Passive line level XO?

[killersoundz]

So is it possible to make a passive line level XO (before the amp)? I have an application (talkbox) I'm goofing around with, I need to protect the driver, with a 150hz 12/db octave high pass at least....

Any suggestions?

[Sydney]

Yes, with some insertion loss..
Some commercial amp have modules or can that are inserted at the amps input.
There are also passive insertion filters available.
Audio Amateur(?) had articles showing hardwiring in a HP.
The components are wired into the amp's front end.

[mintos]

http://www.parts-express.com/pe/show...number=266-462

something like this, but usually after the amp and before the speaker input.

[Sydney]

http://www.hlabs.com/products/crossover/

[fjhuerta]

http://www.hlabs.com/products/crossover/

I use them for my mains. They sorta work. The X-over frequency depends on the amp's input impedance, so you shouldn't expect accuracy out of them.

[Face]

So is it possible to make a passive line level XO (before the amp)? I have an application (talkbox) I'm goofing around with, I need to protect the driver, with a 150hz 12/db octave high pass at least....

Any suggestions?

Make your own: http://www.t-linespeakers.org/tech/f...ssiveHLxo.html

http://www.silcom.com/~aludwig/Sysde....htm#Bi_amping

[1100xxben]

Although it is possible, I think you'd be much better off going with an active crossover. You can more easily attain higher slopes with an active crossover and you won't have to worry near as much about impedance matching to your source or load.

[wg_ski]

A passive 2nd order can be made from an inductor and capacitor, and usually a resistor to "set" the amp's input impedance to a workable value around 1k or so. Just take you basic 'textbook' crossover and scale it for the impedance level. You still need large inductance - but tens of ohms of ESR in the inductor or cap are no big deal. I've done it, but I had to custom wind a ferrite core inductor with lots of iiiitty bitty wire.

In the end, active *is* easier. Don't think you have to go to the trouble and infrastructure required for op-amps. A Sallen-Key filter can be make from two single-supply emitter followers (one is for the input buffer) which can tap power from the amplifier or run off a 9 volt.

[Randy L]

I still have a set of F-Mods that I used to use. They worked well for what I was trying to achieve. There are LP and HP passive filters that you can daisy-chain to make a band-pass pre-amp crossover. They have RCA ins & outs, to it's simply a metter of plugging them in before the amp. PE sells them in a variety of filter points.

http://www.parts-express.com/wizards...rchFilter=Fmod

[Deward Hastings]

So is it possible to make a passive line level XO (before the amp)?

Yes. The issue most often is impedance matching, and everything works better if you have a high input impedance amp and a low output impedance source. Otherwise you have to tailor the filter very specifically to the electronics used, and you won't get "textbook" slopes from a simple filter circuit. It's just a lot easier with active buffers . . .

[Sydney]

I use them for my mains. They sorta work. The X-over frequency depends on the amp's input impedance, so you shouldn't expect accuracy out of them.

Yeah, the OP wanted a "Quick & Dirty" which is where these type of insertion filters are used primarily: as in mobile setups road kits for A/V crews or quick/temp studio patch-ins with 'questionable" outside signal sources.
These insertion devices are found at A/V suppliers like BH photo & Markertek and other companies used by TV studios.
Definitely less than ideal: because of the aforementioned impedance mismatch issues and insertion loss impact at low voltage levels vs typical post amplification usage of passive devices.
A fix or rig rather than a permanent solution.

[DjDisturbed]

If you want to make your on passive in-line crossovers it's really easy and works really well for what you want. Can't find a link right now for the formula's ,don't have time. But later tonight I could get it for you. I made some for my desktop speakers for a quick fix for a blown amp I replaced and I am still using them to this day.

[charlielaub]

A passive 2nd order can be made from an inductor and capacitor, and usually a resistor to "set" the amp's input impedance to a workable value around 1k or so.

I wouldn't recommend that low of an input impedance. Don't forget that this is the load that your preamp or whatever is driving your amp will see. That component may not be able to drive a load as low as 1k ohms.

-Charlie

[Sydney]

I wouldn't recommend that low of an input impedance. Don't forget that this is the load that your preamp or whatever is driving your amp will see. That component may not be able to drive a load as low as 1k ohms.

-Charlie

I wouldn't either - My amp's input impedance is around 47K

[fjhuerta]

http://www.parts-express.com/pe/show...number=266-462

something like this, but usually after the amp and before the speaker input.

That's not a passive line level XO, that's a passive speaker level XO.