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You guys are amazing! How great is it to have a true expert available to consult:D As far as the geek / nerd stuff, yes it IS interesting. That is just an added bonus to the ultimate goal of serious theater use. Yeah, I know, this is JUST a test. But it will be fun far after the testing phase is done.


Collecting empiric data like this ... just wow! Snow and all (as we are having flash flood warnings down in AL today :()
 

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@a77cj7 Do you still need close mic measurement? I don't have it save as measurement file, just the image capture. I can do a close field measurement but it will be in a room though.
 

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Discussion Starter #123
@a77cj7 Do you still need close mic measurement? I don't have it save as measurement file, just the image capture. I can do a close field measurement but it will be in a room though.


Don’t worry about it. I was just curious if the resonance was in the same spot.
Not worth setting up the equipment and taking another measurement.

Chris
 

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Saturday, I quit the sweeps at 38v into mono 4 ohm. I clipped the mic at 2m, and heard what I believed to be driver distress. I later discovered it was the enclosure bouncing on the dolly.

Thanks,
Chris
After reading the statement above and reviewing your pics, you didn't make any ground plane measurements. 2pi equals enclosure on the ground. You might get a perfect overlay with the HR model if you place the enclosure on the ground.
 

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Discussion Starter #125
After reading the statement above and reviewing your pics, you didn't make any ground plane measurements. 2pi equals enclosure on the ground. You might get a perfect overlay with the HR model if you place the enclosure on the ground.

You think the 2” it sits above the ground significantly changes response at bass wavelengths?
I tend to doubt it would make a measurable difference. After all, if I had the box sitting sideways, much of the port and horn mouth would be much farther from the ground. As are the cones in most direct-radiator designs. Yet, those are still ground-plane measurements.

I would generally try it, but snow.

Chris
 

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Don’t worry about it. I was just curious if the resonance was in the same spot.
Not worth setting up the equipment and taking another measurement.

Chris
I believe I have mine saved on laptop. I can send it to you once I get home. Seems like you sont need it anymore though. But let me know if you do.

Sent from my SM-G950U1 using Tapatalk
 

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You think the 2” it sits above the ground significantly changes response at bass wavelengths?
I tend to doubt it would make a measurable difference. After all, if I had the box sitting sideways, much of the port and horn mouth would be much farther from the ground. As are the cones in most direct-radiator designs. Yet, those are still ground-plane measurements.

I would generally try it, but snow.

Chris
I'm quite sure a lot of enclosures are made with wheels are not measured while on their wheels. I do understand the circumstance of snow being on the ground. Still excellent work guy! I love the frequency response. You built a monster for a mancave!
 

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Discussion Starter #128
I believe I have mine saved on laptop. I can send it to you once I get home. Seems like you sont need it anymore though. But let me know if you do.

Sent from my SM-G950U1 using Tapatalk


I’ll take it if you have the file saved. I’m not sure if it means anything, but yay more colorful lines.
I’ll pm you my email address.

Chris
 

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Discussion Starter #129
I'm quite sure a lot of enclosures are made with wheels are not measured while on their wheels. I do understand the circumstance of snow being on the ground. Still excellent work guy! I love the frequency response. You built a monster for a mancave!


I might have a chunk of osb stashed. If I do, I’ll A-B it.
I’m still doubting a noticeable difference.

Yeah, its a bit overkill for a shop sub. But next time jbl’s are $30 I’ll probably pick up 4 more and build a second one. Why? I’ll work on that part...

Chris
 

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LMAO...basshead 4 life!
 

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Discussion Starter #131 (Edited)
In case the burning (hah) question on anyone’s mind is “What’s more fun than ground-plane testing in the snow?”, I now have an answer. Ground plane testing in the snow, in the dark, at 20*. Bonus points for it starting to snow during the first set of sweeps.



I haven’t even looked at the data yet, will work on that once I can feel my fingers again.

I did start out with the concern brought up earlier by @BP1Fanatic. Whether the dolly I had the enclosure on affected the measurement. The result surprised me by being noticeable for part of the range, but wasn’t enough to significantly alter the data.

All the other testing tonight was performed without the dolly. (I certainly wasn’t gonna fight it back on there)

Chris
 

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In case the burning (hah) question on anyone’s mind is “What’s more fun than ground-plane testing in the snow?”, I now have an answer. Ground plane testing in the snow, in the dark, at 20*. Bonus points for it starting to snow during the first set of sweeps.



I haven’t even looked at the data yet, will work on that once I can feel my fingers again.

I did start out with the concern brought up earlier by @BP1Fanatic . Whether the dolly I had the enclosure on affected the measurement. The result surprised me by being noticeable for part of the range, but wasn’t enough to significantly alter the data.

All the other testing tonight was performed without the dolly. (I certainly wasn’t gonna fight it back on there)

Chris

Normally I don't like to quote posts and force the picture to reload twice, but SOMETIMES it is worth it ;) Utterly nuts ... and worse, I get it! About a zillion lifetimes ago (30-something years) I installed a turbo in my driveway during the winter. Had some weather to deal with, but once I got going on it I didn't want to stop.


The frozen ground ought to be good for another dB or 2, rather than soft and fluffy snow (if it ices over).



As this build and testing has progressed, I find myself going back and forth about building one of these. Reason suggests that if I am going to the trouble to build a Dev, install a 21" driver and make the labor worth it. OTOH, something about the silly, inexpensive side of this just makes me smile. 8 drivers, some wood, and a used iNuke could make a lot of noise with minimum expense.


How close are the nearest neighbors? I can't wait until the cops show up to check out the noise complaint, followed in 5 min by the guys in white coats:D
 

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[snip].....


How close are the nearest neighbors? I can't wait until the cops show up to check out the noise complaint, followed in 5 min by the guys in white coats:D
Neighbors.....ppppttt.... I have everything in my SIG in an APARTMENT!!! And it's awesome.....


Juju
 

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Discussion Starter #134
About a zillion lifetimes ago (30-something years) I installed a turbo in my driveway during the winter. Had some weather to deal with, but once I got going on it I didn't want to stop.
I swapped a transmission in a snowy driveway back in college. When we were house shopping, a heatable detached garage was one of my main requirements, so I could work on projects year round.
I ended up with an amazing 30x50 heated shop.
This does not help with ground-plane speaker testing though. There’s always a catch.

As this build and testing has progressed, I find myself going back and forth about building one of these. Reason suggests that if I am going to the trouble to build a Dev, install a 21" driver and make the labor worth it. OTOH, something about the silly, inexpensive side of this just makes me smile. 8 drivers, some wood, and a used iNuke could make a lot of noise with minimum expense.
Owning both, I agree with both sentiments. Once I finish testing and comparing... I probably still won’t have an answer other than “Yes!”


How close are the nearest neighbors? I can't wait until the cops show up to check out the noise complaint, followed in 5 min by the guys in white coats:D

Pretty much straight across the road visible in the pic. Back a few hundred feet. They were shoveling their deck while I was running sweeps yesterday. No complaints yet.

Chris
 

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How you’re not met with torches and pitchforks...

Chris
I invite them over for movie nights.....:D:D:D Also being on the 2nd floor above the supers storage room helps....


Juju
 

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On the topic of experiments, how could a SLAPS or two be worked into a JBL Devastator?

I’d love to see that.

Has anyone ever put a passive radiator at the end of a QWR?

I’m guessing using a SLAPS as the port for the hemholts part of the enclosure would function as predicted.
 

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In case the burning (hah) question on anyone’s mind is “What’s more fun than ground-plane testing in the snow?”, I now have an answer. Ground plane testing in the snow, in the dark, at 20*. Bonus points for it starting to snow during the first set of sweeps.



I haven’t even looked at the data yet, will work on that once I can feel my fingers again.

I did start out with the concern brought up earlier by @BP1Fanatic. Whether the dolly I had the enclosure on affected the measurement. The result surprised me by being noticeable for part of the range, but wasn’t enough to significantly alter the data.

All the other testing tonight was performed without the dolly. (I certainly wasn’t gonna fight it back on there)

Chris


Dude, you’re the man. Seriously!! Thank you for all your hard work! I’ve really enjoyed reading this thread. Still don’t understand most of it

But! I have enjoyed it. And, I may have to build one or two of these bad boys to go with the horns I have now.

- Mike
 
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Discussion Starter #140
I used the advice from Josh, @Ricci, earlier today and performed another set of sweeps in each driver/amplifier configuration.

The box was set up in series/parallel mono, so I started there. I dragged all the gear back into the driveway again, and got it hooked up. Mic is set at 4m again.


I used the multimeter and a 60hz sinewave to set the amp at 100w for a baseline. Using 4ohm nominal impedance, that is 20v.


I ran a set of sweeps, ending at 1000w, the rating of the amp.
Voltages are recorded from DMM, wattages are calculated using the 100w baseline and the change in dB.
Ex. First sweep is -9db, 12.5w.

I checked the data by calculating the wattage using the recorded voltage. They all check within reasonable error.

Next, I popped the hatch and set it up for parallel 2ohm 2 channel operation.


I once again used the multimeter and 60hz test tone to set the baseline of 100w. In this case, I needed 50w into 2ohm per channel. This calculates to 10v.


I performed another set of sweeps, stopping at 1000w. Voltage was recorded from dmm on one channel, wattage is total calculated.

These don’t look nearly as pretty as the series/parallel, not sure what is going on.

Lets compare the 1000w sweeps from each set, and see how they match up.

Well, thats not good.

Now, let’s add in the models on 1000w.

This isn’t getting better.

The more I try to remove variables, the farther off my results are, lol. This is getting frustrating.

I do realize that I made an oversight during the parallel 2ch measurements. I intended to swap the dmm to the other channel to verify equal output, but never did. I blame being cold.

I also used Josh’s instructions to take distortion sweeps at 1000w for both configurations. I’m not sure what I’m looking at here, so I’ll just post the graphs.

Series/Parallel:


Parallel 2ch:


Chris
 
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