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Ricci's Skram Subwoofer & Files


Ricci

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On 4/28/2022 at 6:32 PM, rolo95 said:

Ahh, kind of danley TH118, those are called tapped horns right ? or just horn subs

The TH118 is a tapped horn, but neither my sub nor the Skram are. They're both vented frontloaded bandpass cabinets.
7IoupRp.jpg

They sound and perform great, but I wouldn't build them again. The 21ds115's move the stack (sub+ARCS=250lbs) around. If you're planning on making a line of cabs in front of a stage they'd all be moving all over the place if you drive them near their limits.

I heard the Othorn experienced similar issues. Skram fires forward, so it doesn't 'lift' the cab when the driver is working.

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@rolo95 For the moving sub problem I would recommend those anti-vibration rubber mats that you can put under washing machines. Cheap and effective. You can even cut them into smaller pieces to save cost. A washing machine is a hell of an unbalanced beast and still I've never seen one move (significantly) even after years of operation. Those mats also equalize uneven floors up to a certain degree and protect your subs from scratching. Or the floor itself if you're ever playing on parquet.

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has any builder attempted to update the skram plans to factor in rebates for all the panels? I was watching a video of a boxman in the UK who was a strong advocate of this from a woodworking standpoint as you would create significantly more contact area between each panel resulting in much sturdier connections and a better build - at a price of course.

Just unsure if it's actually necessarily or just an overkill? As it'll be complicated (without having SolidWorks) to modify the existing cut sheets to factor in these additional dimensions. The guy recommended 3mm recesses which can definitely cause issues if not taken into account.

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You mean dado joints like on this board?
FBh7isD.jpg

I use them mostly to make the assembly easier, since it's hard to get the position wrong when everything slots right into place. It doesn't help much with structural integrity unless you do like 10mm or so I'd say. I do 3mm too.

Doing this without a CNC is a massive waste of time imo. I only drew a sketch on to the floor board when I built my Skhorn and went from there.

IzwTTMI.jpg

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A few builds in here have done it I believe, I didnt bother as Peniku8 said it takes a real long time without a CNC and doesnt add that much extra strength if the rest is assembled properly.

If you have a CNC and want the most epically perfect cabs possible then go for it, just add 6mm to the length of each panel and then cut the channels out 3mm on each side

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Just unloaded the wood for my 2 SKRAMs, starting the build on Thursday... oh boy 😻
Unfortunately I don't have access to a CNC router so I have go with lamellos instead. When it's finished I will probably reinforce some critical edges with glass fiber fabric & epoxy resin. That has to do for now...

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5 hours ago, Domme said:

Just unloaded the wood for my 2 SKRAMs, starting the build on Thursday... oh boy 😻
Unfortunately I don't have access to a CNC router so I have go with lamellos instead. When it's finished I will probably reinforce some critical edges with glass fiber fabric & epoxy resin. That has to do for now...

Starving to see your construction pics   😻

hope you can share some audio measurements when you finish the cabs !!

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1 hour ago, rolo95 said:

Starving to see your construction pics   😻

hope you can share some audio measurements when you finish the cabs !!

Will do. Got some tolerant neighbours and a wide field in front of the house, but unfortunately my mic is only built for 128dB. Should be enough for those civilized measurements, but I will try my best to make it suffer 😉

 

2 hours ago, Tahoejmfc said:

I love how many people have built these subs! Also, I just love these subs as well. https://www.instagram.com/tv/CalY8Y1Bi6D/?igshid=YmMyMTA2M2Y=

 

I love this truck! I had it as wallpaper and all of a sudden he's wearing a custome 🤣

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Hey everybody, I am wondering if and how you seal the area between your cabinet and handles, cable terminals and so on to minimize air leaks. I was thinking about using some 1mm neoprene sheet and was wondering if someone here has got experience with it or what you are using instead.

Cheers!

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1 hour ago, Domme said:

Hey everybody, I am wondering if and how you seal the area between your cabinet and handles, cable terminals and so on to minimize air leaks. I was thinking about using some 1mm neoprene sheet and was wondering if someone here has got experience with it or what you are using instead.

Cheers!

attachment.php?attachmentid=2681952&stc=

From a build thread - that's what I did around the handle area - speaker gasket IIRC 

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1 hour ago, Domme said:

Hey everybody, I am wondering if and how you seal the area between your cabinet and handles, cable terminals and so on to minimize air leaks. I was thinking about using some 1mm neoprene sheet and was wondering if someone here has got experience with it or what you are using instead.

Cheers!

I got this gasket tape
https://www.amazon.de/dp/B0792JGC2H/

Easier alternative for handles:
https://www.penn-elcom.com/default.asp?PN=H1105G
for
https://www.penn-elcom.com/default.asp?PN=H1105

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Finally spent some sheckles to have a proper power panel build to run my amps on 240v which isn’t super common up here in most venues. While subtle, things felt a little cleaner and tight and amps ran noticeably cooler. We knocked some bottles off the wall of the bar which was a first so it seemed to have helped :) 

https://youtu.be/rqMiTLL15s8

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6 minutes ago, Ricci said:

I do like 240v for running big / multiple amps. Just seems to do a better job in most cases. 

Speaker gasket tape FTW! I use that for the hatches, handles, drivers, etc...Always good to have on hand. 

Interesting experiment for sure. My personal take away is use 240v if available. If you don't have access you can still get solid performance from 120v plugs, just ensure you aren't overloading your amplifiers with too many speakers. On 120v I run 1 amplifier per 2 skrams on a 4ohm load and can achieve likely 90-95% of what can be achieved using 240v. don't expect to get the most of tough 2ohm loads from 120volt. Of course with 120v you will draw twice the amperage, deal with more heat and that may but extra strain on your gear.

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  • 2 weeks later...

Thought I might as well bring it up in this thread being it's about a design involving big-diameter woofers:

How much of a problem is lack of cone control with large diameter woofers (say, +15"), also known as "wobbling"? Is it a problem mostly with very high excursion, typically no more than moderately sensitive woofers, or is it a general phenomenon and problem even with more efficient pro woofers like the 21" variants used in the Skram, Skhorn and Othorn? 

How much does it matter sonically and for overall performance? Is it even a real issue, and does it warrant designs using instead a multitude of smaller, say, 12" woofers compared to fewer 18" or 21" dittos?

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By "lack of cone control", do you mean non linearity in the translation from electrical to kinetic energy or do you mean cone flex? The former can be remedied by a stronger motor, the latter through a stiffer cone.

Both problems are challenges to the designer, not to the end user. Any properly designed driver will play predictably based on the Klippel graphs. For B&C drivers I think it's the Xvar value, which is a general rule of thumb for when the driver behaviour will transition into non-linear territory. If this was a huge issue, big drivers wouldn't be so popular.

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  • 3 weeks later...

Cone flex can be a problem but only in drivers not designed adequately for high pressure applications. It has not been a problem with any of the cab designs I've made/tested/used with 18" or larger drivers. 

There is a reason that modern high power sub drivers have a heavy mms and stiff suspensions. It is required for strength, control and power handling. The cone on a larger diameter driver must be stronger / thicker than a smaller diameter unit, the voice coils are massive to handle large power inputs, the suspensions are stiffer and heavier to keep things centered and prevent overshoot, fight against gravity over time, etc. Most pro audio and car audio subs are built to take a lot of abuse. This is why a pro audio 15" woofer might have a MMS of 80g but a true subwoofer might have an mms >250g. Even though the 2 might have a similar FS and Xmax rating or even power handling, they are still suited to different jobs. The 80g 15" woofer is not going to fare as well in a FLH or other high output high pressure loading. 

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  • 2 weeks later...

Hello !

Took me a while but I finally remembered to save my measurements to share those with you.
They are worth what they are, I'll try to get unfiltered ones the next time.

So here is an uncalibrated measurement of 2 Skram units, 21DS115-4 loaded with a 2nd order BW filter at 24hz and a 4th order LR filter at 108.8hz. (No correction EQ). The subs were 8 meters away.

Considering how flat it is with the LR filter, you can imagine how the curve is rising after 50hz.

 

289392273_1174726206430275_8275945147078624732_n.png

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  • 2 weeks later...

Hello Alexlel. Thanks for the info. Interesting. A 4th order LR would be 6db down at the Xo frequency. 109Hz. The response should be slightly rising towards 120Hz with that driver without any processing at all. That's including increasing directivity/baffle step as the frequency rises. You also have a pair of cabs. I wouldn't be surprised to see the response up 4dB or so at 100Hz under these conditions. 

Either way that's a useful starting point with just a LPF and HPF. Lowering the LPF frequency and/or changing the slope or filter type should be able to get your XO to the mains where you want it without much extra EQ needed. 

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On 7/8/2022 at 8:35 PM, Ricci said:

Hello Alexlel. Thanks for the info. Interesting. A 4th order LR would be 6db down at the Xo frequency. 109Hz. The response should be slightly rising towards 120Hz with that driver without any processing at all. That's including increasing directivity/baffle step as the frequency rises. You also have a pair of cabs. I wouldn't be surprised to see the response up 4dB or so at 100Hz under these conditions. 

Either way that's a useful starting point with just a LPF and HPF. Lowering the LPF frequency and/or changing the slope or filter type should be able to get your XO to the mains where you want it without much extra EQ needed. 

Hello Ricci,

I had the opportunity to get some fresh measurements this week-end.

The 2 skrams, 21DS115-4 loaded, were superposed horizontally, mic on the ground at ~3 meters.

I did measure one cab (the one sitting on the floor) and two cabs.
No LPF, my HPF was set at 19.7hz (as low as my processor was able to go, I think it was a -24dB BW but looking at my precedent curve I may have put a -24dB LR by inattention which would explain the slighty higher -3dB point on those)

These are still uncalibrated btw !

Green : 1 cab | Red : 2 cabs

Skrams.PNG

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