Even then i want to strap it to the side of the fireplace! Or hug and sit on it forever! Its never enough. Its so hard!
I kind of addressed muliple ideas in one response. Ironically how a response in a speaker has 3 points as well (lol)?
I think i cn waste time trying to get 2.0xpi and the mic just right to play the dog and pony show of amateur hobbyist or i can just use it as a tool to compare what my ears might sense has changed.
No more sweeps... thats all i gotta say. (I only mean this in the adventure to seek out and hear new or change in your own or adaptations of others ) as Thats getting nobody know here and fast. Manually playing with the variety of tones at the touch of a slider is a far more interesting and plotable (by hand )
Look and find real and even musical results and difficulties and thus troubles or cures.
I dont sweep suspension parts and expect to set the bump stops.. thats reality. Its momentum. Its broken parts if not. Including me
But what about sag? Thats not a sweep either.. or antisquat? these are instant center upon accelerating?. Or braking.. and roll axis in a corner? Never a sweep or cycle of random coverage of gently everything. Not even remotely
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I kind of addressed muliple ideas in one response. Ironically how a response in a speaker has 3 points as well (lol)?
I think i cn waste time trying to get 2.0xpi and the mic just right to play the dog and pony show of amateur hobbyist or i can just use it as a tool to compare what my ears might sense has changed.
No more sweeps... thats all i gotta say. (I only mean this in the adventure to seek out and hear new or change in your own or adaptations of others ) as Thats getting nobody know here and fast. Manually playing with the variety of tones at the touch of a slider is a far more interesting and plotable (by hand )
Look and find real and even musical results and difficulties and thus troubles or cures.
I dont sweep suspension parts and expect to set the bump stops.. thats reality. Its momentum.
We're talking about cab vibrations and distortion, not just bass output.
Attached are FR when I stood in three locations around my room. Quick and dirty. Just one of my subs playing. 130 Hz XO. If differences of this size showed up after adding bracing or other changes, I think they would merit our interest. 1/12 smoothing (wilder differences with 1/24).
FYI included is distortion. -50dB - quite nice for a cheap driver, eh. But played real quiet, late at night here.
B.
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Wheres the first three harmonic nodes at in your room? I dont understand this at all^^^^ Think about the areas that are standing waves and then what that means to 20 hz and 30 or 60 and 90? And in between. You just swapped out positions by a division of 1.5:1 in the room. Ie (one node centered and two nodes as 3rds of the room in 2 places).
...and how many times did you repeat the measurements to confirm their veracity?
In any case. the differences below 80 Hz, i.e. subwoofer territory are minimal to non-existent. If I ran my subwoofer up to 1kHz, I might be a little more concerned at how the position of my body in the room changed its response
Oh... i see, i wasnt thinking ‘we’ were moving or that ‘we’ were a reference/size/length.. im backwards..
Frankly, I don't re-run FR curves, like you are suggesting, because you'd need a magnifying glass to see the difference..... unless you moved the mic a few inches. Or, when the levels are quite low (on the right tail end of my plots) or with THD where ambient noise intrudes.
Details of THD curves - which can be 50dB below the fundamental - do vary all the time depending on the A/C in your house, street traffic, railroad trains a mile away, etc.
In the case of sitting on the sub, the wall vibrations might be in that -50dB range and so body location can have an influence on results from cab in various ways.
Attached are re-runs at about the same loudness as last night. Ooops, was that a garbage truck passing by?
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Which is exactly why you repeat these measurements until you get a consistent enough result. Or just average them in REW.
Off topic but apropos previous post, but to restore the honour of my cheap-driver sub previously shown with poor bass using just the laptop mic, here're listening chair runs with good mic. First, re-runs FR (really great bass) and then re-runs THD (really low, eh... but something in room is shaking at 65 Hz).
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Laptop mic. In the room.
Um, ok then.
And yes, averaging measurements is a well-known principle to reduce the impact of any errant noise on the results. In REW, you can do this by simply choosing to run 2, 4 or 8 sweeps for the measurement (More=better).
BTW, for THD, I found it more helpful to plot in terms of % relative to the fundamental, like the attached (a 10" bandpass design driven at peak design voltage). I used those results to choose the best HP filter for the build.
Um, ok then
.And yes, averaging measurements is a well-known principle to reduce the impact of any errant noise on the results. In REW, you can do this by simply choosing to run 2, 4 or 8 sweeps for the measurement (More=better).
BTW, for THD, I found it more helpful to plot in terms of % relative to the fundamental, like the attached (a 10" bandpass design driven at peak design voltage). I used those results to choose the best HP filter for the build.
Attachments
back on topic
Right so I've rebuilt the sub and taken some measurements.
This is the old inadequate bracing. Yes I know it looks ridiculous. I built my first speakers 30 years ago but in my defense I am out of practice and had never built a sub before.
This is how I've rebuilt it. I've adjusted the internal dimensions to allow for the volume of the bracing, so it is 5cm taller than last time. I also made the slot deeper so the drivers can be removed without tearing the speaker apart. I made the braces by cutting the xps foam with a temp controlled soldering iron which worked very well.
I started off using Gorilla Glue, but went back to the trust Sticks Like Sh*t Turbo as I didn't need to clamp most of the joints and it also makes an airtight seal.
1. Did the bracing improve thd? yes.
Here is THD for the old sub. That crazy resonance just under 90hz measures about 90% thd
Putting the heavy weight on top definitely improved things, bringing that resonance down to about 7%
But proper bracing is a better solution. Even the crazy resonance is down to 3% without thd below 1% for most of the useful range
2. Did the bracing affect frequency response?
Some useful dbs around 100hz but most of the rest of the response is similar. The volume increase might be due to a change in the volume dial. I didn't match output voltages.
3. Do the two drivers actually cancel each other's distortion?
I was surprised how well they cancelled the distortion. PP gives a profound improvement in thd, from 2-5% through most of the range to <1%, and at that resonance peak from 10% thd with single drivers to 3% with boh. I ran the sweep on the push driver, then the pull driver, then both again to check consistency with the measurements above.
4. Is the frequency response consistent between measurements?
I wasn't excited about this but some other people were. It is consistent above 18hz - not sure what is happening below that but the sub output was very low in this region and could be affected by background noise
I also took the distortion measurements 3 times but didn't bother averaging as they looked very similar.
5. Does the person moving in the room affect frequency response?
I think we knew this one too. It does a bit. Room is 2.3mx2.2mx3.2m. I sat on the floor, stood up, then sat on the sofa. Close but not identical responses.
Right so I've rebuilt the sub and taken some measurements.
This is the old inadequate bracing. Yes I know it looks ridiculous. I built my first speakers 30 years ago but in my defense I am out of practice and had never built a sub before.
This is how I've rebuilt it. I've adjusted the internal dimensions to allow for the volume of the bracing, so it is 5cm taller than last time. I also made the slot deeper so the drivers can be removed without tearing the speaker apart. I made the braces by cutting the xps foam with a temp controlled soldering iron which worked very well.
I started off using Gorilla Glue, but went back to the trust Sticks Like Sh*t Turbo as I didn't need to clamp most of the joints and it also makes an airtight seal.
1. Did the bracing improve thd? yes.
Here is THD for the old sub. That crazy resonance just under 90hz measures about 90% thd
Putting the heavy weight on top definitely improved things, bringing that resonance down to about 7%
But proper bracing is a better solution. Even the crazy resonance is down to 3% without thd below 1% for most of the useful range
2. Did the bracing affect frequency response?
Some useful dbs around 100hz but most of the rest of the response is similar. The volume increase might be due to a change in the volume dial. I didn't match output voltages.
3. Do the two drivers actually cancel each other's distortion?
I was surprised how well they cancelled the distortion. PP gives a profound improvement in thd, from 2-5% through most of the range to <1%, and at that resonance peak from 10% thd with single drivers to 3% with boh. I ran the sweep on the push driver, then the pull driver, then both again to check consistency with the measurements above.
4. Is the frequency response consistent between measurements?
I wasn't excited about this but some other people were. It is consistent above 18hz - not sure what is happening below that but the sub output was very low in this region and could be affected by background noise
I also took the distortion measurements 3 times but didn't bother averaging as they looked very similar.
5. Does the person moving in the room affect frequency response?
I think we knew this one too. It does a bit. Room is 2.3mx2.2mx3.2m. I sat on the floor, stood up, then sat on the sofa. Close but not identical responses.
"I've adjusted the internal dimensions to allow for the volume of the bracing, so it is 5cm taller than last time. I also made the slot deeper so the drivers can be removed without tearing the speaker apart."
Does this equate to 2.5cm per chamber?
What is new Depth (width)?
Do you have an updated drawing to help us mentally challenged better understand your changes.
Just a mark up would be great.
Tks.
Does this equate to 2.5cm per chamber?
What is new Depth (width)?
Do you have an updated drawing to help us mentally challenged better understand your changes.
Just a mark up would be great.
Tks.
Here you go. Internal width is 25cm. All dimensions on the layout are in cm.
Bracing was marked in yellow - you could use the photos as a guide or just do your own thing.
View attachment MCM 55-2421 sub v2.pdf
Bracing was marked in yellow - you could use the photos as a guide or just do your own thing.
View attachment MCM 55-2421 sub v2.pdf