Hiss on mine is minimal and inaudible from my listening position.
If your bead help, I"ll replicate for sure.
on RTA, mine exhibit peak 15khz (usb mic limit higher than 20khz measurement) Seem like the high frequency garbage is there on mine too.
I read people using ferrite on the tweeter wire to replace the doughnut used by factory. Awaiting delivery...
If your bead help, I"ll replicate for sure.
on RTA, mine exhibit peak 15khz (usb mic limit higher than 20khz measurement) Seem like the high frequency garbage is there on mine too.
I read people using ferrite on the tweeter wire to replace the doughnut used by factory. Awaiting delivery...
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Those ferrite filters on the speaker wires are there for EMI compatibility to pass FCC(and other similar) regulations. Basically so it does not interfere with AM radios.
It is unlikely they will help with the hiss. I'm pretty sure the hiss is caused by the STA350BW itself. I saw other people suggesting it is caused by switching frequency leaking into the ADC input, but that seems unlikely as well. Something fishy is going on with the 384kHz carrier. Initially I thought it is the AM spread spectrum feature of the chip, but in this "noisy" mode the 384kHz spike is even higher, and with proper spread spectrum all spikes should be much lower and broader.
It is unlikely they will help with the hiss. I'm pretty sure the hiss is caused by the STA350BW itself. I saw other people suggesting it is caused by switching frequency leaking into the ADC input, but that seems unlikely as well. Something fishy is going on with the 384kHz carrier. Initially I thought it is the AM spread spectrum feature of the chip, but in this "noisy" mode the 384kHz spike is even higher, and with proper spread spectrum all spikes should be much lower and broader.
Ok those ferrite beads on the PLL filter power supply lines had exactly zero effect on hiss.
Though PLL filter power now is super clean. No digital noise, just some 15mv 200khz sine waveform. Can be reduced to about 2-3mv with a 2.2uf cap in parallel, but also have no effect on the hiss.
So my only remaining theory now is that the STM8 MCU writes something to the STA350BW's registers that causes it to behave that way.
I don't have a proper logic analyzer to dump the I2C traffic from the MCU to the amplifier chip.
Could the that spread spectrum thingy I mentioned. It does seem to reduce the spikes in the > 1MHz range. Though I couldn't care less about EMI compatibility. I'd much rather it not hiss.
Though PLL filter power now is super clean. No digital noise, just some 15mv 200khz sine waveform. Can be reduced to about 2-3mv with a 2.2uf cap in parallel, but also have no effect on the hiss.
So my only remaining theory now is that the STM8 MCU writes something to the STA350BW's registers that causes it to behave that way.
I don't have a proper logic analyzer to dump the I2C traffic from the MCU to the amplifier chip.
Could the that spread spectrum thingy I mentioned. It does seem to reduce the spikes in the > 1MHz range. Though I couldn't care less about EMI compatibility. I'd much rather it not hiss.
I was very suspicious of wasting my time but ~$10 for trying a mod that was claimed to be great was a risk I was willing to take. 
Hate to say but the Amazon "snake oil" guy was right.
I've installed 4x ferrite per speaker (as he described) and compared the sound.
I did one speaker at first and listened in mono, result were definitively better on the "treated one". Like his subjective description, sound was fuller, less edgy and treble sounded more precise (very small improvement on treble but one still). I haven't noticed any drawback at all, it is just better.
Not sure on distortion reduction claim, haven't measured it and I but don't think it would change anything on that area.
Measured hiss and it is exactly the same as before on both tweeter and woofer so the noise remain identical.
When I've done the 2nd speaker with the same mod, I redid my comparison test to make sure they both sounded identical. They did. Both improved to the same degree.
I couldn't stop scratching my head as of what it exactly does cause the subjective improvement is REAL.
Here some pic on my site for the visual people
JBL 306P active monitor impression and mods
Try it.
Hate to say but the Amazon "snake oil" guy was right.
I've installed 4x ferrite per speaker (as he described) and compared the sound.
I did one speaker at first and listened in mono, result were definitively better on the "treated one". Like his subjective description, sound was fuller, less edgy and treble sounded more precise (very small improvement on treble but one still). I haven't noticed any drawback at all, it is just better.
Not sure on distortion reduction claim, haven't measured it and I but don't think it would change anything on that area.
Measured hiss and it is exactly the same as before on both tweeter and woofer so the noise remain identical.
When I've done the 2nd speaker with the same mod, I redid my comparison test to make sure they both sounded identical. They did. Both improved to the same degree.
I couldn't stop scratching my head as of what it exactly does cause the subjective improvement is REAL.
Here some pic on my site for the visual people
JBL 306P active monitor impression and mods
Try it.
Je, talking about ferrites, I have Würth 150 kHz 8 mm ferrite in my KEF Q100 5.25" coaxial speakers. Only in the woofer -> more bass and cleaner/faster. If tweeter too, then I had "V" sound, I do not like it.
Old picture
And YES, the HF sounds better with the cheap NOS polystyrene bypass. Softer, less aggressive.
It was trial and error. Years ago I asked here and nobody could give me an explanation!
Old picture
An externally hosted image should be here but it was not working when we last tested it.
And YES, the HF sounds better with the cheap NOS polystyrene bypass. Softer, less aggressive.
It was trial and error. Years ago I asked here and nobody could give me an explanation!
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Not sure if i get this right, but the JBL example seems to add ferrites to the output of a class D amp, which by definition contains lots and lots of HF garbage. Ok, it is not audible on its own but it certainly finds ways of entering upstream components. So the ferrites cut the garbage down a bit...does not seem so strange.
What would be interesting is repeating the experiment using a linear and preferably zero nfb amp.
What would be interesting is repeating the experiment using a linear and preferably zero nfb amp.
I'm not sure of the resulting inductance from 1 turn in the ferrite, I do not have precision measurement to confirm value.
As Analog_sa mention, the JBL amp is class D and HF garbage certainty make it's way to the driver voice coil. maybe not enough to saturate them but enough to be audible once you filter some of it out.
Maybe I could bring one at work to test it out.
Maty; another tweak, replace that 0.68ohm by a mill (or equivalent) no-inductive resistor.
5watts is probably overkill, 2-3 watts would do just as fine
Later
this resistor is in line with the tweeter for sure
As Analog_sa mention, the JBL amp is class D and HF garbage certainty make it's way to the driver voice coil. maybe not enough to saturate them but enough to be audible once you filter some of it out.
Maybe I could bring one at work to test it out.
Maty; another tweak, replace that 0.68ohm by a mill (or equivalent) no-inductive resistor.
5watts is probably overkill, 2-3 watts would do just as fine
Later
this resistor is in line with the tweeter for sure
I'm not of a DIYer because I don't have much space and time. I only recently found this thread. I have the MKII. I wasn't crazy much about the woom, woom of the loose bass (at louder volumes) so I took it apart and wedged two dowels, side-to-side and one top-to-bottom. I also added some nondrying clay (less than a pound for the pair) to the woofer baskets, "outside" the port tube and a bit on the inside of the metal plate holding the amp.
The biggest weakness on these speakers is clearly the thin, weak enclosure.
Highly recommended! It sounds SO much better in the bass!
The biggest weakness on these speakers is clearly the thin, weak enclosure.
Highly recommended! It sounds SO much better in the bass!
@etalon90
I had thought of "improving" the components, spending a lot more money but the result was so accommodating that it stayed that way.
Another option is the new filter proposed by Zvu, but for now I want to enjoy the excellent sound that I have.
KEF LS50 playground - measurements of raw drivers in factory cabinets and simulations
For me the most important thing is to enjoy the great recordings that I usually listen to.
BTW, a substantial improvement (end Summer'18) is to add mass to the furniture. Now my Q100 weigh more than LS50.
I had thought of "improving" the components, spending a lot more money but the result was so accommodating that it stayed that way.
An externally hosted image should be here but it was not working when we last tested it.
Another option is the new filter proposed by Zvu, but for now I want to enjoy the excellent sound that I have.
KEF LS50 playground - measurements of raw drivers in factory cabinets and simulations
For me the most important thing is to enjoy the great recordings that I usually listen to.
BTW, a substantial improvement (end Summer'18) is to add mass to the furniture. Now my Q100 weigh more than LS50.
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measured the resulting inductance
1.1uh (at 1khz)
Given I have 1 per wire, the driver effectively see 2 in series so the total added inductance is 2.2uh
on 7.4ohm (tweeter RE), that result in a 535khz low pass
on the woofer (4ohm), that result in a 289khz low pass.
GIven the switching frequency of the class D amplifier used in those JBL is at 384khz, I'll order 4 more ferrite and add them on the tweeter so my F3 fall below the 384khz carrier.
(I can't do 2 or 3 turn in the existing ferrite because the hole is too small to accomodate that.)
Will report.
1.1uh (at 1khz)
Given I have 1 per wire, the driver effectively see 2 in series so the total added inductance is 2.2uh
on 7.4ohm (tweeter RE), that result in a 535khz low pass
on the woofer (4ohm), that result in a 289khz low pass.
GIven the switching frequency of the class D amplifier used in those JBL is at 384khz, I'll order 4 more ferrite and add them on the tweeter so my F3 fall below the 384khz carrier.
(I can't do 2 or 3 turn in the existing ferrite because the hole is too small to accomodate that.)
Will report.
Finally put more turn on the tweeter ferrite bead.
Added 1 ferrite bead and did 1 turn and did 1 extra turn on the existing ones.
Each tweeter now has 3 beads (2 with 2 turn and one with one turn)
Resulting inductance is 4.2uh (all bead are indeed in serial)
calculated low pass for the tweeter (7.4ohm impedance) is 300khz, I wanted to match as close as possible the 280khz obtained on the woofers (Class D amplifier on those JBL has a carrier frequency of ~380khz).
I'm fully aware that DIYaudio Forum ain't very entertaining of subjective appreciation but like the initial ferrite mod, sound improved even more. In same lines as initial mod.
Won't write a text on it but bottom line is that it is definitively better (after several AB comparison)
YMMV
Added 1 ferrite bead and did 1 turn and did 1 extra turn on the existing ones.
Each tweeter now has 3 beads (2 with 2 turn and one with one turn)
Resulting inductance is 4.2uh (all bead are indeed in serial)
calculated low pass for the tweeter (7.4ohm impedance) is 300khz, I wanted to match as close as possible the 280khz obtained on the woofers (Class D amplifier on those JBL has a carrier frequency of ~380khz).
I'm fully aware that DIYaudio Forum ain't very entertaining of subjective appreciation but like the initial ferrite mod, sound improved even more. In same lines as initial mod.
Won't write a text on it but bottom line is that it is definitively better (after several AB comparison)
YMMV
Hi people, my name is Diego, I'm from Uruguay, I wish to know what is that if someone knows, mine is erased. Thanks!
An externally hosted image should be here but it was not working when we last tested it.
Can someone tell me what's that? mine id is removed, thanks!
An externally hosted image should be here but it was not working when we last tested it.