Evaluating Subwoofers

[hellomate7654]

Hello everybody!

I am still new to caraudio.com, but I have been in the hobby of car audio for awhile now. However I have never really gone above the "entry level" stuff, and I really want to get into the more high performance and high quality stuff.

The thing that EVERYBODY (at least throughmy limited experience //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif ) talks about when comparing/evaluating subwoofers is RMS power. However, I know that there is much more to it than that. What do you guys look for when you are shopping for subwoofers on the internet, like when you can't actually "listen" to the sub before buying it. I know there is sensitivity and efficiency and whatnot, but I am not sure how that relates to its performance. When it comes to subwoofers, I am a moderate SPL guy, but I also like to have excellent quality.

So things do you guys look at in a subs specifications when you are buying?? And also do you guys have any suggestions on brands/specific subwoofers that you think I would be interested in?? (Again I am more of an SPL guy, looking at doing around 1000 to 1500 watts rms)

Thank you for your help!! //content.invisioncic.com/y282845/emoticons/fro.gif.c695f1f814b01c4ad99fe7f8cccadd29.gif

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[JimJ 5,000+ posts]

The thing that EVERYBODY

I don't.

 

[modskwod 10+ year member]

First piece of advice I'm gonna give you: Don't worry about specs too much. Some companies post the wrong specs on their sites and don't particularly care.

What you need to look for is good quality parts. After a while you get a feel for it, but a good indicator of quality is in the small stuff. Stitched surrounds, cast frames (on non-entry level subs, stamped frames is common on entry-level), and cones made from pressed paper or carbon fiber all play a factor.

Another indicator of lower quality subs is a covered up magnet. Not a magnet boot, those are common, but a magnet covered in plastic so you can't see what it really looks like is an indicator of more concern over appearance than quality. *cough*kicker RE rockford fosgate*cough*

I could go on and on about things to look for/ not look for, but if you're looking for good quality subs, I suggest Sundown, Digital Designs, Audioque, DC, Sound Solutions Audio, and Incriminator.

 

[Imtjnotu 5,000+ posts]

look for rms...company history....xmax sometimes....looks....Voice coil size...motor...weight

 

[cam5860 10+ year member]

Just buy image dynamics and forget about the specs. There's only a few brands on the market that are worth buying anyway.

 

[Bumpin' Goalie 10+ year member]

BL and Xmax are good, interesting ones to research. May as well look up them all if ya can though. It'll help in strides as you progress down the car audio road.

Google T/S specs and their meanings (or wikipedia the individual things "qts", "re", etc) and you should grasp a base knowledge.

As far as SPL with excellent quality (referred to commonly as SQL-Sound Quality Level) I am partial to the DC (DC Sound Labs) Level 4 for 1000rms and the Level 4 XL for 1500rms.

There are many others such as Fi BL, and a million more. Alot will come down to your personal preferences, price, and company reputation.

Best of luck.

 

[Kyle_Keating 10+ year member]

BL over displacement is important - that is only shown as a curve

Compliance over displacement is also important - show an a curve

inductance can be important - this can also be shown as a curve but its a high order derivative so its non linear effects do not directly affect the system as greatly as say compliance or BL which are direct forces on the system.

Other motor distortions such as flux modulation or unwanted eddy currents- non-conductive formers, shorting rings, motor saturation etc can deal with these

sensitivity is a big one let me repeat: BIG ONE, but you also need to consider sensitivity over the displacement which is basically xmax (give or take)

BL gives you sensitivity and resistance (or the DC resistance ace of the voice coil ) will reduce your sensitivity which is why the formula is BL^2/Re for pure motor force factor spec'ed in Newtons squared per Joule per Second, or watt. Combine that with the moving mass and cone area and you define raw SPL.

RMS is not a woofer spec its an amp spec. LOTS of brands will hype up "cooling" or high RMS - i have yet to see any conclusive results of any of it. If it helps its only going to help for very long term thermal abilities. Any and all woofers will takes tons of power short term. Which is why some brands spec SPL woofers at say 20,000 watts which for a 1 second burp is actually not impressive from a thermal standpoint, especially at a high frequency where the mechanical displacement limits wont be reached. The issues with say 20,000 watts (for example) is that the accelerations are very extreme but we don't see thermal break down over a short period of time, but you'll often see mechanical break down from high force - broken cones are very common.

The last specs are the hidden specs - durability, longevity. etc - is it generally going to last for the time i expect it to last? One major one for example is foam vs rubber surround. Foam may give you say ~1.5dB Extra SPL but it not UV or water proof and can wear away over the years. Point is here they are always trade offs to consider.

I also believe "SQL" simply stands for sound quality + loud? where SQ is stickily "Sound quality" and "SPL" is for spl woofers.

I actually think those terms are rather idiotic and misleading. In fact a good woofer can indeed be loud and sound very good. Many of this things that make a woofer sound bad also make it less loud.

 

[ciaonzo 5,000+ posts]

Good stuff, Kyle. Thanks for taking the time to write all that.

 

[audioholic 5,000+ posts]

Over all I agree Kyle's post was very good, a couple issues to mention though...

Sensitivity is important, but not a good spec to look at or compare for subwoofers. Sensitivity is measured at 1khz, who plays their sub that high? Its also not important to know your sub's sensitivity unless you are thoroughly knowledgeable on how hoffman's iron law affects speaker sensitivity versus LFE and enclosure size. In other words, many times LOW sensitivity is desirable, most people wouldn't understand that unless they understand H.I.L.

SQ, SPL and SQL are reasonable terms to use imo. Not all factors that make a woofer louder also make it sound better. Plenty of SPL oriented drivers are designed to have a peaky output, not very good for playing music, but good for trying to belt out one frequency very loudly. Coil size is another example. 4" coils sure increase power handling, an advantage in SPL setups playing at or very near enclosure tuning. But a massive 4" coil does not lend itself to accuracy of signal reproduction in a delicate and complex piece of music.

 

[cam5860 10+ year member]

When I buy a sub I am looking for two things. xmax and cone area. I want the most cone area I can get without the surround taking up space and the most xmax possible. I like good output myself. Image dynamics gives you the best of both worlds. That's why they are my pick. Output in a subwoofer is just like horsepower in a engine. You want to bore a motor out 60 over to get the max piston surface area for more compression. And second you want the longest stroke possible for more horsepower. It's the samething with a subwoofer because they both compress air. Surface area and xmax is all you need to look at if you want output. Sensitivity is no big deal. You just need more power to reach the same output. High number means less power, lower number means more power needed. But it don't effect output long as you got the extra power to push the sub. The only time sensitivity comes into play is on full range speakers. If you are running them off a deck with low power. You want a 93 sensitivity so that they are efficient on low power.

 

[audioholic 5,000+ posts]

When I buy a sub I am looking for two things. xmax and cone area. I want the most cone area I can get without the surround taking up space and the most xmax possible. I like good output myself. Image dynamics gives you the best of both worlds. That's why they are my pick. Output in a subwoofer is just like horsepower in a engine. You want to bore a motor out 60 over to get the max piston surface area for more compression. And second you want the longest stroke possible for more horsepower. It's the samething with a subwoofer because they both compress air. Surface area and xmax is all you need to look at if you want output. Sensitivity is no big deal. You just need more power to reach the same output. High number means less power, lower number means more power needed. But it don't effect output long as you got the extra power to push the sub. The only time sensitivity comes into play is on full range speakers. If you are running them off a deck with low power. You want a 93 sensitivity so that they are efficient on low power.

Your statements would be true if we were only discussing sealed enclosure systems. In vented systems, enclosure sensitivity plays a major role, and greatly diminishes the role of xmax while increasing the importance of power handing. When playing music at or very near enclosure tuning, excursion (xmax) is at its minimum, but enclosure efficiency is maximized. This is why the cone moves the least at tuning, but output is the greatest. Your 'xmax and cone are all that matters' theory ignores this.

Secondly, a speaker cone is similar to an engine's piston. But unlike the engine's piston, a speaker cone is not moved mechanically based on an off-center rotating shaft. A speaker is an electro-mechanical device, so simply looking at the mechanical aspects of it (xmax and cone diameter) and pretending it works just like a piston is only seeing half the over all picture. For example, you say efficiency is not important because you can always just keep increasing amplifier size until you hit full excursion potential. What happens if the coil melts before full excursion is reached? What if someone would rather reach 30mm xmax with 800 watts than it requiring 3500 watts? What if someone doesnt want to have to buy a new alternator, overly large wire, extra batts... just because they took your advice and decided efficiency was 'no big deal'? What if someone ignored efficiency when buying a sub, then realized that thanks to hoffman's iron law, they bought a sub that requires more airspace than their vehicle will allow?

You cant just look at xmax and cone area when buying a sub. That leaves way too many variables to chance.

My advice is to stick around these forums for a while and learn as much about speaker specs as possible. Read up on what theil/small specs are and how they affect speaker performance. No one speaker spec is the most important, and every one of them works in correlation with or are dependent on other specs.

 

[ciaonzo 5,000+ posts]

The only things that matter are the logo and the size of the magnets. You should be safe once you get over the 70 pound mark.

 

[cam5860 10+ year member]

when I was in the market to buy my 8 inch subs. I was looking at the new solobarics the W3's and the ID8's. What sold me was cone area and xmax. ID has the most cone area because image dynamics uses the high roll surround to keep from taking away from cone area. Second the W3 only had 10 mm of xmax which is about average for 8 inch subs. The solobarics have around 12 mm of xmax which is decent for 8's. But the ID's have 15 mm of xmax which is excellent for a 8 inch sub in this price range. So image dynamics was a no brainer for me. Power handling don't mean sh!t if a speaker can't move alot of air without being overdriven. It's just going to rip the spider out of the speaker or tear the surround off of it from over excursion. All the subs I have ever blowed had sorry azz xmax 8 or 9mm of xmax. So easy to blow up from over excursion.

 

[audioholic 5,000+ posts]

when I was in the market to buy my 8 inch subs. I was looking at the new solobarics the W3's and the ID8's. What sold me was cone area and xmax. ID has the most cone area because image dynamics uses the high roll surround to keep from taking away from cone area. Second the W3 only had 10 mm of xmax which is about average for 8 inch subs. The solobarics have around 12 mm of xmax which is decent for 8's. But the ID's have 15 mm of xmax which is excellent for a 8 inch sub in this price range. So image dynamics was a no brainer for me. Power handling don't mean sh!t if a speaker can't move alot of air without being overdriven. It's just going to rip the spider out of the speaker or tear the surround off of it from over excursion. All the subs I have ever blowed had sorry azz xmax 8 or 9mm of xmax. So easy to blow up from over excursion.

Ive already stated why xmax is not a huge factor in vented systems, and why power handling becomes more important. Spiders ripping is a mechanical failure, which takes enclosure size into account as a variable, and was/is not the topic of our discussion on thermal limits. xmax plays a role in performance, and should be considered, even in vented systems. But it and cone area are not the end all be all specs you claim they are.

 

[cam5860 10+ year member]

Audioholic I only use sealed enclosures. I know vented enclosures is all about the frequency response and tuning. But in a sealed enclosure xmax and power handling is everything.