Can you suggest a speaker or driver compliment that you think comes alive at 70dB the same way it does at 90dB? My Unity horn system sounds stunning from 80dB on up to the point where I quit but might as well be a 5" driver two way at very low levels. BTW: The eight sealed 12" XXLS woofers have a Qms >10.
My previous version of this system used a 15LW1401 per channel and before that a JBL2226. They behaved no different WRT very low listening levels when compared to the current setup, only the macro dynamics at low frequencies have improved for the better.
Hi,
This is where I sick my foot in my mouth🙂. I don't know the secret sauce and have no data or proof other than my biased opinion, that is why this is such and interesting thread. I'd really like to know but when my larger drivers were in a sealed alignment and stuffed, they just never seemed correct at low volume.
When I dropped them in open baffle alignment and eq (roughly 17-20 db) I found I they could be played at lower volume and still sound good. I sometimes think air coupling? Velocity vs Pressure sound? Then you have 8x12" sealed woofers, this should be plenty so thats not it, also that would mean surface area is not it either.
I have a slightly drooping response of around 7dB from 30-18000hz. This might compensate for equal-loudness and since it's open baffle, maybe at higher volumes the bass doesn't overpower the system like a sealed or ported would so maybe it is all equal-loudness?
I use a radian 1.4" compression driver in SEOS-24 over a 15TBX100 with wings and stuffing behind the driver, crossed-over around 525hz. Very mismatch sensitivity so I'd really like to change that but so far I've not been able to with better results. Thinking of stepping up to an 18hp1060.
What frequency range do your 8 XXLs cover? What is your midrange driver size?
I do not have a calibrated absolute level mic so my estimated SPL levels might be off if I were to measure. When you say 70 dB what weighting is that? Is that at the listening position?
I've tried sealed peerless XL, 15TBX100, Vifa NE265W-08 in sealed and ported, satori 6.5 in, NE225-08, 8NDL51 in ported. 6 x 5f120 fe in ported and GW-1858 and Alpha 15A in OB h frames. I feel the OB consistently played better at low volumes.
We do all of our listening at low level both movies and music as we really don't like loud music. Of course every once in a while an album deserves volume!
Maybe I can try to so some reasonable absolute SPL tests if anyone is interested.
At this point I'm willing to try most things as long as it doesn't cost me more $$$ on drivers as I've not been able to pick any simply based on T/S parameters, but maybe I'm looking at the wrong ones. I'm open to some education as it will cost me less $$$ for trial and error.
Thanks,
P.S. I've recently read the 3 phase papers from http://www.davidgriesinger.com/. Seemed pretty interesting.
That's very close to my current target response, I aim for a 6dB droop. This works very well with CD horns.
300Hz. There are four 5" mids per side that cross at ~1KHz to a B&C DE25 compression driver in a Unity horn.
Flat, listening position.
I've just recently started playing with OB bass in another system but haven't yet formed any opinions on it's abilities at low volumes.
For me there are two types of listening, either active at 85-95dB or background, which is some 20dB lower in level. No one would say my system sounds awesome at these background levels, but it really does switch on as the levels rise. Above 100dB it will take you places few domestic systems could.
I've never had the pleasure of hearing a Unity or Synergy. Those must hit cruze control at 100dB! Thats loud!
I am going to stick my contrary oar in these waters. My belief is that many systems with poor frequency response sound "ok" at elevated levels, but do not sound good at low levels, because the response curve causes the frequencies that are "lower" in response to be inaudible. Build a speaker that does not have these "holes" in response, it will sound good at both low and high levels.
This is exactly my point, too. While the equal-loudness curve may certainly play a role, if it were the ONLY (or even the main) cause for the perceived loss of dynamics and bass at low volumes, then this should happen with all speakers, regardless of their parameters.
IMO, this is NOT the case, and in particular, woofers with low mechanical damping (i.e., low (Fs/Qms) ratio) DO sound better and more "alive" at low listening levels.
Yes, it does. My personal approximate threshold is (Fs/Qms) ~ 5. Anything below that, I would consider satisfactory.
Marco
While "low and high" playback levels certainly have their effect, my experiences tell me that basically it boils down to the mechanical properties of the moving parts. The more damping that has to be applied to get a nice freq response, the more "veild" it may be at lower listening levels.
I first noticed this building ribbons and planers. Very fine line between open and transparent, and sweet but slightly veild. All related to mechanical damping techniques. This was noticeable throughout the range and seems to be related to the hysteresis property of damping materials.
Even in the bass area. The sort of linear spring action of tensioned film bass diaphragms if done well always had a lively dynamic quality at low levels AND I found the same quality to be in many high sensitivity bass cones. I dont think its high sensitivity thats directly causing this. I think that low mass cones with springy low loss surrounds and spyders simply tend to have components that are more linear spring rather than viscous damped in characture and this property can be heard.
Once I did an experiment to try to validate this idea. I took an 8 inch woofer that had a lossy vinyl based foam surround. It was a cheap woofer. Changed the spider out with tensioned threads and coated the surround with a low loss rubber coating. It was immediately obvious the change in the way the bass sounded. It went from sloppy and un dynamic to lively and exciting. The most interesting part was how noticeable it was at even very very low volume holding speaker up to ear to hear!
Some will say you just experienced changes in freq response and thats what your hearing. I cannot "prove" what I suspect, BUT I have built literally hundreds of planer and cone drivers over many years and this phenom seems to be consistent. As I understand it there is a time delay between stress and strain with damping materials. Perhaps this is telling??
I first noticed this building ribbons and planers. Very fine line between open and transparent, and sweet but slightly veild. All related to mechanical damping techniques. This was noticeable throughout the range and seems to be related to the hysteresis property of damping materials.
Even in the bass area. The sort of linear spring action of tensioned film bass diaphragms if done well always had a lively dynamic quality at low levels AND I found the same quality to be in many high sensitivity bass cones. I dont think its high sensitivity thats directly causing this. I think that low mass cones with springy low loss surrounds and spyders simply tend to have components that are more linear spring rather than viscous damped in characture and this property can be heard.
Once I did an experiment to try to validate this idea. I took an 8 inch woofer that had a lossy vinyl based foam surround. It was a cheap woofer. Changed the spider out with tensioned threads and coated the surround with a low loss rubber coating. It was immediately obvious the change in the way the bass sounded. It went from sloppy and un dynamic to lively and exciting. The most interesting part was how noticeable it was at even very very low volume holding speaker up to ear to hear!
Some will say you just experienced changes in freq response and thats what your hearing. I cannot "prove" what I suspect, BUT I have built literally hundreds of planer and cone drivers over many years and this phenom seems to be consistent. As I understand it there is a time delay between stress and strain with damping materials. Perhaps this is telling??
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Viscous damping creates a force that is linear with velocity, meaning that the system is still linear. There must be another explanation.
Static friction is what I presumed it to be, what are the two surfaces? i still think inertia is the right word
Since the TS parameters outline low frequency performance, can they be used select a woofer that conforms to the OPs guildlines? Or do we have to look at other factors like surround and spider material?
Thanks,
I'm surprised at how much easy bass I get from my U frame subs at low volume. Working harder to pressurise makes sense. Also coupling to the air front and back, cancellation doesn't happen as much in practice as in theory
Well im no expert here BUT my guess is that we are looking for low loss surrounds/spiders which will generally result in a Qms well above 1. My guess is that high Qms is a good indicator of low loss mechanical movement
Yes, you are probably right, but the loss associated with hysteresis is such that it increases with frequency, right? If so, I am not convinced it would explain the loss of bass at low volume.
Wild theory: I'm thinking maybe the force on the voice coil is not perfectly perpendicular to the gap, due to imperfections in the winding of the coil. This would cause losses in terms of torque being applied to the cone, in turn resulting in losses in the suspension. Kind of like trying to force in a desk drawer which is out of alignment.
These ideas are very interesting and no doubt there is an element of truth to them, but, and I hate to say it (because I'm not able to do the measurements myself and so, probably consequently, not a huge fan of them 😱) measurements are required else there is no way to be sure what the speakers are doing at low volumes compared to higher ones because of the equal loudness contour of our hearing
Agreed. Is there an easy test someone could outline? Perhaps I can run a few if they are not too complicated. I have limited test equipment. Basically a mic and some drivers and an impedance box if necessary.
Also the 15TBX100 and Alpha 15A have significantly lower Cms values as compared with NE265W-08 and Peerless XXL divers but the Qms values seem to be all kindof close.
Simply measure the response at different levels to start with. I've been trying to find examples of this being done, not getting very far, are we to assume that the response doesn't vary with level?
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