Horn Mounting On Top Of Scoops Question

[ka7niq]

Hell guys, I have the Peavey Speakers in the picture, and I have a question. Should the horn be mounted as shown in this picture, or should I pull the horn forward so the entire front of it's cabinet is flush with the front of the woofer cabinet ?

Peavey 115 sc and Horn top.jpg (133.77 KiB) Viewed 2896 times

[Enzo]

In the real world a couple inches don't matter. If you want to get into the "proper" way, then it isn't the front that matters, it is the source Your horn diaphragm ought to be at the same place as the woofer voice coil.

[dak]

In the real world a couple inches don't matter. If you want to get into the "proper" way, then it isn't the front that matters, it is the source Your horn diaphragm ought to be at the same place as the woofer voice coil.

That doesn't cut it because you need to align the wave fronts at the crossover frequency range, not the sound sources, and they have different phases due to the crossover and different mechanical properties and of course the different acoustic impedance (and sound speed) in the horn throat.

Essentially if you are serious about it, theory is mostly useless and you need measuring equipment and try to figure out the best distance in the range of most relevant frequency overlap (where the speakers put out comparable volume). And there may not even be a single "best" since both speakers will have different sound field distributions in that range and so the results of the combination are different at each angle.

Will it even be relevant? Assuming that the crossover frequency is close to the lower horn resonance frequencies, the wavelengths in question should be commensurate with the breadth of the horn. The frontal displacement we are talking about seems small in comparison, so its effects would seem to become relevant at frequencies where the bass speaker is not contributing significant volume any more.

TLDR: declaring the optimal distance without experimentation or a tremendous amount of acoustical/physical modeling would be rather presumptuous, and it's not likely to make much of a difference in practice.

I'd place it such that it's least likely to get knocked off accidentally.

[ka7niq]

I would think that the way the horn is mounted in the picture I posted would cause diffraction as the sound from the horn hits the top of the cabinet ?
Think about it ?
A Horn has both horizontal and vertical radiation, so would not the vertical radiation of the Horn hit the top of the cabinet, if mounted like in the picture ?

[dak]

I would think that the way the horn is mounted in the picture I posted would cause diffraction as the sound from the horn hits the top of the cabinet ?
Think about it ?
A Horn has both horizontal and vertical radiation, so would not the vertical radiation of the Horn hit the top of the cabinet, if mounted like in the picture ?

The sound detaches from the horn walls depending on its wavelength, so it's only the longer wavelengths which have a chance of getting to the edge of the horn and they won't see a lot of diffraction with those comparatively small features/offsets.

The overhanging parts of the casing don't really have significant acoustic function: they are there for protecting the horn from being damaged when bumping into stuff. I'll grant you that I'd probably look for something to make this more flush because the functional aesthetics are disturbed. Imagine submerging this thing into water and squirting vibrating colored water at high pressure through that horn. The edge is just not where the action is.

[Enzo]

You got a woofer and a tweeter. The crossover separates the signal into the pair. SO we want the sounds from the woofer and the tweeter arriving at your ears at the same time. We don't want the highs getting there a millisecond sooner. The source of sound in the tweeter is the diaphragm, and the woofer can be considered from the voice coil. Ideally, the tweeter dome should be at the same distance from your ears as the woofer dust dome (essentially). Typical speaker box with recessed woofer and small tweeter right out front is actually placing the tweeter too far forward.

In the real world, VERY few people notice the difference, And having toured for years as a sound man, I can assure you the drinkers and dancers barely notice anything, let alone that. But as an academic concern, we want to get it right. One way is to add a tiny delay to the tweeter signal. But that requires biamping and involved circuits. The other way is to simply recess the tweeter to align the dome with the woofer voice coil. This is called time-alignment.

In big honking PA cabs like in the photo, any potential reflections off the baffle and cab elements is just not an issue.

[ka7niq]

Well, I put the front of the horns flush with the cabinet. I tried them sitting back in "time alignment" but I could not hear any difference.

[ka7niq]

You got a woofer and a tweeter. The crossover separates the signal into the pair. SO we want the sounds from the woofer and the tweeter arriving at your ears at the same time. We don't want the highs getting there a millisecond sooner. The source of sound in the tweeter is the diaphragm, and the woofer can be considered from the voice coil. Ideally, the tweeter dome should be at the same distance from your ears as the woofer dust dome (essentially). Typical speaker box with recessed woofer and small tweeter right out front is actually placing the tweeter too far forward.

In the real world, VERY few people notice the difference, And having toured for years as a sound man, I can assure you the drinkers and dancers barely notice anything, let alone that. But as an academic concern, we want to get it right. One way is to add a tiny delay to the tweeter signal. But that requires biamping and involved circuits. The other way is to simply recess the tweeter to align the dome with the woofer voice coil. This is called time-alignment.

In big honking PA cabs like in the photo, any potential reflections off the baffle and cab elements is just not an issue.

Michigan (Oakland County) is where I was born. I have been to MSU football games in East Lansing.
Used to go Deer Hunting by Jackson.

I moved the Horns to where they are flush with the woofer cabinet, and got to thinking. My Ceiling is pretty low where the speakers are, so I jacked up the back of the horns a little to point the Horns more at me, and to try and avoid that ceiling reflection, and you know what ? I think it worked!
They seem to image better, and there is a definite increase in the very top octave. Cymbals sound better. From the front of the speaker, you can't even tell it is raised up in the rear. LOL, I was looking for something to raise them up a little, so I found 2 brand new boxes with eye drops in them.
I got behind the speakers, raised the horn up at the back, and then placed one eye drop box under there, to hold it in position.
I need to listen some more, but it seems to have improved things!

[Enzo]

Well speakers like that are not intended for near field listening.

When I toured with Stankey Steamer I had a custom PA, and we had long throw and short throw horns. I aimed the short throw down more towards the dance floor and the long throw over their heads. The woofers were heard regardless, but the horns were line of sight.

Aim the horns at your face.

[ka7niq]

Well speakers like that are not intended for near field listening.

When I toured with Stankey Steamer I had a custom PA, and we had long throw and short throw horns. I aimed the short throw down more towards the dance floor and the long throw over their heads. The woofers were heard regardless, but the horns were line of sight.

Aim the horns at your face.

When I am seated, the Horns are more then a foot above my head! I tilted them a little towards my face, and can hear the difference, so tomorrow I plan to tilt them even more. I am at least 14 feet away from the Horns, maybe a little more ? A few days ago, I also bought 8 - 24 by 48 Acoustic Panels. Most of them are still in my truck, but the 3 panels I brought in have made quite a difference !
I have them on the side walls at the first reflection points, just jury rigged until I hang them on the walls, sitting on top of a couch, leaning against the walls.

[Dookie]

For the most basic of testing. Find out what the crossover point is your using. Let's say it's 1000hz. If you know how to do it reverse the polarity of ONE of the enclosures. Let's say you reversed the polarity at the amp by reversing the Pos. and Neg. wires at the amp with the cord that is feeding the horn or at the driver inside the horn lens box if your not true biamping now. Now put a 1000hz tone through both the horn and scoop again with the polarity reversed in the channel feeding the horn. To make it easier download a SPL (sound pressure level meter) meter for your phone. Place the phone where your head would be while listening. Move the horn forward and back and see if the level goes up or down. If it goes down in one spot leave it there and put the polarity back to normal on the horn. The signal should now jump up. Do this with only 1 of the Horn/Scoop stacks going at a time.
If you don't notice a change when doing this it could be because the level differences at the crossover point is so great that only the horn or the scoop dominates the crossover frequency area so moving the horn does little to change the level around the crossover point. The other thing to note is the frequencies around 600 hz and up are quite small so a little movement forward/back with the horn may be all that is needed.
This will get you in phase at that listening position but most likely not on the same cycle. To do that you'd need a FFT type measurement system and a delay to use on the correct bandpass. I use Smaart with good results.