Sanity Check- Fix fostex high end rolloff without tweeter?

[GratefulTony]

Hi all-

I have been living quite happily with a pair of metronomes I built last winter and a 41-hz amp 4 (T amp) I built shortly after...

But I have a problem.

The fostex speakers do have the magic imaging and detail that is so often cited as their primary advantage- but the Fe-167's I have been using (which are phase-plugged and enabl'd) definitely have falling output above 16-18 kHz... and to my young ears, this is a problem.

In the opinion of the all-wise forum, would it be better for me to:
A) add a tweeter/ super tweeter to the system, achieving a pseudo-full range system-

I fear that this would provide either phase distortion, non-point-source projection or other sonic problems associated with such a system. (I mainly fear sound stage degradation)

OR

B) use an active preamp stage to BOOST frequencies above 18kHz.
But, I don't know if the fostex will be able to linearly/ properly produce these signals even with the added emphasis...

If anyone has experimented in this field, or has experience with tweeter integration, I would love to hear what you have to say...


-Tony

[Cal Weldon]

Hi GT,

I would suggest adding a tweeter with a very small cap. You can experiment with placement and angles and that sort of thing including rear firing. I think asking that driver to go beyond 16K is unreasonable. Besides, there's so little music up there, the tweeter is only going to add a bit of airiness. Start with a 1 mfd cap and if that's too much overlap, go smaller. Grab some resistors while you're at to fashion an L-pad if the tweeter's too bright.

[badman]

One good option with 'fullrange' loudspeakers is to use a rearfiring tweeter to fill out the spectrum without too much by way of interference artifacts. tune it by ear, with various capacitor values (ranged between .5-4uF) and a resistive/L-pad. Sometimes Piezos are well-suited to this.

[zobsky]

And also, experiment with both 1st and 2nd order high pass crossovers on the tweeter.

You'd do well to rig up a measurement interface. It certainly can help to quantify any differences you hear. I use a mic. capsule with ARTA.

[seanzozo]

Additionally if you have BSC on the fullrange you can bypass it with a cap and get 3-6 db gain above the caps cutoff frequency.

Sean

[LineArray]

Originally posted by badman
One good option with 'fullrange' loudspeakers is to use a rearfiring tweeter to fill out the spectrum

I want to confirm strongly what was said. Polar response gets
more independent from frequency, range of good listening
positions may get larger, more "air" and subjectively more
resolution if done properly.

@tony:
... use a good tweeter, there are a lot around 20 euros.
I use a Number One DT25N e.g. to fill up the rear highs in
an OB design with FR 125 S .

Cheers

[GratefulTony]

I have followed the advice given here, and installed tweeters on the front of the cabinets, directly above the fullrange... I plan to tweak the capacitor value, as well as add series resistance to perfect the amount of treble. I must say, I have observed a big improvement in the sound of the system, though I now find "s'es" to be a bit to... ssssssss'ey... (I think this is what is referred to as syballence)

Should I be moving in the direction of series resistance to the tweeter, or a smaller cap value (I now use 2.2uf)?

[LineArray]

Hi,

maybe You have to try both, i would recommend to calculate
an L-Pad

http://www.sengpielaudio.com/calculator-Lpad.htm

and then do some iterations with different attenuations

-3 db ... -6dB ...

keep the impedance constant and try a smaller cap.

2.2 .. 1.0 .. 0.5

2.2 uF seems to be fairly large for that purpose, depends on
your particular drivers.

From theory you should not have to change polarity of the
tweeter (both drivers in phase should be ok) but i would
additionally check changing polarity of the tweeter, just to see
what happens. Some Fullrangers tend to produce large phase
shifts in the highs ...

Then:
Where does the sibilance occur?
- On Axis only ?
- Off Axis too ?

At some point there is no more right and wrong, you adjust it
to YOUR room / preferred listening position / taste. Some
Fullrangers sound more balanced in the presence region
when listening slightly off axis, the loss in brillance can now be
compensated with the tweeter.

It is Your speaker, so you decide what is right, thats it.

Kind regards

[Cal Weldon]

I agree the 2.2 is too big. Try a 1.5 or even a 1 before you try the L-pad.

[aural_junkie]

what about a small nxt speaker as it has no (conventional) phase and would, probably, not muck up the content too much due to phase mis-alignments
Or am i barking up the wrong tree with this idea?!??