I cut 10 pieces of white masonite to build crossovers. Here is my draft layout for one channel. Suggestions (and double check) would be more than welcome.
An externally hosted image should be here but it was not working when we last tested it.
I did some testing of Gorilla glue on film coated ply today and a T joint was surprisingly strong. All I did for prep was wet the exposed wood with water, scuff the film and wipe it down with IPA. I am very confident that it will be fine for the dado joints in my build.
Did you resolve the cause of the 10mm gap?
How much space do you need for the XO? Maybe now you're at it you could use real pcb's. Those cost next to nothing from Seeed, Itead or Elecrow and would be way more professional and handy than a piece of wood 😉
Yes, after chipping all the chemical metal off and sanding back the epoxy there was a 3mm gap when dry fit. I think I used way to much chemical metal which set before I clamped it and I also think the rubber baffle on the driver didn't compress as much as I thought it might.
I've routed out behind the magnets and glued with pl premium. I'm away until Wednesday so hopefully I'll come back to a good bond.
The piece of wood you see is 110 x 70 mm. I could get it down to 100x50 with a PCB. The biggest issues at this point are lead time and cost. I am quite sure these will work fine.
Nothing magical about a PCB. I have seen many a good loudspeaker with a point-to-point wired crossover on a piece of wood. 🙂
Forgot to say earlier, those flat packs are awesome. Would have saved me a couple of months of messing about, although it has been quite good fun.
I thought we weren't supposed to use wire wound resistors for the x-overs?
Carbon film was preferred?
Carbon film was preferred?
@Duffy. Just that it looks more professional and is easier to use. Performance wise it won't matter much indeed.
@Steve. That's with the piezo tweeters. Wirewound resistors have quite a bit of parasitic inductance, which acts as a lowpass filter. Not something you want when you use it as a highpass filter on your piezos. For this application it's fine.
@Steve. That's with the piezo tweeters. Wirewound resistors have quite a bit of parasitic inductance, which acts as a lowpass filter. Not something you want when you use it as a highpass filter on your piezos. For this application it's fine.
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Saturnus specified Carbon film for piezo tweeters. In this application (PHT-407 tweeters) I don't thin a few uH will matter but let's do the math. 🙂
The inductance is between 10 and 20uH (I could not measure directly so I could be off a bit). If we assume I am off by a factor of 2 (40uH) the -3dB point is in the 80kHz region. I don't think that is meaningful in the scheme of things.
cool, I didn't realize that and bought the carbon film for the PHT407s...
glad I didn't screw it up.
and I bought 20g inductors not 18g like you have, I hope that's okay too?
glad I didn't screw it up.
and I bought 20g inductors not 18g like you have, I hope that's okay too?
Actually. It's carbon composition or metal film but not carbon film or wire wound with piezos.
Anyway, I normally recommend metal film with the PHT407Ns there's really not going to be much difference if it's wire wound, carbon film or metal film with the PHT407Ns. I wouldn't recommend carbon composition with those though.
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Also, special winding approaches can be used to reduce inductance. I don't know if these appraches are employed or not.
Wirewound resistor » Resistor Guide
Wirewound resistor » Resistor Guide
sorry guys. metal film. that's what I bought. such a huge thread, they are a lot smaller, so at least they'll save some space.
Any suggestions on where 4 ohm 5w metal film resistors can be found without giving up my first born son? Mouser, Digikey, and Parts Express all top out 1/2 watt
but digikey has 2 ohm in 3W. So, I figured I would just put two of them in series and get 4ohm with the required power handling.
Actually, I bought several different values (2ohm,4.3 ohm, 6.2 ohm, 8.2 ohm) and was going to hook them up with a dip switch so I could dial in the attenuation--Saturnus had mentioned that some experimentation here would dial in the tweeter in for the type of music you liked.
They were $0.61/each at digikey.
Actually, I bought several different values (2ohm,4.3 ohm, 6.2 ohm, 8.2 ohm) and was going to hook them up with a dip switch so I could dial in the attenuation--Saturnus had mentioned that some experimentation here would dial in the tweeter in for the type of music you liked.
They were $0.61/each at digikey.
Yeah, then I'd want a PCB to make the soldering easier. 🙂
In all seriousness, in this application the Dayton Audio resistors will be just fine.
I did some measurements and these resistors are 0.003 to 0.004 mH. That is a factor of 10 smaller than I used in my calculations below. Fc moves to 1 MHz
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