Sub positioning, corssovers etc...

[John_C]

My M-audio SBX arrived today

Now i need to find out how the hell i'm gonna use it. Obviously just wacking it in and turning it up makes bob marley sound frickin' awesome, but that's not what i bought it for!

How do you have your sub set up? Do you run everything through it or do you assign it a seperate output and use ITB HP/LP?

What methods did you use for positioning it?

My room is treated, but nowhere near what i would like. I have 3 corners blocked off by 5cm rockwool (the 4th has floor to ceiling wardrobe sitting in it), 5cm rockwool panels either side of the listening position, 5 cm rockwool in front and 10cm directly behind. It sounds a lot better than it did without treatment, and just by ear it sounds pretty flat up to 120hz (120 to 200 is another story though ). Room dimensions are about 3.5x2.7x2.75 m, it's a really small room but it's all I have until july

EDIT: I also scored an EMU ps12 spares and repair of ebay (intermittent fault, sounds like bad connection) which should perform better when fixed as it's 12" and sealed as opposed to the ported SBX. The SBX isn't the new SBX-10, it's the totally different old 8" model

 

[Torniojaws]

There's always the trick of placing the sub where your ears are when listening normally. Then start crawling on the floor and find a spot where the mix balance sounds the best. Place the sub there

 

[John_C]

That's my plan, however i'm not sure how i'm gonna get my sub up to the height of my listening postion!

 

[arv_foh]

I have mine under my desk, drivers aligned approximately with my monitors. Sounds fine to me

 

[John_C]

Yeah i've got it under the desk atm and it sound most even there of everywhere i've tried. What about crossover settings? On the sub itself or ITB?

 

[arv_foh]

I just use the one on the sub.

 

[John_C]

Oh dear...........

not that it surprises me in the slightest, but that is pretty terrible

EDIT: this isn't with a proper measurement mic, it's with a c1000, so the low end obviously tails off more dramatically than it normally would

 

[John_C]

The simply enormous 73.8Hz null is a vertical standing wave, unfortunately seeing as this is a student room I don't think i'm going to be able to get anything up on the ceiling =/

 

[Joematthews]

Hahaha good god, that null is bigger than Pamela Anderson's tits. You'll probably be able to improve it a bit moving it around the room and perhaps raising it off the floor a bit. If not, time for some form of tuned treatment.

edit, I'm wondering whether the directionality of the c1000 isn't helping. I can't find any non-ubersmoothed frequency graphs though.

 

[John_C]

Hahaha good god, that null is bigger than Pamela Anderson's tits. You'll probably be able to improve it a bit moving it around the room and perhaps raising it off the floor a bit. If not, time for some form of tuned treatment.

edit, I'm wondering whether the directionality of the c1000 isn't helping. I can't find any non-ubersmoothed frequency graphs though.

Thanks for the reply. I spent most of today messing around with moving things around, got pretty much nowhere. The c1000s is fine for the job, at least i think so seeing as the difference between
a.c1000 pointing at ceiling
b.c1000 pointing straight ahead
c. sm57 pointed at ceiling
d. sm57 pointed straight ahead
was pretty negligable below 200hz (with the exception of general trends, i'm talking peaks and nulls)

The best response i got from the sub was with it sitting in my lap right behind the test position, completely impractical obviously. Depending on positioning, I got huge dips all over the place, in particular a complete lack of anything between 80 and 100 hz with some sub positions

 

[Force666]

The best response i got from the sub was with it sitting in my lap right behind the test position, completely impractical obviously.

Sounds erotic!

 

[Wolfeman]

Yeah if you aren't using a proper measurement mic, an spl meter, and have your soundcard calibrated, then I wouldn't even look at those graphs. They are lying to you.

 

[John_C]

Yeah if you aren't using a proper measurement mic, an spl meter, and have your soundcard calibrated, then I wouldn't even look at those graphs. They are lying to you.

I know they are lying to me to an extent, except for the fact that I can hear almost everything they show.

The actual spl readings will be off as i haven't calibrated, but that would just give me an offset, i.e. not a problem, the profire 2626 is almost completely flat and both the c1000 and the sm57 gave similar results. I can't see any major source of systematic error *on the small scale*, obv the general roll off from 20-200 will be wrong....have i missed something?

 

[Joematthews]

I think we're deviating from the point here, although your measuring equipment certainly isn't ideal.

If space is at a premium tuned traps is the only way to go I guess, unless you feel like having tons of 8 inch thick traps all over the walls and ceiling.

You could build a helmholtz resonator if you're good at DIY but I've never built one myself so I don't know how hard it would be, and how effective the results are.

Was the null at 74hz a problem before you got the sub?

 

[MarcusGHedwig]

Oh dear...........

Sweet jesus

 

[John_C]

Ok so i fixed the EMU ps12, something had hit the cone and had made the voice coil grind, took it to pieces, realigned everything, glued it all back together and it sounds great. Except that it's ridiculously directional! I always believed in the idea of low frequencies effectively being projected spherically from the speaker, but with this sub a 40Hz sine wave is piss quiet from behind and loud at the front! I have no idea how to position something like this as none of the standard theory/rules of thumb in any way apply!