Zaph ZBM4 Crossover Placement

[samtny]

Hi all,

Building Zaph's ZBM4's, my first speaker project; where in heck do I put the crossover?

I was assuming inside the enclosure, but now I'm looking at Zaph's pix and there's acoustic foam on all the inner surfaces, top/bottom/back/sides, with apparently no surface to glue in my crossover board (which is a highly advanced 4"x 5" piece of cardboard).

Do I just kinda lay the xover on the bottom on top of the foam? Glue it to the foam?

Any thoughts?

Thanks much!

Sam T

[Zaph]

I do something similar to this on many projects: I mount my components on a somewhat rigid board, usually 1/4" pegboard or 3/8" MDF. I make one dimension just the right size to be able to wedge the board between the left and right walls, and the foam keeps it in place.

The great thing about this method is that it's held firmly, does not vibrate, but is still removable if I need it out.

Sometimes I'll position a crossover board on one side near the back if there's enough room, then I'll use a bracing dowel right in the middle of the board wedged into the other to keep it in place. Once again, it's held firmly, does not rattle but is removeable. With the ZBM4 I think the bottom is your only option however.

None of that really works for you if you just used cardboard however.

I'd post a picture of my crossover boards, but if I recall, I paralleled some caps and resistors to reach values, and I don't want to confuse anyone with a bunch of extra components.

[sdclc126]

Many people keep their crossovers completely separate from the cabinets, especially for small speakers such as this. The XOs can be anywhere you want, hidden and out of the way, even in their own protective enclosures if you wish - you then run the two sets of driver cables directly into the speaker cab. This actually can look kind of cool since you'll then need to use two sets of binding posts (but see my alternate technique below).

I mounted my XOs on the rear panels of my cabs (wood screws or even velcro work fine); I extended the top and side panels with lengths of wood 2" wide, as they were pre-built cabs - this pretty much hides the XOs but they remain accessible should you wish to modify them or show off your handywork to your friends.

If you build your cabinets from scratch you can recess the rear panel by using deeper side panels.

With this layout you don't need binding posts going into the filters - the speaker cables can be soldered directly to the inputs (or use quick disconnects, etc.), and the leads going to the drivers can then go to binding posts if you wish, or, in my case, directly through holes drilled in the panel - they are the same or slightly smaller diameter than the cables, so there is a tight seal with no air leakage.

[samtny]

Originally posted by Zaph
Sometimes I'll position a crossover board on one side near the back if there's enough room, then I'll use a bracing dowel right in the middle of the board wedged into the other to keep it in place. Once again, it's held firmly, does not rattle but is removeable. With the ZBM4 I think the bottom is your only option however.

None of that really works for you if you just used cardboard however.

Thanks, Zaph; if I read you right, it is acceptable to mount the ZBM4 crossover on the bottom of the cabinet, on top of the foam insulation, so long as the xover is properly "braced" in place. I think I can manage this if I double/triple up on the cardboard, which is actually fairly sturdy.

I hadn't thought of "bracing" it, I was all about the nailing or the gluing, so thanks for the suggestion. Also I had thought the components might come too close to the woofer driver, but your comments have cleared that up.

External mounting is not an option at this time.

[samtny]

Hmm, just measured my 2 resistors with a multimeter (now they are soldered in place); I'm getting 4.5ohm and 5.5ohm instead of 4.0 and 5.0!

Is this going to be a problem?

For the non-Zaph's out there, the original circuit looks like this;



I guess the different resistance on L4, L5 would affect the "tweeter L-pad", but is the .5 ohm difference anything to really worry about?

Could this be why my tweeters sound a little extra shrill when testing?

[T3sn4f2]

Zaph. If I want to use these as near field like computer speakers between a monitor about a foot or 2 from the wall, do I need to do any modifications to the default crossover?

Thanks,

Frank

[sreten]

Originally posted by T3sn4f2
Zaph. If I want to use these as near field like computer speakers between a monitor about a foot or 2 from the wall, do I need to do any modifications to the default crossover?
Thanks,
Frank

/sreten.

[DcibeL]

Originally posted by samtny
Hmm, just measured my 2 resistors with a multimeter (now they are soldered in place); I'm getting 4.5ohm and 5.5ohm instead of 4.0 and 5.0! Is this going to be a problem?

Some multimeters aren't very accurate at measuring very low resistances. Take your meter leads and short them together. What is the resistance measurement?

[T3sn4f2]

Originally posted by sreten




/sreten.

So treat it the same way if they are stand mounted and closer to the walls?

[sreten]

Originally posted by T3sn4f2

So treat it the same way if they are stand mounted and closer to the walls?

Baffle step compensation options
The default crossover is designed for stand mounting. If the system will be placed closer to boundaries, a reduced baffle step compensation crossover may be used. This may help reduce a boominess problem if it shows up. I recommend construction of the default crossover first. Then if needed later, the primary woofer inductor could be unwound to the lower value, and a L-pad adjustment will bring the tweeter level up to match.

/sreten.