Jbl L100 Crossover

Update on my JBL L100 Rebuild. Hi Troels, I finished installing my JBL L100 crossover (plus cabinet damping upgrade) last night, in Vancouver, Canada. The sound is wonderful. Thanks for making the product available. JBL L100 / L-100 Century Speaker Review, Specs and Price The JBL L-100 Century is JBLs most famous vintage speaker from the 1970ies and is an absolute classic. It has been produced in several versions over the years, so it is well possible to find slightly different midrange and tweeter placements. You can find an. The JBL L100 Crossover board is nearly the width of the cabinet, indicating just how large the coils and caps are! Jantzen offers proper damping padding to replaces the ineffective fiberglas JBL used inside the cabinet. Click this link to Contact Jantzen Audio to inquire or purchase this JBL L100 Crossover Kit.

My Story

After experiencing JBL L26, I really wanted to get my hands on JBL L100 to see what they are all about. I patiently waited for a year, and eventually, a set came up on eBay – 2h drive from where I live. I made an offer and couple of days later I became an owner of a set of legendary JBL L100A.
As expected from 40 years old second hand speakers, they had normal wear and tear marks on the cabinets, slightly pushed in tweeter dust caps and crackling potentiometers – nothing that would put me off from buying them. Because I was redecorating the whole house, these were placed in the attic and not touched until very recently, when I decided to finally test them.
Please note – prior to this review, I replaced the crackling attenuators with like-for-like l-pads. I also recapped the crossover with basic polypropylene capacitors, as the original ones where slightly out of their tolerances. The wires were replaced with basic OFC cables. More details about these upgrades can be found in the upgrades section. Speakers in their original conduction, were unlistenable, mainly due to the poor connection at the l-pads, which caused distorted and breaking sound. This means that my subjective views below refer to the sound that could be achieved with these speakers, with a bit of work. You will not get the same sound if you buy them and leave them in ‘original’, out of spec condition.

Speaker Info

The JBL L100 Century are the consumer version of the legendary JBL 4310 studio monitors. In the late 60s JBL already had a great reputation for making very accurate, full size monitors for studios. Growing demand for more compact control room monitor, forced JBL to start working on the 4310 model. The requirements were: high power handling, high acoustic output without distortion and smooth frequency response thought entire audio spectrum – all of that from a 45l enclosure. Two years after the work begun, JBL Professional Division introduced the 4310 studio monitors. These speakers quickly became first choice for many well known studios, including Capitol, Deutsche Grammophon, EMI, London/Decca, RCA, etc. In fact, these monitors became so popular, that many musicians and engineers started purchasing these for home use. This in turn, encouraged JBL to produce the consumer version of these monitors – JBL L100. JBL claimed for these to be acoustically identical to the studio equivalents, but finished in more provocative style, appropriate for home environment. And this provocative style is one of the most characteristic features of the JBL L100 speakers – the open cell foam grilles with truncated pyramids. I dare to say that these are one of the most iconic speak grills ever made.
There are different version of both studio monitors as well as consumer speakers:

  • 4310 – fist set of studio monitors featuring distinctive oval baffle for medium and high frequency units. Drivers HF: LE20, MF: LE5-2 LF: 123A-1.
  • L100 – consumer version of the above studio monitor featuring all transducers in the centre line of front baffle. Drivers HF: LE20, MF: LE5-2 LF: 123A-1.
  • 4311 – upgraded version of studio monitors, now featuring all drivers closer to each other on a reassessed baffle to accommodate flush fitting fabric grille. Drivers HF: LE25, MF: LE5-2 LF: 2213.
  • L100A – consumer version of the above studio monitor featuring non-linear drivers layout. Drivers HF: LE25, MF: LE5-2 LF: 123A-1.
    The version I am reviewing is the L100A. So what do we have here? Well, these are relatively large by modern standards, 3 way bookshelf speakers with a very basic crossover network and all driver diaphragms made of paper. What a mixture!
JBL L100 Century Specs
Frequency Response:Unknown
Sensitivity:91dB (1W input, measured at 1m)
Power Capacity:50W (continuous program)
High Frequency Driver:LE25 36mm (1.4″) Paper Diaphragm
Medium Frequency Driver:LE5-2 130mm (5″) Paper Diaphragm
Low Frequency Driver:123A-1 300m (12″) Pressed Paper Diaphragm
Crossover Frequencies:1,500Hz and 6,000Hz
Enclosure Type:Bass Reflex
Enclosure Dimensions (HxWxD):600x360x350mm (23.5×14.5×13.75″)
Weight:24kg (each speaker)
Production Year:1974
Price When Launched:£235 for a pair
Equivalent Present Day Price:£2,560 for a pair
Current UK Price:£300 to £900 for a pair
Look & Feel of JBL L100 Century Speakers

These JBLs are a little like Marmite – you either like them or you don’t. I personally really like them. There is something very appealing about the large white diaphragm and non linear drivers layout – studio heritage perhaps?
The finishing quality of the drivers and attention to details is astonishing. Even these days we rarely see so well made drivers, not to mention 40 years ago. Bass and midrange units are powered by large Alnico V magnets, whereas tweeters are energised by respectable size ferrite magnets. Baskets of the bass and treble drivers are made from a black powder coated aluminium. All diaphragms are made of paper, yes, even tweeters – which is not something that you come across in modern speakers.
The original crossovers are probably the weakest link of these beautiful speakers. They consist of two high-pass filters (two electrolytic capacitors) – one for midrange and one for tweeter, as well two l-pads. The potentiometers are made by Alps, and look like quality units, however, if you are planning to use the speakers with original crossovers, the l-pads will need to be cleaned or replaced.
Cabinets are made from 18mm chipboard, finished in oiled walnut veneer, without any internal reinforcements – fairly rigid but we can do much better nowadays. The grilles… well, the original grilles are very unique but the open cell foam tends to deteriorate with time, hence, you would have to be very lucky to find original, pyramid shaped foam grilles. There are companies that make reproduction of these grilles, but they cost a fortune.

Sound of JBL L100

A lot of music that I listen to is folky and acoustic stuff, without very complicated passages. When I plugged these JBLs for the first time, the thing that struck me was how natural and realistic the voices sound when compared with my modified Yamaha NS1000 which I currently use as my mains speakers. I could not believe how much more realistic Bob Dylan’s voice sounded on Girl From the Country North. The sound was not necessary more clear, if anything it was more rough, but there was something very appealing about it. It was like the singer was singing in a different tonality. If I was to use a metaphor, the NS1000 sounded digital, whereas L100 sounded analogue. Not as refined but very engaging. What benefited Bob Dylan’s voice, did not benefit Eric Bibb’s, which sounded much more natural on my NS1000.
Whenever I test any speakers, I always start with tracks that allow me to isolate sounds. I.e. I use recordings with drums only, with guitars only, with a cappella singing, etc. Then I jump to more complex tracks. This process allows me to identify with greater confidence how the speakers reproduce given instruments/sounds in isolation and then as a part of more complex music passages. And the JBL L100 are quite good at playing different sounds in isolation. The vocals are very special and clapping sounds very realistic. The string instruments sound very good too and I could not really find anything negative about wind instruments. But what surprised me the most is how realistic the drums sound. Probably the most realistic presentation I’ve heard so far. And it is not even the good attack, it is more the tone of it and that you feel like the drums are being played in front of you. Bass is nice and punchy but when plugged into a generator, you cannot hear anything below 40Hz. However, you rarely miss it when listening to most of the tracks.
When it comes to more complicated music passages, it is totally depended on the music choice. Some tracks seem to suit JBLs where as others not. You also start noticing lack of balance, especially when you compare them with very linear speakers. This is probably first set of speakers that I am struggling to decide if I like them more than my current speakers or not. Some really well recorded tracks seem to go better with very refined and analytical sound on Yamaha NS1000, whereas others seem to suit the less refined but ‘honest’ style of JBL L100.
In terms of soundstage, the L100 seem to play everything from the speaker line, with the vocals being pushed in front of the speakers, so they do not give an impression of a deep soundstage. Stereo presentation is fine, however, the speakers do not ‘disappear’ from the room. Your are conscious that the sound is coming from the speakers. It may be because of the bass driver doing so much midrange, and therefore, having really large radiating area generating midrange. This brings us to the subject of positioning these speakers. They are much better lifted off the floor at least 50cm, so the bass driver is closer to the height of your ears.
If I was to criticise JBLs for anything, it would be their rough edges and boosted upper midrange/lower treble, which make them harder to listen to for long periods of time. Also, as soon you start playing them loud, you notice the edginess a lot more, and if you go for concert listening levels, you may get your ears bleeding. Overall, very impressive speakers as they are. I’m not quite sure why people refer to these at tizz and boom as, they do so many thinks so well. Ok, they may not be the most balanced speakers ever, but they are very natural and enjoyable to listen.


Extremely natural presenters especially in terms of voices and drums. Can sound very good at lower listening levels with relatively simple music or make your ears bleed at higher volumes with more complex music passages.

Jbl L100 Crossover
Balance of Sound:
Neutrality of Tone:
Total Score:

Reviewed: April 2017 Published: July 2017

In the 70s and throughout the 80s, the JBL L-100 was a very successful loudspeaker. Having a production run from 1970 to the mid-80s, the L-100 sold in more significant numbers than any other model, and perhaps one of the greatest selling speakers in audio history.

For those squealing about the $4,000/pair cost, a quick look at a currency calculator reveals that the $546 it took to buy a pair of L-100s in 1970 is worth about $3,700 in 2019. By comparison, a brand new Camaro (V8 sport coupe, not a Z28) back in 1970 was about $3,100, and a new Camaro goes out the door, moderately appointed (but still with a V8) is about $45,000. Clearly, JBL has done a better job of keeping pace with inflation. However, to be fair, a 1970 Camaro in great shape will fetch 50 to 100 thousand dollars at auction. A clean pair of L-100 originals about $1,500.

Considering what three to four thousand dollars buys in a pair of speakers these days, the new JBL will not be everyone’s cup of, but the value they do bring to the table is unmistakable. There are definitely more audiophile-y speakers out there, but to this writer, loudspeakers are like buying a painting. Some prefer the French impressionists, while others like Andy Warhol, and yet others like something else.

Jbl L100 Crossover Schematic

If you want more resolution and a broader sound field, think about a pair of comparably priced MartinLogans, or Magnepans. If you’d like a midrange that does a better job with the human voice, think about some Harbeths, Grahams, or ProAcs. We all know that there are tons of choices, and $4k/pair is an excellent speaker budget. You should be able to find something you love with four thousand bucks in your pocket.

Just as one person would rather peel out with a nearly 600 horsepower Dodge Challenger than get a wimpy four-cylinder Porsche Cayman S that is only about 300 horsepower (but goes around corners way better), it’s easy to see the attraction. Fun can be delivered within different paradigms and still be fun.

Comparing to the originals

It’s incredibly easy to let a romanticized past get the better of you. And as a boomer to all of you in younger generations, laugh now. Winter gets longer and more treacherous the older you get. It happens. But we try not to play it that way.

With a pair of mint originals at hand to make a direct comparison, it underlines even further what great speakers the new Classics are. The originals still have an unmistakable cool factor, and there are several updated crossover kits on that market that are claimed to make the originals otherworldly, but that has to be another day. One can only tweak so much.

Unlike today’s reimagined muscle cars paying fairly close visual homage to their 70s counterparts, the L100 classic looks incredibly close, whether the grilles are on or off. The pulp cone midrange driver (albeit updated) and woofer (same) are still in place, though today’s 12-inch woofer now sports a rubber cone surround, where the original featured a pleated paper surround. The paper coned tweeter in the original is now replaced by a titanium dome, which incidentally, JBL has done an excellent job at taming.

Best of all, the sculpted foam grille remains. When I sold these speakers back in the late 70s, everyone knew that grille. Whether on purpose or by accident back then, this was part of what made the L-100 an icon. And this charm remains. Foam choices are orange, blue, and brown.

My originals are orange, so it felt like a great idea to get more subdued brown ones this time. Fortunately, your JBL dealer can supply the other colors for $249 a pair, so I foresee some blue ones in my future. (Ed. note: since this was originally published earlier this year in our 100th anniversary issue, I have acquired a blue set, thanks to staffer, Tom Casselli, who now has the orange. Hmmm.)

While many snooty late 70s/early 80s audiophiles dismissed the L100 of the day, it was a much better speaker than many gave it credit for. Unfortunately, most mass-market retailers sold em with a crappy Kenwood receiver (or something else equally dreadful) that didn’t have the current drive to tame the woofer, or the refinement to get a decent top-end response. I always seemed to remember that connecting my pair up to a Conrad Johnson MV50 was pretty rocking, but again, that memory thing.

Jbl L100 Crossover Schematic

This time though, I was right. Hooking the original JBL’s up to the PrimaLuna EVO400 monoblocks with a full complement of EL34 tubes is indeed glorious, and in fact, even better than I remember.

Out with the old, in with the new

The L-100 Classics were far and away the hit of the 2018 Rocky Mountain Audiofest, even if they were hooked up to an awfully dry sounding Levinson amplifier. As part of the same conglomo, I’m sure they had to use that sterile, boring Levinson amp, but they should have pulled out a freshly re-capped Marantz 2275, or god forbid, a McIntosh MC275. Sometimes you have to cross party lines to reach the desired result. But I heard enough to get the essence.

Earlier this year, getting a pair of these for review proved nearly impossible. Getting someone at Harman to even pick up the telephone is almost impossible. So, kudos for making this review possible go to Mr. Steve Rowell at Audio Classics for putting this together. I rarely buy a piece of gear before the investigation even begins, but I knew I wanted to get old with a pair of these. Staff member Jessica Sieracki took the vintage ones off my hands after, so onward and upward.

Komodo edit download mac. Like several other speakers with a metal dome tweeter, the L-100 is slightly bright out of the box. This went away after about 50 hours of play and is gone entirely by 100 hours. The midrange and tweeter level controls are much more useful than they are on the originals and come in handy fine-tuning to your destination amplifier, cable, and room choice. My living room is a bit livelier than in the main listening room, so a nudge of the tweeter control in the counterclockwise direction is both handy and welcome.


How do they compare?

Now that these speakers have been out for just over a year, the internet abounds with multiple opinions, many centering around the L-100 classic, not being an “audiophile speaker.” It is, and it isn’t. If by audiophile speaker, you mean hyper-detailed, with pinpoint imaging, and pretty much no bass to speak of, then the L-100 classic speaker is not an audiophile speaker.

While attending a demonstration of another manufacturer, the fellow running the show said that when making a speaker, you can go for accuracy, or you can go for something more fun. Clearly, the JBL engineers went for the latter, as these are without question one of the most fun pairs of speakers I’ve ever used.

Like the originals, these are genuinely a garbage in/garbage out speaker. Pair them with low quality, low-resolution equipment , and they will reveal what is behind them. Mate them to great electronics, and they stand up very well indeed.

The L-100s go deep. A comparable pair of mini-monitors from across the pond sound absolutely wimpy in comparison at first blush. But a side by side comparison with a pair of Harbeth Compact 7s reveals the Brit monitors to be cleaner and less cloudy through the mid-band – you can’t argue with the BBC. Think of the Harbeths as a cool white color rendition and the JBL’s a warm white rendition. I own both, I enjoy both, but if you have to choose one, it’s probably going to be down to your ultimate preferences.

The L-100s definitely go way down deep, but the character of the bass rendered is slightly warm. If you’re listening to classic rock or jazz, this is probably going to be pretty pleasant. Those of you on a quest for the absolute sound, whatever that is, will probably go elsewhere. Much like the originals, plopping a Joni Mitchell record on the turntable and easing back in the couch with the L100 Classics is one of life’s great pleasures. Especially with a good tube amp. I’d highly suggest the PrimaLuna, an MC275 or a VAC amp as my first choices.

The JBLs paint a fairly big sonic picture, but it’s more diffuse. While it expands slightly beyond the speaker boundaries, it’s not all-encompassing the way a pair of panel speakers or a perfectly optimized pair of Falcon LS3/5as can. They don’t entirely disappear in the room all the way, but that’s ok.

One other forgotten aspect is the ability to play at a reasonably convincing level. When the other speakers have long run out of dynamic capability, the L-100 Classics still have plenty of headroom left. Oddly, while they are slightly grainy in comparison to a few other speakers, this does not increase at higher levels. I’d venture to guess that some of the insight gained in studio monitor and sound reinforcement has trickled down to these speakers. If you want a pair of real rock and roll speakers, these will do quite nicely.

At the end of the day, the JBL L-100 Classics remind me a lot of that great American amplifier, the McIntosh MC275. It’s not the last word in any of the standard audiophile qualifiers, but I dare you to have a bad day listening to one. The same goes for the L-100 Classics. I dare you to have a bad time listening to your favorite music, no matter what generation it’s from when you’re rocking a pair of L-100 Classics.

Jbl L100 Century

And that’s their charm. Considering I’ve had a pair of the originals in one form or another for the last 40 years, the chance that these will be with me till the end is high. Want a good deal? Show up at the estate sale in 2055. I’m sure our kids will sell em to you cheap.