“Let our rigorous testing and reviews be your guidelines to A/V equipment – not marketing slogans”
Facebook Youtube Twitter instagram pinterest

Audioholics 2010 Subwoofer Shootout Measurements Overview

by paul December 23, 2010
Contributors: Gene DellaSala
Subwoofers in our shootout

Subwoofers in our shootout

The goal of our most recent subwoofer shootout is to give us as consumers, a reliable and quantifiable way to purchase home theater subwoofers with some confidence that the products we hear and read about are in fact well designed and capable of sufficient output at low frequencies to reproduce both music and movies with the impact and realism that you expect from a well designed and executed product.  The products in this comparison were chosen based on a box size of 6 cubic feet or less, and a maximum retail cost of $2000.  This article discusses our testing methodology for measuring all of the subwoofers. 

Product Entries

Brand

Model

Box Dimensions

Dimensional Volume

Retail Price

Product Description

Rythmik

FV15HP

18" x 24" x 24"

 6 ft^3

$1,300

15" ported servo with 600 watt amp

Funkywaves

FW12.X

24" x 24" x 14.5"

 4.83 ft^3

$1,950

12" ported with external 2000 watt amp

SV Sound

PB12-Plus DSP

25" x19" x 21"

5.77 ft^3

$1,399

12" ported with 800 watt amp

HSU

VTF-15H

25" x 18" x 26"

 6.77ft^3

$879

15" ported with 350 watt amp

Putting your products in the hands of a stranger whom you do not know is risky business.  There are more than a few folks in audio who are more hobbyist than engineer or scientist.  Having your flaws displayed publicly requires a lot of courage.  I can say with a clear conscience, there were no perfect entries.  For a certainty there were excellent, fair and mediocre products.  Some were so mediocre in fact, they withdrew from the competition.  When viewed in that light, keep in mind those left here, are here because they were the best of the batch.  The few people in the audio business who do know me well will not tell you I am critical.  They will tell you I am VERY critical.  My job is basically finding flaws, eliminating them and designing a better product.  A product which may make the typical consumer ecstatic, may draw faint praise from me.

Some years ago when subwoofers were becoming much more popular, while walking the show floor at CES, (the Consumer Electronics Show) I acquired a loudspeaker component (woofer) catalog from a nondescript Chinese driver vendor, who had gone to the trouble of identifying every single one of the woofers pictured in his catalog as “subwoofer”.  In fact, among the dozens of woofers pictured, regardless of the application, or range of usable frequencies covered, they were ALL identified as “subwoofers”.

The use of the term is not necessarily a guarantee you will be buying the real thing.  Please note; there were NO fakes in this reviewer's opinion in our shootout.  All the products submitted represented the best ability to produce, design and source parts, of all the contestants in the shootout. That does not mean there were any perfect entries, or flawless products.  Pretty much every decision you make as a loudspeaker designer requires a compromise.  The reality is, some folks are better at making choices and compromises than others, and I am hopeful that the consensus of opinion of our readers will be that this reviewer has done his best to be fair and even handed with all entrants.  There were things I liked and disliked about all the subwoofers.  Those shall all be disclosed in the individual reviews that follow.

Is This Test Fair?

We can expect the participants who yield the best results (loudest outputs within the distortion ranges allowed) to say yes, very much so.  Those entrants at the bottom of the maximum undistorted output table may say no. My opinion is not really, and here is why.  The boxes are of different sizes and different prices.  The companies will follow their own ideas and formula's for product creation, and some were clearly better equipped from the standpoint of resources and know-how than others.  On the flip side, it's very difficult to find competitive products of exact box size and retail price, but we did our best to collect similar priced samples from willing participants. Still, the main limitation beyond amplifier power for system output is actually box size and tuning frequency (the lower the tuning frequency, the less efficient the subwoofer is, holding box size a constant).  Since this is NOT controlled, the larger boxes have a considerable advantage over the smaller sized boxes.  The advantage of the smaller size box is clearly in room placement location and wife-acceptance-factor.  (Universally known and hereinafter referred to as WAF among speaker builders).  Keep in mind Internet buyers tend to be less concerned about box size and more concerned about product performance, hence why many of the Internet direct brands have the larger box sizes compared to their brick and mortar competition.

 FAMILY PHOTO_s.jpg

Pictured (left to right): SVS PB12 Plus, HSU VTF-15H, Funkywaves 12.x, Rythmik 15VHP

CEA 2010 Subwoofer Testing - What Is This and Why We Use It?

For many years, a traditional means of quantifiably measuring distortion has involved the very simple principle that if you excite a device under test with a single frequency, any other frequencies which it simultaneously produces must therefore be distortion.  As a result of measuring this repeatedly, on all different kinds of gear we find that our reproduction devices tend to add multiples of the excitation frequency, called simply enough, harmonic distortion. (If you excite a speaker with a 1000 Hz signal, and it simultaneously produces 2000 and 3000 Hz, it has created a 2nd and 3rd harmonic of the fundamental frequency, or simple harmonic distortion.   It has been know for quite some time by those attempting to relate the simply derived number which measures only the amplitude of those harmonics relative to the fundamental, known as THD or total harmonic distortion,  correlates quite poorly with the human perception of how badly the original signal is distorted. The 2010 CEA standard addresses this issue by using a progressively more stringent limitation on the allowable distortion.  Higher-order and/or odd-order harmonics have progressively lower allowable distortion limits, as these tend to subjectively be more offensive to the human ear than lower order and/or even-order harmonics. I have personally seen, as far back as the early 1990's from my own research as a subwoofer system designer for Miller & Kreisel Sound, that we often could "tweak" a compressor in such a way where we found the result more musical and pleasing, yet the THD as measured by some very expensive and reliable HP equipment would actually go up as a percentage of the output.  In my own personal experience, this was almost always a trade-off for more low harmonics (notably second or third) for less higher harmonics (fourth or higher).  We shall discuss this relatively new CEA 2010 standard in some detail, and hold true to it where feasible.

 

Confused about what AV Gear to buy or how to set it up? Join our Exclusive Audioholics E-Book Membership Program!

Recent Forum Posts:

KEW posts on February 17, 2011 14:41
Paul_Apollonio, post: 792889
(Just like my puppy!) LOL

What the heck is that thing? (aside from creepy!)
Paul_Apollonio posts on February 17, 2011 14:30
pbc, post: 792921
Also, would it be possible to post what the sweep levels were that correspond to each of the colors on the graphs?


The sweep levels I used varied from one sub to the other, as there was no standard output power for any given voltage input. (The input sensitivities are not standardized to volume knob position). What I did was this; I started at a low level where there was no question the sub was linear, and drove it up by 2db per curve (input voltage step) until the compression effects became visible to show that frequency response is a dynamic and not a static phenomena. When I first ran the HSU Sub, I had the volume knob set to maximum. It had so very much voltage gain that this caused the problem of having to use really LOW voltages on the input, so much so, I stopped, turned the gain to 12 noon (straight up) and reran the test. (ALL HSU CURVES ARE RUN ON CLIO WITH VOLUME GAIN SET TO NOON) Since the amp voltage gains, input sensitivity, and input sections differ from one sub to the next, standardizing the voltage input used in this test is not meaningful. MOST of the time, the red curve is 0.2 Vrms input. I have the ability with Clio to save 9 curves at one time, and display 10 (last one taken). Since the sweep is 14 second long, the power at the top curves is maxed out. What the power REALLY IS cannot be known without taking the system APART and measuring both the impedance of the woofer and the voltage at the terminals. (Which often results in the product being chipped or scratched meaning the vendors are getting back B stock, and no one wants that, especially me!) Since the mike is quite close to the box, and since some systems (Like the HSU if you look carefully) limit the input voltage at the highest frequencies, each system has been taxed a different amount of time before the power supply runs down to its final level of output. Still 14 seconds is a long time to pull maximum power, so below 100 Hz, this curve shows you what kind of frequency response to expect when you drive the product to the limits, clipping it frequently. As for getting a reference SPL, it would not be a fair contest at a mere 1 meter distance, since that number will be higher for smaller boxes than larger boxes when compared to a much great distance, as the smaller system will follow the inverse square law rule more closely than a really big box (like the Hsu) will. Another really good reason why that data was not collected is frankly, a swept sine signal is invariant in its demands on the subwoofer. We can collect that data, but for a power amp designed like the “ICE”, it will be a lousy indicator of what kind of SPL's you would enjoy with music. (Unless you play it like a DJ not an audiophile). Subwoofer bandwidth signals have a VERY high crest factor, so the CEA test is a FAR BETTER determinant on what kind of peaks you can create than is the steady state test. Adding an additional set of numbers for the consumers may have been simply adding confusion to the mix. Even CEA suggests taking those 1/3rd octave numbers, and lumping them together into bigger groups, under the assumption that the 1/3rd octave numbers (what WE presented) is already too much information for the consumer to digest. Frankly despite the length of this reply, I am just scraping the surface here, there is much more to be said on this subject. Maybe later when GENE stops bugging me by SKYPE….. I hope that shed SOME light. - Mr Paul
MinusTheBear posts on February 17, 2011 13:38
BRING ON THE FUNK!
gene posts on February 17, 2011 12:09
E.g., Each sweep was at an increasing level so that one could gauge at what levels compression started and at what frequency? I.e., in the above graph one could see that the sub started to compress when a 105db sweep was run compared to the 100db curve?

Yes but Paul is extremely anal about accuracy. I personally show SPL levels for continuous sweep tests but Paul's argument is that actual SPL data may not be 100% accurate as it may not reflect losses from power supply sag, driver thermal compression and other issues. It's quite a complex topic to comprehend and I'd hate to put words into Paul's mouth. Perhaps down the road he can write up an article about it.

The max SPL on continuous reverse sine sweeps really doesn't accurately represent real-world output capability, which is the whole reason CEA-2010 was developed. But the data could nevertheless be useful from an academic standpoint. I personally publish it and compare all the subs I test like I did with the Emotiva sub.

The reason why I rated the Emo sub a 4.5 in performance wasn't b/c of its extension capabilities but b/c it was able to play at MAX SPL under extreme stress and the woofer never complained. Yes its extension is quite limited, but its also a very small sub and very conservatively designed. You can't break it.

Continuous tests are really useful in separating the men from the boys in subwoofers IMO.
pbc posts on February 17, 2011 11:41
gene, post: 793062
The SPL calibration was performed for a different set of hardware and NOT for the CLIO. We post SPL data per CEA only for these subwoofer review series and and use freq sweeps to show product linearity under continuous testing. We stand by the calibrated SPL PEAK numbers from the Don Keele/Igor ro/Soundcard/mike Preamp setup.

If you want to extrapolate RMS data from CEA #'s subtract 3dB. If you want to relate it to in-room SPL add between 6-18dB depending on subwoofer location, frequency and room gain factors.

These SPL #'s are short term per the burst tests and don't take into account heating effects of the driver voice coil or power supply sag in the amp section. Heating effects during sustained output can account for addition compression of up to 6-10dB some of which can be seen in the CLIO curves.

Sorry Gene, not following possibly as I'm not familiar with the CLIO curves.

Are the sweeps in the above graph not something similar to what Illka was doing here …



E.g., Each sweep was at an increasing level so that one could gauge at what levels compression started and at what frequency? I.e., in the above graph one could see that the sub started to compress when a 105db sweep was run compared to the 100db curve?
Post Reply