Cheapo passive speakers breaking in
A pair of these were delivered yesterday. At first I thought their bass sucked and the top end was too 'phasy' - it was only after a while I realized I'd connected them out of phase 
Now they're wired up correctly on my TDA1521 amps, they're starting to come on-stream. I rate them as a bargain at the asking price of 228rmb (around $35).
After they've fully broken in I plan to explore what the lowest hanging fruit is by way of tweaks to the crossover....
Update1 - here's the XO, very simple 1st order. 250uH inductor on the bass (0.1ohm DCR, 6ohm bass/mid) and 1.5uF cap for the tweeter (8ohm). The NP cap for the tweeter has a rather high ESR (3ohms at 1kHz) so there might be some mileage in substituting this for a foil cap.
Plotting this arrangement on LTSpice gives a crossover frequency (if -6dB) around 7kHz which seems a little high. If we were to assume a -3dB crossover (because they're in quadrature for a 1st order) then it would require an increase of the tweeter cap by about a factor of 3. I might try a 4.7uF there to see what happens....
Now they're wired up correctly on my TDA1521 amps, they're starting to come on-stream. I rate them as a bargain at the asking price of 228rmb (around $35).
After they've fully broken in I plan to explore what the lowest hanging fruit is by way of tweaks to the crossover....
Update1 - here's the XO, very simple 1st order. 250uH inductor on the bass (0.1ohm DCR, 6ohm bass/mid) and 1.5uF cap for the tweeter (8ohm). The NP cap for the tweeter has a rather high ESR (3ohms at 1kHz) so there might be some mileage in substituting this for a foil cap.
Plotting this arrangement on LTSpice gives a crossover frequency (if -6dB) around 7kHz which seems a little high. If we were to assume a -3dB crossover (because they're in quadrature for a 1st order) then it would require an increase of the tweeter cap by about a factor of 3. I might try a 4.7uF there to see what happens....
Total Comments 6
Comments
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They look good!Posted 1st June 2014 at 03:54 PM by Alexandre
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Thanks Alex - will post up more pics when I cut them open, to show the XOs. Currently they're being worked out being driven by the TDA8932s - there's a little HF harshness but the bass is totally awesome for such small boxes - they're about 15cm * 24cm * 24cm.Posted 2nd June 2014 at 12:50 AM by abraxalito
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Courtesy of the electronics getting [I]that[/I] right, of course - strongly suggest completely hardwiring from the output of the amps to the driver coil tags, if you want to reduce HF harshness.Posted 2nd June 2014 at 02:18 AM by fas42
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There's none of the hardness I'm talking about when I drive these from TDA1521s even with a few banana plugs and sockets in the way.....Posted 2nd June 2014 at 02:42 AM by abraxalito
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Bound to have spade connectors to the drivers, I would hardwire them and completely bypass the speaker carcase connections; use a Solen or similar cap for the tweeter and give it and the inductor some breathing space from each other, make sure everything was locked down physically - SOP for me over the years.Posted 2nd June 2014 at 06:34 AM by fas42
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Cut off the spades, hard soldered the connections. Also put in a dowel as cross-bracing for the largest (side) panels. Tweeter cap now 4.7uF no idea what brand....Posted 3rd June 2014 at 03:44 AM by abraxalito
