Why waveguides/horns?

[gedlee]

Originally Posted by Cal Weldon

I stated that the compression driver without a horn sounds "cleaner" than when mounted.

Have you ever seen the frequency response of an unmounted compression driver? Talk about "colored"!? There are numerous strong peaks and dips in the response that completely go away to a very smooth output when the proper waveguide is applied. Looking at the data, the mounted compression driver is much "cleaner" than the unmounted one.

[Speedysteve7]

Not to mention how horn mouth termination - straight conical or vs rounded mouth and tractric or Le Cleac'h clean things up when measured and sound in room.

Originally Posted by gedlee

Have you ever seen the frequency response of an unmounted compression driver? Talk about "colored"!? There are numerous strong peaks and dips in the response that completely go away to a very smooth output when the proper waveguide is applied. Looking at the data, the mounted compression driver is much "cleaner" than the unmounted one.

[Cal Weldon]

Originally Posted by gedlee

Have you ever seen the frequency response of an unmounted compression driver?

Nope, never bothered to measure one.

Talk about "colored"!? <snip> Looking at the data, the mounted compression driver is much "cleaner" than the unmounted one.

I guess we mean something different by the term "coloured." I am thinking coloured as an acoustic alteration of the original signal. Not to worry, it's such a subjective term that it is difficult to apply measurements to it anyway.

I find many horns have a colouring effect. Perhaps less so with what you are terming a waveguide.

[tvrgeek]

RE post #20
Have people forgotten about Burwin's famous basement?

I don't know if Earls products have moved the industry, his discussions and ideas in the industry certainly have. I can thank him for that having never had the opportunity to listen. I would hope if I ever get the chance, it would remove my bias from the old LaScalla and Altec days. Gad how ghastly. One problem is a proper horn is a tad large for some domestic settings. That prevents me from having a go at one of his kits. Domestic distortion cannot be ignored! A side effect is I would not have looked at the high efficiency pro sound mids he uses. There may be merit there not fully recognized. Speaker building is not the sum of the parts, it is a systems engineering problem which Earl has highlighted.

[mayhem13]

Originally Posted by gedlee

Well I don;t think that I'd agree with that - my crossovers have some 16 components in them. Its not "just a cap". I think thats part of the reason for the bad reputation. The crossovers are very hard to do right.

I think the poster might be referring to conventional dome use where i too have effectively crossed 2nd order with just a cap to a 6.5" mid woofer......don't knock it till ya tried it!

[gedlee]

Originally Posted by mayhem13

I think the poster might be referring to conventional dome use where i too have effectively crossed 2nd order with just a cap to a 6.5" mid woofer......don't knock it till ya tried it!

I reread it and I think that you are correct. I may have misunderstood.

[gedlee]

Originally Posted by Cal Weldon

I guess we mean something different by the term "coloured." I am thinking coloured as an acoustic alteration of the original signal.

Thats the same deffinition that I use, albeit I might be inclined to limit to "coloration" as a linear effect. Most people that I deal with have a pretty stable meaning for the term and its appearance in measurements.

And yes, many horns are colored, and "harsh". Like the Altecs and Klipsch stuff mentioned here earlier. But those are "implimentations" not "concepts". The concept of a waveguide is very attractive, but many of the implimentations are sadly lacking.

[Robh3606]

Hello Cal

I guess we mean something different by the term "coloured." I am thinking coloured as an acoustic alteration of the original signal. Not to worry,

If you take a compression driver with no horn the measure the response it does indeed alter the original signal by quite a bit. Above the mass break point it drops off at 6db per octave. Attached in a plane wave tube measurement on a 2" driver as an example.

I find many horns have a colouring effect. Perhaps less so with what you are terming a waveguide.

You need to get away from 60 year old horns and try some of the newer stuff.

Rob

[Tom Danley]

Why Horns?

It depends what one is trying to do really, when the speakers are closely coupled to your ears, a small very unimpressive looking driver is sufficient for headphones.

Issue one is acoustic power, if you double the distance from the listener to a point source, it takes four times the acoustic power to produce the same SPL. Once the required acoustic power is large enough, Horns are the only practical way of making a single source.
With the efficiency and directivity, it is not uncommon to have a horn based system that is say 10dB or more sensitive than a direct radiator as well as having a higher power handling.
As a result, in commercial or live sound, you find horns are the norm everywhere but the low frequency end where the size required can make that impractical.

Why use one in a home?

Several reasons actually. For one, a horn has directivity, if that directivity was a conscious part of the design of the horn, then one can have an even frequency response over the listen area while not projecting very much energy to the sides or rear.
In a room, close / side wall reflections are distinctly bad so far as the effect on the recorded stereo image and so often one finds a better image when you have directivity over the typical use of domes and cones.

If a nice response curve is a concern at one meter, it is more important at the listening position and in this directivity is certainly your friend. In my room, a set of cone/ dome 2 ways in the spot where the horn sit, produced about a + -20dB response at the Lp while the large horns were more like + -4 or 5dB.

Also, since nearly everything sonically “bad” a loudspeaker adds to the original signal, increases in level faster than the desired signal and so it is as it has been “Headroom is your friend”. It is funny I guess that for something that reproduces a dynamic signal, that the dynamic linearity / reproducing dynamics is not of much concern, unless you have heard proper horns.

Why not horns?

One can take a nice dome tweeter like an accuton and viola, treat it pretty much as a ruler flat component with little fuss. This makes the design of direct radiator speakers simpler right off the bat, the response of a horn is a combination of the directivity vs frequency and the drivers power response and rarely is a horn “flat” all by itself.

So issue #1 is making the horn response flat which often simple crossovers loaded with a complex impedance of a real driver don’t do and this leaves audible artifacts. Until computer assisted design, this was the major problem in many horn speakers of days gone by.

Any driver on any horn will produce sound as seen by some of what is done in hifi with special or antique horns but there is more difference even between drivers than might seem possible.

The home experimenter is at a disadvantage here compared to a manufacturer who may be able to get free samples of all the drivers that “might work”. Some of the things that matter don’t always show up on a data sheet. Unfortunately there is probably as much folk lore about horn drivers as there is gold mining.

We think of a horn as an impedance transformer and it can do that but it also does other things at the same time. For example, at 20Khz with a wavelength of only about 5/8 inch, the impedance transformation has already taken place before the sound even reached the 1” driver exit .

The part of the horn after the impedance transformation controls where the sound goes and then finally well above the horn pattern loss frequency, the big end is essentially uninvolved and out of the way.

The issue of where the sound goes is critical in large scale sound because if you double the room dimensions, you have cubed the volume and so the surface area where the acoustic absorption is, is reduced relative to the volume of air where the energy is stored and so, the average level of reflected sound goes up.
In hifi, the issue is not addressed very much except for acknowledgment of the baffle step effect (big surprise, at the pattern loss Frequency for a 180 degree horn) or speakers like Earls which deal with it consciously from the start.
Anyway, they look simple and take a lot more work to make one that sounds as good as parts that need less tweaking but it can be worth it and if you think of horns like an Altec A7 or other nostalgic antiques, what can be done with horns now has advanced about as much as cars have compared to the 40’s as well.
Best,
Tom Danley
Danley Sound Labs

[Cal Weldon]

Originally Posted by Robh3606

You need to get away from 60 year old horns and try some of the newer stuff.

Geez thanks, I'll keep that in mind.