Directional bass, sub question

[Bill poster]

I think the widely held belief is that your main speakers need to reach down to 80hz flat if using one Sub, to avoid directional issues.

What if you were using 2 subs- ie below each speaker?
How high could you theoretically go with the x/o

[chrispenycate]

Surely, if your subs are in the same direction as your principal sound sources all you've got is a three (or four or whatever) way system crossing over at any frequency you choose. The problems of decent transition still exist, but any directional information from the sub is more or less right (oh, all right, if you have the kick drum panned hard to one side the lows will end up central; but back in vinyl days when I did a band with a double kick drum panned wide I had a lf mix control crossing over at 180Hz, to stop the drummer throwing the arm off the turntable, and nobody ever noticed.

The directional thing is more for when you've hidden the sub under the sofa for a vibromassage (or in the water bed, mmmm) and I suspect a lot of the problem is arrival time; it just doesn't feel right for the bass feel to get to you before the ear-collected impact.

[Bill poster]

Thanks, nice reply! In reality at what HZ does upper bass give way to midrange? 250 hz or so?

[weltersys]

Originally Posted by Bill poster

I think the widely held belief is that your main speakers need to reach down to 80hz flat if using one Sub, to avoid directional issues.

What if you were using 2 subs- ie below each speaker?
How high could you theoretically go with the x/o

Larger cones have more directionality, but are still quite wide in dispersion at 80 Hz.

A horn loaded sub may be a lot more directional at 80 Hz than a front loaded top cabinet.

It is more easy to locate the source of sound when the frequency is above 100 Hz, but there is no magic cut off frequency where suddenly location of the source "goes away".

Most "subs" are fairly large and heavy, so are put on the floor/ground.
The lower the frequency, the longer the wavelength. Longer wavelengths are less affected by audience members standing or sitting in front of them, so we can get away with a steep crossover at around 100 Hz with the subs on the ground.

Move the crossover up to around 160 Hz, and vocals will be heard from the bass speakers, if the bass is left on the ground, the vocals will sound "muddy" if people stand in front of the bass bins.

If the bass and top cabinets are all elevated above head height, any crossover that works well between low and low mid speakers may be chosen.

200 Hz used to be a common crossover frequency between low and low mid speakers in both front and horn loaded systems.

But those low speakers were not called "subs".

[Bill poster]

Originally Posted by weltersys

It is more easy to locate the source of sound when the frequency is above 100 Hz, but there is no magic cut off frequency where suddenly location of the source "goes away".

Most "subs" are fairly large and heavy, so are put on the floor/ground.
The lower the frequency, the longer the wavelength. Longer wavelengths are less affected by audience members standing or sitting in front of them, so we can get away with a steep crossover at around 100 Hz with the subs on the ground.

Move the crossover up to around 160 Hz, and vocals will be heard from the bass speakers, if the bass is left on the ground, the vocals will sound "muddy" if people stand in front of the bass bins.

Thanks, this is very useful info if designing stereo subs; and interesting too.

[Bill poster]

This is a crap sketch of the design.

Its basically a sub/stand with full range speakers above. I wanted a design which doesnt take up space, looks good and sounds decent with 30 hz bass.

The stand integrates a transmission line folded in 3 with a 6.5" woofer firing downwards.

The 'satellites' which sit on top are full range 3" and the 2.5 litre cabs are suspended by springs within a frame, similar to those old classic microphones. w

[chris661]

Hi,

My system is built on a similar principle, but using tapped horns for bass. It works, and in June it'll be at a meet, so I'll be able to say more than "well, I think it sounds good."

Chris

[weltersys]

Originally Posted by Bill poster

This is a crap sketch of the design.

Its basically a sub/stand with full range speakers above. I wanted a design which doesnt take up space, looks good and sounds decent with 30 hz bass.

The stand integrates a transmission line folded in 3 with a 6.5" woofer firing downwards.

The 'satellites' which sit on top are full range 3" and the 2.5 litre cabs are suspended by springs within a frame, similar to those old classic microphones. w

There is more moving mass in even a light cone than you may realize, the “isolation springs” shock mount will allow the top cabinets to move with their cone movement, which is not a good thing from the standpoint of intermodulation (Doppler) distortion. Of course, since you plan to use 3” speakers from 100 or 200 Hz up, IM distortion probably does not bother you anyway.

In a home listening situation, crossovers above 100 Hz or so are problematic with a tall set up as you sketched, because the low range of vocals and instruments will shift upwards and downwards depending on the pitch (notes) sung or played. This wandering vertical position ruins the stereo locational effect, and makes for an unrealistic stereo “image”.

In most music, there is very little vocal information below 80 Hz, the low note on a guitar. Choosing speakers that will allow the subwoofer(s) to be crossed around or below 80 Hz will avoid the wandering image problem.

Art

[Bill poster]

Chris wd love to see your design, sounds ace.

Art, thanks again. I didnt think about the cone movement to be honest. Hopefully the spring arrangement will be quite solid, triangulated front to back, so the cab movement will be negligable. I did some research and some of the more modern isolated mics use a kind of elastic cord which is looped around fixings.
I wanted to x/o around 120 hz but as I'm choosing either alpair 6 or JXr6's for this build, they can be set lower (I wd have to trim the square frames of the Jordan's to fit).

[weltersys]

Originally Posted by Bill poster

Chris wd love to see your design, sounds ace.

Art, thanks again. I didnt think about the cone movement to be honest. Hopefully the spring arrangement will be quite solid, triangulated front to back, so the cab movement will be negligable. I did some research and some of the more modern isolated mics use a kind of elastic cord which is looped around fixings.
I wanted to x/o around 120 hz but as I'm choosing either alpair 6 or JXr6's for this build, they can be set lower (I wd have to trim the square frames of the Jordan's to fit).

120 Hz at 24 dB per octave would be OK.

Elastomeric cord has replaced springs for microphone shock mounts for good reason.
Is there any reason other than "looking cool" for the springs (which will resonate and sound like an old spring reverb)?

Art