Sunn 200S clone

[MisterT]

Hey All,
I just recently built a Sunn 200S cab per Conrad Sundholm plans.
I had 2 older Eminence square back 15's and installed them.
Using my 67' Fender Bassman head the cab sounded good at 3-4.
When I take it up to 5-6 the speakers began to make an awful blapping sound. Contacted Conrad and was told the old speakers will not work in this folded horn 2-15 cab...so he recommended the Eminence CB 15's. I bought 2 new ones and installed them.
Same blapping sound at 5-6 volume. This just sucks!
I went back over the cab plans detail by detail and discovered I had mounted the port boards with the the angled piece to the back of the bottom edges of the speaker baffles. The plans show them mounted just below the baffle edges.
Could this error cause all this bad blapping! I even added more insulation thinking this might increase the internal pressure on the speakers. No improvement!
I can't get it out of my mind that the internal volume is too much and the speakers are becoming unloaded and causing the blapping sound.
Can anyone help or tell me who I might contact?
Sorry to be so wordy!!
Take care and stay low!
MisterT
Oklahoma

[edbass]

Do a search on the Sunn Discussion Page.

There have been more than a couple multiple page threads about 200S and 2000S clone cab projects, including ones built using Conrad Sundholm's plans.
I'm certain that the builders would be happy to share their experiences and any advice they may have.