A site visitor sent me emails saying:

“Johan Dreyer says he can hear no time delay with his bass horns…”

Well, first of all I disagree with it. The fact that Johan Dreyer can hear no time delay is not an indication that delay is not auditable. Johan might not know what specifically to listen or he says it as he has no options to time align his midbass. I would agree that one need midbass time aligned with fraction of inch precision but, even inch does not a lot of difference.  But a number of feet of differences is not a good idea. I might say a lot about the subject as I have a LOT of experience to deal with various aspects of time misalignment.  However, my objectives are not to criticize Johan’s view but rather to use the examples of his (and others) decisions and implementation to nail down what I would like to do with my own playback. My standing is that to use horns without time alignment is not good. I am not saying that if a meticulous time alignment was not implemented then the playback shall be dynamited. BUT, I feel that if the objectives of meticulous time alignment are preliminary goals during the period when a system is architected then why do not consider the alignment? Johan Dreyer has no ways to hear his playback in time-aligned mode, I still do…

Now about the diagram with different time alignment scenarios that Saturntube posted.

The top row is unquestionably the best way to time align. The alternative might be turning the horn way off – it is not a problem at all. A midbass horn does not have need to fire directly to a listening spot and to be on axis. The midbass horns might be even parallel to the walls shooting to the back and to be locate at arrival- aligned location.  In case of rectangular hors it is even a preferable way to do the things as it would allow to use lower low-pass filter and to remove more HF from the horn. The only exceptions from this I see in the Jessie-type horns. Jessie’s horns are full spherical midbass and made to be hanged in air above the MF in time-aligned position.  In my view it is absolutely perfect way to do the things but I am pretty sure that I will not have bolls to go for such a radical (but beautiful) solution.

The bottom line looks like the proper alignment but it is not, particularly the left image.  The alignment is not a pure geometry but the equalization of time arrival. In left bottom image has diaphragms in equidistant position but the wave needs to travel across the bend of the horn and this time need to be considered.  So, in the left bottom scenario the midbass horn needed to be moved closer to listener…

Romy the Cat wrote:

It is very self-explanatory and liked it a lot. The advantage is that it might be used in any rectangular room and the most important that it is VERY simple to build this way. I think that if I have room then I might stop by in a local architecture shape and proposing a few cases of beer I might recruit local students to build foe me a set of plaster walls like this. The wall insets might be even easily removed if I wish so. Very cool!

Yep, if I do it then I will do it right: with a single driver, with full length, with proper mouth, with slow profile and if it had curve then it will be properly linearly expending curve, not with the resonant chambers or with steps. The problem with it only size, positioning and cost. I hope the size and positioning will be resolved in 800 sq feet room. The cost? Well, people do it once in life… How much those things might cost $10-$15K-20K? I do not know. I still hope that if I ready to proceed then I will spend affords and find a right maker (hopefully locally) whom I will be able to motivate not only by the money I pay to him but rather the uniqueness of the project. I have a recursive wet dream that I’ll found at a next street a good carpenter who I will be able to hook on the idea of “better sound” and who would be inspired to hear what his horn will be able to do.

From how I see it now it might be one of 4 scenarios:

1)    If a new home has this option then I will gladly build the things into house structure

2)    If I add in my 800 sq feet to the house then I will consider how it will be done.

3)    If I end up with 1200-1400 sq feet loft in city then it would depends of the width and height. If I have width not 10-15 feet height then it will be rectangular horns on the side parallel with the walls.

4)    If I have 15-25 feet height then it would be hardly anything more beautiful then what Jessie it trying to do:  full size spherical horns hanging ay ceiling above Macondo in time-aligned position. Call be a person with a corrupted sense of esthetics but if those horns are nicely finished then might not looks like two Hindenburgs but rather like two Dally mythical animals, sort of Pink Floyd’s flying Pigs… I will work with light to make is very “interesting”…

JLH wrote:

Alingment is another problem. Maybe an all pass filter could help here without messing things up?

Since I started this thread I have received a number of emails from people bitching that I do not like this, criticize that and that they can’t figure out what I do like. I reply to them invariably – “Do not read my site as you are too much a Moron”. However, besides the devaluing a “secretive” fact that there are plenty of idiots who visit my site there is a useful side element among the inquiry  that those people ask and the question would be – are any properly made commercial midbass horn available out there?

It would be safe to say that I know probably all public commercial midbass horn available and frankly I do not like any of them. It is not that that all of them sound bad (and most of them are) but rather from a perspective of conceptual architecting not of the commercial midbass horn appears to me.  As I said before - I want full length, small through, sufficient mouth, no chambers, no steps, properly continuing-expending slow profile. Any anyone does it commercially? Nope, everyone cheat.

There is only one commercial midbass that remotely fulfill all my demands. I am taking about Western Electric 15A horn. Then 15A is well-know horn with 57x57 mouth and with a very properly made continually-curving neck.

http://www.audioanthology.com/building.htm

http://www.moviemice.com/we/horns/index.php

it has all attributes  to feet my bill of being good horn.

Still being the most properly made among the much worse midbass comparators I am not in complete agreement with what 15A does and would like not to repeat their mistakes. The 15A has near 60Hz mouth but was designed to use with WE555 driver that feel hardly comfortable at 100-150Hz.  The 15A has a presses stress zone at the last bend.  The 15A has a bit too low level of horizontal expansion. And in the end the 15A is something that I call wall-stressed horn. The wall-stressed horn is a horn where circumferential force not evenly presses one side of horn bell. The sound that runs across the 15A horn is like in centrifuge pressed to the outer skirt. The presence of the wall-stressing itself is not so bad - the question is how the stress is handled. If it handled with proper dumpling or proper mass-lording of the stressed surface then it is OK. The 150 point of the 15A is not nearly enough to handle the circumferential force of pressure so the 15A sounds as good as many butterflies will lend atop the 15A while it is working. Sure, there is no “movement of air” in horn a horn and the circumferential force in horn might be visualized only conceptually. I do not have data or evidence about the different pressure in the wall-stressed horns. But I do know that wall-stressed horns with all the rest equal conditions do sound always more surface-colored then horn with mouth that have no pressure obstacles or stressed walls.

What is necessary to make the 15A to sound better then it is.  The 15A must weigh 800 pounds for start and the walls shall be 4 times thinker. Alternative to the beefing up the horn wall would be axis-curving of the stressed surface. In this approach the stress will not be applied to the flat surface as it is done in 15A but despaired across curve that located  transversely  to axis of the horn (the way how it done in Silbatone‘s Aporia). The last curved need to be slightly smoothed up. A ultra-low- exertion driver, capable for full 50Hz , good  TTH characteristic, with the same little throat has to be found - good luck with this one! The 15A as it now shall be OK sounding horn - primary because the small throat and slow horn rate. Could it be better, I bet it might. Still, as it is the 15A probably the less problematic commercial midbass horn among all made.

What would be fun if someone would make the replica of 15A only magnified twice larger! That horn will be able to go an octave lower, will be able to use 4-5” throat with more LF able driver. And the most important is that it will be able to have more space in the curved neck and everywhere else to make the walls of this larger horn very tough and very stiff. If somebody makes a pair of those 1000 pounds double-size 15A horn then invite me – it would be worth to listen. I just afraid that to make the double-size 15A horn will be for somebody much harder than to make the same straight horn.

It is a bit far…

http://atlas.mapquest.com/maps/map.adp?searchtype=address&formtype=latlong&latlongtype=degrees&latdeg=42&latmin=16&latsec=12&longdeg=-70&longmin=45&longsec=30

but it has 114-foot ceiling and it is FREE

 http://www.thebostonchannel.com/news/20303604/detail.html

... and it is "romantic"

 http://www.lighthousefriends.com/light.asp?ID=474  (great read!)

The Cat

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…