subwoofer moving on the floor...

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#22
I've managed to convice myself that going sealed is a good idea 😀

Since the xls's can be put in small boxes I can sort of go "modular" and add more boxes if I don't get enough output. Will probably cost more but small boxes can be hidden away more easily. If I start getting too many modules I can just make a few low ones and hid them under the couch 😛

But now I've started thinking when is the box volume too small for the displacement of the woofer? I seem to remember reading something about 30x the linear displacement one way minimum. For the xls 10" that would make 0.44 liters x 30 = 13.2 liters. Hehe, that's one compact sub!

Putting a little extra room and doing a cube I'd get a cube with the side 26 cm for a total of 17.5 liters. Going 25 mm mdf that would make a cube with a 31 cm side. Would make the weight of the box+sub 14ish kg.

Btw, it seems like I've totally gone offtopic in my own thread...

//edit//
What sort of tricks would that be owdi?
 
#23
Assuming you are using a round vent, make the vent long enough to where it almost reaches the back wall. By leaving about 1/3rd the diameter of the vent clearance, you extend the effective length by around the diameter of the vent. Now place the enclosure close to the wall, leaving the same 1/3rd diameter of the vent clearance, to get the same effect on both ends. If that is not low enough, start adding stuffing to the vent itself (trading effictive length for output). All three 'tricks' can make a 3"x11" vent behave like a 3"x20" vent.

Dan
 
#24
Using the same box size (36 liters) and using a pipe with a 10 cm (4") pipe I would need 1.5 meters without tricks. Still 75 cm (29.5") then with tricks... a bit problematic when one inside wall in the box is 33 cm (13") 🙄

That's why I used a pr. But it's been a long time since I last built a closed box, something like 10 years. But I still fondy remember how the walls shook when playing a 10 or was it a 15 hz tone with that 15" in a sealed box. And how funny we sounded when our voices got modulated with the tone 😀
 
#25
Jarod,

Interesting this with forces, here is my take on this.......

Given that we have a small fairly light sub with heavy moving masses and Element + PR forces simply in one horizontal direction as in your sub JaRoD:
If we add weight non secured on top of enclosure I believe following happens.
Increase of friction against floor and added weight on top. But that added weight will not function as mass once its own friction to box is overcome by moving forces from box.
Its efficiency as mass will also not be as good as it is placed off center the net force axle.
To utilize weight efficient it should have been placed symmetrical and solidly around the net horizontal force axle.
Of course thicker walls and more dense material (heavier box) will do the same with the added benefit of increased stability.

I therefore think that with your current setup there is no alternative than added weight to box and good friction to floor.

With a down firing sub we have no friction against floor to take into account. Force downwards is no problem at least not if floor is reasonably solid. Forces upwards is easily countered with weight.
But as you say that heavy PR moving mass could sag if its mounted downfiring.
 
#26
JaRoD said:
Using the same box size (36 liters) and using a pipe with a 10 cm (4") pipe I would need 1.5 meters without tricks. Still 75 cm (29.5") then with tricks... a bit problematic when one inside wall in the box is 33 cm (13") 🙄

That's why I used a pr. But it's been a long time since I last built a closed box, something like 10 years. But I still fondy remember how the walls shook when playing a 10 or was it a 15 hz tone with that 15" in a sealed box. And how funny we sounded when our voices got modulated with the tone 😀
Click to expand...

A heavily flared 3" port, like this one, should outperform your PR, when the reduction in vibration is taken into account. You may not be able to attain a 22hz tuning, but 25hz should be within your reach.

A 4" vent would be ideal, allowing you to push the XLS 10" to the limits of it's capabilities. As you already calculated, it's not practical.

I've done some experiments with my 10" driver, building the following boxes:

.6 cu. ft. sealed
1.3 cu. ft. vented, tuned to 28hz w/ a 3" vent
1.6 cu. ft. with a 15" PR tuned to 24hz

Of the three, I ended up sticking with the small sealed box. It allowed for the best placement, and didn't shake the house like the PR did. I would have liked to keep the vented enclosure, but vent noise was too big of a problem. I could only do a 1/8" flare on the internal end of the vent, causing all kinds of noise.

Dan
 
#28
Did get lucky and there are 2 xls drivers on the way home to me soon. Got a 10" for 65 euros and a 12" for 40 but the guy thought the 12" was broken, that's why I got it so cheap... He said there's some weird sound when he plays a bit louder. I've had the same thing with my 10 xls when it was crossed at 100 hz and with only 12 db/oct. At 80 and 18 db it works perfectly, I'm guessing and hoping that's the problem with that one.

So I'll be making 2 new boxes for the 10's and I already have a suitable one for the 12.

Might also have to start thinking about an amplifier to rule them all :devilr: Not sure if my nad 912 with 2x30w at 8 ohm is going to cut it 😛
 
#29
Jarod - sorry for the hijack 🙂

AndrewT said:
Hi Owdi,
what is the comparable tuning (resonance) for the sealed cabinet?
Did you use EQ to extend/flatten the response below Fs?
How much extra power and power handling is required, if you went, for the sealed + EQ solution.
Click to expand...

I forget the tuning, it's been a while since I measured it. Somewhere around 30-40hz. No EQ, just set the crossover frequency to 40hz 2nd order on the plate amplifier, then boosted the gain. Integrates well with my vented floorstanders, which alone have little output below 70hz.

The subwoofer is a Blueprint bp1001 (fs 21hz, qts .37, 16.5mm xmax, vas 70l) driver in .8 cu ft. with a 250 watt plate amplifier. The plate amplifier easily bottoms the driver.

Dan
 
#30
Got some 25 mm mdf today and started cutting it up. Took forever to cut through all that thick mdf with a small saw even if it was an electrical one...

These ones will most likely stand still since they should weigh about 15 kg when done and the subs installed. And I'll try to built them as well as I can since I'm hoping they will last for a long time. And if anyone is still reading this, are pro amplifiers any good? I've seen they are very cheap considering how much effect you get. And according to loudspeaker lab I'll need almost 400w to reach xmax at 20 hz :bigeyes: and about 200w to reach xmax at 10 hz🙄
 
#31
Lets see...sub moving, high spl, apartment building...

That's easy.

Your downstairs neighbor is bangin on the ceiling..

Reverse the connections to the sub...that way, the sub stays still, and everything else in the room moves, as nature intended it to be.



Add mass to the sub.

Cheers, John
 
#34
Built a new box using 25 mm mdf and it's total weight is 14.5 kg. I don't use a rp anymore but the box does seem to still vibrate a bit against the floor but I'm sure that's fixable with some rubberfeet of some kind.

Now the weird thing is that I made is sealed but it still has almost exactly the same freqency responce :bigeyes: just a little less loud. Have no idea how or why but I'm happy since the box is about half the size now. It falls about 5db from 80 to 25.
 
#36
There once was a joke - if your speakers move around the floor, just pour some sweet tea under them, in couple of days it will be just fine 😀

Seriously I would consider putting the sub on some really big rubber feet, so that the box is decoupled from the floor, but has enough weight not to make it move around. I think spikes is a bad idea - they increase coupling with the floor and most probably the box will jump on those.
 
#37
I've noticed that I'm getting alot more vibration in furniture and in the floor now that the sub stands on the floor instead of on rubber feet. Have to go look where I can find some cheap rubber feet around here.

Btw, are pro amplifiers like behringer and similar ones any good? Atleast they seem to be cheap compared to how much effect they put out. It's for the subs so they don't have to have great soundquality. Or maybe I should look into building my own amp? Seems like something based on the chipamp lm3886 would be simpleish and probably good enough. Just have to find a cheap amp, heatsinks and a case then...
 
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