Tim Weaver wrote on Tue, 06 April 2010 10:13 |
+1 B&C or Eminence will also tell you exactly what kind of enclosure to build too. The TBX100 is a hoss. |
Tim Weaver wrote on Tue, 06 April 2010 13:40 |
Building from a plan provided by a manufacturer is actually less work than measuring what you have and then halving the volume. And my recommendation for the B&C is due to output AND sound quality. A properly built dual 18 with 2 TBX100's is a better sub than an SRX728. It may not be louder, but it is more accurate. I'd pick the B&C sub over the 728 any day of the week. Besides, it's no slouch when it comes to output either! |
Adam Schaible wrote on Tue, 06 April 2010 21:01 |
Hi Art, Do you know if that is +/- 23mm, or +/- 11.5mm for the JBL driver? Either way, that's a lot.... but if the box is tuned correctly for what you're trying to do, I don't really see 8mm of xmax as an issue. |
Art Welter wrote on Tue, 06 April 2010 18:57 | ||
Tim, How do you define "accurate"? Have you measured the distortion in both speaker types at various drive levels? |
Tim Weaver wrote on Tue, 06 April 2010 14:40 |
Building from a plan provided by a manufacturer is actually less work than measuring what you have and then halving the volume. |
Paul O'Brien wrote on Tue, 06 April 2010 10:21 |
Nobody in their right mind would buy those JBL drivers for a DIY cab when you can buy high quality drivers with similar capability from B&C and others for 1/2 the price or better. If he wants to roll his own have him pick up some B&C TBX100's or Emenince Definimax 4018LF for about $300ea from Parts express and load them in an appropriately sized box. There are other even less expensive drivers he could use too but but output and power handling begins to drop off with the lesser drivers, but then it depends what the needs are, PV Lowriders will come pretty close to these for about $200 a driver. http://www.parts-express.com/wizards/searchResults.cfm?srchE xt=CAT&srchCat=583 |
Tim Weaver wrote on Wed, 07 April 2010 00:38 | ||||
By ear alone. Mostly by comparing different subs while in use. Older SR4719's were pretty decent subs for the day. They would be used in the same fashion that we are seeing SRX728's today. Mid-level club rigs up to regional summer festival stages using a bunch of them under some higher priced arrays. 4719's had a bit of muddiness to them when you got down low. Say under 60 hz. They would really have a loss of cone control (for lack of a better word) when you pushed them with pedal tones. Low key riffs, and 5 string bass would not be reproduced faithfully. The SRX728 is an improvement on an order of magnitude compared to the 4719, but still exhibits some of these traits. These cabs have a ton of output though so they get paired up with some higher end array cabinets in order to fill riders. I've seen them under hangs of vertecs a bunch of times. Compare though an SRX728 to the Vertec sub 4880 and no one would argue with you that the vertec sub sounds better, hits harder, and goes lower with more authority. Even the Dual 15 4882 will run circles around the 728, and it gives up a good deal of displacement to the dual 18. Bass lines are quite faithfully reproduced with these cabs. The tbx100 from B&C is more in line with a high end arena rig subwoofer than it is the club level SRX type box. If you build a proper box for it, it will give you everything you would expect from an A level subwoofer. That's what I mean by "more accurate". It gives me more of what I want and less of what I don't.... |
Tom Reid wrote on Wed, 07 April 2010 10:17 | ||
If power compression and heat are issues, the 2268h will rule over the 1/2 priced baskets. Differential drive woofers will take a magnitude of heat above the competition. |
Jeff Wheeler wrote on Wed, 07 April 2010 15:46 |
I am real partial to the 2268 drivers because I already own them, but I am going to take Charlie's suggestion and spend some time with WinISD to see if the B&C drivers come out significantly ahead. I only did the 18TBX100 real quickly so far, to see if it would be hard to make it -3dB at 35Hz, and I have an Xmax problem, but I will be able to spend more time on it this weekend and see if it is solvable. |
Matt Errend wrote on Tue, 06 April 2010 20:46 | ||
That has to be the P-P spec, otherwise the surround would be much much beefier. I would assume that the "real" xmax is 11.5mm, in relation to the other drivers listed. |
Tom Reid wrote on Wed, 07 April 2010 08:26 | ||||||
VT8880 uses are redesigned 2268h (aptly named 2269h) that was designed to extend low frequency response. Otherwise the drivers are mechanically identical. The same applies to the 15" version of the VT sub. There's nothing wrong with B&C drivers. I'm a fan, and have replaced some beloved JBL drivers with B&C product. However, the JBL will produce more output with less distortion and handle more heat. |
Art Welter wrote on Wed, 07 April 2010 18:37 |
David, The 4018LF has an Xmax of 7.9 mm. The B&C 18TBX100 has an Xmax of 10 mm. According to your sim, they both have exceeded Xmax with 2kW. Art Welter |
Adam Schaible wrote on Wed, 07 April 2010 17:41 |
I know that much/any power in the 30hz area makes them sound like total shit (srx 728) .. but this is sine wave's - like 20 volts. That probably says just as much about the box as the driver, just my experience. I didn't have the grill off to measure, but it didn't look like 1.75" peak to peak and they definitely distort severely at that level. |
Art Welter wrote on Wed, 07 April 2010 19:14 | ||
20 volts into 4 ohms is around 100 watts. Was your observation outdoors? What was the nature of the “total shit”? Was it frequency dependent? Box rattle, cone flap, harmonic distortion? Both cones sound the same? |
Adam Schaible wrote on Wed, 07 April 2010 18:21 |
I don't expect it to respond well at 30hz, just saying the extreme xmax didn't seem to help distortion below box tuning. |
Adam Schaible wrote on Wed, 07 April 2010 21:34 |
...XMax doesn't really help above fb ... |
Adam Schaible wrote on Wed, 07 April 2010 21:53 |
You really like to take things out of context. +/- 8mm is fine. 23mm doesn't seem necessary. |
Art Welter wrote on Wed, 07 April 2010 23:37 |
David, The 4018LF has an Xmax of 7.9 mm. The B&C 18TBX100 has an Xmax of 10 mm. According to your sim, they both have exceeded Xmax with 2kW. <snip image> The 2268 is no where near its rated Xmax of 23 mm, could you check what its output level would be when you reach that excursion ? Art Welter |
David Morison wrote on Thu, 08 April 2010 06:29 |
Not trying to knock the JBL, I'm sure it is a better driver, but just wanted to help show some potential benefits of the other drivers - i.e. getting down to the target 35Hz range in a smaller box, albeit with some trade-offs. Regards, David. |
Paul O'Brien wrote on Thu, 08 April 2010 09:53 |
All this discussion about which driver is superior is sorta missing the point here though. The customer in question won't spend big money and by the sounds of it both he and visiting bands are more impressed with quantity than unseen quality, so wouldn't it make more sense to give him a pair of double 18's with slightly less cutting edge but still very good drivers for about the same cost? If the main source music is typical rock band stuff then uber low response isn't needed anyway so the B&C or Definimax drivers would be more than sufficent. |
Art Welter wrote on Wed, 07 April 2010 23:37 |
David, The 2268 is no where near its rated Xmax of 23 mm, could you check what its output level would be when you reach that excursion ? Art Welter |
Adam Schaible wrote on Thu, 08 April 2010 07:23 |
That said, anyone have experience with the B&C 21SW152? Doesn't Yorkville use this in one of their subs? |
Jeff Wheeler wrote on Thu, 08 April 2010 12:58 |
I am satisfied with the cabinet dimensions of the SRX subwoofers. I suspect the box could shrink and change vent dimensions, and the low-end be beefed up with EQ, to still produce useful output if you really wanted a smaller cabinet. I am not convinced there is any compelling reason to use a different driver. This will be a huge upgrade from the current subs anyway. |
Paul O'Brien wrote on Thu, 08 April 2010 09:53 |
All this discussion about which driver is superior is sorta missing the point here though. The customer in question won't spend big money and by the sounds of it both he and visiting bands are more impressed with quantity than unseen quality, so wouldn't it make more sense to give him a pair of double 18's with slightly less cutting edge but still very good drivers for about the same cost? If the main source music is typical rock band stuff then uber low response isn't needed anyway so the B&C or Definimax drivers would be more than sufficent. |
Jeff Wheeler wrote on Thu, 08 April 2010 14:46 |
The price of comparable drivers is about the same honestly. Two cheaper drivers, like the 4018LF, also cost about the same as one 2268H. A pair of them might look more efficient than one 2268H on paper / in WinISD, but once you heat them up that is no longer true. While it is correct that bar-bands and patrons "hear with their eyes" and Art's remark is not lost on me, I do not think I want the owner to spend more money on that "look factor" when he can get what he needs in a single 18, which is actually what he has now (though they are cheap Pyle Pro subs.) He has a whole lot of "sounds like shit factor" to worry about before he spends time and money making it look impressive. It does need to go to 35Hz because for example, in April the venue calendar includes: * 3 nights with one band each * 2 nights with "dance music" / DJ * 13 nights with karaoke I think their entertainment strategy is totally wrong for a 200-capacity venue but that's a larger issue and one that he does not listen to anyone about. But in any case, he put the house PA in to save money on the DJ/karaoke bullshit, which occupies way more dates on the calendar, so if it cannot do that effectively there is no point in upgrading. |
Adam Schaible wrote on Thu, 08 April 2010 15:19 |
I wouldn't be so quick to discount the 4018lf. 1:1 they might not fare as well as the 2268 but 2:1 .. I think you're mistaken if you believe a single 2268 will be more efficient or handle more heat. True, a 2268 has two voice coils, but so do 2 4018's. I have my doubts that differiental drive is 200% more efficient at dissipating heat than a standard VC. Look at some charts Silas has made with his dual 4015lf sub in comparison to commonly available production subs if you have the time. |
Jeff Wheeler wrote on Thu, 08 April 2010 14:43 | ||
The 2268H is -3dB from power compression at RMS power, while most cheap sub drivers are roughly -6dB, including a lot of Eminence products. Also the 4018LF runs out of Xmax much more easily than a 2268H, and that is a legitimate consideration for DJ-duty subs, much more so than subs that are used for kick drum and a little bit of bass guitar. Seriously, there is no comparing cheap Eminence shit to serious sub drivers. Eminence makes plenty of good things, but the stuff you can buy off Parts-Express, you get what you pay for. A $200 driver is a $200 driver, and a $400 driver is, not surprisingly, about twice as useful. Oh, and Silas's double 15 is not for this kind of use either. I do not doubt his ingenuity and I am sure he makes plenty of money with those subs, but there is a huge difference between a kick drum sub and a good DJ-duty sub, and Silas' double 15s lie somewhere in-between. |
Art Welter wrote on Thu, 08 April 2010 22:03 |
In simple terms, 2000 watts to one 2268H, would be equaled with 500 watts each into a pair of 4018LF, or B&C 18TBX100. I would not want to bet that the 2268H, even with it’s heat wicking design, would exhibit less thermal compression at 2000 watts than the other speakers would at 500. |
Silas Pradetto wrote on Fri, 09 April 2010 14:40 |
I have personally destroyed a pair of 2268H woofers (in SRX718 boxes) powered on 1 channel of an IT8000 with no limiters set, but no clipping; this was with dance music for a 3-hour event. They failed about 10 minutes from the end. So even with 2000 watts peak per driver, they can still die like any other woofer. |
Adam Schaible wrote on Thu, 08 April 2010 15:19 |
I wouldn't be so quick to discount the 4018lf. 1:1 they might not fare as well as the 2268 but 2:1 .. I think you're mistaken |
Jeff Wheeler wrote on Sat, 10 April 2010 15:15 | ||
I finally got around to trying this in WinISD today. Obviously my post is all relevant "on paper" only, as I have not built and listened to these potential subwoofer options. The 4018LF reaches Xmax at 50% power somewhere between 40Hz and 50Hz in every box/vent configuration I tried that is -3dB at 30Hz or even 35Hz. It gets really close to Xmech at 100% RMS power and obviously has no room to peak. Crappy driver or else the first dozen boxes I tried in WinISD were just totally wrong. |
Art Welter wrote on Sat, 10 April 2010 18:55 |
Sounds like you are designing too low Fb for the 4018LF with high power. |
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The SRX 728s is not flat to 30, as JBL’s “Frequency Response” shows. |
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A half version of the 728 would have 6 dB less output, at 3200 watts it would put out 130 dB compared to the dual 4018LF putting out about 132 dB with 1600 watts. |
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I still am partial to the Lab 12 (about $150 per) , as it goes lower than the above speakers in a cabinet half the size, the green trace is a Lab 2x12” in a 7.76 (gross) cubic foot box. |
Jeff Wheeler wrote on Sun, 11 April 2010 01:29 |
True, my simulated box is still a little wrong, as I do not know the driver displacement. Also I've thought about making it a bit larger and tuning the box a little lower since the driver is capable of doing it. |
Jeff Wheeler wrote on Sat, 10 April 2010 18:29 | ||||||||
Yes, I can figure out how to make the speaker go low, or get loud, but not both. I suspect a small 6th order bandpass box would work better but at the expense of requiring more corrective EQ and a more complex box.
True, my simulated box is still a little wrong, as I do not know the driver displacement. Also I've thought about making it a bit larger and tuning the box a little lower since the driver is capable of doing it. I am not sure how to determine if such a modification would make a different box incompatible with an OEM box. Should I be looking at the difference in output phase shift?
If they both had a similar power compression curve, but I think it is safe to say they do not.
I remembered your posts on this subject and it didn't take me long to come up with something that looked feasible. I don't know if I can coax the prediction into looking so much better than the 718S that it's worth making a change from something that is essentially a "de-badged box," but compatible with the real OEM ones that I own, to a true DIY; but I will give it more thought. |
Jeff Wheeler wrote on Sun, 11 April 2010 01:29 |
True, my simulated box is still a little wrong, as I do not know the driver displacement. Also I've thought about making it a bit larger and tuning the box a little lower since the driver is capable of doing it. |
Elliot Thompson wrote on Mon, 12 April 2010 07:22 | ||
Jeff, The JBL 2268H's xmech (not xmax) is 23 mm one-way peak or 46 peak to peak. You can estimate 11.5 mm +/- of available xmax. Based on my records, it is the replacement for the JBL 2241, which offers 3 mm peak (or 6 mm peak to peak) in terms of x-mechanical damage over the JBL 2241 (20 mm peak or 40 peak to peak). It offers a 3-inch dual voice coil and is rated 800 watts getting pink noise ranging from 30 - 300 Hertz. Skimming through the threads I am not sure where the wattage recommendation came about however, for DJ purposes you will lose this driver if you feed it over 1000 watts. The voice coil is small and the x-mechanical is no better than other 18-inch drivers offering voice coils ranging from 4 – 5 inches. Also, if you are going to use WinISD, use the pro version. Best Regards, |
Art Welter wrote on Mon, 12 April 2010 17:49 | ||||
Elliot, It would not be the first time I have seen JBL publish conflicting specifications, but the June 9, 2009 TS LF Parameters & Definitions lists the 2241 as 7.62 mm Xmax, 600 watts, and the 2268 as 23 mm Xmax, 1200 watts. No Xmech figures are given. I am curious as to whether the 2268 specs are correct, it would be interesting to see the results of an excursion test on an actual speaker. Art Welter |
Bill Burford wrote on Tue, 13 April 2010 10:20 |
So where do you think the cone is at peak power? maybe during a rock kick? |
Bill Burford wrote on Tue, 13 April 2010 14:37 |
This is why I love this site!!!! people just love to argue with you even when you are asking a question. I said BANDS THAT USE SAMPLERS AND SUB HARMONIC SYNTHS ON THEIR BASS |
Bill Burford wrote on Tue, 13 April 2010 14:37 |
ps. max excursion probably occurs at MIN impedance |
Bill Burford wrote on Tue, 13 April 2010 15:20 |
ha ha.. I have no idea what I'm talking about. I still haven't said anything that is contradictory to anything anyone else has said. |
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(sarcasm) and (more sarcasm) |
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another hobby |
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Up a few posts you ask a question. People try to answer it. |
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You say they're wrong and that you know the answer. Then later on you restate and agree that it was an unclear question. Then you say people were picking on you by putting strange conditions |
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on the circumstances and that your question was perfectly valid in the first place. |
Elliot Thompson wrote on Mon, 12 April 2010 21:46 |
Art, It seems JBL purposely marketed the JBL 2268H with a high xmax however, never explained it is based on xmax damage. In order for the JBL 2268H to offer a 23 mm xmax, the efficiency would be very low since all of the coil will be sitting outside the magnetic gap. Yet, it offers an no.% of 2.8 The numbers are based directly from the engineer’s specifications. I would imagine this is before marketing got their pretty little hands on it. There is no xmax rating on the engineer’s sheet. However it clearly states, “Xmax, damage 23 mm peak before the spider bottoms on gap sleeve.” It also states, “Special Notes: JBL 2241H Replacement in Neo Differential Drive line of transducers.” It seems the JBL 2241 offers the mathematical xmax. As we know, manufactures were more conservative on their specifications when the “2241” was classed JBL’s best decades ago. Today, that 7.62 mm measurement would be marketed as 9 mm taking distortion into account. Best Regards, |
Jeff Wheeler wrote on Tue, 13 April 2010 16:04 |
My experience emailing JBL for spec help has been mixed, but I will try that and see what they say. |
Art Welter wrote on Tue, 13 April 2010 22:49 | ||
Elliott, Your JBL engineering note quote does sound convincing that the 2268H does not have substantially more Xmax than other drivers, in which case the lesser power compression due to double the voice coil surface area (and lighter weight) would be the main advantage. One correction to a previous post of mine, the 2268H is only 800 watts(PE), the "Ultra Long Excursion" 2269H is 1200 watts (PE). I found no Xmech figures for JBL differential drive speakers other than on the VT4880A spec sheet, which states an 89 mm (3.5”) maximum peak to peak excursion, in other words a 44.5 Xmech (or Xlim, whichever flavor you prefer) for the 2269H, which is only rated 19 mm Xmax. The 2269H has only a fraction of the efficiency of the 2268H or 2241H, what one would expect from extra long (and heavy) coils that extend well beyond the magnetic gap. This would correspond to the engineering note you mentioned, I’m inclined to agree the 2268H is basically a differential drive dual coil version of the 2241H. In which case a pair of decent Xmax drivers like the Eminence Lab 12, the 4018LF or the B&C18TBX100 will certainly walk over a single 2268H. The Lab 12 has an Xmax of 13 mm, 659 cc Vd. Vd is the amount of air that can be linearly displaced by the speaker, just like in car engines, the more displacement, the more ultimate power. The 4018LF has an Xmax of 7.9 mm, 939 cc Vd. The B&C 18TBX100 has an Xmax of 10 mm, 1188 cc Vd. The 2268H most likely lies right between the two 18”, if it has the same ratio of Xmax to Xlim as the 2269H, it would have an Xmax of 9.82 mm, about 1167 cc Vd. Before laying out the big cash for 2268H speakers, rather than the others, I’d be doing a quick and simple Xmax check to verify what is real, and what is a print mistake. Art Welter |
Bill Burford wrote on Tue, 13 April 2010 16:40 | ||||
you said:
let me stop you right there, they didn't try to answer it. they said I was wrong if anything. but certainly tried to find a problem with the question.
no by getting personal and telling me I need a new hobby other than sound-- or other comments designed to discredit me personally in other threads by the same person.. continue...further, I never said they were wrong. in one spot maybe you could say that, I didn't really say they were wrong but I did say that min impedance is where I thought that max excursion would occur. and I tend to believe that is closer than the max impedance. but that was a separate issue not really related to my question. |
Evan Kirkendall wrote on Tue, 13 April 2010 15:18 |
Bill, There's no arguing going on here. Just stating facts. If you can't figure out that a kick drum is an impulse that creates a good amount of cone movement, then you probably should consider a new hobby. |
Evan Kirkendall wrote on Tue, 13 April 2010 18:02 |
Jeff, I'm sorry this thread is drifting so far off topic. I'm done with this, and hopefully you've figured out what you need to do. |
Art Welter wrote on Tue, 13 April 2010 17:11 | ||
Contacting JBL would be interesting, but I was suggesting you check the excursion yourself, since you have the cabinet, amp, etc. needed to do the test. |
Jeff Wheeler wrote on Tue, 13 April 2010 17:24 | ||||||
Off-topic discussion is often educational. As long as no one asks what kick drum mic I am using, I will keep reading the thread.
I don't understand how I could measure Xmax if it is defined as when the driver begins producing more than 10% distortion vs useful output, except if I measured in a particular cabinet with an analyzer capable of measuring distortion vs program material or generated signal. Incidentally I did briefly look at the 2269 drivers but it looks like they are over-engineered to take a lot of abuse at the expense of efficiency, which is not what I think I need. |
Mike Caldwell wrote on Tue, 13 April 2010 16:24 |
During the course of this thread I could have cranked out pair of double 18's and been listening to them! |