AllenB is correct!
IMHO, the question about Q is really about how much EQ do you want to do, and how are you matching it to the woofer?
Attempting a maximally flat (0.7) transition is often the easiest. Also, stuffing matters a little, so an enclosure that's a little too small may be helped by stuffing which could add around 10% of the effective volume. Maybe less in these small sizes.
The process is going to be something like, get the best you can, measure impedance and response of the drivers in place, and the create a crossover based on those measurements. At the end of the day, it's best to be too small than too large. You can compensate for too much bass easier than too little.
IMHO, the question about Q is really about how much EQ do you want to do, and how are you matching it to the woofer?
Attempting a maximally flat (0.7) transition is often the easiest. Also, stuffing matters a little, so an enclosure that's a little too small may be helped by stuffing which could add around 10% of the effective volume. Maybe less in these small sizes.
The process is going to be something like, get the best you can, measure impedance and response of the drivers in place, and the create a crossover based on those measurements. At the end of the day, it's best to be too small than too large. You can compensate for too much bass easier than too little.
It's been a very long time since I felt this was true. There was definitely a period prior to 2000 when new technology seemed to be the answer to dome limitations. Plenty of excellent exemplars in the $50 to $150 range today though.
Infinity popularized a number of different solutions, even having a planar magnetic dome I believe, all of which have IMHO been bested by a wide range of solutions available today, some dome, some not.
I'm talking for my personal tastes, i like the treble of a DE250 as a tweeter in a short WG and even more the Radian 850PB also in a short WG and also some small alumnium cone (and dustcap) wideranges... but i don"t like as much the dome tweeters, the highest treble exhibits irrealistic artefacts and the sound is thin (a kind of overdamping) in the lowest ranges.
I'm not saying that the dome tweeters are bad.
Chamber size is more a product of necessity for me. How big can it be? If it has to be small, then compensation of the impedance peak may be necessary to compensate for the smaller size.
A Q of 1.0 at 200Hz for a pending 400Hz xover point is something that must be suppressed, or it will be audible and make filter alignment very difficult. Usually a higher Q and frequency is less damped and will ring like a bell. A low Q sealed enclosure will still have an increase in Q and frequency over that of a driver in free air. However, it will be at a much lower frequency than a smaller volume.
The ways to avoid, side-step, or fix the resonances, whatever the box alignment, equate to using a TL, aperiodic, multichamber, or filter with electrical compensation. Simply stuffing or not will not remedy these issues.
A Q of 1.0 at 200Hz for a pending 400Hz xover point is something that must be suppressed, or it will be audible and make filter alignment very difficult. Usually a higher Q and frequency is less damped and will ring like a bell. A low Q sealed enclosure will still have an increase in Q and frequency over that of a driver in free air. However, it will be at a much lower frequency than a smaller volume.
The ways to avoid, side-step, or fix the resonances, whatever the box alignment, equate to using a TL, aperiodic, multichamber, or filter with electrical compensation. Simply stuffing or not will not remedy these issues.
Hmm... is this applicable also for home enviromnet? 200Hz to 400Hz region is below/around the Schroeder frequency for a typical domestic room, hence it's hard to separate what's ringing, the room or the speaker and if the ringing/frequency response of the speaker response with Q of 1.0 at the lower midrange blends well with the room (or EQ-ed to the room), then a Q of 0.5 on the speaker side could be worse, despite it have less ringing on its own, IMO.
More related to using midrange drivers with higher Qts.
Monotoks example was using a low Qts driver around .3 so it is rather friendly to small boxes.
The actual response from a .5 to 1 Qtc didnt exhibit a huge peak in the lower response.
Modeling a higher Qts driver from .4 to .6
Going from .5 Qtc enclosure to a 1 Qtc enclosure.
The resulting peaks that result will be rather obvious or at least more obvious with .5 to .6 Qts driver
Shouldn't be to difficult at that point to decide that lower Qtc or larger enclosures are required for high Qts midranges.
Rather simple, real world there is a peak in the lowend response. Showing non ideal overdamped enclosure at low frequency.
Depending on crossover frequency the high Q could or could not result in issues with the overall response.
Most the issue is low frequency. If the crossover point is high enough. Technically its easier to get away with a smaller mid chamber.
If the driver mechanically allows it.
Far as absorption at mid frequencies, stuff it.
If a extremely low crossover point is used and you have low frequency concerns.
Reduce parallel walls. AKA make a wall/s angled, then stuff just the same.
Monotoks example was using a low Qts driver around .3 so it is rather friendly to small boxes.
The actual response from a .5 to 1 Qtc didnt exhibit a huge peak in the lower response.
Modeling a higher Qts driver from .4 to .6
Going from .5 Qtc enclosure to a 1 Qtc enclosure.
The resulting peaks that result will be rather obvious or at least more obvious with .5 to .6 Qts driver
Shouldn't be to difficult at that point to decide that lower Qtc or larger enclosures are required for high Qts midranges.
Rather simple, real world there is a peak in the lowend response. Showing non ideal overdamped enclosure at low frequency.
Depending on crossover frequency the high Q could or could not result in issues with the overall response.
Most the issue is low frequency. If the crossover point is high enough. Technically its easier to get away with a smaller mid chamber.
If the driver mechanically allows it.
Far as absorption at mid frequencies, stuff it.
If a extremely low crossover point is used and you have low frequency concerns.
Reduce parallel walls. AKA make a wall/s angled, then stuff just the same.
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For an enclosure for the mid driver I go oversize with a low Qtc. As the mid would be working above it's piston range it's not treated like a woofer enclosure design. I find the larger mid enclosure helps with the back wave and the back panel is at an angle to assist. Also consider vented, aperiodic, OB or TL instead of sealed. You'd be surprised how much back wave energy there is in a mid and did an experiment with Andy G over a decade ago with the result going from sealed to stuffed TL.
Have a look at some of Troels' mid enclosure designs and you see some effort in back wave control particularly the one with the inverted V.
Have a look at some of Troels' mid enclosure designs and you see some effort in back wave control particularly the one with the inverted V.
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From backwave point of view, a very small chamber can be beneficial, good examples are the mid-domes. See the ATC SM75-150 mid-dome, which is one of the best midrange driver ever made. Its back chamber is only as large as the magnet system allows.
If you are able to get the response you want and the excursion is good at the SPL you want, then there is no problem with Q.
I was told long ago that you can get a satisfactory response with low or high Q, even if you have to use EQ, but that it should always be less than critically damped, because it just doesn't "sound right". If that is true I suspect it is as much a matter of music production as it is reproduction, because it was probably meant to sound good on boomy speakers.
If you want to go extreme there are analog circuits that are meant to manipulate the driver's Q through impedance shenanigans that I descovered a few days ago. LEMF and ACE-BASS. These may be overly complicated compared to modern software EQ tools though.
If you want to go extreme there are analog circuits that are meant to manipulate the driver's Q through impedance shenanigans that I descovered a few days ago. LEMF and ACE-BASS. These may be overly complicated compared to modern software EQ tools though.
