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Ricci's Skram Subwoofer & Files

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Ah, yeah that makes sense... was just an idea. Seems I fucked up putting a pair of my skrams in my livingroom... seems unacceptable to not leave them there. Just messaged my Cnc guy, another pair on the way. 

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Ricci, I see you added egg carton style foam to the SKhorn's. Did you ever measure to see what improvements this adds? Is it necessary? What your thoughts? I was always under the impression that adding stuffing to subs was usually a net loss in overall output?

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7 hours ago, peniku8 said:

Doing so wastes space. It lowers the back chamber volume which raises the tuning (ever so) slightly and decreases bottom end output. Probably by less than half a db but it's still wasted potential.

Look here if you wanna get some ideas for port block solutions.

+1

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1 hour ago, menace said:

Ricci, I see you added egg carton style foam to the SKhorn's. Did you ever measure to see what improvements this adds? Is it necessary? What your thoughts? I was always under the impression that adding stuffing to subs was usually a net loss in overall output?

It's not stuffing. It knocks down high frequency radiation from bouncing around inside of the cab. You may think low passed subwoofer = no high frequency radiation but that's not entirely true. Distortion, mechanical operational noises, internal standing waves in some cases, air noise, leads vibrating against cab walls, etc...Anyway I've always lined my vented subs because it does knock down these junk noises a bit. Try snapping your fingers or knocking on the side of the cab with no lining and then with some lining, with your head inside. 

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On 9/12/2019 at 12:37 PM, Droogne said:

Ok thanks. I modelled them all out for my own reference. Here the results for everyone interested. I Xmax limited the output (15mm for the 21Sw152)

1 port operation. Xmax at ~22hz, 60 volts

image.png.46a95a99f59173c44bd1a46e164a9788.png

2 port operation. Xmax at 30hz, 70 volts

image.png.cdaee8d04fa968283d560d3f3c8ac0a0.png

3 port operation. Xmax at ~22hz, 80 volts

image.png.540f0715e36509f990b262428f408777.png

 

 

 

These don't look right to me. The response shape looks off. Are you using the generic LE (red Le) function? 

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38 minutes ago, Ricci said:

It's not stuffing. It knocks down high frequency radiation from bouncing around inside of the cab. You may think low passed subwoofer = no high frequency radiation but that's not entirely true. Distortion, mechanical operational noises, internal standing waves in some cases, air noise, leads vibrating against cab walls, etc...Anyway I've always lined my vented subs because it does knock down these junk noises a bit. Try snapping your fingers or knocking on the side of the cab with no lining and then with some lining, with your head inside. 

Okay, got ya. Perhaps my net loss understanding pertains more to tapped horns.....

Thanks for the reply. Ill be getting a couple of these cut this week probably not built to the week after though. looking forward to it! Will be interesting to do side by side listening to the othorn made out of mdf I have.......

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1 hour ago, menace said:

Okay, got ya. Perhaps my net loss understanding pertains more to tapped horns.....

Thanks for the reply. Ill be getting a couple of these cut this week probably not built to the week after though. looking forward to it! Will be interesting to do side by side listening to the othorn made out of mdf I have.......

Any surface not in the direct path of sound can be lined with foam. Since THs only have a direct path, theres nowhere to put foam.

Hope you're not moving these MDF cabs around much or you won't have fun for long. New cabs also going to be MDF?

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32 minutes ago, peniku8 said:

Any surface not in the direct path of sound can be lined with foam. Since THs only have a direct path, theres nowhere to put foam.

Hope you're not moving these MDF cabs around much or you won't have fun for long. New cabs also going to be MDF?

I trade in MDF so it kinda free. It holds up to a good chunk of power though I was quite surprised and no that cabinet is not for moving around. These next cabinets will be made of the birch ply certainly.

Thanks for the good explanation regarding damping too...

.

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Thanks for another great design!

I've imported a few of the dxf files into Aspire and Vectric ... They seem to be a different size/dimension than the PDF listed dimensions. Is that accurate or do I have a problem on my end? 

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1 minute ago, klipsch said:

Thanks for another great design!

I've imported a few of the dxf files into Aspire and Vectric ... They seem to be a different size/dimension than the PDF listed dimensions. Is that accurate or do I have a problem on my end? 

Scale? 1/16 I think I recall my cnc guy saying...

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9 minutes ago, menace said:

Scale? 1/16 I think I recall my cnc guy saying...

I've exported dxf out of fusion360 sketches and imported into Vectric or Aspire in the past. Those always match dimensions.  Maybe there's some setting I need to find to import these dxf files from solidworks to get matching dimensions to the pdf? 

I'll try to adjust the scale. Thanks menace. 

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14 hours ago, Ricci said:

These don't look right to me. The response shape looks off. Are you using the generic LE (red Le) function? 

I did yes. Didnt use the "lossy Le" option.

Here is the difference:

2 port configuration:

image.png.ccc4332a27bb0534daa87ccfce1a6b5f.png

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Also, what do you think of trying to make an 18" equivalent version? I very much like the performance of the Skram, but their size is scaring me a bit. Height and width aren't problematic, but the depth is. I would like to reduce it to 60-70cm, as it would make it more accessible for my living situation. 

If not possible to reduce the depth without changing the design completely, then I'll just leave the size as is. 

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@Droogne

It would lower the rear chamber volume and then the bass reflex tuning would go up.

If others can confirm.

You'll not reach 30hz if you reduce the depth, maybe 35hz with 70cm but with 60cm, you're losing a lot.

You can edit the hornresp sim to see what you're gonna lose exactly.

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2 hours ago, Droogne said:

Also, what do you think of trying to make an 18" equivalent version? I very much like the performance of the Skram, but their size is scaring me a bit. Height and width aren't problematic, but the depth is. I would like to reduce it to 60-70cm, as it would make it more accessible for my living situation. 

If not possible to reduce the depth without changing the design completely, then I'll just leave the size as is. 

While fooling around with some 18" pro drivers I found that if you wanted them to play down to 30Hz (F3, not F10), the cab required would be so big that it could also fit a 21. Since most 21" drivers cost just a tad (maybe 10%) more than their 18" equivalent, going with 18" doesn't make much sense imo.

If the cab is too deep for you, you could trade some depth for height. That would extend the horn section, but you might run into issues with the port length.
Maybe make it very tall and compensate for the shorter port with added back chamber volume. If it's tall enough, the horn section could also be a single segment, or well, a big segment and the small segment which opens to the front.

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17 hours ago, klipsch said:

Thanks for another great design!

I've imported a few of the dxf files into Aspire and Vectric ... They seem to be a different size/dimension than the PDF listed dimensions. Is that accurate or do I have a problem on my end? 

Set the document as metric when you import. Can export as IPS from Apsire if your CNC is setup for that.

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5 hours ago, dsl1 said:

Set the document as metric when you import. Can export as IPS from Apsire if your CNC is setup for that.

Thanks dsl1.  Still no dice.  If I import the dxf's into VCarve, Aspire, or Fusion360 in metric or imperial, I still do not get the same sizes as shown in the pdf.  Maybe I should not be comparing the dxfs to the pdf?

 

Edit:  After looking at more parts, it appears that the dxfs provided do not match up with the 233186287_Skramprint.pdf (and maybe they were never intended to be).  

Example: 1472850171_TopBraceSkram_TI.DXF would theoretically be Sheet 16 Part M in the 233186287_Skramprint.pdf.  However, it looks like 1472850171_TopBraceSkram_TI.DXF is really Part M and Part N together in the 233186287_Skramprint.pdf.  If that is true, I've been comparing things I should not have been, no?

 

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7 hours ago, klipsch said:

Thanks dsl1.  Still no dice.  If I import the dxf's into VCarve, Aspire, or Fusion360 in metric or imperial, I still do not get the same sizes as shown in the pdf.  Maybe I should not be comparing the dxfs to the pdf?

 

Edit:  After looking at more parts, it appears that the dxfs provided do not match up with the 233186287_Skramprint.pdf (and maybe they were never intended to be).  

Example: 1472850171_TopBraceSkram_TI.DXF would theoretically be Sheet 16 Part M in the 233186287_Skramprint.pdf.  However, it looks like 1472850171_TopBraceSkram_TI.DXF is really Part M and Part N together in the 233186287_Skramprint.pdf.  If that is true, I've been comparing things I should not have been, no?

 

Ricci also split up the bracing in the SKHorn into multiple pieces instead of using one large piece, because that leaves room for error if you're building it without a CNC.

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14 hours ago, klipsch said:

Thanks dsl1.  Still no dice.  If I import the dxf's into VCarve, Aspire, or Fusion360 in metric or imperial, I still do not get the same sizes as shown in the pdf.  Maybe I should not be comparing the dxfs to the pdf?

 

Edit:  After looking at more parts, it appears that the dxfs provided do not match up with the 233186287_Skramprint.pdf (and maybe they were never intended to be).  

Example: 1472850171_TopBraceSkram_TI.DXF would theoretically be Sheet 16 Part M in the 233186287_Skramprint.pdf.  However, it looks like 1472850171_TopBraceSkram_TI.DXF is really Part M and Part N together in the 233186287_Skramprint.pdf.  If that is true, I've been comparing things I should not have been, no?

 

Those were just my personal CNC files. Ricci had issues uploading his. 

File names won't match the PDF and sizes are going to be a bit different because of dados / rabbets. If you're cutting with a CNC, it does fit together with my files :)

I'll put together an actual cutsheet DXF at some point.

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1 hour ago, dsl1 said:

Those were just my personal CNC files. Ricci had issues uploading his. 

File names won't match the PDF and sizes are going to be a bit different because of dados / rabbets. If you're cutting with a CNC, it does fit together with my files :)

I'll put together an actual cutsheet DXF at some point.

Thank you for clarifying!

I apologize for not realizing that to begin with.

I have a B&C 21SW152 8 ohm version sitting in a box.  I guess I should work on nesting some of your dxfs and make the 152 a home.

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4ft x 8ft sheets? (1200mm x 2400mm)

 

I am very slowly making my pair of Skrams. I have to buy some more ply but progress is progress.:)

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8 hours ago, chrapladm said:

4ft x 8ft sheets? (1200mm x 2400mm)

 

I am very slowly making my pair of Skrams. I have to buy some more ply but progress is progress.:)

Yes. 4x8 sheets. I generally use 4x8 pine if painting with duratex/restorex equivalent and using fasterners.  The expense of a maple or Baltic has not seemed worth it in my experience unless staining. 

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1 hour ago, klipsch said:

Yes. 4x8 sheets. I generally use 4x8 pine if painting with duratex/restorex equivalent and using fasterners.  The expense of a maple or Baltic has not seemed worth it in my experience unless staining. 

Thanks. Its what I use also. Other wise I couldnt afford to build much. Arauco B/C and PL premium. Just building a pair of Skrams so I was curious how much ply I wold still need. Looks like 3 more sheets for sure.

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