T48 Anecdote

[gdougherty]

Some background: My T48's are 30" wide 3015LF loaded. I'm a bit thankful that 30" was the widest recommendation at the time I built. The dimensions work out very nicely for me more often than not. I planned on building two and possibly adding more later. My goal then was the best performance and highest sensitivity I could get out of just the two boxes, so I went as wide as recommended. I've had plenty of stages where 30" is right about stage height or just a hair over, and so many where 36" would have been much more intrusive. OTOH, I've center clustered a pair without any stage, right in front of the band, without complaints. Just the expected questions about why I put the sub right there.



Given the sensitivity chart of the 36" T48, I know I would have wanted to go there. I've mentioned elsewhere my guess that the 30" runs somewhere between the two and probably crosses 100db at about 40Hz, the extra 3db at 40Hz looks tempting for only another 6" of plywood. Especially if I hadn't known that 95% of the time, indoors and out, I wouldn't even bother carting along my second pair.

Last night I did an event in a high school theater/auditorium that seats about 500. Tall ceilings, decent acoustics, big stage with a wide area down front for the pair of subs to sit. Performers were a latin band and two other groups using tracks as backup. Both track based groups were hip-hop/RnB style groups, one was like BoyzIIMen made up of latinos. Both great acts with some pounding low end. A 1oct parametric adjustment of -8db at 100Hz has cleaned up the sound of my T48's immensely and I gave it about +2db at 75Hz as well for some extra oomph.

At the back of the auditorium it felt very good to me and was pretty even throughout the room. The evening went well with 3 OT12 ground stacked on each side of the stage covering the room exceptionally well. Had comments from all kinds of people about how great everything sounded and the bands especially loved the bottom end. Some guest musicians that played at a local club the night before, with 6 EAW double 18" loaded subs per side, commented on how the bottom end clarity and impact just blew away the club sound. I mixed them over there and very much agreed.

Anyway, the real anecdote, the bassist from the latin band sat out front, maybe 10-15ft back from the subs. At dinner afterward he asked what they were and expressed the typical amazement that only a pair of 15" drivers were producing that kind of output. He commented that during the tracks he felt like he was going to throw up from the bass. This from a player who stands right in front of his cranked 8x10 stack he carts around with him.

[Chris_Allen]

I never noticed that considerable boost @50Hz in the T48 before.

[Chris_Allen]

What do you think would be best for this setup?

Cross at 125, flat to 50? You mentioned a boost at 75, is it really worth experimenting with that frequency?



I'm going through a patch where everything sounds like mush and it's really hard to diagnose when your playing.

My T39's are actually 15" with a BP102's. I put the DR280 on there to show it's bass response against a T39/DR200 combo. Of course, you can't V-Plate or corner load a DR280.

[paul_ulrix]

how are those measured ?

[Scott Brochu]

At dinner afterward he asked what they were and expressed the typical amazement that only a pair of 15" drivers were producing that kind of output. He commented that during the tracks he felt like he was going to throw up from the bass. This from a player who stands right in front of his cranked 8x10 stack he carts around with him.

What did he have for dinner?

That's awesome! I wish you could mix sound for us.
One question; mixing in a gym how do you get rid of the tunnel sound if you have any?

[gdougherty]

What do you think would be best for this setup?

Cross at 125, flat to 50? You mentioned a boost at 75, is it really worth experimenting with that frequency?



I'm going through a patch where everything sounds like mush and it's really hard to diagnose when your playing.

My T39's are actually 15" with a BP102's. I put the DR280 on there to show it's bass response against a T39/DR200 combo. Of course, you can't V-Plate or corner load a DR280.

120/125 seems to be a poplarly recommended crossover point for the DR200/OT12's. I cross at 100Hz, but I tend to run 2 OT12 where I could easily get away with 1. I also don't boost the 100-120 range on the OT12, which I may need to revisit. IIRC though, it looked flat enough on the RTA with the two combined.

[gdougherty]

At dinner afterward he asked what they were and expressed the typical amazement that only a pair of 15" drivers were producing that kind of output. He commented that during the tracks he felt like he was going to throw up from the bass. This from a player who stands right in front of his cranked 8x10 stack he carts around with him.

What did he have for dinner?

That's awesome! I wish you could mix sound for us.
One question; mixing in a gym how do you get rid of the tunnel sound if you have any?

Lucky for him, dinner was afterward

I'm trying not to get a big head about my ability to mix since a good portion of why things sound so good is the equipment I've been fortunate enough to stumble onto and collect. Had I decided to just build some single or double 18" cabs a few years back with the inexpensive drivers I could afford at the time, instead of stumbling on Bill's designs my story today would be vastly different.

I've not had major problems in gyms, though I start with a good outdoor EQ and just pull out any major room resonances I hear or see on an RTA. The clarity of the OT12's and T48's takes care of the rest. I have had some luck with phase reversals on channels in tightening up room reflections in very small gym/exercise rooms before, but that was all trial and error.

[Bill Fitzmaurice]

I have had some luck with phase reversals on channels in tightening up room reflections in very small gym/exercise rooms before, but that was all trial and error.

That tends to work best where you have more than one mic close to each other, like with drums. Running them out of phase cancels out the background reflections that are common sources to them while not bothering the signals that aren't common, the individual drums.
BTW, look at old pics of the Dead, you'll see two identical mics taped together. They sang into only one, the other was polarity reversed so that whatever both picked up, ie., stage sounds and monitor feed, was canceled out. The result was clean vocals and silly high monitor levels.

[gdougherty]

I have had some luck with phase reversals on channels in tightening up room reflections in very small gym/exercise rooms before, but that was all trial and error.

That tends to work best where you have more than one mic close to each other, like with drums. Running them out of phase cancels out the background reflections that are common sources to them while not bothering the signals that aren't common, the individual drums.
BTW, look at old pics of the Dead, you'll see two identical mics taped together. They sang into only one, the other was polarity reversed so that whatever both picked up, ie., stage sounds and monitor feed, was canceled out. The result was clean vocals and silly high monitor levels.

What a cool idea. Not sure exactly why things worked in my situation, but I'd guess it had to do with the location. It was a gym/exercise room at an ICE detention center, about 50x60x25, cinder block walls, with the band packed into a 10-12ft wide strip next to the wall on the 60ft side of the room. When we first setup I had all kinds of reverberation in the room that made feedback an issue. Reversing polarity on vocal channels and a few others eliminated all the reverberation and tightened up the sound in the room. I've since done the same trick in the middle of a larger high school gym with similar results.

[CT]

quote="gdougherty"]

I have had some luck with phase reversals on channels in tightening up room reflections in very small gym/exercise rooms before, but that was all trial and error.

That tends to work best where you have more than one mic close to each other, like with drums. Running them out of phase cancels out the background reflections that are common sources to them while not bothering the signals that aren't common, the individual drums.
BTW, look at old pics of the Dead, you'll see two identical mics taped together. They sang into only one, the other was polarity reversed so that whatever both picked up, ie., stage sounds and monitor feed, was canceled out. The result was clean vocals and silly high monitor levels.

What a cool idea. Not sure exactly why things worked in my situation, but I'd guess it had to do with the location. It was a gym/exercise room at an ICE detention center, about 50x60x25, cinder block walls, with the band packed into a 10-12ft wide strip next to the wall on the 60ft side of the room. When we first setup I had all kinds of reverberation in the room that made feedback an issue. Reversing polarity on vocal channels and a few others eliminated all the reverberation and tightened up the sound in the room. I've since done the same trick in the middle of a larger high school gym with similar results.[/quote]

How do you reverse polarity on the vocal channels?[

[Bill Fitzmaurice]

How do you reverse polarity on the vocal channels?[

With the channel phase/polarity switches. This of course requires that the board be so equipped.

[Scott Brochu]

How do you reverse polarity on the vocal channels?[

With the channel phase/polarity switches. This of course requires that the board be so equipped.

My little Mackie bard doesn't have it and either does my Behringer's. But What and the heck does the SOLO button suppose to do?
Does that have to do with polarity?

[David Carter]

How do you reverse polarity on the vocal channels?[

With the channel phase/polarity switches. This of course requires that the board be so equipped.

My little Mackie bard doesn't have it and either does my Behringer's. But What and the heck does the SOLO button suppose to do?
Does that have to do with polarity?

Nope. The SOLO button changes your LED level meter to show the level for the SOLO-ed channel(s) instead of for the main mix. This is to allow you to check levels on each channel to make sure that none of them are clipping. There's probably a lot more to it than that, but that my layman's interpretation.

[BrentEvans]

My little Mackie bard doesn't have it and either does my Behringer's. But What and the heck does the SOLO button suppose to do?
Does that have to do with polarity?

Nope. The SOLO button changes your LED level meter to show the level for the SOLO-ed channel(s) instead of for the main mix. This is to allow you to check levels on each channel to make sure that none of them are clipping. There's probably a lot more to it than that, but that my layman's interpretation.

The SOLO button also puts that channel by itself into the headphones so you can adjust it.

As long as there's no phantom power involved, you can also build an adapter to reverse the positive and negative wires (pin 2/3) on the mic cable. Hosa (and I'm sure others) sell this as a premade piece too.

[gdougherty]

As long as there's no phantom power involved, you can also build an adapter to reverse the positive and negative wires (pin 2/3) on the mic cable. Hosa (and I'm sure others) sell this as a premade piece too.

Phantom is typically carried on pin 1/shield. You should be able to reverse pins 2/3 whether or not you need phantom power.

For those asking, the phase/polarity button is typically up by the gain/trim adjustment and is a often represented by the Greek letter Phi, a zero with a diagonal line through it. Not all boards have them, as noted already.