Making different drivers cover same range

[tech.knockout]

Is it a big no no making two different but similar bass/midbass drivers cover the same range?

Similar as in: efficiency, qts, power rating, xmax, and cone mass. Same diameter. They will be crossed over well in advance of their breakup region.

[BHTX]

It's usually a "big no no" to have even two identical drivers covering the same frequency range, unless they're crossed over fairly low relative to their size and center to center distance vs wavelength at the xover freq.

[Cal Weldon]

Tell us what you're thinking and we'll see if we can discourage you.

[tech.knockout]

Im not thinking of anything specific.

I just have a pair of old broken Electrovoice 15L sitting around that can be reconed for cheap. I want to use them if i can.

However, I prefer a second similar 15" because of the limited xmax/displacement typical of high efficiency drivers (and increase the efficiency of the system further).

The drivers would be run up to around 400hz, which I presume is ok for breakup and center-center distance requirements.

Perhaps an example you can use to discourage me is the eminence delta 15.

spec sheets: http://archives.telex.com/archives/E...line%20EDS.pdf
http://www.eminence.com/pdf/deltapro-15a.pdf

[PeteMcK]

Probably only a 'no-no' because few have tried it, have a look at the method used here:

http://www.fortunecity.com/rivendell...d/dddllqd.html

[Moondog55]

I know that using dissimilar drivers to cover the same range is "unfashionable" now but was used by Wharfedale in many early systems.
I've tried it myself and can't say that the sound produced at lowish levels was any better or worse than using 2 identical drivers, and due to manufacturing tolerances drivers will never be identical anyway, tahat said I'd not use it for mid-range where you want maximum clarity, but try it in the bass, remember "experience is the sum of all of our failed experiments"

[tinitus]

I plan to use an 18" and a 12" in a closed 2.5way with a CD/waveguide, maybe crossed at around 300hz and 700hz

[LineArray]

Originally posted by Moondog55
...
and due to manufacturing tolerances drivers will never be identical anyway, tahat said I'd not use it for mid-range where you want maximum clarity ...

Hi there,

i fully agree to what you say concerning manufacturing
tolerances.

IMO dissimilarity of drivers can be used to improve sonic
quality. In my dipol 08 design i use 3 drivers of same type to
cover the whole range. I select them due to tolerances,
not to be identical but to complement each other ...

There are further examples for using dissimilar drivers:

The danisch DALI Speakers e.g. combine a dome and a ribbon
tweeter covering the same range as far as i know.

The dome tweeter delivers wide dispersion while
the ribbon delivers transient detail in the direct sound,
that's the idea behind it, and the design seems to be very
successful.

It's a matter of tuning XO and power levels correctly and find
a suitable arrangement for the drivers on the baffle to match
them. Phase shifts between the drivers have to taken into
account and compensated for, if necessary.

So i'd like to encourage tech.knockout to make his experience,
since i agree that combining differing drivers at lower
frequencies is not that critical in tuning ...

btw: I really love this forum, because we can discuss even
somewhat strange ideas here, without beeing discouraged too
much usually ...

There is not much fun in always reproducing known and
so called "proven" concepts IMO.

Kind regards