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Ricci's Skram Subwoofer & Files

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On 10/22/2019 at 2:45 PM, Ricci said:

Droogne I've done square ports before and they work well. The ideal is round and heavily flared or shaped which I've also done where it makes sense. Have you read the available AES and other papers on ports? There are many. Compression and chuffing noise do not necessarily correlate.

As far as I can tell compression doesnt relate to in/outflow patterns, but rather core turbulence aka the tube itself. Flaring wont change that. Only circumference and area. 

On 10/22/2019 at 2:45 PM, Ricci said:

There are also papers which point to some possible advantages with multiple smaller vents despite the increased skin effect.

I have been reading through https://drive.google.com/file/d/0B1gKnCRgylLcMnAya0dvc3NDZkE/view the last few days. Havent gotten through the most parts yet, but will try to see how much usefull info I can get out of it. I'm not technically educated, although I have had a lot of sciences (I'm a doctor), sohopefully I'll be able to plough through.

On 10/22/2019 at 2:45 PM, Ricci said:

In the case of the Skhorn and Skram variable tuning is an integral part of the design that I considered fundamental. That is why they have many smaller vents instead of a larger single. Also it is structurally very strong. When considering them as individual smaller vents they are not too far from square. 

Especilly in the Skram! The almost squares do help. But as you mentioned, primarly the area will be the determining factor. 

On 10/22/2019 at 2:45 PM, Ricci said:

Its all about the tradeoffs. I think you may be overestimating the effect a change to the shape may have on compression. A single square or even round vent the area of one of the Skhorn vents isn't going to gain much. They will still overload and compress. The area is not enough to cope with the demand once the sub is pushed at tuning. This is true of almost every sub tuned under 20Hz. In the Skhorn's native tuning with all vents open with 3X the vent area this isn't really an issue as the testing showed. At the end of the day it's all about vent area in my opinion. 

In the end I will probably end up building my adjusted Skram with the same port dimensions, as its proven to work well in the Skhorn, which should do it way worse than the Skram. Its just for future designs nice to know what is important and whats not. Looking at the Skram and Skhorn as a 'case-study' is important in that process. 

 

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Also @Ricci, how did you determine port length? If I go by the length through the center of the port (659,8mm+153mm =  812,8m) + 1/2 of the port height (135/2 = 67,5mm) I get 880,3mm, not the 857,1mm you listed in the parameters. 

 

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Ricci might have adjusted his inputs based on the measurements posted some time in the past, to match the measured response.

IIRC he said that the proximity to the back wall also pushed the port resonance down a bit, but I'm unsure how you ended up with an even longer port. I have not looked much into the Skram

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3 hours ago, peniku8 said:

Ricci might have adjusted his inputs based on the measurements posted some time in the past, to match the measured response.

IIRC he said that the proximity to the back wall also pushed the port resonance down a bit, but I'm unsure how you ended up with an even longer port. I have not looked much into the Skram

I went with the rule of thumb stating that a slotted port ( using the wall of the cab) should have its (height/2) added to get an estimation of equivalent port length. 

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32 minutes ago, Droogne said:

I went with the rule of thumb stating that a slotted port ( using the wall of the cab) should have its (height/2) added to get an estimation of equivalent port length. 

I saw that, but I think Ricci did the same

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19 hours ago, Droogne said:

Also @Ricci, how did you determine port length? If I go by the length through the center of the port (659,8mm+153mm =  812,8m) + 1/2 of the port height (135/2 = 67,5mm) I get 880,3mm, not the 857,1mm you listed in the parameters. 

 

I believe I described how I determine port length earlier in this thread, or perhaps it was the Skhorn thread. I can't remember where exactly. I use line sketches in SW's and previous experience to determine the functional length. I'll see if I can find the post. Edit: It was on page 10 at the bottom of my long post. 

I'm surprised that you have ended up with an even longer length.

 

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I've been messing with a more compact single 21" version more similar in size to the half Skhorn that was originally planned. It won't be drastically smaller but I'm hoping to chop a few inches off here and there without losing too much performance. 

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1 hour ago, Ricci said:

I've been messing with a more compact single 21" version more similar in size to the half Skhorn that was originally planned. It won't be drastically smaller but I'm hoping to chop a few inches off here and there without losing too much performance. 

I wonder how similar it'll be to my approach. Models like this from 320L external (21DS115):

Jv2im6K.jpg

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On 10/31/2019 at 3:19 AM, Ricci said:

I've been messing with a more compact single 21" version more similar in size to the half Skhorn that was originally planned. It won't be drastically smaller but I'm hoping to chop a few inches off here and there without losing too much performance. 

Ultimately this has to come at a cost to efficiency and/or extension.....

On another note, do you think you will ever finish the pale-horn design/drawing? Or do these hybrid designs totally supersede your interest now?( will be interesting to see the final analysis ie your measurements of an SKram loaded with 21sw/21ds vs the old othorn measurements).

Also this may have been covered somewhere else but whats the theory to these hybrid designs, obviously there is bass reflex... but how does the horn part work together with the bass reflex? There is the compression ratio working as a  cushion against the driver? What about the horn length, how is that fitting in?

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9 hours ago, menace said:

Ultimately this has to come at a cost to efficiency and/or extension.....

On another note, do you think you will ever finish the pale-horn design/drawing? Or do these hybrid designs totally supersede your interest now?( will be interesting to see the final analysis ie your measurements of an SKram loaded with 21sw/21ds vs the old othorn measurements).

Also this may have been covered somewhere else but whats the theory to these hybrid designs, obviously there is bass reflex... but how does the horn part work together with the bass reflex? There is the compression ratio working as a  cushion against the driver? What about the horn length, how is that fitting in?

HIL is still in effect. There's no way around it. 

I probably won't. The limited bandwidth of TH's or the added complications and size to the cabinet to be able to deal with the upper band resonances via tuned resonators limits their usefulness to getting much below 25-30Hz. IMO.

It's just my own variation on a 6th order bandpass mixed with a rear ported horn or whatever you want to call it. It's nothing new really, but the way I design them differs a lot from the way I had always seen them done. The most similar are pro audio designs with a big emphasis on the horn section and a port added to a relatively small back chamber. Not much extension below 40Hz. They are targeting being really loud >50Hz with those designs. There are some exceptions in the past couple of years from a few companies. In mine the upper section gets only a little sensitivity gain. It is mostly used for filtering noise from direct radiation of the drivers at high volume, lowering distortion a little and physical protection of the drivers. This leaves more of the cab volume dedicated for the low end where it is needed most. There's quite a bit more to it, but I've covered a lot of it in the MAUL and Skhorn threads. 

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10 hours ago, Ricci said:

HIL is still in effect. There's no way around it. 

I probably won't. The limited bandwidth of TH's or the added complications and size to the cabinet to be able to deal with the upper band resonances via tuned resonators limits their usefulness to getting much below 25-30Hz. IMO.

It's just my own variation on a 6th order bandpass mixed with a rear ported horn or whatever you want to call it. It's nothing new really, but the way I design them differs a lot from the way I had always seen them done. The most similar are pro audio designs with a big emphasis on the horn section and a port added to a relatively small back chamber. Not much extension below 40Hz. They are targeting being really loud >50Hz with those designs. There are some exceptions in the past couple of years from a few companies. In mine the upper section gets only a little sensitivity gain. It is mostly used for filtering noise from direct radiation of the drivers at high volume, lowering distortion a little and physical protection of the drivers. This leaves more of the cab volume dedicated for the low end where it is needed most. There's quite a bit more to it, but I've covered a lot of it in the MAUL and Skhorn threads. 

Thanks for replying that answered my questions...

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2 minutes ago, jay michael said:

Set up pic from our Halloween cabaret last night. Experimented with a 100hz crossover and found it to be the most impactful and cleanest config I’ve tried yet.  Techno and psytrance all night, sounded incredible. https://imgur.com/gallery/qrU6jyD

Good to hear they are working well with 100hz LPF. Does that mean you wont need the kick bins anymore?

What are the box things under your tops?

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I doubt it. Psytrance needs a lot of power and control in the kick and midbass range and the skrams deliver it without breaking a sweat.  Mind you the sh46’s pack a wallop themselves, matched up with the skrams its a potent combination.   I’ve been in front of enough f1 and turbosound systems that really excel at reproducing psytrance transients and my system doesn’t leave me wanting at all.  These Danleys continually blow me a away, I have no doubt Tom borrowed tech from recovered alien space craft 😂.  I have a stack of 6 reconditioned Martin Audio b115 front loaded horn kick bins as well, next summer I’ll give them a go between the Danleys and Skrams just to see what happens 

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21 hours ago, jay michael said:

Set up pic from our Halloween cabaret last night. Experimented with a 100hz crossover and found it to be the most impactful and cleanest config I’ve tried yet.  Techno and psytrance all night, sounded incredible. https://imgur.com/gallery/qrU6jyD

 

https://imgur.com/a/dacbWrI

Awesome. I wish you were closer to me so I could come to one of your events and get a listen of the Skram + SH46 combo. 

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I did a small test which might be interesting to some here, since the Tool album has been discussed here earlier (for the great dynamics with the Skram).
Not entirely bass-related, but I just got my new measurement mic and placed it 1m away from my drumkit to get an impression of the crest factor of actual drumming.
I hit some hard rimshots, which peaked at 143db(Z), but the RMS maximum in the measurement sat at 116db. That's a crest factor of 27db!
That aside, I would never like to listen to recorded drums at the same volume as I am playing at. I always rehearse with ear-protection since the cymbals are just way too overkill, especially if you have high quality cymbals with lots of overtones and sustain.

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Hello everyone, after following this topic from the beginning , me and a friend started building a skram about two months ago. The work was slow due to our limited woodworking experience but it's now near completion and I'm glad it's all fitting together. Thank you for the design mr. Ricci, I can't wait to fire it up.

We are building just one sub so we only used 18mm birch and I'm happy to say it is possible to get one skram out of two 2440x1220 sheets but only if the cutout of the hatch panel is used as the hatch itself (maybe there is a better way but we did it like this).

This is the first time I'm building something like this and although I have read this whole topic, I do have a few questions:

  • We'll be using the sub with our Nexo PS10 tops, which are protected by their Nexo td controller. We don't have the budget for a good dsp yet so we'd like to use the sub output of the td controller for our sub. The crossover point is 120Hz and the recommended power for the Nexo LS500 sub is 300 - 800W (also 4ohm like our 21sw152). I guess with the protection circuit of the td controller there is no chance we could damage our driver? Will it limit much too early? Will the 120Hz crossover work well? I know this isn't an ideal situation but we'll have to make it work at the moment and if there's anyone here experienced with the nexo controller, I'd like to know what you think.
  • Do you use some kind of extra seal to mount the driver or just bolt it on tight?
  • Is there a reason to mount the Speakon connector in the hatch? There would have to be a loose wire on the inside to make this work?
  • Do you solder the wiring to the driver and connector?

Thanks in advance!

image.thumb.png.041f694a51872b3eb911e54e1962150c.png

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On 12/5/2019 at 10:08 AM, Waynes said:

This is the first time I'm building something like this and although I have read this whole topic, I do have a few questions:

  • We'll be using the sub with our Nexo PS10 tops, which are protected by their Nexo td controller. We don't have the budget for a good dsp yet so we'd like to use the sub output of the td controller for our sub. The crossover point is 120Hz and the recommended power for the Nexo LS500 sub is 300 - 800W (also 4ohm like our 21sw152). I guess with the protection circuit of the td controller there is no chance we could damage our driver? Will it limit much too early? Will the 120Hz crossover work well? I know this isn't an ideal situation but we'll have to make it work at the moment and if there's anyone here experienced with the nexo controller, I'd like to know what you think. It should work but won't be ideal. A bit of EQ and flexibility in the low pass frequency and slope will help to dial it in better. The driver should be relatively safe with that amount of amplifier but I'd not assume that it is indestructible.  I've learned that nothing is impossible. 
  • Do you use some kind of extra seal to mount the driver or just bolt it on tight? Just bolt it tight. The front gasket on the driver will seal well. 
  • Is there a reason to mount the Speakon connector in the hatch? There would have to be a loose wire on the inside to make this work? The hatch is the easiest place to put it. It's on the back of the cab and if you need to make wiring changes or check connections it's easy to take the hatch off. The wires can be secured with enough slack that they will not contact the cabinet, or you can wrap the cables in foam or fabric if you think it may vibrate on a cabinet wall. 
  • Do you solder the wiring to the driver and connector? I don't. I use crimp connectors and spades usually. Some people prefer solder. Either will work fine. 

Thanks in advance!

See above. 

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Another successful outing with the Skrams. Bit of a tough room acoustically, vaulted ceiling log A frame hall with concrete floor out in the Alberta Rocky Mountains.  Scratched our heads for a few hours but eventually got it dialed in, helped a bunch once the room was packed. 2 more cabinets are near complete, still needs duratex and drivers mounted 

 https://imgur.com/gallery/mRXr2Tr

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Finally had some personal time to make some chips.  Dry fitting the first one before moving on to cut the second one.  Thanks for the design Ricci!

Are you all using any acoustic foam inside the skrams?

 

pictures or it didn't happen:

skramcad.thumb.png.f7e0056dfdbd04a23fe3cde7ab9c0592.pngskramcam.thumb.png.8b99057c6c8e69833f8a92c1830fe5b5.pngcncside.thumb.jpg.ba858fa52b42b4419b0933fd93e2f0bd.jpgdryfit1.thumb.jpg.6ba7573a80592fe69696efc3deb2e452.jpgdryfit2.thumb.jpg.6a464249e7589433c6838773b32fded6.jpgdryfit3.thumb.jpg.640dbce2c796a1ba906a9e6196f19217.jpg

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On 12/24/2019 at 8:40 AM, klipsch said:

Finally had some personal time to make some chips.  Dry fitting the first one before moving on to cut the second one.  Thanks for the design Ricci!

Are you all using any acoustic foam inside the skrams?

 

pictures or it didn't happen:

skramcad.thumb.png.f7e0056dfdbd04a23fe3cde7ab9c0592.png

Looks great. Yes I would use some lining in the vented section of the cab. Do not use any in the front section. Just make sure to clear the vents well.

Happy holidays.

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