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nyt

2x 18" LMS Ultra 5400 in 27 cubic foot 15hz vented enclosure

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These were measured at about 2 meters, a bit over a foot off the ground.  These are the best measurements I'm going to get, since moving this thing around is just insane.

 

Mastic Beach, NY  (Clear/28.5|23F)  H:67%  W:5.0/6.0NNW
 

Hope you appreciate this :)  I'm sure it's not helping my ear infection any :(

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So I'm going to go to home depot now and get some pvc to create a rounded end for the inner port which makes a little noise during high level sine wave testing.  Outer port seems fine, just going to route that.  Then it's time to paint it and build 3 more.

 

I should probably check its not the wires flapping around and making noise first also... might have to snake my gopro around in there with a flashlight.

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Woo, noise is loose bracing.  Need to secure it, sounds great when I put pressure on the side.  This thing is a monster.

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The bracing is fixed and glue is drying.  Hopefully all sounds good tomorrow.  I have to find some duracoat now.

 

rsaRecT.jpg?1

 

I shaved off as much as I could, reglued, put a brad nail in it, then glued another 3" piece on to it, and nailed that piece to the side and to the brace.  Lots of PL.  Should be good to go.

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I think it was too cold for PL.  One other piece of bracing is loose on the back panel.  The good news however, is when i push on it the enclosure is nice and silent even at high levels.  Great success.  I left all the port edges square to see how it would be, and I can say, it is good.

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Nice progress on the turbulent noise front. 

I've not built such a vented design, but man those cross braces in the cabinet, just seem to have such a small amount of surface area at the point of contact. Two of the finest, most powerful sub drivers in the world, pulsing a mammoth amount of stroke/acoustic energy around within that resonant design, it would seem the brace attachment points would warrant a more robust solution.      

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Yep...It can be too cold for PL. Had that happen to me last winter with a project. It doesn't want to set right.

 

Dave is right there is something a little off about the measurements with a much faster roll off down low than would be expected. With a very close mic you will actually see a little steeper than normal 15-18dB roll off due to a proximity type effect in the bass, but you said you were at 2 meters. Could be a reflection from a car or house, a forgotten cal file, EQ, cable impedance mismatch, or high pass filter. It doesn't really matter for the basis of comparing the 2 cabs against each other since whatever it is applies to both, but it would be nice to investigate for future measurement accuracies sake.

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Wasn't a cal file or EQ, those were both accurate.  I used a macbook to a 20' headphone type cable into an rca adapter splitting a channel to an rca to xlr cable into an fp14000.  So no filters, EQs, or other stuff.  Possibly a not accurate mic to spl meter calibration or some reflections or other oddities from being next to my house.  I haven't changed the batteries in my radio shack meter in a while either.  If it was easier to get these measurements, I'd try to take some more with different hardware.  At least I got a comparison to a sealed box, which is pretty much a known quantity at this point.  This thing is a monster.  I ordered 3 gallons of duratex.  Going to paint it and move it inside, then order some more lumber.

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nyt,

 

I'll third the "too cold for PL" experience. I had a joint pull apart on me, it was still gooey the next day.  

 

What did you build them out of? Sort of looks like the Purebond Poplar I've been working with.

 

If it is - watch for voids - I've not come across too many so far, but had a doozie in the middle of my last sheet, it was 3/4" wide, all the way across. 

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There's a 'follow this topic' link to the right of the thread title at the top.  I took some video and some nice 120fps that I slowed down of the ultra at 10hz.  Unfortunately youtube doesn't support 60fps vids properly, so I either need to rehost it or reencode it.

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that's peculiar because the measured martysubs with slot ports came in at about a 20% adjustment factor.  maybe the turbulence around the corner is the difference.  the marty's were just straight slots.

 

the phase goes 180 at the tuning frequency, if i understand that right, so based on your phase response, it looks like you have about a 14hz tuning or so.  do you have a high pass filter engaged somewhere?  something seems a little off.

 

in any case, nice work, as usual.

 

I think part of the reason the martysub tuning came in low was due to the port ending so close to the wall.  Looks like a few more inches of effective port length from that, but I don't think 20%.

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pl needs humidity to cure, irrc. 

 

ah yes. here:

 

WTF, I can't past a URL?

 

anyway.

There is plenty of humidity here in the PNW. We've had rain most of the day, and fog for a few days prior. 

PL's cure rate slows down considerably when it is cold out. From the first sentence of their directions:

 

"Use above 40°F (4°C). "

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It' been above 40F in my garage, possibly by not terribly much overnight, but it has been.  Not a big deal, all is well now.  I'll be leaving my heater on when the next ones cure.

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Lots of stuff about PL adhesive floating around the forums, most of which is not useful info.

 

Polyurethane glue, unlike manufacturer's initial claims, does not bridge gaps and retain its bonding strength. It requires pressure. Without clamping pressure, the foaming (expanding) action will result in a weaker joint and less glue infiltration will happen. If the piece cannot be clamped, use the press-and-shoot method with a brad nailer.

 

Its strong point is that it permeates the wood pores, infiltrates the wood. To aid in this process, have an old Windex-type spray bottle filled with water handy. Spritz the wood to be bonded a few minutes before bonding. This, besides providing the necessary moisture needed for curing, will open the grain and aid the infiltration process. This is not necessary (and not recommended) with MDF.

 

Loctite claims that their "Fast Grab" version of PL Premium is "100% polyurethane". Someone with the time can investigate that claim to vet it because every PU glue I'm aware of contains fillers. These fillers are the reason you see the cracking around the brace in Rob's posted pic of the failed joint. If the Fast Grab version is indeed 100% urethane, it's worth the 2X price they're asking for it.

 

IMO, urethane glues are good to use down to 40 degrees F, but I would not waste my time below that temperature when doing a project like a sub enclosure. If time (and/or itchy ass) requires that you do, just put a small space heater on the area being joined.

 

And, regardless of claims by whomever leave the joint clamped for 24 HOURS, minimum. If you want the joint to "last as long as the materials being joined", wait a day. If you shoot the piece with a nailer, this point is moot.

 

I've been using PL Premium for 15 years, indoors and outdoors, with many different materials, so I've learned the tricks and busted the manny's claims the hard way, but, YMMV and take my advice for what it is… opinions based on personal experience.

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thanks for the info on pl, good stuff. I had nails in some joints that failed. I think between the cold and lack of enough pl and dusty joins it all contributed. I have a 5kw space heater, but I left it too low and it didn't stay on enough. the knob apparently isn't very linear.

 

the next boxes will be a bit better as I won't be setting up bracing through woofer cut outs.

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