View Full Version : question about bipolar caps in crossovers


gogofast
11-21-2009, 04:28 PM
i'm scavenging parts for pioneer hpm crossover recap around the house, and while looking at the parts list, i see one of the caps rated as "63vBP". i assumed that "BP" is for bipolar?

what purpose does this particular cap have in this crossover? it's placed before a series of 10w resistors and a transformer going to a super tweeter.

Tripqzon
11-21-2009, 05:18 PM
Yes it is a bipolar capacitor. It blocks frequencies below a certain frequency based on the design parameters. In this case it would be ~12kHz if you are talking about the HPM-100's or 60's and ~10kHz if you're talking about the HPM-40's..

gogofast
11-21-2009, 05:26 PM
i'm doing hpm-150.
so, is it critical to use bipolar instead of non-electrolytic?

Urizen
11-21-2009, 05:27 PM
i'm doing hpm-150.
so, is it critical to use bipolar instead of non-electrolytic?

Those terms have nothing to do with each other. Bi-polar (non-polarized) means that the current can flow both ways across the capacitor, as it should in speaker crossovers, as they are AC devices.

I'd avoid electrolytic caps in crossovers except for perhaps the bass sections, or if there are space constraints. YMMV.

gogofast
11-21-2009, 05:31 PM
i guess my question really was, what does this bipolar cap do that other types of caps can't do in its place? just curious. and i see that you're saying the current flows both ways.

mashaffer
11-21-2009, 07:15 PM
It won't blow up like regular polarized electrolytic or tantalum caps will. Any non-polarized cap would work which includes the better quality caps like film caps (polyester etc).

mike

Zilch
11-21-2009, 08:20 PM
i guess my question really was, what does this bipolar cap do that other types of caps can't do in its place?The little bipolar electrolytic can in there?

Sound nasty (if you can hear the supertweeter) and go out of spec sooner if it hasn't already.... :)

Colette
11-21-2009, 08:39 PM
Those terms have nothing to do with each other. Bi-polar (non-polarized) means that the current can flow both ways across the capacitor, as it should in speaker crossovers, as they are AC devices.

I'd avoid electrolytic caps in crossovers except for perhaps the bass sections, or if there are space constraints. YMMV.

But where do you get caps over a few MF that are not E-Caps?
Thank You

luvvinvinyl
11-21-2009, 08:49 PM
Audience, MCM ELectronics, Parts Connexxion, to name three AK advertisers.

There are, of course, others. Google is your friend.

TerryO
11-21-2009, 09:23 PM
You might also check Apexjr as they often have caps that go for very little.

Personally, I'm not adverse to using NP Electrolytic caps myself, although I do use small value Polly caps as a bypass. I like to experiment and having lots of cheap caps is handy. In absolute terms they're not as good as more exotic types, but if they are well matched and not too old it can be very hard to actually hear the difference. Over time however, the values of electrolytic caps can drift quite a bit and they definately won't last forever...but what does?

Best Regards,
TerryO

karlo
11-21-2009, 10:51 PM
i think you'll find most film caps over 20mfd are expensive and can be kinda' on the
large side . lots of folks snub electrolytics , and they've become looked down upon
by many for the simple fact that they're not as trendy as polypropylene.

i cringe when i hear tales of people replacing bad electrolyte caps in old radio shack
and jensen speakers with $20-30 polypropylene versions , and marvel at what an
improvement the $$ caps made . of course they did....the caps were 30 years old,
and they were bad .
i'll bet a $1.50 bp electrolyte cap would've improved it all the same .

now, in a pair of sonus faber, ads ,snell or mission speakers , i could see where replacing
old electros w/ poly might be an advantage , but those speakers cost over $1000 when new,
and are articulate enough to hear the difference .

every snell , mission, ads speaker i've been inside had polyester
caps in the crossover . does that mean they all sounded like shit?

gogofast
11-22-2009, 12:39 AM
The little bipolar electrolytic can in there?

Sound nasty (if you can hear the supertweeter) and go out of spec sooner if it hasn't already.... :)

so using film cap of close enough value is the thing to do here, i guess.

Isotonic
11-22-2009, 12:54 AM
There is no reason to use any electrolytic cap except for the high value ones. Film caps can be very affordable and are superior to electrolytics in sonic clarity and in accuracy over it's lifespan. The Bipolar caps you speak of are two polarized electrolytic caps tied together in one cap.

If you are on a budget, you can find very nice caps for a few dollars on ebay. The vendors that advertise here are reputable, but it's your money. Spend it where you like. I recently found very inexpensive Panasonic metallized polypropylene caps on Digikey and I thought they sounded very nice. I found some very nice polystyrene and foil caps on ebay for about the same price and they are probably the same cap as the Rel RTX or RT. I am pretty excited about trying those out. There is lot's of good information out there regarding what you need and you don't have to spend a fortune.

I think crossover caps are fun.

Zilch
11-22-2009, 01:01 AM
every snell , mission, ads speaker i've been inside had polyester
caps in the crossover . does that mean they all sounded like whit?No, but they'd likely benefit from a Theta 0.01uF bypass cap. :)

so using film cap of close enough value is the thing to do here, i guess.Yup.

You'll see in the HPM-100 recapping thread how I combined two film caps to match the value.... :yes:

http://www.audiokarma.org/forums/showthread.php?p=1862746#post1862746

Isotonic
11-22-2009, 10:17 AM
What do Theta bypass caps bring to the table Zilch?

TerryO
11-23-2009, 03:06 PM
What do Theta bypass caps bring to the table Zilch?

I'm not Zilch, but...

They make inexpensive Panasonic metallized polypropylene caps on Digikey sound like expensive Panasonic metallized polypropylene caps!

BTW, we've done comparisons on crossovers (identical pairs of speakers and crossovers) using electrolytic caps with dayton polly bypass caps on one pair and the same crossover typography using dayton caps with the same value bypass caps on the other pair. Nobody could reliably identify which was which and when asked for a preference it was pretty much split. It shouldn't have anything to do with it, but both pairs were using 2nd order series crossovers.

Best Regards,
TerryO