't think I'll get close to 100 watt for complete output anyway.
So you don't think removing the zeners will do any good ? I'll let it be then. I'd like to get it maybe 2-3 db so it matches the mid and tweeter.
Thanks.
Srinath.
 

Lojzek

Member
2012-02-10 12:12 pm
Croatia
This is a quick sim of the MD 100 with original filter and some mods.
Might be very well that this is the lack of HF you have. Try to bypass
the existing 8uF with a 7 uF and leave the small inductor as is.
 

Attachments

  • Dynaudio MD 100.gif
    Dynaudio MD 100.gif
    20.1 KB · Views: 267
  • Dynaudio MD 100 mod 1.gif
    Dynaudio MD 100 mod 1.gif
    20.4 KB · Views: 262
  • Dynaudio MD 100 mod 2.gif
    Dynaudio MD 100 mod 2.gif
    20.5 KB · Views: 261

srinath

Member
2010-02-12 4:09 pm
Oh, OK I have these 10uF's I pulled from something - nice audio grade, I'll swap that 8uF for the 10, and see if it needs more, then see if I can add 4.7's or some other.
IMHO it could use 6dB, if you ask my wife, she's want it to stay where it is. So I'd say 3dB is about where we'd both claim - its as far as we can take it.

Let me start on it if I can tonight and see what it does.
I have to hack something off the cover first, then maybe solder away.

Cool.
Srinath.
 

srinath

Member
2010-02-12 4:09 pm
There is a 2.5mH inductor in series and 150 uF cap with the woofer - I think its a 350 hz 2nd order XO.
How much spl is it reducing especially in the lower bass. The inductor probably has 1-2 ohm resistance right ? That could make the difference for this set up.
Thanks.
Srinath.
 
The woofers are close relatives of the Dynaudio MW180's.
I am thinking of straight wiring it - by passing the crossover. Would that help them make more spl ? Or is that going to cause more distortion and other ill effects, without much gain.
Thanks.
Srinath.
Many forget that even if the woofer is straight wired, it *always* has an internal series inductor which cuts highs.

Relatively mild 6dB/oct and you can't choose the crossover frequency, you have what you have, but definitely attenuates highs and rises impedance ... exactly what an external series inductor does.
 

srinath

Member
2010-02-12 4:09 pm
@Lojzek - The mid is a MD140/142 dynaudio.
I ran it in the Volvo crossover, where it made a good 4-6 db more than the other 2 in the same XO.I cant believe its so mid range heavy in the car.
I put it in the Infinity 5.1 XO and the mid toned down nicely, there is a 3.3 ohm resistor nicely taking it down to the level of the other 2.
The tweeter benefitted from your tip of the cap in addition to the other cap. Its good with spl just a db or 2 below the mid and sounds damn good.
The woofer is now cleanly slotted in for freq and for spl.
I think I may try to tone the mid down, maybe replace the 3.3 ohm with a 5 ohm, but its great as it is.

@JMFahey - you're talking about the coil's internal inductance with climbs as its frequency rises - which is why a Woofer isn't a full range speaker right ?
Anyway by ear, it sounds awesome, I have to finish the other speaker and may make new cabs etc etc for them, so far I've been boogering some old cabinets I got for $20.
Thanks.

Cool.
Srinath.