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lukeamdman

(8) Ported Incriminator Audio Judge 21" build

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From what I've gathered from a few other members, that boost at 10hz will be removed the second these Crowsons are installed. 

 

Nah...Just need to keep the subs boosted but the Crowson's not. 2 separate signals FTW.

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Nah...Just need to keep the subs boosted but the Crowson's not. 2 separate signals FTW.

Definitely separate signals.

 

I get plenty of vibration above 20hz, so i may just 25hz LPF these things. Plenty of experimenting to do.

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I settled on an LR2 crossover at the same freq I use as a cross from subs to LCRS. Seamless. To verify, I played back a ton of music I was familiar with changing freq and slope and settled on 100Hz LR2.

 

JSS

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ANNNNDDDD...I'm thinking about this again...

 

Changing the box size, bumping the tune to 15hz, and placing them back to back I can get by with moving the front row forward only 6".  

 

Outside dimensions:

 

36" wide, 28.5" tall, and 30" deep (includes double baffle) is 14.95cu.ft.  Ports: (3) 8.5" x 2.625" about 57" long

 

After driver/bracing/port, net internal is  right at 11.5cu.ft.  With 3kw the port velocity maxes at 24m/s with a 14hz BW3 applied.  First port resonance is just over 100hz, but I'm currently crossing the sealed subs with the Othorns at 32hz so that's a non-issue even if it were much lower.  

 

I'll build one and see how it performs.

 

I was looking at the Cap4000ULF, and these will only give up about 1cu.ft internal, will have less driver displacement, more port volume, and tuned half an octave higher.  

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Sounds like someone needs more Crowsons, or multiple rotary subs.

 

JSS

 

I'm back to where I was with the quad sealed 5400s.  <15hz just doesn't do anything for me on a concrete slab, so I'd rather gain SPL and lower distortion above that.  

 

The Crowsons are awesome so what would I miss by doing this?  

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Sounds like someone needs more Crowsons, or multiple rotary subs.

 

JSS

Who here has ever heard a rotary sub? Or has anyone seen measurements for a rotary sub?

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I don't think the rotary subs are able to be comparatively measured against other subwoofers since they are basically home installations. It would be interesting to see what they can do though, even if in-room. 

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If you setup the Crowsons appropriately on an entire riser, more envelopment is possible.  But given your SPL demands....

 

You may just need to hire Mike Tyson to literally punch your chest as the kick drum hits each time if this keeps up.  Gloves on, of course, to prevent serious trauma.

 

How  much will be 'enough'?  Apparently 150dB does not cut it....but Isaac Hayes may offer some advice:

 

JSS

 

https://www.youtube.com/watch?v=zhe58xORWG0

 

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I'm back to where I was with the quad sealed 5400s.  <15hz just doesn't do anything for me on a concrete slab, so I'd rather gain SPL and lower distortion above that.  

 

The Crowsons are awesome so what would I miss by doing this?  

 

Six inches of room space?  Seriously, your system is capable of absurd levels already, but I know it's not up to me.  :P

 

Just to mix things up: what happens if just replace everything with a bunch of M.A.U.Ls or some other BP6?  I dunno how strong the motor is on your 21s, so I don't know if they'd be up to it, but it might just hit all the right spots.  It could simplify things a bit and give you kind of an ideal mix of horn and ported sound with a high output density design.

 

Edit: re-worded.

Edited by SME

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We tried some modeling of Luke's 21's in that type of cab. Personally I wasn't a big fan of how it looked after inductance effects, etc... Those drivers need a pretty big box for that type of alignment with such a low tuning. Multiply by 8 and it gets out of hand quick.

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We tried some modeling of Luke's 21's in that type of cab. Personally I wasn't a big fan of how it looked after inductance effects, etc... Those drivers need a pretty big box for that type of alignment with such a low tuning. Multiply by 8 and it gets out of hand quick.

 

Does it actually model worse than just the ported box alone?  My impression is that the M.A.U.L. is pretty close to behaving like an LLT at the bottom of its range anyway, but it's a bit bigger than the ported equivalent because of the front-side horn loading.  My thought is that this could still be a net gain if they also replaced the Othorns, which take up a lot of room on their own.  But the question is whether the drivers are up to the task at the higher frequencies and whether the hybrid cabinets could actually replace the Othorns.  It sounds like they aren't.

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In that type of cab the bottom is vented so it behaves similar to a standard vented cab for the most part. In other words drivers that require big vented cabs to tune low will require about the same amount of space for the back chamber. The upper section follows the same types of principles. Drivers which require more airspace to effectively load the cab will require a larger upper section as well in order to realize a decent smooth and non resonant response shape. The cab starts getting really big quickly. If you load a driver into the Skhorn or MAUL and it doesn't have enough motor and /or has a large inductance peak what results is a droopy and nasty response curve that tends to ring. The low end is rapidly rolled off and the upper slot/horn becomes a single peak with a large hump in the middle, rather than a smooth additive response between the vented and slot/horn sections. A little bit of playing with it in HR goes a long way. If you setup a model and derate the BL of the driver you'll see the areas near the resonant peaks drop out and efficiency drops. Luke's drivers have a ton of inductance so putting them in 6th order or TH type cabs is a bit more complicated. Also he was trying to tune super low at 10-12Hz versus 16 or so like the MAUL. This is all IMHO of course YMMV.

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In that type of cab the bottom is vented so it behaves similar to a standard vented cab for the most part. In other words drivers that require big vented cabs to tune low will require about the same amount of space for the back chamber. The upper section follows the same types of principles. Drivers which require more airspace to effectively load the cab will require a larger upper section as well in order to realize a decent smooth and non resonant response shape. The cab starts getting really big quickly. If you load a driver into the Skhorn or MAUL and it doesn't have enough motor and /or has a large inductance peak what results is a droopy and nasty response curve that tends to ring. The low end is rapidly rolled off and the upper slot/horn becomes a single peak with a large hump in the middle, rather than a smooth additive response between the vented and slot/horn sections. A little bit of playing with it in HR goes a long way. If you setup a model and derate the BL of the driver you'll see the areas near the resonant peaks drop out and efficiency drops. Luke's drivers have a ton of inductance so putting them in 6th order or TH type cabs is a bit more complicated. Also he was trying to tune super low at 10-12Hz versus 16 or so like the MAUL. This is all IMHO of course YMMV.

 

58853057.jpg

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In that type of cab the bottom is vented so it behaves similar to a standard vented cab for the most part. In other words drivers that require big vented cabs to tune low will require about the same amount of space for the back chamber. The upper section follows the same types of principles. Drivers which require more airspace to effectively load the cab will require a larger upper section as well in order to realize a decent smooth and non resonant response shape. The cab starts getting really big quickly. If you load a driver into the Skhorn or MAUL and it doesn't have enough motor and /or has a large inductance peak what results is a droopy and nasty response curve that tends to ring. The low end is rapidly rolled off and the upper slot/horn becomes a single peak with a large hump in the middle, rather than a smooth additive response between the vented and slot/horn sections. A little bit of playing with it in HR goes a long way. If you setup a model and derate the BL of the driver you'll see the areas near the resonant peaks drop out and efficiency drops. Luke's drivers have a ton of inductance so putting them in 6th order or TH type cabs is a bit more complicated. Also he was trying to tune super low at 10-12Hz versus 16 or so like the MAUL. This is all IMHO of course YMMV.

 

Thanks for the good explanation.  It makes a lot of intuitive sense.  The higher motor strength and lower inductance, in a sense, give the amp more control over the output of the system in the regions of resonance.

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It's been a minute since I thought about it but Luke had a specific set of dimensional constraints and space to work with. It was a lot of space no doubt but we are talking 8 21's too.

 

Luke did we ever look at only covering the 10-30Hz bandwidth and not worrying about 50Hz on up much? Basically a restricted bandwidth and a 2 way SW system? I wonder if a big 4th order BP covering only 10-30Hz or so might work.

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It's been a minute since I thought about it but Luke had a specific set of dimensional constraints and space to work with. It was a lot of space no doubt but we are talking 8 21's too.

 

Luke did we ever look at only covering the 10-30Hz bandwidth and not worrying about 50Hz on up much? Basically a restricted bandwidth and a 2 way SW system? I wonder if a big 4th order BP covering only 10-30Hz or so might work.

 

I did have space restrictions, and originally we were planning on a 12-13hz tune.  Since adding the Crowsons I've raised my tune requirement to 15-16hz.  

 

"Luke did we ever look at only covering the 10-30Hz bandwidth and not worrying about 50Hz on up much? Basically a restricted bandwidth and a 2 way SW system? I wonder if a big 4th order BP covering only 10-30Hz or so might work."

 

No, I don't think we ever modeled that.  

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I did have space restrictions, and originally we were planning on a 12-13hz tune.  Since adding the Crowsons I've raised my tune requirement to 15-16hz.   

 

It's only 2 or 3Hz but at those frequencies that's a rather big change for the better when working with ports and making them a reasonable length and area.

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It's only 2 or 3Hz but at those frequencies that's a rather big change for the better when working with ports and making them a reasonable length and area.

 

This week I'm planning to build a prototype with 11.5cu.ft net internal and (3) 8.5 x 2.625" ports about 57" in length.  Tune should be somewhere around 15-16hz.  

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Port%20bracing_zps1cielryi.jpg

 

Port%20bracing%20and%20walls_zpsbghs5rht

 

baffle_zpszibfld7x.jpg

 

 

Bracing will be leftover scraps:

 

bracing_zpsz4jqyks4.jpg

 

 

 

Got all the pieces for one box cut today, so all that's left is assembly and flush trimming:

 

20170121_143741_zpszndnnbry.jpg

 

20170121_150629_zpsvswotpgg.jpg

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