effect of reorientating baffle and drivers?

[leadbelly]

I considering building the Audax HT design CC as a FRONT PAIR. The why, you may ask is that the drivers are all on sale at PE and the CC seems to get rave reviews. So, regardless of the flames resulting from this proposition and questions of good sense, can someone humour me and answer this question:

If the drivers and baffle are reorientated as in the attached drawing into a WTMW alignment (the two W's stay in the same spot in the baffle and the baffle dimensions as well as all other box dimensions stay the same), does the speaker response change significantly (i.e. enough to require crossover redesign)? I'm not sure I know all the theory to answer this.

[sreten]

The response will hardly change.

The more normal TMWW should be OK too.

In fact the way these are normally built is MTWW to allow
an angled panel at the top to form the midrange enclosure.

sreten.

[leadbelly]

Thanks. Drivers are ordered.

I have a follow up question that is related. Since the speakers are to be fronts, I would ideally like to tune the box for more bass extension, yet I'm not ready to delve into a test & measurement rig.

If I reverse-model the response of the woofers in one of the modelling spreadsheets available, then play with the tuning of the box, but still maintaining the same sound level at the crossover point with the mid, can I expect to avoid any crossover mods at all (even padding adjustment)? Once again, the baffle would remain the same.

[sreten]

for an overdamped alignment
(assuming its near maximally flat)
simply use one port instead of two.
It will have no effect on the crossover.

The graph shows an example where two ports is the
flat response and one port is the overdamped case.

sreten

[leadbelly]

Thanks.

I've come up with yet another question.

The woofer xover for the design is shown below.

It appears to me that the 2 woofers are padded down significantly to match the efficiency of the mid (87.4 dB for the mid vs 89.3 dB for the woofer, both 6 ohm impedance). I believe the calculation is 2 woofers in series = 92.3 dB efficiency, 12 ohm nominal impedance, and the 22 ohm parallel resistor cuts about 4 dB (I'm not sure how to calculate that).

Can I leave out 1 woofer and recalculate the padding resistor value and also expect minimal impact on sound?

[sreten]

The woofers are not padded at all in terms of voltage
sensitivity, the impedance is reduced by the resistors.

You could remove one driver and resistor and double
the value of the capacitor and halve the value of the
inductor.

Voltage sensitivity will be the same as the series pair.

Nominal power handling will be halved.
Impedance will be halved.

You'll also need to redesign the enclosure - half volume.

sreten.

[leadbelly]

Originally posted by sreten
Nominal power handling will be halved.

You'll also need to redesign the enclosure - half volume.

Thanks. If power handling is halved, then it's a no-no to me.

I did put the woofer t/s numbers into a box calculator, and it showed me that the box is designed to a BB4 alignment, 48.5Hz tuning, 0 dB peak.

How do I go about optimizing the underdamped response example you gave? In other words, do I fix Qbox at a specific value and juggle others, or Fbox, etc.? I am prepared to play with box volume, but keep the baffle the same.

[sreten]

Just omit one port as suggested, sreten.

[leadbelly]

Originally posted by sreten
Just omit one port as suggested, sreten.

Thanks again. Drivers arrived, crossover components on order.

How about this idea for the enclosure? Will this muck the sound up too much?

Baffle same width, depth 1/2 * design, height 2 * design: all internal volumes same as published design, but it is now a 4 ft tall floorstander. One port omitted as you suggest. TMWW configuration of baffle; T and M at top of baffle, WW at bottom of baffle to get better room gain.

[leadbelly]

sreten's not around, can anyone else help?

Is my understanding of the theory correct:

1) The effect of lengthening the baffle is minor compared to effect of the baffle width on baffle step loss, so this is minimal impact.

2) The gain/polarity/dispersion effects from driver proximity in the original WTMW layout were not large since the drivers were relatively well spaced, more so than the typical d'Appolito layout.