Here in Europe we are going to face a new 'problem' which is called, law. Since it is a fact the youth in general is suffering from hearing damage, caused by these enormous SPL’s that have become 'normal' in the last 10 years + those phones with these killing ear plugs, our governments are passing new SPL laws. For big pop/rock concerts it means measuring equipment that will monitor SPL constantly, including 'transient peaks'. Of course that will result in an even less dynamic sound.
I am very familiar with those tests. I moderated the diy subwoofer area at that site briefly. In fact I have started my own testing last year that is inspired by them but also expands on them. You can see that at the link in my sig. I only have a few tests done but there are 7 more that are done and in the process of being added. Btw you must click on the system or driver name to go to the detailed test data. Anyway enough about that. I urge you to check out the link that Wayne provided.
Wayne do not forget that these tests are at 2 meters not 1 so there is an extra 6db of power involved. Assuming a roughly 90db 1w sensitivity on most, which is probably close enough, puts the power needed for a nominal 110db sweep at 400w. Some were run to a 115db sweep, putting the input power up near 1100w. A few were run even harder than that.
Btw if you have another prosound shootout I would love to attend.
I am very familiar with those tests. I moderated the diy subwoofer area at that site briefly. In fact I have started my own testing last year that is inspired by them but also expands on them. You can see that at the link in my sig. I only have a few tests done but there are 7 more that are done and in the process of being added. Btw you must click on the system or driver name to go to the detailed test data. Anyway enough about that. I urge you to check out the link that Wayne provided.
Wayne do not forget that these tests are at 2 meters not 1 so there is an extra 6db of power involved. Assuming a roughly 90db 1w sensitivity on most, which is probably close enough, puts the power needed for a nominal 110db sweep at 400w. Some were run to a 115db sweep, putting the input power up near 1100w. A few were run even harder than that.
Originally Posted by Wayne Parham
I think your data is bogus.
I challenge you to have your speakers tested side by side with mine using LMS. .
He posted a good explanation of the various contributing factors which cause even and odd order harmonics in speakers. Although LMS provides a nice line on the screen for THD, the method I have used actually shows the harmonic cascade of the test cabinet's distortion pattern. The LMS distortion trace would look the same whether relatively benign (even order) or non-musical (odd order).
After several requests Wayne has not provided any distortion data for Lab 12s in any cabinets other than the 12Pi, yet insists we take his word that their distortion is higher. It appears any data he has for Lab 12 enclosures other than the 12Pi reside only in his head.
My actual measured data seems to conflict with the the data in Wayne's head, ergo it is "bogus".
If Wayne wants to send me his LMS system, I'll be glad to test my cabinets with it for him.
I'd be interested in bringing my cabinets out for a sub shootout, but seeing as the 12Pi is four times the size of the Dual Lab 12, or two of the Keystone cabinets, a one to one test would be "bogus".
A single Keystone with the BC18SW125-4 would be neck and neck with the 12Pi, with the extender it should be louder. I do concede that the 12Pi has lower distortion than my subs 35-100 Hz, though my subs have less 30 Hz distortion.
Art Welter
I think your data is bogus.
I challenge you to have your speakers tested side by side with mine using LMS. .
Wayne has not responded to the data presented in post 81, 86, 92, and 98 with any rational explanation of why he thinks my data is "bogus".bass heads are waiting for a response Art. ?
He posted a good explanation of the various contributing factors which cause even and odd order harmonics in speakers. Although LMS provides a nice line on the screen for THD, the method I have used actually shows the harmonic cascade of the test cabinet's distortion pattern. The LMS distortion trace would look the same whether relatively benign (even order) or non-musical (odd order).
After several requests Wayne has not provided any distortion data for Lab 12s in any cabinets other than the 12Pi, yet insists we take his word that their distortion is higher. It appears any data he has for Lab 12 enclosures other than the 12Pi reside only in his head.
My actual measured data seems to conflict with the the data in Wayne's head, ergo it is "bogus".
If Wayne wants to send me his LMS system, I'll be glad to test my cabinets with it for him.
I'd be interested in bringing my cabinets out for a sub shootout, but seeing as the 12Pi is four times the size of the Dual Lab 12, or two of the Keystone cabinets, a one to one test would be "bogus".
A single Keystone with the BC18SW125-4 would be neck and neck with the 12Pi, with the extender it should be louder. I do concede that the 12Pi has lower distortion than my subs 35-100 Hz, though my subs have less 30 Hz distortion.
Art Welter
I'm not sure we can get too critical of the Home Theater test data, because we don't have sufficient details. Things like efficiency and power would need to be known, But I do think we see general trends. And while I could have sworn I saw the 1M quote mentioned in there, I can certainly believe two meters was the microphone distance. So thanks for the clarification - That's also a believable scale. It's useful for trending, and I think makes clear what SPL and distortion scale these kinds of devices can be expected to work at.
I think probably some drivers are in the 85-88dB/1W/1M range, others probably get up a little north of 90dB. That gives us a reasonable expectation that 100 watts is somewhere in the 105-110dB range. A 90dB/W/M driver at 100 watts would be at 110dB, assuming no compression. And like you said, 400 watts is what it takes to get to the next line up, since each is 5dB apart. Well actually we would need 6dB increments, since four times the power or half the distance is 6dB higher, but round numbers, it's close. So the 115dB lines are probably around ~350 watts, assuming a 90dB driver. That helps set the scale for trending purposes.
I run the LAB12 (an OEM version, actually, machined to fit my cooling plugs) in both vented and horn configurations. I really like it, and definitely do not talk it down. I pretty much depend on it solely for sub duty these days. And ironically, I've been on both sides of the horn/direct radiator argument. I find each kind of system suited for a specific application. personally, I much prefer a direct radiating LAB12 for hom hifi or home theater. It can be used in a relatively small 4ft3 box tuned to 20Hz, providing deeper extenson, a smooth wide passband and adequate SPL output for that environment. It is small enough I can use it in a multisub configuraton, which I prefer. Outdoors, I would rather use hornsubs. They provide much greater SPL output, reduced distortion and need a lot less power. I'd say it takes 6-8 direct radiating LAB12 woofers, whether in a BR or TL, to equal the output of one 12Pi hornsub, and the direct radiators need a boatload of amps to do it.
That's what started this exchange. I don't get to DIYaudio very often, and almost never in the subwoofer forum. But I noticed recently, in my absense, that weltersys has been saying that his dual LAB12 cabinets provide less distortion than my 12Pi hornsub, that the cooling plugs don't work, etc. So I reply back with links to measurement data showing how well the coling plugs work, distortion comparisons between my 12Pi and other designs and what not. When I post links to measurement data and other results, he quotes me and conveniently leaves out the links. But all this notwithstanding, there's one inescapable sniff test that I can't get around, and that's his claim that a pair of direct radiating LAB12's will beat a horn loaded pair of LAB12's with push pull drive and cooling plugs. I mean, WTF?
You're on - I'll set up something with the track. No point in talking about this any further, let's just see what the LMS traces show.
Multiple Threads, same Arguments
Hi Wayne,
From the "Wayne's 12Pi sub" thread, Post #35:
By Wayne Parnham: "...a vented box against a hornsub with the same drivers?"
I think Art is suggesting to compare four of his dual LAB12 subs to one 12Pi.
Weltersys: "...try four of my dual Lab 12 subs to one 12Pi, as they take up 1/4 the truck space."
Or in other words eight LAB12 drivers v. two.
Anyway, do you have a Hornresp Input for your 12Pi Sub that you could share?
Regards,
Hi Wayne,
From the "Wayne's 12Pi sub" thread, Post #35:
By Wayne Parnham: "...a vented box against a hornsub with the same drivers?"
I think Art is suggesting to compare four of his dual LAB12 subs to one 12Pi.
Weltersys: "...try four of my dual Lab 12 subs to one 12Pi, as they take up 1/4 the truck space."
Or in other words eight LAB12 drivers v. two.
Anyway, do you have a Hornresp Input for your 12Pi Sub that you could share?
Regards,
Wayne,
Get your facts straight.
I never claimed that a pair of direct radiating LAB12's will beat a horn loaded pair of LAB12's in a cabinet four times the size, where did you get that idea?
As far as distortion, I have posted data showing my ported 12s having more distortion in the passband, but less at 30 Hz than the 12Pi.
If your ported Lab12 are a 20Hz Fb, in four cubic feet I would expect distortion to be high, at high power, the speaker will run out of Xmax well before Pmax, unlike my 36 Fb alignment.
Post the distortion data of your ported subs here if you have any.
Art Welter
ahh... now things are getting interesting... Tulsa? I'm close enough to make the trip...
Dayton Audio PA 380-8 and Eminence-Kappalite LF3015 are Spec.-wise different animals
Hi,
Agree on one parameter:Both are 15" drivers but...which TH/T-QWP fits both?
b 🙂
Hi,
Agree on one parameter:Both are 15" drivers but...which TH/T-QWP fits both?
b 🙂
Attachments
Actually, this debate is fundamentally about distortion. The weltersys claim I challenged is that his distortion performance is better, not only in the passband but even below cutoff. I think his measurements are wrong. It really doesn't matter if we measure one box or four, we can see what his distortion curve looks like.
But, yeah, we can measure groups too. Of course, we're going to need a lot of power. We have used some good amps each year, but we'll probbaly need to get a lot more of them if we're going to try and run enough direct radiators to keep up with a horn or two. If we try and compare with four or more hornsubs, we'll need a truckload of direct radiators and the city's generator dedicated to the weltersys system.
Good, 'cause it won't. But like I said above, this is really about distortion. You have made claims that I don't believe and I'm calling you on it. The main one is your claim that distortion below the Helmholtz frequency is low:
If your Helmholtz frequency is 36Hz, then I expect distortion to start rising rapidly below that frequency. Should be ramping up pretty steeply by 30Hz or thereabouts.
Of course, we all high-pass at that frequency, so it's academic. But you keep harping on it, and I'm calling you out on that. I further challenge your claims of distortion through the passband, which you initially said was better but I think you're backpeddling a bit now. Still, doesn't matter, let's just line 'em up and sweep 'em.
Ground pounding action...action...action!
Wayne. There is no gray area... Those tests are at 2 meters. Trust me I know this data backwards and inside out. You have rightfully assumed that many of these "Hifi" vented and sealed cabs are going to be in the 90db at 1w sensitivity range with some probably even lower near to 85-88db. I can actually tell you what the efficiency and sensitivity on some of the DIY subs tested there are because i own the same drivers in very similar cabs. These numbers would be at 1 meter. At 2 meters the sub will need an additional 6db of input power to reach that same 90db at the microphone. That puts the drive level at 4 watts not 1w. When you pile on 20db more level into the subwoofer to reach a nominally 110db sweep level, from the base of a 4w input to produce 90db nominal, you are at a 400w power level already not 100w. The 100w sweep level would be more likely to be the 105db one. A 115db sweep at 2 meters from a 90db 1w/1m sub will require about 1,100w. The lower sensitivity subs that are down in the <90db 1w/1m range will require even more power than this. It is no wonder that power compression rears it's head. Obviously we are both doing quite a bit of educated generalizing here. 😉
The only reason that I bring this up is because you seem to be implying that by looking at this data for trends that you can make an educated guess as to how a direct radiator Lab12 cabinet would behave at a certain input power. For instance there is no doubt that distortion is going to skyrocket below the cabinet loading. This has been proven conclusively in every test I have ever seen. In a general sense perhaps you can make some other guesses as to how it will behave above fb, however you have implied that the estimated input power is 4x lower than it really would be by assuming that the tests were conducted at 1 meter when they are in fact all 2 meter tests which will require 4x the input power for the same output level over a 1 meter result. That is all. As far as the whole Lab12 distortion argument I don't have any actual measurment data on that driver in any cabinet so I don't have anything to add.
If you do the prosound shootout I will be there. I could bring any of 3 tapped horns or a BR. I also have a pair of Powersoft K10's if you need some power.
Last edited:
And not to beat this thread to death anymore...
Why are you guys trying to use an RTA to capture the THD of a sine wave at a single frequency still? 😕
There are numerous cheap or even free audio programs (that are also good) that will run a full sine sweep and plot out the THD, the distortion by harmonic or both in a matter of a minute. Holm Impulse, ARTA and STEPS (My favorite but a little rough for high power) all will measure distortion in a variety of ways. Holm Impulse is completely free.
Why are you guys trying to use an RTA to capture the THD of a sine wave at a single frequency still? 😕
There are numerous cheap or even free audio programs (that are also good) that will run a full sine sweep and plot out the THD, the distortion by harmonic or both in a matter of a minute. Holm Impulse, ARTA and STEPS (My favorite but a little rough for high power) all will measure distortion in a variety of ways. Holm Impulse is completely free.
My purpose was not specifically to measure distortion, but to find out why the ss15 didn't line up with the hornresp prediction.
something was going on at 40hz, where I was measuring output that shouldn't be there... and so out came smaart and a sine wave.
Yes, 40hz does sound good to me on that cabinet, distortion or not.
Wayne,
I agree with you, with a HP the output below Fb or Fc is academic.
The only reason I “harped” on the 30 Hz distortion was my data shows the WS Lab 2x12 to have MORE distortion in the passband, and LESS below than the 12Pi, which bears out your “horns have less distortion” statements, but opposes your observation that push pull has the most effect below Fc or Fb.
I gotta calls ‘em likes I sees ‘em.
I only used a pair of Crest CA-9 to power my four 2x12 cabinets, into slight clip results in the speakers hitting Xmax in the 50-60 Hz region. I have put 66 volts sine wave into them in that region, they sounded a bit rugged. Four cabinets will do 104 dBC at 125 feet at 40 Hz with music with two CA-9 driving them.
The BC18SW125-4 loaded Keystone Subs will take a lot more power, they were not getting warm with 77.5 volts of sine wave. The CA-9 bridged mono is not enough power to "light 'em up", but my system has more headroom with them than the WS Lab 2x12s.
The WS Lab 2x12s are for sale, maybe someone from Tulsa will buy them and bring them to the shootout :^).
Art Welter
Welter Systems, Inc.
Attachments
My excuse is four fold, those programs don't run on Macs, (unless I buy Windows which costs money that could be spent on speakers), seems like there are only about 10 people that seem at all interested in distortion, I like seeing the harmonic cascade rather than a single line, and a single tone allows me to measure excursion at the test frequency.
Art
- Status
- Not open for further replies.