ProSoundWeb Community

Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Subwoofer Forum => Topic started by: Eugen Jeličić on August 06, 2017, 06:43:36 AM

Title: Arraying horn loaded subs,options?
Post by: Eugen Jeličić on August 06, 2017, 06:43:36 AM
So last week i have been mixing a 2 day open air show. 10 bands, some guesting engineers, i did the rest.

Last year i ordered a KV2 vhd2.0 rig for the same show but this year i went for a local hand made soundsystem witch didn't sound as balanced as kv2, but had a lot more power and a much better coverage angle. Overall i was quiet happy but had some weird situations with sub coverage.

So the system consisted of 8 top boxes with some BMS tweeters and 4x10 inch drivers.
Really high sensitivity but a bit thin below 1khz.

The subs are what's known as an Invader Horn. You can find a drawing online. Here is a picture of what it looked like from FOH. We have been limited with how we can array the rig because we didn't have a ramp or anything similar:

https://scontent-frt3-1.xx.fbcdn.net/v/t31.0-8/20545250_10210290380436627_7059157134728030314_o.jpg?oh=0591723f7d01d244415975d9d635ab59&oe=59F08A94

So since it's a standard L/R sub array, there was a summation zone at FOH in the center of the field. And there were holes in the field. Standard...
But there was some weird stuff.
First, in the power alley, exactly on the line in front of the subs, there was not that much power. It seemed that even of you muted one side of the subs to remove cancelation problems between sides, there was more power at FOH then there was right on the line in front of the subs.
And when both sides have been running and you moved away to the side of the PA, there was very very little sub power at all. With clasical reflex boxes it always seemed to me that there is a power alley right on the axis of the subs and you usually find summation in the center where FOH should be. With some power lefover on the sides. This was totaly different. Like subs radiated more power at an angle of the array. Then they did right in front of them.


The other thing that i noticed was that all the power i had didn't sound natural and flat but kind of "pumped up". like you are in a closed room and hear boosts from room resonances.
But we have been in a completly open field. No boundaries at all. A football field in the middle of nowhere.

And i remember that the same thing happens when you array horns like theese with their mouths facing the floor. A usuall monoblock setup. You get a big ball of pumped up resonant power in front of the subs and then it gets lost in the field.

This was kind of like the same thing but distributed differently.
So i was wondering, how horn loading affects the coverage pattern of the subs and what happens when you array them in different ways. We coupled the horn mouths because that way you get more mouth surface and they start going lower. But my FOH engineer friend told me that when you array them the other way around, they give you less power but more natural, better distributed sub coverage.

Subs are loaded with some Fane drivers and pushed with EV q1212 amps bridged. DSP was EV DC1. Crossover was at 70hz because if i ran them higher i would stard getting huge amounts of excess material between 80-120hz giving me a very boxy sounding subs. I didn't like that.

On the other hand i have to compliment theirs transient response. They are very fast and nicely defined.


Title: Re: Arraying horn loaded subs,options?
Post by: Don T. Williams on August 06, 2017, 04:26:57 PM
So last week i have been mixing a 2 day open air show. 10 bands, some guesting engineers, i did the rest.

 
But there was some weird stuff.
First, in the power alley, exactly on the line in front of the subs, there was not that much power. It seemed that even of you muted one side of the subs to remove cancelation problems between sides, there was more power at FOH then there was right on the line in front of the subs.
And when both sides have been running and you moved away to the side of the PA, there was very very little sub power at all. With clasical reflex boxes it always seemed to me that there is a power alley right on the axis of the subs and you usually find summation in the center where FOH should be. With some power lefover on the sides. This was totaly different. Like subs radiated more power at an angle of the array. Then they did right in front of them.


The other thing that i noticed was that all the power i had didn't sound natural and flat but kind of "pumped up". like you are in a closed room and hear boosts from room resonances.

I would be suspicious of polarity reversals some place in the system.  It could be input cables wired out of phase, speaker cables inverted, speaker drivers with inverted wiring, basically anything that could cause one side or some speakers to be 180 degrees out of phase with the other.  The main clue to me is that when one side is shut off, it gets louder in the center.  Classic symptom of inverted phase!
Title: Re: Arraying horn loaded subs,options?
Post by: Eugen Jeličić on August 06, 2017, 05:15:08 PM
I would be suspicious of polarity reversals some place in the system.  It could be input cables wired out of phase, speaker cables inverted, speaker drivers with inverted wiring, basically anything that could cause one side or some speakers to be 180 degrees out of phase with the other.  The main clue to me is that when one side is shut off, it gets louder in the center.  Classic symptom of inverted phase!

Nope. Checked it in depth. All four subs on each side where in phase with each other, both sides where in phase too.
But i think you misunderstood me. I didn't say there was more power in the center when you turned of one side. No, there was a 3dB loss. The summation in the center was fine.

What i wanted to say is that if you eliminated one side completly. And stood 10 meters away from the 4 running subs on the other side. Right on axis of the subs there was less power then when you went about 30-40 degrees of axis.
So if a monoblock of 4 subs is working, the power alley in front of them looks like a triangle. There was more power at the sides of the triangle then right in the center. I don't know how this is possible.
Title: Re: Arraying horn loaded subs,options?
Post by: Don T. Williams on August 06, 2017, 07:11:27 PM
Nope. Checked it in depth. All four subs on each side where in phase with each other, both sides where in phase too.
But i think you misunderstood me. I didn't say there was more power in the center when you turned of one side. No, there was a 3dB loss. The summation in the center was fine.

What i wanted to say is that if you eliminated one side completly. And stood 10 meters away from the 4 running subs on the other side. Right on axis of the subs there was less power then when you went about 30-40 degrees of axis.
So if a monoblock of 4 subs is working, the power alley in front of them looks like a triangle. There was more power at the sides of the triangle then right in the center. I don't know how this is possible.

I stand corrected on the phase inversion.  How it's possible to have more power on the sides than in the center is a complex phase relationship problem.  Is there anyway to set up the subs as a mono center cluster?
Title: Re: Arraying horn loaded subs,options?
Post by: Chris Grimshaw on August 07, 2017, 03:38:40 AM
Could still be almost anything.
For instance, if one side had a few ms delay, that'd give you all sorts of interesting problems.

Were all the cabinets the same? Did they all have the same drivers? I've often seen operators with lots of bass horns like those with a few different make/models of drivers in use. Some of them are okay for that cabinet, others not so much. There'll be some very interesting relationships between the different cabinets.

Was all the processing zero'd, or sensibly applied?


Couldn't open your Photobucket link, since they've decided to lose all of their users pretty much overnight.

Is there any chance you could sketch a map of where you found the loud/dead spots were?

You've got to bear in mind that large sub arrays will start to exhibit some directionality of their own. In the case of horns like these, it's related to the total mouth area, which can get quite large.

Chris
Title: Re: Arraying horn loaded subs,options?
Post by: Eugen Jeličić on August 07, 2017, 04:59:17 AM
Could still be almost anything.
For instance, if one side had a few ms delay, that'd give you all sorts of interesting problems.

Were all the cabinets the same? Did they all have the same drivers? I've often seen operators with lots of bass horns like those with a few different make/models of drivers in use. Some of them are okay for that cabinet, others not so much. There'll be some very interesting relationships between the different cabinets.

Was all the processing zero'd, or sensibly applied?


Couldn't open your Photobucket link, since they've decided to lose all of their users pretty much overnight.

Is there any chance you could sketch a map of where you found the loud/dead spots were?

You've got to bear in mind that large sub arrays will start to exhibit some directionality of their own. In the case of horns like these, it's related to the total mouth area, which can get quite large.

Chris

Yes, i don't know wtf is photobucket doing. But i replaced the link in the main text with a direct facebook link.

Here is another picture of me tweaking the DC1 system processor. And the guy from the PA company on the right:

https://scontent-frx5-1.xx.fbcdn.net/v/t31.0-8/20616033_1610317225707178_7252533669470684012_o.jpg?oh=7141f7934e47f30075664a869f5cd83e&oe=59EDC9CB

but the other side of the PA can't be seen in the picture.

Now as you can see, the horn mouth got quiet large when we coupled 4 of them. Plus, considering the horn exit shape, it even made sense to me that they kind of kicked the power off to the sides a bit. 
But i posted this subject because i want to learn more about horn coupling rules because it seems to me that they exibit some rather interesting behaviour when stacked in different ways.
I was interested in what happens when you turn them the other way around,horns away from each other.

All the boxes are the same, they all have the same Fane drivers. All running from bridged EV Q1212 amps.
No delays on any of the boxes.

But the crossover settings were a bit weird. Considering these subs had excess amounts of 80-130hz material and sounded very boxy. The best way to clean that up was a lowpass at 68hz, 24dB/octave. When i did that they flattened up towards 100hz. The top boxes were highpassed at about 130hz. You'd think there was a bit of a hole there but it didn't sound like that.
Title: Re: Arraying horn loaded subs,options?
Post by: George Dougherty on August 08, 2017, 10:58:53 AM
With my own horn loaded boxes I would tend to orient them so the horns are closest to the ground.  Rotated 90 degrees from how they're shown once I go from 2 to 4 boxes per side.  Could potentially be some issues with cancellations off the ground from the upper subs.

How did you test polarity of the subs within a stack?
Title: Re: Arraying horn loaded subs,options?
Post by: Eugen Jeličić on August 08, 2017, 12:12:40 PM
With my own horn loaded boxes I would tend to orient them so the horns are closest to the ground.  Rotated 90 degrees from how they're shown once I go from 2 to 4 boxes per side.  Could potentially be some issues with cancellations off the ground from the upper subs.

How did you test polarity of the subs within a stack?

I stand in front of the subs, another guy unplugs 3 out od 4 subs while running pinknoise trough them. Then, he plugs the next one, then the next one, then the next one. Untill all four are working.
At each plugin, the power rised.
Title: Re: Arraying horn loaded subs,options?
Post by: Don T. Williams on August 08, 2017, 05:51:25 PM
w
I stand in front of the subs, another guy unplugs 3 out od 4 subs while running pinknoise trough them. Then, he plugs the next one, then the next one, then the next one. Untill all four are working.
At each plugin, the power rised.

Eugen, that really isn't a comprehensive test method.  From what you described, there is still no way to know if the two sides have the same phase relationship.  That is still my concern with the problem as you described it.  With a XLR M/F "phase reverser" or with your crossover or speaker DSP, can you do the same listening test for the two sides?
Title: Re: Arraying horn loaded subs,options?
Post by: Art Welter on August 08, 2017, 10:29:24 PM
1)Now as you can see, the horn mouth got quiet large when we coupled 4 of them. Plus, considering the horn exit shape, it even made sense to me that they kind of kicked the power off to the sides a bit. 
2)But i posted this subject because i want to learn more about horn coupling rules because it seems to me that they exibit some rather interesting behaviour when stacked in different ways.
I was interested in what happens when you turn them the other way around,horns away from each other.
3)Considering these subs had excess amounts of 80-130hz material and sounded very boxy. The best way to clean that up was a lowpass at 68hz, 24dB/octave. When i did that they flattened up towards 100hz. The top boxes were highpassed at about 130hz. You'd think there was a bit of a hole there but it didn't sound like that.
Eugen,

1) Other than the upper range of the pass band the subs operate in, the dispersion will be dictated by the mouth size, "power", as in SPL, will not be kicked left or right.
2) Horn subs can have a huge rising response, like 12 dB per octave, so your 68hz, 24dB/octave may only result in a 12 dB slope with another +6 dB peak here and there in the upper range.
That can still let a boatload of "junk" through in the range between the subs and tops. This "junk" will vary in phase between the two depending on your listening position and the directivity index of the cabinets- the tops will be omni at their bottom, the horn subs may have less than 90 degrees at the top of their bandwidth.
3) No "hole", just multiple phase problems- the subs need to be phase aligned to the tops through the crossover region, and when that region is wide due to the problems described in #2, all sorts of crap response happens, resulting in sound only being good along the axis which is equalized for flat response.

Bottom line- the array is not the problem, it is the interaction between the subs and tops that is messing with your "bass" perception, which may be most critical in the overlap in the octave you crossed at, 68-130 Hz.

Cheers,
Art
Title: Re: Arraying horn loaded subs,options?
Post by: Peter Morris on August 08, 2017, 11:43:17 PM
Eugen,

1) Other than the upper range of the pass band the subs operate in, the dispersion will be dictated by the mouth size, "power", as in SPL, will not be kicked left or right.
2) Horn subs can have a huge rising response, like 12 dB per octave, so your 68hz, 24dB/octave may only result in a 12 dB slope with another +6 dB peak here and there in the upper range.
That can still let a boatload of "junk" through in the range between the subs and tops. This "junk" will vary in phase between the two depending on your listening position and the directivity index of the cabinets- the tops will be omni at their bottom, the horn subs may have less than 90 degrees at the top of their bandwidth.
3) No "hole", just multiple phase problems- the subs need to be phase aligned to the tops through the crossover region, and when that region is wide due to the problems described in #2, all sorts of crap response happens, resulting in sound only being good along the axis which is equalized for flat response.

Bottom line- the array is not the problem, it is the interaction between the subs and tops that is messing with your "bass" perception, which may be most critical in the overlap in the octave you crossed at, 68-130 Hz.

Cheers,
Art

I suspect any or all of the above and possibly a polarity issue with one pair of subs.

Title: Re: Arraying horn loaded subs,options?
Post by: Eugen Jeličić on August 09, 2017, 06:23:55 AM
Eugen,

1) Other than the upper range of the pass band the subs operate in, the dispersion will be dictated by the mouth size, "power", as in SPL, will not be kicked left or right.
2) Horn subs can have a huge rising response, like 12 dB per octave, so your 68hz, 24dB/octave may only result in a 12 dB slope with another +6 dB peak here and there in the upper range.
That can still let a boatload of "junk" through in the range between the subs and tops. This "junk" will vary in phase between the two depending on your listening position and the directivity index of the cabinets- the tops will be omni at their bottom, the horn subs may have less than 90 degrees at the top of their bandwidth.
3) No "hole", just multiple phase problems- the subs need to be phase aligned to the tops through the crossover region, and when that region is wide due to the problems described in #2, all sorts of crap response happens, resulting in sound only being good along the axis which is equalized for flat response.

Bottom line- the array is not the problem, it is the interaction between the subs and tops that is messing with your "bass" perception, which may be most critical in the overlap in the octave you crossed at, 68-130 Hz.

Cheers,
Art


DON:

I misunderstood you. I tought you asked how did i check if all of the four subs on each side were in polarity with each other. Not how i checked if left subs were in polarity with the right subs.

To check if the left and the right side were in polarity, i stood in the center, at FOH. And tried flipping the polarity on one side of the subs. The power loss was huge. When i got them back to the same polarity. The summation at FOH (center) was fine again. Since they should summate at a triangular center in front of the left and right subs. I concluded that L and R subs are in polarity.


ART:

I think we are getting somewhere. Both i and the guy from the PA company suspected that my low crossover setting was part of the weird situation. Because he told me that usually they don't work that way when they crossover the subs at 100hz, or even 110.

Now let's go back a few steps. You wrote that horn loaded subs have a rising response when going from sub, to lowmid frequencies. This is exactly what i noticed when i removed the crossover and did a sinewave sweep from 50 to 150hz with the subs running only. Their power rises vastly the higher you go. I noticed similar things with my own EV T18 horn loaded boxes. This is what gives them a "punchy, boxy" sound. From my perception this can be potentialy usefull for trance and techno music (exactly what is usually the main use of this PA that i worked with). But for mechanical music, it makes your kickdrum boxy as hell. "thump" instead of "boom".

The other thing that made me think this problem is even more prominent with these subs is the fact that the "invader bin" is a design with a sealed chamber. So the driver is sealed from one side, and pushing air into the horn on the other side. The sealed chamber chokes the subs even more down at lower frequencies then it does in the lowmids. Because the driver needs to travel more at lower frequencies so the compressed air in the sealed chamber chokes it's movement more.

The result of this is that i had to go for a 68, and even 65hz 24dB/octave crossover. Which just as you wrote, sloped them down from 65 do 100hz just enough to flatten the response up to 100hz. The sinewave sweep confirmed this.
As soon as i would try opening the crossover up to 75-80hz, i would find myself eq-ing that out of the kickdrum and the bassguitar on the channel EQ.


Now, one thing, that we did not do, and that may be the cause for some of the problems. Is that we didn't delay the tops to the subs. I even brought a measurement MIC and SMAART on my laptop, and was planing to do phase alignment. But we ran out of testing time, and on top of that i saw the situation from a potentialy wrong perspective.

I tought, that considering the top boxes are crossed over at 140hz, 24dB/octave BW. And the subs are crossed over at 65hz, 24dB/octave BW. The top boxes won't reach much into the lowmid 100hz spectrum where the subs start going quiet, so there is no need to phase align them. I tought that i am going to have a hole in the overlapping region that is going to be so wide that it won't make much sense doing any phase alignment.

This was kind of my mistake of listening with my "pre-opinion" instead of with my ears.

However, even tought we suspected the same thing that you wrote, one thing is still not clear to me. These weird sub distribution problems, were very present down at 50hz. That means there was something weird going on with phase problems even down there where the tops don't play any significant amount of material.

Could it be, that the low crossover setting, made a phase anomaly at very low frequencies, that made the Left and right side of subs summate in weird ways? Even tought that the same crossover affected left and right subs and that left and right subs were in polarity with each other?
Title: Re: Arraying horn loaded subs,options?
Post by: Ivan Beaver on August 09, 2017, 07:47:30 AM



I tought, that considering the top boxes are crossed over at 140hz, 24dB/octave BW. And the subs are crossed over at 65hz, 24dB/octave BW. The top boxes won't reach much into the lowmid 100hz spectrum where the subs start going quiet, so there is no need to phase align them. I tought that i am going to have a hole in the overlapping region that is going to be so wide that it won't make much sense doing any phase alignment.


There is often a BIG difference between the electrical xover and the ACOUSTICAL xover.

The acoustical xover is really all you need to be concerned with (as long the the electrical xover is not stressing the drivers).

A proper phase alignment can make the difference between a hole and a flat response-even if the electrical xover freq are not changed.

It can be a huge hole-and a little bit of alignment will fix it.  At least in one listening position.

How well does this alignment hold up over the audience?  It depends on the actual freq (size of the wavelength) and the distance between the devices being aligned.

You generally want the distance to the listener to be 1/4 wavelength (of the acoustical xover) or less.

A couple of ms can make a huge difference in the overall sound/response/punch etc.
Title: Re: Arraying horn loaded subs,options?
Post by: Don T. Williams on August 09, 2017, 10:26:59 AM
Eugen, I agree with you and think the left and right side subs don't have the polarity inverted.  You have an interesting and complex problem.
Title: Re: Arraying horn loaded subs,options?
Post by: Art Welter on August 09, 2017, 11:28:41 AM
ART:
1)The other thing that made me think this problem is even more prominent with these subs is the fact that the "invader bin" is a design with a sealed chamber. So the driver is sealed from one side, and pushing air into the horn on the other side. The sealed chamber chokes the subs even more down at lower frequencies then it does in the lowmids. Because the driver needs to travel more at lower frequencies so the compressed air in the sealed chamber chokes it's movement more.

2)Could it be, that the low crossover setting, made a phase anomaly at very low frequencies, that made the Left and right side of subs summate in weird ways? Even tought that the same crossover affected left and right subs and that left and right subs were in polarity with each other?
Eugen,

1) A front loaded horn (FLH) driver's excursion actually reduces to a minimum at low frequencies down around Fc (cutoff frequency) below which the horn "unloads", and frequency response and excursion is basically the same as the small sealed chamber would produce on a flat baffle the size of the horn mouth. Obviously, with high power, a steep HP filter at Fc must be used unless you like the sound of flapping cones ;^).
As you can see in the FLH simulation examples below, excursion is greatest a bit under an octave above Fc, about the upper cutoff frequency you chose on the gig in question. IIRC, the "Invader" has a higher Fc than the examples shown, so the upper excursion peak would also be higher.

2) The LF "weird summation" could be the result as Peter showed of a polarity reverse on one or a pair of subs, or likely the building and truck on one side of the PA. If the sub boundary conditions are not the same either side, the pattern won't be either.

Art
Title: Re: Arraying horn loaded subs,options?
Post by: Eugen Jeličić on August 09, 2017, 03:52:41 PM
Ivan.

Yes i realize that. But i didn't think some boxes have such prominent natural boosts that i would need to start cutting almost an entire octave lower (65hz), to flatten the response up to the higher octave limit (130hz). So this situation was a bit weird to me.

ART:

How is that possible? When the horn loaded sub starts going very low, the wavelenght starts exceeding the horn lenght by a lot so the horn stops being effective in loading the driver. Because most of the air just moves away at the horn exit. The horn isn't long enough to hold the air in one place under pressure.
That would mean that the driver starts moving under lesser air impedance (smaller load), which would mean it moves more free and moves further?

That's why the lowcut filter is applied right? To stop the driver from exceeding xmax and doing damage to itself.
Just like with reflex boxes. Once you pass the port resonance, the box stops loading the driver well. Therefore the driver starts moving too much and flapping, potentialy damaging itself. So you apply a LC filter?

Or my logics failed me? Can you explain what you wrote up there a bit better?
You claim that driver moves the most almost an octave above the LC.
We set the LC for the invaders at 35hz.
Title: Re: Arraying horn loaded subs,options?
Post by: Roland Clarke on August 09, 2017, 04:28:00 PM
I think that there maybe some misunderstanding due to English usage.  From my reading of the original post he was describing power alley as the line directly in front of one sub stack, not directly between the speakers as we would describe it.  That would make all the other issues just usual stuff to be expected from some pretty low standard bass horns.

Title: Re: Arraying horn loaded subs,options?
Post by: Ivan Beaver on August 09, 2017, 05:10:49 PM
Ivan.

Yes i realize that. But i didn't think some boxes have such prominent natural boosts that i would need to start cutting almost an entire octave lower (65hz), to flatten the response up to the higher octave limit (130hz). So this situation was a bit weird to me.


If you look at the measured response of many cabinets, and compare the output at 40Hz vs 100Hz, you will see that the 100Hz is quite a bit louder, so it has to be reduced even more to be equal to 40Hz.

Not all are this way-but most are.  they get much louder up higher in the "bass" range.  In fact, it is above 100Hz that a lot of cabinets get their claimed sensitivity-NOT down around 50Hz-where it should be stated.

Some cabinets have had sensitivities for sub cabinets measured above 1KHz.

That is not exactly "sub range" to me.

YES-it is important to look at the freq response-the unprocessed response-to get an idea of what is going on.
Title: Re: Arraying horn loaded subs,options?
Post by: Eugen Jeličić on August 09, 2017, 05:35:00 PM
Roland:

Exactly, that's what i wrote. The lack of power was not in the FOH (center) summation location.
It was in the line in front each of the sub stacks. English is not my primary language but i think i wrote that correct.
Can you explain what do you mean by "standard" issues caused by low standard horns? I'm curios what's happening here.

Ivan:

Is this also the case with reflex boxes or just with horns? It seems to me that horn loaded subs tend to get these 100 plus hertz power rises, non existant 200-500hz harmonics causing honk,boxy sound and similar things.
It seems to me that boxes like G-SUB and similar things don't suffer from these problems. Yes they have some other problems but it seems to me they tend to stay quiet clean above 100hz.

And yes of course. You look at the sensitivity and power ratings and think "wow this is going to be a powerfull box" and then relise it's just a bunch of 100-150hz junk that you don't need. And you are lacking 40-50hz power.
Title: Re: Arraying horn loaded subs,options?
Post by: Ivan Beaver on August 09, 2017, 06:51:51 PM

Ivan:

Is this also the case with reflex boxes or just with horns?
It is best to look at the measurements of the particular boxes you are looking at.  They vary.

But yes, many reflex boxes are the same way, with a sloping response, or the output above 100Hz is much louder than the response down at 40-50Hz

Not all horns are created the same, and all reflex boxes are not the same

It is best to NOT to generalize, but to look at SPECIFIC boxes to get actual answers.

Are all gasoline engines the same?  What about diesel?  The answer is no.
Title: Re: Arraying horn loaded subs,options?
Post by: Steve Litcher on August 10, 2017, 11:24:58 AM

It is best to NOT to generalize, but to look at SPECIFIC boxes to get actual answers.



I'm interested in this, as I've experienced instances where "pairs" of tapped horn subs (2 per side) have produced significant nulls at off-axis positions (-10dB from center/FOH position). Most notably when standing between 45-degrees to 90-degrees off axis from the pair of subs on either side of the stage.

How do pairs of deployed TH-118s avoid such nulls? Or, is there delay being used with one of the pair? I usually see them with the horn mouth on the ground, set "side-by-side" (not stacked or with wheels opposite of one another), and coverage seems very uniform.

I have experienced nulls with single 18 tapped horns when paired-up and split 25-feet (stage width), even with delaying the outer pair, so I'm curious how the TH-118s avoid this phenomenon.

Title: Re: Arraying horn loaded subs,options?
Post by: Rob Spence on August 10, 2017, 12:07:39 PM

I'm interested in this, as I've experienced instances where "pairs" of tapped horn subs (2 per side) have produced significant nulls at off-axis positions (-10dB from center/FOH position). Most notably when standing between 45-degrees to 90-degrees off axis from the pair of subs on either side of the stage.

How do pairs of deployed TH-118s avoid such nulls? Or, is there delay being used with one of the pair? I usually see them with the horn mouth on the ground, set "side-by-side" (not stacked or with wheels opposite of one another), and coverage seems very uniform.

I have experienced nulls with single 18 tapped horns when paired-up and split 25-feet (stage width), even with delaying the outer pair, so I'm curious how the TH-118s avoid this phenomenon.

You seem to believe that if a sub is a tapped horn design that it is designed well and has been measured to perform well.

Not all speakers that are built and sold are designed well or built well. This goes for any basic design be it horn, tapped horn, reflex, 2 way tops, 3 way tops, horn tops.

There is more to making a well behaved speaker than cutting out some plywood.

You do not identify any of the speakers you have been dissatisfied with. Why?



Sent from my iPad using Tapatalk HD
Title: Re: Arraying horn loaded subs,options?
Post by: Ivan Beaver on August 10, 2017, 12:27:33 PM
You seem to believe that if a sub is a tapped horn design that it is designed well and has been measured to perform well.

Not all speakers that are built and sold are designed well or built well. This goes for any basic design be it horn, tapped horn, reflex, 2 way tops, 3 way tops, horn tops.

There is more to making a well behaved speaker than cutting out some plywood.

You do not identify any of the speakers you have been dissatisfied with. Why?



Sent from my iPad using Tapatalk HD
Agreed.  not all "designs" perform the same.

It depends on the particular "design".

BTW, most of the DIY tapped horns are not done properly, and are missing a key element (NO, I will not say what it is-don't ask).

And as a result, they do not perform like a proper design.
Title: Re: Arraying horn loaded subs,options?
Post by: Eugen Jeličić on August 10, 2017, 08:34:11 PM
Yes, that is the thing. I don't know how these invader bins have been made, are there building mistakes causing problems. But i didn't think that the way a subwoofer box is designed can do very much difference in 40-50-60hz dispersion. Considering how small the box is compared to the wavelenght.

And how can coverage pattern change when you go from one to two tapped horns? Shouldn't they just "couple" at low frequencies? Start working like one box?
Having exactly the same dispersion as one box, just with more power?

I mean there is no room for interference with two boxes playing 50hz staying side by side. Only if the frequency goes up?
Title: Re: Arraying horn loaded subs,options?
Post by: Art Welter on August 28, 2017, 08:52:41 PM

ART:

That's why the lowcut filter is applied right? To stop the driver from exceeding xmax and doing damage to itself.
Just like with reflex boxes. Once you pass the port resonance, the box stops loading the driver well. Therefore the driver starts moving too much and flapping, potentialy damaging itself. So you apply a LC filter?

Or my logics failed me? Can you explain what you wrote up there a bit better?
You claim that driver moves the most almost an octave above the LC.
We set the LC for the invaders at 35hz.
Eugen,
I wrote:
 "Obviously, with high power, a steep HP filter at Fc must be used unless you like the sound of flapping cones ;^)."

A HP (High Pass) filter is the usual name for a Low Cut filter (LC is generally not used, as it can be confused for an LC coil/capacitor network) but as you can see in the FLH simulation, excursion is greatest (other than below FC) a bit under an octave above Fc,  which happened to be about the upper cutoff frequency (Low Pass filter) you chose on the gig in question.

Since the "Invader" has a higher Fc than the examples shown, the upper excursion peak would also be higher than the examples. The 35 Hz HP you used does nothing to limit the upper excursion peak, which becomes the "flap" frequency.

This is true for all FLH, TH, and BR alignments, the only alignment that excursion increases directly as frequency is lowered is a sealed box.

Art