BillFitzmaurice.info

Hello!!

It's been a long time since I've been here. This is our current setup. Temporary.

We had the 4 T60s and 4 Jack10s installed in a small 60 persons club for almost 5 years. The owner sold the space in March of 2019.
This setup is in my friends loft. Very cool spot. Very strange setup as it is in an old industrial building. Realistically the space is probably 80'x160', but it is all cut up into smaller sections with lots of partial height walls and few full height walls.

I've never been very good at tuning my system (which is testament to how good the Tuba 60s are because the dance music community here really thinks I know what I'm doing, I try to be humble and admit I do not). As we know the Jack 10s didn't really compare to the T60s, thats a long story and I take responsibility for making poor decisions and being in over my head during the build all those years ago.

I recently found these old Acoustic PA tops for peanuts.. threw some B&C 15"s and Selenium horn drivers in them and I'm very happy with how they sound for this temporary fling (a series of 4 bi-weekly events, 3 left to go!)

Anyway, we have limited hours (Sundays only) to really let it rip, eq, tune, adjust so I'm posting here to potentially expedite things.

The first event looked slightly different to the photo, and I'm fairly sure these adjustments made dramatic improvements but I can't measure until Sunday.
We first noticed that having the subs on the ground just didn't have the power we were used to in the smaller space so I remembered an old post here about a guy standing them up. I stood in the sweet-spot while my buddy started to lift the first one up. I had a 60Hz sine wave playing and it was so dramatic that we all took turns experiencing it. lifting the sub up to face the ceiling was like grabbing the fader on the console and pushing it up 9dB. So we put all four subs in a line against the wall. Well, after thinking about it and experiencing the first gig I was realizing that the 2 outside subs were pretty far away from each other. We now have them in this cube shape, yet still facing the ceiling. I'll know more later, but subjectively things seem much cleaner and I was able to drop the sub output on the DSP 4dB to keep a matched "perceived" balance.

I also moved the tops out of the corners a couple feet. Just based on a simple google search of distance from wall.. any further tips/science here would be appreciated! I'm not set on my acoustical crossover yet.. but electrically it is currently at 98Hz.

Looking at the photo, any tips or criticism is helpful.

Beyond that... I really need a good primer on how to electronically set this up from scratch. When I installed in the club I was fresh out of Audio Engineering school and I kind of chugged away thinking I knew some stuff and I didn't have an RTA setup.. blah blah.. people loved it. I didn't.

I am now finally getting comfortable using REW for basic frequency sweeps and I have a nice Audix RTA mic.

I use 4 QSC PLX 2s. I use an Ashly Protea 3.6, 2 in from the dj mixer, and 6 out: 1 to each sub amp (mono in dsp settings), 2 to the mid amp, 2 to the hi amp.

I'd like some guidance or links to articles/videos/books on the best practice for measuring raw response and letting that guide where I set crossover points.

I'd like to know how you decide on which slope to use. Subjectively the Linkwitz 48dB seem to sound better on the T60s for Techno/Dubstep, but again I am not confident in this.

I'd like to know which order things should be done it. I think it would be this: sweep each speaker one at a time, overlay those responses, notice natural xover points, set them, sweep each box and eq box corrections, and then sweep whole rig, then balance input/output gain for each band to be (flat?) (xcurve?) (help?), and then sweep again for room correction.

Am I way off? Please be gentle, but tell me!

I feel like I need to go to school all over again. I'm also aware that my intention is good and I just want to be a better "engineer". Admit my faults etc.. TIA

G'day, welcome back!
Righto, first things first.
You need some space. Say 20 metres OUTSIDE in every direction from the mains cab before you hit any type of obstruction.
Record your response so you can analyse it later. Presumably the mains cabs have passive internal crossovers so that's taken care of.
Having a chart can also assist with determining a baseline EQ.

Sounds like you want to bi-amp, so you need to include/link SPL charts from the manufacturers of the drivers you have installed and their specs to be able to assist there.

Once you know what your mains response is like, you can set a crossover point based on information and not guesses, because you already have that information for your subs.

That gets you an electrical crossover point.

However, if you do again what you've already done, ie alter subs response by the 4dB you did to achieve balance, you've already altered the acoustic crossover point!

In order to work out how much you've altered acoustic crossover point, you have to plot subs and mains on one chart, including the selected subs low pass slope and value (eg LR24), and the mains high pass slope and value (eg LR24), then move each line according to what you've done is DSP to determine the final value...

Thank you very much for the response Grant!

The x-overs in the mains were damaged which lead us to just bi-amping.

JBL response: JBL recommended x-over: B&C response: I do not have the opportunity to take the mains outside for testing before the next gig. well.. at least not with the 20-meter space. Definitely don't have a crane!

I think after this event series I can get them out to my grandparent's property to do that type of measuring. So understanding this is an improper procedure, do you have any recommendation for the best practice?
Do you typically have an "independent box" eq set in the DSP 1:1 each box and then just use one stereo eq for the mains to tune the room? As I type that, it seems obvious. But.. I'm trying to be ultra sure of the standard practices. Assuming that's the case, then you can set eq just by looking at Bills eq response data yeah? I've always wanted to measure each tuba, label them, and have hyper-specific calibration presets. But time, space and knowledge are still scarce.

When eqing the "room" for the sub-cluster/bandwidth is there an article I can dissect on best practice for mic placement, number of places, etc..?

You don't need a lot of space to measure mains. Since the longest wavelength they pass is only 12 feet or so being at least that far from buildings is adequate, especially if your gear can do a gated measurement. Do a ground plane measurement to get the result up to 250-300 Hz, put the cab on its back and take a measurement with the mic suspended above the cab to get the result above 250-300Hz, splice the results.

When you get the chance, go and do what Bill has suggested above.

It's not best practice. Best practice is to think and do well before the gig.
In the meantime, to get the "gig" done;

For the mains, try a 2K high pass on the JB's with a BW12 or 24 slope, and a low pass of say 18K, LR24.
That's 2 outputs on your DSP, HF left and right.
I don't like running subs above 100Hz, you may feel differently, but those B&C's dive from 100Hz down,
so high pass them at 100Hz, LR or BW 24 or 48, low pass at 2K with a BW12 or 24.. That's 2 outputs on your DSP, mid L and R.

If I have said 12 or 24, or 24 or 48, LR or BW above, try them, see if one sounds better than another to you.

Subs, high pass at 25Hz LR48, low pass 100Hz, LR or BW 24. One channel on your DSP (run them in mono). Set your limiters.
Do you remember how?

Setup, DJ mixer, to EQ to DSP to amps.

EQ, just looking at the response charts, set to -3dB at 125Hz, -3dB at 4K and 8K, and that gets you started...

Oh, to have an island of t60s!! I went back a looked at your post again, but don't see what kind of gigs these 4 "events" are. What are you actually doing with the system? Good luck, and keep the posts on your progress coming.

himhimself wrote: ↑Sat Feb 22, 2020 7:22 pm Oh, to have an island of t60s!! I went back a looked at your post again, but don't see what kind of gigs these 4 "events" are. What are you actually doing with the system? Good luck, and keep the posts on your progress coming.

They are dance parties. I suppose. Our community is pretty diverse in the electronic realm at least. House, techno, dnb, ambient, experimental, dubstep, hardcore, electro and including all the sub genres of each... lofi, classic, minimal, EDM-esque... trap, hiphop. But all djmixer out... attendance ranges from 12-200 people depending on time of day.

Grant Bunter wrote: ↑Sat Feb 22, 2020 3:37 pm When you get the chance, go and do what Bill has suggested above.

It's not best practice. Best practice is to think and do well before the gig.
In the meantime, to get the "gig" done;

For the mains, try a 2K high pass on the JB's with a BW12 or 24 slope, and a low pass of say 18K, LR24.
That's 2 outputs on your DSP, HF left and right.
I don't like running subs above 100Hz, you may feel differently, but those B&C's dive from 100Hz down,
so high pass them at 100Hz, LR or BW 24 or 48, low pass at 2K with a BW12 or 24.. That's 2 outputs on your DSP, mid L and R.

If I have said 12 or 24, or 24 or 48, LR or BW above, try them, see if one sounds better than another to you.

Subs, high pass at 25Hz LR48, low pass 100Hz, LR or BW 24. One channel on your DSP (run them in mono). Set your limiters.
Do you remember how?

Setup, DJ mixer, to EQ to DSP to amps.

EQ, just looking at the response charts, set to -3dB at 125Hz, -3dB at 4K and 8K, and that gets you started...

That is very helpful. Do you have a reference for calculating Q value based on a chart? And did you mean that you wouldnt eq the T60s at all?

I've been looking at threads on setting limiters. Kind of crazy weve survived this long without doing it. Lol. But no. Sadly I've never done it and some of the threads seem to debate on proper procedure.

Bill Fitzmaurice wrote: ↑Sat Feb 22, 2020 11:29 am You don't need a lot of space to measure mains. Since the longest wavelength they pass is only 12 feet or so being at least that far from buildings is adequate, especially if your gear can do a gated measurement. Do a ground plane measurement to get the result up to 250-300 Hz, put the cab on its back and take a measurement with the mic suspended above the cab to get the result above 250-300Hz, splice the results.

Interesting. So if I'm inside with every wall/ceiling further than 12 feet I can do this too? That might be possible tomorrow even.

No, because outdoors you'll get one reflection, indoors you get multiple reflections as the waves bounce about the room, including off the ceiling.

Bill Fitzmaurice wrote: ↑Sun Feb 23, 2020 2:39 pm No, because outdoors you'll get one reflection, indoors you get multiple reflections as the waves bounce about the room, including off the ceiling.

Ok. Makes sense.

Grant Bunter wrote: ↑Sun Feb 23, 2020 3:57 pm

5meohd wrote: ↑Sun Feb 23, 2020 1:40 pm Do you have a reference for calculating Q value based on a chart?

No. I use a 31 band GEQ. They tend to not have Q control.

And did you mean that you wouldnt eq the T60s at all?

You said you were happy with the T60's as they were. Best to leave that alone.

I've been looking at threads on setting limiters. Kind of crazy weve survived this long without doing it. Lol. But no. Sadly I've never done it and some of the threads seem to debate on proper procedure.

You may well have been lucky. Still it's not to late to protect your investment.
Find a method, that seems to sit with you, and implement it..

Most graphic equalizers generally work at 1/3oct slopes I think, so a Q value of 3 I guess. My Ashly Protea unit doesn't have built-in graphic eq. I could get my BSS hooked up but I'm not sure adding another device in the chain is worth it.

5meohd wrote: ↑Sun Feb 23, 2020 8:29 pm Most graphic equalizers generally work at 1/3oct slopes I think, so a Q value of 3 I guess. My Ashly Protea unit doesn't have built-in graphic eq. I could get my BSS hooked up but I'm not sure adding another device in the chain is worth it.

If your DSP has PEQ, use that.
If you have Q control, you want enough to cover 100Hz to 150Hz with Q and -3dB at 125Hz as I said before.
The -3dB at 4K could have similar Q
The -3dB at 8K can allow a little wider Q, you're trying to dip about 6 to 10K with the max -3dB at 8K.
All that will get you roughly flat, then tweak to ears in the space.
If no PEQ, adding your BSS absolutely is not only worth it, but mandatory.
Never run what amounts to pro sound without EQ...

Ok. Thanks, Grant. I know I'm asking very noob, and vulnerable questions. I'm trying to show humility and get the most help I can.

However, several comments like eq being mandatory... Of course. Yes. I've been running the T60s for 6 years now. Never blown a driver, always blown people's minds. I'm just trying to take things to the next level. Such as ironing out a specific method for Limiting. And knowing not just how to set them, but when, if ever they would need to be adjusted.
Like looking at the manufacturer frequency plots... I understand how valuable they are, but then in the physical space when I sweep at 1 meter, etc... It looks nothing like the graph from the manufacturer. So I simply question where to start. The stuff sounds god awful without EQ. So we sculpt to the best of our ability (I have very little confidence in my ears when testing I can pick "low, mid, high" but not 900Hz vs 2kHz. So I'm never satisfied. Ever. I'm just trying to move forward, however long this takes.

Also, I was remembering the QSC amps have built-in limiters and I engaged them years ago. I know that isn't the best practice. I'll fix that.

I'm also humbly aware that its challenging to communicate via forums and I'm not yelling at you like "I already know that Grant". I'm just trying to paint a better picture. My little ego doesn't want to feel like a total F****** moron.

Thanks for all the help so far! Today is the day I get to go play with it all day long. I'll try to take a lot of screenshots and document any progress.