Does anyone make a separate mid-range speaker for a modular system?

[Bill Fitzmaurice]

[quote name='LawrenceH' timestamp='1341500534' post='1720115']
From a dispersion perspective I think it's better to cross as low as possible to avoid off-axis nulls due to destructive interference between drivers in the crossover region
[/quote]That's much more of a concern with PA than electric bass. So long as you use at least 3rd order filtering on the midrange the response overlap zone is slight enough to minimize ill effects to the point of being virtually inaudibile, especially when compared to a typical commercial cab with woofers horizontally aligned and no midrange driver at all.

[LawrenceH]

[quote name='Bill Fitzmaurice' timestamp='1341502780' post='1720170']
That's much more of a concern with PA than electric bass.
[/quote]
Yup I'm sure this is correct - as I said my experience with this type of design is PA and for bass it probably doesn't matter nearly as much.

[quote name='Bill Fitzmaurice' timestamp='1341502780' post='1720170']
So long as you use at least 3rd order filtering on the midrange the response overlap zone is slight enough to minimize ill effects to the point of being virtually inaudibile
[/quote]

I differ on this from a PA perspective, at least crossed below 2k or so where individual frequencies are still easily perceivable as distinct musical notes. It might be a slight difference but if you're looking for it, it's there IME and will be more noticeable on things to which this register is critical. Really notice it on wedge monitor speakers where thanks to the angle you can easily move in two planes at once in relation to the drivers. However on bass, it may be audible but inconsequential... though I have to say for me the 1-3kHz range is really important whatever the instrument. All else being equal I'd rather have a system that didn't cross over in this region at all.

[quote name='Bill Fitzmaurice' timestamp='1341502780' post='1720170']
especially when compared to a typical commercial cab with woofers horizontally aligned and no midrange driver at all.
[/quote]
Absolutely yes... though if your nulls are only a few degrees off centre then whether it's horizontal or vertical, it's easy to move in and out of them.

The advantages for bass may be small in practice, but properly implemented the only disadvantage I can see to crossing lower is cost, but that can be very significant!

[stevie]

Dispersion isn't the only consideration in designing a midrange add-on. Spending up to £100 on a driver, half as much again on a crossover and then not making the most of its benefits by crossing over as high as 1k doesn't make a lot of sense. It wouldn't surprise me, however, if a lot of commercial bass cabs are crossed over that high in order to reduce the cost of the crossover. For the current crop of PA midrange drivers 600Hz is usually good, although there is a lot more than you might imagine to getting the crossover point right: much depends on the drivers you are using.

There are currently some very good, low-cost midrange drivers available - from Celestion in particular - which could form the basis of a cheap midrange add-on. Unfortunately, designing a passive crossover is not an undertaking for the faint-hearted and, as Lfalex points out, an active solution would be complex, requiring asymmetrical slopes, phase compensation and frequency response shaping (all of which is relatively easy to achieve with a passive solution) - not to mention an additional power amp.

The benefits of having a separate midrange driver are very worthwhile, however, and I'd never want to be without mine.