How to evaluate a subwoofer? Here is my tutorial. - AVS Forum
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post #1 of 6 Old 02-06-2014, 07:33 AM - Thread Starter
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Hello forum users.

Given that I currently some discussion for some months and user questions seeking advice, to interpret measurements and so to choose the right subwoofer for your room here I leave my brief explanation. In the best way possible and with all my knowledge to date. Hope you like it.

I want to add that my language is Spanish, errors may exist in the translation when reading. I beg for your patience.

This topic will get a tutorial to evaluate based on objective data, choosing appropriate our Subwoofer.

There are a lot of factors when taking into account buying a Subwoofer:
  1. budget available
  2. Sound equipment with which it will combine
  3. Objectives to be met by the subwoofer: required maximum sound level, maximum depth desired bass, precision, maximum allowable distortion ...
  4. Subwoofer Size
  5. Type of building
  6. Room size
  7. Optical Design and Subwoofer
  8. Services Seller / Manufacturer:
  9. Sales in local or internet
  10. Pre-service and post-sales support
  11. Warranty ..

These questions must be clearly answered before you begin your search in order to limit the selection and not waste time with models that do not correspond to their own needs . Each will give a different weight to these factors , having people who have no limitation on budget matters much but the color and design of the subwoofer, and others who want to get the best sound possible at the lowest price, but do not have problems in accommodating a big black box in his room .

The audio system is also important, because you have to take balanced decisions . Not worth buying a mastodon 2000 Euros to combine it with a 5.1 200 Euros , but it makes no sense to spend 200 Euros on a subwoofer and speakers combined with 2000 Euros.

The last point , I just add , can be decisive. Some prefer to see, touch and hear before buying , others generally prefer to save and use direct purchase online . The after-sales service is important : What happens if I have a problem or need help installing the equipment? The warranty is too, especially how to solve a warranty and not just the length of it.

How to invest money
The price of a subwoofer will basically invested in the following:

a. Maximum sound level
b . Maximum depth of serious
c . Response time
d . Accuracy and fidelity to the signal ( low distortion , flat response ... )
e . Extras ( such as equalizer settings , automatic measurement, etc. . )
f . Size (the smaller , more expensive - to equal other features )
g . Design and optical ( piano lacquer finishes or woods, so unusual and unique , etc. . )

Each buyer will be more interested in certain aspects than others, and will give more or less weight to each item on the list .

In general , a large subwoofer , heavy, "bass reflex " membrane 12 "or more extensive tour with a powerful amplifier and ensure the best ratio between price and sonic performance , but this is not what everyone is looking for

Graphical Interpretation

I take this as an example

http://www.audioholics.com/subwoofer-reviews/svs-pb13/pb13-measurements
http://www.data-bass.com/systems

For one reason:

Their results are generally recognized as very good, so well served by example



What is important in the first graph is that the curve is as flat as flat as possible and get as far to the left as possible. The horizontal axis shows frequency and the vertical axis shows the level for each frequency sound. If the curve is flat, meaning that the subwoofer does not exaggerate any frequency. We often say that the curve is "flat" if the differences are within a horizontal band of 6 dB.



The second chart shows the maximum output. The subwoofer is better the higher the level in dB without distortion curve (retaining the lower shaped curves as possible). If we distort the curve, we say there is "compression".





The third graph shows the distortion I speak more explicitly above. The flatter the curve, the less compression at certain frequencies.
All subwoofers compressed at some point, it is to do so at the highest possible sound level (dB, decibels).





The fourth graph shows how distorted the subwoofer to increase more and more the noise level (or sound pressure). The red curve is the highest noise level, and also has the largest distortion. A distortion of less than 10% above 20 Hz is a very good result. The lower curves are, the better the subwoofer. The distortion implies that the reproduced sound does not exactly match the original. In very low bass, more distortion is tolerable because it is not audible.



The graph is more complex. If the number H of low are above the high number H, is less audible distortion.




The graph shows the highest noise level achieved with the subwoofer (Take the blue reference). The lower the frequency, the more difficult it is to reach high levels. And we all want to achieve the highest possible levels.




The graph shows the group delay. The blue line is a reference, and black is the measure. If black is above the blue, the subwoofer will sound very delayed. The lower black, best line (the subwoofer will not sound delayed). The red line represents the maximum allowable limit (1.5 cycles) below this will not be audible.



The graph shows the spectral decay, that is, how fast it responds subwoofer. I have not even clear as to explain its functioning. Someone can help me??



Finally, this graph represents how fast you can answer a subwoofer and the time it takes to recover a certain bass signal. I have not entirely clear and doubts assail me here too.

Equalization
Finally , equalization is a very important issue in a subwoofer, because enclose the subwoofer in a room, its frequency response automatically cease to be flat and nice because calls " resonance " that cause unwanted peaks. These peaks depend on the position of the subwoofer in the room, and the size and geometry of it. So it is always advisable to measure the frequency response and first find the optimum position of the subwoofer and then apply low to obtain a "flat " variations and "soft" response equalization. There are devices that automatically measure the correct answer and the same in real time. The best known and in different price ranges are the Velodyne SMS -1 ( obsolete ), the SVS AS- EQ1(obsolete) and Antimode DSpeaker 8033 . AV (AVR ) receivers usually come with an automatic measurement also includes subwoofer equalization . Yamaha has its own system (YPAO ) and Pioneer also ( MACC ) . Others, like Onkyo and Denon, include Audyssey system . The important thing here is to check that the automatic system includes equalized subwoofer , as the most basic models , at least for now , do not include it . Eye , as I understand , the Pioneer MACC nor included.
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post #2 of 6 Old 02-06-2014, 08:52 AM
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Quote:
a. Maximum sound level
b . Maximum depth of serious
c . Response time
d . Accuracy and fidelity to the signal ( low distortion , flat response ... )
e . Extras ( such as equalizer settings , automatic measurement, etc. . )
f . Size (the smaller , more expensive - to equal other features )
g . Design and optical ( piano lacquer finishes or woods, so unusual and unique , etc. . )

Superman is a myth and so is a sub with all these traits in one box wink.gif

History is written by those who have hanged heroes ...

The best EQ is no EQ ...

Alpine SWR-1223D Slot Ported HT Sub

Dual Dayton RSS390HO-4 Reference 15 Build For HT

Main System: Klipsch RF-82 II, Klipsch RC-62 II, RS-52 II, Onkyo 5010, Rythmik FV15HP, PSB S300
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post #3 of 6 Old 02-06-2014, 10:37 AM - Thread Starter
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Quote:
Originally Posted by braveheart123 View Post

Superman is a myth and so is a sub with all these traits in one box wink.gif

Right.
Well, nice, cheap, small, much SPL ... lol
The perfect subwoofer does not exist... biggrin.gif

Anyway, the SVS is an example, not a reference.
I took it just to explain graphs, as could have taken other graphic of any other model.

smile.gif
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post #4 of 6 Old 02-07-2014, 02:11 AM
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Good read Lect.. I gotta say over the years I’ve changed in how I evaluate a sub and in how I relate to the different aspects of a sub. The biggest thing that comes to mind is although a dB racer for the $$ has it’s place, (always will) it’s definitely not my top consideration anymore and some of your posted examples reflect that.

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post #5 of 6 Old 02-07-2014, 05:32 AM
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Quote:
Originally Posted by braveheart123 View Post

Superman is a myth and so is a sub with all these traits in one box wink.gif

My IB`s disagree wink.gif
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post #6 of 6 Old 02-07-2014, 08:32 AM
 
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Lect, 

 

I'm sure you put a lot into this, so I hope you don't lose your grits when I direct you to the Know How tab on the DataBass site which you sited. It explains in easy to understand detail each graph, and how DataBass tested for it. 

 

A few caveats to remember, some of these graphs are IMO 'legacy' metrics, which for most listeners, have now been replaced by easier to interpret measurements. The most notable is distortion. Distortion can best be evaluated in the CEA max burst. The THD graphs can be confusing and require some additional knowledge to interpret. For instance, the SVS sub, which you indicated has an incredibly low distortion in the THD graphs. However, this evaluation is lower than other subs which I know have, in reality, better distortion evaluations than the SVS. How is that possible? well start with reading that tab, and maybe fire up the google machine.

 

Other charts here I wish were more common. Impulse response and waterfall are huge metrics, and don't require much understanding to correctly interpret. 

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