.5 alignment electric bass cabs

[Rick James]

Bill, could you comment on this thread? Thanks.
http://www.talkbass.com/threads/5-align ... s.1118427/

[Bill Fitzmaurice]

Sure. First, a .5 alignment is when two identical woofers are used, but one of them is low passed. One reason for doing this is baffle step compensation. Below where the baffle is 1 wavelength in dimension response rolls off, eventually settling in 6dB down from nominal. If you use two drivers with one low passed at the right frequency it will give back that 6dB only at the lower end of the spectrum where you need it for flat response. This is especially handy with pole mounted PA cabs that are run full range without subs, and that’s where you used to see this technique employed a lot. You don’t see it so much anymore since nowadays subs are the rule.

Another reason for doing this is the one noted in the thread, to broaden midrange dispersion and eliminate high frequency comb filtering when drivers are mounted side by side. Above where the two driver centers are more than 1 wavelength apart comb filtering causes high frequency response to change as you move across the sound field. Placing the drivers side by side also results in the midrange dispersion angle being more than halved compared to one driver. The cure for both those concerns is to low pass one driver, or in the case of a 4x10, 6x10 or 8x10 one of the vertical sets of drivers.

In the thread the poster low passed one vertical set of drivers in his 4x10 with a first order filter. A second order filter would work much better, and the added cost would be minimal, as the required capacitor isn't expensive. A higher knee frequency could be used as well, lowering the cost of the inductor.

One potential problem is if the drivers are series/parallel wired in a 4, 6 or 8x cab. If you don't know how to wire the cab up correctly you can really make a mess of things.

Why .5 alignments aren't used by the electric bass cab industry in general comes down to cost, pure and simple. At the manufacturing level the cost of the filter is perhaps $15, but manufacturers hate to spend even one buck on anything that the consumer can't see.

[Rick James]

What are your thoughts about this?
http://www.talkbass.com/threads/diy-410 ... t.1119819/

[Bill Fitzmaurice]

What are your thoughts about this?
http://www.talkbass.com/threads/diy-410 ... t.1119819/

It's not something I'd do. There are two inherent deficiencies in the 4x10 design. One is horizontal dispersion, which you can improve upon with a .5 alignment. The other is where it aims. Unless you've got auxiliary ears mounted on your butt cheeks you can't hear the mids and highs until you're a good ten feet out from your rig, and how often do you have that luxury?

Look at it this way. What's the most acclaimed commercial bass cab ever? It's the SVT. Why is that? Output capability aside, because a modern 2x10 can beat a '69 SVT in output, the main reason for its popularity is that the uppermost drivers are high enough off the floor that you can actually hear what you're playing, even if you're crammed on a tight stage. When you look at comments about why they sound good it's always tone, tone, tone. What's special about the tone of an SVT? Nothing. What's different about it is that you can hear the lows, mids and highs, not just the lows. Using a .5 alignment 4x10 won't do a thing to improve how well you can hear it at the close range where you're usually standing.

The way to address both of the inherent flaws of the 4x10 is to not use a 4x10. Use a pair of 2x10s, vertically aligned.

[Chris_Allen]

Would there be any value in a tall and skinny version of the Jack?

[Bill Fitzmaurice]

Would there be any value in a tall and skinny version of the Jack?

Not really. The Jack isn't a direct radiator, its a horn, with dispersion characteristics which are quite different from a direct radiator. Its midrange dispersion pattern isn't determined by the dimension of the mouth, it's determined by the dimension and flare at the throat. The J12, for instance, has an eight inch throat, so its midrange dispersion is about the same as a direct radiating eight inch cone. This shows why:
http://www.acoustics.salford.ac.uk/fesc ... slider.swf

Pattern control is also why the initial horn flare at the throat section is all on the vertical plane.

[Rick James]

Any more comments on this thread, seeing how much more is there now?
http://www.talkbass.com/threads/diy-410 ... t.1119819/

[Bill Fitzmaurice]

Any more comments on this thread, seeing how much more is there now?
http://www.talkbass.com/threads/diy-410 ... t.1119819/

Only that some things should not be done via committee.

[Luke the Fluke]

except giraffes?

[DJPhatman]

Any more comments on this thread, seeing how much more is there now?
http://www.talkbass.com/threads/diy-410 ... t.1119819/

1st, I'm trying SOOOOO hard not to do my Dave Chappelle skit! "CHARLEY MURPHY! HA, HA!"

Anywho, don't be a shee-people and think just because they wrote it, it must be right.

[LelandCrooks]

Yea, I tried to pull in the reins a bit. I get lots of requests for plain simple bass cabs. The 4x10 seems to still be insanely popular. The slant top is as complex as I will go. There's no way to make a 4x compete with the supercabs like Bill's horns and some of the other designs. Simple and cheap are my goals.

[Bill Fitzmaurice]

The slant top is as complex as I will go.

That's still going too far. It seems like a good idea, in terms of what the player standing a few feet in front of the cab will hear. But beyond a few feet what happens to the mids and highs coming out of that slant section? They shoot over the audience instead of at the audience.
Bottom line, if you have a 4x10 you can make it work better by converting it to a .5 alignment, and the cost is low enough for it to be worthwhile. But nothing can be done to a 4x10 to get results as good as a pair of vertically aligned 2x10s. You can polish a turd, but even if you do it's still a turd. IMO if talkbass wants to do their members a solid with respect to the 4x10 it would be by adopting this logo:

[LelandCrooks]