Yes, I see the need for a phasing plug for a 40Hz bass horn. Most people choose to ignore the finer details and claim the wavelengths involved are too long to be affected by phase plug. If someone really understands the fundamentals of sound origin, then a phasing plug begins to make sense.

All you have to look at is Fourier transform. All “natural” sound consists of fundamental and harmonics. If a speaker does not reproduce the harmonics correctly, then the tone is not reproduced correctly. It is the harmonics at the higher frequencies that help shape tone.



You can take a sine wave and make a square wave by taking the fundamental and adding together its harmonics. If these harmonics are not added together correctly, then you cannot reproduce the sound. Think about what will happen to the music you play if your speakers did not reproduce the harmonics correctly. The waveform would not look like the original and it will not sound true.

Low E string on a bass guitar has fundamental frequency of 41Hz. However, its 2^nd and 3^rd harmonics have much higher amplitudes. This is normal behavior for a lot of musical instruments. It is very common for the harmonics to have higher amplitude than the fundamental note being played. Below is the frequency response of a guitar. You can see the fundamental being played is centered at about 65Hz, however the harmonics have much more amplitude. The relationship of the harmonics to the fundamental, and the other harmonics are responsible for the tone of the instrument.



So, even if you cutoff the bass horn at 160Hz – 200Hz, it still must get these higher frequency harmonics correct for 40Hz to be reproduced correctly. The real trouble begins when you must have the mid bass horn handle the harmonics of the fundamentals coming out of the bass horn due to the crossover point. You have to get the fundamental coming from the bass horn to sum correctly with the harmonics coming out of the mid bass horn. This is very tricky to get right.

Rgs, John

John, I disagree.

No one deny the importance of harmonics and you are right saying that “If a speaker does not reproduce the harmonics correctly, then the tone is not reproduced correctly.” However you are talking about a complete speaker, not about the narrow operating midbass channel. Yes, the relationship between midbass and upperbass channels will be tricky to set properly. People do not know but people do not use the midbass horns properly. You see typically people having midbass run it all the way up unto lower MF and in THAT case you would be correct. In my case my midbass will be running in very narrow band-path and then I will have a full blown upperbass horn that has no phase plug but it has very HF-able driver, not to mention that two octave above it I have a dedicated Fundamentals channel the takes over… So, the harmonics are not problem to handle properly. In case the people run midbass too wide and particularly in case of improperly folded horns the harmonics become screwed, I would agree but not in case of narrow midbass.

I do not plan to do phase plug on my midbass. Here is for you another reason why. Midbass horn is not upperbass horn. When the upperbass horn that you made for me outputs les say 120Hz then it sends out 8.2 feet wave.  This wave is comparable with listing distance and perfectly “matured” when I reach ears. That is why you upperbass is very much direct-firing type of horn and it does wonderful. Did you try to listen your upperbass from 1-2 feet?  It has completely different upperbass sound that I do not like. In my past I have build a small setup for the position right next to my upperbass mouth. The balance was right but the upperbass was totally wrong.

Not pretend that that my midbass horn shot his 50Hz. It will be 19 feet wave or 6 Meters; the 40Hz will do 25 feet. I do plan to keep my listening distance shorter then this, probably 10-12 feet as max. So, in this scenario I will be in the zone of immature midbass. Bruce Edgar looks like fight the problem with floor firing his 35Hz refrigerator midbass. I am planning to turn off my midbass horns from the listening position to get first bounce of midbass from boundary. For instance if I hang the horn at ceiling then the will be shoring to the back wall near-parallel to ceiling or to the side of the listening position. If I in this situation will do phase plug on my midbass then the sound of the horn from EQ perspective will become directional. I do not what it and I will intentionally use it as non-directional transducer. My idea to use midbass is to load the room, this why I do not want to have overly large room – I will burn the midbass excursion and midbass amp power. The directivity, HF harmonics and the sense of acoustic bass direction with respect to a listening position I anticipate overriding with the upperbass horn.  I would not even mention that a phase plug on midbass would require high order low-pass filtration with more complex phase spin at crossover point.

So, I do not see a phase plug in my midbass. I might remotely agree with it what people use midbass in context of 2-3 ways system but in 6-ways I do not see a need for it.  Also, a phase plug adds compression to the driver.  A 15” driver loaded to 8” throat without a phase plug would have the similar completion (I think) as the same driver loaded to 10” throat with phase plug. If I would be OK with higher compression for my paper-base driver then I would rather go do smaller throat, let say 6” throat. I do not as I feel that it might make my cone too stiff and to over-dumped with compression and with consequential tone diminishing. I am not convinced that it not going to happen even with 8” throat….

Anyhow, they were just a few my own arguments that I have against the phase plug on midbass horn. I have a few more but you the picture… Warn you that I never had a properly made midbass horn and evrything that I expressed is hypothetics and extrapolations form my other experiments. But this position of mine does make sense to me, at least now.

 Jorge, that is good but a few thighs I would like to mention in this approach:

1)    What you depict will work with tractrix or conical horn but not hyperbolic curve. The hyperbolic has own “swell” into exponential curve that would make it to swell differently at different profile rate.

2)    The extensions for midbass (for different throat) will be way longer…

3)     I do not see a practical need to modify throat in midbass. Let me explain why.  If we modify throat in MF driver, let say from 2” to 1.5” then we just replace the bottom of the horn with length compensator, and not a lot of things change. In a midbass a change between 6” and 8” will be 2-3 foot length change and the would require a repositioning of the horn in new time-aligns location. So, it is not so simple, not to mention that sine you have done it one you would hardly do it again.

I have interchangeable bottom on my MF horn. How many times was even considering doing it for 8 years? None! So, I am pretty sure that if a pees make a 4M monster you depicted then it will sit in there for year and years…

Here is an idea that I partially like. I make the horn “invisible” by using a full height of a room; I made just 12” as an example.

This is basically the regular J-horns but it is INVERTED and has a few advantages over what people have done so far.

1)      It has very low footprint. You might laugh but it is.
2)      It has an easy ace to the driver
3)      It is easy to move it across the room -juts drive a new hook into ceiling and re-hand the horn
4)      It is easy to tow it off without changing a footprint
5)      In case the room have very high-ceiling it will be very well will break up the HF typical high-ceiling echo reflections
6)      It has just 3 sections
7)      It is very effectively loads ceiling that “might” allow to go even ¼ size
8)      Since it will be located into-front and on-side of MF then it will act as very effective defuser from side MF reflections, introducing a slight “life-bottom-dead-top effect.
9)      If I cover the bottom with carpet then my Koshka will have a phenomenal scratching post
10)   Since It is vertically inverted J-horn and I do not position my MF above it I have no need to castrate the profile of the bend and I might run absolutely perfect parabolic right across the bend

I show the idea to my Koshka and she like it. She told me that if she climbs all the way atop the horn then I never will be able to harass her again.

skushino wrote:

What is the purpose of having the flexibility to re-configure from straight to J horn? This thing will be large and massive enough that physically moving it from one configuration to another will be difficult and require a lot of effort.  Conceptually it would be interesting to compare each configuration and learn about sound.  Nothing wrong with the idea, but due to its size and weight, is their any real-world application?  I don't think so... I like the other poster's idea of a configurable throat, compression ratio, and back chamber.  Sure it has drawbacks too, but you could learn about the affect of different compression ratios and throat sizes on your driver's behavior.  You also gain more flexibility in case you want to use different drivers.  If you want the ability to modify and control the sound from this horn and driver, why not focus your efforts on the throat-side instead of the mouth?

I think you took it wrong. No one plan to “physically moving it from one configuration to another” and there is absolutely no my desire to have any “learning” experiments with it. If I will do it then it will be done once and right - I will know what I will do. The purpose of having the flexibility to re-configure from straight to J-horn is to have the opportunity do not redo the whole horn is you ever need to go from straight to J-horn or vice versa. To make another mid section is not expansive and complex but it would be possible ONLY if the horn is cut on the sections with the aim that it might be re-configurerable. The horn will be made with sections anyhow – so the slicing the horn on sections might be planed considering a future re-configuration.

Let me die you another scenario. You made the inverted J-horn with enter height of your room.  Instead of hanging it you attach to the mouth two legs on skates (all the way to floor) and not you have a tripod upon which the horn stay: back chamber and two legs. Now you can move your horns as the room looking for the right position using my ideas of the macro-imbedding. After you found the right position for the horns you can hang them there from ceiling but you suddenly discover that in those found positions you do have room to continue the neck of the horn as a straight horn.  In the horn is made with re-configurerable aim then you will mark the found position of mouth, flip the re-configurerable middle sections on the horns (or only on one of them) and then you hand to ceiling completely straight horns . It shall free up a lot of footprint in room and make the horns “invisible”.

Sure it I fill the hors with helium then they might float in the room themselves and I can shepherd them like a flock of geese…

Romy,
there are box-speaker manufacturers that use exactly this approach, so nothing is so new about it. I think Karma and Evolution Acoustics speaker (also layered construction) come to mind, see below.




As to CNC routering, it needs a CNC cutting program written to produce the numerous layers. This would be a cost amortised over the number of cut. But today's CNC routers should make that a pretty quick task as all be different size circles, yes?
The ONLY thing I can see to be an issue, are the ever changing angles / degrees of each 'slice's' in- and outsides. I would imagine your man would still have to smooth them over on a wood-lathe after all is glued up --- it still would be a lot easier since he has the already existing edges to work from.

How could you figure this out? Even if vertical horn is saving space, the other channels would be so far back that space is a problem again?

No wonder I hate horns. Been avoiding them all my life, but now is the time in my life for Horns.

j.