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Can the commercially used mono RCA subwoofer signal output be duplicated via DIY?

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  • tyger23
    replied
    Originally posted by Spaker View Post
    [SIZE=14px]
    I can read schematics just fine and build them to their plans. I have it in my head that it isn't hard to make a "mono sum" circuit : taking a pair of stereo line level signals, and using resistors to turn those Left and Right signals into a single, mono signal that includes all the sound from both Left and Right at a lower volume. This may be total horseshit that someone told me as the correct way. He for sure used the tiny 1% film resistors in this circuit he made to "mono sum," and it seemed to work. It also seemed like the wrong thing to do to a clean audio signal.

    Spaker
    Yes - what you're asking for is relatively easy, or possibly complex. It just depends on how you want to do it. The first thing to understand is that any time you use passive components (resistors, inductors, capacitors), you will be attenuating the signal by some amount. The amount attenuated depends on the components chosen and the topology of the circuit you use. In general, I would highly recommend that you do this with relatively simple op-amp circuits, but that will involve a knowledge of power supply circuits for the op-amps themselves, and possibly dealing with a mains power supply.

    If you're comfortable dealing with a mains power supply, then it's simple to create a +/- power rail pair that avoids the use of series capacitors in the audio signal chain. If you want to use a positive DC power supply only (like a simple wall-wart), this circuit topology becomes cheaper, but slightly more complicated with regards to tradeoffs. You'd need series capacitors and you'd need to bias the audio signal to a reference point above ground. This is a very commonly done thing, but it does usually introduce a filtering/phase affect and it will likely introduce turn-on/off pops.

    I did basically what you're asking for in a DIY 2.1 amplifier board a few years back. You can read about that over here, and there's also schematics attached to the very first post. Those schematics are more complicated than you need, as you could get away with just the bottom half of the page. Those schematics enable a single DC wall wart to perform a second order low pass filter. The top half of the page enables a second order high pass filter for the stereo signal.

    http://techtalk.parts-express.com/fo...uld-you-buy-it

    Leave a comment:


  • wogg
    replied
    Originally posted by tvrgeek View Post
    Just a crossover. Mix the output of the low bass. As in tie them together!
    There re also a lot of crossovers that have that built in. Most sub plates have two RCS's and they are tied together inside,

    Sub crossovers are usually 80 to 100 Hz. Higher than that you can "localize: the sub.
    Careful with your language there. "tie them together" is over-simplified and would lead a layman to just short the R and L wires together. They need a summing circuit, even if it's just a couple series resistors before you tie them together. I'm sure you know that, but a reader may not.

    Leave a comment:


  • tvrgeek
    replied
    Just a crossover. Mix the output of the low bass. As in tie them together!
    There re also a lot of crossovers that have that built in. Most sub plates have two RCS's and they are tied together inside,

    Sub crossovers are usually 80 to 100 Hz. Higher than that you can "localize: the sub.

    Leave a comment:


  • Spaker
    replied
    [QUOTE=wogg;n1461202]Standard crossover, lots and lots of options. Like:



    Danielle and I aheb't been sjuurping I that sinetines. Or srterrt? That wiill fo it,

    Dayton DSP-LF
    Dayton DSP 408
    MiniDSP
    Behringer DCX something or other
    Various Rane and other pro audio crossover devices
    Car audio crossover unit and a 12V supply
    Build your own based on op-amps like I did for [URL=[quote] [you, alright. I jearned ot "http://woggmusic.com/indy-8-powered-2-1-system- full of one-off cabinet heads wgo ageee=ww on nothing, Also people, mind you

    Leave a comment:


  • Millstonemike
    replied
    Originally posted by Spaker View Post

    ok. But. That isn't an answer. ...
    There are simple circuits to sum the L-R into mono. Once you have that then you can use a LLPXO (Line Level Passive crossover). But you need to know the input resistance of the plate amp insure it works. For a 1st order (6 dB) low pass filter, all you need is the correct size cap after the summing resistors (a couple of uF). A 2nd order (12 dB) LLPXO is possible but much trickery to design, especially with the summing resistors ahead of the XO.

    Leave a comment:


  • ernperkins
    replied
    Sounds like you want a Passive Line Level Crossover (PLLXO). Rod Elliot has a nice write up here: https://sound-au.com/articles/pllxo.htm#outro.

    Leave a comment:


  • Steve Lee
    replied
    Try this, Spaker --> https://www.parts-express.com/rolls-...tput--245-1184


    Or this --> https://www.parts-express.com/harris...s-rca--266-258

    Leave a comment:


  • wogg
    replied
    Standard crossover, lots and lots of options. Like:

    Dayton DSP-LF
    Dayton DSP 408
    MiniDSP
    Behringer DCX something or other
    Various Rane and other pro audio crossover devices
    Car audio crossover unit and a 12V supply
    Build your own based on op-amps like I did for this

    Leave a comment:


  • Spaker
    replied
    Originally posted by billfitzmaurice View Post
    For the most part you don't have to be concerned about summing content below 100Hz or so to mono. Recording studios have been doing that since the 1980s. As for cutting sub content above 215Hz, that's much too high. 80 to 100Hz is the norm, so that the subs are not directionally locatable. Crossover duties have been handled by AV receivers with subwoofer outputs for at least 20 years, essentially ever since DVDs were introduced.
    ok. But. That isn't an answer.

    I know home theater receivers do this. The subject is asking if the same signal can be duplicated by somehow cutting everything above, YES, 215Hz. It is going to a plate amp that is adjustable up to 200Hz. If I cut everything above 100Hz, the other speakers would all have to play down to 100. No.


    I realize that recording studios typically even pan the kick drum, bass and various other gut shaking vibrations. They still come out both the left and the right speakers with all the other frequencies.. I can't see just jamming both left and right line level into a single input, or just feeding the input either Left or Right is the answer. So I again ask, is there a way to mono sum a pair of line level stereo signals? I know I have seen it, I just didn't think it looked right. I thought there must be a right way.

    So I suppose I'll attempt to find that simple mono summing circuit and run the line through a simple crossover. Or half of one, anyway. See what happens.

    Unless someone has a better idea on how to do this. Talking me out of it isn't happenning. If it bothers anybody that I am experimenting with audio gear, I beg you to look away. This is not going to be pretty.

    Leave a comment:


  • billfitzmaurice
    replied
    For the most part you don't have to be concerned about summing content below 100Hz or so to mono. Recording studios have been doing that since the 1980s. As for cutting sub content above 215Hz, that's much too high. 80 to 100Hz is the norm, so that the subs are not directionally locatable. Crossover duties have been handled by AV receivers with subwoofer outputs for at least 20 years, essentially ever since DVDs were introduced.

    Leave a comment:


  • Can the commercially used mono RCA subwoofer signal output be duplicated via DIY?

    Anybody know how to take a stereo line level signal, duplicate it, mono sum one of the pair and feed it through a crossover, cutting all frequencies above 215Hz, and leaving all the low end below 215Hz to come out that mono RCA, into a subwoofer plate amp RCA line level input?





    I like the ease of hooking up a sub with the single RCA. It's easy. I always can get a proper length. I don't feel bad about messing up an RCA cable, as I can just unspool more cable and make another one.

    I do not know what voodoo goes on inside an otherwise straightforward amplifier that allows it to have a single mono line out that has already eliminated any non-subwoofer worthy frequencies and is delivering a clean, balanced subwoofer line level signal.

    Obviously, a crossover has been emplyed somewhere. Is this where I dip into powered crossovers? I am totally in the dark as to how one would take a stereo line level signal ... and maybe..... double (?) the signal into two paths, a stereo pair to continue to the stereo amplifier, and a stereo pair that needs to turn into a mono signal, then run through a crossover(?) and back out the enclosure via an RCA jack meant for a subwoofer RCA input.

    That is how it works in my very uninformed head. The signal path anyway. What the hell I am supposed to do in order to make all that work correctly ......????? pfffft.

    Maybe I should start with numbers? I know that I am feeding a small sub at either 8" or 10" and 300watts is the RMS, but it will never get cranked. The plate amp I am going to use at this time is that Yung SD300-6 that was for sale here pretty cheap forever. It's nothing special. I would want this RCA subwoofer signal to have already cut anything above 215Hz.



    Anybody know how to take a stereo line level signal, duplicate it, mono sum one of the pair and feed it through a crossover, cutting all frequencies above 215Hz, and leaving all the low end below 215Hz to come out that mono RCA, into a subwoofer plate amp RCA line level input?


    Some stuff I know may make more sense to someone else, but things that will not help me are telling me this is a...
    Fools errand? That I should just buy a product? Just get a receiver / home theater piece of gear with an RCA subwoofer out? Just use the speaker wire level input / output? (I hate that) Do something else?


    This is part of a larger project that will distract if I drag out all those details here. Long story short, I am using multiple amplifiers to better partner with the speaker cabinets I have made and am making for a surround system. It is very unique, very cool, very loud, very clean, and very much free of distortion, and very much full of rib shaking from kick drums and face melting guitar solos.

    So just looking for a solution to this - I figure if anyone has done this DIY subwoofer amp mono RCA input stuff, they are here and can tell me about it. I have done some looking online but I am chasing the wrong rabbits down the wrong holes.


    I can read schematics just fine and build them to their plans. I have it in my head that it isn't hard to make a "mono sum" circuit : taking a pair of stereo line level signals, and using resistors to turn those Left and Right signals into a single, mono signal that includes all the sound from both Left and Right at a lower volume. This may be total horseshit that someone told me as the correct way. He for sure used the tiny 1% film resistors in this circuit he made to "mono sum," and it seemed to work. It also seemed like the wrong thing to do to a clean audio signal.

    If someone can draw a picture on a napkin and post a pic, I'll try it. I have made a couple circuits I found online, but I have to use some gear I am ok with frying before I go further with that stuff.



    Any ideas or help is greatly appreciated


    Spaker
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