[quote name='Bill Fitzmaurice' timestamp='1416922324' post='2615030']
First off, no fifteen will give useful response to 4kHz. On-axis you'll hear something, but off-axis the highest a fifteen will go is perhaps 1.5kHz. Even twelves aren't much good past 2kHz or so. If you want to run without a midrange driver you need to go with tens ---
You do need to be concerned about the mids... You could do a vertical 2x10 in 60L net, but IMO it's easier to carry two small cabs...[/quote]
That makes a lot of sense, and fits with what the people over at TalkBass said about beaming from larger cones. At some gigs I need to push the Acme, so I'm guessing I would need two tens, especially in a sealed box. But I want to build a combo, so I'm looking at putting it all in one box and driver weight is an issue. I seem to recall reading something to the effect that smaller speakers physically close together can beam like one larger speaker, is that correct? Is that why you recommend vertical stacking?
Anyway, on your advice I will be looking for two tens to put in a sealed box, and I will choose the box size to get the rolloff slope I prefer. I'll look at the B102s and similar alternatives, especially anything lighter. Power handling may be an issue as my power amp is 1000W. I'll also need to learn how to model a sealed box with multiple drivers.
[quote name='Bill Fitzmaurice' timestamp='1416922324' post='2615030']
Second, your preference for sealed versus ported has nothing to do with the cabs, everything to do with the instrument. Double bass just doesn't go low enough to require the lows that a ported cab produces ... Frankly I can't imagine a worse cab for double bass then an Acme, unless you don't want your double bass to sound like a double bass..[/quote]
You may be right, but my preference for sealed speakers extends to listening to recorded music too. It's hard to quantify but to me, sealed sounds more coherent.
When you say double bass doesn't go low, I guess you are referring to the fact that in its lower range the fundamental is much less audible than the first few overtones. None the less it is there, and to my ears it's an important part of the sound. This point has always confused me: if the fundamental is already weak, won't using a speaker which is also weak in that range exacerbate it? Surely it should be flat, then the level of fundamental will remain accurate to the instrument?
I guess this is a complicated issue, because what I just said assumes that the signal source is accurate to the instrument, like say a good microphone. But in fact, unlike magnetic pickups, common bass piezo bridge pickups produce massive fundamental if correctly buffered, and maybe a speaker with highish rolloff is the antidote to this? There are so many variables.
On your last point, I must admit there have been times when I don't want my double bass to sound like one! In fact, I used to tour with a theatre show that played large stadiums, and I used distortion, pitch-shifting, delays, octaves, dynamic filters etc, sometimes all at once! I don't do that any more, but I play a wide variety of music that goes outside traditional double bass music, sometimes verging on rock volumes, and some gigs that require a very big loud sound. I suppose I could keep the Acme as an extension speaker for those times and focus my combo project on getting a natural sound.
Thanks for your help Bill, it is a privilege to get such generous advice from a master designer.