Dr Gedees - I'll try to find a sketch (or draw one up myself), but I'm convinced the AL and that sub are not related. It would appear you have simply misinterpretted the post. I posted the bit on the AL to ensure I fully understood it. The subwoofer works how described in my first post.
Mister Twister - you're quite welcome. Sometimes it takes a fresh set of eyes to fully explain things.
Chris
Resurrecting an old thread: There seems to be some patented prior art on the AL principle, among them patent 4076097 and 3,772,466. In these patents, the reference is to an 'augmented passive radiator'.
I have a question to Dr. Geddes if he is still around - earlier in this thread, he claimed that the maximum practical acoustical gain with the AL is 6db, but at the time he also claimed that a doubling of the cone area in the AL gave this 6db, but later amended his latter claim to 3db. My question is whether this amendment also pertains to the maximum practical gain of the AL principle, in his opinion.
I have a question to Dr. Geddes if he is still around - earlier in this thread, he claimed that the maximum practical acoustical gain with the AL is 6db, but at the time he also claimed that a doubling of the cone area in the AL gave this 6db, but later amended his latter claim to 3db. My question is whether this amendment also pertains to the maximum practical gain of the AL principle, in his opinion.
Still around.
The "augmented passive radiator" does in fact work differently than a lever. Same basic construction, but different connections in the system.
I believe that doubling the area would be 6 dB of SPL increase, not 3, so I am not sure what was being said at that point. The maximum "practical gain is about 6 dB - beyond that and the parasitic loses begin to eat up the gain very fast. 3-6 dB is pretty easy to get.
The "augmented passive radiator" does in fact work differently than a lever. Same basic construction, but different connections in the system.
I believe that doubling the area would be 6 dB of SPL increase, not 3, so I am not sure what was being said at that point. The maximum "practical gain is about 6 dB - beyond that and the parasitic loses begin to eat up the gain very fast. 3-6 dB is pretty easy to get.
Hi -
Good to see you're still here.
Doesn't an active driver in both the AL and the APR in their basic forms drive a smaller closed acoustic volume loaded with the small diaphragm end of an AL, with a much larger acoustic volume having considerably higher compliance than the other between the two diaphragms of the AL, with the larger diaphragm end of the AL exposed to the environment, or is that true only for the APR?
Good to see you're still here.
Doesn't an active driver in both the AL and the APR in their basic forms drive a smaller closed acoustic volume loaded with the small diaphragm end of an AL, with a much larger acoustic volume having considerably higher compliance than the other between the two diaphragms of the AL, with the larger diaphragm end of the AL exposed to the environment, or is that true only for the APR?
Btw, I have a couple of questions, if you don't mind me asking. With the AL, is it generally preferable to make the AL moving assembly as light as possible to help transient response?
Also, do AL designs share the characteristic PR out of band 'notch' due to the PR free air resonance frequency?
Thanks in advance for any feedback.
Also, do AL designs share the characteristic PR out of band 'notch' due to the PR free air resonance frequency?
Thanks in advance for any feedback.
In the AL all of the radiated sound goes through the lever creating a level increase in the passband. In the APR this is not the case and there is only gain below cutoff with no gain in the passband - big difference.
The level when operated as a bandpass does not have the notch dip. When opperated as a dual level, it will, But a dual level was shown to be a waste. The second lever doesn't do much and can be replaced by a port which will act just about the same. This is all discussed in the patent. You should read that.
The level when operated as a bandpass does not have the notch dip. When opperated as a dual level, it will, But a dual level was shown to be a waste. The second lever doesn't do much and can be replaced by a port which will act just about the same. This is all discussed in the patent. You should read that.
I always liked this concept. I once thought id actually invented something when i had a couple of similar ideas.
1: I visualised a horn expansion, with several membranes. The added diaphragm mass and air mass combined could be made identical to the equiv horn. Since the diaphragm mass is likely to be greater than air, i considered that the required path length would be reduced. In fairness I was probably using my hind brain that day.
2: In a vaguely similar way to AL, i would like to try a bass Exciter to drive a large panel, or hydraulic cylinder system in reverse. Exciter driving LF at low excursion to cylinder, master output to large membrane at higher excursion. Maybe thats not a great idea either.
1: I visualised a horn expansion, with several membranes. The added diaphragm mass and air mass combined could be made identical to the equiv horn. Since the diaphragm mass is likely to be greater than air, i considered that the required path length would be reduced. In fairness I was probably using my hind brain that day.
2: In a vaguely similar way to AL, i would like to try a bass Exciter to drive a large panel, or hydraulic cylinder system in reverse. Exciter driving LF at low excursion to cylinder, master output to large membrane at higher excursion. Maybe thats not a great idea either.
Hi,
Thanks, I downloaded the patent. But I have a question: Let's suppose we have an AL type dual diaphragm where the larger cone area is exactly double the area of the smaller one (1.4142 times the effective diameter).
Now, if the chambers are properly sized, how would it make any difference in the overall function of the AL if the annular outer half of the larger diaphragm is driven versus the full area of the smaller diaphragm since in either case the same area is driven and the same area is loaded by the other (high compliance) chamber (assuming properly sized chambers for either configuration, and imagining, for the sake of simplicity, that the two diaphragms are connected by a reasonably short lightweight cylinder that is the same diameter as that of the smaller diaphragm and 0.7071 times that of the larger)? After all, the diaphragms are tightly coupled mechanically and the driving and (larger high compliance chamber) internally loaded diaphragm areas are essentially the same in either case.
In both cases, only the relatively negligible displacement of the surround of the smaller diaphragm would affect both the total effective area of the larger diaphragm nominal 'half area' and smaller diaphragm 'full area'. Of course, in both cases the larger AL diaphragm 'sees' the outside world and the smaller AL diaphragm doesn't.
Thanks, I downloaded the patent. But I have a question: Let's suppose we have an AL type dual diaphragm where the larger cone area is exactly double the area of the smaller one (1.4142 times the effective diameter).
Now, if the chambers are properly sized, how would it make any difference in the overall function of the AL if the annular outer half of the larger diaphragm is driven versus the full area of the smaller diaphragm since in either case the same area is driven and the same area is loaded by the other (high compliance) chamber (assuming properly sized chambers for either configuration, and imagining, for the sake of simplicity, that the two diaphragms are connected by a reasonably short lightweight cylinder that is the same diameter as that of the smaller diaphragm and 0.7071 times that of the larger)? After all, the diaphragms are tightly coupled mechanically and the driving and (larger high compliance chamber) internally loaded diaphragm areas are essentially the same in either case.
In both cases, only the relatively negligible displacement of the surround of the smaller diaphragm would affect both the total effective area of the larger diaphragm nominal 'half area' and smaller diaphragm 'full area'. Of course, in both cases the larger AL diaphragm 'sees' the outside world and the smaller AL diaphragm doesn't.
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