Building 3 Way Speakers

[Raikou Tch]

I posted this over at AVS Forum and was told to ask here.

Hi, my dad and I are going to build our own speakers using drivers from Parts Express. We've picked out a few drivers for each range, and we're going to see which sound best and send the rest back. We're using a near cubic box around 1.4 ft³, and we're only going to be putting the woofer in it. No tweeter/midrange, unless it's a problem (explaining later). Here're the parts:

Tweeter
Davis Acoustics TW26T soft dome
Hi-Vi TN28 soft dome encapsulated
some metal dome tweeter, hopefully
a planar/ribbon tweeter

Midrange
Dayton metal dome
Morel MDM-55 soft dome
or
Usher 9845 soft dome

Woofer
Aurum Cantus AC250F1 10"

What we're going to do is make a sealed box for the woofer only, then make another stand-like thing for the tweeter/midrange that can be moved around a bit. We've done it on previous speakers that we modified and they sound great. I'm just wondering if it's making it sound worse than it could, and if the separate stand presents a problem. Also, if you have any comments/recommendations for the drivers, please let me know. I'd like to try a metal dome tweeter and a planar/ribbon, but all I've found are titanium ones that seem cheap, and 4 ohm aluminum domes. I don't really know what to pick in the planar range, either. 8 ohm is preferred as well unless it is possible to raise the impedance easily. Thanks in advance.

[Dennis H]

There are a couple of 3-way designs in the stickies. Unless you are set on your driver choices, I would suggest building one of them. The threads are long but the finalized designs are toward the end.

https://www.htguide.com/forum/showthread.php?t=15323

https://www.htguide.com/forum/showthread.php?t=11873

[Raikou Tch]

Yeah, we can't do that. We're set on the woofer, and between those midranges/tweeters. It has to be limited to about a 1.4 cubic ft box as well. I just need some verification on whether what we're doing is okay. We're making the box out of 3/4" MDF as well.

[ThomasW]

We've never used that woofer, so we have no testing data for it.

If you post a frequency response and impedance plot of the woofer measured in your baffle, then we can probably recommend appropriate drivers to work with it.

BTW the Vas of that woofer is 5.58 cu ft, and it's recommended for use in ported boxes. What's the sim look like for your 1.4 cu ft sealed box?

[Landroval]

BTW the Vas of that woofer is 5.58 cu ft, and it's recommended for use in ported boxes. What's the sim look like for your 1.4 cu ft sealed box?

WinISD gives Qtc = 0.78 and f3 = 43Hz, so it seems to work quite well. A 3.0 cu ft vented tuned to 20Hz is also very good, f3 = 27Hz.

[Raikou Tch]

Well the problem is, we can't have a box bigger than that. We're going to be putting it on a shelf-llike thing, and it can't really be any bigger than 1.4 cubic feet. The catalog had a list with the recommended sealed cabinet space, and that's what it said for the woofer, so I'm going by them.

[cjd]

What kind of guidance are you looking for?

1.4 is a tad on the smaller side of what a lot of us around here would recommend, given how Q changes once you include things like series impedance changes from crossover components.

Are you able to measure in-box response accurately? How have you approached previous projects? And what is your final intended goal?

Why are you set on that woofer?

While it may seem we're asking questions or being less hopeful than you had hoped, I think that's for lack of information still.

As for separating woofer cabinet from mid-tweeter, I see two issues, particularly with the mids you're looking at. First issue is one of center-to-center spacing. It needs to be less than the wavelength of shared frequencies - and a dome-mid requires a higher crossover point, maybe 800Hz. This means close. Farther apart introduces cancellation in certain positions (comb filtering). The second is that diffraction will change as you reposition the mid/tweet cabinet.

If you want a more movable top cabinet, consider a cone mid-woofer and more robust tweeter implementation, and cross to a woofer lower. Something like the Modula MT paired with top notch a 10" sub like the RS265HF, crossing maybe 200Hz and a bit steeper. Though that's just an example.

C

[ThomasW]

Chris,

He's not going to measure anything and plans on using generic crossovers.......They've chosen that woofer because that's the one they want to use....

My suggestion is to use soft domes for both the mid and tweeter. Those are the most forgiving of driver mismatches and nonoptimal crossovers.

[Dennis H]

Nevermind.....