Wayne

Would like to ask the board a more specific question.  Looking at sealed subs in the same size as the JL113,   the SVS SB13-ultra makes an interesting comparison.  It's slightly bigger at 3.7 cubic feet vs 3.5 but it's 20 Hz output is about 5 dB lower.  Why is this?

1)  the box volume is similar and the driver is the same size

2) according to data-bass tests the SVS is not amp limited at 20Hz

3) looking at the photos the SVS driver is massive.

What would need to be done to have an ID sub with the same volume and 5dB more output?  Does it come down to just the driver? Why is no one making one?

Thanks

Wayne

1 hour ago, SME said:

 

Long term max is a good candidate for a plot,  I'll generate that when I have some time.

1 hour ago, SME said:

Might as well quantify what can be quantified,  otherwise no plot.  I would say that sub performance is easier to distill into a set of numbers than loudspeakers  where dispersion is key and equalization is more difficult due to direct vs reflected sound. neither of those is an issue for subs playing below 80 Hz.  

1 hour ago, SME said:

I picked 20 Hz as I was looking at small subs,  many of the small ones cant reach 10 Hz but I will plot at 10Hz , 16Hz, and 30 Hz when I have time.

1 hour ago, SME said:

Hoffman's Iron Law can be overcome with brute (motor) force.  The limitation then is how much magnetic flux you can ultimately focus on a coil, and whether the end result is remotely affordable.

FWIW, I spent an excruciatingly long time deciding on which subs to buy for myself.  I had a very specific location and space budget, and wanted the best I could possibly get with that space.  I had to make a custom design.  There was no chart that told me which driver would work best.  I had to consider all the possibilities individually.

37 minutes ago, Kyle said:

Sure, by no means is this wrong and everything on the y-axis is relative so it does work, just means means its windows to a set of dB that makes sense which is already done. Josh has wanted to add this data to the site for a long time now, maybe its time to get it baked in

 

Here is all active commercial subs on data-bass (plus the F113) . Looks to me that linear volume vs log SPL is a decent fit.  The r squared is 0.6684 or a correlation of 82%.  The JTRs also outperform the trend on output at 20 Hz vs size.

6 hours ago, SME said:

Honestly this seems like splitting a lot of hairs.  The CEA scores use a fairly arbitrary distortion thresholds that are only maybe approximately at the limit of the actual usable output of the sub.  The CEA score won't tell you how fast distortion drops as level is decreased, or does it tell you how much additional travel may be present in the driver in which distortion continues to rise but not as rapidly as another sub.

The decision to buy a JL vs. a JTR sub should come down to a lot more than just CEA scores.  Seriously, 3.5 vs 4.6 cubic feet?  If they are the same 3D shape, this is going to be a tiny difference.  In reality if space is very tight, one may fit the dimensions of the room better than the other.

1). If you don’t like to compare CEA scores , what measurable quantifiable data do you suggest?

2). I don’t have data for the jtr s1 (I see other ,larger jtr subs on data-bass)

3).  I suspect that most would rather look at max 20hz (or a lower frequency) output vs cost rather than size.  This would lead to a different set of overachievers.  I find it interesting to see what speaker designers can do with a constrained size, seems like a good design challenge and I wonder if the best subs are close to the limit of what is possible in a small size. All things being equal wouldn’t you prefer smaller subs (at equal performance) as you could fit more of them in your room.   Yes, Hoffman’s iron law says something’s got to give and that would be sensitivity which could be offset with very powerful and efficient amps.

3 hours ago, Kyle said:

I really like this idea and concept of comparing output vs size. I think one shortcoming with this graph is that SPL is on the decibel scale which is not linear, but we can think of box volume as linear. What we should do is convert SPL to Sound intensity (assume sea level for air pressure -- close enough). Once we have a linear scale for output and a linear scale for volume, I think the graph can have more meaning.

 

 

I’m not a speaker designer but I see no reason that the max 20hz output should be linear with volume.  There is a lot more going on here (e.g. the amps have different capabilities, driver excursion is different , etc.) looking at the 3 JL subs which have similar designs the output in dB looks pretty damn linear with volume.

On 8/14/2019 at 10:47 AM, STL D said:

The JTR S1 actually puts a serious smack down on the JL F113 in this metric (output per cubic foot centered at 20hz) being ~5dB less than the S2 but only slightly larger than the JL. The size difference between the two may as well not even exist.

 

19.25x19.25x16.5 for JL

21x21x18 for the JTR. So not even 2" larger in any dimension (as in, even the wife won't notice unless they are sitting next to each other), but sitting around 107dB at 20hz. So 1 actually pretty much would beat two f113s.

I don't see any measurements for the JTR S1 on Data-bass but would be happy to add to the plot.  As far as the size difference not even existing, the JTR S1 is 38% bigger in volume than the JL F113 (4.6 cubic feet vs 3.5 cubic feet)  and based on a simple linear regression on the 3 JL datapoints, I would expect it to do 106dB at 20Hz to be on the same trend as the JL subs.  If it measures at 107 dB for the same test is would be 1dB better than the JL trend.  

and including all active small and medium sized subs (ported and sealed)

For some, myself included size is important.  Using data-bass I plotted all the sealed, active, small and medium sized subs. I also added the measured data for the JL F113 linked above.   When looking at  the plot of CEA-2010 20Hz max SPL vs size the JL subs (E110, E112, F113) are clear outliers offering higher 20Hz output proportional to their size (volume)