Series crossover problem

[F1 FAN]

Hi all ,I recently built this crossover for use with my VIFA M17SG and SEAS H1212 tweeter. But when listening at hi levels the 6.8 ohm resistor in series with the 67uf cap gets extremely hot. I removed these two components assuming they were just for impedance eqilization. Then I noticed that the 6.8 ohm resistor conected to the tweeters pos terminal was now getting hot. Is it normal for a series xo to disipate this much power through resistors or is this crossover design flawed?It actually sounds better than the parallel network I previously used but the excessive heat conserns me.Any input on this would be much appreciated .Thanks Fred http://audioclone.free.fr/New%20BABY2000.gif

[Jennice]

I'm by no means a pro (rather the contrary), but that looks like a rather creative cross-over.

Where did you get hold of such a schematic?

I can't see the point in the RC part across the terminals, either

Jennice

[Andy G]

1. what power rating resistors are you using?
I suspect you would need at least 50w for the 6.8ohms in the RC, because its across the woofer as well and therefore equalising the impdance over the whole speaker !!

2. contact the designer !!!!

[jmateus]

I'm a great fan of the series crossovers that I've implemented over the years on all of my speakers. Especially the great sound
stage that gives to the speakers is the real advantage of
this type of crossover.

From your design I can see the over care put on this particular
one, see I'm used to simplify these crossovers just where the
big gurus recommend.

I never had resistors overheating in this type of crossover so
I'm a little puzzelled as to why either one of the resistors gets
so hot. May be the main reason is the complexity of the design
I don't know, but again there might be a reason.

I suggest you a google on the subject there are good sites you
can get ideas about this excellent topology.

One I must say is a must, a calculator and designer.

http://www.pvconsultants.com/audio/crossover/scd.htm

[Notax]

Originally posted by Andy Graddon
1. what power rating resistors are you using?
I suspect you would need at least 50w for the 6.8ohms in the RC, because its across the woofer as well and therefore equalising the impdance over the whole speaker !!

2. contact the designer !!!!

Its equalising of impendance at certain frequency, or range (800-2500 Hz). But frequency is high enough, so it is not needed resistor which can hold more than 10-15 W.
One more thing. 68 uF for equalisation is very much. It puts down impendance from 8-9 Ohm to 4-5 Ohm. About two times. Because of that, maybe is needed more powerfull resistor. I dont like that x-over. Whole.

[F1 FAN]

Thanks everyone for your responses. The resistors I am using are 15 watt. Hi Jennice ,I found this crossover on a french site called Audio clone. This design is said to be a copy of the expensive ASA Baby Monitor speaker. Hi Jmateus, thanks for the link to the series design program it looks real good.

[jmateus]

Hi Fi Fan

Just for what's worth Rod Elliott has a nice discussion of differences between series and parallel crossovers and reasons
why you prefer one to the other. Interesting stuff

http://sound.westhost.com/

[F1 FAN]

Hi jmateus, I will definitely look that up.I have previously read about Active xo's on Rod's site. His site has to be one of the very best on the net just full of excellent info.

[F1 FAN]

Another question I have for anyone knowledgeable about series xo's.What is the purpose of the .33mh coil across the tweeter? I have never seen a coil in this location on any series xo schematic.

[Andy G]

Originally posted by F1 FAN
Another question I have for anyone knowledgeable about series xo's.What is the purpose of the .33mh coil across the tweeter? I have never seen a coil in this location on any series xo schematic.

yep, got me rather puzzled too..