Fostex FE207E smashed whizzer

[OzMikeH]

Last night I watched my wife crush the whizzer on one of my drivers.

She was moving something with one foot and reached out to steady herself without looking her hand touched the whizzer than crushed it down against the phase plug.

I haven't looked closely at it yet. I was too frustrated to go near it last night.

It'll never be right again. Does anyone have any ideas for my next project?

are these worth keeping for use in some whizzerless application?
I'm tempted to recover the tweeters, phase plugs and connectors and throw the whole lot in the bin.

If something was going to happen i expected it would have been our small child or cat.

I never thought I'd say this but I'm glad I didnt buy those AER when I had the money.

[planet10]

I'd do a whizzer-ectomy and consider this an opportunity to lower the XO point (you have FT17 IIRC).

I'll dig out an XO topology i've wanted to try for sometime.

dave

[planet10]

.

[OzMikeH]

Thanks dave. Seen that one, wanted to try it too.
I had no idea where to start with the values. I have the FT17H already. We need to guesstimate where the new xo point should be and start working out some numbers.

I may as well hack the poor broken thing off then. I'm glad I didn't get around to spending a couple of days enabling it.

Talked with her about it. After attempting to explain why they won't just work fine if I try them out by explaining how the cone bends in drivers like this she switched to the "well they should have been covered if they are so fragile". I'll have to remember that one next time I break an ornament. "well you keep putting these things out on the table like that." I think she started getting it when I compared it to a bird's wing. If it breaks it can be patched up but they just don't fly quite right or quite as high ever again.

So where would a whizzerless FE207E start to roll off? I seem to remember seeing some decapitated FE206E somewhere but they had some serious cone treatments with a big star shape glued on to stiffen the inner portion up.

I've got nothing to lose so I may as well go nuts with these. Please put forward any ideas for phase plug designs, treatments or whatever.

My amp is a DIYhifi Supply Ella push-pull EL34 with the fancy bits like teflon sockets and PIO caps. It's got plenty of power and plenty of resolution.

Cabinets are Singulars in MDF. I quite like the curvy changs but they are beyond the limits of my equipment and budget at the moment.

Existing driver treatments are:
Baskets: outside of legs are bitumen and thick foil damped the stuff is designed for damping automotive body panels. Inside of legs has self adhesive synthetic felt pads 5mm thick.
Basket - magnet interface: packed and streamlined with poster putty (like blu-tak but stiffer).
Back of magnet: Covered with self adhesive synthetic felt (5mm thick)
They have several hundred hours on them and were beginning to open up nicely. Me discovering Dream Theatre certainly helped them loosen up.

[planet10]

I was thinking 7k. Series XOs need to be played with, but Andy Graddon has a spreadsheet (and articles) that should give you a good starting point.

dave

[OzMikeH]

Andy's website doesn't appear to be around any more.
I'm reading through some good stuff on the ARGOS loudspeakers site at the moment.

[planet10]

Andy's web site= ARGOS loudspeakers site

[OzMikeH]

A bit of rambling and thinking out loud (well putting it down on the screen anyway)

The FT17H is 98.5dB. (per watt per metre)
the Fe207E is approx 95dB
Ken's opinion is: " If the tweeter needs more than half it's resistance in series to pad, you need a less efficient tweeter. "
I'm going to need about 8 ohms in series with the 8 ohm tweeter to bring it down to match. I'm hoping for some errors in the factory figures plus some efficiency gains from the reduced mass of the cone.
If this philosophy is from a damping factor point of view I may be able to use a smaller series resistor with another resistor parallel to the driver to dump some power.

Time alignment is important. I'll need to make some removable supra baffles and mount the tweeter from the rear of the supra baffle. I've been keeping my eyes out for some nice oval cutting boards for months but I haven't found any big enough yet. This will allow me to move the tweeter to be in line vertically with the main driver too.

I must use a zobel to flatten the big driver's impedance out. I'll probably change cabinets eventually so an approximate correction should be good enough for now. I hope this doesn't drop the efficiency enough to stop me from using the FT17H. I imagine removing the whizzer will have little effect on the impedance curve.

Frequency... the FT17H looks like it can go down to 5k with a first order filter. I shouldn't have any problems there. The only real question is how well behaved the upper end of the FE207E will be.

[OzMikeH]

I've been looking at this series crossover calculator:
http://www.pvconsultants.com/audio/crossover/scd.htm

I need *.ZMA or *.FRD files for the FE207E and FT17H.

Does anyone have these files for these drivers?
I've searched and can't find any.

[beauistheman]

hey OzMike, how much capacitance did you have in series with those FT17hs when you were using them normally with the FE207e before it got raped? Also, where did you get the phase plugs? Cheapest place?