COROSSOVER MISSION M33i
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 🙂
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 🙂
Attachments
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
33uF+33uF+15uF+1.50uF+1.50uF+0.68uF=84.68uF
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
Ralf
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.............
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.............
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.
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.
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.
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.
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.
I wouldn't recommend altering this value.
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/loudspeaker_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?model_id=34&range_id=5&type_id=2§or_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
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/loudspeaker_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?model_id=34&range_id=5&type_id=2§or_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
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.
* Using a 0.33mH inductor.
I assume the resistors are 1.5 ohms or something similar perhaps.
Attachments
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.
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.
While the spec sheet on the M33i speaker says 2nd order Acoustic crossover, but the configuration of parts is for a 3rd order filter (C2, L1, C3).
The values we have from the original poster are C2 = 9.5 µF and C3 = 84.68µF.
I looked up the resistor markings and they are indeed 1.5 ohms each.
Using a 4 ohm tweeter and an 8 ohm woofer, the standard values for a 3rd order at 2,700hz are -
C2 = 9.8µF
C3 = 29.5µF
L1 = 0.18mH
If I adjust the frequency on the Crossover Calculator I am using to see what frequency give me the correct value for C3, I have to drop the frequency down to 940hz, which gives me a C3 of 84.65µF.
They may have done something with the second (C3) capacitor to alter the response curve slightly. So, it could make some limited sense. Though without a circuit simulator, I'm not clear how it would alter the filter.
Perhaps the have created a 'staged' or 'cascading' filter. Maybe as the frequency goes down, it rolls off at 12db (2nd order) between 2700hz and 940hz, then when it reaches 940, it continues to drop at 18db (3rd order)?
There are certainly those here who know way more than I do, but to my limited knowledge, this is the only way I can make sense of the values I'm seeing.
Now the only remaining question is, what is the true value of the inductor? My calculations indicate something in the range of 0.18mH. But, in this non-standard configuration, I'm not sure how much we can rely on 'standard' values.
I suppose one could measure the dimensions of the coil, count the number of vertical winding and the number of horizontal winding layers, estimate the wire gauge, and use that to make some determination of what the likely inductance is.
As far as replacing the cap, a quick look at Parts-Express.com indicates that the nearest full standard value is 82µF, and I did see crossover caps that go as high as 200µF. So, it is possible to buy them in this range.
In your case, perhaps a 47µF plus a 39µf for a total of 86µF would be close enough. Still there is a full range of values, so you can come up with some combination to get it exact.
http://www.parts-express.com/crossover-capacitor-index.cfm
http://www.parts-express.com/mfg/jantzen/jantzen.cfm#capacitors
Just a few thoughts.
Steve/bluewizard
The values we have from the original poster are C2 = 9.5 µF and C3 = 84.68µF.
I looked up the resistor markings and they are indeed 1.5 ohms each.
Using a 4 ohm tweeter and an 8 ohm woofer, the standard values for a 3rd order at 2,700hz are -
C2 = 9.8µF
C3 = 29.5µF
L1 = 0.18mH
If I adjust the frequency on the Crossover Calculator I am using to see what frequency give me the correct value for C3, I have to drop the frequency down to 940hz, which gives me a C3 of 84.65µF.
They may have done something with the second (C3) capacitor to alter the response curve slightly. So, it could make some limited sense. Though without a circuit simulator, I'm not clear how it would alter the filter.
Perhaps the have created a 'staged' or 'cascading' filter. Maybe as the frequency goes down, it rolls off at 12db (2nd order) between 2700hz and 940hz, then when it reaches 940, it continues to drop at 18db (3rd order)?
There are certainly those here who know way more than I do, but to my limited knowledge, this is the only way I can make sense of the values I'm seeing.
Now the only remaining question is, what is the true value of the inductor? My calculations indicate something in the range of 0.18mH. But, in this non-standard configuration, I'm not sure how much we can rely on 'standard' values.
I suppose one could measure the dimensions of the coil, count the number of vertical winding and the number of horizontal winding layers, estimate the wire gauge, and use that to make some determination of what the likely inductance is.
As far as replacing the cap, a quick look at Parts-Express.com indicates that the nearest full standard value is 82µF, and I did see crossover caps that go as high as 200µF. So, it is possible to buy them in this range.
In your case, perhaps a 47µF plus a 39µf for a total of 86µF would be close enough. Still there is a full range of values, so you can come up with some combination to get it exact.
http://www.parts-express.com/crossover-capacitor-index.cfm
http://www.parts-express.com/mfg/jantzen/jantzen.cfm#capacitors
Just a few thoughts.
Steve/bluewizard
sviru said:
I have to disagree here, the large value of C3 is like Bluewizard says - it delays the initial roll off towards 2nd order, the filter then tending towards 3rd order as frequency decreases. What C3 also does is alter the shape of the response around the crossover frequency and also alters the phase.
No doubt C3 at this unusually large value was and is absolutely necessary in the design, otherwise Mission would not have used it, or used a smaller cap.
Decreasing the value of C3 increases the initial rate of roll off in the tweeters high pass, but also increases the output of the tweeter smack bang where you don't want it to - the 1-3khz band. You're directly altering the range your ear is the most sensitive to, whilst at the same time changing the tweeters phase and spl in the most important area - the area of integration with the woofer.
If you don't want to buy and parallel many expensive caps to reach the large value of C3, simply buy one high quality one and replace the 20uf one in the original crossover. Although quite honestly, I bet that's what Mission have done with the 0.68uf cap anyway.
Thanks guys for help. It looks like mission made everything with purpose. I'll live it like it is and add some quality bypass caps. 😎
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