peniku8

23 hours ago, jay michael said:

Cant stop, wont stop.

Whoa those edges look rough. No compression bit used here?

13 minutes ago, klipsch said:

With all of the vents open, maybe start off with a 24db BW at 30hz and 110hz respectively? 

A sharper slope could be used on the low end if really pushing the cab/driver. On the higher end, it really depends on your mains. 

I typically like to grab the HR sim and use the filter wizard so that the maximum excursion below tuning doesn't exceed the maximum excursion above it. With a 4th order Butterworth that typically lands a few Hz below the tuning point, which is around the same point as you suggest, for this cab's native tuning of 30Hz.

Draw a 1:1 sketch onto the wood (optional but helpful). Then make a 6° jig for the table saw and cut it where it needs to be cut

15 hours ago, lawbadman said:

Question for the more proficient woodworkers here.

Referring to baffle brace J in the construction plans.

I don't have a CNC machine, I only have a table saw, circular saw and jig saw. My tools are usually only good for square or rectangle cuts.

Can anyone advise me on the best method/trick of accurately making the 6 degree angle cut (on the right side) with the tools that I have? Its a tricky cut with the tools I have...

 

Thanks

I couldn't help myself...

1 hour ago, Lex breijs said:

Upon completion i would like to submit measurements. I think i have everything (software, calib. mic., mic, stand etc) Could anyone point me in the right directions on a step by step measurement process?

I know theres a big chance this thread is dead, no one will be reading this but im trying anyway and like to thank Josh again for the nice drawings.

Here is a small guide of what you need to obtain accurate measurements of a subwoofer:

Equipment:

• Microphone with a known frequency response (ideally an omnidirectional mic, something like a UMIK for example, but technically for this purpose any microphone with a calibration file for on-axis (free-field) sound will work)
• Audio interface
• Amplifier
• DUT (Subwoofer)
• A computer with REW, ideally something portable

Measurement process:

• Calibrate your electrical chain (I'd personally not recommend this step to beginners as it's possible that you'll be making things worse. So if you don't know how to do this you can omit this step, since it's likely not gonna make a huge differency anyways if you have decent gear)
• SPL calibrate your mic (not needed if you just care about frequency response)
• Find a suitable open space to obtain your half-space measurements in. This means outside on a flat surface with no objects within a certain distance to your DUT (say ~10m or 30ft; parking lot for example or your backyard if it's large enough
• Place the subwoofer in the intended configuration with the radiating source (aka reference axis) towards the microphone
• Place the microphone one the ground and at least 4 times the widest dimension of the baffle/frontal area (typically diagonal) away from the cab, which would be about 4m in your case
• Take a measurement sweep in REW. Start with a low level to avoid mishaps and define a sensible sweep range (for example starting two octaves below the expected tuning point and ending two octaves above the intended maximum usable frequency, which would be something like 10Hz-500Hz in this case)

Interpreting sweeps is an entirely different topic, but I hope I didn't forget anything here so you can obtain some high quality data!

16 hours ago, heresyreznor said:

I can get the B&C 21SW115 for quite cheap on sale, is there any significant downside as opposed to using the 21DS115?

no, go for it.

17 hours ago, Bionico said:

Hi Robin,

I already noticed last week that you are selling yours and I also knew this customized copy from your making of documentations in the AVS forum. It’s a really nice piece of work and the customized look fits to your other components.

I first considered your enclosure as an option, but finally realized there are just too many mismatching points for me:

-          I really like the look of the integrated handles on the sides, the top and the bottom. I fully understand they were omitted when not using CNC

-          The vinyl painting wouldn’t fit for me and I have no experience in removing it for a repainting

-          My Eminence NSW-6021-6 have a smaller Bolt Circle Diameter and a smaller Baffle Cutout Diameter than your previously owned B&C 21DS115

Beside transportation costs from Saarland to Hamburg at least the latest point on the previous list is a knock out criteria.

I mean, these are all problems that can be solved. If you pay me a bit extra I'll modify the cab to your liking and then you can compare my price to the CNC quote you get Shipping would be around 100€, looking at a quick google search. I would just prefer to not have to paint it (the vinyl wrap can just be ripped off). But you'll have to get yours painted too, so either way you'll have to figure that out.

3 minutes ago, Bionico said:

After reading so many convincing posts and measurements about Ricci’s Skhorn, it was only a question of time until I desperately want to have one of these.

I already have two Eminence NSW6021-6, each one running in a self-made 200L ported enclosure and each one driven by a bridged FP14000 clone. The enclosures work, but I am convinced that the drivers are running far below their potential and I’m also not really satisfied with the sound characteristics.

Meanwhile I was lucky to find a nearby CNC shop in Germany willing to build one for me. They asked for metric version measurements and I found a pdf with metric drawings in the original post. After a closer look it turned out that these drawings provided by Robin Mahler (peniku8) were created for building without CNC and contain various design changes.

I really like the design change to build the braces in one piece and with holes as done by dsl1 for his CNC version.

@dsl1: from all versions I have seen so far, yours is the one I like best. May I kindly ask you to share your files, knowing that my local CNC shop might still have to do some adjustments to consider material and cnc setup.

Or is there anyone who already built a Skhorn with CNC and metric sizes?

Wait, you're in Germany? I'm selling my Skhorn, without the drivers. I'm in Germany too, hit me up if you want it

Well just think about it.. the port is how wide? 600mm? Now you increase bracing thickness by 18mm total (three braces iirc). So you lose 18mm of port width from your 600mm which is 3%. Make your port area 3% smaller in hornresp and see how much the response changes (hint: no).

As the title says, I'm selling my Skhorn. I took the drivers out and built single driver subs with handles for PA use, because I don't have space for a subwoofer anymore after moving. As such, I'm just selling the cabinet without the drivers. The port blocks are still installed.

Plenty of pics here:
https://www.avsforum.com/threads/skhorn-build.3037204/

Asking for 1000€, that's about its plywood cost atm (18mm BB). Fixed price, for anything less I'll rather keep it.

I live in Germany near Luxembourg. No shipping, unless you handle everything. I have an epal pallet which I could put it onto. Would charge 50€ extra for that.
I can not transport it either, so it must be a local pickup. Has 4 wheels installed on its back currently to move it around easily.

Heya, I wanted to update this thread with my recent findings comparing straight ports with shaped ones from two 21" subs.

I build two cabs of identical size and tuning loaded with 21DS115-8 drivers, where one cab has a straight port and the other one has a port with continuously changing area. The shaped port has a moderate ratio of 2.5 (largest to smallest area).

I put both cabs up for compression sweeps at 2m half space and the results are quite interesting.

Port compression is visible at around 20V for both cabs, but I don't care much for fractions of a dB of compression. It starts getting interesting at 64V, where the shaped port went 0.5dB into compression and the straight port was at 1.5. The difference remains 1dB at 90V, but now we see power compression starting to kick in as well, centered at around 75Hz.

Here are both cabs at 128Vrms input:

The difference is still around 1dB at tuning, but now we see a stark difference of around 2dB near 70Hz. The cab with the shaped port behaves much better overall producing a smooth curve, which would still sound excellent at those levels, while the straight ported one starts being kinda all over the place.

The difference at tuning is easily explained: the aerodynamic port reduces 'air resistance' so the cab is more efficient there. The expansion at 45Hz I can explain too, or at least speculate: This is where impedance and particle velocity is high, which means no power compresison in this region and vortices forming along the surface, reducing friction with the cabinet walls. The dramatic difference at 70Hz I have no clue. The port does nothing at that frequency...

Interestingly, the sweeps at 181V look similar, because both drivers are heavily into power compression at that point, but the shaped port wins out by 1dB on average.

Distortion looks pretty similar across all levels, except for the 128V sweep, where the cab with less compression also has quite a bit less distortion (around that 70Hz).

So, conculusions.. It looks like overall a shaped port can extract 1-2dB more out of a subwoofer of a given volume, depending on which frequencies you need for your application. The cab with the straight port performed almost identically from 40-60Hz, but for other frequencies, it might be the difference of bringing 6 to bringing 8 cabs to a show.

On another note: hornresp predicted this subwoofer's max output at 44Hz to be 124dB (1m full space), limited by Xmax. But I measured 129dB (2m half space) with just 7% THD... 5dB is a pretty big difference, especially since hornresp doesn't factor in any sort of compression...

Randomly came across this old topic and I thought I'd elaborate on what (probably) happened here, in case someone comes across this in the future:

Some amps have their 2nd channel running double reversed. Their input phase is flipped and then the output wiring is also reversed, flipping the phase back. This seems to make it easier on the power supply, since one channel generates a positive voltage swing, while the other goes negative, creating an overall balanced load on the PSU. It's kinda like running bridged.
Since the output wiring is flipped on channel two, 2+ will be neutral. And since both channels are running on the same PSU, ch1 and ch2 have a shared neutral, which means you're running 1+ and neutral, essentially the same as 1+ and 1-. If you hook up 1+ and 2- while feeding both channels the same input, you're running bridged (differential) automatically.

20 hours ago, jay michael said:

These amps conveniently have power factor correction, so they will take what ever voltage you throw at them reliably

I was under the impression that the variable input voltage thing was a doing of the SMPS itself, not PFC. Are you sure these amps have PFC?

12 hours ago, chrapladm said:

Where can I find out more info on this said device?

I got an email from them announcing the D-3004 with 4x8600W@2Ohm but in the follow up mail their rep said that the amp isn't really 2Ohm stable lol. But if it really performs up to spec, you could run 3 Skrams per channel for a total of 12 cabs off of a 1U amp, which would be pretty sick. But of course pushing the amp pretty hard.

Nice endfire setup! I'm in the process of building a 4th sub (not Skram but also 21") and will bring all 4 to a wedding next month. I also got a mail from CVR that they released a new 35KW 1U amp. Would love to test it but can't really justify buying stuff just for fun yet lol!

Nice! Now you just need to get appropriate amping and the setup will slay.

Btw, it's called "infrasonic" (sound), not "subsonic" (speed)

25 minutes ago, Domme said:

It's no easy project at all. I have some woodworking experience, but not too much, and had some help from a friend master carpenter and it was still a PITA to get it all right. Without his help I probably would have messed up the glue step because you need to be quick! Those huge surfaces are not easy to move around once you apply glue and it's almost the last step and you can still mess everything up... you also need strong clamps and MANY of them.

I would probably order all parts CNC'ed next time because even though it was worth for the experience and learning, when you count man hours it wasn't worth spending hundreds of hours just to save a bit of money. Anyway, good luck!

If you have an air compressor, buying a brad-nail gun is a better investment than buying clamps imo and it makes building the cab way easier.

If your cuts are clean and you don't have to use construction glue, that is the best solution. Danley does it like that. If I didn't buy a large press to put the whole speakers into, I'd do the same.

If you really want to use clamps, I can recommend to buy extruded aluminium to spread the clamping force over the length of the edges like I did in my Bordeaux build:

Wow, is this a spam post written by ChatGPT?

12 hours ago, Derecaston said:

Choosing the right subwoofer can be a tough decision, but you've got some great options in mind! The Captivator 4000, RS2, and Pro18 are solid contenders. It'd be awesome to have some graphs and measurements to make an informed choice, right? For your theater and music playback, those low port tunings and high SPLs sound like a fantastic combo! While the thread might be a couple of years old, the quest for the perfect subwoofer never gets old! You could still check out audio forums or websites like d20 roller, where you can find a dice that will help you make the choice.

3 hours ago, rolo95 said:

Guys,

impressive work each and everyone who built the SKRAM

i have a couple of questions

1.- How many dB get lost  if i get the least expensive driver from the list , the Lavoce SAN214.50 or the RCF LF21N551

2.- what router bit is used to trim the 90 degree angles in the outside of the box where the outside panels meet to each other, so to look more pro factory made cabinet with chamfered/rounded edges

3.-  do you guys use any method so to stack 2 or 3 cabinets and some feet or corner cover that fits in to each other cabinets so to "lock" and do not let the cabinet run or fall when stacked in top of the other.

4.-  what area of the back driver chamber need to be filled with ikea pillow stuffing ?

5.-  is best to use the 8 ohm or the 4 ohm version?, i plan to run 2 8ohm drivers in paralel for a 4 ohms load in to the amp channel, im not confident enough to run @ 2ohms load regardless

6.-  do you need a CNC machine to cut the wood or you can make one with just a table saw.

 

1. the LaVoce is a perfectly adequate driver. If you're in the US, the Eminence driver will output like 2dB more. In Europe the price difference doesn't make any sense

2. a roundover bit

3. I machine circles in the top of the cabinet where the (round) feet sink into

4. uh none; you can line the walls not near the port with foam if you like

5. you answered your own question

6. that's up to how good your woodworking skills are - I built an SKhorn without a cnc

I'm probably going to sell mine; you don't happen to be in Germany? lol

Sealed subs are not suited for live sound applications. They won't have enough headroom down low

6 hours ago, Lab_Experiment said:

Linear Frequency response is not the same beast as Linear Frequency Volume response. If you're replying please understand the distinction. I know it can be confusing.

What you're talking about is compression and expansion.
There are a lot of factors that can cause compression in subwoofers (a change in input gain results in a *smaller* change in output change), like the voice coil getting hot (impedance rises, so the same amount of voltage generates less power; also known as power compression), air velocity in the port getting too high (port compression), the driver reaching excursion levels where the magnetic field strength gets lower (over excursion) or simply the amps' limiters kicking in, to protect the drivers from destroying themselves.

To express the effects of compression with your wording it could be something like:
-volume change from 70% to 75% is very large
-volume change from 75% to 80% is small
-volume change from 80% to 85% is imperceptible

Since you describe the opposite effect, if I undersood you correctly, this doesn't apply, since you're seemingly describing expansion.
There is only one cause of expansion in subwoofers that I am aware of and it is minute.

So, if expansion doesn't happen inside a speaker, what's the thing you're hearing?
I think the explanation is fairly simple: it's the lack of compression. You're not used to hearing capable systems that can reproduce content with their full dynamic range, in which case the SKHorn would be one of the worst choices, since it's one of the most capable subwoofers out there.

Another explanation would be bad deployment and what you were hearing at "75% volume" wasn't the subs being super loud, but everything distorting badly (which will be perceptually louder, since our hearing is more sensitive at higher frequencies and distortion will mostly produce frequencies higher than the stimulus).
Most venues and festivals I mix have underdeployed systems and/or are badly set up. The last festival I mixed at had a stack of 3 2x15" subs on either side of the stage. All three cabs were different, which was the first point of concern, but the biggest issue is the physical deployment: you get terrible lobing and super uneven bass response across the audience (see my recent post on AudioScienceReview on this topic).

I haven't experienced the effect you're describing. Most of the time I'm fighting compression and uneven response across the audience.

The issue you're describing can have many causes, but "subwoofers being overly dynamic" it is not.

7 hours ago, Lab_Experiment said:

2. Was the unilinear volume response amplifier related or speaker/box related?

My answer to that question would be "source content" as per the explanation above (lack of compression; habitual).

7 hours ago, Lab_Experiment said:

3. If I build a SKHORN will it only sound good when I'm pushing 4000 watts?

The difference between 1000 watts and 4000 watts will be 6dB in theory. In practice, some compression will have set in at 4000 watts of input power and it will be less than that at certain frequencies.

Cool video, I haven't seen that before. Gotta do this too, been too lazy to phase align my PAs but I really should.
The alignment tool in REW looks super cool, this is the first time I see it. I used to take a bunch of sweeps changing delays until things looked right lol.

Btw you don't need to run the timing reference to a speaker, you can do a straight (electrical) loopback instead.

When integrating multiple drivers via dsp in speaker designs, I do it in the following order:

1. Apply corrective speaker/driver EQ (minimum phase)
2. SPL align
3. Apply Xovers
4. Take another measurement of the individual components/speakers now with everything that changes phase already applied
5. Phase align
6. Take another measurement for validation

And then when the PA is set up I'd probably align the PA with the Snare drum, because that will likely be the loudest sound coming from the stage and in smaller venues that will actually dominate the overall sound. Not applicable to DJ gigs of course, but something to keep in mind if you're working with acoustic sound sources.

I'll be rocking Powersoft soon so I'm looking forward to getting all of this running.

6 hours ago, Leimahmood said:

i have four skram box in my theater room and two port block tune to 20hz iss there any specially eq needed the driver used is b&c 21SW152 4ohm

yes: room eq

Why the double baffle? What's your panel thickness?

4 hours ago, kipman725 said:

I was trying to avoid audio connectors so that the wrong cable didn't get plugged in. 

We are building 8 Skrams at the moment with B&C 21SW152.  I notice the suspension is super stiff out the box on these drivers but finding the space to do any kind of free air break in is a challenge while also building the subs.  Does anyone see an issue performing break in with the driver mounted in the subs and the hatch removed?  also failing that I guess break in is actualy not that important and will occour with usage?

should be fine since the horn loading isn't a high-pressure loading so it should almost behave like in free-air

just take an impedance sweep, set the sine wave to the resonance and give'er

should be good to go after a few minutes near Xmax

and yes, it'll occur with usage, but you'll have to do a few gigs before you can set up the system properly with measurements n stuff, because calibrating the system with subs that'll be slightly different each gig doesn't make much sense