Sealing up the ports on a 4560.

[Izzy Weird]

I have used many JBL 4560 cabinets in nightclubs, and I would generally cross them over into 18” vented box subs mounted around the dance floor. Typically the crossover frequency would be 100-120 Hz.

I have always liked the way front-loaded horns reproduce the impact of drums, explosions and other low-mid frequency percussive events. I have read another thread here about the impact of 4560 horns, and I completely agree.

But one thing that always gave me difficulty tuning such a system was the resulting phase turnover due to the porting of these low-mid units. A phase turnover near to a crossover frequency is something I would really like to avoid.

I currently use a pair of EAW (ported) front-loaded horns with 15” JBL drivers (wish I could remember the model number). I have a pair of 4560 cabinets, and I have had cabinet shop prepare plates to cover up the ports. I plan to use bolts, tee-nuts, and adhesive foam to secure and seal the port covers. My intuitive sense tells me to stuff these cabinets with fiberglass.

Has anyone else experienced crossover difficulties with similar front-loaded horn/vented-box cabinets and subwoofer systems? Has anyone experimented with sealing up the ports on similar horns to make them integrate better with subs?

Thanks in advance,
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Izzy