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Ricci's Skram Subwoofer & Files

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Here are some HR sims with the 21DS115-4 and the Lavoce SAN214.50. Both are using measured specs with semi inductance from drivers I have. Dark line is all vents open. Grey line is with one vent blocked. There will be some slight differences due to the inability to model the vents and horn slot exactly, but they should be relatively minor. 

 

21DS115-4 

1943039715_Skram21DS115-4Sim4vand3v.jpg.8db75c9e7a876aedbf235291a8c6d09b.jpg

 

SAN214.50

1192072405_SkramSAN214.50Sim4vand3v.jpg.2f4205d4812f55cabce03f4364e42c43.jpg

 

Hell might as well throw the NSW6021-6 in there too. Also using measured specs with semi inductance. 

462255192_SkramNSW6021-6Sim4vand3v.jpg.9c4e907c0cb41f9bac72a42f8ec917cf.jpg

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1 hour ago, m_ms said:

@Ricci

Good looking (and likely performing) single-build of the SKhorn - anticipating measurements/testing.

Do you see yourself returning to Tapped Horns or even Front Loaded Horns with future builds? Does the SKhorn (singles or not) sound like TH or FLH's with similar tuning frequency - seeing that it houses its driver hidden inside the enclosure, or how would you describe it sounding different?

/Mikael

I don't see myself doing many TH or FLH's in the future. FLH makes more sense for systems without size restrictions, looking to extract maximum from a single driver and those without the need to go very deep. I might employ it for 80-300Hz range or so in the future but it's doubtful I'd do a subwoofer. 30Hz extension is bare minimum for something I consider a "sub". FLH's can be bested in the lower register by smaller more output dense alignments. They can sound very good. TH's I've found that the limited bandwidth and limitations imposed by path length needs and folding options cause them to be difficult to design well. More importantly the harmonic resonances in the response are audible and can cause major issues with harmonic distortion and ringing. In order to keep this up out of the sub bandwidth, well damped and above the low pass filter it's difficult to get extension much lower than the Othorn IMHO. TH's are best with extension to the 30-40Hz range IMHO. When done right they can sound killer as well, but the driver is more exposed usually so they have a bit more operational noise than FLH's. Better driver cooling though. The hybrid BP's I've been doing can be smaller than TH's, much smaller than FLH's and can almost match the TH's output. They are still somewhat tricky to design well and package but easier than a TH and easier to build. The response can be made to lack the upper end response issues more easily. The driver is buried in the cab so mechanical and operational noises are diminished, which is a big deal to me, but the air exchange and cooling is a lot better than a FLH. They are a bit more tolerant of a wider range of drivers as well. The sound is definitely clean and visceral when done right. 

In summary I have heard excellent examples of all 3 sub types. I'm a big fan of burying the drivers in the cabinet. Reducing the direct operational noise of the drivers especially when operating at high excursion / high output scenarios makes a large difference to me. The tradeoff is it may be difficult to tell just how hard the driver is being worked. 

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Big brother Skhorn is lonely. Will be joined soon with its triplet half brothers :) 

Already started cutting the outside panels and drawing the outlines.

Josh, would these 3 drivers work in the Skram? 

B&C 21SW115, 18SW115, 18NW100 

These are what I have on hand right now but will get more 21DS115 later if  I have some tax refund.

 

Skram3X.thumb.jpg.01c975460ba8d736311cfeea25459fcd.jpg

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Exciting stuff Ricci! I guess the 21NTLW5000 will just fit in there. 😛

I also think you should flip the skids 90degr on the long sides you could use 2 per side instead of 4. saves some material and routing. I cut the skids myself from 15mm HDPE plastic sheets.

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Yes compared to the DS115 (40bl) the 18s TLW5000 30bl motor is weak.

The 18s 21NLW9601 (43bl) or 18s 21NLW9001 are better options. But personally I prefer B&C drivers. Or the yet to be released new Eminence is an option.

 

 

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6 hours ago, USRFObiwan said:

Exciting stuff Ricci! I guess the 21NTLW5000 will just fit in there. 😛

I also think you should flip the skids 90degr on the long sides you could use 2 per side instead of 4. saves some material and routing. I cut the skids myself from 15mm HDPE plastic sheets.

I looked into cutting some HDPE or similar. I left the skids on the longer dimensions because it should be a bit more stable. I'm still not entirely sure which way I will go for feet / stacking yet.

It should fit no problem. There is still no availability of that driver here in the US. I see it available in a few shops across the Atlantic but I haven't seen anyone that actually has them yet. Seems like they've been advertising that driver for a long time now not to have stock.

Simulation with the 21NTLW5000. Standard sim with factory specs is the black line and actually looks pretty good. Using the generic high LE function uglies up the response a lot (grey line). It doesn't load the vents as strongly as the more efficient drivers. I don't think it will behave like high LE graph though. Unfortunately there aren't any semi inductance specs available for the driver to do the more accurate sim. Hopefully someone will pull an impedance measurement from one and post those soon.

517208606_Skram21NTLW5000Sim.jpg.4de76116e00854f6c6b4d464da08cc8b.jpg

 

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By the way. The reason I'm not posting the HR inputs is due to the way the vents behave. The vents are loaded into the corner and back wall which will increase their apparent length and tune like a physically longer vent. HR has no way of knowing this so the vent length HR input is longer than the physical vent length to hit what should be the correct tuning the cab will have with the amount of vent area. Doing this causes the vent resonance to be somewhat lower in frequency and more severe than it will be. In order to get the vent resonance in what should be the correct frequency range I shorten the vent length to the physical length, but this raises the tuning of the cab. To compensate for that in the sim I have adjusted the vent area down to hit the expected real tuning correctly. These are the sims shown. To further complicate things overall vent volume and area affects the amount of efficiency that the vents have. More volume and area= more gain. Also a single large circular vent has upper end resonance behaviors that are different than multiple smaller vents of the same area that are square in cross section. HR doesn't know this either. I saw this same type of behavior with the MAUL which loaded a huge vent right into the back wall of the cab and to a lesser extent the Skhorn.

Anyway I'm interested to see what the vent resonance turns out like in the real cabs. It could end up with almost no effect on the response (hopefully) or it could create a large notch as low as 160Hz (WCS). As usual I think it will be in between. I'm going to wait till I have real data so I can adjust the HR inputs to reflect the vent behavior before posting the inputs.

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Hello :)

First of all i wanna thank you for designing these awesome subs! I can imagine how much work you have put into the design and I really appreciate that you share your designs freely and support the DIY community with pro audio subwoofer designs that are able to compete with the big brands.

I'm proud to be able to say that we will be making 2 of them loaded with 21ds115`s within the next few weeks. Maybe our party collective has the honour to be the first to build a pair of these beauties in Germany ;)
They will be used mostly outdoors for Bass Heavy music.
We will make sure to take some pictures during the build and post measurements afterwards!

Cheers, Nathan

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Any chance I could get a PM with the plan so I can order the wood? Couldn't find the measurements on the pics of post 2 somehow :D

EDIT> noticed that prints will still take time, was confused by jesal already having the dimensions as it seems 😇

Edited by LSC

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I got my dimensions by printing and scaling it based on the 32x36 inch area. Just too excited to build and jumped the gun with the ruler :)

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Veerry understandable, Jesal and good to see that you care for your lonely skhorn in a way of constructing some little siblings! Keep us updated!
Plenty of wood has been ordered, that's how far I got today x)

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Yeah 4 should be enough for now lol

Picked up more Baltic Birch, the lumber guy commented "Oh it's you again" ;)

Have all the 32x36 panels cut and the 22.5" interior panels all ripped and ready to go.

Hoping these 3 should go pretty quick...

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Thank you Ricci for sharing your project!

Once again!

What kind of changes should we make for 18" driver with close T/S parameters?

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The only 18 I've modeled is the Pro5100 TC Sounds, which looks good.

Changing the baffle cutout for the 18" would be the only change needed to fit an 18.

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14 hours ago, Infrasonic said:

I want a bigger one.

 

 

 

 

Excellent work as always, Josh. You should get paid for this stuff, ya know.

You always do!

When I go bigger I end up stuffing more drivers in the cab!

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PDF Print added to the first post for download. I'm having trouble with the DXF print giving an error. I'll have to look at that later.

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I like how these are called the Skram.

 

People don't say scram anymore. Some people should tell other people to scram more often. 🤣

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Oh yeah it's very important to shut down the reactors at times.. 😜

Quote

A scram or SCRAM is an emergency shutdown of a nuclear reactor. It is a type of kill switch. In commercial reactor operations, this type of shutdown is often referred to as a "SCRAM" at boiling water reactors (BWR), a "reactor trip" at pressurized water reactors (PWR) and EPIS at a CANDU (CANDU). [1] In many cases, a SCRAM is part of the routine shutdown procedure as well.

https://en.wikipedia.org/wiki/Scram

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Did scram drills when I was onboard the SSN 762 and 763.

 

Ricci will four of these all vents open be fine on a FP14k?

 

They would be an 8ohm per channel or all four at four ohm on a single bridged channel. Will be building four. Just have to move and then I will get started. 

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If possible it would be great to see a sim for the 21sw152.  How high do you think this will play smoothly,  150hz? or perhaps even higher?  Compared to a Othorn it seems like one should expect a slightly higher output with more usable response up past 100hz?  For the people who have heard both the othorn and the skhorn, is there a difference between the type of sound between the two?  Curious about what to expect as far tightness, speed, musicality and felt impact on the dance floor between the two.  Having already built some Othorns would it be worth the effort to give the Skram a try?  Cheers

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