JBL 104 absolute volume

[yewneek]

I got a pair of JBL 104 today, and set them up via TRS with an Audiobox GO. Windows 11, USB-A to USB-C, playing FLAC thru MusicBee, also via other music apps.

Also tested with RCA to confirm volume.

It would appear: the volume control is at FSD on the speakers, and the dial on the AudioboxGo is FSD and the volume control in W11 system tray is set to 100%. With an arbitrary Sound Analyzer App using the Samsung S22+, confirmed with another Samsung phone with the same software, the JBL 104 speakers top out at around 77dB at 70cm equal distance.

Tested with: King Crimson, Jimi Hendrix, Pachelbel

The peak SPL is 92dB from the JBL website literature, and 77dB from what would ostensibly be 30W from a class D amplifier, is, basically disappointing.
https://jblpro.com/en/site_elements/jbl-professional-104-spec-sheet
That's effectively giving 1W output. I can measure the actual output at the wire with a DSR and ammeter while playing a 1kHz test tone, and white noise.

Assuming: 1 Watt=77dB, then a 3dB rise for each doubling of power, gives another ~5*3dB=>77dB+15dB=92dB total.

The speakers are certainly clear and a good quality c/w my Sony MDR-V6 headphones, so no complaints there.

Am I doing anything wrong? I read the reviews here a few times.

Cheers

GB

 

[staticV3]

Your audio interface might be outputting too low of a voltage to get the JBL to play at full volume.
Unfortunately, neither Presonus' website, nor their manual for the Audiobox Go says how much voltage the Line out can output.

Try unplugging the JBL, but leave the TRS cables plugged into the interface. Then use REW to generate a 60Hz sine wave test tone at -0dBFS amplitude. Save it as .wav, play it back on your PC, and use the multimeter to measure the AC voltage between Tip and Ring on the other end of the cable.

Also, make sure that the JBL 104 input is set to -10dBV.

 

[yewneek]

Ok thanks. Will try it.

Not sure if you realsied I tried the RCA straight from the computer as well as TRS, but this gave an identical volume on FSD too.

How do I set the JBL 104 input to -10dBV? I have some knobs and dials on the audio interace and the speaker but no level.

 

[DVDdoug]

I found the user manual online. In the Troubleshooting section it says the RCA inputs are -10dBV and the XLR inputs are +4dBu for "professional equipment".

 

[yewneek]

Ordered a Focusrite Scarlet Solo with known output levels, will compare side by side. Will also update when I've done the audio test as advised.

If someone just made a cheap pro-level DAC with damned volume knob. I love a good knob I can grab at the desk while I work.

 

[yewneek]

2.67Vrms 60Hz and 1kHz confirmed. AudioBox Go TRS output at FSD.
Power use at 60Hz peaks at 45Watts thru JBL 104 full scale deflection.
Power use at 1kHz on JBL 104 FSD is approx 30 watts.

Sorry about the large pics, and I know my skirting boards need a dust.

 

[yewneek]

20-20kHz sweep tone 0dBfs. Arbitrary measurement of SPL peak of around 90dB at maybe 70cm equidistance from JBL 104 and AudioBox Go at FSD.

 

[staticV3]

If I understand JBL's specs correctly, you get 88dB with -10dBV in via RCA or +4dBu in via TRS, and to get max output of 104dB, you then need to add 16dB to the inputs (reflected in the "Maximum Peak Input Level" numbers).


Ergo, to max out the JBL 104, you need to input +6dBV (=2Vrms) via RCA, or +20.3dBu via TRS (=8Vrms).

That would explain why it was so quiet with the AudioBox Go. 2.67V in via TRS will drive the JBL to only 50% of its rated max volume.

You said you ordered a Scarlett Solo as replacement? It can output 15.5dBu max via TRS.
That'll give you 40% more volume than your AudioBox Go, but it'll still be short of driving the JBL to its limit at 70% of max volume.
Basically:


If this all is correct, then it's really strange to me why JBL would choose such a low gain using TRS in.

 

[yewneek]

Working on the absolute numbers is what I can provide as evidence. Doubling the power from 45watts measured to 90watts will give a theoretical 3dB rise, so the claimed current draw of 86watts will only give outpout to 80dB SPL at 70cm, if it follows with the first post I made here.

Time will tell, and it's so easy to do this with what we have to hand I'm surprised it's not more readily available in manuals, even for low end prosumer stuff.

 

[staticV3]

@yewneek instead of driving the 104 with TRS to TRS cables, you could try using TS to RCA cables.
If the specs say what I think they say, then you'll have a much easier time driving the 104 to its max that way, as you'll only need 2Vrms instead of 8.

 

[yewneek]

The TRS is balanced, RCA isn't. Not sure if a cable exists to convert it. Or, what the technical stuff says.

 

[staticV3]

The TRS is balanced, RCA isn't. Not sure if a cable exists to convert it.

Most TRS Bal Line outs can be used as TS SE out as well. Here are some cables: https://www.thomann.de/de/cordial_cfu_15_pc.htm

 

[yewneek]

So that grounds the cold and only uses half the waveform on the hot? Yikes! Doesn't sound ideal!

 

[staticV3]

So that grounds the cold and only uses half the waveform on the hot? Yikes! Doesn't sound ideal!

True. The obvious solution would be to use native SE outputs, as the 104 has much higher gain with SE in.

Edit: and yeah, instead of shorting Cold to GND with TS plugs, it'd be a better idea to use TRS plugs with the sleeve just left disconnected.

 

[yewneek]

Sounds suboptimal! Worth exploring but I'm not the one to solder cables if I can just swap the audio interface!

I actually like the form factor of the AudioBox Go, it's small, got a big voume knob and independent headphone output.

Much as with the JBL 104 BT, I was very close to sending them back when I discovered there was a startup sound of guitar strummed, but I realised they could just be left on. Normally, the EU-required standby power-down would be disabled but it doesn't seem to be an issue.

I also quite like the white colour!

I have just ordered a JBL 104 3D printed stand for each of them from Thingiverse. It will add an 8° upward tilt so they fire more directly toward my ears. Total 12.50GBP for two.


Since I have a Rode VideoMic Go II, I emailed Rode for the calibration and test data for the product, so that I can start testing and have a reliable source.

View of the desk below, cropped for privacy.

 

[yewneek]

Focusrite Scarlet Solo 3rd Gen arrived earlier today. Now tested on 60Hz output 0dBfs wav file with updated drivers. Result is 4.75Vrms output.

Power use on 20-20kHz sweep tone to follow. Also SPL on FSD wil be compared and updated.

 

[staticV3]

Feeding 4.75V into the JBL's TRS input will still leave you about 30% short of the Max rated volume.
You could make a cable that only feeds Hot and GND into the JBL's RCA inputs.
That'll leave you with 2.4V. With RCA in, 2V is enough to get the max rated output.

How's the volume with the Scarlett? Is it loud enough for you?

 

[RayDunzl]

2.67Vrms 60Hz and 1kHz confirmed

Is the 2.68V on the meter unconfirmed?

 

[yewneek]

Is the 2.68V on the meter unconfirmed?

The meter isn't calibrated. It's in agreement with another multimeter I've got so I would think it's pretty accurate for a muggle like me.

I tested the voltage at 60Hz as advised, and also at 1kHz to provide confirmation that the result was good at a test frequency commonly used. 60Hz is more energetic aka more demanding on speakers/power supplies while in the F3 or F6 range of speakers.

My use of commas, sometimes, is lacking.

 

[yewneek]

Sound analyzer app gives quite a good result, (so assume + or - 3dB) 96dB @ 1kHz Full Scale Deflection on Focusrite Scarlett Solo 3rd Gen into JBL 104 BT on balanced inputs.

I am aware the measurement isn't ideal, but the conditions were pretty standardised at 70cm from speaker, equidistant, repeated from before. The app/equipment should be reasonably linear and reliable, and repeatable. I used TWO Samsung phones with the same app to verify as much as possible.
Samsung A18 and Samsung S22+.
Blurry images are shots of the A18 screen. Screengrabs are from the S22+

Power use at 60Hz was again, higher than at 1kHz, 43watts used FSD, but the absolute volume measured lower(4th photo) showing in the high 80's dB for 60Hz.
Maybe it was the microphone being obscured while I held it, sensitivity of the mobiles. Not sure.

JBL104 BT uses 27 Watts used on 1kHz sine giving [unverified] 96dB SPL at 70cm, both speakers driven. UK mains at 240VAC. Input of 4.75Vrms from Focusrite Scarlett Solo 3rd Gen.

The important result is that the absoute SPL/volume DOES increase when using balanced inputs with a higher input voltage.

I got what I wanted, more LOUDER. Yes!

I hope this helps anyone wondering the best way to get max volume from half decent desktop speakers on a budget.

The white is really lovely, and they're going cheap on Amazon UK right now for 139GBP

Thanks for your views, help, input.

GB


Pic. 1: Samsung A18 measuring 1kHz showing SPL
Pic. 2: Samsung A18 measuring frequency spread and SPL
Pic. 3: SamsungS22+ measuring 1kHz showing SPL to confirm A18 measurement.
Pic.4: Samsung S22+measuring 60Hz showing SPL with same output as 1kHz, indicating lower output or lower sensitivity of microphones, or speakers, or both.
Pic.5: Power use at 60Hz FSD(no change from using lower input voltage on balanced TRS from different audio interface)
Pic.6: Power use at 1kHz FSD(no change from using lower input voltage on balanced TRS from different audio interface)