Originally Posted by mcdizzle
...forgot to mention the sonosub is a DIY, using a polk sub that i've had collecting dust in the garage. it is being ran by a 300w yung plate amp. no boost, crossover is around 40hz, not sure how steep the roll off is. 4 cubic ft, port tuned to 22hz. packed with fiberglass insulation....
...sounds as if the sub has a steep roll off around 35, and 20 is barely audible...
Let's start with that sono-sub... no problem with DIY subs, but occassionally, something gets mixed up.
This shows the contributors to a speakers's LF output. Note that the driver (black line) dives below 30Hz while the port output is rising to a peak at 22Hz. Put a sock (foam plug, Nerf football, diaper, etc.) in the port and see if removing the port contribution changes the sound. I'm betting it won't, and the fix is trivial.
I'm banking on the phrase: "packed with fiberglass insulation." You don't pack a vented box as you damp the box resonance you're tuning for.
- Line the walls, at most, with 1-2" of foam or fiberglass.
- Make sure the port mouth is unobstructed for its diameter in all directions, if possible
- test again with and without a sock in the port.
I'm hoping that the low bass is back. If not...
- the amp's SSF may be too aggressive
- you may be using a driver that's not a good match to your enclosure.
There is a lot of confusion regarding the FR of Yung amps and boost / SSF. The best data I see says -3dB point is 21Hz for unboosted amp, the right choice for your design; you want to protect the driver below resonance:
Let us know what you get!