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JBL 705P / 708P

Bjorn

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There's another thread that was started about room correction and I suggest you continue the debate there.

But bottom line is that showing measurements of the speaker and driver on-axis has no relevance to what we're talking about. It's simply not possible to correct myriads of reflections arriving simultaneously or at different times with different spectral content from different angles with a software in way that works. That's simply impossible without making something else much worse. Not to mention that when taking into account superpositions between drivers/speakers, and the fact that even if you actually could effectively cancel out reflections ; it wouldn't be the psycho acoustically correct way of doings things. With treatment you are trying to achieve different design goals with different type of treatment. Something not possible in any other way.

The difference between a well treated room and something based on "room correction" is completely night and day. One sounds completely unnatural and weird if one corrected much of what's non minimum phase behavior and the other sounds natural and spectacular.

The irony here is that despite that some designers of room correction softwares say it works to correct the room and reflections, they also say you need treatment for a really good result. Where is the logic in that if the room correction truly worked as they say? But the fact is that it doesn't and even some of the speaker correction that is done is something one should ideally avoid.
 

Krunok

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That's simply impossible without making something else much worse. Not to mention that when taking into account superpositions between drivers/speakers, and the fact that even if you actually could effectively cancel out reflections ; it wouldn't be the psycho acoustically correct way of doings things. With treatment you are trying to achieve different design goals with different type of treatment. Something not possible in any other way.
I don't agree with your statement that "something else" would end up being much worse. As you addmitted yourself frequency response can be fixed by room correction and that is something all folks would hear and recognise as a step forward if done properly. Regarding the things in the time domain - well, from what I was able to see here, most of the folks believe it is of no practical importance as they claim difference can't be heard when you fix time domain. Some say contrary. Personally, I believe that truth is somewhere in between - I believe you can hear the effects of time aligned drivers but I also think tit is a very subtle change.

However, the effects of room eq can be measured and if I was to summarise it's effects it would be something like this:

- when you fix frequency response above Schroeder frequency it stays fixed throughout the room
- you can fix LF response at LP. It may make LF response worse at some other point of my room but as I don't sit and listen music there I don't really care
- when you fix time alignement and measure step response it stays fixed throughout the room. Of course, if you measure it 0.5m away from the speakers it will look much better than further away because the reflections will affect it, but it will still be better than when it wasn't aligned

Nobody claims that room eq can cure all evil, but it certainly helps in a very measureable way. I see room treatment more of a complementary action than a replacement for room/speakers eq. The better your room is in acoustical way the less you need to EQ it but your speakers will still need correction even in an anechoic chamber.

The difference between a well treated room and something based on "room correction" is completely night and day. One sounds completely unnatural and weird if one corrected much of what's non minimum phase behavior and the other sounds natural and spectacular.
This statement is very subjective unless you can offer some objective arguments/measurements for it.
 
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Sal1950

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The irony here is that despite that some designers of room correction softwares say it works to correct the room and reflections, they also say you need treatment for a really good result. Where is the logic in that if the room correction truly worked as they say? But the fact is that it doesn't and even some of the speaker correction that is done is something one should ideally avoid.
The logic is simple, make the response as good as possible before attempting any digital eq.

That really is a matter of opinion since, as I mentioned before, no 2 systems are going to react to the correction in the same way.
 

Bjorn

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I don't agree with your statement that "something else" would end up being much worse.
Quick and last reply, any more discussion regarding this should be done in the other thread.

I was referring to the time domain behavior of the room. And there's no doubt that this will become worse. Also well known that time domain of a room is extremely important. More important than the frequency response. Actually the frequency response follows the time domain! This isn't really up for discussion.
 

Krunok

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Quick and last reply, any more discussion regarding this should be done in the other thread.

I was referring to the time domain behavior of the room. And there's no doubt that this will become worse. Also well known that time domain of a room is extremely important. More important than the frequency response. Actually the frequency response follows the time domain! This isn't really up for discussion.
Hmm.. How about providing some links to the relevant sources that support your opinion?
 

jhaider

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Also well known that time domain of a room is extremely important. More important than the frequency response. Actually the frequency response follows the time domain! This isn't really up for discussion.
Cite?

"Time domain" is one of those buzzy bits of jargon people throw around a lot without much rigor, and usually to defend poor performance in an area known to be highly relevant to human perception of sound quality.
 

stunta

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It buzzed, it popped and then it gave out. One of my 708Ps (which I got just a few weeks ago) is in for repair. This is a one year old unit I got used - previous owner did not have any issues.

Not sure if its a coincidence, but this happened after I connected Roon to the built-in Chomecast on my A/V processor. Is it possible it sent a signal that killed the amp? Does the 708P not have any protection circuit? I started hearing a loud buzzing sound, so I turned the speaker off and on. After that I played some music (not through Chromecast) and it started to make loud popping sounds so I turned it off and on again. No sound. Factor reset didn't help.

Luckily the unit is still under warranty and there is an authorized repair center 30 mins from me. The guy there said that generally JBL sends out a new amp module from Mexico. So I have to wait a couple of weeks. Hopefully they don't close the border anytime soon :facepalm:

Is this just my bad luck or does JBL generally have ****** quality control?
 

Jaimo

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It buzzed, it popped and then it gave out. One of my 708Ps (which I got just a few weeks ago) is in for repair. This is a one year old unit I got used - previous owner did not have any issues.

Not sure if its a coincidence, but this happened after I connected Roon to the built-in Chomecast on my A/V processor. Is it possible it sent a signal that killed the amp? Does the 708P not have any protection circuit? I started hearing a loud buzzing sound, so I turned the speaker off and on. After that I played some music (not through Chromecast) and it started to make loud popping sounds so I turned it off and on again. No sound. Factor reset didn't help.

Luckily the unit is still under warranty and there is an authorized repair center 30 mins from me. The guy there said that generally JBL sends out a new amp module from Mexico. So I have to wait a couple of weeks. Hopefully they don't close the border anytime soon :facepalm:

Is this just my bad luck or does JBL generally have ****** quality control?
Yikes! sorry to hear this.
 

Sal1950

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Is this just my bad luck or does JBL generally have ****** quality control?
Crib death, sadly the enemy of all electronics. If she's gonna fail, it will do so in the first hours of life. Some small component or other just wasn't up to the task and died, can happen to anyone.
Sorry for your experience!
 

stunta

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If she's gonna fail, it will do so in the first hours of life
This is more than a year old. I am guessing the previous owner did not drive it too hard because he had it in his office (near-field).

It was working fine at high SPLs, sounded effortless.

Luckily I still have my ATCs so I am not without speakers.
 

Sal1950

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This is more than a year old. I am guessing the previous owner did not drive it too hard because he had it in his office (near-field).

It was working fine at high SPLs, sounded effortless.

Luckily I still have my ATCs so I am not without speakers.
Ah, I thought it was brand new, didn't read close enough.

"high SPL's", Yep that's the reason, you blew it up, your fault then. LOL
 

Jaimo

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Somewhere in their literature, JBL claims that these speakers are designed to run at high levels for hours on end. I don’t doubt that the design is sound and intended for real taxing studio work.

It’s more likely component failure than shoddy design work.

Let us know what the repair centre comes back with.
 
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Thanks, watchnerd. I've been on the edge of my chair waiting for news of a new 4-series from JBLpro. These powered 7 series monitors are quite interesting to me.

At $ 2000 each, the 708P is more than I wanted to pay. I could spend that much but I don't want to.

At $ 1000 each, the 705P is at the upper end of what I wanted to pay

My application is for 2 channel music (only) in a ~ 20 by 15 foot room with a flat 9 foot ceiling. We would be listening at a distance of 7-9 feet with average volume levels in the 75-85 dB range.

There are a variety of pro audio monitors but it will be good to have a JBL alternative to consider. Some of the other alternatives are from foreign companies; I always wonder about how solid their presence in Vidmate iTunes Notepad++ the USA will be in the future.

I look forward to seeing good reviews and thoughtful comments by users.
I'm still don't understand very much about HiQNet, other than it seems to be a tuning and calibration system. Maybe @amirm or someone else with Harman connections can shed insight.
 
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k3nb5t

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Does it do it on the digital input?
I noticed this same hiss, and performed the same steps that @Thomas savage did. Having recently acquired a device with AES3 output, I put it to the test using a calibration mic I had nearby (Emotiva EMM-1, for the curious). I recorded the speaker while turned off for control, then also at idle with both the analog and AES inputs selected. The mic was in the same place for all 3 tests. My ear detected the hiss originating from the compression driver, so I positioned the mic in the mouth of the horn.

Control: Speaker off
JBL off.png


Delta: analog vs control
analog spectrum delta.png


Delta: aes vs control (sorry for the different scale)
digital spectrum delta.png


And finally the aes and analog on the same plot (blue is analog, white is digital)
digital vs analog.png


Pretty sure I messed up something on either the recording or the export from Audacity that resulted in the HF roll-off of the analog and control, but it's all ultrasonic, so I didn't bother re-doing it.

I think the graphs are far more trustworthy than my ears, but I'll add my observation as well. Subjectively, I don't hear the hiss on the digital input unless I get right up against the speaker, while I found the hiss on the analog a bit taxing after some time. I suffer from mild tinnitus, so I'm probably not a great test in this regard. Could be with the digital that it just fell into a frequency being masked by my tinnitus...
 

k3nb5t

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@Jaimo asked about the SMSL B2 driving the 708p's in a different thread. I thought I'd post my findings here, as it relates more closely to the JBL than the DAC that thread was covering.

I'm quite pleased with the B2 so far. Aesthetically, it's pretty much identical to the SMSL SU-8. It has a nicely anodized aluminum case and is pretty solid. I installed the Thesycon drivers that SMSL licenses for this unit. Thesycon + XMOS has proven to be a pretty rock solid combo. I'm an avid PC gamer and have noted issues with several DACs under CPU and/or IRQ pressure. In all cases, I attributed these issues to driver problems. This unit has been flawless.

Unfortunately, the remote control was dead on arrival. I'm not sure I'll ever use it, but it seems to be the only way to access the menus on the SMSL. I'll be contacting SMSL to see about getting one that works. If you end up purchasing one, hopefully you'll have better luck.
EDIT: I figured the remote out... you have to press the "B" button to put the remote into the proper mode... hooray for user manuals!

I posted my observations regarding the hiss above, so you can check that out. In addition to the hiss, I had issues with a low volume scratchy/static sound coming from the left speaker after extended runtime. Volume was so low that it was easily masked once any audio was fed to the speaker, but still not great out of such an expensive speaker. I haven't noticed this noise return since switching to AES. Time will tell, I suppose.

A couple extra notes... It takes about 2.5 seconds to switch sample rates. Sample rate switches are also accompanied by a few low volume pops/clicks. I assume these are properties of the DAC in the 708p, not the SMSL B2, but I wouldn't really know how to test this. Additionally, the B2 offers no volume control, so you'll be limited to software volume control. None of these are negatives for me, but some people care so I thought I would mention them :)
 
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Jaimo

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Thanks for the update - I've been contemplating picking up a SMSL B2 but the lack of a volume control kills this option for me. Besides, I am very happy with the SMSL SU-8 / LSR708P combo.
 

Jaimo

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Also, my LSR 708P’s have negligible hiss. For me to hear anything, I have to place my ear right into the waveguide. I am using a balanced cable that I made up using Canare L4E6S star quad cable and this works like a charm.
 

Music1969

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Thanks for the update - I've been contemplating picking up a SMSL B2 but the lack of a volume control kills this option for me. Besides, I am very happy with the SMSL SU-8 / LSR708P combo.
Hi, are you feeding your 708P's via analogue outputs from SMSL SU-8?

Do you prefer this to sending your 708P's AES3 (digital)?
 

stunta

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Somewhere in their literature, JBL claims that these speakers are designed to run at high levels for hours on end. I don’t doubt that the design is sound and intended for real taxing studio work.

It’s more likely component failure than shoddy design work.

Let us know what the repair centre comes back with.
First JBL sent them the wrong (705P) part. Then they said they don't have any parts (this is the entire amp+dsp module) for 708P, so they sent a brand new unit. Maybe I should send in my other unit for repair as well :)
 
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