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Normal Practice To Use 6 1/2" Sub With 8" Speaker?

I have a PMC TLE1 subwoofer with dual 6 1/2" drivers and speakers with 8" drivers. I am thinking whether it is a norm to combine subwoofers with speakers that have bigger drivers. The PMC subwoofer with smaller drivers goes down flat to 22Hz while the speaker with bigger drivers goes down to 40Hz+/-3dB. I am just curious since my impression is it is more appropriate to use subwoofers with a driver size that is at least similar or larger than the speaker's driver apart from looking at the specifications.

In my case I reckon it is technically acceptable to hook up the sub to the speakers since it does go down lower than the speakers? I just feel a little awkward using a sub that has smaller drivers compared to the main speakers although the results can be good(I think).

Any advice would be appreciated.
ryder
ryder OP
1,734 posts
 
I upgraded from a single 12" Dali sub to dual 6 1/2" PMC sub. The bass quality of the PMC is better and goes lower (22Hz) than the Dali (28Hz) on paper...something which I fail to understand why a single 12" driver fails to go lower than an equivalent 9.12"(2x6.5") driver. The PMC retails at $3,000 while the Dali at $600 though, if that tells anything.
audiokinesis
2,754 posts
 
Ryder, woofer diameter is not a reliable predictor of bass extension. Often designers use large-diameter cones to reproduce very deep bass because a lot of air movement is required, but the cone size itself is not what causes a speaker to have deep bass extension (though along with excursion and enclosure design, it is a factor in how much air a woofer can effectively move). Many factors come into play, with cone diameter contributing to one of those factors directly, and to another indirectly. But the motor, suspension system, and enclosure design all matter more than the cone diameter. Computer programs that accurately model the bass response of loudspeakers do not use cone diameter for anything other than calculating maximum SPL.

By way of analogy, tire diameter is easy to see, but doesn't reliably predict the performance of an automobile. The motor, suspension system, and body/chassis design all matter more.

Duke
dealer/manufacturer
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shadorne
7,477 posts
 
Computer programs that accurately model the bass response of loudspeakers do not use cone diameter for anything other than calculating maximum SPL.

Exactly - that is where large woofers or several large woofers become important. And at low frequencies where hearing is much less sensitive it is generally obligatory to have very large woofer(s) in order to achieve SPL's greater than 100 db at 20Hz with minimal distortion. However, in a good design, with a high quality driver, a 6 inch woofer can do a pretty darn good job down to about 60 Hz - just don't expect miracles that defy the laws of physics. (Anyone with 6 inch woofers on their main speakers must have seen the remarkable excursions that they do when playing bass heavy music and these large excursions means that a fair portion of what you hear is distortion)
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