OT Sub bass

[Hungeryhippie]

hello , sorry for the unrelated question but i'm sure someone here will know. I am now the proud owner of a 12" sub + cabnet, it was being removed for the theater at work, it was going to be thrown away, so now its mine (+ it was me who had to take it off the wall above the stage about 5m up!).

I'm going to take it home and use it with my stereo so my question is I know i need a low pass filter but how do you get the stereo channels into mono (one speaker)?

Idea's on this would be greatly appreciated as i have no experience of this but 'm sure that its anyother DIY project to take on.

Failing all else i'll use it as a guitar cab.


peace to Ya

[Nasse]

I have seen projects and suggestions just taking signal for the sub bass  filter from one channel. Then the designer is in belief that most music recordings are done so that bass is mixed "mono" and is more or less same anyway at subwoofer frequecies. That method works quite well in practice.

But  maybe not always so, I have some records that certainly have bass somewhat panned or recorded "stereo", some early Beatles vinyls have bass panned hardly at another channel and drums at another.

Take just common inverting opamp mixing stage used in mixer circuits and you have what you wanted. Thats what I did. I used simple 12 dB/octave filter and believe that crossover freq was around 100 Hz, they say you can not hear the direction of freqs under 200 Hz and that is very true. In practice there might sometimes be some distortion or loud enough harmonics above that because of simple filter and it is then easy to "hear" where the subwoofer is situated.

[zeta55]

Could this be something?
http://www.sound.westhost.com/project48.htm

[Hungeryhippie]

thank you thats just what i needed.

[Mark Hammer]

Just be aware that looooonnnngggg wavelengths need big spaces to be heard.  This is why the bass coming out of little Hyundais and Acuras with 200W subwoofer systems is substantially louder (and more irritating) for those 20 metres from the car than for those inside the car.  If you live in an apartment or nondetached home, or if you have a penchant for listening to music in one part of the house while your partner watches TV in another, I would recommend including a highpass filter in there too so you can roll off the deep low end that is inaudible in your actual physical listening space.
In principle, this is no different than the "rumble" filters that would be included in phono preamps to cut out low-frequency fluctuations stemming from record warpage, motor vibrations, off-center holes in vinyl discs, and other things that generated low-frequency content that did the listener absolutely no earthly good, and just sucked supply current that could be put to better use.

I realize it may seem paradoxical to roll off the low end and restrict a subwoofer to the, say, 35-100hz zone, but thats about an octave and a half, which is actually pretty wide.

[Hungeryhippie]

Just to say thank you to zeta55 for pointing me to the site, I made the circuit at the weekend and it works great. when i get a camera again i'll have some pics to show how it came out.

[zeta55]

Glad it worked for you. I did try that one too and it worked fine for my needs at the time. I also built the guitarpreamp from the same site. I play it every day