Tops / Bass x-over settings for night club PA...

[Brian Steele]

Guys, need some help here.

Situation:
Place:
Night club (volume is about 45'*50'*20' high).

Tops:
4 x passive CV 3-ways, 15"/6"/1" horn, 40 Hz Fb, good down to about 70 Hz
2 x Mackie active 2x15"+1" horn, unknown Fb, unknown F3
All wall-mounted about 6 feet up, facing down to the center of the dance floor.

Bass:
2 vented "W-bin" 18" horns, B&C drivers, vented @35 Hz, corner-loaded

Equipment:
Mixer->Aphex Aural Exciter->dBX compressor->DriverRack PA->amps + active speakers.


I found the DriverRack PA with the following settings:

Sub:
HP @20 Hz, 6dB/octave
LP @ 50 Hz, 12dB/octave
Gain: +8.5 dB

Mid (feeding the amp that's driving the CVs):
HP @200 Hz, 12dB/octave
LP @20kHz, 12dB/octave
Gain: -10dB

Highs (feeding the active Mackies)
HP @ 160 Hz, 12dB/octave
LP - passthru
Gain: -5dB

Does this sound "right"?

I've been in the club a few times and to me it's missing that upper bass "hit", and from those settings I think I might know why.

From the settings, it looks to me like:

1. The tops are crossed over way too high. Should be around 80 Hz or so. Maybe even lower, seeing that they're vented.
2. The sub's HP filter is way too low and shallow. Should be something more like 30 Hz @ 24dB/octave
3. The sub's LP filter is way too low - should be around 80 Hz, but adjusted to match where the tops start falling off.
4. Gains on all channels should be set to 0dB and the gains at the amps (and active speakers) adjusted accordingly.

Am I on the right track here? I may be heading down there tomorrow with my measuring equipment to see how I can help sort things out. BTW, any ideas on what sort of "house curve" I should aim for, when measured on the dance floor?

[billfitzmaurice]

Re: Tops / Bass x-over settings for night club PA...

From what I see there's a LP on the subs at 50Hz, and HP on mains at 160hz and 200Hz. That leaves a mighty big hole from 50 to 160Hz. Illogical to say the least.

[Brian Steele]

Re: Tops / Bass x-over settings for night club PA...

From what I see there's a LP on the subs at 50Hz, and HP on mains at 160hz and 200Hz. That leaves a mighty big hole from 50 to 160Hz. Illogical to say the least.

Yup, that's the first thing that stuck out at me. That, and the 13dB of gain difference between the sub output and the tops. The original subs used to be some old CV 18" FLHs, and were then replaced by some DIY "W" bins of unknown design parameters. I'm guessing that the LP on the subs may have been chosen to cut the upper bass response and make them sound more like subwoofers, but it's just a guess. In any case, it doesn't explain the somewhat high HP settings for the tops, particularly considering that they're 15" drivers.

I think I'm going to start with a "standard" 80 Hz LP on the subs / 80 Hz HP on the mains and then use my RTA to get the best match between the subs and the mains. Maybe even push it a bit lower, consider that there's a total of 8 15" speakers in the tops, vs just two 18" speakers providing the bass.

For the "house curve", should I aim for flat curve, or a bit of boost in the bass response?

[Brian Steele]

Re: Tops / Bass x-over settings for night club PA...

Another thing - these 18" "W" bins are tuned to 35 Hz with two 4" vents. I suspect some major port compression is probably happening at higher volumes. I'm trying to convince them to go with some DIY THs instead. Those nice B&C drivers deserve better enclosures. And perhaps double-up on the number of subs too. They just bought an iNuke 6000DSP to drive them. They were about to go with the 12kW version, but I told them that might not be a good idea, considering that they were feeding everything from a 6kVA transformer... :-)

[sn95]

Re: Tops / Bass x-over settings for night club PA...

some of the w horn boxes actually play pretty low and have pretty good efficiency obviously will depend on the design and build quality. from everything I've been able to read on the CV they don't appear to have anything below 50 Hertz and by today's standards is really just in general bass box and not truly a sub

[billfitzmaurice]

Re: Tops / Bass x-over settings for night club PA...

some of the w horn boxes actually play pretty low .

Some do, but the original 18" W horn designed by Don Keele for JBL, upon which most of these are based, only had a 60Hz f3. That was fine in 1977 when he designed it, but not today. The advantage to a W horn is large mouth area, which gives high sensitivity, but it comes at the cost of the path length necessary to go low.

[sn95]

Re: Tops / Bass x-over settings for night club PA...

you are absolutely right Bill just like the CV . I think and install is a perfect application for a horn where size and weight is not all that relevant.

[Brian Steele]

Re: Tops / Bass x-over settings for night club PA...

Well, I spent a good 8 hours working on getting that system "right". I'm close, but not quite there.

1. Hummmmmm! Looks like it's coming in from the old mixer. There seems to be some sort of channel imbalance as well. They've got this arrangement where the DJ's mixer plugs into this old mixer, then into the aural exciter, then the compressor, then the DriveRack PA. As nothing else plugs into the mixer, I'm thinking of just taking the damned thing out of the loop and either doing DJ Mixer->Exciter->Compressor->DriveRack, or DJ Mixer->Compressor->Exciter->DriveRack. Why keep the old compressor in there when the DriveRack PA provides the same functionality and more? Well, it's got a "gain" knob, and it's easy to show someone to turn a knob than to instruct them how to go through the DriveRack PA's various settings, LOL. For the moment, to minimize the audible effect of the hum I've reduced the gain on the compressor and changed the threshold limits on the DriveRack PA to +20dB and turned down the gain on the amps - basically ensuring that the signal from the mixer has to be pretty high wrt the hum.

2. The iNuke 6000DSP is a ficking BEAST! It really lit up those subs. As I thought, the boxes those 18" drivers are in are not adequate to keep the low bass going once the volume's pumped. My brother's eyes lit up when I connected the amp to the cheap 15" subs I made for him some time ago using Dayton PA drives and the old CV cabs with DIY big square vents tuning the boxes to 35 Hz each. Nice, clean low end. The 18's definitely beat them on impact however. Oh, and not only was there that funky 20 Hz ~50Hz bandpass filter set on the subs by the DriveRack, There was also a good deal of "smiley EQ" applied to the signal as well via the same DriveRack PA, all the way down to 30 Hz which the subs had no chance of producing seeing Fb was above that. And the reason the LP filter was so low was because the damned box panels were flexing audibly at higher x-over settings (sigh). I settled for a 32 Hz-63Hz 12dB/oct bandpass on the sub and a "brickwall" 30Hz 48dB/Oct HP filter on the amp. NOTHING is getting past below Fb. I might go back and remove the HP filter on the DriveRack's subwoofer output in my next rounds of tweaking.

3. I couldn't get the tops to sound "right" even after hours of tweaking and RTA-ing. Then my brother tells me that the horn in one of the main tops (the amplified Mackies I referred to earlier) was blown. Idiot, LOL.


Plans for next rounds of tweaking:
1. Seek and destroy the blasted hum, even if means retiring the mixer from the loop
2. Clean up the gain structure (no need for something wonky after the hum is addressed)
3. Incorporate the 15" subs into the system (I can see that's going to be a challenge - 18" horns + 15" vented boxes)
4. See if the damned Mackie with the dodgy horn can be fixed
5. Clean up the EQ and subs/top x-over points (currently set at 63 Hz /120 Hz -seems there's a little "room boom" around 100 Hz that shows up at lower HP filtering on the tops.


Oh, did I mention that all of the amps were fed from only the L channel outputs on the DriveRack PA, even though it was set to "Stereo" mode?

Finally, the subs are capable of going a bit low, but the sound more like "hit" boxes, if you know what I mean. Still, the RTA says the response starts dropping around 50 Hz...

[billfitzmaurice]

Re: Tops / Bass x-over settings for night club PA...

Finally, the subs are capable of going a bit low, but the sound more like "hit" boxes, if you know what I mean. Still, the RTA says the response starts dropping around 50 Hz...

As I expected. They probably are what we used to call 'bass bins' back in the day, before the advent of true subs.

[Mipsconsult]

Re: Tops / Bass x-over settings for night club PA...

Brian...

Try moving the Aphex Exciter to AFTER the compressor & drive rack. The 'magic' of the AAE could be giving the DSP in the drive rack fits. Or, simply remove the AAE from the chain.
Just a thought.

[Brian Steele]

Re: Tops / Bass x-over settings for night club PA...

Brian...

Try moving the Aphex Exciter to AFTER the compressor & drive rack. The 'magic' of the AAE could be giving the DSP in the drive rack fits. Or, simply remove the AAE from the chain.
Just a thought.

Thanks for the suggestion. Moving the AAE after the DRPA means that it can only be used to process the bass feed or one of the feeds for the tops, so that's probably not going to work out well. I may try removing it entirely.

I suspect the old mixer is the main issue. I'm going to try taking it completely out of the chain to see if some of the problems I highlighted in my previous post are addressed.

I suspect setting the gains properly with the Behringer amps is going to be an interesting exercise. It's not possible to lock their gain knobs, and they are very easy to turn, so I'll basically be setting them up (either via adjusting their x-over gain settings, or by adjusting the gain settings on the DRPA) so the amp reaches peak level with their gain knobs in the 12 o'clock position. The amps, DRPA, AAE and compressor are kept away from the DJ's hands, but they are still more accessible than I like at the moment, so doing it this way means I'll I need to do is to tell my brother to ensure the knobs are at 12 o'clock before the DJ goes on :-).

[billfitzmaurice]

Re: Tops / Bass x-over settings for night club PA...

Try moving the Aphex Exciter to AFTER the compressor & drive rack.

Better yet, move the exciter to the rubbish bin. They can make a junk system sound a bit better, but will only make a good system sound worse.

[Brian Steele]

Re: Tops / Bass x-over settings for night club PA...

Better yet, move the exciter to the rubbish bin. They can make a junk system sound a bit better, but will only make a good system sound worse.

What, no love for the AAE?

This club plays a mixture of different music at times. While modern music should sound fine without it, what about stuff from the 70's and 80's? Wouldn't that sound a bit "dry" without the extra processing? Note also that I think they sometimes pipe a live band through their system as well.

I spoke to my brother tonight. Yes, as I thought, the mixer is not used for anything else but passing on the feed from the DJ mixer downstairs. I suggested that he take it out of the input chain and run the feed directly to the compressor instead. Then that leaves only one gain knob (excluding the amps) to worry about, and it may take care of the hum problem as well. I'll float the idea to him of taking the AAE out of the chain as well.

[Brian Steele]

Re: Tops / Bass x-over settings for night club PA...

As I expected. They probably are what we used to call 'bass bins' back in the day, before the advent of true subs.

I've floated the idea to him of replacing the 'W' bins with something a bit more modern, using the same drivers. I've gone back and forth between a couple of design ideas, but I seem to be coming back to a sort of short-horn-laded BVR alignment, that gives me the extension of a TH in a 100L less of enclosure, and about a dB or so less output in the passband. The only acoustic purpose of the horn is to fill in the dip in the upper bass response caused by the big vents, but it also does allow me to mount the driver facing inwards, which should help keep the motor a little cooler (the club is A/C'd).

I also suggested that he double up on the number of subwoofers, because two 18" drivers trying to keep up with the eight 15" drivers in the tops is not going to work out well.

My design should be should be a fairly easy build. See images below. Imagine the big vent to the left split in two and brought around the sides of the enclosure to be flush with the output of the short horn to the right. That should give you an idea of what it will look like when built.

[Paul O]

Re: Tops / Bass x-over settings for night club PA...

WOW... what a mess. This is likely a good example of where less is more. Do they really need 6 tops on the dance floor? Mixing 2 different brands here is likely making things harder than they need to be and possibly causing overlaps in coverage with further messes things up, much depends upon the layout of course. And same goes for the electronics, there's really no need for the sonic crapitizer or compressor with the DRPA in the loop and the DJ's should have ZERO access to everything but the DJ mixer so I'd suggest you put a locking cover on the rack if the gear is located near the DJ booth. As for those 18" drivers some Cubo subs may be just the ticket, this design produces the output of a double 18 reflex in a box a little more than half the size without giving up lowend extension into the 35hz territory.