The Topping Tripath Triamping Trial
OK, after all the drama and flap, finally got the second set of Vifa XT25 tweeters! Had them delivered in the US, and an obliging B.O.B. carried them back home.
Had to find out how they sounded, so I dragged out my mothballed, superannuated Pioneer CS-88 boxes and promptly gutted them: disconnected the crossovers, soldered 18-gauge cables directly to midrange and woofer (ignoring the tweeters & supertweeters), threaded the twin cable pairs through the erstwhile binding-post holes, shoved the fibreglass blankets back in and screwed them shut. Then soldered cables directly to the new tweeters' tabs, and plopped them on top of the speaker boxes still in the bottom halves of the packaging they came in (heresy!).
The other ends of the speaker cables went to the Toppings: one TP-20 for tweeters, another TP-20 for midranges, TP-21 for woofers. Minijack-to-RCA ICs connected the 3 Toppings to Xonar DX analog-outs. Had to buy really cheap no-name ICs, because all the decent ones have fat metallic minijack plugs and the Xonar's line-outs nestle together closer than virgins in a harem. These cheapo ICs have moulded rubber bodies, and I had to shave them flat-sided with a pocketknife so they'd fit alongside each other.
On my PC: Foobar2000 with the foo_dsp_xover plugin. Configured the xover with 2nd-order (12db/oct) Butterworth: Lowpass @ 150, Bandpass @ 150/2000, Highpass @ 2000, delay on Low @ 10ms - those ancient 12" drivers are slow!
Only minor stumble was the Centre/Sub line-out: couldn't use it because it sums stereo input to mono output. I think the Xonar is responsible for this. So even though it's an 8-channel card, only 6 channels are usable, really. And channel mapping isn't what the foo_dsp_xover indicates, either. In my case, xover channels 1-2 mapped to xonar channels 1-2, but 3-4 went to 5-6, 5-6 to 7-8, 7-8 to 3-4. Took a while to figure out what went where using my old Sansui amp and Bose bookshelves for the testing - didn't want to slag the new tweeters by mistake
With all the crossover parameters and the gain controls on the Toppings, there's so much leeway to play around with the sound that I'm still trying to figure it all out. Not easy, when one has dodgy aural memory
. I'm playing WAVs that I ripped from my CDs with EAC. Right now, low-end lacks resolution and the imaging sucks, but I guess that's only to be expected considering how it's all just tossed together. Tweeters sitting in thermocole cradles! Speakers on wooden stools! But it's still early days with my new/old toys, so on with the tweaking...
Next I guess I should see how flat a response I can get with this setup in my little, cluttered, horribly reflective room. I have a basic non-IEC Radio Shack SPL meter, so maybe I could use that with a test-tone CD...
Then, how to best resolve the driver timing issue without having to blow more moolah on, say, thuneau's Frequency Allocator? Hmmm...
Anyway, here's what the trial looked like. Low resolution, because it's an old camera. And ignore the messiness; I usually do.
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