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post #181 of 219 Old 05-02-2018, 03:17 PM - Thread Starter
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Originally Posted by mtg90 View Post
In REW if you go to controls on the right side you can add offsets to the measurements to normalize them to the +5MV, basically stacking them on top of each other which will help visualize the compression much better.

So for the -20MV sweep add 25dB, then add 20dB to the -15MV sweep, ect...

@mtg90

Here we go. I did as you said (i think) and I also compared the distortion graphs.
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post #182 of 219 Old 05-02-2018, 04:25 PM - Thread Starter
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The Periscope Subwoofer B&C 21DS115

I noticed i have ringing at 18hz and 27hz at -15MV. Should i try to notch 18 and 27hz to alleviate the ringing? I don't think bass traps are an option unless they are huge. Note, these measurements are without audyssey or any inuke eq and just a single point in the room so the response doesn't represent what i'm actually hearing.

thanks,

Pete
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post #183 of 219 Old 05-11-2018, 03:02 PM - Thread Starter
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The Periscope Subwoofer B&C 21DS115

Quote:
Originally Posted by corradizo View Post
I noticed i have ringing at 18hz and 27hz at -15MV. Should i try to notch 18 and 27hz to alleviate the ringing? I don't think bass traps are an option unless they are huge. Note, these measurements are without audyssey or any inuke eq and just a single point in the room so the response doesn't represent what i'm actually hearing.

thanks,

Pete


Got some help in the @AustinJerry thread (thanks AustinJerry!!) and it was determined that this is nothing to worry about as you kinda want explosions to ring a bit. The upper band decays nicely at my normal listening volume. Once you get up to -10, -5, 0 it gets pretty nuts with all sorts of ringing..of course the walls are also "breathing" at those levels.

Thread: https://www.avsforum.com/forum/91-aud...graphs-28.html

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post #184 of 219 Old 05-11-2018, 03:13 PM - Thread Starter
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I did a little test today based on two ways to set a high pass filter in the inuke6000dsp. I posted this in @Shreds inuke6000 thread - a wealth of information for inuke owners. (Thanks @Shreds !)With this sub coming in at 14.8hz tune I need to set a 15hz high pass. The trick is usually to set your crossover section to 20hz Butterworth 12db/octave and to set the PEQ section to 20hz HS12 -6db. In looking at and talking to Mark Seaton about the sub he designed with the same driver, he recommended the same crossover section but a PEQ setting of 20hz LS12 +6db. He also recommended that in order to flatten the sub response to match the outdoor groundplane response an additional PEQ of 90hz HS12 -14db be used. I left this filter in place for both measurements. Here are the results and the mdat if anyone cares to play with it. Rew was at -12dbfs and acr was at -20mv. Audyssey was off.



Mdat https://www.dropbox.com/s/bv636znjaw...ared.mdat?dl=0
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post #185 of 219 Old 05-11-2018, 03:39 PM
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Quote:
Originally Posted by corradizo View Post
Got some help in the @AustinJerry thread (thanks AustinJerry!!) and it was determined that this is nothing to worry about as you kinda want explosions to ring a bit. The upper band decays nicely at my normal listening volume. Once you get up to -10, -5, 0 it gets pretty nuts with all sorts of ringing..of course the walls are also "breathing" at those levels.
I always assumed anything below 30hz would have some ringing regardless of treatments, was that the consensus.

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post #186 of 219 Old 05-11-2018, 03:45 PM - Thread Starter
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Originally Posted by Gorilla Killa View Post
I always assumed anything below 30hz would have some ringing regardless of treatments, was that the consensus.


You are correct, the guys in AustinJerry's thread indicated that. I didn't know. I also didn't know that it makes no sense to worry about ringing at "demo" levels and it's better to focus on quality at the levels you actually listen at.
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post #187 of 219 Old 05-12-2018, 04:40 AM
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Im really curious how these sound compared to large excursion drivers. Do they come as a little thinner in the sub 30hz dept? Nobody close to me has them so that leaves me with a build somewhere in the fall.

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post #188 of 219 Old 05-12-2018, 07:35 AM - Thread Starter
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Originally Posted by Gorilla Killa View Post
Im really curious how these sound compared to large excursion drivers. Do they come as a little thinner in the sub 30hz dept? Nobody close to me has them so that leaves me with a build somewhere in the fall.


These can get out to 20mm excursion with very little distortion. My ht18's could get out that far too but with far more distortion. My assumption is the low distortion is what makes the bass different. It's far better to my biased ears :-)
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post #189 of 219 Old 05-12-2018, 07:36 AM
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Originally Posted by corradizo View Post
These can get out to 20mm excursion with very little distortion. My ht18's could get out that far too but with far more distortion. My assumption is the low distortion is what makes the bass different. It's far better to my biased ears :-)


Are you gonna build two more?
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post #190 of 219 Old 05-12-2018, 07:45 AM - Thread Starter
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Are you gonna build two more?


We had a storm this morning and the thunder shook the house..almost as much as the subs! I'm good. Haha.

Seriously though, I don't think so. My system is in an open basement media area and can already get pretty nuts. Not @eng-399 nuts, but enough for me. If I did, it wouldn't be for output but for smoothing out the bass in the space.
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post #191 of 219 Old 05-12-2018, 07:47 AM
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Originally Posted by corradizo View Post
We had a storm this morning and the thunder shook the house..almost as much as the subs! I'm good. Haha.

Seriously though, I don't think so. My system is in an open basement media area and can already get pretty nuts. Not @eng-399 nuts, but enough for me. If I did, it wouldn't be for output but for smoothing out the bass in the space.


Haha ok good. The thunder shook my house too overnight. Much more then my subs all the way up in my room. I can also say I am done adding bass. At least sub bass. I’m still interested in adding a couple pa-460’s for midbass. Listen to me. I’m crazy. What am I talking about.
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post #192 of 219 Old 05-12-2018, 07:51 AM - Thread Starter
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Originally Posted by Jk7.2 View Post
Haha ok good. The thunder shook my house too overnight. Much more then my subs all the way up in my room. I can also say I am done adding bass. At least sub bass. I’m still interested in adding a couple pa-460’s for midbass. Listen to me. I’m crazy. What am I talking about.


I cross them to my Fusion 8's at 120hz. Midbass galore! John Wick 2 gun shots were pelting my body!
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post #193 of 219 Old 05-12-2018, 07:53 AM
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I cross them to my Fusion 8's at 120hz. Midbass galore! John Wick 2 gun shots were pelting my body!


I cross over from my 6 hst’s and 2 ds4’s still at 80. It sounds great. I want to bump the mids up on my titans. I know they can give me more midbass. Always something to tweak.
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post #194 of 219 Old 05-12-2018, 07:56 AM - Thread Starter
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The Periscope Subwoofer B&C 21DS115

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Originally Posted by Jk7.2 View Post
I cross over from my 6 hst’s and 2 ds4’s still at 80. It sounds great. I want to bump the mids up on my titans. I know they can give me more midbass. Always something to tweak.


Nice, and/or bump the ds4 up to 120hz if they are up front. That's a next level setup you got there!
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post #195 of 219 Old 05-12-2018, 07:57 AM
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Nice, and/or bump the ds4 up to 120hz if they are up front. That's a next level setup you for there!


The ds4’s are nearfield. I still can try it
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post #196 of 219 Old 05-12-2018, 08:24 AM - Thread Starter
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The Periscope Subwoofer B&C 21DS115

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Originally Posted by Jk7.2 View Post
The ds4’s are nearfield. I still can try it


I wouldn't try nearfield at 120hz, it will definitely be localized, smear voices etc. I guess you're just going to need moaaar.

If I could get my wife to let up on the basement decor I wouldnt hesitate adding nearfield subs. I only get to do whatever I want behind the screen. That's the deal.
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post #197 of 219 Old 05-12-2018, 05:46 PM
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Originally Posted by corradizo View Post
I wouldn't try nearfield at 120hz, it will definitely be localized, smear voices etc. I guess you're just going to need moaaar.

If I could get my wife to let up on the basement decor I wouldnt hesitate adding nearfield subs. I only get to do whatever I want behind the screen. That's the deal.
Happy wife happy life
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post #198 of 219 Old 05-31-2018, 06:27 AM
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the slats concept was a cool idea. that could even be done with removable panels of various lengths, so instead of a bunch of slats, there is just a different size panel attached for each different tune. that might make for a more rattle free cab.


once the exit of the port is about 2x the distance from the top panel, it won't really be loading from that any more.


this is roughly how I would think about the port lengths as slats are removed. the second image from the left is the tricky one because the top panel will still be providing a small effect. but by the third image and fourth images there is no loading from the top panel any more, so there is just the port.


slot ports extend 1/2 port length out past the measured length on both ends, which is why the red line is extending out past the apparent end of the port in all cases.


Just want to make sure I understand this correctly. If you have a 4 inch high slot port and WinISD says your port length should be 20 inches (for example) you box port should actually be 16 inches and the other 4 will be made up on each end. Is this correct?

Also a thanks to @corradizo as I am somewhat copying this design although with a slightly higher tune. Your speakers look great!
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post #199 of 219 Old 05-31-2018, 07:14 AM - Thread Starter
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Just want to make sure I understand this correctly. If you have a 4 inch high slot port and WinISD says your port length should be 20 inches (for example) you box port should actually be 16 inches and the other 4 will be made up on each end. Is this correct?



Also a thanks to @corradizo as I am somewhat copying this design although with a slightly higher tune. Your speakers look great!


Yes, add half the port height to both ends of the length of the port measured down it's center. That overall length should match what's in winisd.

I know it was and example but I'll remind that I ultimately used 3.5" tall ports.

Thanks for the kind words!
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post #200 of 219 Old 05-31-2018, 07:34 AM
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Well, guess I screwed my port up then. Mine is 4.5 inches high. I'll have to trim some off from the first box. Second one isn't assembled yet. Thanks for the clarification.
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post #201 of 219 Old 05-31-2018, 02:21 PM - Thread Starter
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Originally Posted by Jedi940 View Post
Well, guess I screwed my port up then. Mine is 4.5 inches high. I'll have to trim some off from the first box. Second one isn't assembled yet. Thanks for the clarification.


4.5" tall internal? By how wide? Maybe we can work with it.
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post #202 of 219 Old 05-31-2018, 04:05 PM
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Port is 4.5" tall x 21 wide and tuned to 20Hz. Should be 37.26 inches long. Re-measuring mine, I'm wayyyyyyy off.

Full measurements are in this post.

Looking back, I didn't measure from the center of the port either. Just the top edge. This is my first time making a ported box. I'm just glad I caught it now.
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post #203 of 219 Old 05-31-2018, 04:36 PM - Thread Starter
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Quote:
Originally Posted by Jedi940 View Post
Port is 4.5" tall x 21 wide and tuned to 20Hz. Should be 37.26 inches long. Re-measuring mine, I'm wayyyyyyy off.



Full measurements are in this post.



Looking back, I didn't measure from the center of the port either. Just the top edge. This is my first time making a ported box. I'm just glad I caught it now.


I looked at the post but can't decipher your actual physical port length down the middle. What is that? Is the width subtracting the port rails?

If we can get this data we can predict what tune it will be as is.
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post #204 of 219 Old 05-31-2018, 05:21 PM
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Apparently I couldn't figure it out either. I find sketchup extremely frustrating because it never does what I think it should do so this entire design was done on paper/in my head. I was going back and forth between a couple different designs and I think i mixed the two for my final dimensions. My current port length by my measurement is 37.25 plus 4.5inches for the extension past the port giving me a total length of 41.75 inches. I really don't want to go any lower than 20Hz for a tune because I couldn't get the excursion under control putting 2200 watts to it without setting a high pass at 24Hz.

Since I'm having so many problems, I also decided to go back an re-calculate the volume of my box. See if this makes sense.

Going back and actually measuring the port, it is 4.5 high by 20.25 wide. This is subtracting the port bracing. Outer dimensions for the box are 48x30x24. This yields a total volume of 20 cubic feet. Since each box is roughly 2 sheets of MDF (only 8% waste) I can subtract 4 cubic feet for the volume of the wood leaving 16 cubic feet. I subtracted .5cuft for the driver and 1cuft for the bracing which gives me 14.5 cubic feet including port volume.

For a 20Hz tune, and a box volume of 12.6 (my newly calculated number) the port has a cross sectional area of .63 cubic feet. This multiplied by the length of the port at 40.64 =should give me the volume of the port or 2.11 cubic feet.

14.5 - 2.11 = a box size of 12.4 cubic feet. This is close enough for me and is also very close to my current port length so perhaps I got really really lucky although I'm still probably missing something.
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post #205 of 219 Old 05-31-2018, 06:10 PM - Thread Starter
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Quote:
Originally Posted by Jedi940 View Post
Apparently I couldn't figure it out either. I find sketchup extremely frustrating because it never does what I think it should do so this entire design was done on paper/in my head. I was going back and forth between a couple different designs and I think i mixed the two for my final dimensions. My current port length by my measurement is 37.25 plus 4.5inches for the extension past the port giving me a total length of 41.75 inches. I really don't want to go any lower than 20Hz for a tune because I couldn't get the excursion under control putting 2200 watts to it without setting a high pass at 24Hz.



Since I'm having so many problems, I also decided to go back an re-calculate the volume of my box. See if this makes sense.



Going back and actually measuring the port, it is 4.5 high by 20.25 wide. This is subtracting the port bracing. Outer dimensions for the box are 48x30x24. This yields a total volume of 20 cubic feet. Since each box is roughly 2 sheets of MDF (only 8% waste) I can subtract 4 cubic feet for the volume of the wood leaving 16 cubic feet. I subtracted .5cuft for the driver and 1cuft for the bracing which gives me 14.5 cubic feet including port volume.



For a 20Hz tune, and a box volume of 12.6 (my newly calculated number) the port has a cross sectional area of .63 cubic feet. This multiplied by the length of the port at 40.64 =should give me the volume of the port or 2.11 cubic feet.



14.5 - 2.11 = a box size of 12.4 cubic feet. This is close enough for me and is also very close to my current port length so perhaps I got really really lucky although I'm still probably missing something.


That sounds about right. Mine was about 10.5-11cu and was 48x30x20. I modeled with 1800w. I wouldn't go past 20mm excursion. I'll try to replicate your model to see what's up.
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post #206 of 219 Old 05-31-2018, 06:31 PM
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I also used 15mm as my target excursion based on the manufacturer's data. Xmax is listed at 15mm and the mechanical limit is 17m.
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post #207 of 219 Old 05-31-2018, 08:54 PM
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The Periscope Subwoofer B&C 21DS115

Quote:
Originally Posted by Jedi940 View Post
Apparently I couldn't figure it out either. I find sketchup extremely frustrating because it never does what I think it should do so this entire design was done on paper/in my head. I was going back and forth between a couple different designs and I think i mixed the two for my final dimensions. My current port length by my measurement is 37.25 plus 4.5inches for the extension past the port giving me a total length of 41.75 inches. I really don't want to go any lower than 20Hz for a tune because I couldn't get the excursion under control putting 2200 watts to it without setting a high pass at 24Hz.



Since I'm having so many problems, I also decided to go back an re-calculate the volume of my box. See if this makes sense.



Going back and actually measuring the port, it is 4.5 high by 20.25 wide. This is subtracting the port bracing. Outer dimensions for the box are 48x30x24. This yields a total volume of 20 cubic feet. Since each box is roughly 2 sheets of MDF (only 8% waste) I can subtract 4 cubic feet for the volume of the wood leaving 16 cubic feet. I subtracted .5cuft for the driver and 1cuft for the bracing which gives me 14.5 cubic feet including port volume.



For a 20Hz tune, and a box volume of 12.6 (my newly calculated number) the port has a cross sectional area of .63 cubic feet. This multiplied by the length of the port at 40.64 =should give me the volume of the port or 2.11 cubic feet.



14.5 - 2.11 = a box size of 12.4 cubic feet. This is close enough for me and is also very close to my current port length so perhaps I got really really lucky although I'm still probably missing something.



@Jedi940
Hp set at 20hz and all the info you just posted everything looks good from my end.
Your port height would be 3.75” by 20.25 as you posted for width. Vent length is 33.89” so 34 inches and first port resonance is 199hz.

If you made the port length 40 inches long your tune would be 18.66hz. And the rear port air velocity would be at 20ms
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post #208 of 219 Old 06-01-2018, 06:14 AM
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So since I already got ahead of my self and started building the box with my original port height of 4.5 inches, the question is, do I need to slide some MDF in the port to bring it down to only 3.75 inches? Of course, that will change my box volume slightly as well which will change the port length etc. At 4.5 inches tall, I'm looking at a first port resonance of 164Hz. Is that too low? When I thought my box volume was 14 cubic feet, it was 189Hz which is what I wanted.

All these issues will be corrected on the second box. I haven't started assembling the port on that one yet.
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post #209 of 219 Old 06-01-2018, 06:05 PM - Thread Starter
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Quote:
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So since I already got ahead of my self and started building the box with my original port height of 4.5 inches, the question is, do I need to slide some MDF in the port to bring it down to only 3.75 inches? Of course, that will change my box volume slightly as well which will change the port length etc. At 4.5 inches tall, I'm looking at a first port resonance of 164Hz. Is that too low? When I thought my box volume was 14 cubic feet, it was 189Hz which is what I wanted.



All these issues will be corrected on the second box. I haven't started assembling the port on that one yet.


I modeled it at 12cuft. You are at about 21hz tune as built. Just need a 20hz Butterworth 12db/octave high pass and you're good. Port velocity at 20m/s. First port resonance is plenty high at 178hz. I'd build them both this way. 1hz isn't anything. You will have zero compression issues in my estimation. If you want to tune lower you can add a board too the port or leave it and plug a port later with foam.
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post #210 of 219 Old 06-02-2018, 06:51 AM
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Originally Posted by corradizo View Post
I modeled it at 12cuft. You are at about 21hz tune as built. Just need a 20hz Butterworth 12db/octave high pass and you're good. Port velocity at 20m/s. First port resonance is plenty high at 178hz. I'd build them both this way. 1hz isn't anything. You will have zero compression issues in my estimation. If you want to tune lower you can add a board too the port or leave it and plug a port later with foam.
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Cool, that definitely makes it easier Big thanks for all your help and @eng-399 . And thanks to @LTD02 for posting that information. Not sure how I didn't know that with all my time on AVS but that is the first time in all the build threads I've read that I've heard it was necessary to keep the physical port shorter than what is modeled in WinISD. It was explained very well.
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