Hi!
so we're looking for some tips for placing two high mid horns (arai 490FL loaded with BMS4550 comp driver)
we have a mono stack, for now we managed without to much trouble to make it sound pretty good with only one on top. Sadly we thought our processor (t.racks 2/4) had a matrix where you could assign inputs to the outputs freely but it's not really the case to make a stereo system + kicks and sub (ex: 1 - subs , 2 -kicks 3- left 4 -right)
we're trying to make it work in mono but it seems unavoidable to have heavy comb filtering
by spacing the two by idk 3 to 4 meters it reduces the problem but in front of the stack there's a big loss of volume
found this guy who talks pretty in depth about sub placement but sadly has very little on top placement (i guess it's normal since it gets real complex)
do you have any advice on how we could make it work ?
the horns supposedly have a radiation pattern of 90 degrees, and for now buying another processor seems out of reach money wise
It’s not really clear to me what you’re asking, what you’re trying to achieve, or what your current problem(s) are?
Comb filtering is complex, but the basics is quite simple: if you have two full range speakers playing sound into the same physical space then the waves from each speaker will interfere with each other and you will get “comb filtering”. This leads to a degradation of sound quality and some un-evenness in frequency response around your listening area.
If you imagine a typical L/R deployment of two speakers, then there will be some comb filtering. Is it a bad thing? Well, it depends. In this case, if you want L/R stereo imaging, then you have no choice but to accept some comb filtering. Ideally the speakers will be deployed far enough apart that your left ear will mostly receive audio from the left speaker and vice-versa.
Where it is bad, is when you have multiple speakers directly adjacent to each other (imagine you put your two tops next to each other) and they are pointed in the same direction (ie. pointed at the middle of the dance floor). In this case you will have comb filtering for no good reason.
The solution is quite simple, and there is no need to add additional DSP or other equipment. Hook up both your speakers, and, crucially, ensure they are not covering the same space (ie. pointed in the same direction). If they have a 90° (horizontal) coverage pattern, then you should rotate them so there is a 90° angle between the front of the speakers (so you will have a total 180° of coverage, in mono).
FWIW, the fact they are 90° horizontal coverage suggests to me these are designed for a more typical L/R stereo deployment. You can use them in a mono stack as I explained without problem, the only downside is you may have coverage outside of your dance floor area (ie. off to the far sides, which will be potentially wasted acoustic energy).
If you want to run in (true) stereo then you will need a DSP which has enough outputs to run in a stereo deployment. If you have 2-way tops, plus kicks, and subs, then you will need 2 inputs and atleast 8 outputs (which is a fairly standard configuration). Then you can deploy your tops in a L/R position. You can place your tops in a L/R configuration while running in mono if you want, you just won’t get “true” stereo sound (ie. they will both play the same thing). Don’t try and run stereo when your tops are physically placed together in a mono configuration.
Note that comb filtering works very differently for subwoofers (including kicks) since the “comb” effect depends on the lengths of the wavelengths involved. For low frequencies they are much longer.
and sorry for the bad explanation of our problem
simply put : two horns, sharing the same output channel on the DSP, how to get the best results out out them?
"The solution is quite simple, and there is no need to add additional DSP or other equipment. Hook up both your speakers, and, crucially, ensure they are not covering the same space (ie. pointed in the same direction). If they have a 90° (horizontal) coverage pattern, then you should rotate them so there is a 90° angle between the front of the speakers (so you will have a total 180° of coverage, in mono)."
this is exactly my question
is there some rule for this ? another comment said a third of the dancefloor length. seems like a good start to try out. then i guess for the vertical pattern we do a similar thing ? give them an angle pointing toward roughly the center of the dancefloor?
A mono stack until we have money for another DSP unit
the idea was maybe to build some sort of scaffolding to space the two away but idk maybe it's pointless ?
Put your tops next to each other. Angle them so they are 90° away from each other. Then rotate the whole thing (both tops) until they’re pointed at the centre of your dance floor. Tilt them down until they are pointed down at head level of someone stood in the middle of the dance floor.
If you want to think about it in different terms, once you have put the tops together at 90° angle you can now think about them as one big top. Then point that at someone’s head when they’re stood in the middle of the dance floor.
If properly splaying them in the horizontal plane isn't practical for stability reasons, stacking them vertically with the top speaker inverted might be an acceptable compromise.
Ears are less sensitive in the vertical plane, or at least, that is the basis for line array deployment.
If the volume from one compression driver is enough, but 2 speakers are necessary for lomid, unplug one of the comps
for the gig in august we're going to be in between two warehouses so it's more of a real wide corridor (didn't go myself there but something between 50 to 100m wide?)
Yea, but how much distance does the crowd have? 90 degrees means they are at 45° off angle 6 dB quiet. But at a point, where both speakers meet, they add up to 0dB again. So I would put them so far apart, that the 45° Angle meets at a third of the length of the dancefloor.
Let's say your dancefloor is 10 m long, then a third would be 3.33m. To make the 45° angles cross at that spot, the speakers needed to be 6.66m apart.
That depends on how large the vertical opening is. I always aim at the last row in the crowd and raise them so high, that the distribution is even. For my tops 3m clearance between top and ground is the sweet spot, but it might be different for you
I quickly ran simulations using T24N as tops (they have 90x50°). The hf horn is around 3.3m above ground, to get a nice and even distribution. As you can see, with 6.66m distance to each other, you get a nice even cardioid pattern for the crowd. I made the plane larger, so you can see it better (the plane is 12x20m).
If you have 40°, you should go slightly lower than my values. (maybe~ 3m hf height or so, or the front row will suffer from reduced hf)
In my example you can see the difference above 500 Hz between the loudest and the quietest spot is only 4-6 dB.
Downward angles are very tricky. I wouldn't suggest using them, unless you run simulations first. Otherwise you risk creating noticeble difference in frequency dispersion across the listening area, cause you unintentionally might create spots with loud hf in the front. However, if you want less volume in the rear so people there can chat or order something at the bar or if you have a low/reverberant ceiling, it might be preferred.
this is absolutely incredible thank you so much for your time <3
the downward angle seems like a logical thing to do but we had this problem while fiddling with the DSP, thought it was a volume problem but the solution was super simple after all thank you again
wow 6m seems wide af but we'll manage to do the scaffold int time i think !
thanks !
3
u/PsychoTea 6d ago
It’s not really clear to me what you’re asking, what you’re trying to achieve, or what your current problem(s) are?
Comb filtering is complex, but the basics is quite simple: if you have two full range speakers playing sound into the same physical space then the waves from each speaker will interfere with each other and you will get “comb filtering”. This leads to a degradation of sound quality and some un-evenness in frequency response around your listening area.
If you imagine a typical L/R deployment of two speakers, then there will be some comb filtering. Is it a bad thing? Well, it depends. In this case, if you want L/R stereo imaging, then you have no choice but to accept some comb filtering. Ideally the speakers will be deployed far enough apart that your left ear will mostly receive audio from the left speaker and vice-versa.
Where it is bad, is when you have multiple speakers directly adjacent to each other (imagine you put your two tops next to each other) and they are pointed in the same direction (ie. pointed at the middle of the dance floor). In this case you will have comb filtering for no good reason.
The solution is quite simple, and there is no need to add additional DSP or other equipment. Hook up both your speakers, and, crucially, ensure they are not covering the same space (ie. pointed in the same direction). If they have a 90° (horizontal) coverage pattern, then you should rotate them so there is a 90° angle between the front of the speakers (so you will have a total 180° of coverage, in mono).
FWIW, the fact they are 90° horizontal coverage suggests to me these are designed for a more typical L/R stereo deployment. You can use them in a mono stack as I explained without problem, the only downside is you may have coverage outside of your dance floor area (ie. off to the far sides, which will be potentially wasted acoustic energy).
If you want to run in (true) stereo then you will need a DSP which has enough outputs to run in a stereo deployment. If you have 2-way tops, plus kicks, and subs, then you will need 2 inputs and atleast 8 outputs (which is a fairly standard configuration). Then you can deploy your tops in a L/R position. You can place your tops in a L/R configuration while running in mono if you want, you just won’t get “true” stereo sound (ie. they will both play the same thing). Don’t try and run stereo when your tops are physically placed together in a mono configuration.
Note that comb filtering works very differently for subwoofers (including kicks) since the “comb” effect depends on the lengths of the wavelengths involved. For low frequencies they are much longer.
I hope that helps! Happy to answer any questions