Acoustic Horn Co.

2010-08-11T08:55:00.000-07:00

My Wife and I were married at the Moravian Tile works in Doylestown Pa. in 1972.
I was thin then! My wife, Dorothy is just as beautiful, and deserves an award for thirty years of horns.

We had a gigantic sound system consisting of a full size 60Hz Hyperbolic horn and four RCA LC1A speakers, powered by a 60 watt Acrosound, and a 100 watt Grommes tube amplifiers.
The horn was built in 1969 for a hammond B3 organ.

The basshorn had two RCA 15" field coil woofers, and the top end consisted of Western Electric horns and drivers. Notice the the orange horns are conical horns ( three in a row).

We stored the horns at a nearby friends house. His name was Mr. Clemments. He worked for RCA, and said Harry Olson was his boss. He had an immense library of in house RCA journals, the RCA Review. It was the size of a set of encyclopedias.

I read as much as I could, but I never finished as I got married a day later!

I have never seen or heard of these volumes since.

Bill

Interesting Things

2010-07-28T09:36:00.000-07:00

Some of my collection. The first one is a battle anounce speaker used on D-Day in WW two.

Next is a large RCA 10" voice speaker, a RCA 1428b on Twin Power horn, and Lansing field coil coil woofer.

...............and my shop.

best, Bill

News from Down Under.......

2010-04-15T07:53:00.000-07:00

Simon, from Australia, Has a purists system, perfect turntable, really nice amp, and lives in a terrific place.

Hey Bill
1. The Ah 700 horns are running and they are beautiful – very happy with the sound . Soundstage is wide and instruments place precisely. I have been switching back and forth between the Ah horns and some 550 hz tractrix on the same drivers – Your horns are clearer and the treble much more precise and sweeter. They are clearly more neutral. Midrange tone is beautiful
I am still running tractrix for the midbass – the horns are cut out but not yet assembled – too busy at work at the moment but will let you know as soon as they are done
The sound is noticeably less open as you get to the cellos as compared to the violins – the conical are definitely more clear and wide open.
I am very happy with the horns but just to let you know the mounting brackets did not fit once bolted to the driver – the bolt circle is inside the flange on the horn so took a couple of hours with a file to get them to mate – just for future reference .
Thanks Simon

----------------------------July 19, 2010--------------Hi from Bill
Hi Simon,

Thank you very much for your kind words. I'm glad to hear the sound to your liking.

Many years of work and testing have gone into the AH700.... your comments are echoed by others who have AH! horns.

I would be glad to send you a new stand. Filing aluminum is not the most fun.

I now have a precise jigging system and threading machine.

When you get your mid horns going, let me know.

Best,
Bill

------------------------------------------------------------
Hi Bill

My Stuff does not get into boxes very quickly ( thankfully have girlfriend who appreciates the sound rather than the looks ) so most of it is not photo worthy.

The amps are DIY single stage rs241 – parafeed and the photo shows a separate power supply

I use K+K audio phono stage and the Semi DIY table with a Teres signature motor pod and an advanced analog air bearing tonearm with a zyx cartridge

PS, not sure if i said it but you are very welcome to publish any comments

S

From Across the Pond......

2010-04-07T08:24:00.000-07:00

Pete has the ultra fabulous RCA 1428b field coil driver mounted the the AH 300.

He hails from England.An electronic engineer, he has designed his own passive network..really a good job too!

Networks are very difficult

"'I have attached a few pics of the current setup. If I had to describe them in a few words, I think it would be "natural", "effortless" and "sweet". I'm currently using an Audio Innovations First Audio 2A3 push-pull amplifier - I'm in between projects and this is my stop gap amp; not bad, but not the last word. My deck is a Technics SP-10 in a double layer slate plinth, with an SME V-12 arm and Audio Note Io Limited field coil cartridge. Some pics attached also. I'll soon be replacing the deck with a Voyd Reference, which I recently heard and loved - it's a toss up between the Voyd and Technics, but the Voyd does more things right to my taste.

Cheers,
Pete

This time with attachments!

Thanks Bill,

Yes, I had to say these sound *incredibly* natural and there's not a trace of the horn "honk" to be found. The "peak" at 1kHz is not really audible, but I will definitely experiment with a low-Q notch filter. If you have any suggestions, I would welcome them along with any crossover designs so I can compare.

They are sounding absolutely wonderful (more or less tuned by ear). The measure pretty flat, too (see attached). Possibly a touch rich in balance, so I might raise the midrange up a dB or two by adjusting the LPAD (currently at about 10db!).

All the best,
Pete"

15 minutes

2010-03-24T08:50:00.000-07:00

A Friend of mine found this on You Tube.

I do not use You Tube, but I guess I will start

http://www.youtube.com/watch?v=8DPe3Uaxwt4

Be careful of this guy, he has some genetic order pre-disposed to horns

AH 700 in Quebec, Canada

2010-01-21T12:12:00.000-08:00

Hi again Bill,

Here are some pictures.

This system is very dynamic, precise and analytic. Every instrument is reproduced with astonishing realism. No detail is hidden. TAD compression drivers with Beryllium diaphragms are among the best that money can buy. The use of the AH Horns added smoothness and a clearer articulation to the sounds that the TAD reproduced. In fact I tried many horns in the 800 Hz to 12 KHz range, the most important part of the audible spectrum, and none did better then the AH horns (...yet...). Period.

My main sound source is an Oracle Delphi turntable with an Alphason tonearm. A Shure V15 type V cartridge is mounted on the arm and connected to a Hiraga phono preamp. A Krell preamplifier then sends the signal to a pair of modified Rane AC23 electronic crossovers. All the speakers used have a dedicated amplifier. Its a five way active system.

The lowest frequencies are reproduced by 2 JBL 2235H (15" speakers) mounted in an Onken enclosure tuned to 25 Hz. A bridged Bryston 4B SST amplifier is used here.

My satellite speakers are all horns. Bass is taken care of by 4 Altec Lansing 515B speakers mounted by pairs in a modified JBL 4550KBA cabinet. Two Basic M2A Kenwood amplifiers, with sigma drive circuit, are use here.

Mid frequencies are reproduced by a pair of JBL 2482 compression drivers. The original phenolic diaphragm were replaced by Radian diaphragms. Those drivers are bolted to a JBL 2350 horn.

Mid high frequencies are taken care of by a pair of TAD 4002 drivers married to AH horns (in fact this is the cherry on the sundae...).

High frequencies are reproduced by Fostex T-925 horn tweeters.

Mid and high frequencies are all amplified by Basic M1 Kenwood amplifiers, with sigma drive.

My system was adjusted (in the listening room 33' X 18') with a real time spectrum analyzer using 1/3 octave equalizers.

Best regards,

Maurice Daignault

In Good Company...........

2010-01-13T15:02:00.000-08:00

Here is Walter's AH500 with the fabulous RCA 1428 electro magnetic driver, the HF component of his massive RCA theater system. ( four radial RCA basshorns!)
One of the best drivers ever made......

"Hi Bill,

I would have sent this sooner but yesterday when I went to take a
picture I made the mistake of turning on the system to listen and
after two hours had gone by l realized that the light had failed.
I've always thought of a music system as a time travel machine and
this one certainly has the power to transport me. Lifelike, clear,
realistic, powerful- take your pick of adjectives and use them
wherever needed. These sit on top of RCA field coil bass horns and
the 1428B matched to the AH! 500 certainly keeps up. Twice recently
different people have asked me if this was "better than live".
I just smile. I love my horns.

In your debt,
Walter

New Pricing

2009-12-16T16:06:00.000-08:00

Staring in February, there will be a price increase on the AH 700. AH500, and AH700.

The new prices will be listed in a day or two, but not active until February 1st, 2010

They have been sold at a "break even" point until now.

The best of the Season to everyone!

Bill

a Christmas Horn!

Acoustic Horn Company creates designs for RCF Speakers...

2009-11-04T12:37:00.000-08:00

Acoustic Horn Company develops designs for RCF P.A. Speakers.

Click here to visit Bill Woods Design page at RCF

A year's research under contract from RCF has led to the development of these systems.
Designed expressly for High Power P.A. , RCF Precision drivers are a benchmark for high quality transducers.

I might add, RCF is an absolute pleasure to work with.

Best, Bill

The Vitavox S2

2009-10-25T12:00:00.000-07:00

Here are curves of the famous Vitavox S2 on the vitavox radial horn.

Jonathan graciously allowed me to measure it. Despite its popularity, no one has posted a clear curve

Here they are.............

Radial horns always have the smoothest curve ( but not the best sounding)
Shown compared to the RCA 9584 driver on a 350Hz tractrix for comparison.
It is a very nice driver, but needs a HF horn.

Muticell horn tests

2009-10-03T13:28:00.000-07:00

Here are some muticell tests of an RCA 4 x 5 with RCA 1428b (two) Altec 2 x 5 110 deg with Altec 288 driver.

A single cell of the RCA 4x5 at 0 deg an 10 degree
For comparison a JBL 90 degree - deg.

The muticells all measure almost exactly the same off axis.
The JBL horn is down 5dB 45 deg off axis.

Here is PDF of JBL 2553 horn. Note horn is eq'd flat to show off axis curves.

Best, Bill

Acoustic Sounds Website...

2009-09-29T07:32:00.000-07:00

If you like vinyl records, I highly recommend Acoustic Sounds.

This Louis Armstrong version of "St. James Infirmary", is one of the highest fidelity, most moving pieces of music I have ever heard.

It is a 200 gram record, and my order was processed in record time.

A great place to deal with.. and I may start giving this LP away free with each set of horns-- such is my opinion of this particular performance. I also purchased Sonny Rollins "Way Out West"

I hope you enjoy this recording, Bill

http://store.acousticsounds.com/d/8116/Louis_Armstrong-Satchmo_Plays_King_Oliver-200_Gram_Vinyl_LP

There is also a 45 RPM version of Louis Armstrong/king Oliver, but my Thorens TD121 will not play 45 RPM

Required reading...........

2009-09-27T08:26:00.000-07:00

So how good was the sound at the Mill? In a nutshell, the entire experience was fairly ------- amazing.

http://www.6moons.com/industryfeatures/oswaldmill08/oswald.html

The Fostex 30" woofer

2009-09-26T08:09:00.000-07:00

Here are test results of the Fostex Fw800 in a 25 cubic foot box.
there is an error on the graph, it should read "103dB at 32Hz" not 42Hz.
The maximum box size is 40 cubic feet.
It is still in production.

http://www.fostexinternational.com/docs/speaker_comp/pdf/fw800n.pdf

The sd is 615 sq in. An 18" woofer is 200 sq inches. The x-max is 2.2mm.
Note that on a cone this large, there are mechanical limits on how far the cone can move.
I would take a 2.2mm x-max of a 3/4" 18" woofer. the less it moves-- the lower the distortion.

The Fostex is a much better design than the EV Patrician version.

The Legendary JBL Big "Masher" 500-594

2009-07-21T10:48:00.000-07:00

Test curves of the JBL 500-594 driver with "humpback 375" driver.

Note that this lens disperses quite a bit better than the smaller "potato masher" version

The AH 700 was based on this design, but has better dispassion, no "honk" due to exponential flare.

At some point in the future, I will make a Lens for the AH700. It will fit all AH 700 horns, new or old.

Based on the current price of a 500-594, the AH 700 is quite reasonable!

See Cad drawing below.

New E-mail address

2009-07-10T09:51:00.000-07:00

Hello All,

I have recently had my satellite crash, and had to go to another provider.
I live in the woods somewhere and it is difficult to get high speed.
However, all is well now. thank you if you had difficulty contacting AH!

Bill
As penance, I will soon provide test curves of the elusive JBL big round lens ......

Perfect! DYI Backload horn for 8" Fostex

2009-05-28T08:00:00.000-07:00

Thanks to Brad for sending me a set of RCA-fan horns a friend of his built.

Just terrific woodworking. This guy could make piano's!

My Uncle's EV Aristocrats...

2009-05-28T07:45:00.000-07:00

Long ago and far away, the late 1950's, my uncle built these EV aristocrats with the co-ax ev speaker.

They are beautifully built, and still sound good. He also built numerous tube amplifiers, and taught my brother and I the joy of learning how things work, and how to build practically anything.

We built a lot of model airplanes, and learned the nature of flight.

I prefer the experimental sharp edged airfoil, with a terminator thread, as opposed to the Clark Y airfoil.

I would not be where I am today, but for Aunt Urs and Uncle Dick, and those wonderful summer visits.

Dad's New horns..

2009-03-17T07:59:00.000-07:00

Luigi from California, is one of a growing number of people who have a quality bass system, direct radiator or folded horn, upgrading to a horn loaded top end.

A substantial improvement can be made by adding an AH! horn, and the DBX PA electronic speaker management system.

Hello,

I am writing this letter to help whoever is considering buying AH! Horns and is not sure about what he will eventually get.

Before telling you about my system and the impressions from my listening experience with the AH! 700 horns, I would like to spend few words about Bill Woods for those of you who don’t know him yet.

Bill has been a researcher in the field of sound for many years and he developed different solutions in the field of PA: his technical expertise is deep and his passion for music is a clear complement to that; I consider this very important, because very often in this field you find people who love to listen to a system rather than music [ I am quoting my wife…]. Besides his outstanding technical expertise, Bill is a real gentleman who is not in the business merely to make money: he certainly does need to sustain his activity, but obviously for him giving you the ability to listen music at its best takes precedence over everything else. He will spend countless hours to find the best arrangement for your system and he will be open to all sort of technologies: if you just listen to digital formats and you use solid state amps, he won’t treat you with snobbery [ which is something you easily find with other people].

Said this, let me now describe my setup: as sources I have an old Sansui tuner, a Jolida CD player and a VPI turntable; as preamps I have a solid-state Bryston and a tube Audio Research; as power amps I have solid-state Bryston monoblocks and tube Luxman and Quicksilver monoblocks. Before getting the AH!700 horns, I had two pairs of B&W 801, one series 80 and one Matrix Mk2. I decided to keep the woofer section from one pair of them and to use Bill’s horns, driven by B&C de900 compression driver, to replace the mid and the tweeter. Given the difference in efficiencies of the drivers we went for bi-amping set-up with electronic crossovers [dbx].

As for the type of music we [me and my family] listen, it is mainly symphonic music, piano concerts, baroque music and some opera; since a couple of years we started to listen to quite some jazz as well, with preference for female vocals and trumpets players.
Last but not least, we also enjoy a variety of singers, as Bob Dylan, Johnny Cash and Tom Waits – to name a few.

Well, the horns improved the sound clarity, detail and depth of all kind of music.
Simply said, we are enjoying more listening to the same music.
It is not just my impression: it has been also my wife’s statement. She is always very critic of whatever investment I make on the stereo system, but after listening to them she approved the AH! Horns without reserve. The improvement is not apparent.

I can wholeheartedly recommend them to anybody loving music.

Conical Horn Geometry

2009-03-02T10:48:00.000-08:00

I’m often asked how horns differ from one another, and also how different types of horns differ in sound and design, such as exponential, tractrix, and new versions of these which carry the names of their designers. I’ve put together some observations, backed up by actual frequency response curves and measurements, so that people can decide for themselves what types of horns would work best for them.

For the past 30 years I have designed loud speakers for professional applications and more recently for home HiFi. While designing at Yorkville Sound and in the course of my career, have built and tested numerous exponential and tractrix horns. This includes hybrid profiles using a tractrix and a conical which were created to fulfill specific tasks. In professional audio, horns have to work as intended. They cannot be of unlimited size - in fact, there exists an obvious commercial advantage to building the smallest horn to do a given job well. Tractrix or exponential horns are rarely used in professional applications where clarity and coverage are an issue.

In the early 80's I built a four sided conical prototype to be converted to a bi-radial design. I was astounded by how good it sounded so I measured and tested it. This opened the door to the study of conical horns. Some of the characteristics of conical horns are….

Good directivity or power response - the hallmark of the conical horn.
Conicals keep the sound wave at 90 degrees to the wall of the horn at all times as the wave exits the horn.

...After Hughes (Peavey, Also Morse)

(this defines a conical.) The sound wave is not disrupted by the walls of the horn. For these reasons, conical horns have the best sound of any horns for home HiFi Use.

The accidental conical horn

The tractrix profile has been used in commercial products and in DIY. All exponential, and tractrix horns tend to beam as they go higher in frequency due to the squeezing of the side wall of the horn. This results in a "honky" sound and some of the high frequency information is lost, when listening off axis. This is the case no mater what type of mouth correction you might use. The tractrix profile itself is a form of mouth correction.

My first tractrix in production 1989

I have experimented extensively with all types of horns, using absorbing materials, mouth geometry, adding a foam ring at the horn’s mouth, cutting slots, and also with acoustical lenses. (see photo) I have discovered that these devices have, at best, an ameliorating effect, often redistributing the anomalies they try to correct to other places in the passband instead of eliminating them. The acoustic lens holds the most promise.

It is interesting to note that RCA acoustic laboratories analyzed the conical horn flare and mouth termination issues in the 1950's. I am lucky to be in possession of the very lab sample test horns, of which my work is based. See picture.

In listening tests, the rollback using pink noise is very slight. Few individuals have the time, money, space, and technical ability to build and compare using state of the art hardware and software. (I use a TEF analyzer, ATB B&K ,AKABAK, AJ horn software, etc).

I can, however, suggest a simple way to make some experiments for yourself, to see how horns differ from each other in a very rudimentary way. Choose a compression driver, and make a number of very short horns of only 4-5 inches in length ---really horn adapters-- for your driver.
The most critical part of a horn is the first few inches. This is often over looked. Start with a section of straight pipe. Listen to that. It will be very loud, and very colored. Next, try an exponential horn of the same length, then a tractrix - they will be progressively less colored. Finally, try the conical section. It will be the most natural sounding and uncolored.
Musical instruments such as trumpets and trombones are not conical. They are designed to produce harmonics, the very thing we try to avoid in a sound reproducing device. The more the horn is squeezed, the more the harmonics. On the other hand, voice producing devices such as megaphones are always conical.

Horn design is always a game of balancing the factors of length, angle, directivity, low frequency cutoff. There are many ways to tweak a horn’s response. One is to add an exponential throat adapter to a conical horn. This colors the sound, but improves the measurements. Another is to add a secondary flare to a conical to deal with the internal reflection issues.

One other area which deserves discussion is the crucial issue of the beginning of the horn- the throat- and the drivers being used. Compression drivers all have a horn beginning within the driver which you cannot see. The internal geometry of the driver and its phase plug has a direct relationship with the horn.
Sometimes a small exponential throat will be of benefit, sometime it will not. Once again it is a question of degree, and audibility.
If a driver has an exit a half inch, you will likely get to 12kHz, but a driver with a 2 inch opening will be lucky to reach 8kHz. Directivity decreases as the throat diameter increases. Also, if a 2 inch exit diameter driver is being used on a horn expected to go up high, the issue of mouth reflections coming back into the horn pales compared to the very real problem of high frequencies getting “stuck” across the 2 inch throat opening of the horn

As you can see, designing horns is actually a very complex equation involving parameters that all need to be addressed so that an optimal design results. There is no such thing as an “ideal” horn. But certain basic flare profiles work vastly better than others if the best sound quality is the most desired result.

Some general horn examples under test.
I have hundreds of pictures, hundreds of horns, but this is enough for now.

AH 700 with and without flare and throat...it's not as though I missed it somehow...

Itawa horn, and odd drivers I use to cover a complete range of drivers when testing a horn
Also A multiple flare horn after Olson

We stand on the shoulders of giants...

Olson
Holland and Newell

I built the Holland horn soon after his paper came out. the gray one was cut down from a 24" mouth version

Morse
Geddes

Here is 90 deg conical with and without rollback. Also a tractrix, and a tractrix mouth coupled to a conical throat

Danley
Keele
RCA
Western Electric
The US Navy

A battle annonce speaker with special articulation drivers. 119dB 1w/1m!

...and many others.

AH! 1000 system as done by a professional............

2009-01-07T14:10:00.000-08:00

John has made a rigorous scientific design and analysis with his system. To say he is DYI is gross misstatement. Only in professional circles have I encountered such a thorough study of a speaker project.

kudos's to John.

------------------------------------------------------------------------------------
Hey Bill,

"You are more than welcome to use pictures or comments from emails or off my website, list me as a reference, whatever, as I unreservedly recommend your horns."

"I got a pair of AH!1000 horns from you a while back, and I wanted to let you know I've finally made some good use of them. Here's a link to my writeup of them at my website:

http://nullspace.us/tt12.html.

In the end, I really like the horns I got from you. It turned out to be a lot of work and the drivers I picked at first didn't work out that great, but I'm really happy with the final product.

I'll be a starting a thread at the OMA forum in the next day or two, so keep an eye out..."

Regards,
John

Peter Makes an Upgrade...

2008-12-30T10:28:00.000-08:00

Peter from Ontario, Canada, has upgraded from his RCA-fan horns ( now moved upstairs for Home Theater service) to the new, experimental AH 50 widerange basshorn. This is a prototype model.

"exactly what I wanted"
" no horn sound- laid back and neutral sound'
"bass response is excellent"

Note that Peter is using Yorkvile Studio Power amplifiers ( CR5) with a DBX driverack, as well as superb vintage Rotel units.

Nice Grill Solution for RCA-fan backload horn

2008-12-24T15:35:00.001-08:00

Christopher built RCA-fan backload horns, and has come up with a very stylish grill solution!

Christopher feels the cloth grill also aids in high frequency balnce by attenuating the highs from a Fostex Fe 206 whizzer cone. This backload horn, made especially for the Fostex drivers, is available free from acoustic Horn Co.

AH300 - Tom from Colorado

2008-11-27T14:34:00.000-08:00

Tom has integrated the JBL L200 enclosure and LE15 b JBL woofer with the AH300 horn and B&C DCX driver.
Right now the AH300 is hooked to the internal JBL network, bypassing the JBL HF driver.
Tom is adding a DBX DriveRack in the near future. The JBL LE15 b is one of the few, and overlooked, under-hung 15" woofers available today.

Comments from Tom.......

If all goes as planned, I should have an actively bi-amped 3-way horn system throbbing and purring in my living room by next weekend. WOW!!!!!

These things are great.

.........anyway, it has been established that the horns and drivers are flawless.

Thanks again and again for all your help. I will definitely strive to send business your way. Tom

Customer comments on the AH700 and AH 1000

2008-11-17T13:52:00.000-08:00

From Customer Lou, on the AH 1000, and AH700 horns........Nov 8- 2008

Hi Bill.
The 3 Xovers have been completed and in use for three days now. The listening tests and pink noise tests verified that your designs work very well and are a pleasure to listen to. The sound is different than the AH1000's with TAD 2001's. The 2435HPL's should be available to you through JBL Pro Parts but are rather expensive unless you are a dealer. I have both, set up side by side and will email you some photos ASAP. Thanks again

Lou

--------------------------------------------------

You are quite welcome, Bill. I consider myself fortunate having found your horn products and their very helpful designer (that's YOU). Dealing with you has been a pleasure! There are no objectionable points, they just sound different and that's probably due mainly to the drivers being used. I will pass on additional comments to you as I continue to listen to the horns. Good luck on the bass horns. These sound like New Years presents to yourself.
Have a good weekend and continue to take it a bit easy so that you can recover from your surgery. Best, Lou