Building a fourth for my tahoe I ran dats on sealed section no loading wall sealed up.. Well freq was low so I shrunk box down freq didn't change in fact it went a lil lower if anything .. Have any of u experienced this
how low is it
how many subs/size
sealed section size
ive used dats in my 4th
make sure your sealed section has NO air leaks. you must also make sure that the wall is SEALED from rear (b pillar/cpillar no air should escape cabin)
Any leaks will throw sealed resonance off a little. The best way to double check is to pull tsps free air and then use the equation to solve for sealed resonance with those tsps. Also, make sure to calibrate the leads every time you use dats or your readings will be off. Temperature will also effect the readings so if you sweep on a cold day and then change things and its 10° warmer the next time you sweep it will throw things off a bit. Increasing sealed side will lower resonance and shrinking it will raise it, if it is going down while shrinking then you either had a faulty reading to begin with or are currently getting a faulty reading.
You can recalibrated, but I have the resistor here with me lol. Make sure there is no leak the in sealed section. Instead of doing impedance sweep, measure the TS spec. Graph should mirror impedance sweep, but on the right it'll give you some readings. I'm curious what the Q's readings are.
Post up the graph if you can. Leaky or resonant enclosures usually show up as "squigglies" in the impedance, unless there's a really large leak which might change resonance. Also please post specs for the subs if possible.
As a sanity check on the DATS, run another sweep and hold your hand against the cone(s). You should get a funky reading with a much higher amplitude impedance peak (or probably several peaks).
It could also be that the measurement is correct, and as BKNIGHTS was saying - the acoustic environment around the sub is causing a low fb peak. Try to vary the environment by opening all of the doors and see if anything changes.
Glad to see you still check in from time to time. And thanks for the tip on buying one last year! It gets used a pretty decent amount out in our neck of the woods!
Yes everyone has been blowing up my phone and fb about this. I will leave this hint, on drivers with a lot of mms (moving mass) bigger swings (30%)in volume change will have to be made to see resonances change.
So in general for low fs (higher mms) subs, sealed section will typically be smaller? As an example, (4) 18's in a 10 cube with resonance of 41hz. To see a change in resonance, box will ned to be shrink down to 7cube?
Is there any good way to have proper compression in a larger ratio build and still achieve a higher desired tuning?
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