Revolt Sound

5 hours ago, jay michael said:

Hey guys.  I've been experimenting with crossover points between a single Skram and a single Danley Sh46 in my living room over the last couple of weeks.  I had never considered pushing the crossover point up higher than about 100hz but I am currently running a 125hz crossover point using BW24 filters and I can't fault the sound at all, in fact I think I am preferring it as sounds noticeably more dynamic and visceral.  I can't tell for sure if this would translate the same at war volumes due to my smallish living room but it has me thinking more about experimenting some more.  I am currently using the 24db BW filters as that is what is recommended in the Danley DSP recommendations but I'm wondering what the differences would be in trying some other settings.  I don't know enough about crossovers to really know how they are going to effect the sound other than trying to objectively listen to the differences.  Just curious if anyone has any input about this subject?  My initial thoughts around keeping the crossover lower around 100 or so is that the SH-46 can easily get down into 80hz with no problems but I think the Skrams will provide more energy in the 80 to 125 area.  What do you think would happen if I tried a different slope, something not as steep as a 24db, maybe something like a 12db or even less.  Would that allow more sharing of that bandwidth between the Skram and the Danley? Could that maybe improve or hurt the potential output?  I've gotten a pretty solid grasp on time and phase alignment so I am less afraid of allowing more sharing of certain frequencies between the two different cabs.... I am just not sure if this is a thing that people do, or if it is recommended at all.  I guess my thinking was that in scenarios where the 46's are placed further away from the subs the 46's would still have output down into the lower frequencies rather than being cut off sharper at 125hz from the 24db slope. Any thoughts?  

I would highly recommend reading the attached white paper that was written by Paul Williams on crossover filters and there characteristics. Paul is responsible for the  DSP algorithms in Linea Research products. 

CrossoverFilters White Paper -C.pdf

4 minutes ago, jay michael said:

SPL and Phase

 

Looks very close to my SK horn measurement. I would be very interested to see the same measurement with all 4 cabs. One with the ports in the center and one with the ports on the outsides.

Ok so it was an air leak that is causing the noise problem. It was coming from one of the un used t-nuts for the different drivers we will be testing. 

15 hours ago, Ricci said:

The measurements look good. That's a smooth response from 30-150Hz with no smoothing or processing. Looks right. Were these taken outdoors?

I'm not sure what to say about the noise. I don't recall anything like that from mine. All of the air noise I've encountered is from the ports at really high output near tuning. When airspeed gets high. The horn section has a lot more area and the airspeeds are a lot lower. I wouldn't expect anything like that especially at lower volumes.  Could be an air leak, a loose panel, wire touching the cone, or a driver issue. Might be worth double checking that everything is sealed good and tight especially at the driver mounting area. I never put any material in the upper section of mine. Is it something that you hear with you ears close to the cab or something that is audible from 10+ feet away? Is this with the low pass filter in place?

Hi Ricci,

Yes measurements were outside in a field, closest building was about 15-20m behind the cab.

The noise is present at low power (around 500-1000w) and can be heard at 10+m away as an annoying artifact but when you are next to the cab its more of a noisy rattly sound . I have a suspicion that it could be an air leak from the unused bolt holes we put in for different drivers, I thought that the foam gasket around the driver would do a good enough job of sealing them. It could also be the cables that we have ran through the horn to the other driver chamber. I have the day off on Thursday so im going to check everything and try again. 

Ok so took some measurements with the 18 Sound NLW9601 today. 

This one is the unfiltered response:

This one is with HPF 24Butt @25hz and LPF 48LR @120hz:

There is no smoothing on the magnitude or phase traces and all vents are open. Next time I will EQ out the lump at 208hz and try a less sharp LPF.

When playing music there seems to be quite a bit of noise coming from the horn mouth (not good noise), has anyone els experienced this? this seems to be present at low  power and is much more obvious at higher power (around 3600w) Have we messed something up? I have wadded the rear chamber and there is no noise at all from the vents on the sides. Do we need to add wadding to the front middle vents of the cab? It almost sounds like the drivers are moving too fast and the air can't escape, I'm not sure.

The noise aside, the sub and bass from the cabs is really nice, very fast, deep and effortless.  I will be going back on Thursday to try and find the source of the noise, any suggestions are much appreciated. 

Ok so cabs are finished, I have the 18Sound drivers but will have to wait about 3 weeks for the RCF and won't have my hands the B&C until next week. Will update with 18Sound results over the weekend.

Could anyone please tell me what %THD I should expect to measure at high SPL with these cabs?

2 minutes ago, radulescu_paul_mircea said:

Can't wait to see your comparison results, to compare them to mine. I don't have the NLW9601 driver, this should be extremely powerful and efficient

The 18 Sound driver is the one I am hoping to perform the best as I get the best deal on it, we will see though.  

Following

Some progress shots. We have decided to do a shoot out between the B&C 21SW152, RCF LF21N551 and 18 Sound 21NLW9601. I will share the measurements and results in a couple of weeks.

54 minutes ago, Ricci said:

Hmm. Man I think its splitting hairs. Should be fine. Your talking a couple hertz tuning difference if that. The vented chamber is relatively forgiving of small changes. Id say roll with it.

We decided we are going to just make the vents wider. Going to start cutting at the weekend.  

The second option was a port width of 87mm and port length of 595. After replacing the 12mm ply for 18mm the last 35mm would be split between the rear chambers.

1 hour ago, Ricci said:

I did some quick modeling and it looks like the tuning would come in at about 31.5 or 32Hz from the original 28 or 29Hz tune. A little more than I had guessed, but the response doesn't change much. It looks good. I'd say this modification would be barely noticeable if both were side by side and you have a little extra vent area. Go for it. 

Thanks Ricci, was this for the simple mod of making the vents wider or the latest mod I posted with wider and longer vents?

9 hours ago, SME said:

Assuming I understand the dimensional drawing, the ports are 3" (76 mm) wide, so adding 30 mm to each side would make the ports 140% bigger in cross-sectional area.  Vent tuning frequency scales with square root of port area, so tune will be ~118% or around 1/4 octave higher.  That's like 35 Hz vs. 30 Hz.  This assumes a pure vented alignment, and I'm not sure how the 6th order aspect will come into play.

So we did some calculations and think this should give pretty much the same response as the original.

Depth and height of the cab will stay the same but the overall length will be 1440mm. We will also be using 18mm ply for the whole cab so we have taken that into consideration. Do you think this will work how we intend it too? 

27 minutes ago, radulescu_paul_mircea said:

Regarding limiters, for pro use, I suggest to make use of all of those limiters. The X-max limiter is excellent to be used when you force the system and you hit the peak limiter or maximum voltage quite hard. It will help you with keeping the high pass where it should be no matter what the input stage is doing.

Thats right, if a mic gets dropped on stage or someone unplugs something when they shouldn't it offers some protection but mainly its for protection against rubbish DJ's that like to have the mixer in constant clip. I regularly use the VX and Tmax limiters and I have never fried a driver and with the kind of events we do we get to really push the limits of our cabs. Here are some 44M20 logs from a 3 day festival we did last September, the first one is the whole device and the last 4 are the individual channels. we were driving 4 8r Beyma 18p1200nd per channel all channels driven with the same input/output settings.

We will be using Linea Research 44M20's to power these, Im planning to run 2 drivers per bridged channel at 4r. The DSP has 3 different limiters, voltage, thermal and Xmax. I usually use the peak rating for the voltage limiter and the RMS rating for the thermal limiter. I haven't played around with the Xmax limiters yet but its something I will defiantly use on these. 

Also I would like to ask if its is possible to make the cab 60mm longer? I was thinking to make the ports on each side 30mm wider so that 2 of our low mid horns stack perfectly on one SKhorn laying down on its side. What affect would this have on the tuning and performance do you think?

On 2/16/2019 at 2:09 PM, radulescu_paul_mircea said:

RCF LF21N551 arrived and tested. The driver is extremely well built, it is more powerful and efficient than my 21SW152 and the parameters better matches the SKHORN XL enclosures. The BL is pretty close to the specs, the excursion capability is excellent, with 18 mm gap and 39 mm dual layer inside outside coil, better but noisier cooling strategy. The triple point joint is reinforced with epoxy resin and the leads are glued to the spiders . The mechanical noise doesn't really appear even at 5.5 cm peak to peak excursion in free air but the turbulences are loud. I recommend it in these enclosures with all my heart.

I can get a better deal on the RCF than the B&C. Did you try them in the SKhorn?

We have been tuning it for 5 years 😅 We spent a lot of time on it last year. There are a few all pass filters needed to align out of band phase and we now use FIR filters from about 500hz up. 

Thanks Ricci,

I will look into the Lavoce. Reason I was keen to know the difference between the 21 and 18 is because I can get 2x XL2000 for the same price as 1 B&C 21SW152. It wont be too hard to make baffle reducer to test the XL1600 that I already have and put them up against the B&C in an a/b test just to see if the extra £/$ is worth the difference in output. I can also get a good deal on 18Sound. Was looking at the 18NLW9601, how do you think it looks? I will be able to get some to demo. Also have you ever had any problems with drivers failing or over heating when running for long periods?

It looks like my cab builder is going to be making a start on the first pair next weekend so I will post some updates if people are interested?

Hi all,

We are thinking about building 8-10 of these, we are based in the UK and mainly cater for outdoor festival stages playing sub orientated dance music up to 2-3000 people and club events of around 1000-1500 people. 

Im slowly working my way through all the information there is on this design on all the various forums. While I am doing so I would like to ask some questions if that's ok:

What should I expect if i was to run a stack of 4-6 of these? has anyone done this? 

I can get very good deals on Faital Pro drivers, has anybody tried or got a sim of the XL1600 (I have 4 of these already) or the XL2000? 

Is it correct that the cab size is the same for an 18" driver and a 21" driver?

It is my understanding that the B&C 21SW152 is the best driver bar the Ipal, how much of a difference in output and low extension would there be between the 18" Faital and the B&C 21SW152? 

Some of these questions I'm sure there are answers to that I've not come across but though I would ask at the same time as reading as it could be quicker.