First Outing, Full Band, Titan 48s and omnitop 12s

[brodave2]

this was the long awaited first outing with the new BF rig. Two omnitop 12's on each side, 2512 in each, bottom one on each side has melded array, top one on each side has crossfiring array. Each pair is held together with a ratchet tie down. It surprised me, a 10' strap isn't any extra, takes most of it to go around a pair. QSC PLX 1602 on omnitops, two on each side of amp in parallel, input is stereo. Subs are two titan 48s, 24.5", 3015 loaded. Sub power is a QSC PLX 2402, one sub on each side. Tops had available 500 watts @4ohm stereo, so each cab had available 250 watts. Subs had available 450 watts each. Processing was DBX DR260, crossed over at 100hz, hi passed at 39hz. Mild rock band (Youth Praise Band) in 800 seat church. Mix position was 50' back. I am extremely impressed with the omnitops. I had done one previous similar concert with one omnitop on each side, and found them impressive but not quite up to it. They couple very nicely. Two on each side is huge. Some eq required, but after running manual RTA, they sounded incredible, really nice dispersion, needed no eq on lead vocals, wireless Beta87a. The jury is still out on the subs. I was not blown away by the kick, but different drums and drummers vary greatly. I was bumping the red occasionally on the amp driving the subs, which should not be a problem, 10 ohm rating for the amp should put it at 360 watts per sub. I'm not sure they couldn't have take a bit more. Anyway, I'm used to putting a double 18 or two on each side and sitting in the middle, which is an exaggerated place to be with subs on each side. This gig I had the titans on the floor in the middle of the room, right in front of the stage, with the mouths together. No room for V coupling, and the corners of the room were too far away for corner loading. All in all I think the titans performed well, but they didn't knock my socks off. Playing CD's they sounded incredible, but, as usual, when a band kicks off, it's a different animal. The kick was pretting cool when they were playing on and even keel, but when the rocked out, the kick got lost. I have had this same experience with my double 18's. It was nice to haul in 90 pound subs vs, my 160 pound double 18's. I put the omnitops together on the floor, then stuck the speaker stand into them, then grabbed the omnitops and heaved and tilted them up to an upright position, able to do it alone. That was a big reason for going to them, getting into something I can set up alone. The band was pleased and the promotor was pleased, I got paid, and made it home safe, so, all in all, a good night.

[Bill Fitzmaurice]

One problem that can crop up with centered subs is phase cancellations from the rear side walls. It seems counter-intuitive but often you'll get a better result stacking the subs further away, not only to take advantage of corner or wall loading but to eliminate those destrutive room modes. As for knowing how much the subs will take, there's no substitute for a limiter pre-adjusted to allow a set maximum output voltage from the amps.

[gdougherty]

Glad you liked the OT12's. Now that I've got tweeter issues sorted out I'm loving mine more and more. Bill designed a sweet little cabinet there that can really rock the house. I'm not sure if I want to go to the effort of DR280's or just build another 4 OT12's and figure out some way to lift them up, probably something like Tim and Dave have rigged up. I think for most of what I do 8 OT12's would be plenty of output. The few times I've stacked all 4 in an array, the output was incredible.

I'd highly recommend running the T48's in parallel with the amp bridged. The extra power for peaks helps tremendously, especially live. Since I'm running aux fed, the subs tend to get just bass and kick plus a touch of keys. The transient nature of the signals tends to play well into juicing the subs with as much as they can take but still not overheat the driver. Power compression kicks in as the driver heats up but has less effect on transient peaks like a kick drum on a cool driver. Thus it's a bad idea with recorded music to push them like that, but mine have been just fine running hard live with a 40Hz cut on the bottom. OTOH, 800 seats for a pair of 24" T48's may be asking a bit much. The recommendation on their page says use 4 for 250-800. I'm curious how much the extra 12" of mouth area affects the output, since my 30" T48's have always run very easy and seem to have plenty of headroom left compared to my 4 OT12's.

[brodave2]

I was thinking the same thing about the transient nature of kick needing that extra wattage, but not soaking the coils as would synth bass. I have PLX 3402's that I can use. The 3402 should make 562 watts per side, stereo mode at 10 ohms. That's not much over the 450 watt rms rating of the driver. If I added another pair of T48's I'd be right back where I was, hauling in and out too much gear. I'm looking at 105db max. I was hitting 102 at mix position last night with no problem. I may get really brave one day and try the subs in a corner. Having the subs 50' away from center stage just doesn't seem right.

[Bill Fitzmaurice]

Having the subs 50' away from center stage just doesn't seem right.

At 50 Hz that's only about two wavelengths. I'd try it next sound check.

[Sydney]

try the subs in a corner.

Do it now! + 12db gain
As Bill said, the center of any room stinks ( dead center - couldn't resist ).
Equidistant from all walls guarantees you are in at least 1 node. perhaps 3.
I look at a space as divided by uneven fractions ( ex 3rds 5ths 7ths ), Likewise avoid the 1/4 & even divisor spacing.
A lot of other things come into play ( like wall spacing and materials ) but in general I seek the odd planes.
Symmetrical placement can cause problems

[brodave2]

I like the idea of having the subs out of the way, but that just seems weird. I'll give it a try though. The one gig I did (back with the old double 18's) with subs on one side, over to the side, it was incredible. They weren't in a corner, but they were over to one side. I could have done that last night, easily. AND! that would make for some shorty sub cables, but the subs on the side where the amps are.

[Bill Fitzmaurice]

I like the idea of having the subs out of the way, but that just seems weird. I'll give it a try though. The one gig I did (back with the old double 18's) with subs on one side, over to the side, it was incredible. They weren't in a corner, but they were over to one side. I could have done that last night, easily. AND! that would make for some shorty sub cables, but the subs on the side where the amps are.

Close to the side wall still is probably better than centered unless the room is gigantic.

[DaveK]

Subs in the corner might work out for you. We used a pair of T36 in a corner for a Christmas party. It was a smaller room (200-300), but the thing I noticed walking around was that the deep bass seemed to be everywhere. It was the same volume no matter what part of the room I was in.

[brodave2]

Ok, so here's the rub. Why do all these folks spend so much time and money on programs like smaart to time align all the components of their sound system. It would be impossible to time align a system with the mains on either side of the stage and the subs over in the corner. I'm not contradicting the practice, I'd just like someone smaarter than me to explain how all that shakes out. Folks on the far side of the room are hearing everything above 100hz right now and then half a second later everything below. I know how much delay there is in a large room, I've played bass on a wireless and walked back to the sound guy, playing the whole while. You can do it if you don't stop playing, but once you stop playing, you can't pick it back up because of the delay.

[Bill Fitzmaurice]

Ok, so here's the rub. Why do all these folks spend so much time and money on programs like smaart to time align all the components of their sound system.

They aren't, or at any rate they shouldn't. Time align is a major concern above 200 Hz, almost no concern below 100 Hz.

Folks on the far side of the room are hearing everything above 100hz right now and then half a second later everything below

Only if that far side is 500 feet away.

[gdougherty]

I was thinking the same thing about the transient nature of kick needing that extra wattage, but not soaking the coils as would synth bass. I have PLX 3402's that I can use. The 3402 should make 562 watts per side, stereo mode at 10 ohms. That's not much over the 450 watt rms rating of the driver.

Don't bother, just run them parallel on what you've got. That should put them down about 5ohms and the amp will have plenty of output. 58V at 5ohms is only 670W and the 2402 will put 2400W into 4, albeit with 1% THD.

[brodave2]

there's another thread on here where a guy ran a tuba 36 with a 3015 on a PLX1402 in bridged mono and toasted his driver. That would be about the same as having two on a plx2402 in bridged mode. The PLX 2402 does 2400 watts at 4 ohms bridged, so that should shake out to about 1950 at 5 ohms, or 975 watts per driver. I think that would be overpowered, especially considering the neo magnets don't like heat.

[Bill Fitzmaurice]

there's another thread on here where a guy ran a tuba 36 with a 3015 on a PLX1402 in bridged mono and toasted his driver. That would be about the same as having two on a plx2402 in bridged mode. The PLX 2402 does 2400 watts at 4 ohms bridged, so that should shake out to about 1950 at 5 ohms, or 975 watts per driver. I think that would be overpowered, especially considering the neo magnets don't like heat.

Stop thinking in watts, start thinking in volts. You can't easily limit an amp to a specific power output because you can't easily measure power output. You can easily measure voltage output, which in the case of the 3015LF should be limited to a maximum of 60 volts.

[mloretitsch]

Hey brodave...nice to read your review. I can tell you a few bits and pieces to chew on. I run my t48's (same as yours) stereo on a powerlight 1804. It's only rated for 330w per side at 8 ohms. If I really need to bring out a heavy kick I will bridge this amp into the subs...so now we're talking 1800w at 4 ohms mono. I try to keep it just blinking the -10 light on kick hits in that mode with the limiters.

I'd take 4 of those cabinets to cover that size crowd. I did about 300-350 with my pair of t48's bridged to get a few more db's out of them (shortening their life of course). It was good for that amount of folks...we had some rap music blaring too and it was actually pretty loud on the bottom end.

Thanks for the review though...I want to have 8 otop12's for next season and 4xt48. This makes me even more ready to build when it's not 4 degrees F.

-Matt

edit: a last minute idea...if you are grouping the subs you could take 3 subs...why not? two on one channel of your plx2402 and 1 on the other.