Assembly Instructions for Speaker Crossovers with included PCBs

Discussion in 'General Topics' started by Matt Grant, Jun 11, 2018.

  1. #1 Matt Grant, Jun 11, 2018
    Last edited: Oct 7, 2020
    I thought I would throw this up here to perhaps answer some questions people may have during crossover assembly and help cut down on the number emails Erich or I receive on this topic.

    General instructions:

    Place the crossover components (and terminal blocks if applicable) on the PCB in the positions referenced on the included image making sure that the connection leads are inserted into the correct through holes. Note all of the crossover components are non direction or non-polarized so the resistors and capacitors can be placed in either direction on the board. Many of the inductors/coils have the leads on one side so they often fit only one way on the board.

    Note: Sometimes the components may not visually match ones in documented photos of the crossovers boards due to parts availability at the time of order. Therefore components may be substituted for another equivalent part by a different brand. Note the voltage ratings on capacitors may differ but performance of the finished crossover will not.

    Secure components to the PCB using adhesive to prevent rattling and to prevent excess strain on the lead wires, hot melt glue works well for this. In addition use non metallic zip ties on the larger and heavier components.

    After securing the crossover components to the board you can flip it over and solder the component leads to the solder pads. It’s often easy to leave the leads pointing straight through the PCB when soldering and trim the excess lead length with side cutters when finished. Pay special attention to the leads of the inductors/coils as only a section at the ends of these are pre-tinned (silver colored), the rest of the lead length being insulated with an enamel coating (usually gold or red colored). You can only solder to the pre-tinned end of the leads as the solder will not make an electrical connection through the enamel coating resulting in degraded or no sound. If you wish to trim those leads shorter to make the installation cleaner you must scrape the enamel coating off the trimmed ends of the leads. Scrapping sideways with a utility knife works well.

    When the components are soldered to the PCB and the leads are trimmed you can connect the wires for the respective drivers and the input to the crossover board. Usually 16 gauge wire is all that is needed for the internal connections. If you have an older style PCB these wires get soldered to the PCB itself in a similar fashion to the components leads. If you have a newer PCB these wires get attached to the terminal blocks.

    Terminal Block ID:

    IN – The input to the crossover board from the speaker cabinet binding posts/terminal cup.

    LF – Connects to the woofer driver/s

    MF (if applicable) – Connects to the midrange driver/s

    HF – Connects to the high frequency driver or tweeter.

    HF PAD (if applicable) – Terminal block for the optional high frequency padding which lowers the level of the high frequencies. Connect a small jumper wire across the two positions of this terminal block to enable. Alternatively you can wire in a switch which allows you to toggle the HF pad on and off.

    For designs using the larger terminal blocks (Philips head screws) you can insert bare wire or use ring or fork terminals on the ends of the wires. For designs that use two drivers in parallel you can insert two sets of wires (one for each driver) into each position (+ & –) of the terminal blocks, (a bare wire should fit on each side of the screw).

    For designs using the smaller terminal blocks (flat head screws) these accept only bare wire (up to 12 gauge). For designs using two woofers in parallel there will be an extra terminal block to accommodate the additional pair of wires.

    Unless noted on the reference image or crossover layout instructions any polarity reversal of the drivers is accounted for on the PCB itself and the drivers should be wired to the terminal blocks as marked.

    With the crossover assembled and the wires attached you can now mount the crossover board. Many of the newer crossover PCBs include snap in standoffs which can be popped in from the bottom side at the four corners of the crossover board. Using the included screws the crossover board can then be mounted to the inside of the loudspeaker cabinet.

    The crossover should be installed before the damping material, it is ok to place damping material over the top of the crossover but for most designs it is unnecessary to cover the crossover.


    Quick checklist, are the wires from the input and individual drivers connected to the correct terminal blocks and or correct position on those terminal blocks and attached securely? Are there any loose strands of copper wires near the terminal blocks that are touching each other and shorting out? Is the crossover board mounted to a non conductive surface such as directly to the cabinet walls, not something like foil backed damping material? Are there any cold solder joints? If you suspect a cold solder joint it does not do any harm to heat the joint back up and allow the solder to reflow.

    Common problems and solutions:

    - Intermittent or crackly sound from speaker?
    Check for cold solder joints on the PCB which may be vibrating and making intermittent electrical contact. Also check for general loose connections to the crossover and or speaker terminals.

    - No sound from woofers?
    Check for loose connections to the terminal blocks. Check for cold solder joints. Check that the solder joints to the inductors leads are not made on the insulated enamel coated section which would not allow power/sound to pass.

    - Dull sound/no sound from tweeter?
    Check for loose connections. Make sure the tweeter is connected to the correct terminal block and that the input and woofer wires are not reversed.

    - Thin sound and/or tweeter extremely bight?
    Check that the resistors are placed in the correct positions on the PCB. Check that there are no cold solder joints on the bottom of the PCB. Check that the input and tweeter wires are connected to the correct terminal blocks and not reversed.

    - No sound from speaker at all?
    If you have already checked all solder joints and electrical connections on the PCB verify you are receiving an audio signal from the amplifier by substituting in a known working speaker.
  2. Crossover Assembly Example Videos:

  3. #3 Matt Grant, Oct 7, 2020
    Last edited: Oct 7, 2020
    HT-8 Crossover assembly walk-through.
    Note this same crossover assembly process is applicable to any of the other kits.

    The parts all laid out:

    Follow Layout Diagram and test fit all components:

    Note I am using my custom adjustable PCB support tool to hold the boards up while I assemble them but you could easily use a pair of 2x4's or some quart size paint cans:

    Next with all the components properly placed you can glue them down to the board. I use regular hot melt glue for this, as it is quick easy and no mess/smell. I also add a little bit of glue to the terminal blocks to keep them from falling out when the board is flipped over to solder:

    Now with all the components glued down I add the zip ties to the larger components (which is only the inductors on this HT-8):

    With all the components properly secured it's time to flip the board over and begin soldering. At this point I straighten out all of the leads and double check all of the inductor leads to make sure they are not inserted too far.

    Now it is time to begin soldering. If your soldering iron has an adjustable temperature or wattage I often turn it up for soldering these PCBs as the leads and pads are fairly large and can pull the heat out of the tip quickly. If your iron is not adjustable be sure to give it adequate time to build up to the proper temperature and/or recover between solder joints.

    The soldering iron tip should be placed so that it touches both the lead and the solder pad on the PCB.

    I apply the solder starting directly at that point where the soldering iron tip is touching allowing the solder to start to melt and flow into the joint. As the solder melts and flows between the tip, the solder pad and the lead the greater area of contact allows better heat transfer allowing you to move the application of solder towards the opposite end of the joint. The solder will follow the heat, add it little by little until it flows out to the edges of the pad on the PCB and forms a cone shape around the lead.

    If your solder seems to bead up rather then spread out the iron is not hot enough or you are not allowing enough heat into the joint before applying the solder. Though if the tip is hot enough you should be able to apply solder immediately.

    Soldering done:

    Time to trim leads:

    At this point the crossover is assembled and ready to prepare for installation into the enclosure.

    Adding the standoffs:

    Tighten the screw such that the head beings to spread the flaps on the top of the standoffs, this will prevent the board from pulling off the standoffs. Be sure not to over tighten which can either strip the hole or break those flaps off the standoffs.

    It's easiest to attached the wires to the terminals blocks on the crossover board before mounting it in the enclosure. The terminal blocks are designed to accept up to 12 gauge stranded wire but that is overkill for all of the kits. My standard go to is 16 gauge zip cord or hook up wire. The bare wire can be inserted into the terminal blocks directly:

    For designs that use two drivers wired in parallel you can insert one wire on each side of the screw in the terminal block allowing for two pairs of wires to be attached at once:
  4. The actual application of solder part needs a bit more explanation. When the time comes I have the roll of solder in one hand and pull the end out with the other so it's sticking straight out. It should kinda looks like a 6" pokey thing, or however long you can make it and still control it.

    Pick up the iron and put the tip of the iron on the pad and wire coming through the backside and start them heating up. Then poke the conjunction of pad, component lead, and iron with the solder and start feeding it in. I like to aim at the pad and iron more than the companant wire or else solder will poke straight through the hole in the board and stick out the back side.

    If it's hot enough then the solder should melt and puddle up as quickly as you can jam the pokey bit of solder straight in. At this point a puff of smoke is heading towards your face so give it a puff of air so you can see and not breath that crap in.

    What differs between XO soldering and regular electronics soldering is the sheer amount of solder you'll be laying down. With the normal stuff you have a small pad and it takes a small bit of solder. With these XO boards you have a gigantic pad and will need to feed like 4" of solder in within a second or two. You're looking for a nice shiny solder volcano. Once you've got one pull the iron away and let the volcano cool by itself and look shiny and pretty.

    If you had to give it a puff of air with you mouth then try to miss the solder volcano because if it cools too quickly then you won't get a shiny pretty solder volcano. Quickly poking it with the tip of the iron again should get the temp back up that it will temporarily liquify again, then let it cool to be shiny.

    If you're shoving in solder and the volcano isn't building then you might be simply jamming the solder through the hole in the board. This is also something that just doesn't happen when regular electronics soldering but does with XO assembly due to the size of stuff we're dealing with and the enormous holes in the boards.

    Dwell with the iron for like 10 seconds and you could start damaging stuff, though with the scale of components we're dealing with that's less of an issue. Aiming for the iron as the backstop while solder poking will help reduce the dwell time necessary to heat stuff up quickly.

    If you have silver-bearing solder and not stuff with lead (nod your head yes) then it needs a hotter iron. I had to replace my old Radio Shack iron from days long gone with one that gets hotter.

    I don't have a dedicated soldering bench like Matt does but I do have a big blue rubber mat (from Amazon) so I can lay stuff down and work without screwing up the table I'm working on.

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