There’s a pair of L7 and L150 (not the A model) for sale locally at about the same price point and condition (good).
I mostly listen to loud rock and electronic music.
I’d love to get your opinions on which would be the better speaker.
the only two that are in consideration at this point are the L7 and L150. I’m looking for something that will take the L166 sound to the next level in the JBL catalog.
I think you're dealing with a pros and cons situation mixed with lots of potential subjective preferences. Maybe I can give you at least a bit to work with in helping you make your decision.
Let's start with the L166, since that's where you're coming from. It comes with the 066 tweeter which was one of JBL's earlier dome tweeters as they moved away from paper-cone tweeters in the late 70's. The 066 is well regarded for it's ability to extend well into the very high frequencies, but on the flip-side, it's a very fragile tweeter with very low power-handling. In fact, in order to protect the fragile 066 tweeter, the crossover between the mid-range and tweeter in the L166 is set all the way up at 6000Hz, offloading as much of the lower treble as they could get away with (too much IMO) onto the LE5 midrange driver to reduce the burden on the tweeter.
To elaborate on this a bit, the L166 uses the LE5-8 midrange, while the L150 uses the LE5-10 midrange. These two LE5 midrange drivers are actually functionally identical and fully interchangeable, differing only by the color of the faceplate (black vs silver). But while the L166 runs the LE5-8 all the way up to 6000Hz, the L150 only runs the LE5-10 up to 4000Hz. This is significant for two reasons. One is that the LE5 drivers have a rising response (output increases as frequency rises). The other is that when a driver is tasked with producing frequencies far above it's ideal range, they begin to become directional, mainly projecting sound forward. That can create a situation like with the L100 (where the woofer is run full-range) where it sounds fine when you are standing right in front of it, but when you move to the side, certain frequencies begin to drop out. So for both of those reasons, it's really iffy to have that 6000Hz crossover. It's clearly something that was done as an acoustic compromise in order to protect that 066 tweeter.
The LE5-8 midrange itself is a competent, good-sounding midrange driver that gets the job done, with the only questionable aspect about it, in the L166, being that very high crossover frequency.
The 122A woofer in the L166 is a fine woofer, but limited in it's maximum potential power-handling by it's Alnico magnet, which can suffer partial demagnetization events when overpowered, which are cumulative and permanent. The only way to fix this would be to have the magnet recharged at a facility. Newer ferrite magnets do not have this issue.
The L150. I'm personally a big fan of the L150. It's the speaker that got me into JBL, and subjectively my favorite pair. The L150 should not be a massive departure from the sound that you have come to enjoy from your L166, but it should be an improvement.
The 033 tweeter in the L150 has more power-handling than the 066, at the expense of a
tiny bit of high-end frequency response. The frequency where it rolls off is still high enough that you likely won't miss anything, and the increased power handling avoids the need for an obnoxiously high crossover frequency with the midrange driver, allowing each driver to focus on doing what it does best. The 033 is a very easy tweeter to listen to without sounding veiled like some older paper-cone tweeters can. The 066 and 033 are still more similar to each other than they are different so this will not likely be a massive departure from what you are used to with the L166.
The LE5-10 midrange driver in the L150, again, is functionally identical to the LE5-8 in your L166, so you should expect the midrange to be very similar. I do believe that the LE5-10/033 is a better combo than the LE5-8/066, but mainly due to the better crossover frequency used between the LE5 and 033.
The 128H woofer in the L150 is the real star of the show IMO. It's a direct improvement over the 122A, being very similar but utilizing a ferrite magnet and offering increased power-handling. While the 128H was used in many vintage JBL designs, most of them were bookshelf designs like the L112, 120ti, 4412, etc. While all of those are fantastic speakers, the L150 with it's increased cabinet volume and passive radiator really takes it to the next level IMO.
The PR300 Passive Radiator in the L150 performs the same function as a port does in a ported speaker. However, passive radiator has several advantages over a ported design. One advantage is that you completely eliminate any port-noise or "port chuffing" during heavy bass. Another advantage is that a passive radiator offers tuning options that would be impractical with a port. Certain tuning frequencies might only be possible with a port tube that was 10 feet long for example, which would not be practical, but you could replicate that using a passive radiator instead. Yet another advantage is that the tuning frequency of the passive radiator can actually be changed to suit your preferences. This is done by adding or removing weight from the rear of the passive radiator, and has the same effect as lengthening or shortening a port tube would have. Less weight results in more of a mid-bass hump. More weight results in less mid-bass but more low-end extension.
The L150 is tuned to offer fantastic low-end response, having a low-end bass hump and not even
starting to roll-off until below ~45Hz or so. In addition, the passive radiator imparts a certain "texture" to the bass that I personally love quite a bit, but of course that is subjective.
The L7. The L7 is a beast of a speaker, and from a purely objective technical perspective is the best choice. The 4-way design with appropriate crossover frequencies ensures that each driver gets to focus on what it does best.
The 035TiA tweeter in the L7 is a fairly legendary JBL tweeter that has been used in countless models that sold for nearly two decades. It's a great sounding tweeter, but it can be slightly harsh/metallic sounding especially compared to older dome tweeters like the 066 or 033. This issue is easily exacerbated by a known foam plug issue with these tweeters where the foam underneath the titanium tweeter dome, which is meant to dampen the dome, disintegrates over time and no longer properly dampens the dome anymore. Fixing this is a very delicate repair.
The 704G midrange is underrated IMO, and I would say at least as good as any LE5. It's a very good sounding midrange driver.
The 708G-1 midbass driver is a great midbass driver. 8" is a great size for a midbass driver, and this driver is the same driver that is used as the low-frequency woofer in the L5. It's a very robust woofer with good punch.
The LE120H-1 woofer is competent woofer. Not nearly as common as the 128H, especially in the USA. I've unfortunately never had the chance to put this woofer through it's paces but I can't imagine it holding anything back.
Overall, it would be hard not to recommend going with the L7. If you're looking for something that is a clear technological leap over the L166, the L7 certainly qualifies. I wouldn't automatically discount the L150 though. As someone who is also into loud rock and electronic music, bass is hugely important. The L7 will almost certainly have more midbass punch due to the dedicated midbass driver, but the amazing texture of the fantastic deep bass offered by the 128H and passive radiator combo in the L150 can't be overstated. The 035TiA tweeter is technically a better tweeter but as someone who listens to a 033 and an 035Ti (L100T) side by side nearly every day, you're not missing anything critical by going with the 033, and in fact I actually prefer the 033. The 033 also doesn't have the deteriorating foam under the dome issue to worry about. The L150 probably has more collector value, as the L-series (such as the L7) has always fallen under the radar, and the black painted cabinets don't have the same appeal of the oiled-walnut cabinets of the L150. Another thing to consider is positioning. The L7 has a rear port and side woofers that need some space. The L150 is more forgiving if you have to have it up against a rear wall, since it has no port.
Really, neither would be a bad choice. I would get as much info about both as possible. If one of them has a critical flaw, such as damage, or a driver that has been swapped out with a non-JBL replacement, then that would be hugely important to know and would probably be a good indicator of which direction to proceed.
