Quad 22l type 2.5 way crossover/speaker - diy alternative

[charliemouse]

Hi,
I'm wondering if anyone has had experiene of building 2.5way type speakers. I have some quad 22L's and fancy seeing whether I can come up with something that sounds as good or better.

22Ls use two bass drivers, one sealed for bass and mid, one ported for bass.

Any suggestions as to
1. Why they should want to use this approach (rather than true 2 way) is beneficial?

2. Whilst bass is superb, the mids I find less articulate than comparable prices B&W CM7s: Would use of this layout of two bass units (both of which effectively just have a low pass crossover), but allowing them to handle less middle, and inclusion of mid unit be a reasonable approach.

Essentially, I'm looking at a true 3 way, with an additional bass driver for the lower bass rangers like the quads.

Cabinet layout and first glance at crossover, & *very* crude model (estimates from crossover, not real data) of 22Ls is as follows.

[Willitwork]

Originally posted by charliemouse
Why they should want to use this approach (rather than true 2 way) is beneficial?

In theory a separate smaller sealed enclosure allows a given driver to deliver better midrange performance (at the expense of LF output) while keeping the crossover design simple thanks to the natural bandpass filtering properties of the smaller enclosure. At the price the 22L sells for (they cost less than audiophile quality small monitors) they couldn't design overly complex filters for the drivers, it's cheaper to divide the cabinets into separate enclosures.

However there's no way a first-order crossover would allow those Kevlar drivers (well, one of them) to deliver well-controlled midrange, the crossover frequency (around 350Mhz if I recall well) is low enough to create a hollow area in the 1500-2500Mhz range assuming the tweeter has a third-order crossover, and I'm quite sure it does. Quads have always had the reputation of sounding somewhat "reserved" -I dare say muffled- and the 22l is no exception. With its emphasis on bass at the expense of midrange clarity this is clearly a design destined more for HT purposes than serious music listening. The drivers are Chinese made to Quad specs but to me they appear to have been seriously inspired by Audax. Whether that's a good thing or not is difficult to say since they are being used with such minimalist crossovers. Audax drivers were great but usually required more filtering.

Whilst bass is superb, the mids I find less articulate than comparable prices B&W CM7s

The CM7 costs a little more and is a true 3-way. I never heard it but so far I have never heard a B&W speaker that sounded bad, even though the entry-level models have limitations these are usually well controlled. Along with JM Lab, B&W is my favorite commercial speaker manufacturer. I have no doubt the CM7's midrange qualities are well above the 22l's.

Would use of this layout of two bass units (both of which effectively just have a low pass crossover), but allowing them to handle less middle, and inclusion of mid unit be a reasonable approach.

Your crossover schematics are still that of a 2.5, although they are now second-order (12dB/oct) for the 6.5's and third-order (18dB/oct) for the tweeter. This puts the tweeter out of phase with the other drivers and such a 45-degree misalignment cannot be corrected by wiring the tweeter in reverse polarity. You'd need a fourth-order (24dB/oct) crossover for the tweeter at a slightly lower cut-off frequency to correct phase between drivers. If this is the original crossover I don't understand what Quad was thinking.

A true 3-way would require both a low-pass and high-pass on the middle driver. Since the middle driver on the 22l does not seem to be contributing to the lower bass output I don't think using it as a real mid would affect bass output much but designing a proper crossover for these drivers would require access to their actual specs and even with those it's still a gamble. Designing a decent 3-way crossover from scratch is not for the faint of heart. Before you attempt to do this you should perhaps experiment with building a better 2.5-way crossover for the 22l's (make sure to keep the original crossover) since the one it comes with is pretty basic.

[planet10]

Originally posted by Willitwork the crossover frequenc
y (around 350Mhz if I recall well) is low enough to create a hollow area in the 1500-2500Mhz range....
Your crossover schematics are still that of a 2.5, although they are now second-order (12dB/oct) for the 6.5's and third-order (18dB/oct) for the tweeter.

That is some serious HF response

The XO on the 0,5 driver is 1st order with impedance compensation.

dave

[sreten]

Originally posted by Willitwork


......However there's no way a first-order crossover would allow those Kevlar drivers.......

......If this is the original crossover I don't understand what Quad was thinking......

Hi,

The "midrange" unit has second order electrical,
not known what order (likely 3rd/4th) acoustic roll-off.

The second point is obviously true.
You cannot just analyse the electrical network to work out acoustic topology.
Wiring of drivers depends on the acoustic, not electrical, topology.

FWIW there is nothing wrong with the basic topology.
The 0.5 way driver is used for baffle step compensation.

Turning it into a 3-way would require major redesign and a
reduction of sensitivity, as the midrange would include BSC.

/sreten.