Suggestions for muscle car sound muffler without drone

Robj said

Here's where my Dart is at now. Looks to be about the same as yours at 125Hz. Any chance of sharing your pipe length as it worked so well for you?

View attachment 1714713039

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If you go here
http://www.diracdelta.co.uk/science/source/q/u/quarter%20wave%20tube/source.html#.U0sfFVpOVaQ and use a 27" long 1.5" dia pipe connected to a 2" dia pipe you will get 125hz. You have to convert to meters for dimensions. You will get the following. Vertical axis is DB. Looks like I cut it off when I did the capture.