160Hz bump

[Diggar]

Hi I am not sure if this is the right place for my question but if not maybe you can lead me in the right direction.

I built a front ported cabinet for a 10" guitar speaker. I have a small spectrum analyzer that I use and I noticed that when I put pink noise through the amp there is a bump above all the other frequencies at 160Hz.

Is this the cabinet resonance due to the porting or is this something else?
Any help appreciated.
Thanks

[Chuck H]

out on a limb, I'd say it's interaction between the resonant peak of the cabinet (perhaps due to porting) AND the speaker. The speaker properties need to be taken into account for a tuned cabinet otherwise you can get "wolf" notes (or a bump at 160hZ)

If your using a cab CAD program it should allow for speaker properties in the design process. If not then I'd say try a different speaker or experiment with partial blocking or enlarging of the port or both.

It's also worth noting that there could be imperfections is the amplifier used to generate your pink noise.

It's also worth noting that if this is to be an instrument cabinet a perfectly flat response may not be as good as a bump at 160hZ for the cabs intended purpose depending on the instrument and the room. How does it sound???

It's also, also worth noting that even tuned cabinets often present some minor non linearities. It's not a perfect world and design parameters can often present compromises. If your bump is less than two dB it's probably not worth chasing.

Disclaimer: Not a cabinet designer but I've made these observations before.

Chuck

[Diggar]

Hi Chuck:

Thank for the info and what you write does sound logical. I am going to do some experimenting today.

I apologize for leaving out that the 160Hz is about 10dB so it does have some significance.

I will try different speaker and changing the port size and see what happens.