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SPL vs. SQ Subwoofers - what separates the two?

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Fairly nooby to car audio, and I searched the forum but couldn't find anything on this.

What differentiates a SPL sub, to a SQ Sub? Meaning - what makes a sub one or the other? OR a hybrid?

I currently have a beginner audio system in my trunk car and am told my Alpine Type S is an SQ sub. Judging by the size of the motor/cone design I'd tend to agree as it's only rated at 500wrms.

What characteristics should you look for to differentiate the two?

Thanks :)

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This is actually a more complicated question that you might think. The concept of SPL is easy to define and measure, SQ is simple in concept (sound as true to the original as possible), but it's a lot harder to measure and just what a "SQ" system is can be very different to different people.

In my opinion, very few car audio manufacturers make true SQ hardware. Some may make stuff that is closer than others though. The Alpine Type S is definitely NOT a SQ sub. That's not so say it can't sound pretty good, because it can, but producing high fidelity sound is not what its primary design goal was.

As far as what differentiates a SQ sub from a SPL sub, here are several attributes that SQ hardware will have and the SPL hardware has no concern about:

1. Low inductance to resistance ratio (Le/Re)

2. Low distortion

3. Ability to produce the desired frequency range and response (usually flat, but not always) in a reasonably sized enclosure

Here are some examples of true SQ drivers:




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Thanks for the reply Tricticum! You've helped clear things up for me.

What would indicate the primary design goals of a subwoofer like the Type S?

I assume Fs, Ques, Frequency response, driver/motor.

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The primary design goal of the Apline S series is low cost output. The Fs, Qes, etc don't really separate SQ drivers from SPL drivers, Le (inductance) can be an indicator though. The Type S subs have a moderate Le/Re ratio, lower is better.

Distortion and frequency response are going to be the important distinctions. Unfortunately you can't just look at the specs for the sub and know what kind of distortion levels you are going to get. Also the enclosure has a big effect on the amount of distortion produced.

The fact that the S series subs only cost around $100 is also a good indicator that they are not really SQ focused. Its not that price alone is an indicator, but high quality SQ subs are expensive to build and that is reflected in the cost. Don't interpret this as a dig against those subs though, I really like the S series and I think they are one of the best subs you can get in that price range.

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Thanks again for the detailed response Triticum! Definitely taught me something. I assume the only way to truly know is to hear the stuff in person unless it's extremely obvious in the specs.

+5 star rating.

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