Phase Plugs

[levon]

I own a pair of Fostex FE 206 E drivers in BR boxes (2.5 mk II from David Dicks). Since there is almost no bass I plan to built a BSC filter proposed by Martin J. King and put it between the amp and the drivers. If I understand it right this circuit attenuates mids and highs for a few db allowing the bass to become alive.
On Decware site I read that removing the dust cap and instaling a steel phase plug improves and extends the hi frequences of the driver. I would like to give it a try but dont know how to do it. Is there anybody out there who actually did it (instaled a new phase plugs) ? to explain the easiest way to do it.

levon

[Timn8ter]

I have a very small bit of experience here with the RS 40-1197. I used a small and very sharp hobby knife and very slowly cut the dust cap off. I installed a wood phase plug that I added two small screws to so the driver magnet would hold it in place.

[Timn8ter]

Phase plug installed.

[ooheadsoo]

When should you and when should you not install phase plugs? I have a pair of woofers that have a slightly cold midrange. Would a phase plug help? Or do I have no idea what I'm talking about?

[Timn8ter]

I installed mine as an attempt to clean up HF distortion.

[Flemming J P]

I installed "phase plugs" in my FE206E. I also used a sharp hobby knife and removed the dust cap.

After the dust cap had been removed I carefully remove a little of the black glue to leave stright surface on the inside.

I used a socket wrench top as described at decware, but just placing the top made me realise that I proberly never gonna get them off again. The only reason for removing them would be to test with other types of socktes.

The top and upper midrange did improve don't know about bass or if the linear xmax has change since I use them at 250hz and up.

[sreten]

Originally posted by levon
I own a pair of Fostex FE 206 E drivers in BR boxes (2.5 mk II from David Dicks). Since there is almost no bass I plan to built a BSC filter proposed by Martin J. King and put it between the amp and the drivers. If I understand it right this circuit attenuates mids and highs for a few db allowing the bass to become alive.

levon

Yes it does. But by adding a capacitor in parallel you can
use the midrange cut to effectively extend the treble by
bypassing the higher treble cut.

sreten.

[MJK]

sreten beat me to the punch, his suggestion is a good one and does extend the high end response. You might want to try using a 1, 2, or 3 uF cap in parallel with the BSC resistor. I have done this with my Lowther ML TLs and it does provide more high frequency extension. You should try all three cap values, I settled on the 2 uF value for my drivers. I would probably try that treak before altering the drivers permanently.

For the Fostex FE-206E driver in my ML TL enclosures people have been using the same Zobel as I used and for a BSC circuit a 3 mH coil and a 10 ohm resistor. For your wider enclosures the value of the inductor will be different as calculated using my write up. The resistor value will probably be about 10 ohms, part of this value is for BSC and part is to raise the Qts of the driver, if you are using a solid state amp. If you are using a tube amp, with a low damping factor, the resistor value will probably be in the 6 to 8 ohm range.

Please let me know how you make out either in a private e-mail or in this thread. I am very interested in your results and how the circuit effects the sound balance of David Dicks enclosure design.

Hope that helps,

[navin]

Originally posted by levon
I own a pair of Fostex FE 206 E drivers in BR boxes (2.5 mk II from David Dicks). Since there is almost no bass I plan to built a BSC filter proposed by Martin J. King and put it between the amp and the drivers.
levon

do you have a link to this ckt?

[Variac]

I's important to make sure that the bass increase can be accomodated by the x-max.

Although the 206 is quite well behaved for a full range, another way to look at not enough bass and treble is that here's too much upper midrange due to the resonant response peak