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Old 22nd June 2011, 07:00 PM   #1
uglykid is offline uglykid  Denmark
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Join Date: May 2009
Default i need some help about subīs for mobile disco

hi all.

i have a little problem about subīs for my mobile disco. i have a little/medium mobile disco and my problem is that then i am out and play to a party, have i many times notice that i have more/lots of bass behind the speakers than on the dancefloor, i have tried many types of subīs (DIY) bassreflexs-bandpass-look and like x1īs but all with more or less same results, but i have never tried a horn construction, so my question is (i now itīs difficult to say exactly) but will a couple sub horn perhaps help me to get more bass on the dancefloor?? i am not a bassfreak but i like a good punch the musik i play is all kind of stuff so i need a good allround sub and i dont need extremly high output, my topspeakers are fullrange and i use electronic crossover, i normally cut the sub about 80-and max 120hz, my sub amp is qsc plx-3002. i will also mention the different places i play i normally have the speaker setup about 1 to 1,5 meters from the backwalls and one thing more iīve have not very much place in my car for big subwoofers

the tham15 and the ss15 looks pretty nice for my needs but again, will they help me?? my woofers now is eminence kappa 15lfa and can i perhaps use them??

and sorry if my english is bad..

uglykid..
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Old 22nd June 2011, 07:50 PM   #2
jbell is offline jbell  United States
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The kappa 15lfa models with almost exactly the same response profile as the 3015lf that the ss15 was designed for. However the lower 5.5m xmax of the 15lfa would make me want to limit to less than 63volts, probably closer to 40volts.

You must run a high pass on the ss15. If you don't have a high pass, don't run it hard. (or at all)

If you are really 1 - 1.5 meters away from a wall, you are probably getting a null or suckout at a frequency that lines up with your distance to wall. General rule, 2meters or more, or tight against the wall for subs.

For reference, here's the directivity test I did for the ss15. Yes it has directivity, where a reflex cabinet does not.
Click the image to open in full size.

Last edited by jbell; 22nd June 2011 at 07:54 PM.
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Old 22nd June 2011, 08:09 PM   #3
HK26147 is offline HK26147  United States
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Quote:
Originally Posted by uglykid View Post
... my problem is that then i am out and play to a party, have i many times notice that i have more/lots of bass behind the speakers than on the dancefloor, i have tried many types of subīs (DIY) bassreflexs-bandpass-look and like x1īs but all with more or less same results, ....
This implies that you have substantial distance between the bass cabs and back boundary.
That can be a setup for uneven response and cancellation.

Kudos to Jim for the directivity chart.
( wish some would have an epiphany when it comes to bass directivity )
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Old 22nd June 2011, 09:15 PM   #4
uglykid is offline uglykid  Denmark
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hi jbell.

thanks for your answers.


in my research i have notice that the 3015lf and kappa 15lf have almost the same TS data except the Xmax and i hope that i could use them in a horn cabinet if this could help me and if you mention not push the driver to hard. i can use highpass at 20hz on my crossover and 30hz or 50hz on the amp right now i use the 30hz highpass. then you say use it about 63v or probely 40v do you so meen 63v/8ohm=7,8A*63v=496w??

then i say 1 to 1.5 meter from backwalls, ok its mayby 1 meter max but yes i know itīs bad īi use the subs as stand for the topspeakersī i have sometimes the options to put my subs into a corner and then there is good sound on the dancefloor but again it dosent happens so many times. the different roomīs i play in is normally about 100 to 400 m3 and about 30 to 100 people so again i dont need extrem output.

ok i think i will plug the skillsaw in the outlet and try making a couple of your ss15 and cross my fingers
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Old 22nd June 2011, 09:22 PM   #5
uglykid is offline uglykid  Denmark
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hi jbell.

thanks for your answers.


in my research i have notice that the 3015lf and kappa 15lf have almost the same TS data except the Xmax and i hope that i could use them in a horn cabinet if this could help me and if you mention not push the driver to hard. i can use highpass at 20hz on my crossover and 30hz or 50hz on the amp right now i use the 30hz highpass. then you say use it about 63v or probely 40v do you so meen 63v/8ohm=7,8A*63v=496w??

then i say 1 to 1.5 meter from backwalls, ok its mayby 1 meter max but yes i know itīs bad īi use the subs as stand for the topspeakersī i have sometimes the options to put my subs into a corner and then there is good sound on the dancefloor but again it dosent happens so many times. the different roomīs i play in is normally about 100 to 400 m3 and about 30 to 100 people so again i dont need extrem output.

ok i think i will plug the skillsaw in the outlet and try making a couple of your ss15 and cross my fingers
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Old 22nd June 2011, 09:27 PM   #6
jbell is offline jbell  United States
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yes use your amps 30hz high pass, and keep it under 250watts (44volts) and you will be happy. Since it sounds like you have a pair of them, I don't think you'll be pushing too hard with these.

Putting ss15's on their side works really well (better than upright) and you can put a pole socket in the side of the ss15's for your tops. That'll make a nice stable base, and allow you the pole option to get your tops up as high as you need.

Do pull your subs away from the wall just a bit farther, and it'll help prevent a suckout or null in the bass frequencies.

I was just running a few tests to answer a question in another post... 125db with 100watts from a single 50lb cabinet still makes me smile.

thanks for the compliment syd... It means something coming from you.
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Old 23rd June 2011, 01:55 PM   #7
60ndown is offline 60ndown  United States
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Quote:
Originally Posted by uglykid View Post
my problem is that then i am out and play to a party, have i many times notice that i have more/lots of bass behind the speakers than on the dancefloor, .
the Karlson works well for this in my experience, only yesterday i was playing some music quite loud, when i went behind the speaker the bass was reduced about 60 or 70%.

http://www.diyaudio.com/forums/subwo...rectional.html
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Old 23rd June 2011, 02:10 PM   #8
HK26147 is offline HK26147  United States
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I figured there would be a prior thread on directionality of bass...
On some forums: the "rule" is that bass is omnidirectional - yet no specific frequency is stated for the transition to directionality.
I believe the confusion lies with the limits of human direction perception NOT physics.
Historically there are several bands whose sound crews had their tricks for managing bass propagation.
From experience, I knew that forward perception on bass cabs was not merely perception of "harmonic distortion".
Hopefully if the next round of shootouts goes off there would be an opportunity to test directional control.

The nature of the OP venue was not specified but:
Quote:
bout 100 to 400 m3 and about 30 to 100 people so again i dont need extrem output.
Is small and is probably dominated by room modes.

Last edited by HK26147; 23rd June 2011 at 02:14 PM.
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Old 23rd June 2011, 02:24 PM   #9
tb46 is offline tb46  United States
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Hi jbell,

Did you ever get around to doing something like a polar plot for the SS15?

Regards,
__________________
Oliver
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Old 23rd June 2011, 02:47 PM   #10
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by uglykid View Post
i have a little problem about subīs for my mobile disco. i have a little/medium mobile disco and my problem is that then i am out and play to a party, have i many times notice that i have more/lots of bass behind the speakers than on the dance floor, i have tried many types of subīs (DIY) bassreflexs-bandpass-look and like x1īs but all with more or less same results, but i have never tried a horn construction, so my question is (i now itīs difficult to say exactly) but will a couple sub horn perhaps help me to get more bass on the dancefloor??
This an old problem. Part of it is that normal subs are non-directional, part is that the DJ/PA is typically near walls, where there is additional room gain for bass. while the middle of the dance floor is always a "bass hole".

To make low bass directional you need either massive horns (and I mean massive, look up the Levan Bass Horn) or subs that use active steering.

Levans and their ilk are severely unportable, active pattern steered subs need multiple amp's and are uncheap.

In the 80's I found that the classic JBL dual 15" "scoop" worked okay for punchy bass across the dance floor (preferably one in each corner), but they do not really go low and they are still rather large, large enough you really want them only for installed sound.

Some may laugh, but the old Karlson coupler does seem to have a few dB gain in the mid-bass over normal reflex boxes and it's weired distortion behaviour makes them sound "lower" than they really go. One can get pretty punchy PA bass out of them, they do like fairly light cones (EVM15L for example) and no floor shaking, but at least they are semi-portable.

These days I personally would probably go for a bunch of modest sized vented cubes with 18" drivers for the bass, 3 pcs per side and just run the middle one inverted (pointing backwards, wired out of phase).

This makes a poor man's steered bass array, needs massively capable drivers and amp's as you need to EQ the heck out of it, but 18" drivers with decent excursion and > 1KW power handling are no longer the creatures of myth they where in the 80's and not even forbiddingly expensive and amplifier watts are cheap.

Ciao T
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