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Crossovers on pcbs.

J

John3655

Well-Known Member
Wondering how good or bad pcbs are for crossovers. There's track thickness is it sufficient, are tag boards better, is wood better.

There's microphony, commercial pcbs have all the components glued very firmly to the pcb, but doesn't this just make everything vibrate, for some strange reason I wonder about drilling holes to allow airflow, or pressure wave flow through the board, avoiding tracks obviously. Should crossover pcbs be mounted on springs and dampers or bolted down to the cabinet!

Is the tweeter inductor better off mounted in foam.

Questions questions.
Thank you
 
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Lol could be overthinking, gslikker, thankyou for the link. I know Sonus Faber use or used a black compound partially over things.

I suppose the thing to do is mount the xover externally.
 
PCB xovers are simpler to manufacture. I'm sure there are good and bad examples out there, but the same is true of hard wired crossovers. Hardwired is all I ever knew, and is what I used for every speaker I ever built. I suspect the design and quality level of parts is more important than whether it's hardwired or PCB.

Never tried springs or foam, but I have moved x-overs to outside of the cabinet, or in their own isolated chamber
 
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I think you are over thinking it. Lots of crossovers use PCBs with just big square pads, literally they just leave as much copper on the boards are possible. Others that I have worked on, like KEF, use smaller traces, but still well within spec for the amount of current they carry.

You could add foam to the back of the PCB mounted crossover if you're worried about it flapping around inside the cabinet, but again I think it's a wasted effort.
 
leesonic said:
I think you are over thinking it. Lots of crossovers use PCBs with just big square pads, literally they just leave as much copper on the boards are possible. Others that I have worked on, like KEF, use smaller traces, but still well within spec for the amount of current they carry.

You could add foam to the back of the PCB mounted crossover if you're worried about it flapping around inside the cabinet, but again I think it's a wasted effort.
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Great idea, the crossover I've just worked on is attached to the back of the binding posts on plastic arms it slots into, it's ok when it's just electrolytes but fit films and it becomes quite heavy there's a bit of space underneath so I could see it flapping to the beat.
 
The good or bad part would be entirely up either doing it right or doing it wrong.

There are zero issues with a crossover on a properly designed pcb.

Personally I would rather see components mounted to a pcb than hot-glued to the cabinet.
 
I'd like to see crossovers mounted on the terminal board so that when you unscrew it, you get the crossover. For some reason speaker manufacturers like to screw the crossover to the rear wall of the cabinet and the only access is through a woofer hole, after you move the stuffing out of the way.
 
mrehorst said:
I'd like to see crossovers mounted on the terminal board so that when you unscrew it, you get the crossover. For some reason speaker manufacturers like to screw the crossover to the rear wall of the cabinet and the only access is through a woofer hole, after you move the stuffing out of the way.
Click to expand...

I suspect that the reason is the same one for many other items...they are made for ease of assembly with little to zero thought given to ease of repair or maintenance.
 
I have speaker crossovers that were made both point to point, and on PCB's.
Either is fine with me. I have a pair of Celestion Dittons with nice square PCB's that were easy to access and replace the caps. Some PCB's are more difficult to deal with. Like the PCB's mounted on the terminul cups in several pairs of Polk Monitor series speakers I own. You have to unsolder several thicker diameter solid core wires from the PCB to get to the back side of the PCB. And if replacing the electrolytic caps with film caps you have to get a bit creative so that the cup and PCB will fit back into the hole.
 

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I like to use E6000 Craft Industrial Strength Clear All Purpose Adhesive to glue down the components. This was suggested on several crossover posts here on AK and it really worked well. It stays 'rubbery' which I think adds some vibration protection. This should help on PCB and point to point.
 
I don't have pictures, but the crossovers in the pair of Ditton 300's I own had a 50uf cap in the crossovers. I was about resigned to using an electrolytic cap to replace the old general purpose cap when I ran across a close out sale at Partsconnexion. They had these huge polypropylene film caps dirt cheap.
The 50uf poly caps were about as big around as a condensed soup can and about half as tall.
I had to affix them to the inside bottom of the speaker cabinets and run wires to the PCB.
 
Lavane said:
I don't have pictures, but the crossovers in the pair of Ditton 300's I own had a 50uf cap in the crossovers. I was about resigned to using an electrolytic cap to replace the old general purpose cap when I ran across a close out sale at Partsconnexion. They had these huge polypropylene film caps dirt cheap.
The 50uf poly caps were about as big around as a condensed soup can and about half as tall.
I had to affix them to the inside bottom of the speaker cabinets and run wires to the PCB.
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The other option is to just get a good quality np electrolytic

I like the electronic-grade silicone for securing parts. Easy to deal with if you have to change layout and move things around (that never happens, right?)
 
I recently ordered some 220 uF PP film caps via ebay, to replace NP electrolytic input caps in my Quad ESLs. I'm really not a true believer in things like the audibility of different capacitors, but thought if the price was low enough, I'd try them and at least know they would never have to be replaced again. I was doing some research and found Jantzen PP film caps for $88 each at Parts Express. In medium to good speakers, electrolytics are primarily used in the low frequency filter driving the woofer. There were essentially no specs at the Parts Express web site so I went to the Jantzen Audio site. I took a look at their application info and found this gem:
"From a technical perspective it would generally be complete overkill to use expensive high-end capacitors for the low frequency area (bass), as the improvements in performance / sound of higher-grade capacitors, would not be audible at such low frequencies."
As far as specs go, the only specs on the 220 uF PP film cap was the voltage rating, the 5% tolerance, and something they call "loss factor" = 105. I haven't been able to figure out what that loss factor actually is. Loss tangent is usually expressed as a percentage.

Anyway, on ebay I found some new CDE 220 uF PP film caps designed for industrial use that have ESR of 1 mOhm and Ls of 40 nH for $20 each. That's close enough to the $5-8 that a NP electrolytic would cost that I decided to order them and try them out. It will be a miracle if I can fit them into the speaker's electronic enclosures- they are 85mm dia x 65 mm high. They sell for $137 each at digikey...
 
220uf film cap! I hope it isn't that size just because someone vastly oversized the bp electrolytic for less distortion.

Looking into it a bit more, a solution is to bypass the 220uf BP electrolytic with a quality film cap.
 
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RVT1K said:
I suspect that the reason is the same one for many other items...they are made for ease of assembly with little to zero thought given to ease of repair or maintenance.
Click to expand...
It seems like assembly and testing would be easier with the crossover mounted on the terminal plate/cup.

John3655 said:
220uf film cap! I hope it isn't that size just because someone vastly oversized the bp electrolytic for less distortion.

Looking into it a bit more, a solution is to bypass the 220uf BP electrolytic with a quality film cap.
Click to expand...
The electrolytic caps are about 40mm long x 18 mm dia. The film caps are always larger than similar value electrolytics used in crossovers. The electrolytics are typically 100V rated parts, which keeps their size and cost down, and the PP film caps with the same capacitance are typically 400-600V rated parts which makes them bigger than if they were also 100V parts. I suspect the film caps used in crossovers are rated for high voltages because they are also used as coupling caps in some tube circuits.
 
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