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Author Topic: Lightweight Rock & Roll subwoofer, what have I overlooked?  (Read 7672 times)

Roland Clarke

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Re: Lightweight Rock & Roll subwoofer, what have I overlooked?
« Reply #80 on: November 02, 2019, 05:16:14 am »

Option for wheels or no sale.

Problem with subs is there is no substitute for cubic inches, thus weight.
And when you have to carry 100 pounds of sub, why not get a 18" which is about the same weight, but usually has more potential. It is no coincidence there are very few 12" subs that made it into the rock'n'roll world. The ones that did are all (both?) 100+ lb units.

I honestly don't get why a lot of people keep asking for affordable, small, light subs which can do the same as a decent 18". There aren't any. Heck, it is hard enough to find a decent sounding 18". If you have a logistics problem, i suggest you solve that first.

Its a bit like the argument for large engine cars, no replacement for displacement, but there are a few speakers that do remarkable things given their size and weight.  Danley have a few and there is a recent addition from aura audio which is small, lightweight, 4 x 12 faital pro drivers which is truly awesome and for shows with less than 1000 people, ample in my personal opinion.
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Steve Litscher

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Re: Lightweight Rock & Roll subwoofer, what have I overlooked?
« Reply #81 on: November 06, 2019, 01:57:28 pm »


I honestly don't get why a lot of people keep asking for affordable, small, light subs which can do the same as a decent 18". There aren't any. Heck, it is hard enough to find a decent sounding 18". If you have a logistics problem, i suggest you solve that first.


Jeff from JTR just announced a 2x15 sub that performs identically to his C218 Pro subs (27Hz +/-3dB, 138dB output). It's slightly larger than the 2x12 cabinet that he has, and weighs around 100-lbs. Has tilt-back casters and can be ordered as passive or active.

I had a chance to hear it last week. It's a game changer.

Mark Wilkinson

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Re: Lightweight Rock & Roll subwoofer, what have I overlooked?
« Reply #82 on: November 07, 2019, 04:20:31 pm »

This thread put a bug up my butt to try to build a really light sub...well that, and the fact all my subs are either double 18"s, or Labhorns, or Orbitshifters.

I have single boxes for the drivers in my double 18"s, and they work super...other than their 91lbs is still much for me to want to lug..
I could build a lighter box for the 18"s (bms18n862), but they already walk around when cranked. 
That's about the only real problem with today's large and heavy voice coils, high power, high xmax drivers, i think....they demand weight
 
Started to try a push-push opposed, dual 12" sub, just to counter sub walking, but so far weight keeps climbing unacceptably.
Then I saw the 18" Faital Pro 18FH500 weighs a mere 10 lbs.       ( 99dB 1W/1m, 600W AES, 9mm xmax, 30Hz fs.)
So, I'm like how light can I make a single 18" that gets close to 40Hz....especially when I see I can do it for about $325 per sub.

It's ended up all in at 58 lbs.  1/2 baltic birch.  22x22x27
I measured deflection of equal wall length pieces of 1/2, 5/8, and 3/4 BB with a dial indicator, and was surprised to see less deflection difference than expected.
So with good bracing, which is much more effective than thickness, I figure a lack of weight to counter walking is the only real downside with 1/2"...for this sub...
.....because this is a more old school, high sens, less xmax, less coil weight design, ....so hoping it doesn't walk bad.
So far, pushing about half looks good, although I haven't really cranked it yet.

Wanted to get measurements and processing in place (along with limiters of course) before cranking.
Just finished measurements and processing...

Red trace below is raw, 4m out in the yard.
Green is IIR processing (without latency) I'll use for live.
And purple is FIR processing I'll use for playback. I find playback riskier than live down low, so I roll it off steeper.  Same thing on the high end, but that's more to be able to roll of the low-mid driver faster.
I forgot to hit Delay Finder on the green IIR trace....it's phase curve should bottom close to zero degrees, if done.

Happy to see the porting got me close to the 40Hz f3 goal, and that little boost was need to fill in response.
Sensitivity measured to spec...getting 99-100 dB with either processing in place.
By the stupid SPL numbers the industry uses, that should equal 127dB cont, 133 pk.   Yeah, right  ::)

Now, if it does walk, here is something a little goof ball.  I made a coupler to connect two subs so they face each other in push-push fashion.
My push-push double 18"s, and labhorns with opposed drivers, don't walk, ...and vibration is greatly reduced.

Time to set some limiters and try them in anger....gotta see how this lightweight driver holds up... and try out the coupler.

 

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Don Davis

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Re: Lightweight Rock & Roll subwoofer, what have I overlooked?
« Reply #83 on: November 08, 2019, 04:57:44 pm »


Now, if it does walk, here is something a little goof ball.  I made a coupler to connect two subs so they face each other in push-push fashion.
My push-push double 18"s, and labhorns with opposed drivers, don't walk, ...and vibration is greatly reduced.

Time to set some limiters and try them in anger....gotta see how this lightweight driver holds up... and try out the coupler.

Mark as usual your work is top notch. A question on the push-push set up, only because I have no experience at all with that type of deployment, do you flip the polarity of one of the boxes to avoid cancellation?

Don
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Mark Wilkinson

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Re: Lightweight Rock & Roll subwoofer, what have I overlooked?
« Reply #84 on: November 09, 2019, 07:55:10 am »

Mark as usual your work is top notch. A question on the push-push set up, only because I have no experience at all with that type of deployment, do you flip the polarity of one of the boxes to avoid cancellation?

Don

Hi Don, thanks.

Push-push is where the cones move towards each other, both driven with the same polarity. This would be in a 'clam shell' configuration, with the cones facing each other.
Or, the coils could be back to back, and both cones would move outward together.

The moving masses largely cancel out, at least on symmetric waveforms, and greatly reduce cabinet vibration. 
Cleans up the sound from that reduction too, I find.

I guess most modern high-power 18" drivers have coils in the 1/2 lb vicinity. It's amazing to me that they can oscillate that much mass so many cycles per second.
As mentioned, the driver in my lightweight subs was chosen because it's a lower mass, less power design, but has good sensitivity, and decent power handling.
 
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John Halliburton

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Re: Lightweight Rock & Roll subwoofer, what have I overlooked?
« Reply #85 on: November 16, 2019, 07:26:44 am »

Hi Don, thanks.

Push-push is where the cones move towards each other, both driven with the same polarity. This would be in a 'clam shell' configuration, with the cones facing each other.
Or, the coils could be back to back, and both cones would move outward together.

The moving masses largely cancel out, at least on symmetric waveforms, and greatly reduce cabinet vibration. 
Cleans up the sound from that reduction too, I find.

I guess most modern high-power 18" drivers have coils in the 1/2 lb vicinity. It's amazing to me that they can oscillate that much mass so many cycles per second.
As mentioned, the driver in my lightweight subs was chosen because it's a lower mass, less power design, but has good sensitivity, and decent power handling.

A more practical approach for PA rigs would be to latch them back to back, or side to side(obviously mounting inputs on a recessed panel on accessible sides in mirror image configuration), and eliminate the fancy cage over the driver.

Just a thought.

Best regards,

John
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Mark Wilkinson

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Re: Lightweight Rock & Roll subwoofer, what have I overlooked?
« Reply #86 on: November 16, 2019, 10:21:53 am »

A more practical approach for PA rigs would be to latch them back to back, or side to side(obviously mounting inputs on a recessed panel on accessible sides in mirror image configuration), and eliminate the fancy cage over the driver.

Just a thought.

Best regards,

John

And a good thought  :)

I did the back to back thing on a prior pair of single 18"s and it worked well for force cancellation, but I had some wonky response issues at the top of the spectrum.
I guess center to center spacing, which was 5ft given the depth of the subs was a problem.

I thought about making shallower subs to solve that back to back coupling issue, but ultimately decided i wanted to be able to stack the subs, as well as lay on ground.

I love avoiding a stand for mains when possible.
Need to make the coupler about 6" higher i think.  Will only take a morning's work.
It's not letting all the driver area and ports give me the full +6dB I get side by side on ground.
Plus it will put the new synergy I'm building a little higher in the air !
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Rory Buszka

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Re: Lightweight Rock & Roll subwoofer, what have I overlooked?
« Reply #87 on: Yesterday at 08:26:02 am »

there is a recent addition from aura audio which is small, lightweight, 4 x 12 faital pro drivers which is truly awesome and for shows with less than 1000 people, ample in my personal opinion.

Together with a friend, I built a subwoofer in 2009 that uses the principle that Aura Audio seems to have obtained a patent upon, which appears to be an added mass element at the end of the tapped horn which trades a bit of broadband efficiency for a slightly lower corner frequency for the available path length. I called it a Mass-Loaded Tapped Horn, and it was later independently "invented" again by someone on DIYAudio.com as the mouthful "MLT-TQWP". (I decided it was of limited value because it tended to sound more resonant and less "defined" than a tapped horn, and it was easy to overdo things with the mass element, so no more have been built and I passed up the opportunity to buy one of the prototypes.) However, some of the other implementations by Aura Audio would appear to infringe on the Danley patent because they appear to be using a horn mouth that is substantially open and not providing significant acoustic mass. This is where patents get tested, as they are only worth what a company will spend to defend them in court. I believe Danley already has products in production that could serve as prior art to invalidate Aura's patent, and place them in legal jeopardy of infringing on the Danley patent.

https://patents.google.com/patent/US9014408B2/

« Last Edit: Yesterday at 11:13:31 am by Rory Buszka »
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Re: Lightweight Rock & Roll subwoofer, what have I overlooked?
« Reply #87 on: Yesterday at 08:26:02 am »


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