Building a world-class Horn system for Small Rooms

After nearly 7 years, I think it's time to create a thread for my journey, in the hopes that it may inspire or help others with their own audiophile ambitions. My hypothesis was that world-class reproduction could be achieved in a small (~11'5" x 12'8" x 7'8) room. I think I have achieved it. I will post more photos and videos of playback over the next few months.

While my audiophile journey started many years before, the desire to create a world-class (almost) no holes barred system for my media room started with a visit to Oswald's Mill Audio (OMA) in Brooklyn and reading their (now removed) DIY meet summaries ("OMA Tastings"). If you have never heard a well-designed horn system close this window and go and find one, then come back. OMA has a beautiful showroom in Brooklyn. You should also listen to the Klipsch Jubilee at HiFi Loft in NYC (I have no affiliation and have never been). Be careful with horns from other manufacturers - not saying there aren't others, but it's more hit than miss.
 
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Objective:
Achieve world-class audio reproduction for both music and movies in a small room.

First challenge: Size
Most horn systems are large, and for good reason. You need a large horn to reproduce low frequencies.
I got around this by using a vertical transmission line active sub. It blends perfectly with the other drivers.

The main speakers are only 18" wide - a critical dimension for a small room of less than 12' total width. Depth is 24" and height is 66".

The sub is about 12" x 6" and 66" tall.
 

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Congratulations on the courage to realise such a horn project in such a small space. Very cool! I really like the speakers themselves, lots of beautiful wood. I hope they sound as good as they look. In any case, I take these horns as a sign not to doubt the use of horn speakers in my moderately large room. ;)
 
Did you try different horn profiles before settling on the multi-sided conical for the mid range? I've built and listened to a few of those after being inspired by the Oswald Mills write ups. I know the guy who designed those is really against any use of a round over or any kind of curvature in a horn for hifi use in the midrange, and I know he has extensive experience with horn design. I still don't feel I understand his argument. A big round-over on the mouth makes the whole horn bigger and more expensive but it also smooths out the on and off axis response considerably due to significantly lower diffraction. The ones I built all demonstrated the mouth diffraction. I will say they sounded good even though the response looked relatively messy compared to other horn flares with round-overs.
 
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Did you try different horn profiles before settling on the multi-sided conical for the mid range? I've built and listened to a few of those after being inspired by the Oswald Mills write ups. I know the guy who designed those is really against any use of a round over or any kind of curvature in a horn for hifi use in the midrange, and I know he has extensive experience with horn design. I still don't feel I understand his argument. A big round-over on the mouth makes the whole horn bigger and more expensive but it also smooths out the on and off axis response considerably due to significantly lower diffraction. The ones I built all demonstrated the mouth diffraction. I will say they sounded good even though the response looked relatively messy compared to other horn flares with round-overs.
Hi, no, I didn't because I was impressed with what I heard at OMA and I know that he built the business on the ideas and experiences of a talented community of DIY audiophiles. Also, the reasons why conical are best just made sense inherently.

Response is very good, 800-8000Hz +/-2 dB. We actually got it even flatter, but I prefer the slight emphasis.
The crossovers have custom-made jumpers so you can try it both ways.
 

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Congratulations on the courage to realise such a horn project in such a small space. Very cool! I really like the speakers themselves, lots of beautiful wood. I hope they sound as good as they look. In any case, I take these horns as a sign not to doubt the use of horn speakers in my moderately large room. ;)
Thanks! It's been a fun and interesting journey. I'm glad I did it, after OMA turned me away(*), but I would not do the DIY route again.

For a second media room, I currently have the Klipsch Jubilee and Wilson XVX on my short list. Yes, the Wilson are not horns, but that's ok. With a large, purpose-built room and at that level, they should and do sound great. (I don't think they quite match the midrange tone on vocals of my RCA1443 + Bill Woods' conical horns though!).

[* After calling out OMA on why they claim that a ~90dB efficient speaker can be adequately powered by a ~2W amp (they can't!), Weiss told me to get lost. And that was at the start of a journey in which I spent close to $500K (speakers alone were a lot less). I just had to share as it's too funny and it brings to mind that scene in Pretty Woman.]
 

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An interesting project, but I'm a bit confused. You have quite a bit of gear including a Trinnov and several amps. What exactly are you driving the horns with? Are you using DSP for them?
 
Objective:
Achieve world-class audio reproduction for both music and movies in a small room.

First challenge: Size
Most horn systems are large, and for good reason. You need a large horn to reproduce low frequencies.
I got around this by using a vertical transmission line active sub. It blends perfectly with the other drivers.

The main speakers are only 18" wide - a critical dimension for a small room of less than 12' total width. Depth is 24" and height is 66".

The sub is about 12" x 6" and 66" tall.
Fascinating, as I inherently like horns, especially the custom projects, like yours.
Could you share info on the drivers, x-over design(1-st, 2-nd order) and x-over frequencies, please?
 
An interesting project, but I'm a bit confused. You have quite a bit of gear including a Trinnov and several amps. What exactly are you driving the horns with? Are you using DSP for them?
Sure, I wanted the system to first be ideal for music (2-channel) reproduction; but also for movies. Music reproduction is a lot more demanding than movie reproduction, so starting with music first makes sense.

Most HT speakers are terrible for music reproduction. I'm a big believer in 'less is more' in terms of speakers for home theatres, especially in small rooms. There is usually no need for a center channel. Spending the same budget on fewer speakers and amps will also lead to better sound. Yes, I did get a Trinnov, but mainly because of its virtualization tech for speaker placement and because you can use an external DAC.

The Trinnov is very, very good at surround processing. So much better than my previous Denon 8500 with Audyssey.

Powering the horns are the DarTZeel 18NS and 108 pre and power amps. I was using the Kondo Japan M77 and Souga - these are nice, but the DarTZeel is significantly better.

No DSP - other than for subs, I think DSP is a band-aid that is best avoided. Why? Because you're converting A to D to A, two extra conversions which definitely reduce quality. Get it right with room treatment, seating positions, and the right equipment instead of using DSP. For the high-end, anyway, DSP should be avoided.

Crossover is passive using massive Duelund CAST Tinned Copper caps (you can see one on the wall behind the horn).

Trinnov is only used for multi-channel movie playback. The main channel digital out is converted to analog by the Nagra DAC, which then goes to the DarTZeel preamp. There are 4 additional surround channels, powered by a (soon to arrive) Apollon Purify amp and Klipsch in-wall speakers.
 
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Fascinating, as I inherently like horns, especially the custom projects, like yours.
Could you share info on the drivers, x-over design(1-st, 2-nd order) and x-over frequencies, please?
Sure:
Active Subwoofer: 20-60 Hz [500W Yung plate amp with 12" driver (don't know the brand), passive crossover]
Upper bass: 60-600Hz
Supravox 285-2000EXC

Midrange: 600-8000Hz
RCA1443 + Bill Woods AH300 Conical Horn in Maple

High: 8000-20,000+
Fostex T500aMKII

1st order from bass to midrange; 2nd order from midrange to high.
Sorry, I cannot share the crossover circuit. I retained one of the world's best audio engineers and crossover designers and he asked me to keep the circuit confidential. You can see it on the wall actually, so it's really simple!
 
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Hi, no, I didn't because I was impressed with what I heard at OMA and I know that he built the business on the ideas and experiences of a talented community of DIY audiophiles. Also, the reasons why conical are best just made sense inherently.

Response is very good, 800-8000Hz +/-2 dB. We actually got it even flatter, but I prefer the slight emphasis.
The crossovers have custom-made jumpers so you can try it both ways.
One of the advantages of horns, especially in smaller rooms, is controlled directivity. This is why you usually see rectangular horn mouths, since they are better at minimizing side wall reflections which contribute to harshness. To be clear, when the horn mouth is rectangular and the width is horizontal, the dispersion is vertical.

With a conical horn in a smaller room you may well find that in order to get them to perform properly, you might have them toed in such that the axis of the horn is crossing in front of the listening chair.
 
Thanks @Atmasphere - very good points that are not well understood.
What do you think the differences are in dispersion in a folded bass horn like mine vs the Klipsch LaScala? Note that the LaScala is oriented in the opposite direction.
 

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I broke one of the 3 turnbuckles that hold and position the midrange horn yesterday when trying to adjust the position of a speaker! I want to replace them with brass or something that looks better. Does anyone have any ideas?
 

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Thanks @Atmasphere - very good points that are not well understood.
What do you think the differences are in dispersion in a folded bass horn like mine vs the Klipsch LaScala? Note that the LaScala is oriented in the opposite direction.
At bass frequencies dispersion isn't an issue since the waveforms are so long. Its not until you get much higher that dispersion becomes an issue. This is why the LaScala has the tweeter, since it can disperse more widely than the midrange can at higher frequencies. Yet still we can see that its dispersion is optimized vertically so as to avoid side wall reflections.

I forgot to mention that one issue with round horns (trumpets) is beaminess at high frequencies- which rectangular horns outperform. If its only one person listening this might not be an issue, especially in a smaller room. This problem is really similar to 'full range' (which never are) drivers, which are also beamy at high frequencies and for much the same reason. Personally I don't like having to hold my head perfectly still; its nice to have a little wiggle room.

Its pretty easy to find brass turnbuckles. You can also get aircraft grade turnbuckles that allow greater tension, but you might have to get creative with the anchor points since the eyes that they have are smaller.
 
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Sure:
Active Subwoofer: 20-60 Hz [500W Yung plate amp with 12" driver (don't know the brand), passive crossover]
Upper bass: 60-600Hz
Supravox 285-2000EXC

Midrange: 600-8000Hz
RCA1443 + Bill Woods AH300 Conical Horn in Maple

High: 8000-20,000+
Fostex T500aMKII

1st order from bass to midrange; 2nd order from midrange to high.
Sorry, I cannot share the crossover circuit. I retained one of the world's best audio engineers and crossover designers and he asked me to keep the circuit confidential. You can see it on the wall actually, so it's really simple!
Thank you,
Understand about the proprietary x-over design. So the wall-mounted looks like the midrange-high 2nd order?
1st order should be just one cap, one coil and 1 resistor.
And you have only 1 LF driver in the bass horn?
 
Thank you,
Understand about the proprietary x-over design. So the wall-mounted looks like the midrange-high 2nd order?
1st order should be just one cap, one coil and 1 resistor.
And you have only 1 LF driver in the bass horn?
The entire crossover is on the wall. You can see all the components. It would have been half the number of resistors but they weren’t available in the required value.
 
At bass frequencies dispersion isn't an issue since the waveforms are so long. Its not until you get much higher that dispersion becomes an issue. This is why the LaScala has the tweeter, since it can disperse more widely than the midrange can at higher frequencies. Yet still we can see that its dispersion is optimized vertically so as to avoid side wall reflections.

I forgot to mention that one issue with round horns (trumpets) is beaminess at high frequencies- which rectangular horns outperform. If its only one person listening this might not be an issue, especially in a smaller room. This problem is really similar to 'full range' (which never are) drivers, which are also beamy at high frequencies and for much the same reason. Personally I don't like having to hold my head perfectly still; its nice to have a little wiggle room.

Its pretty easy to find brass turnbuckles. You can also get aircraft grade turnbuckles that allow greater tension, but you might have to get creative with the anchor points since the eyes that they have are smaller.
Conical horns do not beam. Perhaps it’s just the Bill Woods design, but this is one of their main advantages. Ok, I see you specifically wrote “trumpet” shaped. Conical have flat and non-parallel sides so they are not the same.
I can be upstairs or in a different room and it sounds like a live band is playing in the house.
Visit OMA and read his literature on conical horns. It’s nothing new, just not well understood; probably a function of how few correct designs there are.
 
Hi, no, I didn't because I was impressed with what I heard at OMA and I know that he built the business on the ideas and experiences of a talented community of DIY audiophiles. Also, the reasons why conical are best just made sense inherently.

Response is very good, 800-8000Hz +/-2 dB. We actually got it even flatter, but I prefer the slight emphasis.
The crossovers have custom-made jumpers so you can try it both ways.
Is that a CRT you're using there? That does look very good. I could also get good measurements but it depended on where I measured. Best was slightly off axis. I guess what would need to be done is a full spin-o-rama to see how it all averages out. It may be that it comes out good on average even though it looks rough at certain angles and distances.
 
Is that a CRT you're using there? That does look very good. I could also get good measurements but it depended on where I measured. Best was slightly off axis. I guess what would need to be done is a full spin-o-rama to see how it all averages out. It may be that it comes out good on average even though it looks rough at certain angles and distances.
Ha! That’s actually a NEC LCD Multisync monitor. Not mine, the crossover designer who is “old school”.

This was measured in room, but with the mic quite close and on axis.
The Trinnov 3D measurement at the listening position is not much different.
 
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