I see some wonderful drivers but with low qts values so now when a low qts drivers loaded in open baffle then the lower part of the spectrum there will be peak now consider we use a compensation network to reduce the peaking.
But a usual approach is any driver at qts 0.7 is suitable for open baffle or infinite baffle loading. S
So now the question is that I really want to use super high sensitivity drivers in the open baffle but all of them have Qts < 0.35 so now how far its important to have Qts 0.7 Im starting to feel that is it really required to have 0.7 or may be 0.65 ish qt or can I go with 0.3 qts with compensation network?
But a usual approach is any driver at qts 0.7 is suitable for open baffle or infinite baffle loading. S
So now the question is that I really want to use super high sensitivity drivers in the open baffle but all of them have Qts < 0.35 so now how far its important to have Qts 0.7 Im starting to feel that is it really required to have 0.7 or may be 0.65 ish qt or can I go with 0.3 qts with compensation network?
I don't know about open baffles (with finite size), but theoretically, in an infinitely large closed box, Qts = 0.5 sqrt(2) ~= 0.7071068 results in an optimally flat low-frequency roll-off, Qts > 0.5 sqrt(2) in some peaking and Qts < 0.5 sqrt(2) in a more gradual than optimal roll-off. You can in principle always equalize it, but I could imagine that at very low frequencies, loudspeakers designed to be put in small closed boxes reach their maximum excursion at a much smaller power when put in an infinitely large closed box.
Before the time that Martin King popularised the higher Q dipole for EQless crossover, higher Q drivers weren't necessarily popular in the role. Even still, the design was specific and such a Q isn't going to automatically EQ just any dipole. I wouldn't go into using one without a plan for EQ.
True, the driver goes goes lower before it naturally rolls off, regardless of small wings, big wings, or infinite baffle.
A driver with a qts of .2 and FS=50 will roll off below 250hz, regardless if the wings are 4' deep (instead of a dip at 140hz then a +3 to +6db hump at 70hz).
A driver with a qts of .2 and FS=50 will roll off below 250hz, regardless if the wings are 4' deep (instead of a dip at 140hz then a +3 to +6db hump at 70hz).
Given this threads subject, Does anyone know how/why a Fostex fe126 which is a 4" low Qts can sound great in an OB?... https://www.audiocircle.com/index.php?topic=68604.msg636963#msg636963
Out of curiosity in the early days of the original FR forum I made an OB using a cheap RadioShack 8" FR driver's ~2.86 Qt, so it's not the driver per se, but the sum of the driver/baffle same as any other box alignment. It wound up being pretty big (quite the opposite as I assumed, needing nearly a full 4x8 sheet IIRC) and needed the sides to be folded back to 'taste' to roll off its mild sounding Fb peaking, but it performed fine to me and the local few that auditioned it.
Here the problem what I`m more concerned is on the bottom roll off and compliance when loaded in room. If you look at the 4 inch low Qts driver it will anyway have peak near its resonant frequency more than actually intended.
Very true, though my room's large/open enough not to be an issue except floor/ceiling, so had I chosen to use this for more than a proof of concept I'd of tilted it back as required to randomize it and of course don't recommend using such drivers in a HIFI app. Really, the only reason I did this was because some folks on the Basslist were deep into ribbons and Bob Carver's Amazing Platinum speaker system was discussed with woofer's supposedly having a high 3+ Qt! So curiosity got the best of me.
Hmm, Allen's post disappeared; oh well...........
Hmm, Allen's post disappeared; oh well...........
For a low effort (passive) system you will want a large high Qts driver with soft suspension (low Fs) and large Xmax.
When you go active, pretty much any woofer can be used. As for that, even seemingly completely unsuited ones... the craziest OB project I've ever seen (and actually helped building) used 6 pcs of RCF L12P110K per side, on a simple baffle just large enough to fit the drivers. That driver is a 100+dB 12" PA midbass for horn loading, with a Qts of 0.14(!!), 2mm Xmax and Fs of 55Hz. Completely nuts you say, and rightly so. Why this driver? Because we got 15pcs of them (reconed) from a surplus sale for almost no money and 12 of them were in perfect condition, haha!
With a ton of EQ, obviously (and beefy amps, also refurbished PA stuff) it was the best sounding bass I've ever heard in terms of articulation and texture, not to mention its punch and slam capabilities. There is so much inherent feedback in such a low Qts driver that it basically creates full motional feedback, the voice coil itself being the velocity sensor, linearizing the driver (within Xmax). That feedback is still strong enough way below Fs where a moderate to high Qts driver normally degenerates to force-steered mode, working purely against the quite nonlinear suspension spring leading to higher distortion even within the Xmax range.
I would not recommend going this route if you start from scratch and want to build a cost-effective system that must also cover sub-bass (<40Hz) at loud levels, obviously ;-) Just mentioning it to illustrate what's possible.
OTOH, a Qts 0.7 driver has only little intrinsic feedback and thus much less control over its cone motion and is more prone to suffer from suspension nonlinearities and other ill-effects.
When you go active, pretty much any woofer can be used. As for that, even seemingly completely unsuited ones... the craziest OB project I've ever seen (and actually helped building) used 6 pcs of RCF L12P110K per side, on a simple baffle just large enough to fit the drivers. That driver is a 100+dB 12" PA midbass for horn loading, with a Qts of 0.14(!!), 2mm Xmax and Fs of 55Hz. Completely nuts you say, and rightly so. Why this driver? Because we got 15pcs of them (reconed) from a surplus sale for almost no money and 12 of them were in perfect condition, haha!
With a ton of EQ, obviously (and beefy amps, also refurbished PA stuff) it was the best sounding bass I've ever heard in terms of articulation and texture, not to mention its punch and slam capabilities. There is so much inherent feedback in such a low Qts driver that it basically creates full motional feedback, the voice coil itself being the velocity sensor, linearizing the driver (within Xmax). That feedback is still strong enough way below Fs where a moderate to high Qts driver normally degenerates to force-steered mode, working purely against the quite nonlinear suspension spring leading to higher distortion even within the Xmax range.
I would not recommend going this route if you start from scratch and want to build a cost-effective system that must also cover sub-bass (<40Hz) at loud levels, obviously ;-) Just mentioning it to illustrate what's possible.
OTOH, a Qts 0.7 driver has only little intrinsic feedback and thus much less control over its cone motion and is more prone to suffer from suspension nonlinearities and other ill-effects.
But what if we use multiple drivers like 8 inch woofers say with Fs of 40hz, wouldn't it not have to work that hard which in return would reduce the ill effects that you mentioned ?
'Sounds' like you're trying to load it to Fs, but just like sealed, it ideally needs to be tuned as if it's in an optimized 0.707 box alignment to sufficiently damp any peaking, so the published FE126 specs = 206 Hz Fc.
