2 Drivers to enhance low freequencies?

[jjohnston]

I have a question about multiple drivers and producing low freequencies.

Lets say I have 1 Driver that has an effective range of 60hz - 300hz. at 60hz it plays -3db. If I took a 2nd driver of the same type and set a 2nd order low pass filter at 50 hz its natural roll off would be -3db at around 60hz. So if I allowed driver 1 to just play with no hpf on it, and add a 2nd driver with a lpf of 50hz would that allow the sound to go down to around 40hz at -3db? Or would it not work that well?

 

[badman]

Pretty common approach but you have to be careful with 2nd order filter- make sure you don't wind up cancelling rather than reinforcing

 

[Glowbug]

Why not use a dedicated subwoofer instead of the same midbass that's covering 60-300?

 

[chris661]

The same driver again is a .5 way system, where a 2-way speaker, with an extra mid/bass added, XO somewhere low to help with bass would be a 2.5 way system.

Go for it - you'll learn more from your own experience than from us telling you.

 

[jjohnston]

The reason I want to go this rout is for space, and making it all look hidden. I think I will just try it and see. I really am curious about learning how to get it all to work. Is there anything I should keep in mind when looking at the 2nd order x-over to avoid frequency cancellation?

Also, if I take 2 full range speakers (L & R) can I take the outputs from the LPF of both, and play both into the 1 bass speaker, or would I need some diods to keep the 2 outputs from conflicting?

I'm designing to build a very small sound bar. Thats why its all small stuff.

 

[picowallspeaker]

Only things that occurs to my mind are the terms "Isobaric" and "2nd Harmonic distortion reduction"
Bye

 

[richie00boy]

If you are connecting it passive no it won't get you any more extension.

 

[jjohnston]

OH, so it would need a seperate amp not setup as a x-over on the same channel?

 

[richie00boy]

It will need more signal than the other driver in order to achieve any extension, the only real way of doing this is to power it by another amp.

 

[Glowbug]

I'm designing to build a very small sound bar. Thats why its all small stuff.

You're running up against Hoffman's Iron Law here. Small enclosure size, efficiency, low frequency extension. Pick two

 

[jjohnston]

Oh, I got ya. Thanks for the help! Here is 1 more question. If I wanted to just use a 2 way system is there a way to take LPF out of the X-overs from the Right, Center, Left channels and put them into 1 Low Freequency driver? Without causing problems?

 

[richie00boy]

Yes an inverting summer using an op-amp will do that, then you run the appropriate filter and amp to the sub. This assumes though that your right, left and centre speakers are all identical though.

 

[picowallspeaker]

Otherwise , a driver equipped with double coil could be used . That would be the easiest way , it has always been used in Car Stereo . Since the lowest frequencies are mono ,recorded and perceived as , i think there will be no problems if run under 150 Hz.

 

[richie00boy]

How is a dual coil driver going to take a third (centre) channel? And what about handling the crossover and level matching?

 

[picowallspeaker]

Sorry , but... center channel for what ? Is this " sound bar" going to be positioned under a TV screen ? I'm in total confusion understanding #1 post , either.

 

[jjohnston]

Yes sound bar under TV. Its a 50 inch. So a speaker on the far left one in the center and one on the far right. I know they aren't "far enough apart for seperation" but I've had speakers set right to the sides of it, and its good enough for my bedroom. Or are you saying I should maybe just do a stereo... I mean if I'm not going to gain anything from buying a center speaker I may as well save my money.

I am really a noob, I'm not sure what you are saying about summer... etc. My plan was take the signal from my amp into a passive x-overs. Take the FL X-over LPF feed into the Low Driver and the X-Over from the FR LPF into that same spaker. No seperate amp... Just didn't know if that was possible.

 

[richie00boy]

Passive then you will not be able to mix the centre in and you will have to use a dual coil driver as suggested by picowallspeaker. I'm detest these setups though and would rather buy a second hand amp and run the sub active every time. Passive subs are just a mess.