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JBL 308P MKII Studio Monitor Review

thewas

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Repair gets more difficult when its a multiple layer PCB, which I doubt is the case on most loudspeakers yet?, but getting the specialised amp or DSP chips as spares can get more difficult in some years in comparison to more "classic" electronic parts which were produced for decades and in millions.
 

FTB

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This is definitely not true, but yes, it is hard to repair them yourself.
Thank you, so my guess was false.
Why it isn't more reliable ?

I googled the thing, I found mostly stuff about electrolytics as the weak point. Well, mostly amps have electrolytics...

I guess there is another reason.

Repair gets more difficult when its a multiple layer PCB, which I doubt is the case on most loudspeakers yet?, but getting the specialised amp or DSP chips as spares can get more difficult in some years in comparison to more "classic" electronic parts which were produced for decades and in millions.
This is what I fear, to enjoy the speakers but having to throw them in case of failure.
A passive components design is easy to fix...

I'm wondering about this because I have here two good quality woofers, Seas W22NY001, that I bought a few years ago to make DIY speakers which would go with an external amp.

The thing is I'm not sure to have the skills and the technical ressources (well I don't have anechoic chamber at home !) to make passive speakers that measure as well as these JBL about FR linearity, directivity, no Xover error, baffle step etc
but that could last a lifetime...
 

maverickronin

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What about in case of failure ? I guess class D amp are less prone to failure as it runs cold but if so, is it as easy to repair as a passive components amplifier or we do as we do nowadays, replacing all the board ?

Component level repair is possible, but not for the inexperienced, and in this case the labor would be way more than just buying a new speaker.

Here's what's involved in fixing a 308 MKI


And if it was a bad microcontroller, with it's custom and secret code, then it would have been unfixable without nicking the same part from a donor board.

Why it isn't more reliable ?

In this JBL's case, because they are built down a price. The best possible SQ for cheapest possible MSRP. Front loading all the engineering into a really good waveguide and DSP filter optimization so they can make something that sounds good from a thin injection molded baffle and dirt cheap drivers. The electronics are built to a reasonable enough standard of quality, but they aren't meant to last for decades.

As someone else on ASR put it, the JBL 3 series are top shelf engineering with bottom shelf components.

I have a pair of the 305 MKII and they are certainly an excellent value.

I googled the thing, I found mostly stuff about electrolytics as the weak point. Well, mostly amps have electrolytics...

Switchmode supplies stress the electrolytics much more than traditional linear supplies. Plus they usually render the supply completely inoperable when they drop below a certain tolerance - or just explode. More often than not a device with a liner supply will just suffer from more mains hum as the caps start to age.

Any separate amps with switchmode supplies are vurnrable to the same kinds of failure, but there are still brands which sell amps using traditional linear supplies and even a few active speakers that still use them. The big reliability advantage of passive speaker and separates is that they're basically standard so you can easily keep a spare amp or buy a new replacement from anywhere. With actives, you have to hope the company is still in business and/or sell spare boards.
 

FTB

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Thank you for all the details here.
Watching the repair video, oh god for sure I'll not be able to repair a pair of these ones.

I don't doubt of the qualities of these 308p as they are observed by the measurements but I took a look to other speakers reviewed here.
At a higher price I could go for the Selah Integrity DIY kit as the qualities are mechanically obtained instead of DSP correction of low-end elements, distortion values are way better, LF extension is pretty much the same (don't want to add a sub) plus the possibility to make strong and lasting cabinets (well, plastic is plastic), external electronics in case of failure etc.

The big reliability advantage of passive speaker and separates is that they're basically standard so you can easily keep a spare amp or buy a new replacement from anywhere. With actives, you have to hope the company is still in business and/or sell spare boards.

Fully agree with that, the pleasure of good passive speakers seems less short-lived.

You wrote SMPS stress the electrolytics more, is it because of the HF switching ?

Thank you for the work done here on ASR which allows us to not buy blindly.
 

Chromatischism

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My only question is, do passive crossovers change performance with temperature? If a lot of "EQ" was done, resistors get hot after a while. Intuitively, heat affects conductivity, I just don't know if it's enough to make a difference.
 

maverickronin

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Fully agree with that, the pleasure of good passive speakers seems less short-lived.

It depends on the brand too. Anecdotally ATC and Genelec have reputation of lasting forever and also provide service and parts for out of production models too.

Personally I would take a Genelec over a over a new brand like Kii or D&D which hasn't been time tested yet.

You wrote SMPS stress the electrolytics more, is it because of the HF switching ?

Yes
 

FrantzM

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It depends on the brand too. Anecdotally ATC and Genelec have reputation of lasting forever and also provide service and parts for out of production models too.

Personally I would take a Genelec over a over a new brand like Kii or D&D which hasn't been time tested yet.



Yes
As a small business owner, i can remember when I started 30 years ago...
It behooves us the enthusiasts, to support innovative companies that produce high performing and high ROI products such as Kii and Dutch & Dutch.
Genelec , ATC had to start too...
This is of couse, a personal decision; one I would be happy to make: The 8C remains high on my list

BTW, very satisfied owner of 3 LSR 308.
 

Sal1950

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This is of course, a personal decision; one I would be happy to make
We possibly have to take financial position into account.
Some of us can afford to lose out on a bad investment.
Some not so much so.
 

807Recordings

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I will sort of take back my previous comments on the noise with these speakers. Lately I been working on a new track in the studio and just finishing up some slight details on my reverbs and delays (dub techno). As I am not listening loud the noise although subtle has been a bit distracting. Also I will add the speakers are under-powered and will compress with the internal limiter which can give a false impression of how a mix really sounds. Usually the loudness isn't at the mix stage but sometimes when I am working on individual tracks that are coming in live and not compressed. Often I need to have levels at max and it is still not loud enough. Not that the overall RMS is loud just that there is no headroom.

Second point when listening at low levels the stupid speakers often turn themselves off with the auto standby. One of my biggest annoyances with this monitors is this and that you have to turn up to a fairly loud level for them to start again even though the sub is already on.

Still I standby that at the price point nothing comes close but more and more I am leaning toward the KH-310.
 

Buckster

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when optimising signal to an active speaker - does it matter where the "gain" is - I'm thinking not but I thought I'd ask

I've my 308 IIs set to 10 (max volume and set to -10dBu) - they are connected to a Denon 7200WA av amplifier - and in speaker settings they are set at I think either 0 or +0.5 - which means my JBL passive rears one is at -8

this is fine but means for some 5.1 connect I really have to crank the volume up on the amp - to something like -7dB - so not that far off "reference"

is it better to have speaker levels set not above 0 - and then crank up master volume as much as needed

or is some compromise better - say the actives set to +2 or +3 in speaker levels (not on the speaker) and then use less master gain/volume on amp ?

I'm assuming it doesn't matter - but I was just wondering please.

The JBL rears are A130s - I've been very very pleased with them - I'm considering buying another pair for fronts to replace the 308s

many thanks
 

807Recordings

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@Buckster If you can actually keep your speakers from not going into standby I will be amazed. Mine always turn off even when I am listening at lower levels and often it takes a fairly good level above the threshold for them to come on again. Maybe that is my biggest thing I dislike about them and why I never used them in the home theatre.
 

Buckster

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thanks for your reply - the auto standby actually seems well behaved - not had any issues with it

turns off when not in use and is on when not expecting - I've never had it go off during a film or playing a game
 

807Recordings

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thanks for your reply - the auto standby actually seems well behaved - not had any issues with it

turns off when not in use and is on when not expecting - I've never had it go off during a film or playing a game
So then if that is the case then basically I would run the system with a higher gain and adjust on your AVR the levels as this will give you the most dynamic range. Let the AVR do all the calculations I would think is the best and keep everything flat.
 

Buckster

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as in level levels in speaker levels no higher than 0 (to avoid pre-amp clipping) and crank master AVR gain up

or tweak up the speaker levels ? I think I'd read somewhere to keep them to near 0 to try and avoid clipping - but I find it all confusing to whether more likely to introduce clipping by keeping speaker adjustments near to 0 and cranking up master gain or adjusting speaker levels up and not having to use so much master gain

just felt with some content where the D.Digital + mix volume is very low for reasonable listening volumes I'm up at near -7dB on amp and it seems to sound a bit "flat"
 

807Recordings

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0 or max on the actual speaker is what should be set. The AVR will then adjust the levels. I am guessing you are using the AVR software for the setup? If so the microphone should set all the levels correct as to not clip and also the Xover points.
 

Robbo99999

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@Buckster If you can actually keep your speakers from not going into standby I will be amazed. Mine always turn off even when I am listening at lower levels and often it takes a fairly good level above the threshold for them to come on again. Maybe that is my biggest thing I dislike about them and why I never used them in the home theatre.
Actually, you can turn off the standby feature. It's in the instruction booklet that came with your 308p speakers. Can't remember off the top of my head how you turn off standby, but it's a very easy sequence to do once you've found that in your instruction booklet, you just press a few buttons in sequence or something, nothing to take apart or anything. That's how I run my speakers, I've turned off standby, just felt "cleaner/simpler" and they didn't always turn themselves off overnight anyway.

About the gain, I'll just add that I think I saw somewhere that the amps within the 3xxp Mkii speakers performed/measured better around mid range point rather than at max volume, but I'm not totally sure on that, you might have to google that. Either way, if you need the extra gain, then this can't really stop you from cranking up the volume, as listening level is more important than running at the optimum point for the 308p internal amp....but it might influence your gain structure you decide on.....but google it first if you're curious as I'm not 100% where I saw this snippet re the internal amplifiers of this JBL speaker line.
thanks for your reply - the auto standby actually seems well behaved - not had any issues with it

turns off when not in use and is on when not expecting - I've never had it go off during a film or playing a game
 

Jake C

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Great drivers, poor amplification. Looks like a prime candidate for Mods.
 

RCAguy

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Experiment:

JBL LSR 308
"Normal" room noise
Simultaneous measurement, single speaker active
About 82db SPL at listening position

Mic 1 at Listening Position
Mic 2 hanging over the front of the speaker, so the capsule is in the plane of the front of the cabinet - more extreme than the Klippel measurement position, but I don't have a stand to hold the mic where I might like to put it.

Using dBc setting - graph sets tone level received to 0dB, to allow comparison of levels of noise and distortion relative to the tone


View attachment 92262

Tone and harmonics are much higher relative to room noise in the close measure

Third harmonic just peeking out of the noise floor at the listening position

Disclaimer: quick test, not trying to make it look bad or good, there will be variations with frequency and the phase of the harmonics (levels will change) at the listening position. Take the measure with a little suspicion, but useful to illuminate the basic idea.

I set it up, frequency selection - random, at least, nothing specific and no tuning - saw harmonics at the speaker, raised amplitude until one of the harmonics peeked out of the noise floor at the listening position.
That 428Hz artifact is so narrow, could it be a non-linear box resonance rather than a driver (probably not the amplifier)?
 
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