2 OT 212, 4 titan 48 photo

[sine143]

^^^ that sounds like a really good idea, especially given the fact that your cabs are built to a code miles ahead of my own motto: If it doesnt fit, sand it with some 40 grit and PL the crap out of it.

[Ron K]

Dave when you used the Titans in place of the reflex 18"s did you have them separated left and right?

If so it's possible the Titans were having more of a problem with a power alley then the 18"s.

The harmonic distortion of the 18"s could probably be felt better even though the power alley still existed trumping the bass guitar sounds!

To clarify I was not saying all the new switching amps just budget ones that are being used where you are at the edge of headroom.The new more expensive units seam to keep up on sub duty as well as the big iron does from what I have heard so far.

With some of the cheaper/budget switching units you need to add headroom to achieve the same performance. I personally haven't tried a PLX on the bleeding edge but I would suspect it has the same problems but perhaps not. I know for a fact the PLs do not and for the price difference I would hope it didn't!

I do know the XTIs have this problem. I'll know very shortly if the Peavey IPR does as well.

[brodave2]

Maybe you should give some big-iron Class AB a shot on those T48's, or try running one per amp, like you did the 18"s. IIRC, RonK was saying he's not so impressed with the newer switching amps on bass material when you push them to their limits. PLX's are light and letting them coast individually might do better than loading up the amp. I'm running two at a time off a channel of my PLX3602 and not having any issues.

If you were up to it, you might try building a sample 30" cab. It took me under 3 sheets of 4x8 ply and about a week to crank one out. You've got the drivers to spare and you could probably get some money on the forums for the unloaded cabs if they did the trick. The 24" still isn't a slouch, just not quite as loud as you're used to. Yours look good and uniform, easily saleable.

The amps are the same in this shootout. The PLX's do just fine with the double 18's, and I'm running a double 18 on each side of the amps. I could run the 3402's in bridged mode, one amp per one sub, the double 18's can take it. The titans are supposed to reach Xmax at 300 watts. I think I had them there. All things considered, I've built all the titans I'm going to. It's a good design, but doesn't fit me. Considering the best I can get out of the titans is 1:1 with my double 18's AT THE SAME WATTAGE, and the double 18's can take about 10x the wattage, it just isn't going to work. I'd sell the titans for what I have in them.

[Turntablist]

How big are your 2*18" subs and how low are they tuned?

[brodave2]

How big are your 2*18" subs and how low are they tuned?

they're 17 cu. feet and tuned to 50hz

[brodave2]

Dave when you used the Titans in place of the reflex 18"s did you have them separated left and right?

If so it's possible the Titans were having more of a problem with a power alley then the 18"s.

The harmonic distortion of the 18"s could probably be felt better even though the power alley still existed trumping the bass guitar sounds!

To clarify I was not saying all the new switching amps just budget ones that are being used where you are at the edge of headroom.The new more expensive units seam to keep up on sub duty as well as the big iron does from what I have heard so far.

With some of the cheaper/budget switching units you need to add headroom to achieve the same performance. I personally haven't tried a PLX on the bleeding edge but I would suspect it has the same problems but perhaps not. I know for a fact the PLs do not and for the price difference I would hope it didn't!

I do know the XTIs have this problem. I'll know very shortly if the Peavey IPR does as well.

yes, they were separated right and left. Sometimes that's how it has to be. That is the way I set up the double 18's in this venue and they do fine, it's a corner stage. We can hash sub placement all day long, but this was an A-B test. As far as the PLX's, it seems they come to life when the clip light starts blinking, although I rarely run them that way. I believe in bringing enough rig to the gig so I don't have to. When I bought the PLX's several years ago, they replaced Crown MA3600's, so I have quality "iron" to compare them to.

[Turntablist]

How big are your 2*18" subs and how low are they tuned?

they're 17 cu. feet and tuned to 50hz

Well, then that's why they are so loud. They're bigger than the T48s and as they are tuned higher they have higher sensitivity within their passband and you won't max out the excursion as soon as if they would have been tuned lower. That the T48s are smaller, tuned half an octave lower and still is on par sensitivity wise is quite impressive.
A more fair comparison to your double 18"ers would have been T39s.

The T39 is 18% smaller than the T48 but it still beats it sensitivity wise. The T39 would have been your animal.
IMO, the optimum would be to sell the T48s and build a fleet of T39s. Two V-plated 24" wide T48s would roughly be on par with two free standing 30" wide T39s even though the T39 stack would be a LOT smaller.

[Ron K]

I'm not questioning your reasoning for splitting your subs at all.Simply making a point that they may react differently to the power alley effect. I'm well aware that its not always possible to boundary load or use physics correct placement on every gig.

As far as the old-iron vs new switching PLX like I said I could be wrong with that particular amp.I don't have any nor do any of my constituents so I can only assume.It's good if it doesn't suffer from recovery problems.

Can you say the same when the voltage on the main feed drops to say 87-97 volts at near 100% humidity? Again not having one to play with I can only guess. The switchers that I have played with have problems when supply voltage begins to drop.I-techs and PLs seam to handle this well but the Macros and the likes of Crests 9001 etc. IMHO dont even blink!

[gdougherty]

How big are your 2*18" subs and how low are they tuned?

they're 17 cu. feet and tuned to 50hz

Well, then that's why they are so loud. They're bigger than the T48s and as they are tuned higher they have higher sensitivity within their passband and you won't max out the excursion as soon as if they would have been tuned lower. That the T48s are smaller, tuned half an octave lower and still is on par sensitivity wise is quite impressive.
A more fair comparison to your double 18"ers would have been T39s.

The T39 is 18% smaller than the T48 but it still beats it sensitivity wise. The T39 would have been your animal.
IMO, the optimum would be to sell the T48s and build a fleet of T39s. Two V-plated 24" wide T48s would roughly be on par with two free standing 30" wide T39s even though the T39 stack would be a LOT smaller.

That's arguable. The 24" T48 still beats the T39 from 60Hz+ by about 2db is my guess. The wider T48 like I'm running will beat it all the way down to 40Hz. The 3015LF will also move more air than a single 3012LF will ever think of moving, so the final output of the T48 will be higher as well. That's if I understand everything correctly, which I think I do.

[SeisTres]

That's arguable. The 24" T48 still beats the T39 from 60Hz+ by about 2db is my guess. The wider T48 like I'm running will beat it all the way down to 40Hz. The 3015LF will also move more air than a single 3012LF will ever think of moving, so the final output of the T48 will be higher as well. That's if I understand everything correctly, which I think I do.

The whole thing about moving more air only matters for the extra extension of the driver had limited xmax. But if sensitivity is the same for both, and they both take the same wattage, it doesn't matter if it's a 10" or a 15". So if you crossover at 45hz with a very steep slope and have no need for anythign below it, the extra potential of the 15" in the t48 will be wasted.

Think about it like this, if a 15" and a 6" have the same sensitivity at 1khz, and that's all you wanted to reproduce, what would be the point of the 15" even if it had more xmax and could move more air?

However, it still holds that if you want the most out of your money you should consider the Vd of the driver since most of the time we do need stuff under 45hz.

Disclaimer: please notice i did mention that the sensitivities have to be equal as to no have anyone arguing over the increased area of the cone and added gain due because of it. Also, that's how I understand it, but if I am wrong, please do not hesitate to correct me.

[Turntablist]

The T39 is 18% smaller than the T48 but it still beats it sensitivity wise. The T39 would have been your animal.
IMO, the optimum would be to sell the T48s and build a fleet of T39s. Two V-plated 24" wide T48s would roughly be on par with two free standing 30" wide T39s even though the T39 stack would be a LOT smaller.

That's arguable. The 24" T48 still beats the T39 from 60Hz+ by about 2db is my guess. The wider T48 like I'm running will beat it all the way down to 40Hz. The 3015LF will also move more air than a single 3012LF will ever think of moving, so the final output of the T48 will be higher as well. That's if I understand everything correctly, which I think I do.

Since you have to reproduce a tone at 45hz 7db louder than a tone at 70hz to percept it as as loud any sensitivity advantage in the upper part of the passband is quite moot since nearly all power goes to the low end of the passband anyways. I suspect your 30" wide T48 will be on average 1db louder or so than a 30" wide T39 above 45hz. As seistres pointed out any advantage in Vd is pointless if you don't need any output below 45hz since both the T48 and the T39 are restricted by power above that frequency.
Below 45hz the T48 is king but since brodave2 hasn't commented on any advantage in extension that the T48s has over his double 18" cabs I suspect that he doesn't need a lot of output below 50hz and since that is the case the T48 loses it's point.

[gdougherty]

I'll wait for Bill to step in and smack me down, but my understanding of Vd was that given the same or similar sensitivity, it was the final answer in maximum output. Vd is Sd*Xmax and the increase in xmax also increases the Vd and allows a 3012HO to generate about 3db more output than a 2512 in an OT12 despite essentially the same sensitivity. If Turntablist and SiesTres are correct in their assertions, I'd expect both drivers to produce the same max output. 15" drivers have roughly the same Sd, so xmax alone can often be compared, but Vd is more useful when comparing drivers with different cone sizes. Larger Sd will typically equate to higher sensitivity in a driver's operating range.

Wattage, in terms of output, I always understood to be specific to the driver and largely dependent on xmax as well. A driver with 6mm of xmax and 600W of power handling can simply take more heat than a driver with 9mm of xmax and 450W of power handling. Higher power handling does not always equate to higher xmax as far as I've seen, and I'm not sure that 300W always equals the same excursion on drivers with similar sensitivities.

[Bill Fitzmaurice]

if sensitivity is the same for both, and they both take the same wattage, it doesn't matter if it's a 10" or a 15". .

That's a big if. How much power a driver can use is almost always determined by Vd, not Pe. The recommended maximum voltage for the 3012LF and 3015LF is not the same, for this reason.

[brodave2]

Below 45hz the T48 is king but since brodave2 hasn't commented on any advantage in extension that the T48s has over his double 18" cabs I suspect that he doesn't need a lot of output below 50hz and since that is the case the T48 loses it's point.

the double 18's trounce the T48's especially in the lower frequencies. In my side by side tests the double 18's went 4db louder at 60hz.

http://i926.photobucket.com/albums/ad10 ... rsless.jpg

[Bill Fitzmaurice]

the double 18's trounce the T48's especially in the lower frequencies. In my side by side tests the double 18's went 4db louder at 60hz.

With equal power after accounting for the impedance differential?