Adding a tweeter to full range

[morneaux]

Originally Posted by LineArray

What is the difference between "assisting" a fullranger in the brilliance region and building a conventional 2-Way ?

I'd like to know as well. Is it more conceptual, in that the tweeter is crossed over at a higher frequency?

[planet10]

Get yourself a couple 1 uF, 0.5 uF, 4 0.1 uF caps (per side).

Start with a cap value that is probably too small (that say nominally crosses it at 20-30k (more if it is more efficient). Then keep adding caps in parallel until you have too much air, and then back it off. When you are happy get a good cap(s) to replace the experimental unit.

dave

[tinitus]

Not all tweeters have impedance rise
Some ScSp and Vifa are 4ohm, and quite flat
But true, most do rise
And besides, a series cap will also have higher impedance downwards

I would use series resistor only fore attenuation
The higher impedance results in a smaller series cap

Might be that a very small series inductor on fullrange driver would be good too, maybe
And a small cap shorted on fullrange terminals

I must be daft to suggest that here

[planet10]

Originally Posted by tinitus

Not all tweeters have impedance rise

Lars... I'm pretty sure Cal was talking about the typical impedance rise of the FR driver. There are exceptions (FF85, FE206), but they don't need tweeters. And even then they still go up a bit.

dave

[tinitus]

Originally Posted by planet10

Lars... I'm pretty sure Cal was talking about the typical impedance rise of the FR driver.

Right, Cal clearly said "FR", I missed that

But still, its the lowest impedance that dominates
But no, Cal is right, it wont be any problem
And besides, tweeter may need attenuation resistor

But its important to find the right values, to get good phase
Even if it seems simple, you may still have to experiment

[zmyrna]

I plan to add a tweeter to a FR myself. The FRs that really need HF help are the 8" ers without whizzer. I doubt a tweeter would add too much to a 4"er.
Even so it probably needs to be a supertweeter. And supertweets don't necessarily need to be time aligned. Actually they are probably best placed 20cm or so away from the FR. Top of the speaker for example.
I plan to try the configuration on Supravox DIY page (open baffle project).
It is basically a bullet tweeter crossed over very high with a single capacitor.
Similar to Fostex supertweeters pretty much.
I believe the radiation pattern is a good match in this configuration.

[dcathro]

My Seas T35 has a rising response from about 2K (92 db) to 15K (96 db).

For matching with the Supravox, I need a pretty even gentle boost form about 6K up.

Rather than pad the tweeter with a resistor, or cross it over further up, I was thinking of running an inductor paralleled with a resistor in series with the tweeter to flatten out the response at 92db from 2K up.

[tinitus]

Originally Posted by dcathro

I was thinking of running an inductor paralleled with a resistor in series with the tweeter to flatten out the response at 92db from 2K up.

Might work, but may also cause phase issues

[Raphael Shaw]

I came right with a 1uf cap in series with the tweeter.
I think what's happening is I'm using the high cross point as attenuation too.
-just getting part of the roll off slope from the tweeter.
I'll make a diagram quick to illustrate.

[planet10]

Originally Posted by Raphael Shaw

... is I'm using the high cross point as attenuation too.

That is what the technique i described is intended to do.

dave