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How does the VTF2 MK4 compare to the Outlaw LFM1EX? Are there any ground plan measurements that you know of, or are there any comparisons to the VTF15 that you can make (e.g. 6db down at 20hz, etc)?
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Can someone please help me out . This sounds like a cool idea but I admit, that I am having a hard time trying to figure out how to do it for my system. I have a single SubMersive HP(2400 watts dual 15in drivers) in a 1000cf room. Can someone figure out what my SI number would be? Thanks
P.S, I guess if I have to specify a frequency it would be 15Hz or 10Hz..
Ok...before we start estimating the submersive output, let's make sure we keep this in context of this thread and the ULF score:
Whatever the number we land on regarding it's output, it is NOT meant to be used for anything else except this thread. In other words, you CANNOT compare it directly to any other sub based off what we come up with in terms of the Submersive having more or less output that x sub. I'd say it has no meaning outside the context of this thread.
Having said that.......
To estimate subs, I suggest we give it a range, from low to high. So, if we start with a low estimate and determine what that is, and then maybe add 6 more dbs for the high estimate. That's a 6db swing...I would think the true max output number would fall within that range. By coming up with a low and high number, we could take the average and use that as the max output number for the purposes of this thread.
The best way to estimate its output would to find some data from Seaton's website that would give us some idea. If nothing there, we could start comparing to databass tested subs.
MikeD, you want to take the first shot? Make sure and walk us through your logic. I have some guesses as well, we can see if we are thinking the same way.
Calculating piston excursion, the SI18 was moving 19.3mm to hit 89.2dB @ 10Hz 2m burst.
Assuming an Sd of ~0.08m^2 for the SubM's 15" (typical), and allowing it to move 19.3mm (same as the SI18), you get 92.1dB @ 10Hz 2m.
That's probably as close as you'll get without more accurate Sd and Xmax specs/measurements.
Using the same formula, the LMS5400 was moving 35.5mm at 10Hz to hit 94.7dB @ 10Hz 2m.
SPL = 112 + 10 * log(4 * pi^3 * Ro / c * (num * Vd)^2 * f^4)
The RE XXX was in a box much too small for it so as you keep pumping power into it the THD rose rather than the volume. Also remember room gain will decrease THD and increase spl so as Bosso and others have said it is the audio free lunch!
Ricci and Japandave have the most disacement by far so it all depends on their room sizes. Notnyt has awesome displacement as well but his room is much bigger than ours so even though his score won't be as low you can rest assured reference levels is a piece of cake! He has measured to 130 dBs in that big room! I have hit 130 dBs as well but my room is tiny in comparison. I have had many bass heads come to my theater an mention how that can't believe how much bass they feel on concrete floors. I have been thinking about removing my back row and putting the front row on a riser for one helluva kick butt 7.1 experience.
My computer at the office has all the good stuff so I can get the T/S parameters loaded into winisd too. I will so the sims of how single drivers all compare to each other using a sealed enclosure at .707 and power for Xmax at 5hz. I already know the SI hits 95.2 dBs at 10hz with 900 watts.
AVRYamaha A830
amps5 Adcom 555 in 850 watt monoblock mode
sub ampSanway FP14K
LCRDual stacked BFM DR250's
Surrounds Dual stacked BFM W10's
subs12 SI 18's ported 6hz.
My computer at the office has all the good stuff so I can get the T/S parameters loaded into winisd too. I will so the sims of how single drivers all compare to each other using a sealed enclosure at .707 and power for Xmax at 5hz. I already know the SI hits 95.2 dBs at 10hz with 900 watts.
Sounds about right if that's 1m, it matches the databass measurement.
ULF is simply moving air, no? The SubM is a dual 15" with ~20mm throw.
Calculating piston excursion, the SI18 was moving 19.3mm to hit 89.2dB @ 10Hz 2m burst.
Assuming an Sd of ~0.08m^2 for the SubM's 15" (typical), and allowing it to move 19.3mm (same as the SI18), you get 93.1dB @ 10Hz 2m.
That's probably as close as you'll get without more accurate Sd and Xmax specs/measurements.
SPL = 112 + 10 * log(4 * pi^3 * Ro / c * (num * Vd)^2 * f^4)
93db at 10hz for the SubM? I was guessing 92db, so we are close!
If MK's calcs are right, the FTW21 is around 95db@10hz. 2 15's with a 2025mm throw do not match the displacement of the FTW21. Nonetheless, if we use 95db as the high range, and subtract 6 for the low range, that would mean the true number would exist between 89db and 95db. If we split it down the middle, it's 92db.
EDIT: I like your method better
So MikeD, here's what I calculate using 93.1@10hz
Room size in cubic feet  1000  
Hz  SI  Sub/Driver  Your Sub's lowest freq's max output (ground plane)  dB Difference  Equivalent SI(s)  Quantity  Total SI(s)  HT ULF Score (cf per SI) 
10  88.6  SubM  93.1  4.5  1.7  1  1.7  588 
4.5 Star territory!
Love those small rooms!
So MikeD, here's what I calculate using 93.1@10hz
Room size in cubic feet  1000  
Hz  SI  Sub/Driver  Your Sub's lowest freq's max output (ground plane)  dB Difference  Equivalent SI(s)  Quantity  Total SI(s)  HT ULF Score (cf per SI) 
10  88.6  SubM  93.1  4.5  1.7  1  1.7  588 
4.5 Star territory!
Love those small rooms!
Just to show everyone how the margin of error works:
If we assume the true max output exists between 90.1db and 96.1db, his ULF score would be between 435 and 833.
From a ULF Star standpoint, that is either 4 stars or 4.5 stars.
That is why I say we do not need to be that exact as it will typically result in plus or minus a half a star.
AVRYamaha A830
amps5 Adcom 555 in 850 watt monoblock mode
sub ampSanway FP14K
LCRDual stacked BFM DR250's
Surrounds Dual stacked BFM W10's
subs12 SI 18's ported 6hz.
They saw 86.9dB @ 10Hz 2m, and should have moved 15.6mm to do so.
AVRYamaha A830
amps5 Adcom 555 in 850 watt monoblock mode
sub ampSanway FP14K
LCRDual stacked BFM DR250's
Surrounds Dual stacked BFM W10's
subs12 SI 18's ported 6hz.
Think they r close to the Outlaw but I'm on the road so ill do some digging once I get to the hotel. Thinking mine and the VTF15 share same amp.
Edit: VTF 15 amp had 100 more watts RMS than VTF2.4
Just to show everyone how the margin of error works:
If we assume the true max output exists between 90.1db and 96.1db, his ULF score would be between 435 and 833.
From a ULF Star standpoint, that is either 4 stars or 4.5 stars.
That is why I say we do not need to be that exact as it will typically result in plus or minus a half a star.
Ran the numbers again to check, it's actually 92.1dB.
Also, shouldn't the SI be 89.2dB at 10Hz yielding a difference of +2.9dB? 1.4 multi for a score of 714?
Also, your "margin of error" of +/3dB would require our guesstimatumption of the SubM's Xmax to be anywhere from 13.7mm to 27.3mm. I think we could safely narrow that window, considering we know the SubM is roughly a 1920mm driver.
Call it a range of 1622 and that gives you 90.493.2dB, or 625909... also 44.5 stars. Another way to look at it is our assumption of SubM Xmax needs to be 20.3mm or greater to bump it into the 4.5 star category, and it's probably a safer assumption that it's <20.3mm, so 4star based on 92.1dB is a good rating.
On another note, the UXL18 moved 30.5mm to hit it's 92.2dB at 10Hz, so based on Sd we'd probably expect the same excursion from the FTW21 which calculates to 96.2dB.
I'm just thinking that displacement is all we need to really work about (Vd), and just assume proper sized boxes and sufficient power like Ricci tests because it adds so much more complexity to take that into consideration for each and every setup. Not to mention most setups' combined chain rolloff is going to knock of significant dBs by 10Hz but we can't really take that into consideration for each setup either.
Ran the numbers again to check, it's actually 92.1dB.
Also, shouldn't the SI be 89.2dB at 10Hz yielding a difference of +2.9dB? 1.4 multi for a score of 714?
Also, your "margin of error" of +/3dB would require our guesstimatumption of the SubM's Xmax to be anywhere from 13.7mm to 27.3mm. I think we could safely narrow that window, considering we know the SubM is roughly a 1920mm driver.
Call it a range of 1622 and that gives you 90.493.2dB, or 625909... also 44.5 stars. Another way to look at it is our assumption of SubM Xmax needs to be 20.3mm or greater to bump it into the 4.5 star category, and it's probably a safer assumption that it's <20.3mm, so 4star based on 92.1dB is a good rating.
On another note, the UXL18 moved 30.5mm to hit it's 92.2dB at 10Hz, so based on Sd we'd probably expect the same excursion from the FTW21 which calculates to 96.2dB.
Yes, you are correct. I was using a different 'unreleased' version of the calculator when I was using the min voltage as the input. That lowered it to 88.6.
Using 89.2db for the SI and 92.1 for the SubM:
Room size in cubic feet  1000  
Hz  SI  Sub/Driver  Your Sub's lowest freq's max output (ground plane)  dB Difference  Equivalent SI(s)  Quantity  Total SI(s)  HT ULF Score (cf per SI) 
10  89.2  SubM  92.1  2.9  1.4  1  1.4  714 
So yes, 714 is the correct score, putting it in the 4 star category. Good catch! Thanks!
I like you're thinking with the xmax...makes sense.
For the FTW21 at 96.2, that would give me a score of 432@10hz, and 232@12.5hz. Still the same 4.5 and 5 star categories, respectively.
AVRYamaha A830
amps5 Adcom 555 in 850 watt monoblock mode
sub ampSanway FP14K
LCRDual stacked BFM DR250's
Surrounds Dual stacked BFM W10's
subs12 SI 18's ported 6hz.
Ok...before we start estimating the submersive output, let's make sure we keep this in context of this thread and the ULF score:
Whatever the number we land on regarding it's output, it is NOT meant to be used for anything else except this thread. In other words, you CANNOT compare it directly to any other sub based off what we come up with in terms of the Submersive having more or less output that x sub. I'd say it has no meaning outside the context of this thread.
Having said that.......
To estimate subs, I suggest we give it a range, from low to high. So, if we start with a low estimate and determine what that is, and then maybe add 6 more dbs for the high estimate. That's a 6db swing...I would think the true max output number would fall within that range. By coming up with a low and high number, we could take the average and use that as the max output number for the purposes of this thread.
The best way to estimate its output would to find some data from Seaton's website that would give us some idea. If nothing there, we could start comparing to databass tested subs.
MikeD, you want to take the first shot? Make sure and walk us through your logic. I have some guesses as well, we can see if we are thinking the same way.
OK. I read all the posts regarding my situation and it makes sense. And I understand that it would limited to the context of this thread. There are people who have posted FR charts on Mark's forum years ago, but they were not max charts. Just regular charts showing a normal FR. TBH, even though I like this stuff, I know Mark is not into this angle of everything. I mean, I have numbers and charts that made my jaw drop and it's what caused me to get this sub, but even though they are very old, I am not sure I should share them in open forum. So maybe I got too excited and jumped the gun here. If it is not going to be equal to the way these are measured, and we really can't compare it to the other subs, maybe we shouldn't even try. Thanks for your efforts though .
I agree that we shouldn't definitively compare the estimated output numbers outside of this thread to compare subs. If you're comparing subs to determine which sub has more output and a certain frequency, then the only way to do that is to have a consistent test methodology done by the same tester in the same test environment using the same test equipment; this equals Josh and databass.com.
BUT, if you want to get a general idea of how your HT room compares to other HT rooms, you do not need to be that exact with the output. As shown above, a 6db range only affects the ULF Star rating by a half a star. The ULF scoring and categories are fairly resilient to these types of ranges. Said a different way, the categories aren't that sensitive to fairly significant db swings when you factor in room, logarithmic comparisons, and the category spread.
I think most would agree that we could get within a 6db range of the true max output of a sub by using other similar subs' data, displacement/TS params, and sub design. Not perfect by any means as many have pointed out, but for the purposes of this thread it doesn't have to be; it ultimately results in being accurate to within a 1/2 star in the majority of cases.
At the end of the day the ULF Star rating will give you an idea what kind of HT ULF experience you have compared to other members here.
I agree that we shouldn't definitively compare the estimated output numbers outside of this thread to compare subs. If you're comparing subs to determine which sub has more output and a certain frequency, then the only way to do that is to have a consistent test methodology done by the same tester in the same test environment using the same test equipment; this equals Josh and databass.com.
BUT, if you want to get a general idea of how your HT room compares to other HT rooms, you do not need to be that exact with the output. As shown above, a 6db range only affects the ULF Star rating by a half a star. The ULF scoring and categories are fairly resilient to these types of ranges. Said a different way, the categories aren't that sensitive to fairly significant db swings when you factor in room, logarithmic comparisons, and the category spread.
I think most would agree that we could get within a 6db range of the true max output of a sub by using other similar subs' data, displacement/TS params, and sub design. Not perfect by any means as many have pointed out, but for the purposes of this thread it doesn't have to be; it ultimately results in being accurate to within a 1/2 star in the majority of cases.
At the end of the day the ULF Star rating will give you an idea what kind of HT ULF experience you have compared to other members here.
AVRYamaha A830
amps5 Adcom 555 in 850 watt monoblock mode
sub ampSanway FP14K
LCRDual stacked BFM DR250's
Surrounds Dual stacked BFM W10's
subs12 SI 18's ported 6hz.
That is basically all I was looking for. But I am assuming that you would need some sort of max out put. There is no way I could even try to test that in my small rooms and the info I do have is NOT from my room but it does show max out put. Now, not with me, but at work, I do have the original SubMersive displacement numbers. If you were to use to calculate that on the subs you have, then I would be able to compare it myself that way. But I don't know how many subs that are listed have displacement numbers. Thanks again for trying . But displacement is the only way I would be able to compare my bass system with others here. Besides FR charts which I have.
Actually, displacement is still not accurate by itself, as you have different designs like ported, horn, etc. They would have lower displacement, but higher output at tune. Like I said, the best measurement is testing by josh, but until then, estimating is all we have. Fortunately IMO, a scoring system like this can get us pretty close.
You're at 4 Stars with a score of 714. Another SubM would get you to 4.5 with a score of 357. A third would get you to 238 in the 5 star territory. This is equivalent to 4.2 SIs in your 1000cf room!
Just to give you an idea of how much subwoofage pop and MK have at 10hz..., you would need 8.4 SIs in that room to get a similar score (119)!!!
What is funny is that the ULF scores only represent capability. If we all watch at reference with flat settings a higher score would be fine. My score with my eD's would have been 252.7 and I had plenty of headroom. I could have halved that system and still play reference. Half of that system would have scored 505.5 at 10hz. So in my room a score of 505.5 is reference capable and 4.5 stars. My new system will be a score of 125 and have much more capability but only .5 stars more. Maybe we need to decrease the range a bit or define what a 5 star system should be? The goal has always been to reproduce what is on the disc which takes 505 but I run hot so in my room I do get much more tactile feelings.
YES! Great point!
Perhaps 4.5 Star is reference playback, and 5 Star is just ULF crazy territory.
Don't get too caught up though in the individual scoring as the metric is missing a lot of variables to start comparing scores directly with other HT systems when you're talking about inroom measurements. This is an anechoic metric; inroom throws a lot more variables in that couldn't possible be compared to others rooms without knowing a whole lot more.
Over the years, I've approached the measurement guys about an inroom metric. Always, I get the "too many variables" "every room is different", etc.
I have 2 problems with those responses; 1) room are not so different and 2) the only variable I've noticed has nothing to do with room size and everything to do with transmission losses.
Housing construction methods haven't changed in the US for a century. There are 2 floor construction methods; slab and subfloor on wood joists, and there are 3 exterior wall methods; sheetrock on frame with siding veneer, sheetrock on frame with brick veneer and sheetrock on frame on masonry foundation. Interior walls are a constant and haven't changed at all in the last 50 years.
IOW, a transmission loss input multiplier would be rather simple to devise since the transmission losses of all of those floor/wall methods is already available from the sound/vibration transmission field.
Here's a graph I put together from several well known member's posted inroom graphs vs their known native response graphs:
I've said over and over that SPL is achieved by adding multiples. It's a known mathematical formula. The room gain curve could be determined and a filter approximating it could be configured in an app like WinISD and the only thing left is to add the transmission losses multiplier.
Although, for example, MKT and myself have a very similar room gain transfer function, block walls have a 50% less transmission loss rating than drywall on studs. And, those ratings do not address <125 Hz, where the differences are much higher.
Model + room gain L/T + transmission loss multiplier = rating number.
There then needs to be a further multiplier for seating distance. That multiplier will vary by frequency because as wavelength increases, Inverse Square Law multiplier decreases.
Model + room gain filter + transmission loss multiplier + seating distance multiplier.
People assume that putting a sub in a room is going to automatically mean that they'll see higher numbers than 2M GP results. Sitting 4M from the sub requires greater than +6dB boundary gain just to equal the 2M GP number from 30 Hz and up, the size of the room being a far lesser factor.
Again, I like what's going on in this thread and thanks to all for the awesome input. I just wanted to throw some known and easily solvable variables into the mix and my opinion that room size should probably not be as big a factor in the calculation as it currently is in the posted calculator. In fact, I personally never consider room size when sizing a system to the stated goals of FR and output.
Bosso, et al,
The way the metric works now is that a halving of room size is the same as the doubling of the number of subs you have (and in terms of the ULF score reduces it by 50%). If you double the number of subs, you get a 6db gain. Therefore, halving the room size equates to 6db gain based on how the metric is constructed.
Is this in the ballpark? Intuitively it doesn't seem that far off, but I have no idea...would like to hear folks thoughts on the matter.
What if you made a 5.5 star rating for any scores below 126?
There then needs to be a further multiplier for seating distance. That multiplier will vary by frequency because as wavelength increases, Inverse Square Law multiplier decreases.
Model + room gain filter + transmission loss multiplier + seating distance multiplier.
People assume that putting a sub in a room is going to automatically mean that they'll see higher numbers than 2M GP results. Sitting 4M from the sub requires greater than +6dB boundary gain just to equal the 2M GP number from 30 Hz and up, the size of the room being a far lesser factor.
Hummm, my near field subs give a ridiculous amount more from a ULF/tactical sensation than my front stage. I've had my front stage amp trip a breaker, but still had my near field subs rocking and I barely noticed a difference in intensity. In fact, given my front and rear boxes are setup with different response curves, I didn't notice my front stage was off until a familiar part of the song was a bit lacking in the midbass department. Other than that, I'd say my near field gives me 90% of my tactical feel...
Oh, and don't get me wrong... that 10% from my front stage is pretty intense. If I was to just play my front stage with no near field, that 10% would still be pretty impressive to some... <Just basing that on the feedback I've received thus far from those that have demoed my space.
Yes, but consider; the larger the space, the further you sit from the subs. Sitting 4 meters vs 2 meters requires 4X the displacement, or 2X the displacement + 2X the power, for the same SPL. The general formula is just that. For a specific formula, much more input is required or there will be no way to calculate a conclusion.
Hummm, my near field subs give a ridiculous amount more from a ULF/tactical sensation than my front stage. I've had my front stage amp trip a breaker, but still had my near field subs rocking and I barely noticed a difference in intensity. In fact, given my front and rear boxes are setup with different response curves, I didn't notice my front stage was off until a familiar part of the song was a bit lacking in the midbass department. Other than that, I'd say my near field gives me 90% of my tactical feel...
Oh, and don't get me wrong... that 10% from my front stage is pretty intense. If I was to just play my front stage with no near field, that 10% would still be pretty impressive to some... <Just basing that on the feedback I've received thus far from those that have demoed my space.
Subjective impressions serve a purpose, but let's take the idea to the extreme. Here's the same sub sitting 1" from the sub and sitting 4M from the sub:
I have included your room gain profile. Maybe you could post the FR @ the seat with Front, Back and Front+Back?
AVRYamaha A830
amps5 Adcom 555 in 850 watt monoblock mode
sub ampSanway FP14K
LCRDual stacked BFM DR250's
Surrounds Dual stacked BFM W10's
subs12 SI 18's ported 6hz.

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