After experimenting with various combos of crossover values, although the MK I cheapowave using the Pyle PDS221 compression driver sounded OK.. the high end was never really impressing me.
Note: this post continues on from cheapowave MK I postwhich documents building the cabinets etc
After reviewing the Econowave thread on Audiokarma yet again I ordered in aÂ Selenium D220Ti-8 from Parts Express in the USA. The shipping cost almost as much as the drivers themselves.. but although I could probably find a more than acceptable replacement from the P.Audio drivers from Cannon Online, I decided to go with a combination that already has shown so many good results for others, plus the hard yards on the crossover circuit has already been done by people with way more expertise than myself.
The Selenium drivers arrived, and the immediate impression is that they are bigger then the Pyles.
After screwing them in and measuring them… they are also much louder than the pyles.. on paper 7dB louder but I think a bit more. This is why the high frequency compensation techniques don’t work as well on the Pyle PDS221.. it just makes the driver too quiet to be usable with the Pioneer woofer…
After a bit of measurement and messing about with speaker workshop (and a few mis-tries, asÂ I don’t have anything calibrated so I have to measure relative to the current setup, and sometimes something changes in the measurement rig by accident and knocks everything out of whack) I went for the standard low efficiency woofer econowave crossover, but with some attenuation on the compression driver via a 22 ohm resistor in parallel, and sticking with the first order low pass crossover that I’ve found seems to work OK with the Pioneer woofer.
After being resoldered lots of times in different configs, the bits of cardboard used as the prototype crossover starting to get a bit worse for wear.. also I’m combing a few components to make up values as well, so the crossovers look a bit rough until I re-make them (but they work just fine):
The main thing is they now sound awesome.. before the best I could get was “not bad”.. but when playing “Â Emmeleia” by Dead Can Dance on the new layout and hearing little echoey bits in the corners I hadn’t hear before I knew these things were ready.
Since then I’ve just been listening to them… another good sign, but I just did a round of measurements to post up here.
- white: calculated output
- black: measured output
- pale green: Selenium output, no crossover (33 uF protection cap)
- yellow: Pioneer woofer output, no crossover
- (click to get link to bigger version)
Interestingly while I was running up the calculated output I found a small improvement I can make.. currently I have the compression driver hooked up with negative to positive as in the “standard” Econowave layout, but putting back the comp driver to have positive hooked to positive yields a slightly smoother curve at the crossover point in Speaker Workshop. Given how closely the simulated response matches the measured response I’ll change the polarity of the horns.
Just as a reference I hooked up the recently re-capped Alesis Monitor ones and measured them with the same mixer settings and measurement rig, here are the response curves superimposed – each time the mic is about 1M from the speaker and midway between the HF and LF driver.
- Black: the econowave
- White: the Alesis
Except for rebuilding the crossovers more neatly onto a bit of masonite or similar rather than the messy bits of cardboard this stage of the speakers are complete.. and they sound great.
Ideas for MK III?
Although the PioneerÂ A30GC50-52F-Q-1 sounds fine the response has quite a lot of dips and bumps in it, especially at or around the crossover point.. which has made getting the crossover right a bit fiddly. Although first I need to measure it without the effects of the room on the curve. Then perhaps I can see which 12″ woofers are available which have a smoother response curve up to about 2K which will work well in a 120L bass reflex box… but right now they sound just fine so no urgency at all….
Addendum – rebuilding the crossovers and putting them in the boxes
Now they sound just fine I rebuilt the crossovers onto some bits of MDF, and mounted them using cable ties to the bracing inside the speaker. To stop them rattling around I’ve damped the join with a big pile of hot glue, as well as all the components being stuck to the board with hot glue as well.