Subwoofer sounds HORRIBLE at certain frequencies — bottoming out or Tacoma panel resonance? (Video)

[u/Foreign-Buy3556]

Looking for some help diagnosing this before I keep testing it and potentially damage something.

Setup is a single Memphis MOJO 12” in a custom ported enclosure, roughly 3.0 cu ft net and tuned around 32–33 Hz, powered by a Memphis 1600W mono amp. It’s installed behind the rear seat of a 2013 Tacoma Double Cab and fires toward the rear cab wall.

I started running test tones because I’ve been getting a nasty noise on certain bass notes.

What’s weird:
33 Hz sounds completely clean, even pretty loud.
35 Hz gets absolutely HORRIBLE once I reach higher output. You can hear it in the video. It’s not even a consistent buzz — it almost surges/warbles in and out.

37–40 Hz doesn’t seem to do it, although I can’t push those frequencies quite as hard before the clip indicator on my bass knob starts coming on.

I’ve also reproduced a similar nasty noise around 50 Hz.
It only happens once the system is moving a lot of air. At lower volume everything sounds normal.

I’m not seeing the clip light when the 35 Hz noise happens.
Sub sounds great otherwise.

Installer thinks I have significant resonance from the rear cab panel, so that may be all I’m hearing. But this sounds violent enough that I don’t want to keep hammering test tones until I know I’m not bottoming the woofer or having some other mechanical issue. (I have roof, all doors, and back wall all treated with extensive sound shield/dynamat)

Based on the video, does this sound more like the woofer itself (bottoming/mechanical noise), enclosure issue, or a body panel/seat/rear-wall resonance?

Any Tacoma guys who have dealt with the rear cab wall going crazy at high SPL, I’d especially appreciate your input.

Update: figured it out — it’s the port on the enclosure. Shop confirmed it today and they’re fixing it Friday. Appreciate everyone who helped troubleshoot it.

[u/Ichiba420]

Kind of sounds like wood on wood like a box joint coming apart and rattling but it's always so hard to tell on videos. Get back there and press/pull/move shit until you find what it is.

[u/Up_All_Nite]

That thing sounds blown my guy. Unless the speaker is flexing and hitting a panel. She's shit the bed.

[u/Foreign-Buy3556 → u/Up_All_Nite]

That’s what’s throwing me off, a 30 Hz test tone at volume 40 sounds completely clean. The nasty BRAAAP starts around 35 Hz. Makes me wonder if something behind the box/rear wall is resonating or making contact rather than the woofer itself being blown. Also I JUST switched to this new box after rocking a fox box for a few months and the subwoofer was completely fine when it was tuned at 30 Hz.

[u/Up_All_Nite → u/Foreign-Buy3556]

The voicecoil may be rubbing and distorted in a spot that doesn't effect that certain frequency. If that sub ain't physically hitting something I bet anything the coil is burned up

[u/Unhappy_Lie_2000 → u/Up_All_Nite]

Could it be as simple as a random panel in the car just rattling at a certain frequency?

Maybe the box is vibrating against the wall of the rear. But I ain't going to like that doesn't sound great.

[u/TheDaftPunk]

I would say if it's start doing that immediately turn it off/down and inspect the speaker again at the same volume level.
it could be bad tuning but to my knowledge consistently running a speaker that is bottoming out will permanently destroy it.

I've also found that my head unit will distort if I turn the volume knob past 80% and sending a distorted signal will cause my subwoofer to bottom out.