Testing audio crossovers

So I built some bookshelf speakers from a KIT

It comes as components and you assemble the enclosures and crossovers. Given the small enclosures, about the only way to attach the crossovers in the box is by using an expanding urethane glue like Gorilla glue... which is a great method, but me and soldering irons don't play well together and I figure its best to test them before I permanently install them.

I thought about assembling the drivers in the boxes with the crossovers just sitting inside to test, but that is actually more difficult than it seems, nor do I know if my ear could tell subtle differences. I also have a surprising lack of amplified signals. About all I could do is try to drive them with the junk sound card in my desktop that was surplus from the liquidation sale after the fall of the Roman Empire. Caesar didn't need it anymore.

Suggestions on ways to test these home-built crossovers before gluing them in?

Do you have any gear at the theater you could test them with?

Edit: Like a power amp, and a couple speaker cabinets, with whatever signal you want to use run through the mixing console?

Use a function generator app on your phone and your computer running a sound card osciliscope program.

Pete Gossett wrote: Do you have any gear at the theater you could test them with? Edit: Like a power amp, and a couple speaker cabinets, with whatever signal you want to use run through the mixing console?

Surprisingly, no. I have a Mackie 8-channel board, 6 non-functioning microphones from about 1974, and 643 miles of questionable XLR. I actually have a little more inventory than that, but nothing really functional. I found some tone generators; both online and free downloads, but I truly have no amplified signal source other than my desktop and my cell phone.

I was thinking about using the tone generator on the computer and sending it out the 1/8" jack to the input of the crossover. Using a sweep tone I should be able to measure voltage out of the high and low sides and map a curve. But holy cripes, that sounds like a time-consuming thing including sourcing and fabricating something in the hopes that my shallow theory might prove that it actually attenuates frequencies, but will it tell me if the components are good? Will it be a definitive test?

I just wrote a grant for $50k to solve the lack of sound equipment issue, but right now I really have next to nothing.

RossD wrote: Use a function generator app on your phone and your computer running a sound card osciliscope program.

Can you expand on that?

Strictly for my own horn-tooting... turned out pretty sexy.

In reply to curtis73:

Well I've got a nice Peavey 12-channel board, 2 CS-800 amps, and a pair of Peavey subs/mids/tops you can have for $400, but they're in IL.

I've heard good things about the C-Notes. Haven't heard them myself.

What you can do is connect connect everything temporarily outside of the box and verify that audio is coming out of each driver. If you want, you can also run wires through the port tube and temporarily hook up the crossover to the drivers in the box. (If it's not glued, clamping should be enough.) That way, you can hear it exactly as it will sound when everything is fully together.

As far as mounting the crossovers, I'd recommend putting it all together on a thin board (eg 1/8") and mounting it in the box with industrial strength velcro.

If you need a cheap amp, you can pick up a mini-amp from Parts-Express (https://www.parts-express.com/lepai-lp-2020ti-digital-hi-fi-audio-mini-amplifier-with-power-supply--310-3000) for $25. Then you can pipe your cellphone or computer audio to them.

You'll need to get the 3.5mm stereo plug out of your phone to some interface that you can send to the crossover. Like an old patch cable that you split apart and solder alligator clips to the ends. Then use the other end of that cable with more alligator clips and connect that to the output. Plug that into your microphone/In on your sound card. Download a function generator app and a sound oscilloscope program. Then start changing the frequency and watch the output on the computer.

I make this sound easy because, I've never done this before either. But it should be possible!

Yah, buy one of those cheapo Lepai amps from Parts Express already! No excuse for not having a couple laying around the house.

Easy for me to say. I've got no fewer than six working stereo systems in the house (and garages) and a bunch of other guitar amps and miscellaneous audio components.

Nice job on the C-Notes! I wonder how they compare to the Overnight Sensations I built for my son a couple years back. If they're anywhere near as good, they'll be awesome!

Gratuitous pic of the overnight sensations. They sound even better than they look!

Nice work on the Overnights! The woodgrain looks sweet.

I hit mine with a couple coats of spray poly (mostly to seal up the endgrain so it didn't absorb so much), then scuffed them up and used Rustoleum spray on bedliner. That stuff would be awful as actual bedliner, but it is a nice resilient coating. I had used it in the bilge of my last boat and was pleased, but I think I'd be disappointed if I put it in a truck bed. I would call it a matte finish, but nowhere near as rough as actual bedliner.

The Overnights and the C-notes compare pretty well. I think the main difference is the ply cabinets instead of MDF and different drivers, but they both have awesome reviews. Woofers on the Overnights look like they might be shielded? That would be a nice addition for studio and home theater. I'm not picky on cabinet material for something this small. If the panel resonance were outside the passband (like subs) that's where I really prefer MDF.

RossD wrote: You'll need to get the 3.5mm stereo plug out of your phone to some interface that you can send to the crossover. Like an old patch cable that you split apart and solder alligator clips to the ends. Then use the other end of that cable with more alligator clips and connect that to the output. Plug that into your microphone/In on your sound card. Download a function generator app and a sound oscilloscope program. Then start changing the frequency and watch the output on the computer. I make this sound easy because, I've never done this before either. But it should be possible!

Will the audio jack from my phone create enough oomph for a functional test of frequency attenuation of the crossovers? In the absence of an amp I'm kinda stuck unless I want to dump more money into what will basically be a one-time use item.

I plan on making a "soldering" station in the shop for things like repairing XLR and DMX, but I have a feeling that having a fully functional audio repair station is something that A) I will use once every 5 years and B) is a bit beyond my skill and ability.

In reply to curtis73:

Thanks! I had to check, but yes, they are shielded. They're the HiVi 4" midbass drivers here: https://www.parts-express.com/hivi-b4n-4-aluminum-midbass-round-frame--297-429

What amazes me is just how nice the low end sounds in these ported enclosures. It reaches impressively deep for such a small system.

Finish, IIRC, is Minwax Colonial Maple with a couple coats of gloss polyurethane. Being in my son's room, I wanted the finish to be durable above all else. Given that I rushed it a little, I was very happy with how the finish turned out.

Back on the matter of the crossovers, there really isn't much to go wrong. Just remember to make a good physical connection before soldering. I used some old Plexiglass I had laying around.

scardeal wrote: As far as mounting the crossovers, I'd recommend putting it all together on a thin board (eg 1/8") and mounting it in the box with industrial strength velcro.

Thanks for the amp recommendation. Might have to snag one.

When I ordered everything I got some breadboards to assemble the crossovers. I realized I only ordered two, so for the two pairs of speakers I shorted myself. I went ahead and assembled two of them naked and put the other two together on the boards... only to then find another pair of breadboards in the box. Oops. Oh well.

I was going to screw the breadboards down but there is no way to really get a driver or screwdriver in there with my fat hands.

curtis73 wrote: I went ahead and assembled two of them naked...

I fail to see how your state of undress has anything to do with building crossovers.
Just be careful not to get hot solder on your hootus.

1988RedT2 wrote:

curtis73 wrote: I went ahead and assembled two of them naked...

I fail to see how your state of undress has anything to do with building crossovers. Just be careful not to get hot solder on your hootus.

Haaaaa. Phrasing, Curtis. Phrasing.

Picked up an amp off CL yesterday. Its a used Sony A/V surround receiver, so limited use for the theater except for maybe lobby music, but I am closing on my house in a week and it won't hurt to have tunes there.

So now I guess I'll make up a 1/8" to RCA cord and use a tone generator through my phone to test these puppies.

The phone wouldn't be able to drive the speakers attached to the xover but should be able to make it do it's thing as a stand alone.

Here's how my crossovers turned out.

In reply to curtis73:

Mine always look ghetto compared to that.

scardeal wrote: In reply to curtis73: Mine always look ghetto compared to that.

I had a tutor. Big help.