SEAS 27 prestige series tweeters

[crazyhub]

Hi,

I.e. 27tdfc, tbfc/g and on...Do someone know what is the x-mech (not x-max/x-linear) of these tweeters?

Thanks.

[a_tewinkel]

Why would you want to know that...?

[454Casull]

Originally Posted by a_tewinkel

Why would you want to know that...?

Guess.

[sreten]

Hi,

One would assume its around +/-2mm, but may be more + than -,
as nothing gets in the way of it going plus, whilst minus depends
on the clearance of the coil/dome join above the magnet.

rgds, sreten.

[crazyhub]

Originally Posted by a_tewinkel

Why would you want to know that...?

because I generally like to cut tweeters very low; I run power capabilities simulations using x-max. Knowing x-mech allow me to get an idea of what could be called a "safety window".

[crazyhub]

Originally Posted by sreten

Hi,

One would assume its around +/-2mm, but may be more + than -,
as nothing gets in the way of it going plus, whilst minus depends
on the clearance of the coil/dome join above the magnet.

rgds, sreten.

I agree. Allmost all Scan-Speak tweeters similar to the SEAS are rated +/- 1.6mm, I'm relatively confident SEAS tweeters are on par with SS in this field regarding size and materials used in their surrounds.

[gornir]

A better way of determing if they are capable of a low cross-over frequency is to take a look at the distortion measurements.

Here you have some links:

Mark K
Zaph|Audio

Regards

/Göran

[454Casull]

Originally Posted by gornir

A better way of determing if they are capable of a low cross-over frequency is to take a look at the distortion measurements.

Here you have some links:

Mark K
Zaph|Audio

Regards

/Göran

Unfortunately tweeters are never measured with crossovers in place, so it may be hard to extrapolate additional useful info from these tests.

[crazyhub]

Originally Posted by gornir

A better way of determing if they are capable of a low cross-over frequency is to take a look at the distortion measurements.

Here you have some links:

Mark K
Zaph|Audio

Regards

/Göran

Yes, I know these sites thanks. I also run distorsion measurements but as usually tweeters distorsions in the low-treble fr range are lower than those of mids I find it unuseful to look at them.

[sreten]

Originally Posted by 454Casull

Unfortunately tweeters are never measured with crossovers in place, so it may be hard to extrapolate additional useful info from these tests.

Hi,

Not so, quoting Zaph :

Selecting the crossover point is a fine balance of many issues. One of those issues is using the drivers within their lowest distortion working range. Like many rigid cone drivers, the cone breakup propagates as peaks in 3rd and 5th order harmonic distortion lower in frequency. We want to avoid or minimize those as much as possible. Through the design iterations, the crossover frequency started high and moved down until we get to a point where the woofer's upper end distortion doesn't make itself known. We have to factor in everything here, including tweeter low end power handling, natural response rolloffs, power response and crossover complexity among other things. It's no easy decision. In my opinion, 1750 Hz was the best for this system. A 27TDFC could easily work down to 1500 hz, but only at a certain output level. I favored 1750 over a lower crossover point that would place the power handling limit on the tweeter. Seas woofers handle power well and get very loud, so it's important to make sure the tweeter can keep up.

Xmech is a poor choice for choosing a tweeter c/o point, distortion is guaranteed,
Xmax is OK unless the driver has low down distortion issues, and some certainly do.

quoting Zaph again :

Vifa XT25 ($48) - Smoothest and most extended response curve in the group, and resulting CSD is excellent. Good tall order HD above 2kHz, but average 2nd order HD. Poor HD levels of all types below 2kHz, even considering the extended low end. It may have a 500 Hz Fs, but don't think about crossing it below 2kHz LR4 or 2.5kHz LR2. Off axis response curves available. Tested January 2006.

rgds, sreten.