Easy LPF and volume? [Archive] - Audio & Video Forums


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05-25-2011, 01:39 PM
Is there an easy way for me to create a simple low pass filter and lower the volume for a particular speaker?

Basically for my home setup I've got two small polk bookshelves, and a massive electrovoice speaker from like the 50's. It's got a 12" woofer, and a giant tweeter centered in the woofer. It's in a giant enclosure and has a variable presence knob on the back. It sounds really nice... problem is I don't know what to do with a single speaker in a 2 channel music setup. My thought was to basically turn it into a subwoofer so that I can at least use it for something. Can I just throw a cap or something on it to cut out the higher frequencies? and maybe some resistance somewhere to cut the volume down? (as of now its louder than the 2 other speakers)

harley .guy07
05-27-2011, 12:21 AM
You could throw a variable cap on it to control the volume and also put a crossover coil and if you do the math a fixed cap in series to make a crossover for this speaker that would be able to be controlled by volume first but frequency as well. The Cap,Coil circuit I am talking about is a 12 DB per octave circuit and you can find calculators online in order to find the right variable parts in order to get the desired crossover point right and also put a volume attenuator in place to control the volume, the crossover well lessen the volume a bit but probably not enough so a variable volume circuit must be in place to control the volume. It would be a Linkwitz riley crossover and add the volume attenuator before the crossover and you could get the desired results. I don't have the specs of your speaker to have the math here but you can find calculators online for these types of crossovers.

05-27-2011, 03:59 AM
Like Harley says, but with a couple of additional considerations.

You'll need to blend the Left + Right signals to feed the EV
What if the EV needs a volume boost rather than a cut relative to to your two main speakers?
One solution would be to buy subwoofer amp and retrofit it to the EV -- shouldn't be too hard given the large EV cabinet. You could get a sub amp, including crossover and level controls, from Parts Express, e.g. see here (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-802). PE has a wide range of sub amps with various prices, features and power outputs.


06-05-2011, 05:25 PM
Not sure what numbers I need to figure out how to do this... but here are the specs of the speaker http://www.mcmlv.org/Archive/HiFi/ElectroVoice12TRXB.pdf

06-06-2011, 06:53 AM
Is there any problem with disconnecting the tweeter from it's portion of the xover and just use the woofer?
I know on my Home of the Theater speaker there's a terminal block used to connect the drivers to the xover. If the driver, load for the circuit, is remove there should be no current flowing and shouldn't affect the low pass portion.

06-06-2011, 05:12 PM
I'll take a look. I know I remember this thing was very difficult to get inside of with the way it was built.