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hernanstafe 27th March 2007 10:27 PM

I need an active sub filter!
Ok i've asked this before several times and i got answers that were not so useful, and after reading some information about the subject, i'm getting more and more confused.

This is the thing; i built a 10" vented subwoofer cabinet, the speaker goes inside the cabinet, facing up, and the enclosure has 2 vents behind the speaker, if i'm not wrong that's a 4th order bandpass enclosure, i think.

I need an active filter, which also sums up both L and R channels. Some people on the forum reccommended me Rod Elliot's Project Nš 48, but i just read it's USELESS FOR VENTED CABINETS plus the schematic is incomplete on the page (some caps are missing).
So here i am again with nothing and wondering what should i use to filter and sum up channels. Does anyone know a working, suitable ACTIVE filter? I've been looking for one on the net for quite some time but i can't find it:(

PS: I remind it should also sum up both channels.


dswiston 27th March 2007 11:08 PM

Rod Elliots P48 is absolutely not for your vented speaker.

I'd suggest looking at P09 on Rod's site, specifically the "low" portion of the circuit.

To sum the channels, the easiest way is to simple use a resistive summer. (Just hookup the two channels together through resistors) A better way would be active mixer, look at figure 1 on P71 on Rod's site for that. You don't necessarily need the second opamp there either.

CSS/XBL 27th March 2007 11:20 PM

You might want to consider one of the Reckhorn products, either the F-1 or the B-1 (

These will be available in North America next week when my shipment arrives. These units are 120V but 220V are available from Germany.


Creative Sound Solutions

Cal Weldon 27th March 2007 11:26 PM

I picked up the Reckhorn B-1 from Bob at CSS and am very happy with the overall control it gives me. As far as summing the channels, why not consider dswiston's suggestion?

hernanstafe 27th March 2007 11:32 PM

ok thank for the replies guys, about those devices coming from germany, i'm from Argentina, i don't think we'll get them here:( Bringing them here from USA would be horribly expensive.

About Rod's projects, the mixer is fine, the Figure 1 on P71, i was wondering if that schematic is complete? or there are also some coupling caps missing?

Still looking for athe filter tho:(

dswiston 27th March 2007 11:43 PM

I don't see anything missing from Rod's mixer circuit. Looks OK to me.

CSS/XBL 27th March 2007 11:53 PM

Small packet air (up to 2 KG) is quite reasonable from Canada but I don't have any 220V versions.


hernanstafe 28th March 2007 12:01 AM

ok the mixer circuit will do then, now i have to find the filter!!

mikee55 28th March 2007 12:18 AM

Its all there
2 Attachment(s)
You just have to look.

Mostly building blocks. In the downloads section the crossover calculator is there


This program (ESP-LR12.EXE) is the actual executable file. This is version 1.2 of the program, and is just under 67k, so it is not too big. There are no setup programs or such like, so you simply have to decide where to put it, and create your own shortcut. Feel free to distribute the program to friends, since I have released it as freeware - just don't change the program in any way is all I ask.
Cheers:D mikee55

hernanstafe 28th March 2007 12:32 AM

just wondering, what are those 3 opamps in the lower part of the schematic?

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