JBL 308P MKII 8-inch 2-way monitors - first impressions

[Name]

https://www.amazon.com/gp/product/B001UJEKZ6/ref=ppx_yo_dt_b_asin_title_o05_s01?ie=UTF8&psc=1

 

[ripvw]

what I run from the Atom to the JBL's:

https://benchmarkmedia.com/collecti...dapter-cable-pin-3-floating?variant=547761981

 

[Name]

I had actually looked at those cables and contemplated purchasing them

 

[maxxevv]

what I run from the Atom to the JBL's:

https://benchmarkmedia.com/collecti...dapter-cable-pin-3-floating?variant=547761981

What I use :

https://item.taobao.com/item.htm?spm=a1z09.2.0.0.1dd62e8d52Lfxa&id=556486267169&_u=r1u1q9kmcae7

Prices are for a pair, lengths are in meters.

 

[LDKTA]

Lovely. I preferred my 308s to B&W 805 D3s. They’re now being used for my MBP setup and I’m using the 708s as mains for my 2 Ch. setup (movies/shows and music).

 

[Sasha]

Are you using balanced cables? You shouldn't have a hum, but only a slight hiss from the tweeter.

Totally forgot to reply to this. I've used both balanced and unbalanced cables, but turns out that the JBLs weren't the issue at all: the stereo outs on my MOTU 2408mk3 have very low-level hum (not at 50/60hz, but at 100hz, 200hz weirdly iirc) regardless of which type of cable you use.

The JBLs are fairly hissy on any DAC though, balanced or not, which might very mildly excite certain OCD tendencies if people are using them nearfield. For the money they're astonishing though, no question about it.

 

[ripvw]

checked briefly and did not see this video posted elsewhere:

 

[Ron Texas]

It takes more than 2v to drive the LSR's to maximum output. Either used a balanced DAC, a preamp or an unblanced DAC with a preamp. I got the best results with an unbalanced Grace M9xx which has a 5v maximum output.

 

[monkeyboy]

What is the consensus on these for a L/C/R home theater application? I'm thinking of 308s for L/R and maybe a 305 or 306 for the center channel. Looks like finding a decent AVR is also a problem....

 

[LDKTA]

What is the consensus on these for a L/C/R home theater application? I'm thinking of 308s for L/R and maybe a 305 or 306 for the center channel. Looks like finding a decent AVR is also a problem....

They'd perform very well and there are plenty of AVRs on the market with preouts. If possible, I'd look to match your LCR. 3 308s.

 

[Robbo99999]

I'd like to see the 308's tested here on this website by Amir. He's done the 305, so I think it makes sense to test the opposite end of the extreme of the series, that way we could probably assume the 306 was ok if the 308 was ok.....I'm thinking it might be hard to marry the 8" woofer of the 308 with the 1" tweeter. I've got the 308's by the way and run HF Trim at -2dB which also pleases the UMIK measurements for a Harman Curve.

 

[daftcombo]

I'd like to see the 308's tested here on this website by Amir. He's done the 305, so I think it makes sense to test the opposite end of the extreme of the series, that way we could probably assume the 306 was ok if the 308 was ok.....I'm thinking it might be hard to marry the 8" woofer of the 308 with the 1" tweeter. I've got the 308's by the way and run HF Trim at -2dB which also pleases the UMIK measurements for a Harman Curve.

Agree it'd be a welcome review. But not because I have a pair (I have the 305p) nor because it would tell about the 306 (how?).

 

[Robbo99999]

Agree it'd be a welcome review. But not because I have a pair (I have the 305p) nor because it would tell about the 306 (how?).

Well I think by reviewing the 308 (now that we also have the 305 reviewed) then if the 308 were to measure well then the chances increase that the 306 would measure well too. My reason for saying this is that I see the 308 as probably the most difficult to get right considering they're trying to combine an 8" woofer with a 1" tweeter....I think it gets progressively harder to produce a good result in a 2 way speaker when combining an ever increasingly large woofer with a tweeter, due to crossover issues. It's also possible that the larger cabinet size can mean increased likelihood of unwanted vibrations & distortions. Therefore I think if Amir was to test the 308 and it measures well (like the 305 did), then it's probably pretty safe to assume that the 306 will be ok too. So I think if you were gonna have to choose 2 speakers to review from the 3 series range you'd choose the smallest & the largest - the 305 and the 308. That's my thinking.

 

[daftcombo]

Well I think by reviewing the 308 (now that we also have the 305 reviewed) then if the 308 were to measure well then the chances increase that the 306 would measure well too. My reason for saying this is that I see the 308 as probably the most difficult to get right considering they're trying to combine an 8" woofer with a 1" tweeter....I think it gets progressively harder to produce a good result in a 2 way speaker when combining an ever increasingly large woofer with a tweeter, due to crossover issues. It's also possible that the larger cabinet size can mean increased likelihood of unwanted vibrations & distortions. Therefore I think if Amir was to test the 308 and it measures well (like the 305 did), then it's probably pretty safe to assume that the 306 will be ok too. So I think if you were gonna have to choose 2 speakers to review from the 3 series range you'd choose the smallest & the largest - the 305 and the 308. That's my thinking.

I somehow agree but if you had the 306 you'd probably rather have the 306 reviewed right? ;-)

 

[Robbo99999]

I somehow agree but if you had the 306 you'd probably rather have the 306 reviewed right? ;-)

Yeah! But my logic for the greater good is sound! :-D

 

[half_dog]

Hi guys! First, I'd like to anticipate my apologies if my texts be confusing in any way. English is not my first idiom.
So, I´ve bough a par of JBL 308P MKII and soon as they have arrived I assembled the system and played some songs, but I perceved something strange, the music were "pulling" to one side and some instruments sounded muffled coming this specific speaker. So, I decided to do some rudimentar measurements using a US 366 and a electret mic adapted to phantom power. The sweep coming from this specific speaker sounded weird. So, I measured each speaker (inside a livingroom = "strange curves") in the same position without move the mic or change the cables, only realocating the speakers and I got this (FR.png). The bad speaker are the last two measurements (blue and orange) and green and red curvers display the good one. Looking at THD (dis_bad) there is a peak reaching %2. I suppose it is a problem related to this circuit, not a driver issue.

I've considered it a defect speaker and took it to a service center and here where my headache really begins. They didn´t accepted it at first, I had to take both speakers for them to compare between them. So they consented there was a problem and replaced the tweeter (?). And as I already expected the issue wasn't solved. I took it there again and so far no news from JBL.

Guys, am I being too petulant or I really have a faulty speaker?

 

[AnalogSteph]

Looks like an assembly error - either woofer or tweeter is connected out of phase on the bad unit. That would be a 5 minute fix with the soldering iron.

The culprit shouldn't be too hard to find with some test tones with one channel inverted. Put both good + bad face to face and play e.g. 440 Hz generated like that. If woofer phase is OK, the tone should cancel out almost entirely. If it doesn't, retry with both channels the same polarity and see if it does then - then it's the woofer. Otherwise it's got to be the tweeter.

Since the tweeter has already been changed I suspect it's the woofer.

 

[half_dog]

Huum I got it, but the speaker is under warranty, I'm not supposed to pry it open... And it is at the service center at this moment.

I forgot to mention that if I play an 2kHz signal and feed the speaker at a low level everything seems fine, but increasing the signal there is a point where suddenly emerge its third harmonic (6kHz). It is able to hear this component and it shows up on RTA and it is independent from the volume controlled on speaker's back panel. That does not happen with the other speaker. I guess there is something happening that makes the signal saturates, maybe something is triggering its limiter sooner.

 

[maxxevv]

Are the gain switches at the back set in the same position?

It sounds stupid, but its one of the possibilities.

 

[half_dog]

@maxxevv sadly this measurement I've posted both speakers were set in the same position - 8 in this case. I measured with it at 5 too and got the same results. These speakers are surprisingly well matched, but not at 1,5 to 4kHz