at www.jblproservice.com where many more of their systems detailed tech data is available, lots of xover schematics for instance. Some even have errors, where the same xover is used with 8 ohm HF in one system, and a 16 ohm driver in another, need to be careful about "cloning" from bad drawings. The 4648A-8 system is specified at 97dB/watt using the dual 2226J's. My rat meter calls them 100. JBL say the 4648 using a pair of 2226H's is 100dB/watt, but that is a 4 ohm system impedance. The main point is knowing how many dB's to shelve the HF. In room measurements once all xover losses have acted will let you know how close you have gotten with level matching, in some cases manufacture published data is misleading...my 902's can't be found rated higher than 106dB on a 511 horn in any Altec data. They measure 112dB. Good luck. You HAVE been to the altec heritage online library, right? Sam
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