- Now factors in and displays groundplane estimates (1/8th space, 4M distance)
- If between 115 and 118, it is "Reference" output. If above 118, it is "Above Reference"
- This will trump the existing star rating if any of the above criteria is true
- This should bridge the gap in output/star discrepancies when dealing with larger rooms
- Member scores are now in the spreadsheet
- Much more intuitive. Just enter room size, find your subs, and enter qty
- Automatically identifies ULF Score, Stars, and relative Reference Output by ULF frequency
- Now you can factor in the cost of your subs to determine how much your willing to spend or have spent to get a certain ULF perspective (category). I've input the cost of Commercial Subs, but you can also input the cost for DIY subs manually.
- Calculates the cost per SI: This is an indication for the "bang for the buck" of all your subs from a ULF perspective
- Calculates the cost per ULF Star: This is an indication for the "bang for the buck" for your HT from a ULF perspective (factors in room size, subs, and cost)
- I've also tweaked the Star methodology: Your highest star for your lowest frequency carries forward to the other ULF frequencies. Example: If you can reach 5 stars at 10hz, you can reach 5 stars for all ULF frequencies. However if you can only reach 3 stars at 12.5hz and can reach 4.5 stars at 16hz, it will not change the 12.5z rating to 4.5 stars.
- The SI Conversion charts can be found in the spreadsheet by clicking the 'plus sign' above Column L on the ULF Calculator Score tab
I thoroughly enjoy this hobby, and am always looking to expand on it. It's great to see folks excited about their subs and speak about it in these threads! There are so many great ID and commercial options available...and with DIY, the options become limitless.
With so many options, folks try to find the 'perfect' sub...they read past threads, use data-bass.com, and get the help from many AVS experienced members who have gone through this journey before. Once they select their sub(s) and set it up in their rooms, they're back to the forums to tell the world how much they enjoy them.
However, when folks start to compare their point of view with their subs system to others points of views with with other's sub systems, it's hard to understand their perspective of where they're coming from via sub models alone. They all have potentially different sub models and most certainly different listening rooms.
The purpose of this thread is to come up with a score to get us closer to understanding each sub owner's perspective from a ULF standpoint. The goal was to make it a relatively simple score that puts folks in the general ballpark based on their sub system and HT room. It will NOT be perfect. Again, this score will NOT be perfect. There are too many variables that enter into the calculation. However, the hope is that it's a 'fairly decent' assessment to give folks a better understanding of each other's HT ULF perspective.
I've taken a shot a putting together this scoring system. Again, keep in mind that the goal was to come up with a metric that is relatively simple.
Room size in cubic feet / subwoofage in SI
The first thing to include in the metric is the size of your HT room. Your room is such a huge factor of how your sub(s) interact and perform. A dedicated sealed HT room is easy to calculate. However, if your HT is in a shared living area, you may have to factor in that entire living area. A general guideline to determine how much area to factor is:
- If the opening to the next area is approximately less than half the size of the longest wall, then don't include the adjoining space. If it is larger, then include it.
The second thing to tackle with this metric is that everyone has different subs. Should we base it on overall sub displacement? Sounds reasonable, but is riddled with problems. With different designs of ported, horn, sealed, etc. and different driver capabilities (pro-audio, HT, car), pure displacement is not a fair measurement. For example: ported and horn designs will have potentially smaller drivers, but far greater output than their sealed counterparts...which kind of throws displacement out the window.
If not displacement, than how else? Using the great work of Josh Ricci and data-bass.com, I've come up with a way to normalize different model subs by comparing them to some sub standard by using the max output measured by Josh and comparing it to the standard. By using this data, we can look at subs using the same lens and make general comparisons. For example:
At 16hz, the FV15HP (in 1 port mode) has a max output of 104db. The Outlaw LFM1-EX (1 port mode) has the output of 97.5db. That is a 6.5db difference. Meaning, it would take roughly 2 LFM1-EXs to equal the output of 1 FV15HP at 16hz.
In the example above, I've essentially converted the FV15HP to 2 Outlaws at 16hz. That's how the 'conversion' works.
I mentioned sub standard above...the standard I chose to use is the SI (Stereo Integrity) HT18D2 sealed. Why? It's a popular DIY driver right now that has very good performance. It's not the best by any means, but not the worst either. Any sub would have worked that measured to 10hz, I just chose the SI as a lot of people can relate to it....and it has a very short acronym
Now to determine how to convert a db difference (6.5 in the above example), to how many equivalent factors (multiples) is required (2 Outlaws), requires a logrithmic scale based on the below calculation:
- L = 20 log (x)
Where L is the difference in db, and x is the factor (multiple). Everyone can do this in their head, right? Well I've made it easier for you in the conversion chart below:
The table above are the latest listing for max output in data-bass.com. The columns show the # of SI(s) required at each ULF frequency as recorded by data-bass.com.
Also note that the gray shades above indicates that in Ricci's tests, he indicated that port noise occurred; from very apparent to very slight.
The Chart above are ESTIMATED SI conversions.
Here's the methodology I'm using for estimating (this was all derived by looking at data-bass and extrapolating from the measured results). Also, I'm estimating more optimistically in general (benefit of the doubt).
Again, this isn't perfect, but should get us pretty close.
Going from ported to sealed:
- Sealed is aprox. 10db down at the ported subs tune. If the measured result is not exactly at tune, I'll subtract 1-2 db to compensate for the difference: 18hz tune, I'll use 8db down instead of 10db, since there measurement on data-bass is 20hz.
- Example: The FV15HP outputs 108.1 at 20hz. The F15HP is it's sealed counterpart (using the same driver and amp), so I adjust it's 20hz output by 8db (FV15HP's tune is 18hz) to 100.1 at 20hz.
Estimating sealed max output from 20hz
- Looking at data-bass, most sealed subs are down 10-12db at 12.5hz compared to 20hz. Being optimistic, I use 10db down to get to the 12.5hz
- Example: Since I estimated the F15HP at 100.1 at 20hz, based on the above, it's 12.5hz output is 90.1db.
- In order to determine whether or not a sealed sub can dig cleanly to 10hz, I referenced data-bass again. Looking at 20hz, the lowest output where a sealed sub has clean CEA output at 10hz is when it had 99db or higher at 20hz (LMSR12-Sealed). Generally speaking, any sealed sub that produced 99db or higher, was able to get clean output at 10hz.
- To estimate 10hz output, looking at data-bass, most sealed subs are down 4-6db from 12.5hz. Being optimistic, I use 4db down from 12.5hz to get to 10hz.
- Example: Since the F15HP is estimated 100.1 at 20hz (>=99db), I will estimate it's 10hz output. Subtracting 4db from it's 12.5hz estimate puts it at 86.1db at 10hz
- For 16hz, I just took the midpoint between the 20hz output and the 12.5hz output.
- Example: The F15HP at 20hz is 100.1, and at 12.5hz is 90.1. The 16hz output is estimated at 95.1db.
Additionally, I've added a comments in the "Notes" column for additional detail on the estimates.
I've also attached a HT ULF Calculator that will help you calculate your subwoofage in SI(s) if your sub is not listed above, but have a good guess on what the max output (ground plane) might be. I've included examples and the table above in the spreadsheet.
***Note: If your sub and/or driver isn't listed, when you post your score, please list how you estimated the output so I can add it to the list.
Calculating your HT ULF Score (lower is better)
Let's try a few examples:
Room size = 3000 cubic feet
Subwoofer = Epik Empire,
Conversion to SI = 1.1 at 12.5hz
HT ULF Score = 3000 / 1.1 = email@example.com
Room size = 6000 cubic feet
Subwoofer = Dual Rythmik FV15HPs
Conversion to SI = 1.9 x 2 = 3.8 at 12.5hz
HT ULF Score = 6000 / 3.8 = firstname.lastname@example.org
Comparing the two HT systems, you can see that the Rythmik system has a lower score. In this metric, lower is better. It's apparent that the Rythmik HT room generally speaking has more capable ULF at 12.5hz than the Epik room, even though the Epik room is half of the size.
When the Epik room owner speaks about not being enthusiastic about the ULF of a particular movie scene, and the Rythmik room owner loved it, this could help give us perspective on why...
Let me know what you all think! I know it isn't perfect, but if we all start calculating our HT ULF score and comparing with one another, we'll start to see if the metric is any good or not.
Please calculate and post your HT ULF score. I will update the second posts with results.
Edited by dominguez1 - 12/14/13 at 8:30am