I won a pair of 4.5" Wavecor WF118WA05-4 at MWAF this summer, and picked up a pair of (JR's so-called BeastMode) DX25BG60-04 for less than $10 each- <$20 in drivers out of pocket. It is time for another capable 4" 2-way.
Being what they are as quite durable wide-bandwidth devices, I set out on a sim for broad overlap, and easy treatment. The measured T/S yielded a 4 ltr vented box tuned to 57 for an F3 of 57 Hz. Not bad considering it's a 4.5" 'woofer' as Wavecor calls it. It has a progressive spider, and supposedly well damped Qms to allow it to work harder than a lot of other 4" woofers. I still think a switchable 500uF NPE might find its way in to the xovers for safety's sake. Then I tried to mock up internals by drawing it out. That is internally, HWD, 8" x 4" x 8". Talk about a squeeze when I'd need 2x 1" ports at 7.75" long including flares, the double magnet tweeter, and the fairly large magnet 4.5"; and to fit them vertically is tight. Then the xover still had to go in as well!
Okay- think time...
I supposed to make the side-walls double thick, and incorporate the ports as squarish slots into the immediate left and right panels, and that still required a 90* bend in each of them to make them fit within the wall. Then I'll cut a larger through circle as the inner terminus exit. I'll use roughly the diameter of the tweeter magnet to add the volume it takes up back in to the total, and likely install xover parts into the inner side walls as well, saving volume. The outer boards will get sculpted a bit for looks.
Okay- seems doable, right? Then I went to simming it. The tweeter spec sheet upper octaves did not match the prelim measurements I took of the tweeters, so I spliced them to the spec sheet plot, extended tails, adapted to the proposed dims and placement, and came out with relatively easy LR4 results. Then I scaled back to LR2, and it was just as easy. The guessed offset looks to be about 7mm, as I'll have to overlap the tweeter with the midbass frame to get them to fit on the front together, and this shifts things to a better spot. Visual Fc hits about 2.2-2.3k as it fell on it's own with LR 2 through the xover, and tapering to 3rd above and below there.
Then I fiddled with the off-axis toggles, and found that the whole shebang lined things up even better for a listener about 2.5-5 degrees below the tweeter axis with great phase alignment from 0 to quite a ways above if I were to flip it over. So- I guess this will be an inverted TM with 8 parts; tanked second order on the woofer (3), and second order plus flanked (for and aft) L-pad and a small series L for tilt (5).
I think it looks quite viable!
Thoughts? If you'd like to comment...