Using Dayton Apollo 18N Driver In Old Sub Cabinet

[Randy L]

Hello All, I have 2 old Carvin TRx118N subwoofers and I am thinking of swapping out the stock drivers (still working great) with Dayton's new Apollo 18N drivers (PE P/n 295-644).
While I do like to design and build PA speaker cabinets I'd like to simply drop them into the Carvin sub cabinets IF the results will be an improvement over the old Carvin NE18-8 raw drivers (the Carvin NE18-8 looks very similar to the B&C 18NBX100 Neo driver and Carvin did have B&C build their TRX drivers for a while).
My measurements and running numbers through WinISD show the existing cabinets have an internal volume of 4.25cf (after deducting for vent and driver volumes as well as other things using up space inside) with a box tuning frequency of 39.5hz.
Modelling the Apollo 18N driver in WinISD and using the rated 1200 watt RMS rating, I see the driver excursion exceeds XMaxx of 9.1mm from 49-75hz at 1200watts, with the peak excursion of 11.1mm at the critical 60hz.
For my PA use, I use my DBX Driverack PA to filter off the signals below 40hz and that has saved my old Carvin 18" drivers from destruction after all these years.
The Apollo 18N driver reaches its rated 9.1mm Xmaxx at the 60hz peak with a 775 watt input.
I have a 3000 watt amp used for used for subwoofer duty, and since I run 2 18" sub cabs paralleled, each driver would be fed up to 1500 watts.

Wondering if 11.1mm cone excursion at 60hz is safe for the new Apollo 18N. The specs and product description doesn't list Xlim so I don't know how much "buffer" is designed into these drivers.

My original plan was to replace the Carvin subs with the powered EV EKX-18SP (1300 watts peak, but most likely 500 watts RMS) but they are a pretty big punch to my funds at $1400 each. Then, while browsing PE I came across their brand new Apollo 18N and am intrigued by them.

[billfitzmaurice]

I always recommend limiting the amp voltage so that xmax isn't exceeded. That way you don't run the risk of transients or overshoot damaging the driver. Besides, all you get for exceeding xmax is higher THD.

[Chris Roemer]

OTOH, 125dB @ 50Hz SEEMs like it should be adequate? (ouch)

[billfitzmaurice]

In a living room yes. But 125dB at 1 meter is 107dB at 8 meters, so in pro-sound it's not a lot.

[Paul O]

Randy does the software show any gain in SPL with the Appolo driver, if so how much?

[billfitzmaurice]

The 2008 NE18-8 had only 5.4mm xmax, so an additional 5dB is possible, if that's the version he has.

[Randy L]

Paul,
Attached are the graphs showing the differences between the Apollo 18N and the Carvin NE-18N drivers, both in the same TRX118 sub cabinet. The Apollo 18N is the RED curves and the Carvin is the BLUE. Note that the Apollo 18N does have a bump in SPLs at 750watts and at the driver's rated 1200 watts RMS. BUT once again, at the 1200 watts input note that the Apollo has exceeded its Xmaxx and the Carvin driver has 1mm buffer before it reaches its 7mm Xmaxx. Both drivers in the same cabinet have very similar response curves.
Image titles didn't show so here is what each is. Image 1 = the frequency response curves compared. Image 2 = SPL at 750 watts input. Image 3 = SPL at 1200 watts input. Image 4 = cone excursions at 1200 watts input.