To horn, or not to horn?

[hoffie125]

The intro:

I'm a mechanical engineering student, and I recently (i.e. fall 2006) took a class on signal processing as part of my curriculum. Suddenly, I became obsessed with speakers and audio in general. Since last November, I have been determined to design and build my own 5.1 system, starting with the left and right front speakers.

The question:

I want to build speaker enclosures only; I have no interest in fabricating the drivers themselves. However, I want to design the cabinets myself - I don't want to take somebody else's project. Although it seems like I have learned a great deal over the last year, there are a couple questions that I haven't been able to get answered just by reading DIY articles, and here is one of the biggest ones: how will adding horns to my cabinet alter the sound of the drivers? The general impression is that it will make the speakers louder, but is that necessarily a good thing? I don't want to impair the soundstage by making the drivers too overpowering or directional.

 

[avaserfi]

I want to build speaker enclosures only; I have no interest in fabricating the drivers themselves. However, I want to design the cabinets myself - I don't want to take somebody else's project. Although it seems like I have learned a great deal over the last year, there are a couple questions that I haven't been able to get answered just by reading DIY articles, and here is one of the biggest ones: how will adding horns to my cabinet alter the sound of the drivers? The general impression is that it will make the speakers louder, but is that necessarily a good thing? I don't want to impair the soundstage by making the drivers too overpowering or directional.

I wouldn't recommend using horn drivers as they usually have rather poor dispersion and generally color sound quiet much. Along side this poor dispersion they also have a fairly low linearity and high resonance. While they do generally make speakers more efficient, thus needing less power to play loudly, their faults do not make up for this IMO.

If you want to make a great speaker be sure to have a highly braced cabinet to reduce resonance as much as possible along with drivers that have flat on and off axis response to get the widest and flattest frequency response both on and off axis with virtually no coloration. Do not forget crossover design. With a build like this I would recommend going full active so you can completely adjust your crossover points and achieve ideal frequency response. Also, to take full advantage of these speakers I would recommend making yourself room treatments and place them properly. For this endeavor I would recommend reading Master Handbook of Acoustics by F. Alton Everest.

edit: What reading have you done so far (which specific articles and books)? I might be able to recommend some more to you which will greatly help the build.

 

[Joe Schmoe]

The only horns I have heard were by Klipsch. They were painfully bright.

 

[fmw]

I'm not sure whether you are referring to horn drivers or a horn enclosure. The Klipschorn, as an example, is a horn enclosure that uses horn drivers. Horn enclosures are simply outstanding - difficult to manufacture, large and expensive to buy. The Klipschorn has a very large mid/tweeter horn. The bass is handled by a 15" horn woofer in a gigantic horn enclosure. The result is fabulous but expensive.

Horn drivers are not very popular in the hi fi and home theater industry mostly because few manufacturers do what is necessary to design the systems properly. Horns are very efficient compared to cone drivers and they play louder than cones as a result. A properly designed speaker system for home use will require quite a few cone drivers at the mids and lows to compensate for the efficiency of the horns and that adds a lot of cost to the system. So home audio designers tend to use cones and domes for the mids and tweeters to prevent having to add so many drivers to balance out the efficiency of the horns.

Horn drivers, on the other hand, are almost universally used in pro audio applications for sound reinforcement because of their efficiency and ability to play loudly.

I think it would be a very interesting project to incorporate a horn driver in a home audio speaker system and design it properly. I once had a pair of large VMPS tower speakers. They had the opposite problem. Each tower had 2 12" bass drivers and a 12" passive radiator. The bass response was ponderous. There were two midrange cone drivers and 5 tweeters per tower and they simply weren't enough. The overall result was a fairly dark sound. They could be tuned to a degree in the bass with modeling clay but they were dark sounding any way you adjusted things.

I always thought the designer would have done well to put a couple of horn drivers with all of that ponderous bass. My woodworking shop is now a warehouse so I don't have access to it for woodworking. If that weren't the case I would test my theory and build up a couple of towers with horn mid/high drivers and those 3 12" radiators. I think it would be very interesting and might work really well.

 

[no. 5]

I want to build speaker enclosures only; I have no interest in fabricating the drivers themselves.

I believe that anyone who can fabricate there own drivers would be the most detail oriented, and well to do DIYer in the world.

how will adding horns to my cabinet alter the sound of the drivers? The general impression is that it will make the speakers louder, but is that necessarily a good thing? I don't want to impair the soundstage by making the drivers too overpowering or directional.

Again, I am assuming you mean horn loading some, or all of the drivers.
From what I have read, it's nothing that can't be dealt with. You just need to know what you want to achieve with the speakers frequency response and dispersion (etc), and some knowledge about how horn loading will affect the drivers you chose.

Horn loaded speakers are typically more sensitive, which doesn't just mean "they are louder", it means they can do more with less power/

 

[fmw]

The only horns I have heard were by Klipsch. They were painfully bright.

In a home theater with a powered sub that is pretty easy to adjust to your preference. You would just raise both the crossover frequency and the level of the sub. That would darken the sound.

 

[fmw]

Horn loaded speakers are typically more sensitive, which doesn't just mean "they are louder", it means they can do more with less power/

Horn drivers are always more efficient. That means they need less input power to reach a given SPL as a cone or dome speaker designed to reproduce the same frequencies. It means they are louder than those same cone or dome speakers at a given level of input power - every time.

If you mix horns with cone speakers in a speaker system, the horns will be louder than cone speakers at the same frequencies at any level of input power - always. A designer needs to add more bass and mid bass volume to compensate or the system will have frequency response peaks around the frequency area of the horns. That compensation can be more drivers or an enclosure like a horn enclosure that accentuates the bass or some other means of compensation. It has always been so.

I can't think of a single exception. There may be one but, if there is one, it eludes me.

 

[no. 5]

Horn drivers are always more efficient. That means they need less input power to reach a given SPL as a cone or dome speaker designed to reproduce the same frequencies. It means they are louder than those same cone or dome speakers at a given level of input power - every time.

Right, I worded my comment the way I did because I think that sometimes people talking about high fidelity equate the ability to be loud with bad sound.

I said typically more sensitive, because I'm pedantic and know of a tweeter or two that is of higher sensitivity than a small handful of horn loaded tweeters.

 

[fmw]

Right, I worded my comment the way I did because I think that sometimes people talking about high fidelity equate the ability to be loud with bad sound.

I said typically more sensitive, because I'm pedantic and know of a tweeter or two that is of higher sensitivity than a small handful of horn loaded tweeters.

I wasn't aware of any. I've never encountered one that was more efficient than a horn. I wonder how they do it with the additional mass to move? It seems counterintuitive.

 

[no. 5]

I wasn't aware of any. I've never encountered one that was more efficient than a horn. I wonder how they do it with the additional mass to move? It seems counterintuitive.

The Aurum Cantus G1 has a sensitivity of 102dB/W/M, and the G3 is 100dB/W/M, which is a bit more sensitive than a few of the cheaper horn loaded tweeters I have seen.

I would be interested to know how, as you said, it seems counterintuitive.