Thank you Matthew Morgan for your keen interest and enthusiasm. The latest development is that the Faital driver is no longer available from my sources.
Although the 18LW2400 is only 2/3 of the cost of 18SW115-8, the latter is certainly the better driver. So going with the 18SW115-8 (4 ohm is not readily available, but can be specially ordered), you can help with a Symmetrical, 8th Order Super Planar Sub Cabinet.
By the way, I was referring to the length and not the depth, while suggesting 54" as a maximum. But looking at the Symmetrical layout, I assume that more depth will allow a longer path. Anyway, you are the best judge.
This is not meant for home use but for outdoor PA work. These will be powered by XTi6002s and QSC RMX 1850, 2400 amps.
A lower response of 30 Hz would make it suitable for almost all genres of music.
Thank you once again.
Although the 18LW2400 is only 2/3 of the cost of 18SW115-8, the latter is certainly the better driver. So going with the 18SW115-8 (4 ohm is not readily available, but can be specially ordered), you can help with a Symmetrical, 8th Order Super Planar Sub Cabinet.
By the way, I was referring to the length and not the depth, while suggesting 54" as a maximum. But looking at the Symmetrical layout, I assume that more depth will allow a longer path. Anyway, you are the best judge.
This is not meant for home use but for outdoor PA work. These will be powered by XTi6002s and QSC RMX 1850, 2400 amps.
A lower response of 30 Hz would make it suitable for almost all genres of music.
Thank you once again.
A flat 30 Hz response is quite brutal. Every time I hear clean bass below 35 Hz at levels above 125 dB I feel nauseous and dizzy. Tapped horns tuned that low usually get a very heavy and sluggish character that is difficult to correct with DSP.
My first ROAR-prototype is tuned to 33 Hz and it almost unusable, even though it has a great mid bass peak and punch. It tends to overwhelm everyone listening to it. It is fun to hear the pure overwhelming energy rattle everything and making your pants flap against your legs, but its a bit to overwhelming to listen to for extended periods of time.
One Swedish guy who built a hometheater sub based on the ROAR concept (large front resonator) with a B&C 12TBX100 fooled his wife that there was a helicopter hovering above their house.
Even though it is tuned to 35 Hz he has a very powerful and energetic response down to 10 Hz indoors.
These front resonator enhanced quarter wave designs does not behave like normal tapped horns or FLH. Everyone who hears them comments on their very physical and tactile quality. My ROAR12 tuned to 45 Hz used indoors makes people feel sick whenever we disable the highpass filter. It makes a great home theater sub, even though it has a 45 Hz simulated lower knee in the passband.
I would recommend a 38 - 45 Hz tuning for a B&C 18SW115-8. Raw efficiency is usually much more usable then the last few Hz of extension.
If you stack several SuperPlanar horns or ROAR18 you gain those few Hz of extension back without the penalty of lower efficiency or large unwieldy boxes.
Regards,
Johannes
Directivity and pattern? These are completely irrelevant concepts in a sub that will spend its life sharply crossed over below 100Hz. Specialty cardoid sub designs or steered arrays of subs are tools for a different discussion. Midrange and high frequencies yes. Dedicated subwoofers no.
Hoffman's law is said to be an "iron" law for good reason. You want something that performs better, weighs less, goes as low and is the same size. You have to give something up. Usually size and extension. There is no free lunch.
Effects and curiosities
Johannes and Josh, that is great advice about the tunings!
and Johannes, those are some VERY interesting observations about effects ....
In post #163 you state that these designs are able to produce some useful output well below their tuning .... How do you suppose this works?
...... If the cabinet's tuning (Fb) is 35hz then would our output at 10hz be similar to what you might get from a simple Open Baffle with same driver? Or do you believe that there is more to it than that based upon your observations? If so do you have any theories on this?
Forgive me if i sound at all skeptical but i am just asking questions because i am sincerely curious
.
Some sort of loading taking place that far below Fb would certainly be an intriguing development and a pleasant surprise!
Johannes and Josh, that is great advice about the tunings!
and Johannes, those are some VERY interesting observations about effects ....
In post #163 you state that these designs are able to produce some useful output well below their tuning .... How do you suppose this works?
...... If the cabinet's tuning (Fb) is 35hz then would our output at 10hz be similar to what you might get from a simple Open Baffle with same driver? Or do you believe that there is more to it than that based upon your observations? If so do you have any theories on this? Forgive me if i sound at all skeptical but i am just asking questions because i am sincerely curious
.Some sort of loading taking place that far below Fb would certainly be an intriguing development and a pleasant surprise!
Samuel's 8th Order Super Planar
No problem Samuel and yes I was planning on going with the stepped variant design inpired by the ROAR from Johannes and Martinsson... I am thinking i may just start calling the new style "8th Order Super Planar" to keep the name simple (and the old style Super Planar would be 6th order) .....
According to what Johannes is saying the subjectively useful output indoors extends well below the fundamental tuning of the cabinet (Fb) so even if we tune far down as low as the Driver's Fs value (which is the very low end of what is advisable, but we can make it work) you will get absolutely and unquestionably solid response to 30hz as i would expect in a traditional sense but you may also have some amount of perceivable output well below that! ............If this is the case then the result would be a cabinet that shall not only be useful for all music but also effective for watching movies! A wonderful multipurpose subwoofer
No problem Samuel
and yes I was planning on going with the stepped variant design inpired by the ROAR from Johannes and Martinsson... I am thinking i may just start calling the new style "8th Order Super Planar" to keep the name simple (and the old style Super Planar would be 6th order) .....According to what Johannes is saying the subjectively useful output indoors extends well below the fundamental tuning of the cabinet (Fb) so even if we tune far down as low as the Driver's Fs value (which is the very low end of what is advisable, but we can make it work
) you will get absolutely and unquestionably solid response to 30hz as i would expect in a traditional sense but you may also have some amount of perceivable output well below that! ............If this is the case then the result would be a cabinet that shall not only be useful for all music but also effective for watching movies! A wonderful multipurpose subwoofer
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Here is the simulated impedance for my ROAR12 with a B&C 12PS100. It is tuned to 45 Hz.
The frontresonator adds a lot of mass to the driver and lowers the Fs substantially.
A ROAR12 standing in a corner indoors still have a simulated efficiency of 101.8 dB/w/m at 33 Hz.
The ROAR-inspired home-theater sub rattled his house when he was running frequency sweeps from 10 Hz and up. The 10 - 20 Hz spectrum might have excited higher harmonics. I don't really know. I have not heard that sub.
I know my large 33 Hz tuned 212 ROAR-prototype plunges the depths with ferocity, but I don't have any hard facts or measurements to back this up. It has the lower impedance peak at 23.6 Hz. It seems like the straight non-expanding sections behave quite different then expanding horn sections.
Cheers,
Johannes
I would be extremely surprised if the output is useful any further below tune than any other system not using a closed air volume on one side of the driver. In my opinion and experience you may get a useful 1/3rd octave below tune. Perhaps 2/3rd octave or a bit more in a smaller indoor setting. If the tuning is 40Hz you could expect some useful amount of output to maybe 31.5 to 35Hz outdoors. Indoors possibly a bit under 30.
The modeling of these or any other system where the back wave is resonant will bear this out. Excursion gets out of control below tune, power handling is low, response drops off a cliff and distortion shoots through the roof. High resolution controlled measurements will back this up if they are taken.
The modeling of these or any other system where the back wave is resonant will bear this out. Excursion gets out of control below tune, power handling is low, response drops off a cliff and distortion shoots through the roof. High resolution controlled measurements will back this up if they are taken.
Did the double wall construction eliminate the need for bracing around the mouth?
I really like the stepped TH design tho'!
C/E/X PA Flat to 30 (FT30) PA TH Awesomeness
Can the 8th order Planar Sub match or do better than the performance as linked above, with the same B&C 18SW115-8 driver? I am ready to bite the bullet, either way. I will build both cabs for proof of concept before committing to making a stack of 4 or 6 cabs. Thanks.
Can the 8th order Planar Sub match or do better than the performance as linked above, with the same B&C 18SW115-8 driver? I am ready to bite the bullet, either way. I will build both cabs for proof of concept before committing to making a stack of 4 or 6 cabs. Thanks.
Yes. The 8th order Planar sub and the TH equivalent ROAR18 has a larger usable bandwidth and more output.
I don't want post any simulations since the 8th order Planar Sub is not my design, and this thread is not about my ROAR design. I only mention the ROAR design since it shares a lot of characteristics with the super planar designs.
Regards,
Johannes
I looked at your link but didn't notice measurements, only sims. Can you provide links to the "performance" that impressed you?*
B.
*I'm still hoping somebody will link to ROAR measurements too. Some people seem to think theoretical sims are a trustworthy substitute for measurements.
Yes. just a guy seems to think that Hornresp is quite accurate:
Considering that Hornresp does not account for bends in the horn path, flexing horn-walls, turbulence around sharp edges at high spl, room acoustics (which usually change the response curve a lot more then small changes in the simulation) changes in Bl within the stroke of the driver, differences between different batches of drivers etc, I see the Hornresp sims as close enough for a reliable indication of expected performance.
The most important factor is the real life performance, and this is not a statical condition which adheres to a simulation. The response will change dramatically dependent on operating conditions, processing, the acute condition of the driver (changes gradually over the whole lifetime of the driver) and many other factors.
I have posted measurements of my ROAR12 in the ROAR18 thread.
I will take new measurements once I get my ROAR back. My friend Anders Martinsson has it on loan at the moment.
Regards,
Johannes
Found it. Thanks. Esp nice to see measurements (even measurements tight up against the drivers) compared to the sim. Very close, provided you sit within a meter of the speaker.
But the FR (even just eyeballing the main sub passband and ignoring the weird upper range and rarely-posted distortion figures) does not seem great for a large driver and that much carpentry effort and the appearance of upper-range weirdness. Is it the loudness or box size that you and OP of this thread are proudest of?
Aside from the fun we all have from experimenting with speakers, I have trouble seeing the practical benefits of trick 6th-order or quarter-wave-resonator boxes as compared to the orderly and lower distortion sound results of sealed mounting or even large baffles.
B.
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Here is the simulated groupdelay for the ROAR18 (black trace) and for the FT30 tapped horn (gray trace).
The ROAR18 has a peak in the groupdelay curve of 33 ms at 137 Hz effectively ending the useful passband there. The FT30 has a 42 ms peak at 114 Hz, effectively ending the useful passband at that point.
I agree that tapped horns have a more limited useful frequency response compared to Super Planar 6th or 8 order quarter wave resonators or similar designs.
Efficiency.
Regards,
Johannes
If "efficiency" means these complex carpentry efforts can get extra loud sound from a given driver, then it might be a valuable feature for auditoriums and Green Bay Packers (American football) stadiums, the natural home for quarter-wave-resonator speakers.
But if it means smaller amps needed for a given loudness, then hardly an advantage in these days of cheap class-D and DSP amps.
So I remain puzzled over the net benefit of making this complex choice, aside from the legitimate fun of experimenting.
B.
That's because it's proven that if you accurately sim what you build the sim will match the measurement.
In the case of the ROAR series, unfortunately accurate sims were not done though.
What do you think your beloved K horn was? It's a complex multi resonant enclosure that has frequency response much worse than the ROAR.
Why don't you stop littering all the threads with complex enclosures? You've never heard a tapped horn, don't know how they work and are inexplicably biased against them (considering your beloved K horn).
The ROAR series are not good designs but that doesn't excuse your constant thread derailing against an alignment you've never even heard.