Speaker distances

[epistaxsis]

I am trying to  calculate how far apart my mid bass drivers and my tweeters need to be.

I expect it has something to do with a calculation based on the crossover frequency (which is 2.2KHz in my case).

I also would like to hand the tweeters (i.e. not have the directly below the mid bass drivers) - I know this hepls with imaging but again what are the rules here?

Anybody got any ideas or point me in the direction of a suitable online resource?

Thankyou in advance

 

[Paul Joppa]

Of course it depends on teh acoustical crossover function, which may or may not (probably not!) be the same as the electrical crossover.

The best case (IMHO) is a Linkwitz-Riley crossover, where both drivers are in phase with each other throughout the crossover frequency. There will be a null at crossover at +/- 90 degrees if their acoustic centers are 1/2 wavelength apart at the crossover frequency. These nulls will cause the image to wander as the reflected sound won't have the same frequency response as the direct sound. So ideally, they should be less than 1/4 wavelength apart; that's about 1.5 inches center to center.

So unless the midbass is 2" outer diameter and the tweeter 1", you can't achieve the ideal. Since the ear seems to be more sensitive to horizontal images than vertical, it is common practice to place them in a vertical arrangement. If they are one wavelength apart (6 inches), there are nulls at +/- 30 degrees, corresponding roughly to the floor and ceiling bounce - a popular choice among theoretically-inclined designers, and about as far apart as you can get with good integration.

 

[richardl]

I would recommend that you follow Paul's advice about the 4th order L-R xover(and use The Loudspeaker Design Cookbook 6th ed. to calculate backup equations.  The internet calculators are pretty bad IME)but, I would also avoid the offset tweeters if you want the best imaging.  As Paul said, get the mid and tweet drivers as close together as possible. You can get away with more distance in the bass but, surprisingly, less than you would suppose IMO. Think Totem Pole for driver lineup and make that box small as possible, Thick, heavy, braced and dense to get rid of noise.. And no vents!!(personal choice here actually, I hate boomy bass)  Surprisingly a heavily built box improves the sound more than you would imagine.