Make your own SDA with regular speakers, is it possible?

Phasearray

Just toying around with the idea, no idea if it works. Some Receiver/Amp has Bi-amping capability and or A/B output. In theory the output to A is no different than the outpout of B right?

Suppose you have a pair of speakers connected to the primary output/A. Then you take a second set of speakers and placed them next to the first pair. But instead of hooking up channel B as one would normally do, you hook up the left channel to the right speaker and the right speaker to the left speaker. You then invert +/- terminal of the 2nd pair of speaker. The net effect should be the signal coming out of the 2nd pair of speakers is 180 degrees from the speakers from the other side of the first speaker.

Would this work?

hoosier21

yep

not as good, but it is the basic design.

I always thought that a second amp with a volumn control would get you "rather" close

heiney9

LOL- I say go for it, but they won't sound anything like SDA's. Well perhaps in strict principle they are very roughly similar. Read the SDA white paper then you'll see why it will sound nothing like SDA's.

Inneraural crosstalk is a human phenomenon and in order to properly cancel the effects it's a very exacting science and simply can not be done placing speakers side by side on an A/B switch.

But hey, experimentation is great fun!

H9

Boywonder

Interesting, with at least two basic problems with the concept:

The horizontal separation of the drivers in the SDA is very close, on all except the SRS series, the mid woofers are crammed next to each other, with their centers about 6" apart. Looking at the various Polk SDA patents (I believe all of the early SDA patents have expired at this point, and are in the public domain, allowing anyone to use the technology), the design relies on the horizontal driver spacing to be roughly the same as the width of the human head (6"-8").

The SDA's also tilt the horizontal polar response about 20 degrees inward, so no "toe-in" is required.

I suppose if you had 2 pairs of very slender and tall speakers and toed them in slightly, it may be interesting to experiment. You would also have tweeters separated horizontally and no crossover provisions for the horizontal response desired. You could however, move them front-to-back relative to each other to get some horizontal polar tilt and time alignment.

Your amp would also have to be comfortable drive two pairs simultaneously (low impedance).

heiney9

Not to mention the phase correction that take place with the x-overs. SDA's are not all that simple. Math and physics play a huge part.

Boywonder

Of course you could always try one of these modified for home use:

http://cgi.ebay.com/POLK-AUDIO-SDA-Automotive-Crossover-Matrix_W0QQitemZ300201045290QQihZ020QQcategoryZ14931QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Phasearray

I finally tried it, and I like to tell everyone that the result was ALOT better than I thought it would be. For the front i used my old cheap(and I mean cheap) Onkyo HTIB speakers connected to terminal A of the $25 Craigslist throwawy amp. Terminal B output was connected to the rear speakers of Onkyo HTIB rear speakers but the wire at the surrounds speaker ends were reversed. I placed the right surround next to the left font speaker and the left surround next to the right front speaker.

Fired up Speaker A and sure enough it sounded like cheapo Onkyo speakers. Fired up Speaker B also and the volume got dropped in 1/2. Guess the A/B amp are splitting the power. Thats ok, I simply upped the volume and all of a sudden SDA! you got to be kidding me. It worked alot better than I thought . With both A/B channel on vs only Channel A, it felt like I'm going from mono to stereo. I'm sure it doesn't have anyone near the accurate imaging and resolution of the Polks, but wow the soundstage has just blew up all over the living room(and it is pretty random what it's doing..). The difference is HUGE!

This wouldn't exactly be a listening rig,but it is fun to play around with it. If you pick up one of the rear speakers and walk around with the room with it, certain sounds just kinda nulls in and out. Feels pretty funky. Bass for some strange reason completely disappear. I suspect it's the weak amp unable to do both channels. But when I first plugged it in, voices which I thought was coming from maybe 20 degrees left of normal all of a sudden jumped to the far side of my left year. Maybe it isn't suppose to do that but it's sure fun playing with it.

Face

Let's see some pics!

ShinAce

When you are using speakers that are out of phase, bass will tend to cancel completely.

zingo

I tried to mock-up a pair of SDA-esk speakers once with a couple of extra drivers I had. They sounded different then regular speakers, but definitely not Polk SDAs. (Which was a given when I started) It is kind of fun to experiment, and it would be sweet to take after Ben some day and make a custom pair of SDAs. Post pictures, post pictures...