The ''Lazy'' and ''cost-no-object'' solution would be to throw one or two of these
8W7AE-3 - Car Audio - Subwoofer Drivers - W7AE - JL Audio
and just put some big power in it, with massive EQ boost... But it's far too expensive. And i'm afraid it would still be 28hz-shy (!)
8W7AE-3 - Car Audio - Subwoofer Drivers - W7AE - JL Audio
and just put some big power in it, with massive EQ boost... But it's far too expensive. And i'm afraid it would still be 28hz-shy (!)
In my experience that is a too simple statement to make. While I down want to hang you out to dry, I do wish you could back it up with your experiences.
In the 90s I built a lot of bandpass boxes, convinced that they would be louder. Later I realized that they simply werent. Then I went on to horns...
I have simulated a lot of horns, tapped horns, bandpass, built too many of them, and my opinion is still that you can get high efficiency, but overall output is difficult. At least over any reasonable bandwidth. I had a 200x50x120cm FLH in my living room for a while. Very interesting sound from it, felt massive. But the two 60L bass reflex boxes that replaced it was louder, even if it felt counter-intuitive. They could take more power and that made the difference.
I would love to see any realistic simulations or IRL measurements where a high Xmax, high power handling subwoofer in bass reflex is outperformed by something more exotic of similar size enclosure.
I feel a bit silly for forgetting about the Silver Flute W20RC38-08.
They are perfect for your application. Ends up at 61 liters, but there is fidelity. Not certain I would use anything more than a coil to smoothly transition it over to a good mid, could always just slam a small tweeter/widebander in the middle and call it finished. These will sound much like a sealed box, only with better extension. A bit of dip eq to get the match right, does not use a lot of power, just works.
They are perfect for your application. Ends up at 61 liters, but there is fidelity. Not certain I would use anything more than a coil to smoothly transition it over to a good mid, could always just slam a small tweeter/widebander in the middle and call it finished. These will sound much like a sealed box, only with better extension. A bit of dip eq to get the match right, does not use a lot of power, just works.
Attachments
Last edited:
Interesting but what about the 5mm xmax?
Fs is good but xmax-limited makes me think i will need 2 or 3 per side, am i wrong?
See simulation, it is 2 in parallel in each cabinet. So yes, 2 per side. They are cheap.
An externally hosted image should be here but it was not working when we last tested it.
Directly from the amplifier output, in-between the driver, true rms.
The 80wrms rated amp (8ohms?) Rotel A14 is obviously pushed beyond his max here so i can't wait to try on some massive amplifier but it gives a good idea:
Basically, with the standard 10 inchers i have here it's about 103-105db in-room @ 45hz and power consumption in the 60 watts rms.
In the 25-35hz range, it jumps to 110-140wrms (and the amp clips AND/OR driver xmax is reached, difficult to know which is which to be honest) while having lower SPL output (in-room, at certain mic position) in the low 90db to high 90db.
LS12-44 Dayton i just tried is good at 40-45hz (peaks 106db) but very weak below 40hz...
So basically, as expected, it's very consuming in every aspects when it concerns 20-35hz: amp power, xmax/xmech, box volume. Stressfull mechanically and electrically.
A 2 cu ft 2nd order sealed box with an F3 of 30hz can only be 0.18% efficient (84.55dB).
A 2 cu ft 4th order vented box with an F3 of 30hz can only be 0.36% efficient (87.56dB).
A 2 cu ft 6th order vented box with an F3 of 30hz can only be 0.90% efficient (91.54dB).
Posted by djk (M) on December 14, 2010 at 06:53:43
In Reply to: RE: nope posted by Scholl on December 13, 2010 at 14:46:43:
You don't need any real math to understand what is going on here.
We have a fixed box size and cut-off frequency. Each box requires a different driver to be optimum for the box type (2nd, 4th, 6th). This can be seen as if you would convert a 2nd to a 4th the reference efficiency cannot change, but the 4th would go about 1/3 octave lower.
In theory we should be able to see about a 3dB difference in a 2nd vs a 4th if the box size and cut-off frequency are kept constant (which we do, 84.55dB vs 87.56dB).
What you need to ask is how the 6th can be 91.54dB, an increase of 3.98dB?
The answer lies in the optimum driver having a lower Qts which in turn raises the mid-band reference efficiency, but causes the deep bass to roll off. There is no such thing as a free lunch, and there isn't one here either. The deep bass roll-off is compensated for by the bass boost in a 6th order system, typically 6dB at the box tuning frequency.
That's cheating!
Well, sort of.
Comparing output at Fc (2nd order) vs Fb (4th and 6th order), the 6th order is only about 1dB more that the 2nd order, and is actually 2dB less than the 4th order (low Qts drivers have no low bass). But the mid-band reference efficiency really is 6.99dB more that the 2nd order, or 3.98dB more than the 4th order. The 6dB boost in the 6th order is mainly at Fb and drops off rapidly above there. An octave above Fb the boost has declined to only 1.5dB or so. Distorting is not excessive as the largest boost is at Fb and does not cause excessive cone motion. Levels of F1 in program material tend to be on the order of 6dB~10dB lower than F2 on most musical instruments, so the boost at Fb doesn't eat up all the power on real music.
The 6th order vented system looks to be a free lunch (violate the Iron Law), but as we see, doesn't. Keele's actual examples were for a 2nd order with a 15, 4th order with a 10, and 6th order with an 8!
See example 2 on page 29 of the pdf (which was pg.28 of the actual paper)
From examining various equations for efficiency and LF cut-off I have concluded the optimum driver for the highest efficiency and lowest cut-off would have a Qts=0.312 and be a 6th order system with an Fb=F3=Fs=Faux with the filter (Faux) having a Q=2.
I can address alignment jamming (using non-optimum drivers) if desired.
http://www.xlrtechs.com/dbkeele.com/PDF/Keele%20%281981-05%20AES%20Preprint%29%20-%20Direct%20LF%20Driver%20Synthesis.pdf
A 2 cu ft 4th order vented box with an F3 of 30hz can only be 0.36% efficient (87.56dB).
A 2 cu ft 6th order vented box with an F3 of 30hz can only be 0.90% efficient (91.54dB).
Posted by djk (M) on December 14, 2010 at 06:53:43
In Reply to: RE: nope posted by Scholl on December 13, 2010 at 14:46:43:
You don't need any real math to understand what is going on here.
We have a fixed box size and cut-off frequency. Each box requires a different driver to be optimum for the box type (2nd, 4th, 6th). This can be seen as if you would convert a 2nd to a 4th the reference efficiency cannot change, but the 4th would go about 1/3 octave lower.
In theory we should be able to see about a 3dB difference in a 2nd vs a 4th if the box size and cut-off frequency are kept constant (which we do, 84.55dB vs 87.56dB).
What you need to ask is how the 6th can be 91.54dB, an increase of 3.98dB?
The answer lies in the optimum driver having a lower Qts which in turn raises the mid-band reference efficiency, but causes the deep bass to roll off. There is no such thing as a free lunch, and there isn't one here either. The deep bass roll-off is compensated for by the bass boost in a 6th order system, typically 6dB at the box tuning frequency.
That's cheating!
Well, sort of.
Comparing output at Fc (2nd order) vs Fb (4th and 6th order), the 6th order is only about 1dB more that the 2nd order, and is actually 2dB less than the 4th order (low Qts drivers have no low bass). But the mid-band reference efficiency really is 6.99dB more that the 2nd order, or 3.98dB more than the 4th order. The 6dB boost in the 6th order is mainly at Fb and drops off rapidly above there. An octave above Fb the boost has declined to only 1.5dB or so. Distorting is not excessive as the largest boost is at Fb and does not cause excessive cone motion. Levels of F1 in program material tend to be on the order of 6dB~10dB lower than F2 on most musical instruments, so the boost at Fb doesn't eat up all the power on real music.
The 6th order vented system looks to be a free lunch (violate the Iron Law), but as we see, doesn't. Keele's actual examples were for a 2nd order with a 15, 4th order with a 10, and 6th order with an 8!
See example 2 on page 29 of the pdf (which was pg.28 of the actual paper)
From examining various equations for efficiency and LF cut-off I have concluded the optimum driver for the highest efficiency and lowest cut-off would have a Qts=0.312 and be a 6th order system with an Fb=F3=Fs=Faux with the filter (Faux) having a Q=2.
I can address alignment jamming (using non-optimum drivers) if desired.
http://www.xlrtechs.com/dbkeele.com/PDF/Keele%20%281981-05%20AES%20Preprint%29%20-%20Direct%20LF%20Driver%20Synthesis.pdf
Do note that as my sims are in halfspace (2pi), at the lowest frequencies (28hz) you might get 107db max pending on room modes. This is why I always sim with 2pi, because sometimes the room modes f*** up the response and you get dips and peaks all over, and it's easier to use dip eq than trying to catch up with tons of power.
The port is front firing, and if you place it close to the back wall near the floor, you may get 107db's at 28hz, if you're lucky with the room.
The port is front firing, and if you place it close to the back wall near the floor, you may get 107db's at 28hz, if you're lucky with the room.
Kaffiman, i understand but unfortunately 90 liters is quite big for this project, even if i use 10mm thick bamboo i still can get anywhere near such a big volume.
As i understand, there is no way to get some serious first octave with limited cabinet volume, even with EQ and ''unlimited'' power...
:-(
Well, there is in fact: by using some massive drivers with unusual Xmax and the price that comes with it... But that's hardly a solution in this project.
As i understand, there is no way to get some serious first octave with limited cabinet volume, even with EQ and ''unlimited'' power...
:-(
Well, there is in fact: by using some massive drivers with unusual Xmax and the price that comes with it... But that's hardly a solution in this project.
Jon,
Since you seem to be of the opinion that you don't "hear" below 20 Hz, you "feel" it, and space is limited for you, why not use tactile transducers below 30 Hz? Simply bolt them to your chair, or piece of plywood, and "shake your booty" (the first popular tactile transducer was the "Buttkicker") down to the single digits with relatively little power.
An advantage of tactile subwoofers is they are only felt by the intended audience, your neighbors won't complain of windows flapping while your body feels the equivalent of 150 dB 7Hz rotor blade noise, or earthquakes, explosions or the 8 Hz note of a pipe organ. Another advantage is the room has no effect on the output, no location based room modes and nodes effecting output and perception.
Anyway, if I liked the "feel" that's what I'd go for, but as it is, when I hear an air handling duct resonating below 20 Hz, I look for another place to sit.
Cheers,
Art
Since you seem to be of the opinion that you don't "hear" below 20 Hz, you "feel" it, and space is limited for you, why not use tactile transducers below 30 Hz? Simply bolt them to your chair, or piece of plywood, and "shake your booty" (the first popular tactile transducer was the "Buttkicker") down to the single digits with relatively little power.
An advantage of tactile subwoofers is they are only felt by the intended audience, your neighbors won't complain of windows flapping while your body feels the equivalent of 150 dB 7Hz rotor blade noise, or earthquakes, explosions or the 8 Hz note of a pipe organ. Another advantage is the room has no effect on the output, no location based room modes and nodes effecting output and perception.
Anyway, if I liked the "feel" that's what I'd go for, but as it is, when I hear an air handling duct resonating below 20 Hz, I look for another place to sit.
Cheers,
Art
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.