JBL LSR305 & LSR308 measurements
By Etienne Dechamps (e-t172) - etienne@edechamps.fr
Last updated: February 2017
This document attempts to compile all published measurements of the LSR305 and LSR308 active monitor speakers from JBL Professional. What makes these speakers stand out from the crowd (especially at their price range) is the availability of detailed specifications in the form of on-axis and off-axis measurements. These measurements demonstrate very impressive acoustic performance and make these speakers excellent choices according to known, demonstrated, double-blind-tested scientifically established facts regarding objective loudspeaker performance. This document attempts to back up that claim with actual data and objective evidence.
NOTE: this document is about the original version of the JBL LSR305/LSR308. I am not aware of any measurement data for the latest version of these products (JBL 30xP MkII). One would presume that the MkII has similar performance to the original version, but this has not been confirmed. NEW January 2020: The 305P MkII has been measured by amirm from AudioScienceReview using state of the art equipment!
If you come across additional data points that are not included in this document, feel free to comment or send me an e-mail and I'll gladly add it to the list. Note, however, that I will not accept frequency response measurements that were not achieved in anechoic conditions: such measurements can be misleading because they include the contribution of the room the speaker was measured in.
Frequency response measurements
From JBL Professional (Harman)
Sound & Recording (German magazine)
Unfortunately, and quite surprisingly, JBL only published detailed frequency response graphs as part of the marketing package they provide to retailers; these graphs are not available on their website. Worse, the images provided by JBL seem to only exist in very small dimensions, although they are good enough for the curves to be readable. The following images were found through Google Images searches, which surface them from some of the retailers.
Cropped and enhanced:
JBL also seems to have provided another graph:
Cropped and enhanced:
The reason why I believe the LSR308 label to be a mistake is because the low bass extension is consistent with the smaller LSR305, and known measurements of the LSR308 don't show the peculiar rise in the high treble.
Photo comparisons confirm that this is a LSR308, not a LSR305. In addition, the better bass extension shown by the graph is consistent with the larger woofer and enclosure volume.
Cropped and enhanced:
Dr. Earl Geddes (GedLee), one of the foremost experts on loudspeaker directivity (he coined the term "waveguide"), has added the LSR308 as an example dataset in his polar map application:
It is possible to get precise figures by using the application and navigating the various axes. As mentioned in the application notes, the low frequency part of the measurement is not very accurate, which explains why the speaker low-frequency roll-off looks different from the JBL-provided data.
Dr. Geddes himself said, commenting the above measurements:
"That is an amazing speaker. There are of course better speakers, but at $200 I don't think ever I've seen a better speaker."
Source. It appears the measurements were made in May 2014 by a German company called Four Audio. Note that their "EQ graphs" are not included here because they seem to show measurements in some unspecified room (as opposed to anechoic data), making them useless and misleading.
Low frequency cut-off figures can be derived from the JBL-provided graphs:
JBL seems to use the -10dB point on their website, which is too flattering.
According to the JBL website peak SPL is 108dB for LSR305 and 112dB for LSR308, but there is no indication as to how this is measured, making comparisons impossible except between the two speakers. The measurements from S&R, shown above, seem to indicate that these claims are grossly exaggerated, at least for reasonable THD levels.