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8 Inch Woofers?

Andy:

I really appreciate all your answers on the Low B2 and B4.  Question for
you...have you ever considered designing and building a 4x8 cab?  What brand of
drivers do you use in the B2 and B4, and are similar 8" drivers available?  My
opinion (and it's merely an opinion) is that a 4x8 can potentially have the
higher sensitivity of a 410 but be closer to the size and weight of a 210
(given that the T/S parameters of the drivers make this possible, of course).


Would you consider designing and building a custom 4x8 that similar to the B4?
Please let me know...

Regards,
Dave

Andy Replies:

The problem is that 8" drivers either (1)have a higher resonance, which makes them impractical for low bass, or (2) if they're made to produce low bass, their efficiency would have to be even lower.

The other problem is that 4 magnets weigh more than 2 magnets. A 4x8 cab with good drivers will never be as light as a similar quality 2x10.

I have thought of making a small cab with 8" woofers, but it would never be capable of reproducing the low B.

My woofers are Eminence. They can make anything you want.

I don't do custom work. it takes a LONG time to do a decent design job. Anything billed as "custom" is likely to be a thrown-together piece of junk.

Thanks,

Andy

Dave Replies:

Hey Andy:

Thank you for the reply.  OK, so tell me this if you will.  I thought that when you "couple" multiple drivers (like putting two 10's into the same volume), you actually reduce the Fs of the combined collection of drivers, thus making it possible for (say) two 10's to produce a lower frequency than a single 10 could (given adequate volume of the enclosure of course).   I'm don't know how you calculate what the new Fs is though, come to think of it.   If you have time, would you be willing to give me a quick explanation of how this works when you have multiple drivers?

I have toyed with the idea of possible building a 4x8 myself, but I don't know how good it would turn out.  Is there any software for speaker enclosure design that isn't incredibly expensive but would handle multi-driver configurations?

Btw, I am just really thrilled to see so much innovation happening in the bass guitar area.  It's about time.  Not surprisingly, all the innovation seems to be done by very small companies like yours rather than the big companies.  I truly hope that you really grow Acme into a tremendous success.  That said, I'm still looking to find someone local who has a B2 or B4 that I can play through just to get an idea of how it would work for me.

Thanks and best regards,

Dave.

Andy Replies:

Wrongo. The Fs doesn't change. The efficiency changes when the drivers couple, not the Fs. It would be nice if it did.

 Thanks,

Andy

Further notes on the subject:

At its heart, this is a discussion about the basic concept of reproducing bass by using a larger number of smaller drivers. 

I had a vision about 30 years ago, of a full-range loudspeaker made up of hundreds of Sennheiser 414 headphone diaphragms. A perfect loudspeaker, I figured. I had used the 414’s (purportedly developed for the Apollo program), and they had a great full-range sound. Why not use a ton of them, and make the perfect full-range speaker, with no crossover, and essentially perfect transient response?

Nice idea, but naïve. Headphone drivers have a high resonance. In the case of the headphone, the high resonance is compensated for by the natural rise in bass in a confined space- an advantage lost in an open room.

This multiple-headphone is the extreme logical extension of the 15” vs. 12” vs. 10” vs. 8” etc. discussion. Ironically, even this extreme example seems really cool, in a way. The problem is that it won’t work. The bass will disappear.

The most notable practical example of this concept, in my opinion, is the venerable Bose 901. Bose managed to get an array of 4.5” drivers to reproduce deep bass. Even so, they were forced to use extreme equalization in order to do so, and required an unheard of amount of power, especially for 1968. (But I still like the way the 901’s sound. Call me sentimental.)

The use of 8” drivers would be considered a less extreme attempt to squeeze bass from a larger number of smaller drivers.

I have heard of bass guitar speakers using even smaller woofers than 8.” The idea is silly to me, and I don’t consider such a speaker to be a serious attempt to reproduce the full range of the instrument. I believe the “designer” of such a system could be laboring under the weight of the same false premise as Dave- that multiple woofers would exhibit a noticeable reduction in resonant frequency when coupled together. Oops.

I my opinion, the 10” woofer is the smallest woofer that can be used for the five string bass, and even so, it’s only barely practical.

What I didn’t mention to Dave is the unfortunate fact that 8” woofers cost essentially the same as 10” woofers. No advantage there.

Bottom line: Don’t look for a bass guitar speaker using 8” woofers from Acme Sound. I prefer to stay in the real world.

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