Revolt Sound

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

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.

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?

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.

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.

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

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? 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?

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