JBL Decade L36 vs. Polk Monitor 7 (and a special appearence by Infinity RS6000.) pics

The GW find JBL L36's have had a few days of operation after a full recap and replacement of the "binding posts" for actual binding posts. All three speaker sets sport Dayton poly caps in the x-overs.

This is a first installment review using my Magnavox 9302 fully mod'ed with Edcor OPT's. I picked a track from the regular rotation stack of vinyl and Dire Straits, "Industrial Disease" hit the platter.

The JBL L36's from around '77 and the Polk Monitor Series 2 from around '88 both were models built to provide "high value", affordable speakers. I think the Polks have a '92 production date on them. Two different approaches:

JBL- 3 way with 10" woofer on ported cab. Paper cone tweeter and mid. Big foam ring around the tweeter. :thmbsp:
Polk - 2 way with 6 1/2" mid woofer and a passive 10" radiator in sealed cab. Textile dome tweeter, small foam ring and concave housing in relation to the baffle.

The L36's have the mid and tweet side by side- very close to the woofer. The Monitor 7's are a more traditional vertical stack. Both are driven nicely by ~15W of PP tube amp.

Specs:

Polk Monitor 7 Series 2
Driver Complement
Subwoofer 1 - 10" Diameter (25.40cm) sub bass radiator
Midrange 1 - 6-1/2" Diameter (16.51cm) driver
Tweeter 1 - 1" Diameter (2.54cm) Polk SL2500 dome tweeter

Electrical
Overall Frequency Response 25Hz - 25kHz
Lower -3dB Limit 40Hz
Upper -3dB Limit 23kHz
Nominal Impedance 8 ohms
Recommended Amplifier Power 20-150 w/channel
Efficiency 89 dB
Dimensions
Cabinet Size 24" H x 13" W x 10" D
(60.96cm H x 33.02cm W x 25.40cm D)
Shipping/Other
Total Shipping Weight 33.00 lbs. (14.97kgs)

JBL Decade L36
Decade L36 is the largest in the "Decade" concept.
Specifications:
Manufacturer: JBL-James B. Lansing, California USA (1975)
Principle: Bass reflex
Number and type of speakers:
Woofer: (W) 125A, 250 mm/10" diameter
Midrange: (M) LE5, 130 mm/5" diameter
Tweeter: (T) LE25, 35 mm/1.4" diameter
Crossover points: 1500 and 6000 Hz, variable mid and tweeter controls
Volume in litres: 45
Bass own resonance of the box: 30 Hz
Frequency range of the box: 30-15000 Hz ± 3 dB
Power rating: 35 W
Maximum power: 50 W
Impedance: 8 ohms
Dimensions: 340 x 610 x 350 mm/ 13.5"x 24"x 13.625"
Weight per piece: 18 kg / 38lbs
Sensitivity per JBL technical page: 76db at 1 watt at 15 feet. (They sound like they match the Polks when swapping A to B.)

We have JBL's renowned expertise vs. Polk with a decade of technological advances and much more robust computer modeling available.

The RS6000's will be a postscript as they need waaaay more power than my tubes can provide to really wake up.

First some pics then I will post some musings on what I heard.

itty bitty stock JBL connectors and the new PE binding posts that happen to fit the opening the original posts were in perfecftly!


The gang (poor phone pic)

To start- 10+ years made a BIG difference in build techniques.

The JBL's were built to the "it has to survive a minor nuclear conflagration" standard that vintage JBL is known for. It was the late 70's and the stereo wars were going gangbusters. Real Oak veneer, machine screws with nut inserts to hold in the drivers, and grill frames of not just real wood but also a steel bar to hold the center crease are almost unheard of today in reasonably priced gear. All the grill posts are still there and solid. The woofer and mid drivers sport beefy aluminum frames. A couple coats of Howard's Feed and Wax and they look very nice. Don't build them- you know the rest.

Fast forward late 80's, BPC is the standard in affordable stereo systems. Polk wants to provide sound quality that punches well above a reasonable price point. The drivers get the attention and the cab's are part of the cost control. Vinyl, wood grain applique', plastic framed grills (but cool looking bevel at the edges) are offset by actual 5 way binding posts. Not remarkable to look at but not unattractive, either. Rather stealthy to my eye. Drivers and x-over/post cup attached with wood screws. The money has been spent on the 6.5" driver used throughout Monitor line, the passive radiator and SL2500 tweeter.

How do they sound? (Lpads set to 0 or middle of range)

Bass: The Polks are solid for being so small and using the 6.5 as the live driver. Good attack, think they get close to 40hz before fading.
The JBL's use the L125A woofer and the use of a single radiating surface with a properly sized cab and port provide cleaner bass. The attack is just a smidge less, but bass guitar notes are better defined and the bass drum is cleaner. The 6.5 Polk is the faster driver but it is working alongside the passive rad. This muddies things a tiny amount. I would not have been able to pick it out without a direct A/B test. The JBL's go as deep, but not deeper than the Polks. Impressive for the little 2 ways.

Edge- JBL

Mids: There is a bit of warmth to the vocals in the Polks that is missing in the JBLs. The JBL's are more forward in guitar and vocal presentation. You do have the option to dial them back. Again, clarity goes to the JBL's by a small amount.

Edge- JBL

Highs: At the begining of "Industrial Disease" I think the drummer is hitting his sticks together or on another surface. The JBL's just give you more detail and the sound has more authority. The Polks give a nice clean "click" where the JBL's add enough info to identify you are hearing wood strike something. I was shocked. I was sure the more modern, dome tweeters would win this one. The Polk tweeters do have a slightly "sweeter" note, where the JBL's are on the clinical side. High guitar notes sound just a bit nicer to me from the Polks.

Edge- JBL

Imaging: Polks very good- JBL's just a touch better.
Soundstage: Tie with MAYBE a lean towards the Polks

So there you have it. IMHO the older speakers are the ones for me. I like hearing the little details like breathes and movement of the performers along with the music. I would say the L36's are definitely closer to monitors than the shrewdly named Monitor 7's. BigBill had a good listen and opined that there was possibly baffle diffraction he was hearing from the Polks and not from the JBL's. I doubt I can hear well enough anymore to define the sonics that accurately. EITHER speaker is a killer deal when found at GW, SA, the flea market or CL.


ps: The Infinity RS6000's were run for fun. My little tube amp can't push all 4 10" woofers and the crossovers to reliably compare bass. I will say that the Highs were somewhere between the two smaller speakers and the Mids while a bit laid back compared to the JBL's have a clarity and natural sound that really is nice in vocals and acoustic instruments. Guess that big Poly K dome mid is doing a nice job.

Disclaimer: The previous was all just IMHO

Nice write up Jim, I enjoyed the read. Sounds like Mr. Lansing figured a few things out early on. Im looking forward to a listen!

Just out of curiosity what were you listening to when you compared them?

parman said:

Just out of curiosity what were you listening to when you compared them?

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Music or hardware?

Excellent detailed review. Thanks Fasterdamnit!

Very nice review.

For full disclosure, I am somewhat biased toward the JBLs.

I have a pair of L-36s that I have had since they were new. Won them in a JBL sales contest. They are awaiting a refoam and a crossover rebuild.

Thanks for the detailed review.

Good review. What sources were you using for this as in amp or receiver, cd player, tt etc?

So far i have found that most of the vintage jbl's are very good. There are a few i don't care for as with every brand. I don't have any experience with the polks of that era myself. I have a set of l100t3's, l-1's and a set of l60t's that i am going to e wave.

VROBERTSON said:

Nice write up Jim, I enjoyed the read. Sounds like Mr. Lansing figured a few things out early on. Im looking forward to a listen!

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Thanks Vince! Maybe we can get together later in the week. :thmbsp:

Isotonic said:

Excellent detailed review. Thanks Fasterdamnit!

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You are quite welcome, sir!

JBL GUY said:

Very nice review.

For full disclosure, I am somewhat biased toward the JBLs.

I have a pair of L-36s that I have had since they were new. Won them in a JBL sales contest. They are awaiting a refoam and a crossover rebuild.

Thanks for the detailed review.

Click to expand...

Really?? You are also welcome. Look forward to your review!

nissan guy said:

Good review. What sources were you using for this as in amp or receiver, cd player, tt etc?

So far i have found that most of the vintage jbl's are very good. There are a few i don't care for as with every brand. I don't have any experience with the polks of that era myself. I have a set of l100t3's, l-1's and a set of l60t's that i am going to e wave.

Click to expand...

Vinyl.
Cart= Denon DL-301 MKII
Table=Denon DP59L
Phono Pre= Hypnotoad Clone of Phonoclone (fantastic pre!)
Pre-amp= Mod'ed B&K AVP1000
Amp= Mod'ed Magnavox 9302, 6BQ5 PP.

I was not thrilled with some L100's I heard in the past, but I have no idea if the crossovers had been rebuilt. Now I will keep an eye out for other JBL's .

JBL GUY said:

They are awaiting...a crossover rebuild.

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Any info on the best way of doing this? I have a pair of L36s given to me by my father-in-law who bought them new in the 70s (there are pics of my wife as a child dancing with these speakers in the background). I also recently bought another pair that are sonically great but cosmetically not so much. I'm going to use the spares as my main speakers while I rebuild the x-over and do some refinishing work on my father-in-law's.

Thanks so much. As a former L36 Decade owner (bought them new) and current L26 Decade owner, I really enjoyed that. So true, how well-built they are.

Thanks for sharing, Personally, as someone who owns both JBLs and classic Polk Monitors, I would find it almost impossible to compare the two, they are so different.

If one likes the JBL sound, usually one won't like the softer more laid back and non-fatiguing sound of the, actually, very "musical" Polks.

And if one likes that "smooth" Polk sound one will NOT like the more in your face and forward sounding JBLs.

As for me. I love what both have to offer because I tend to listen to different things on each, so the question above as to the program material was is relevant.

In any case. Two very nice speakers.

cnh2

Great stuff, having just restored my set of L-36's I agree with your assessment. I own some 4311B's and 4410's so I was not expecting the L-36's to be anything special when completed, wow was I surprised. I still have them hooked up as my main surround sound fronts, they are sitting on top of my Klipsch KLF-10's which were being used.

I love their sound, and since I did them in black on black they look more modern. I was not fond of the brown grill so I'm real happy with the way they turned out. After a few days of using them the new Dayton caps settled in and the new foams loosened up, they are very impressive! :thmbsp:

Hey guys, this is actually my first post on audiokarma, but I've been a long-time lurker. My first (and quite modest) TT setup is finally coming together, and these Polks and JBLs are both available in my area. I'm also considering the Advent/1.

If any of you guys have heard all three of these, how do you think the Advent/1 would fit into this comparison? I'll be running them off a Pioneer SX-780.

Cheers! And no worries if you're all long gone and this post only echoes forever alone in cyberspace.

Nice write up. Enjoyed it!

Nice speakers and good to know the vintage JBL's hold their own.

Glenn

Enjoyed this post & don't know how I missed it seeing some Polk 7s in the midst!

Luv my 7B's & looks like you have a nice collection to enjoy.

Rome

I would concur with this assessment, the L36 was my "go to" speaker for a long time. Have great imaging qualities, and are clear and controlled.

midairmatt said:

Hey guys, this is actually my first post on audiokarma, but I've been a long-time lurker. My first (and quite modest) TT setup is finally coming together, and these Polks and JBLs are both available in my area. I'm also considering the Advent/1.

If any of you guys have heard all three of these, how do you think the Advent/1 would fit into this comparison? I'll be running them off a Pioneer SX-780.

Cheers! And no worries if you're all long gone and this post only echoes forever alone in cyberspace.

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Not fond of the advent/1. They lack the bass extension of the original advents, even than the original Smaller Advent, and the highs are a bit harsh with the replacement of the original fried egg tweeters with the the ferro-cooled tweeter, although the latter could be driven hard for long periods with less risk of damage. Overall, the advent/1's just color the sound way too much and their punchiness at 50-60Hz is often misconstrued for the bass extension they lack.

The original Advent would be the fair comparison with the L-36, and the difference would be one of taste more than an absolute one is better than the other.

M2