Crossover Mission M33i

[sviru]

hi guys. I need help with this crossover. I wanted do change all caps with better ones - most of them are Electrolytic cheap caps. The thing is that they are 84uF in total... it is hard to buy such big caps.

Is there any way to change values C1 and C2 without changing L1 and make them "easier" to find? Something from range 2-20uf.

Thanks for help

[Inductor]

Just guessing because I don't know what you want to do (shop, brand name, etc., etc.). No eggs, no omelets. If what you want is to keep adding 'til you get the count... like (for C3) a Mundorf cap of 82uF+2.70uF=84.70uF or another ex.
33uF+33uF+15uF+1.50uF+1.50uF+0.68uF=84.68uF:cracku p:

[giralfino]

I was also suggesting a 82 + 2.7 uF caps, but then I noticed that 5% tolerance over a 82uF cap is more than 4uF, so depending on the real value of the 82uF cap, in order to achieve the correct 84.7uF value you could need a cap in the range of 0-7uF. So IMHO you could use a single 82uF cap or have it measured in order to add the correct value to reach 84.7uF.
Ralf

[mjf]

hello.
do you know the impedance of your tweeter?
are you shure this are the correct values of c3? because in a ordinary butterworth network c3 is around three times c2......
greetings.............

[sviru]

Yes all the values are correct. They seem a litte to big. 84uf is quite a lot. I have never seen such big value Caps in crossovers.

The impedance of the speakers is about 4ohm.

What I wanted to achive is to eliminate the 84uf and make it smaller around 20uF - so I could buy something more refined - Mcap / Mundorf etc.

[ashok]

Use film caps meant for motor use. Rated here for 440 volts ac.
I got some with 45uF/440V. Pretty large though much cheaper than botique caps and they sound good too. You get various values. Check the range and pick up what you need. Here they are rated 5% tol.
You will need to measure the inductor. Wind one with an air core. Use the free "inductor" software that Calsod have on their web page. You can choose the wire size and core dimension and get the number of turns required plus dc resistance etc.
Cheers.

[5th element]

It seems like an odd value, but if you sim with the crossover and just fiddle around with reasonable values for the inductor. Then you'll see that it's quite reasonable in its function. There's certainly nothing odd with how the crossover functions using a cap of that size. It basically allows you to finely shape the response around the xover region and alters the steepness of the initial roll off.

I wouldn't recommend altering this value.

[BlueWizard]

Judging from your circuit diagram, I think you need to recheck your values and your circuit.

The Mission M33i is a 2-way bass reflex tower with a 165mm (6.5") woofer and a 25mm (1") tweeter in a 17.7 liter cabinet with a 2.7khz acoustic 2nd order crossover. The impedance is rated at 8 ohms with a side note that it can drop to as low as 3.2 ohms.

Here is the PDF data sheet on the speaker.

http://oldsite.mission-hifi.com/pigs...r_pig_m33i.pdf

Also note in the schematic diagram provided by the original poster, there are TWO 5k ohms resistors in series with the tweeter. That would mean that the tweeter would only be getting 1/1000th of the supplied signal. That just doesn't seem right.

I suppose there are other ways of interpreting the values. 1R could mean 1 ohm, and the rest could be related to ohm tolerance and temperature code, or some such. So, 1 ohms, 5%, 'K' temperature coefficient, or similar.

For a stock 2nd order electrical crossover, the values would be about 3.6µF total. That would before a Linkwitz-Riley; a Butterworth would be about 5.2µF, and a Bessel would be about 4.2µF.

For a stock 1st oder electrical crossover, the values would be about 7.4µF.

So, the values you are giving don't seem remotely correct.

Can you confirm they are in series and not in parallel, though either way they still don't add up.

If you go to this link and scroll down, you can see a picture of the crossover (or a crossover). It does seem to have a lot of components on it, but none the less, the values we are hearing don't make sense.

http://www.mission.co.uk/model.php?m...r_id=1&print=1

I'm wondering if we aren't seeing assorted capacitors for different purposes. Some could be for baffle step correction, others could be for the Zobel network, some could be for a notch filter, and some could be for the actual crossover.

I think you need to give us a photo of the actual crossover, and a much better diagram.

But then, that's just my opinion.

Steve/bluewizard

[5th element]

The schematic provided*, produces an almost perfect electrical 2nd order butterworth rolloff at 2700 hz, into a perfect 4 ohm load. If the tweeter has a reasonably extended low end response, we've got no problems here.


* Using a 0.33mH inductor.

I assume the resistors are 1.5 ohms or something similar perhaps.

[sviru]

I have checked again. The values and schematic is fine. Caps are parallel. The resistors in series with the tweeater are 1,5Ohm - not 1.5k - but they are branded as 1R5k - it is misleading I think a litte bit.

Thanks again for help.

I think a new crossover with smaller more common values Caps (mundorf supreme etc) would be a great upgrade for thease speakers.