JBL LSR 308 in the house

[fas42]

I would say that he is not measuring the type of distortion that he's hearing, which would be equivalent to IMD of the relatively low level high frequency information in the recording - something that standard THD measurements would not pick up. I would suggest that he lowers the volume level so that he could listen, comfortably, "a few inches from the driver" - think, headphone listening ... does it still sound "fizzy"? And continue in that vein ...

 

[RayDunzl]

Ultra-Nearfield - Red - 6 inches or so - and listening position - Green - 10 feet - unsmoothed of the left JBL:



It's room interaction, not speaker.

Compare:

JBL Ultra-Nearfield - Red - 6 inches or so - and listening position - Blue - 10 feet - unsmoothed of the left ML:

 

[RayDunzl]

I don't think the class D amps are doing that. The effect went away when Ray measured up close to the speaker. Didn't Ray also show a distortion plot of both speakers, and while the panels were lower, the 308s didn't have high distortion levels other than in the low frequencies as I recall?

There is a slight broadband hiss measurable close to the speaker, shown earlier, doesn't seem to be correlated with the dips. Not measureable from the listening position, it's below the noise floor.

Distortion: Correct, higher by 10dB or so, at the listening position, like -40/-50dB instead of -50/-60dB with the panels.

 

[RayDunzl]

I would say that he is not measuring the type of distortion that he's hearing, which would be equivalent to IMD of the relatively low level high frequency information in the recording - something that standard THD measurements would not pick up.

I did some dual-tone measurements, the results were very similar between the JBl and ML, so much so that I didn't see that as a difference.

 

[Blumlein 88]

There is a slight broadband hiss measurable close to the speaker, shown earlier, doesn't seem to be correlated with the dips. Not measureable from the listening position, it's below the noise floor.

Distortion: Correct, higher by 10dB or so, at the listening position, like -40 -50dB instead of -50 -60dB with the panels.

Thanks for the measurements Ray. Just noticed you could go wireless on your subs.

http://www.parts-express.com/dayton...itter-receiver-system-for-subwoofers--300-580

Those might be useful if they work well. You wonder about them at $69.

 

[RayDunzl]

I have one, haven't used it with the subs as I still have them in "stereo", repurposed it to send what I was listening to in this room to Mother's sidewall-adjacent room.

It isn't bandwidth restricted that I notice causally - not for subs only or anything.

Muffled boom from behind the wall didn't seem nice to subject her to, so I fixed her up with the Infinity P-363 run off an old Pioneer SX-780 with the receiver attached to an input to disguise my noise with the actual program when we got too loud on Beer Saturdays.

Unfortunately its range isn't quite enough to get out to the garage or the main bedroom. I haven't experimented beyond "didn't work".

You wonder about them at $69.

It was a $20 (or $40, I forget) add-on when buying the subs, so I took that chance.

 

[fas42]

I did some dual-tone measurements, the results were very similar between the JBl and ML, so much so that I didn't see that as a difference.

With conventional dual tonemeasuring, the levels of the tones would be comparable - I would be interested in what happens when the higher tone is much lower in amplitude than the lower, say 40dB down - what happens to the distortion spectrum directly related to the higher frequency, as the amplitude of the lower frequency varies.

What this could tell one is how much the variable current draw on the PS, in the JBLs, is impacting the distortion behaviour.

 

[Blumlein 88]

With conventional dual tonemeasuring, the levels of the tones would be comparable - I would be interested in what happens when the higher tone is much lower in amplitude than the lower, say 40dB down - what happens to the distortion spectrum directly related to the higher frequency, as the amplitude of the lower frequency varies.

What this could tell one is how much the variable current draw on the PS, in the JBLs, is impacting the distortion behaviour.

You are talking about the old SMPTE standard. 60 hz with 7 khz. With 60 hz being in a 4 to 1 ratio with the 7 khz to see if distortion of the 7 khz is modulated by the 60 hz tone. Then again, I would expect the class D switching amps in these using switching supplies aren't effected by the 60 hz so much.

 

[RayDunzl]

Somewhat incredibly to my antique eyes, this chip turns out to be the 2 x 50W "amplifier" in the 30x Series

STA350BW

http://rdimitrov.twistedsanity.net/blog/show.php?entry=JBL LSR305 Teardown and Analysis

 

[watchnerd]

I have Christmassed myself with a pair of powered monitors.

http://www.jblpro.com/www/products/recording-broadcast/3-series/lsr308

View attachment 4010

Oops... Measurements aren't true below 200Hz - see post #5 below

Here are some initial measurements. They are on barstools directly in front of my main speakers. The microphone is located at the center of my brain between my ears at the listening position.

Sweep and Pink Noise, both speakers playing - 1/6 octave smoothing on the sweep, 1/48 on the pink:

View attachment 4011

Left, right, and both sweep at 1/12th octave smoothing:

View attachment 4012

Impulse (not normalized) for left, right, and both:

View attachment 4014

Step (not normalized) and Inverted for left, right, and both:

View attachment 4016

Distortion for both speakers - numbers at 1kHz:

View attachment 4017

Distortion for both speakers, normalized to fundamental, displayed as percent with 80dB fundamental:

View attachment 4020

Distortion for both speakers, normalized to fundamental, displayed as dB relative:

View attachment 4021

Waterfall, both speakers, 1/6 averaging, dropping into the ambient/measurement noise floor:

View attachment 4022

Impulse Response both speakers, dBFS setting, 350ms:

View attachment 4023

What software are you using?

All I can tell is that it's Windows-based and looks to run in Java.

Also would be curious to know what mic.

 

[RayDunzl]

Room EQ Wizard (free) and MiniDSP UMIK-1 ($100 or so when shipped)

DSP is MiniDSP OpenDRC-DI - $325 + shipping

DRC is AcourateDRC - $80 Euro + VAT if required

 

[watchnerd]

Room EQ Wizard (free) and MiniDSP UMIK-1 ($100 or so when shipped)

DSP is MiniDSP OpenDRC-DI - $325 + shipping

DRC is AcourateDRC - $80 Euro + VAT if required

I thought it was probably REW -- but I use it on the Mac, so it looks a bit different.

I also have the MiniDSP + UMIK, too.

 

[RayDunzl]

Well, you're all set.

Go measure something and post it.

 

[fas42]

Somewhat incredibly to my antique eyes, this chip turns out to be the 2 x 50W "amplifier" in the 30x Series

View attachment 4118

STA350BW

http://rdimitrov.twistedsanity.net/blog/show.php?entry=JBL LSR305 Teardown and Analysis

The chip shows borderline acceptable distortion figures, by audiophile standards - and they're not game to show figures for any frequency above 1kHz! I can't complain, because the class AB chip amp in my lowly Philips HT box showed poor figures too - yet delivered impressive subjective performance at times. However, may be the cause of the fizziness, in this case ...

 

[Sal1950]

Somewhat incredibly to my antique eyes, this chip turns out to be the 2 x 50W "amplifier" in the 30x Series

View attachment 4118

STA350BW

http://rdimitrov.twistedsanity.net/blog/show.php?entry=JBL LSR305 Teardown and Analysis

I find it interesting how much "scrutinizing" is being done on such a inexpensive product.
Kind of shakes the timbers of the High End

 

[Sal1950]

I also have the MiniDSP + UMIK, too.

Well, you're all set.

Go measure something and post it.

I also have the same gear as do many others.
How about doing a tutorial on doing some of these basic measurements you post
Amir did a basic step-up tutorial of REW but the promised followup still await.
http://audiosciencereview.com/forum...om-measurement-tutorial-for-dummies-part-1.4/
I find the REW help files a bit (lot) confusing and hard to follow.

 

[amirm]

Thanks Sal for the reminder. I will try to get that done soon.

 

[RayDunzl]

How about doing a tutorial on doing some of these basic measurements you post

Well, you're all set.

Go measure something and post it.

Start a WTF Am I Doing? thread.

 

[Thomas savage]

Thanks Sal for the reminder. I will try to get that done soon.

Do,or do not..

There is no try.

 

[Sal1950]

Well, you're all set.

Nope, not all set.
Need some guidance.