Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

[Gene Hardage]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

It really might come down to building some more, I'm not sure yet. Since I've already committed my remaining 4 to a customer, I will need something else in the meantime.

@Gene... I added those subs to my sheet. I could get two of those subs in the front of the trailer (if I go the 30" wide way) and have a few inches to spare. The nice thing is that I could stack them and have four units in only 24.5" of trailer space. Only issue I have with those is that they will absolutely need cloth-backed grilles to be presentable for my shows.

Some people have voiced concerns over the jet engine look and he said that black foam could be added to hide the innards. As big subs go - they are not that big or heavy and they really do some serious damage.

 

[Chris Davis]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

I'm trying to understand what the real issue is:

A) You need something smaller than a LAB.
B) You need something easier to move than a LAB.
C) you need something "new" to try out.

-drew

It's A and B.

My goal is convergence of my SOS and Racks and Stacks to a common subwoofer like the VRX and VP series sub.

Marlow hit the nail on the head here. There is nothing really wrong with the LABs

----

Another issue with LABs is that using a single isn't really possible, so I'm stuck with too much sub at even the smallest shows. I'm sure a couple powered 18s would be nice to fill in this gap.

Bingo.

Also, I would really, really like to stay away from using anything other than my IT-HD amps. The integration of System Architect in my rig is pretty much critical, and I'm not willing to run different programs to control the rig depending on what passband I'm trying to work on.

I think your thinking on this will hold you back from your above brilliant idea.

Considering you're comparing to a subwoofer for which there are no published specifications, and for which available specifications are probably not accurate, using subwoofers for which you only have the manufacturer's (also possibly wildly inaccurate) max SPL spec, I think you're just masturbating out loud.

Sounds like you should just keep your LABS.

It really might come down to building some more, I'm not sure yet. Since I've already committed my remaining 4 to a customer, I will need something else in the meantime.

Yeah, build new LABS. You know you want to....

In the meantime, devise a good "plan B" for your system controller so that you can effectively use most of the same system for smaller gigs.

P.S. I am not sure what that means with IT-HD amps, but this seems to me what is really holding you back. Real or perceived lack of flexibility here may indeed be a problem.

 

[Silas Pradetto]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

In the meantime, devise a good "plan B" for your system controller so that you can effectively use most of the same system for smaller gigs.

Thanks for the summary, Chris. I'm not sure what your last line means?

 

[Chris Davis]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

Thanks for the summary, Chris. I'm not sure what your last line means?

I was just trying to say that I think a second system controller configuration seems inevitable. I also edited it to see if there is a problem in having more than one configuration with the IT-HD amps. Is is any more difficult to change programs than just rotating a knob like on a usual system controller?

 

[Phil Graham]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

Initially I was under the impression that there would be no front-loaded subwoofer that could equate to a LAB in a reasonable quantity. The SRX718S appear to require 10 units to be equal, which is just on the verge of being unreasonable, IMO. However, looking at the volume (I should have another column for size compared to 4 LABs, hmmm), 10 SRX718S is still less volume than 4 LAB subs. So it's not nearly as bad as it would seem, except that the power requirement would be a lot higher than just four LABs.

I think the sheet could make a quantitative comparison a bit easier. Who knows? If it's based on false numbers then it will only add to the confusion.

PS - I'm not using the manufacturer-provided 'peak' spec. I'm calculating it in the sheet off my own power and sensitivity numbers.

Silas,

Both a 1w "sensitivity" and a "power rating" have so little meaning from virtually any manufacturer as to be essentially useless beyond the math review of setting up the spreadsheet.

Let's make a more rational view of this calculus:

1. Forget "power" entirely
2. Forget about spec sheet "sensitivity"
3. You own a certain number of voltage sources (i.e. amp channels and/or bridged amps)
4. Each of those voltage sources can produce a specific +/- V_peak
5. If not unduly loaded, each of those voltage sources will not enter current limiting in normal use
6. You want to purchase/build designs that are "stout" enough to take the full peak to peak voltage swing of your sources

At this point, then, Hoffman's "iron law" will dictate the sensitivity of your cabinets. Namely, the sensitivity is proportional to the volume of the cabinet and inversely proportional to the cube of the cutoff frequency delta. You pay incredibly dearly for additional extension from a sensitivity perspective. The other way to think of this circumstance is that you decide on the box sensitivity by choosing the cutoff point.

Vented boxes aren't magic. If you know the driver in a particular box, and the tuning frequency, you can reliably calculate the driver output and excursion as well as the velocity of air in the port(s). In fact, other than a few tweaky points I won't dig into presently, WinISD Pro 0.57a does a good job of this for exactly $0.00. Everyone in audio owes the linearteam guys a beer, as their predictions closely match much more expensive programs, and reality.

WinISD asks for the "Power" input to the driver, but in reality that "Power" is equal to the RMS voltage input to produce the desired power at an impedance equal to R_dc of the driver voice coil.

So, for a "Power" input of 2000W into a driver with a 6ohm voice coil R_dc the RMS voltage is as follows:

V_rms = sqrt(P_in*R_dc) or V_rms = sqrt(2000*6) = 109.5V_rms

To calculate V_peak, multiply the V_rms by 1.414:

V_peak = 1.414(109.5) = 154.9V_peak or 2(154.9) = 310V_peak_to_peak

Thus, WinISD can easily be used to calculate the peak voltage input at which a driver exceeds Xmax (or Xlim). The transition from Xmax to Xlim is not a dramatic one, but rather a gradual one marked by the progressive, continual decrease in the driver's Bl product, amongst other things. The character of the driver in this transitional region will define much of how we think of that driver when "driven hard."

In similar fashion, once the Reynold's number in the port(s) goes dramatically north of 100,000 the port compression effects on the vented box response start getting very severe. Practically, for boxes with nearly square ports (not "slot" porting), this Reynold's number is hit with a port airspeed of a little under 10 meters/second.

Since WinISD naively calculates port airspeed by dividing the volume velocity of the air in the port by the port area, it cannot predict the effects of a slot port. But if the box port is square, or divided into square(ish) sections, the airspeed it predicts will be useful, and can help you determine if the box has enough port area. A rule of thumb is that the port area should be a minimum of 50% of the driver Sd.

So, start on your amp's spec sheet, at the amp terminals, and work backwards. You will find that the choices are no longer so broad.

 

[Evan Kirkendall]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

Silas,
Why don't you get 4 SRX718's for your "smaller" shows, and then build 4 new labs for your "bigger" shows? Then combine and use all 8 subs for your "really big" shows? The 718's are decent little subs that'll work for a few hundred people(where you don't want to bring labs in), and you know what the labs are capable of for larger shows. It makes the most sense to me, and won't break the bank...



Evan

 

[Silas Pradetto]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

Silas,
Why don't you get 4 SRX718's for your "smaller" shows, and then build 4 new labs for your "bigger" shows? Then combine and use all 8 subs for your "really big" shows? The 718's are decent little subs that'll work for a few hundred people(where you don't want to bring labs in), and you know what the labs are capable of for larger shows. It makes the most sense to me, and won't break the bank...



Evan

@Evan, I used to own four SRX718S that I used on an IT8000, and I don't even know why I sold them. They were definitely good sounding subs, but I think I sold them after I built my first batch of LAB subs.

I may end up just buying four PRX618S-XLF for small stuff, and then I can use them as drum or sidefill at larger shows. I might build another set of LABs, or another design I have, which I may post here with the designer's permission.

@Chris, my IT-HDs are nothing like a traditional system controller at all. They can have up to 50 presets which can be changed on the fly, applied to other amps, or loaded from files. Amps can be grouped easily for control and monitoring, especially useful when I'm using multiple amps as main L-R or different elements in an array. These conveniences are something that I'm not giving up anytime soon to go back to a traditional system controller. The fact that any amp can power anything at any time is just amazingly useful. The only exception to my IT-HD rule is my Driverack 4820, which also integrates into System Architect, accepts AES digital, and can be used to drive any powered speakers that I might buy. (I used the DR to electronically steer the array of 12 PRX618S-XLFs that I deployed a while ago).

In fact, System Architect is so powerful, I can't even come close to describing its capabilities in one paragraph. Download it (it's free), put some stuff in the venue, and mess around with it. You will be completely blown away.

@Phil, I think I understand what you're saying. Given a driver and box parameters, the sensitivity is pretty much fixed, and the peak output is going to be limited by whatever amplifier I'm driving them with, rather than the rating on the sheet. Since all I have right now is IT5000HDs, that could be the limiting factor for most of the subs on the list. An upgrade to IT12000HDs would be necessary to realize the full potential of some of the subs, which should be factored into the cost (and power consumption) equation.

So, I guess I got my math review, and can calculate the volume of subs pretty accurately...the rest probably isn't that useful...I hope I'm not totally missing the point (I feel like I might be).

Thanks everyone for their opinions so far!

 

[Phil Graham]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

@Phil, I think I understand what you're saying. Given a driver and box parameters, the sensitivity is pretty much fixed, and the peak output is going to be limited by whatever amplifier I'm driving them with, rather than the rating on the sheet.

Yes, exactly. Also, these numbers are not mysterious, but can be calculated, independent of the datasheet, for any driver/box combination you have the specifications for. You are not beholden to the marketing department's interpretation of what the output will be.

So, I guess I got my math review, and can calculate the volume of subs pretty accurately...the rest probably isn't that useful...I hope I'm not totally missing the point (I feel like I might be).

You know what you've got to work with, so you can use those parameters to pick driver/box combinations that provide maximum value for the money. No need to overspend on drivers if your amps aren't up to the task, and no need to buy the top shelf amplifiers if you can't afford the drivers that can manage that input level. From the itech 5000HD datasheet, it would appear that the amplifier has 100V_rms rails. That will be a good match for many middle of the road 18" drivers.

The thing you might have missed is that many subwoofers have ports that are too small, and therefore those with undersized ports can be eliminated from consideration.

 

[Ron Kimball]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

PPS - I just had another idea. I recently used twelve PRX618S-XLF subs for a few thousand people outside...it was plenty of sub for my taste. According to some quick math, 8 of them would do about the same as 4 LAB subs? Not sure I believe that.

Me neither - my Rog subs are about equal to two PRX618S-XLF each in their passband. I'd guess a Lab = about 2 Rog's so about 4 XLF's? Also those XLF's will take 4x or so the mains power as the Labs/iTech combo for the same SPL I think?

 

[Ron Kimball]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

BTW I've "chatted" a bit with a TH-118 owner on another forum and I think you may be underestimating their output - they are much flatter than Labs and with a bridged iTech5000HD for each I'd be worried that four with 16KW (or 20KW if available in 8 ohms?) into them would punch a hole in the space-time continuum no prob :lol:. He was using some EV 4KW amps bridged into his.

 

[Chris Davis]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

Silas,
Why don't you get 4 SRX718's for your "smaller" shows, and then build 4 new labs for your "bigger" shows? Then combine and use all 8 subs for your "really big" shows? The 718's are decent little subs that'll work for a few hundred people(where you don't want to bring labs in), and you know what the labs are capable of for larger shows. It makes the most sense to me, and won't break the bank...



Evan

What Evan said.

I think all that matters is that you have some large format horn loaded subs, and also smaller 18" front-loaded cabs to supplement. Fewer limitations than with a one size fits all box, that is unless you are thinking about scaling down some.

 

[Ivan Beaver]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

I've put together a Google spreadsheet to help me make the decision.

It calculates how many subs it would take to reach 154dB (approx 4 LABs) based on the 1 watt sensitivity (I corrected it if it were based on 2.83 volts) and the nominal power each can handle.

I would put pricing on the sheet, but that is something I can't publish.

And, if you have another subwoofer you'd like me to put on the sheet, send me the info or link and I'll put it on there. That link will update automatically when I add more to it.

Just for fun, you should compare the rated sensitivity and the actual sensitivity at 330 or 35Hz-for those products you can get the real data on. Not just printed numbers or -3 or -10, but an actual graph (the numbers don't always line up well).

WHat a sub does at 35Hz is often very different than at say 60Hz.

If you need to go low, then that is a BIG-HUGE issue. If 40 or 50Hz is fine, then going lower is not that big a deal.

It just depends on what you need.

 

[Ivan Beaver]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

BTW I've "chatted" a bit with a TH-118 owner on another forum and I think you may be underestimating their output - they are much flatter than Labs and with a bridged iTech5000HD for each I'd be worried that four with 16KW (or 20KW if available in 8 ohms?) into them would punch a hole in the space-time continuum no prob :lol:. He was using some EV 4KW amps bridged into his.

Langston has a number of TH118's (at least 8- many more-I'm not sure). His main rig is EAW 730's, I think he is running 12/side.

He has recently switched over the Lab Gruppen 14K for the subs. I am not sure if he is running 1 or 2 cabinets per side-but something tells me he only 1 cabinet per side. He likes headroom.

 

[Ron Kimball]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

I must be the only guy on this forum that has seen - heard and used these - http://www.ramsdellproaudio.com/products/subs/BP-SD21.htm
Check the dimensions - maybe you could pack a different way?

The 18" version is 22.5" and quite a bit lighter .

 

[Ron Kimball]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

Langston has a number of TH118's (at least 8- many more-I'm not sure). [...] He has recently switched over the Lab Gruppen 14K for the subs. I am not sure if he is running 1 or 2 cabinets per side-but something tells me he only 1 cabinet per side. He likes headroom.

The i-T120000 HD looks to be a good choice also if one wants to stay with Crown power? BTW is the TH-118 available in 8 ohm or only 4 ohm? An 8 ohm version would seem to be a better match to a bridged i-T5000 HD

 

[Jay Barracato]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

http://www.youtube.com/watch?v=LH5Y7EaZx9M


Om I give up, can we actually embed a video here?

 

[Silas Pradetto]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

The i-T120000 HD looks to be a good choice also if one wants to stay with Crown power? BTW is the TH-118 available in 8 ohm or only 4 ohm? An 8 ohm version would seem to be a better match to a bridged i-T5000 HD

Only 4 ohm. As Langston has said in his amp review thread, the IT series doesn't mind 2 ohm stereo or 4 ohm bridged operation at all, they just current limit sooner than with lighter loads. The peak power is still there and will still be worth having available.

The TH118 can take so much power I'd always want the biggest amp I could afford on them. I'd definitely be buying a 12000HD if I were to buy some of them.

 

[Ron Kimball]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

The TH118 can take so much power I'd always want the biggest amp I could afford on them. I'd definitely be buying a 12000HD if I were to buy some of them.

Two in stereo per or one bridged?

 

[Silas Pradetto]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

Two in stereo per or one bridged?

I'd run them two in stereo, but I think Langston also reported that a TH118 can withstand a bridged PL380, so I don't doubt that a bridged IT12000 would work, even if 12kW into one woofer is totally ridiculous.

 

[Ron Kimball]

Re: Yes, it's cliche, yes it's overdiscussed, but yes, I need new subs.

I'd run them two in stereo, but I think Langston also reported that a TH118 can withstand a bridged PL380, so I don't doubt that a bridged IT12000 would work, even if 12kW into one woofer is totally ridiculous.

Hey, anything worth doing is worth overdoing . But yah, 6KW each should do it .