28 December, 2016

Review: JBL20T 4406

Review: JBL L20T, Part I
JBL 4406 4312A
Letter from NYC (57) 2016 (13)

A friend just gave me his father's pair of JBL L20T. They look remarkably handsome, and I immediately tested them.

Basic Info
The L20T was introduced in 1988 ($235), as the smallest member of the L series (Official Brochure, with spec's). It is the consumer version of the 4406 and uses the exact same drivers (115H woofer and the famous 035Ti titanium tweeter). If you look at the Official 4406 Brochure you shall see the spec's are identical. They are different only in the looks of the enclosure and the port, and the 4406 has a tweeter attenuator. In fact, the L20T is also used in many studio!

I was quite eager to hook them up as I still own two pairs of the 4312A (official literature here and here), which employ the same 035Ti tweeter (I have also heard countless others of the 43 and 44 series). I had a ball with the 4312's (including stacking, see my mammoth article).


  • Build and Cosmetics My pair is in good shape, with a little bleaching from the sun. The L20T is well built. Although the cabinet is made of particle wood, the real wood veneer lends solidity, and they feel sturdy. I find they quite nice to look at, comfortably old fashioned! Note that unlike more modern designs, and like its other JBL contemporaries and pro monitors, the pair are not mirror-imaged - not only the ports, even the drivers are all to one side if you look at the pic. Surely this would bother some audiophiles and speaker designers, but the excellent sound speaks volumes about the engineering prowess of the JBL team (and about many of the so-called "science", "theories", even "facts", of modern speaker design, of which I am highly skeptical).
  • Sound I drove them with various electronics but not yet with a high powered amp. Lepai LP2020A+ Ancillary electronics are more or less that of my Reference System III (see right sidebar; for full article see here). Sound was excellent, more solidly honed than my Dayton B652, but it is apparent these need more power than the B652. Elekit TU-8300 (here) Swapping in the more powerful Elekit immediately freed up the sound more. There is more dynamic headroom, and I played and enjoyed a Bruckner symphony in full. However, I did notice that the brass in the right speaker did not have quite the sheen they should have. I put my ears close to them and discovered that the tweeter was not making sound. I took the tweeter out, disconnected the cables and tested it with a multimeter - surely, the coil is unfortunately open. Linn System Even with one tweeter out the L20T's still were very enjoyable! I put the tweeter back (but left disconnected) and took them into the large living room (>300 ft), where I connected them to the Linn Majik (here) integrated and Karik CDP (an excellent device that I have yet to write up). With 33 wpc on hand, sound further opened up, allowing me to make a more proper (but not ideal) assessment. Sonically, I could hear the resemblance to the much larger 4312A, as the L20T is in the same mould as other JBL monitors - quite an even frequency response from the treble to the midrange; a slightly perceived midbass warmth allied to deep bass on the lean side. Contrary to some claims , the 035Ti tweeter is not edgy, just playing it straight (see also my 4312A article quoted above) as evidenced by well reproduced mass strings and biting (but not grating) brass in the 3 last symphonies of Dvorak I played (Warner/Silvestri, all recorded with different orchestras and by different engineers). The scale is very decent for a loudspeaker of its size, though of course not at all approaching the scale of the 4312A. It is smoother, has fleshier images and a deeper soundstage than the Linn Kan I normally use in this system (see here). All in all, a more satisfying listen. I think I'd prefer this to many similarly sized modern bookshelves. It is rare to hear downright bad JBL, which cannot be said of many modern loudspeaker brands. All make one yet again weary of the word progress. 
  • Power Requirement The L20T is rated at 8 ohms and efficiency is 87 db, a full 5 db less than my 4312A. Therefore it likes a bit of power, as evidenced from my listening experience. On the other hand, it should be noted it is an easy load (the impedance curve seen in the 4406 brochure is quite benign), so there is no need for high-current amps. This is also borne out by the fact that even my 300B amp drove it nicely (in a more or less near field placement). 
Despite one tweeter out, I am confident this is an excellent pair of loudspeakers. I am taking the tweeter back to HK to be refurbished. Next time, I shall test them with better amplification.

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