Presonus Eris Sub 8BT pass-through and HPF measurements

[roladyzator]

The Sub 8BT's standout feature amongst cheap subwoofers is a build-in high-pass filter, so it's very easy to off-load smaller monitors and reduce the interaction between the sub the and the small woofers.

I've decided to measure how the pass-through affects the line level audio signal, out of curiosity.
In case this is important to someone as a part of their purchasing decision, I'm sharing the results here.

Setup:

• Source: Shanling M0 portable DAP. It has a 2V RMS output and is based off of an ESS DAC. Amir has measured its successor - M0 Pro.
• ADC: The built-in ADC in a Creative Sound Blaster GC7's Line-In
• Source is connected to RCA inputs on the Sub 8, then Sub 8's RCA outputs are connected to the sound card's Line-In.
• Test is using RMAA test signal, played back using the M0 and recorded using the GC7.
• The reference setup is when M0's headphone output is connected directly to GC7's line-in.

Frequency response:
There is a slight treble roll-off (-0.5 dB at 20 kHz) and even slighter bass roll-off (0.2 dB at 20 Hz)

THD + noise:
I've measured a significant increase in the noise floor.
I'm surprised to see some peaks at 60 Hz, given that I live in Poland where the power grid is 50 Hz.

IMD

High-pass filter
Company states it's a 12dB / octave high pass filter with cutoff frequency at 80 Hz.
I've measured this one using REW's RTA, so some the jaggedness there wouldn't show up in a typical sweep measurements.
I'm too lazy to re-do this one, though.

It looks like it delivers on the promise and doesn't affect anything above 200 Hz or so.

My thoughts:
The HPF works as expected, but the pass-through itself is quite noisy, so perhaps not the best idea for using with monitors with high gain.
With my Edifier MR4's, I did not find the noise disturbing.
I've recently upgraded to Kali IN-8 V2 and on my desk they still benefit from the sub.
I've done some MMM measurements using a dayton iMMM-6 microphone.
I don't trust the treble measurements too much with this one, but it's good enough to evaluate bass in my opinion.

I'm not hearing any hiss from them at my listening position (85 cm and more), but I'm tempted to use a 3.5mm jack splitter from my source and feed the sub and IN-8 V2 separately, so that I have a cleaner signal to the IN-8. However, before spending any more money, I think it's worth experimenting with placement and sub low pass frequency and improve the things a bit.

What do you guys think? Is this deal-breaking performance, or something to expect at this price range?

 

[komhst]

What do you guys think? Is this deal-breaking performance, or something to expect at this price range?

I think, considering its price, is an OK product.

 

[Berwhale]

I use the older, non-BT, version of the Sub8 with my iLoud MTMs (also older version). I can't say I noticed any increase in noise from the MTMs when I added the Sub8 in-line, although that was several years ago. The MTMs have their own high-pass filter which is implemented in DSP, so I could drive the Sub8 and MTMs separately - I might consider this as it would reduce the cabling under my standing desk.

 

[roladyzator]

I also don't think I'm hearing any noise or hiss from the sub line outputs. I suppose it's just buried within the ambient noise.