OP
- Thread Starter
- #61
My measurement setup:
REW -> laptop soundcard -> LPF -> amplifier -> passive sub -> UMIC-1 -> USB of the laptop -> REW
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Help with my faulty 12" subwoofer design
- Thread starter Yevhen
- Start date
REW -> laptop soundcard -> LPF -> amplifier -> passive sub -> UMIC-1 -> USB of the laptop -> REW
Perhaps you can try with a different laptop or an external USB sound card or something.
OP
- Thread Starter
- #63
Can I analyze those sweeps with REW? Or maybe better borrow USB DAC...
What a strange setup.
DanielT
Major Contributor
Make a flow chart. Write down all and what components you use in the flow. Hardware and software.
Then problem solving to exclude part by part, component by component.
Plus how and where you measure. What it looks like physically.
In short, everything you come up with
It can usually help if you get an overview. It also helps other knowledgeable people who can then help you more easily then.
.
Publish your complete schedule here in the thread for help.Really make sure to include everything in the flow chart.
Then systematically step by step. Attached image example in electronics, but the principle, the way to go about it is general.
Then problem solving to exclude part by part, component by component.
Plus how and where you measure. What it looks like physically.
In short, everything you come up with
It can usually help if you get an overview. It also helps other knowledgeable people who can then help you more easily then.
.Publish your complete schedule here in the thread for help.Really make sure to include everything in the flow chart.
Then systematically step by step. Attached image example in electronics, but the principle, the way to go about it is general.
Attachments
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OP
- Thread Starter
- #66
Here is my in-room response (Left speaker + sub, mic pointed at the speaker at 0.5m distance, 1/12 oct smoothing)
Still need to kill room mode at 40Hz (coming from the speaker in the corner of the room). Fortunately, sub is placed in the middle of the long wall and does not ignite that 40Hz mode.
Still need to kill room mode at 40Hz (coming from the speaker in the corner of the room). Fortunately, sub is placed in the middle of the long wall and does not ignite that 40Hz mode.
OP
- Thread Starter
- #67
why strange? It's my home office. Normally I use the company laptop only for work and stream music via Chromecast.Why a lpf for a sealed sub for starters? Meant not the measurement setup, but your basic setup. Are you using REW to implement the lpf or ?
ps nm to an extent, had hpf on the brain for the sealed sub. Still was more curious about specific hardware in the basic setup.
OP
- Thread Starter
- #69
Ah, no, I've built a hardware LPF (resistors and capacitors, 3rd order) to cut everything after 40-60Hz
Run RTA and enable show distortion
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Well if it was clipping the sub, then that would explain a lot.
You might want to try more sub amp gain, and lower the signal on the preamp side?
The plot look like it should be sounding good if the output is enough now?
Are you done? Or is it still lacking?
Why? Seems an electronic crossover with your speakers would be the better route.
In the OP’s defence though, he has found a solution that helps to understand where the problem might be occurring.
I doubt we would have gotten there digitally, if my premise of (digital) clipping is the cause.
So I think he is onto a decent path here.
Maybe. We'll see. Just seems kinda goofy and not ideal to start with.
If he didn't implement an LPF (analog or digital), it wouldn't be a sub.
Low pass filters filter out the high frequencies and let the low frequencies through.
Yes, with speakers, sure. For just measurement of the build?If he didn't implement an LPF (analog or digital), it wouldn't be a sub.
Low pass filters filter out the high frequencies and let the low frequencies through.
OP
- Thread Starter
- #77
Hi guys, mystery solved. Just got an external USB DAC to bypass audio out from my laptop:
REW-> USB DAC on ES9038PRO -> wideband amplifier (no LPF) -> passive sub -> UMIC-1 -> USB -> REW
Check out the curves. 3rd harmonic below 1%!!! and still without LPF.
REW-> USB DAC on ES9038PRO -> wideband amplifier (no LPF) -> passive sub -> UMIC-1 -> USB -> REW
Check out the curves. 3rd harmonic below 1%!!! and still without LPF.
OP
- Thread Starter
- #78
Thanks a lot for your help, I was just about to give up and return the driver.
OP
- Thread Starter
- #79
The next step in my home office project:
1. Make a box for sub LPF + amplifier. I'll use 600W PA from Aliexpress:
It does have a built-in band-pass filter 30-100Hz but no adjustments. I have already bypassed their filter and added my simple 3rd order LPF, also planned to add a roll-off freq control.
2. Cut low freq extension for my floorstanders. Currently, they play from 30-40Hz and trigger that 40Hz room mode. I wanted to reduce the internal volume (more absorber) of the speakers and leave the low freq range for my new sub (placed in the middle of the room, doesn't trigger room mode). If that doesn't help, I may try a high-pass or notch 40Hz hardware filter in front of the power amplifier.
1. Make a box for sub LPF + amplifier. I'll use 600W PA from Aliexpress:
It does have a built-in band-pass filter 30-100Hz but no adjustments. I have already bypassed their filter and added my simple 3rd order LPF, also planned to add a roll-off freq control.
2. Cut low freq extension for my floorstanders. Currently, they play from 30-40Hz and trigger that 40Hz room mode. I wanted to reduce the internal volume (more absorber) of the speakers and leave the low freq range for my new sub (placed in the middle of the room, doesn't trigger room mode). If that doesn't help, I may try a high-pass or notch 40Hz hardware filter in front of the power amplifier.
