High Efficiency Speaker Asylum: REVIEW: Acoustic Horn Ah! 300 Speakers by Paul Folbrecht

Model:	Ah! 300
Category:	Speakers
Suggested Retail Price:	$300
Description:	300 Hz conical horn
Manufacturer URL:	Acoustic Horn

Review by Paul Folbrecht on September 19, 2010 at 18:25:35
IP Address: 65.30.21.134 Add Your Review
for the Ah! 300

This review actually concerns the combination of the Ah! horns, BD Design Orphean bass bins, and DEQX HDP-3 preamp/crossover/EQ. I am reviewing these three components together for my own convenience and due to the fact that there is a lot of overlap in the analysis of them: I am listening to them as a system. Many of my comments will pertain to one particular component, of course.

In 2006 I attended the Rocky Mountain Audio Show and there heard the most incredible audio system I'd heard before or since: the Cogent "True To Life" horn system. This was an Acoustic Horn Ah! 300 horn along with large bass horns covering approximately 50-300 Hz, both using Cogent's field-coil compression drivers. Amplification was Welborne SET amps, 45 on top and 300B on the bottom, and a DEQX unit was used for digital crossover and EQ. I did not learn until years later that the DEQX unit was used, and when I did, I was all but shocked, as the vinyl reproduction in that room was in the most important ways the best I have ever heard. The effortless detail and dynamics presented with completely natural, fatigue-free smoothness was literally jaw-dropping for me at the time. If someone would have told me at the time that I was listening through a digital processor I would have called him a lying scumbag.

I went through a great deal of gear since that experience, and a lot of it was very good. Especially in my large room, though, I concluded it was not possible to achieve the sort of effortless pressurization, dynamic freedom, and clarity at loud volumes that I experienced with the front-horn system with anything but horns. I had written-off front horns for years as being too large, too complex to do correctly, too expensive, and too un-coherent at my relatively close listening distance of about 10'. (The combination of a very large room with close listening distance is difficult.)

Nevertheless, after several years I had begun to think more and more about front horns. I tried Klipschorns and found that despite their strengths which pulled me in initially I could not live with their substantial horn colorations, still present after various modifications. In fact because of them I wrote off horns for another year. I then decided I want to try some more and was led to the various vintage Altecs: I scored a mint pair of Altec Model 19s which were indeed really, really good. The kind of speakers you could almost never complain about in any way. But there was still a touch of horn coloration now and then, and in my room with close corner proximation it was difficult to get tight bass out of them.

Then, however, a used pair of the Acoustic Horn Ah! 300s became available to me locally along with B&C DCM compression drivers already installed. I decided I couldn't pass this up. I had actually just acquired the Orphean Compact Reference bass bins and wasn't sure what I'd use them with. The original idea was probably the Oris horns, but I had never had the chance to hear them and was a little apprehensive based on some mixed reports. I knew that if there were substantial horn colorations eventually I would tire of them.

My initial go with this setup using a Berhinger DCX2496 for crossover was quite promising - especially after getting correct EQ settings (conical horns require some EQ) it was very good in most areas: the compression driver/horn had very good tone and as expected excelled at detail and dynamics. Yet, I was suffering from some boomy bass as well as a relatively subtle coloration that I recognized from previous use of the DCX (with a very different, open-baffle setup).

My original plan was to get the DCX modded, but I was then drawn to the DEQX unit, especially after somewhat coincidentally just learning that a previous DEQX model had been used by Cogent. The DEQX HDP-3 has the advantage of filling preamp duties as well, with a good analog volume control and a linear power supply - this was more theoretically palatable than putting the signal through an attenuating preamp and then into the digital crossover, both because it is best to attenuate after digital processing and because this setup gets rid of one component in the signal path.

The DEQX software, after speaker measurement, performs not only frequency response corrections but also time & phase adjustments and implements linear-phase, steep crossovers. (At my relatively low crossover point of 400 Hz it would not allow me to use anything more steep than 48 dB/octave for reasons I don't quite understand.)

The system as it stands now is overall the best I have had and close to the best I have heard in most ways. The areas where it is lacking are minor and things I never notice unless I look for them.

One reason I stayed away from horns was the necessity of having crossovers in sensitive areas due to their relatively narrow-band behavior. (On the other hand, I would think about the Cogent system's pretty much transparent crossover and perfect integration, despite sitting under 10' from the huge horns!) Before the DEQX, the transfer from the bass bins to the horns was quite audible, even with a time delay using the DCX. One of the most impressive things to me about the DEQX is the way it made this transition all but disappear - the speakers are pretty close to one-voice most of the time. Yes, when I'm listening to a bass line I can tell you that I am not listening to a compression-driver bass horn but there is no way around that. There is just not as much disparity between the two sound sources as you would think. Instruments that have substantial content from both the bass box and the horn - such as male voices - give away no hint at all of less than perfect coherence. This is quite a feat!

The most impressive aspects of the system to me are the macro-dynamics (and the dynamic linearity across the octaves), the *tone*, the perfect balance, and the clarity and instrument separation.

Of course the system is capable of impressive dynamic swings, from low bass up to the limits of its treble reach. It would surely be more dynamic still with bass horns closer in sensitivity to the mid horn, but it is pretty impressive and leaves about any non-horn setup far behind. The bass bins' sensitivity is about 100 dB/W. The 15" driver can move a bit of air. There is EQ on the bottom giving flat response to at least 25 Hz.

For me, proper tone is probably the #1 requirement of an audio system. Nothing will matter if tonality is off. This is the area where I think the compression driver & horn (I can't say how much credit each takes) really excel. The tone of acoustic instruments - especially horns (which have the most complex harmonic structure, outside of the human voice, I believe) is amazing and is what keeps me listening for really long periods. The tone is deep, saturated, fleshy, and realistic. I believe I am describing a property not directly related to frequency response or even "detail" since in my experience even speakers that are very flat and very detailed don't have tone like this. I haven't heard this tone from other than a compression driver/horn setup - and actually I think the conical horn is better than anything else I have heard. (Although, I have not listened at length to any good front horn setup since RMAF '07. Still, I don't recall being struck like this with perfect tone and also perfect neutrality.) So, I can't say for sure what results in this wonderful tone. I can say the system had it before the DEQX but the DEQX made it better still - probably by removing the DCX's colorations and also, possibly, by achieving flatter response. And better phase?

The next sub-topic is the balance/frequency response. The octave-to-octave balance is extremely good - as you should well expect from a processor that incorporates both speaker and room measurements and corrections. Despite the fat tone, the detail, and the dynamics, the system is never, ever harsh or fatiguing. It will sound thin and not so pleasant on bad recordings but even then it doesn't make me wince like other revealing speakers I've had will. Many people will tell you that horns (horn instruments, that is) are supposed to have bite but having bite and making you wince are two different things. On good material any sort of harshness is completely and totally absent; there is jumpy dynamics and deep tone but with buttery smoothness and lots of clear detail - to me getting dynamics and detail along with real smoothness is one of the big audio holy grails. (I can also say the sound is the farthest thing from having any kind of 'digital' sound signature.)

The DEQX does not seem to have hindered transparency in any way whatsoever. Good recordings - especially vinyl - are as transparent as I've ever heard. (I'm suffering from a bit of a noise issue with my analog setup but I'm able to listen past that.) The digital source sounds like digital (and digital from my Audio Note Kits DAC is pretty impressive) and vinyl sounds like vinyl - it takes everything up a notch from the digital. (I am really liking the XRCD sound, though - really took the jazz horn smoothness up a notch.)

I have read people opine that while digital EQ corrects many problems it also tends to "suck the life out of the music" or something similar. I am finding, after daily listening for several weeks now, that is not the case at all - and I was skeptical that I would cotton to this setup, frankly, despite the Cogent experience. If I can say I have heard systems that sound a bit more "lively" I can also say without exception that those systems suffered from frequency response far from flat and I have my suspicions that it was peaks - broad or narrow - that result in that sense of increased "liveliness".

Lastly, instrument separation and clarity are top-notch. As much as I love a coherent two-way dynamic speaker (such as the excellent Audio Note AN/E) they cannot keep it together on loud, complex music, at least not in a room like mine. I guess it takes sheer driver area and/or horn-loading to do that.

My take on what contributes to the overall excellence of this setup, in order, are the mid horn/compression driver, the DEQX, and the bass bins, in that order. The sound signature of the Acoustic Horn/B&C setup is consistent across other gear changes and contributes "most" to the overall sound of the system. It gives about the best midrange possible, I believe (surely a vintage RCA or new Cogent field-coil driver would be a step up). There are no horn colorations whatsoever yet all other horn advantages are present. The need for EQ would be the one weak point but it is simple enough that it could be done passively as well.

The DEQX HDP-3 is really an amazing piece of equipment. Utterly transparent, with no 'digital signal' whatsoever that I can discern, it functions as a nearly perfect crossover, EQ, and preamp. It does not offer a pleasant opinion like many tube preamps can, and I suppose that could be called a 'disadvantage' - I know & love the Shindo sound, for instance - but that can hardly be expected. It seems to do what it sets out to do nearly perfectly.

The bass bins are very good at what they do. Certainly horn bass would be superior but at the cost of being far larger, heavier, and more expensive. As a bass solution fast and dynamic enough to keep up with horns it succeeds, if not perfectly (which is impossible), than admirably.

Weakness - I could name only a couple, which have been hinted at. I am not using tweeters, and using what is really a midrange horn for highs as well is not optimal. The DEQX EQs it very well, and the B&C drivers are good to 14K or so, but it is not as good as separate, hi-eff/horn tweeter would be. But I hardly mind, at all, and doubt I will ever change it.

And the bass, as noted, is not really up to the level of the mids. The DEQX's room EQ did a great job at getting rid of any bloom in the bass, but a big bass-reflex box is what it is and does not have the qualities of a horn. They do give away their presence now and then. But, and I stress, the bass is still very good. I could not live with the system otherwise as I love acoustic jazz bass. There is excellent tone, excellent reach (due in part to the EQ), and the bass is taught and tuneful except in the lowest registers, on occasion. (I'm certain that if I EQed for less flat response down low I would get better acoustic bass: it is those lowest overtones that always cause that bit of resonance. In my experience it is systems that do roll off below 40-45 Hz or so - such as the excellent Lamhorn - that do stand-up bass best.)

I am calling the system essentially done. I have a desire for bass horns and would like to go there some day but I can take my time about that. I know it will mean greater complexity as I will need subs below the bass horns as well. With only 10' between me and the speakers, which are almost flush the corners, space is the biggest enemy to a bass horn setup.

System:

Digital Source: Audio Note Kits DAC 3.1 Signature fed by Mac Mini
Analog Source: Thorens TD-124, Shure V15, Audio Note Kits Phono Stage
Preamp/processor: DEQX HDP-3
Amps: Korneff 45 SET (mid/hi), McIntosh MC-2125 (bass)

Product Weakness:	See review
Product Strengths:	See review

Associated Equipment for this Review:

Amplifier: Korneff 45 SET (mid/hi), McIntosh 2125 (bass)
Preamplifier (or None if Integrated): DEQX HDP-3
Sources (CDP/Turntable): Audio Note Kits DAC 3.1, Thorens TD-124/Shure V15/AN Kits Phono Pre
Speakers: Acoustic Horn Ah! 300, BD Design Orphean Compact Reference bass bins
Cables/Interconnects: Anti-cables, Gabriel Gold, Mapleshade speaker cables, VH Audio PCs
Music Used (Genre/Selections): 40s, 50, 60s, Jazz, Rock, and Pop
Room Size (LxWxH): 30 x 25 x 15
Room Comments/Treatments: Open-concept house
Time Period/Length of Audition: Two months
Type of Audition/Review: Product Owner

Amplifier:	Korneff 45 SET (mid/hi), McIntosh 2125 (bass)
Preamplifier (or None if Integrated):	DEQX HDP-3
Sources (CDP/Turntable):	Audio Note Kits DAC 3.1, Thorens TD-124/Shure V15/AN Kits Phono Pre
Speakers:	Acoustic Horn Ah! 300, BD Design Orphean Compact Reference bass bins
Cables/Interconnects:	Anti-cables, Gabriel Gold, Mapleshade speaker cables, VH Audio PCs
Music Used (Genre/Selections):	40s, 50, 60s, Jazz, Rock, and Pop
Room Size (LxWxH):	30 x 25 x 15
Room Comments/Treatments:	Open-concept house
Time Period/Length of Audition:	Two months
Type of Audition/Review:	Product Owner