JBL Selenium D202Ti CD Protection Cap? . . .

Steve_Lee

I have no experience with Compression Drivers and find myself in need of a value to protect the subject units.
These will be crossed between 1.5K and 4K via DSP so there is a real possibility of blowing them while experimenting.

Spec Sheet --> https://www.parts-express.com/pedocs/specs/264-455-d202ti-spec-sheet.pdf

Can anyone offer a cap formula specific to CD's or suggest a safe value, please?

Thanks!

Steve.

Added Info --> The Subject CD is mounted in an Eminence Beta-10CX speaker which has a very shallow horn . . . which confuses the issue for me after reading up on the subject . . .

jhollander

My experience says they are pretty durable, but I've not burned one up to know for sure. There are replacement domes that are simple to replace, which I've done due to contamination in the gap.

My thought are these have a thermal limit more than a x-o limit. I ran my tests without any caps and it was loud. I've got a few more CD projects on deck and I'm not planning any protection caps.

dcibel

At 106dB sensitivity I imagine you'll blow your ears out by the time to put 1W to the tweeter. In other words, it'll be fine.. But if you must know..

Option 1 - place some cap 25-50uF in series and you get what you get.

Option 2 - evaluate impact of series capacitor.

Step 1 -trace the impedance response from the datasheet, or ideally measure impedance with the driver mounted to your horn of choice.

Step 2 - Load impedance into some simulation software like VituixCAD.

Step 3 - place capacitor in series with driver and observe filter transfer function , adjust cap as you see fit.

Steve_Lee

I'm coming up with about 17.4 uF if crossing 1st order BW @ 1.3KHz with a CD Z of 7.5 Ohms at ~1.3KHz inside a Plain-Wave-Tube.

Using this calculator --> https://goodcalculators.com/crossover-calculator/

Good enough? (I have these caps on hand . . .)

Steve_Lee

I am getting this CD crossing over as low as 800 Hz without problems at around 85~90 db and it sounds good using DSP and discrete amps.

Billet

Are you still using the D202ti drivers? How do you like them?

Steve_Lee

Hi Billet,
Yes still using them with the Eminence CX10's and love them - took a little DSP effort with a mic to get rid of the rasp in them though - no fault of the driver - Once you get them flattened (either DSP or passive) and broken-in they sound very clean & detailed for me.

I did not use a blocking filter cap on them and still have not - they don't need them like a ribbon does.