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My 8 x RE XXX 18" Subwoofers, IB build
Couldn't pour water out of a boot with instructions on the heel.
Post 1 Updated
 Version 13.1 now available  Member scores are now in the spreadsheet
Post 2 Updated
 Now lists groundplane (1/8 space, 4M distance) for all members
 Using new Star calculation, 2 members ULF Stars have been changed to 5 Star:
 notnyt  5 Star @ 10hz
 archaea  5 Star @ 20hz
The original star rating was pretty decent though...only 2 members changed out of 50+ as a result of the new methodology.
This new methodology is much better however.
***Note, the new method doesn't change any of the estimates for the subs or the ULF score. It only changes the ULF Stars.
Hey just a thought...I think the 1db should be added to the databass numbers for the XV15. Based on Ricci reports that removing the base plate would of yielded another 1db. if I add 1db @ 16hz it gives a SI of 1.2. Which takes my 3 sub setup from 3.0 to 3.6 and drops my ULF score from 800(4stars) to 667(4.5 stars). Which makes sense because I have above reference output according to my SPL meter and REW.
I know this has been mentioned many times on these forums about the 1db, but I can't seem to find it in Josh's reviews. Can you point me in the right direction?
I think you are confusing what they were trying to say. They are talking just adding a driver using the same amp. What you are doing is adding a whole other subwoofer which in fact would add 6 dBs collocated. The same for if one had a Captivator sub, added another Captivator sub right next to it. It would gain 6 dBs. You added driver, amp, and box to get the 6 dBs. If you were to add just a box and driver to that cap and used the same amp you would get 3 dBs of an increase. The argument is over technical wording, so adding another driver gets you 3 dBs, adding identical subs gets you 6 dBs(max of course). Now the SI and UXL are not identical drivers. In my sims I used enough power to bring each driver to xmax at 5hz based on T/s parameters. It shows the differences but in the real world do these drivers really provide what the sims show? Some do, some don't. The best way to find out is build and test for yourself. People say the uxl is awesome because it provides LMS 5400 type performance for half the price, but like you what I don't understand is that the LMS 5400 was 2.5 dBs more than the UXL at 10hz, the UXL was 3 dBs more than the SI, all used the same amp that could destroy them. So why is the UXL such a great bargain if it almost takes two to equal the LMS 5400(which is not twice as much money) same as the SI to the the UXL with a .5 dBs difference? Call me confused as well.
I said several times that I have a full comprehension of the "general" principals at hand. Add another driver and get +3db. Give that driver the same power as the first and you get +6db.
I totally agree with that.
Again, I fully comprehend the principals at hand. But, under what circumstance would you add another sub to the same amp and NOT decrease the load, effectively doubling the power?
Maybe that's it... But, I really don't see how I worded anything incorrectly?
How about coming to a bottomline. Based on the measurements provided on DB, if one had to choose between 1 UXL and 2 SI's, based on the configurations tested, which set up should technically have the output advantage? The UXL is clearly a superior driver over the SI, but when you add another SI into the equation, the numbers I read show that 2 SI's should yield an audible advantage.
My argument is that 2 mutually coupled SI subs, utilizing the same amp should:
1. Provide an audible max output advantage over 1 UXL.
2. Provide lower distortion that the UXL when pushed to the same SPL levels.
Is that not a logical conclusion to draw or am I missing any key points to support my stance?
I agree 100%. Not really feasible for me at this time. Not for several months anyway, but I might jump on a UXL at some point to do a comparison for myself. The thought of whipping together a GH does sound awesome!
Maybe it has something to do with the LMS tech and the BL of the LMS, which indicates that it has the ability to maintain most of its motor force when pushed to its excursion limits. I think I've seen Scott and Bill weigh in on the subject in the past, but can't recall any specific quotes right off hand.
Not sure if you guys realize this, but maybe this has something to do with it:
Let's compare the UXL and the LMSU at 10hz.
The UXL outputs 92.2db and the LMSU produces 94.7db. Let's assume they are both powered appropriately. There is a 2.5db difference in system output.
If you double the UXL and LMSU, you will get 98.2db and 100.7db respectively. There is a 2.5db difference in system output..
If you quadruple the UXL and LMSU, you will get 104.2db and 106.7db respectively. There is a 2.5db difference in system output...
Point being, if you continue to equally add multiples at the same rate for each sub, the difference in output will still only be the difference you had as single subs (in this case, 2.5db); the difference does not compound. Granted, there's many more aspects of a sub than just its output at 10hz, but you get the picture.
Someone correct me if I'm wrong here...
http://forums.audioholics.com/forums/subwoofers/82624powersoundaudioxv15subwooferreview.html
Scroll down to post #9 by Josh.
...There is a 2.5db difference in system output...
Point being, if you continue to equally add multiples at the same rate for each sub, the difference in output will still only be the difference you had as single subs (in this case, 2.5db); the difference does not compound. Granted, there's many more aspects of a sub than just its output at 10hz, but you get the picture.
Someone correct me if I'm wrong here...
You're perfectly right and this is perfectly normal. dBs are a relative scale. You can think of added dBs as a *multiplicative* factor. A factor 2 is 6.02 dB. Factor square root of 2 (1.4142) is 3.01 dB. 2.5 dB is a factor 1.33.
Thus if one LMSU has 33% more output than the UMX at 10 Hz, it stands to reason that two LMSU also have 33% more output than two UMX. Thus the constant 2.5 dB difference with multiples.
Your math is for real quantities like voltage.
Someone correct me if I'm wrong, but dB SPL are sound pressure level relative to the smallest pressure the human ear can register, which is 20 micro pascals. Pressure is directly proportional to cone excursion and voltage, so no, it's not a power or intensity quantity.
My understanding, double the power to get a 3dB increase. Double the distance and you lose 3dB in SPL. Put together a well balanced, kickbutt system and the rest of it is moot.

Since SPL is proportional to voltage, and power is proportional to the voltage squared, doubling the power gives 3 dB more SPL (aka factor 1.41 = sqrt 2). To double SPL one has to quadruple power.
SPL however drops like 1/distance. If you double the distance, SPL drops by half, and this should give 6 dB.
Not sure if you guys realize this, but maybe this has something to do with it:
Let's compare the UXL and the LMSU at 10hz.
The UXL outputs 92.2db and the LMSU produces 94.7db. Let's assume they are both powered appropriately. There is a 2.5db difference in system output.
If you double the UXL and LMSU, you will get 98.2db and 100.7db respectively. There is a 2.5db difference in system output..
If you quadruple the UXL and LMSU, you will get 104.2db and 106.7db respectively. There is a 2.5db difference in system output...
Point being, if you continue to equally add multiples at the same rate for each sub, the difference in output will still only be the difference you had as single subs (in this case, 2.5db); the difference does not compound. Granted, there's many more aspects of a sub than just its output at 10hz, but you get the picture.
Someone correct me if I'm wrong here...
Yessirrrr.
That is one of those "general principles" I was referrig too in the post of mine that you quoted above.
What I was questioning was why that principle would not apply in the UXL vs SI scenario.
Not sure I understand your question. It does apply to the UXL vs SI scenario.
Instead of 2.5db difference in the above example, it would be a 3db difference. The SI is 89.2 and the UXL is 92.2.
If you have 16 SIs (which you do ) and compare them with 16 UXLs, the difference at 10hz comparing those two systems would be 3db.
To get an additional 3db at 10hz from your 16 SIs, you would need to add 6.4 more SIs w/appropriate power; thus 16 UXLs are the equivalent of 22.4 SIs (SI Conversion).
Post 1 Updated  Estimated Conversions (V13.2 now available)
 New estimated value for XV15 (up 1 db to counter base plate measurement)
 New estimated values for XS15, XS30, XV30 as a result of the above (all up 1 db)
 PC12+ now equals PB12+
Post 2 Updated  Member scores
 Basshead and Tenderchkn scores bumped by .5 star as a result of the above
rcohen, let me know what freq you want to represent your ULF score (3.5 star@10hz, or 5 star@20hz)
Fingers crossed I eventually get it built... lol
2x Rythmik FV15HP , 1920 cuft
10 12.5 16 20
NA 505 480 600
1 4.5 4.5 4.5
I am 2.5 at 10hz
3.0 above
Not too shabby
Panasonic 65VT30  Panasonic AE8000 HD PJ  Denon x4100 ATMOS 5.2.4 Emotiva XPA5  PSA MT110 x 3 FL/C/FR  PSB B4's  DUAL PSA XS30  OPPO 103  minidsp  Buttkicker LFE
the SadieMax HT build thread  my first build
3 Triax's
10 hz  565  4.5
12.5 hz  520  4.5
16 hz  542  4.5
20 hz  619  5.0
I am surprised that the S2 is rated so much higher than the triax given the triax has more displacement and the same power.
Would love to see both tested for cea numbers to see if the calculations here hold.
3  JTR 228's LCR (game room)
4  DIY Sound Group V8 Coaxials in slanted boxes (game room)
4  PSA Triax's (game room)
3  DIY Sound Group V8 Coaxials in Ported Boxes for LCR's
2  SVS SB13+'s (living room)
1  SVS SB12NSD (bedroom)
Today, in speaking with Brian, he commented the FV15HP was 10dB down at 10Hz and then it pretty much drops like a rock.
dominguez1, with this information, can your figure out a SI factor for the FV15HP at 10Hz?
No because it could not pass a clean 10hz signal during 2m rms max burst testing. The XV15 will extend 12hz in room but it will not pass a clean 12hz signal 2m rms ground plane. The ULF thread is based off of databass 2m rms ground plane, so its only fair to calculate a SI factor based on the lowest frequency the sub will pass.
No because it could not pass a clean 10hz signal during 2m rms max burst testing. The XV15 will extend 12hz in room but it will not pass a clean 12hz signal 2m rms ground plane. The ULF thread is based off of databass 2m rms ground plane, so its only fair to calculate a SI factor based on the lowest frequency the sub will pass.
Not arguing, what's considered a clean signal? Is it <10% THD?
Does a second or third subwoofer change or add to the equation in any form?

Haha thanks BeeMan
Room sounds fantastic. I have HUGE plans for a second sub. But I am just trying to convince the wifey to let me have one (it's our living room this is all set up in. I just won the battle for some room treatments so.
But I'm trying hard hahah
This is the only graph I have at the moment.
This shows the sub with and and without xt32
Panasonic 65VT30  Panasonic AE8000 HD PJ  Denon x4100 ATMOS 5.2.4 Emotiva XPA5  PSA MT110 x 3 FL/C/FR  PSB B4's  DUAL PSA XS30  OPPO 103  minidsp  Buttkicker LFE
the SadieMax HT build thread  my first build

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