Sansui dipole-tweeter gimmick

[Klimon]

Hello,

After buying a pair of Sansui LM-220 speakers today (they've made some very nice speaker imo) I've been reading the brochure that explains a certain tweeter feature. The gimmick is that the backside of the tweeter isn't closed but is connected to three small 'horns' firing upward, left and right. The brochure claims two benefits:

-- Better transient response (makes sense, less pressure build-up behind membrane)

-- Better stereo image because the hornoutput cancels some of the out-of-phase information of the other speaker... which sounds like complete nonsense to me. I can accept that the tweeter has a more spacious effect due to the quasi-dipole radiation but the story Sansui gives doesn't add up; for the interested: see under LM-series; page three 'better sound image resolution' for the words and some pics to make things clear: http://www.classicsansui.net/Speakers.htm

Simon

[Geoff H]

Hi Simon.

The brochure says nothing about phase. That has more to do with the aural sense of direction than level. They do however point to time delay.

I couldn't see where the 3 horn mouths are located.

You can get a different spatial effect with the source radiating in all directions. But not just above 1500 Hz. That's OB territory.

What do they sound like compared to a "normal" tweeter?

You have to remember these brochures are produced to sell items to non technical would be buyers. The old baffle em with science trick.

Cheers,
Geoff.

[Klimon]

Hello Geoff,

The brochure says nothing about phase

They do say that the right speakers horns cancel out out-of-phase info of the other speaker and vice versa. See the trumpet example

I couldn't see where the 3 horn mouths are located

It's sketched on the forelast past

What do they sound like compared to a "normal" tweeter?

I'll get back to you, just got them yesterday late and didn't have the time to do critical listening yet.

You have to remember these brochures are produced to sell items to non technical would be buyers. The old baffle em with science trick.

Definitely true although I have quite high regards for the Sansui speakers, their engineers seemed genuinely creative (e.g. the woofers of these speakers have perforated 'throats' behind the dustcap which reduces pressure build-up in the dustcap/polepiece cavity) = not just sticking a few drivers in a cab + some sweettalk. My guess is that the tweeter-arrangement does make an audible difference but they just didn't find the right explanation for it. Will hear soon, definitely after I've swapped the 2nd order XO for a 1st order and have my sweetspot

Simon

[Geoff H]

I don't recall any of the top line Sansuis getting into Australia. Likewise the better Pioneers. Amps of course, but not the speakers. The Yamaha NS series may have overshadowed them. (I didn't like them)

One of the Sansuis that took my attention was one with a 15" bass, a 10" mid, a tweeter and super tweeter. Only saw it American magazines. Looked good on paper. If the design / build quality was in line with the G2200 and G3300 amps, they should have been good.

Geoff.

[Klimon]

I did some listening on the sansuis this afternoon, after changing the tweeter XO and upgrading components. The tweeter gimmick definitely makes a difference, albeit in a negative way; imaging is smeared & listening very fatigueing with a haze of treble overtones that comes way too late (I didn't think it would be very audible at all)... Taping up the slots made them sound like normal speakers = much better.

Fwiw: to my surprise sansui lies about the X-over point in their folder; they claim 2nd order at 2000hz; I found 1st order low-pass @ 1200hz (necessary to reduce a 6db bump at that frequency) + zobel; high-pass 2nd order at 2800hz. Their published FR however is pretty accurate with slight peak at 1200hz and same at 3000. All in all quite enjoyable pocket-money speakers and toys for tweaking.

Simon