Similarities and Differences: ZDT 3.5/Syphons

[sdclc126]

I think can be fun and educational to compare/contrast similar designs, especially when it comes to the crossover. John Krutke's ZDT 3.5

http://www.partsexpress.com/projects...?project=zdt35

and Darren Kuzma's Syphons

http://www.partsexpress.com/projects...ect=TheSyphons

are "similar" in that they are multi-way and use the same woofer and midrange; they essentially part ways after that. Just for kicks I'm interested to see opinions on the relative merits of the crossover designs employed in these speakers.

Thanks!

[Dave Bullet]

If woofer / mid crossover is 2nd order acoustic in the Syphons, I'm surprised polarity is not inverted between the woofers and mid.

David.

[sreten]

Hi,

Much is made of 2nd order acoustic slopes in the Siphon, but as
stated midrange polarity does not support this or is a mistake.

The Devil is in the details. The ZDT3.5 has a 1st order high pass to the
mid and a wide 2nd order L/R roll off. The Siphons have a 2nd order
highpass with a highish Q - hard to see where the 2nd order slope
comes from, and to boot Zaphs excursion modelling for the RS52
indicates there may be some power handling issues if indeed the
rolloff is 2nd order acoustic at 550Hz.

IMO the Siphon has "quasi" filters - meeting the target near the c/o
points whilst the ZDT3.5 meets them further way from the c/o point.

Hard to judge the Siphon without more curves ...
Zaphs RS52 suppression is more elegant / cheaper.

The two designs are not strictly comaparable due to the inclusion
and requirements of a low cost tweeter in the ZDT3.5 leading to
4th order L/R for mid/treble, though one could note this has been
achieved with less components than the Siphon, also mentioned
in the Siphon write up.

Possibly this indicates that 4th order acoustic mid/treble is the easiest
/ most cost effective for the RS52, consequently then the RS28A is not
the most cost effective choice as a combination of drivers.
FWIW I would baulk at the tweeter costing more than the midrange.
(unless the mid is used as a "filler" driver.)


/sreten.

[sdclc126]

"...RS28A is not the most cost effective choice as a combination of drivers. FWIW I would baulk at the tweeter costing more than the midrange. (unless the mid is used as a "filler" driver.)"

Yes - RS28A is overkill (and under utilized) in a 3-way w/ 7" woofers - should ditch the RS52 altogether & go 2.5-way. Zaph's design is more practical/better value where the tweeter is more the "filler" driver.

RS28A & others in its class simply don't need midranges to work well with midwoofers. If you're going with big woofers then yes make it a true 3-way, but then maybe use a larger cone driver for mid - see many of Troels' designs.

I recall classic 3-ways - a la a/d/s, Yamaha etc. from 1970s & up used 2" dome mids w/ 8", 10" & 12" woofers, but still a 1" dome tweet, although I doubt they could reach down where modern tweeters do - many of these were crossed as high as 6kHz.