[LowerFE]

Can someone explain to me what determines the output of sealed subs?


Specifically, I'm looking at the SVS SB12-NSD and the Emotiva X-Ref 12. Ricci's data shows the SB12 having 11dB more output than the X-Ref at 20Hz when the SB12 is a smaller subwoofer with 200W less amplifier power.


DIY section, from what I can gather, suggests cone area and maximum excursion down low for low bass, and also driver sensitivity for upper bass. If I understand correctly, 11dB more means a bit more than 10x more output. Since the cone area is roughly the same, it would mean the SVS's driver would have almost 4x more excursion than the X Ref's, and that's clearly very unlikely.


Since the X Ref has the bigger box and amplifier and similar cone area, what else, besides excursion, determines max SPL at low frequencies?

 

[shadyJ]

In the case of the Emotiva vs the SB12, the Emotiva was hobbled by electric filters. Its deep bass ability was intentionally diminished via signal processing. Only the designers really know the reasons for that decision, but I think many of us here could offer reasonable speculation. 1) to protect the driver from bottoming out and prevent damage. 2) to prevent the mechanical exertion of reaching for the outer edges of the driver's xmax, which will prolong the life of the sub 3) to reduce distorted output, as the driver really loses control by the time it hits 30 Hz with any reasonable output. Comparing distortion sweeps, the SB12 is clearly using a better driver. However, neither subs is really a deep frequency champion, and both become worthless for deep frequencies after the 95 dB sweep. At least with the SB12, you stand a chance of boosted performance from pressure vessel gain if it is in a small room.


By the way, an 11 dB increase is just under four times the output, not 10X more.

 

[Bill Fitzmaurice]



Quote:
Originally Posted by LowerFE  /t/1523702/what-determines-max-spl-in-a-sealed-sub#post_24514248


Can someone explain to me what determines the output of sealed subs?

The combination of sensitivity, frequency response, thermal power capacity and maximum cone displacement.

Quote:
By the way, an 11 dB increase is just under four times the output, not 10X more.

+6dB is four times the power, +10dB is ten times the power. +10dB subjectively sounds twice as loud.

 

[LowerFE]



Quote:
Originally Posted by Bill Fitzmaurice  /t/1523702/what-determines-max-spl-in-a-sealed-sub#post_24515283


The combination of sensitivity, frequency response, thermal power capacity and maximum cone displacement.

The SB12 clearly has a better driver, but it is by no means a high output driver given the rather low cone displacement. In your opinion, how would you explain the large difference between the huge low bass output of the two subwoofers?

 

[Bill Fitzmaurice]



Quote:
Originally Posted by LowerFE  /t/1523702/what-determines-max-spl-in-a-sealed-sub#post_24517427


The SB12 clearly has a better driver, but it is by no means a high output driver given the rather low cone displacement. In your opinion, how would you explain the large difference between the huge low bass output of the two subwoofers?

If I knew the driver T/S parameters and detailed box dimensions I could tell you in about 10 minutes. But without that data I can't. Perhaps shadyJ's explanation is correct, they might have limited the LF output. The logical reason for that would be to cut down on blown driver warranty returns.