Xmax on horn loaded enclosures

[kblackmore]

Gentlemen,

I am considering taking on a project to improve my home system which involves building new bass horns to replace my existing ones. The design is by Dana Moore and the cabinet is called the Jamboree. It is reported that it can go down to 38 Hz when corner loaded. It is a dual 15" cabinet with the woofers mounted on a motor board that has a 13X6 hole cut in it for the sound to leave through and enter the horn. One of the recommended woofers is the B&C 5PZB100. My question is, with 8 mm Xmax on that driver, would I run into issues with the woofer bottoming out on the motor board and if so, what would I need to do to avoid the issue? I do push the system on occasion, and I like that the woofer has both the efficiency and the power handling capability, but I don't want to kill the woofers. Any words of wisdom would be appreciated.

Thanks,
Ken

[wg_ski]

Re: Xmax on horn loaded enclosures

You will run into problems with bottoming the woofer. I did it with Kappa P15LF2's on horns with a similar throat. Cut a gasket out of 1/2" ply, the width of the woofer mounting surface and install it in between. If you still bottom, you'll need 3/4".

[Sydney]

Re: Xmax on horn loaded enclosures

.... My question is, with 8 mm Xmax on that driver, would I run into issues with the woofer bottoming out on the motor board and if so, what would I need to do to avoid the issue?...Any words of wisdom would be appreciated.

A voltage limiter could help.
Consider that the industry definition of Xmax is quantified with a very high distortion figure ( 10% ) - I avoid pushing drivers to that excursion.
Paul Klipsch ( in his papers ) advocating using horns to reduce excursion demands to minimize distortion.
Perhaps this borders on a philosophy of approach and implementation; but it's my w.o.w. that has prevented damage.

[wg_ski]

Re: Xmax on horn loaded enclosures

8mm of excursion (safe for the driver) may very well send the cone beyond the edge of the frame resulting in bottoming. Some of these horns were designed back when anything over 3 mm was a pipe dream, and with longer excursion drivers you need a spacer.

[kblackmore]

Re: Xmax on horn loaded enclosures

Well, the Jamboree is a DIY implementation for the Klipschhorn. I am upgrading my Belle's. Would buying an extra set of gaskets from a woofer reconer give me the clearance needed for the extended Xmax?

Already spoke to the factory about replacement horns for the midrange, keeping my existing drivers. The next bridge to cross is the crossovers of which I am trying to study up as much as possible being since Klipsch is a big fan of autoformers to attenuate the dB level of the mid & HF horns. Might actually go active due to the complexities of the passive crossover.

[wg_ski]

Re: Xmax on horn loaded enclosures

A 'speaker gasket' might provide enough clearance - double thick ought to be at least 8mm. If I used one of those, I'd glue it on because it's not as rigid as a plywood ring and harder to keep in place while installing the driver. Then if it isn't enough it would be harder to rework. I would prefer the driver to have no potential for interference all the way to Xlim - which is probably somewhere around 20mm.