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Charles Jenkinson wrote: ↑Wed Feb 05, 2020 8:02 am We bought a 13 year old Land Rover Discovery 3 in September. There were some practical reasons for getting it, not least 6 proper sized seats, but it’s not used to its max in any way – when I tried driving up a green lane, number 2 son complained of the bouncing around and Mrs J said, “can you turn around please”. It’s hard not to feel a little smug when driving it though, even for an old, cheap one like it is. We had a party on Saturday, and I was surprised that I could fit a 19” T30 through the rear passenger door without any problem. I don’t especially like the £80 fuel fill ups every fortnight and watching the fuel gauge dropping, but at 25mpg, it’s not bad for what it is.

Did I say, it's £570 road tax. Ouch.

Wow! That's better MPG than my Tacoma. It has a 3.5l V6 and it gets around 21 MPG highway. Although, it only costs me around $45 to fill it up. And I live on base so I only drive around 3 mi to work.

Imperial gallons?

Aye, 4.55litres per gallon. A 2.7 V6 turbo diesel, auto - mostly around town mileage. The Discovery of that age has legendary quality, but they still seem to have an emotional pull - it was Mrs J that wanted me to get one - I'd have preferred a double cab van - 6 seats with a proper load space behind. When we'd finished load out on Saturday, my mate said he was envious of it. ...he hadn't seen the previous owner service bills that bulked out the car sales guy's folder.

'Legendary' is an interesting way of putting it.

A friend of mine had a Jag E back in '72. It was gorgeous, one of the limited production aluminum frame racing jobs. But I didn't envy him. Despite being a mechanic it was all he could do to keep it running.

I was reading elsewhere that if I couldn't spread my T39s at least 56 ft apart then clustering them together would be best. How exactly does that work? The length of the wave at 50 Hz is 22.3 ft so wouldn't that put them around 2 1/4 wavelength's apart?

Am I totally missing the point on this? I thought they needed to be either less than 1/4 or more than a whole wavelength apart.

Bryan Cox wrote: ↑Wed Feb 05, 2020 6:28 pm I was reading elsewhere that if I couldn't spread my T39s at least 56 ft apart then clustering them together would be best. How exactly does that work? The length of the wave at 50 Hz is 22.3 ft so wouldn't that put them around 2 1/4 wavelength's apart?

Am I totally missing the point on this? I thought they needed to be either less than 1/4 or more than a whole wavelength apart.

What you're missing is the 56 feet is for 40Hz, not 50.
Yep, the separation needs to be 2 wavelengths or greater, 40Hz is 28 feet, so it adds up.

If you were a T60 owner, at 25Hz you would need 90 feet (2 x 45')!

Now then, real world use says a single cluster may cause power alley(s) and that might not be so good.
So you will see people separating, but not to 2 wavelengths, as there just isn't room to do that, in order to eliminate power alley(s).
If you do this, and you start to see a fall off in response at a certain lower frequency (or frequencies), then you need to keep it in your mind that that is a result and function of insufficient separation of the cabs, and can't be cured with EQ.

Lots of people simply don't know this stuff, or let aesthetics dictate setup regardless of the laws of physics.
It's great to know this stuff, and you can try to use the info you've learned whenever possible, but there's always that curve ball gig.
Best to learn it all, play around with it, learn what works, what doesn't, and working out the theoretical outcomes if it doesn't work...

Grant Bunter wrote: ↑Wed Feb 05, 2020 6:48 pm

Bryan Cox wrote: ↑Wed Feb 05, 2020 6:28 pm I was reading elsewhere that if I couldn't spread my T39s at least 56 ft apart then clustering them together would be best. How exactly does that work? The length of the wave at 50 Hz is 22.3 ft so wouldn't that put them around 2 1/4 wavelength's apart?

Am I totally missing the point on this? I thought they needed to be either less than 1/4 or more than a whole wavelength apart.

What you're missing is the 56 feet is for 40Hz, not 50.
Yep, the separation needs to be 2 wavelengths or greater, 40Hz is 28 feet, so it adds up.

If you were a T60 owner, at 25Hz you would need 90 feet (2 x 45')!

Now then, real world use says a single cluster may cause power alley(s) and that might not be so good.
So you will see people separating, but not to 2 wavelengths, as there just isn't room to do that, in order to eliminate power alley(s).
If you do this, and you start to see a fall off in response at a certain lower frequency (or frequencies), then you need to keep it in your mind that that is a result and function of insufficient separation of the cabs, and can't be cured with EQ.

Lots of people simply don't know this stuff, or let aesthetics dictate setup regardless of the laws of physics.
It's great to know this stuff, and you can try to use the info you've learned whenever possible, but there's always that curve ball gig.
Best to learn it all, play around with it, learn what works, what doesn't, and working out the theoretical outcomes if it doesn't work...

Phenomenal explanation! Thanks, Grant. On Saturday I did not have my T39s 44 ft apart (or even close for than matter). I'll be sure to do that when I do this again.

Bryan Cox wrote: ↑Wed Feb 05, 2020 6:28 pm I was reading elsewhere that if I couldn't spread my T39s at least 56 ft apart then clustering them together would be best. How exactly does that work? The length of the wave at 50 Hz is 22.3 ft so wouldn't that put them around 2 1/4 wavelength's apart?

Am I totally missing the point on this? I thought they needed to be either less than 1/4 or more than a whole wavelength apart.

They "need" to be either closer than a 1/4 wavelength of the highest frequency in the bandwidth, or greater than 2 wavelengths of the lowest frequency.

It varies depending on temperature, humidity, & atmospheric pressure... but I use the number 1125 feet per second as the speed of sound for the calculation. Just divide that by the frequency (which is pressure waves per second) to get a wavelength. Then simply multiply by 2 to get two wavelengths, in feet. Or divide by 4 to get a quarter wavelength.

So, in your case, high passing at 50Hz, 1125 / 50 = 22.5' wavelength, x 2 = 45 feet minimum distance needed between stacks.

I think having them spread in two stacks will produce a power alley effect, which could be good or bad depending on venue and goals. And one stack provides greater output by 3dB due to "mutual coupling", the speakers essentially combine and work as 1 source... Pretty sure it's 3dB. Might want to verify that with the big boss. In any case, if you ran a 100Hz low pass for the subs, 1125 / 100 = 11.25 wavelength / 4 = 2.81' (or 33¾") quarter wavelength or closer to achieve mutual coupling. 27" or less for a 125Hz crossover point.

I'm guessing you're talking about the placement thread. If not, it's essential reading. viewtopic.php?f=10&t=398

One stack, v-plated for greatest output potential. I think spreading them is considered less than optimal. However, as I understand it, indoor venues can throw all that out the window. Something about a sub crawl... I look forward to experimenting with this myself as the need presents itself.

I always try to put 'em together when possible. However, outside I'm able to get out to about 42 ft....at that distance, I get a tiny little bad spot right in the middle of the speakers about 30-40 feet back. Not noticeable to the crowd.

There are a few venues for weddings and corporate gigs where there really isn't any option except to split 'em and put tops on 'em.....that's just the reality of what we do. Always try to do it the best way, but it's not a hill to die on if they are paying well.....

SethRocksYou wrote: ↑Wed Feb 05, 2020 7:31 pm One stack, v-plated for greatest output potential. I think spreading them is considered less than optimal. However, as I understand it, indoor venues can throw all that out the window. Something about a sub crawl... I look forward to experimenting with this myself as the need presents itself.

You'll find that with almost all the venues that you set up in are not conducive to spending an hour testing sub positions and EQing the room. You just have to make a decision based on your experience and try to get the room as good as you can. Just doing that will still put you way ahead of most every other system that comes into most venues.

I see people all the time set up their system and never even run a song through it to try and EQ the room....they just start sound checking and making huge EQ moves on each channel.....

OH! Also, I found the thread I was thinking about where Behringer voltages were discussed. viewtopic.php?t=24393

49v loaded, reported by CoronaOperator which I consider a reliable information source. Haven't heard anything from him in a while. Any of you guys keep contact with him? Hope he's alright.

Seth, Bruce;

Thanks for the info, fellas. The next time I test the T39s I'll stack and v plate them. Seth, thanks for the other thread. I read it and it makes a lot of sense.

With those things in mind concerning class D amps, I need to do research and maybe procure some class A/B amps.

At the very least I'll get some more appropriately sized class D amps. But I don't like the idea of them cutting to 50% power when taxed.

Bruce Weldy wrote: ↑Wed Feb 05, 2020 7:38 pm

SethRocksYou wrote: ↑Wed Feb 05, 2020 7:31 pm One stack, v-plated for greatest output potential. I think spreading them is considered less than optimal. However, as I understand it, indoor venues can throw all that out the window. Something about a sub crawl... I look forward to experimenting with this myself as the need presents itself.

You'll find that with almost all the venues that you set up in are not conducive to spending an hour testing sub positions and EQing the room. You just have to make a decision based on your experience and try to get the room as good as you can. Just doing that will still put you way ahead of most every other system that comes into most venues.

I see people all the time set up their system and never even run a song through it to try and EQ the room....they just start sound checking and making huge EQ moves on each channel.....

I've experienced this more times than I'd like to remember. Venues would gripe about soundchecks because their two regulars couldn't hear the TV. But then we'd have a feedback issue in the first set and they'd ask us if we knew what we were doing.

As for sub placement...at the time I had no idea that was a thing. I used either my set of Yamaha 18" direct radiating subs or EV SW 181s. We set up like every other local band with a stack on each side of the stage and one side was almost always next to the wall. And we'd get that notorious 70 Hz bump in the low end. Wish I'd been a member of the forum back in 2010. Haha

Bryan Cox wrote: ↑Wed Feb 05, 2020 8:33 pm As for sub placement...at the time I had no idea that was a thing. I used either my set of Yamaha 18" direct radiating subs or EV SW 181s. We set up like every other local band with a stack on each side of the stage and one side was almost always next to the wall. And we'd get that notorious 70 Hz bump in the low end. Wish I'd been a member of the forum back in 2010. Haha

It took a little searching, but I found it. I remember reading this review a while back. Something about it just stuck with me, about sub placement and it's effects when it's good and bad. Thought it would be worth a re-share... viewtopic.php?f=13&t=8576