Template talk:L1® Classic, Model I, and Model II Acoustical Output

From Bose Portable PA Encyclopedia FAQ & Wiki
Jump to: navigation, search

quote:
Originally posted by Neil-at-Bose:

Some of you that have read through the product specifications for the L1® classic and L1® model I system
may have wondered how the systems are able to achieve the same acoustical output given the differences in the power amplifier configuration. We wanted to provide you with further explanation on how this is indeed possible.

The model I system features one dedicated 250 watt RMS amplifier that powers the Cylindrical Radiator® loudspeaker and an additional 250 watt RMS amplifier that powers up to two B1 Bass Modules. This brings the total system power handling to 5oo watts.

In contrast the L1® classic had two 250 watt RMS amplifiers each dedicated to driving one half of the Cylindrical Radiator® loudspeaker and an additional 250 watt amp that powered up to two B1 Bass Modules. The total system power handling is listed at 750 watts.

Although these numbers serve as a point of reference they do not tell the whole story. During the design of the L1® model I the impedance of the L1 Line array was lowered. As a result of the lower impedance, a single 250W amplifier now powers the system to within 1.75 dB of the max SPL of the L1® classic. We paid particular attention to this change and conducted many A/B comparisons to confirm that there was no significant audible difference between the two systems. When used in the field with program material, the volume difference between the two systems is unnoticeable.

For those that own both an L1® classic and a model I system it is important that the correct Cylindrical Radiator® loudspeakers are matched to their respective power stands. For example if you inserted a model I radiator into an L1® classic power stand you would notice a (-6dB)difference in acoustical output. Both the L1® model I power stand and radiators contain an orange sticker which serve as a easy identifier. If you are purchasing an open box system this is something to keep in mind.
I hope that you found this information helpful.

Neil


The difference between 500 Watts and 750 Watts is 1.75 dB. This is barely audible, if we did nothing to improve the efficiency. But we did! We made up the difference through tweaking the impedance of the driver and a few other subtle adjustments in the power amps.
I was probably the most rigorous in making the engineering team prove to me that we were at parity with the Classic -- that any differences were negligible. I was completely convinced of this as were others on the team.
I don't know what's going on exactly in the setups you're comparing. But to resolve any difference, you're starting by splitting hairs (1.75 dB) and working to even more subtle differences given the gains we got in efficiency.


Source — Ken-at-Bose


The two amps in the Classic power stand that drive the two sections of the Classic Cylindrical Radiator speaker are capable of delivering 500 Watts, but because of the exact impedance of the speakers, they actually deliver 370 Watts.
In contrast, the single amplifier in the Model I power stand that drives both sections of the Model I Cylindrical Radiator speaker is capable of delivering 250 Watts and delivers the full 250 Watts when needed.
This amounts to a difference of 1.7 dB = 10 * Log (370/250).
(Note that in both the Classic and the Model I a separate 250 Watt amplifier is dedicated to powering one or two B1s.)
I realize that these further details do not resolve the different experiences being reported. I do feel, however, that they may provide some additional clarity to those that are interested in learning more.



Source — Ken-at-Bose