Edgar and Danley: Where the military get their toys.

Years ago, I saw this picture on AudioAsylym, at the High Efficiency section. What/who you see here, is Dr. Bruce Edgar looking happy with the modular subwoofer he has built for the military. I saved the picture, but am not so sure about specific details of the desgn. As I recall, it is several of his refridgerator-sized Seismic-subs together, each extended to give greater mouth area. The military wanted something to "make big booms" and I suspect this is for training situations, exposing the soldiers to near-realistic soundlevels.

Later on, we get this film, about the Matterhorn "device" by Tom Danley. Enjoy.

Weird... But interesting...

There's more video's of similar horns for Andrew Bird, made by http://www.specimenproducts.com. I wasn't familiar with either of them and am glad I stumbled upon these. Enjoy.

PS: I have some corrections for the HM Moreart post, but more about that next time.

Advanced new backloaded horn - RDH20

Many posts ago, I announced that I would be featuring some input by Horst Möller, of the HM-Moreart website. Horst is the creator of a wide range of backloaded horn designs, which has earned him both fans and critics. He certainly has a respectable career, with several of his designs featured in the leading German DIY audio magazines and others interesting enough to manufacturer Visaton to test in their own facilities. The published designs are already somewhat older, but definitely worth checking out. One of them is for Jordan 92-sized drivers, the other for Manger or Seas coaxial-sized drivers. They can be used for other drivers, like perhaps Tang Band coaxials or Markaudio fullrange drivers. A range of Fostex fullrangers and whatever you can think will probably also work. Especially take note of the very extended range down below out of these modest driver sizes. Obviously, Horst was already a capable horn designer at the time.

Horst prepared a piece of text for me, about the use of different materials to construct horns from. Horst advocates the use of soft fiberboard, to make enclosures with excellent internal damping. This is a known use of material for horns and I used it myself in the bass horn described here. I asked Horst to write about it, because he is an experienced and accomplished designer and is a very passionate advocate of this material. A new thing he put forward, was that the material dampens most sound above 200 Hz, which ensures that few higher frequencies

travel down the horn. This creates a stronger crossover between the midrange (from the driver) and the bass (from the horn). Horst was pretty quick to deliver the text, but I lost it in a computer crash. Busy times started around that time for me, so I never really tried to resolve this. To my shame, I must point out. The basic points of the text delivered Horst are stated in this part of his website.

But Horst has done more than design relatively standard backloaded horns with soft fiberboard. Since the earlier published designs, he has started to use double driver configurations, dual horns, different pathlengths to achieve smooth response in small volumes, bipole/dipole configurations and creative space-using concepts (like horns incorporated in seats). Very neat stuff. You understand why he has fans by now. On the other hand, Horst releases half complete plans for "normal" DIY-ers and only supplies fully detailed copies in print and at payment. Some of his designs look less like a horn than most DIY-ers would expect and they clearly don't trust on the good results by looking at the pictures and diagrams. And, it must be said, discussions with Horst about his designs can carry on and on and on, with neither side moving much to either side. These are some of the possible reasons for criticism. Fortunately, this blog has an open and understanding mind for any possible position.

Some months ago, Horst released the first sketches of his latest design, which he calls the RDH20, or Rahmendopplhorn (double frame horn) for 20cm/8" drivers. Typically, the half (in)complete drawings were unclear to many and the predicted response was considered overly optimistic. Some discussion followed, but interest stayed low. I have no doubt that Horst was very disappointed. The past few weeks, looking for new copy and feeling like some modelbuilding, I considered building a Sketchup model of the RDH20. This could help visualize the horn. I just checked Horst's website and found that he now has pictures and measurements of the real thing online. It looks VERY exciting and, perhaps more importantly, VERY clear now, so I decided to fix the deleted text fiasco by publishing this post, about this very innovative design.

Some things to note about this design: There is a forward-firing and rear-firing driver. Depending on choices of the builder, the rear driver can be a woofer or a second fullrange driver. In principle, this design can be a dipole or bipole backloaded horn. The two drivers drive two different horns, of different length and expansion. The idea is that the horns have different peaks and dips and fill in each other's weak points. This principle was known before and is related to, for instance, tapped horns. The inside of the horn is largely made of soft fiberboard, to reduce enclosure sound. The inner horn rests on the outer section via a panel of soft fiberboard, which decouples it. Also notice how the horn mouth is wrapped around the entire enclosure. It is relatively large, yet the enclosure the driver sees is relatively small. Finally, I think it is a beatifully proportioned horn, which draws much less attention to itself than some of Horst's

other designs.

To his credit, and downfall, of most of his designs. He is criticized for strange and peaky/dippy response graphs, but I think they mostly show how tough it is to measure a smooth response in a room. He offers several measurements, from several drivers, measured in several positions. At the very least, the horn does bass. At best, it has response below 30 Hz. Also, he shows how the horns seems to dominate the response, not so much the driver parameters. This is something that people like Klinger also stated and Horst's measurements seem to support his.

On of the great things about Horst Möller, is his continuing drive to create, try, learn and improve. I expect the RDH20 to be just one step along the way and I am curious to see where he will go next.

Tapped LAB, or something like that...

I have been aware of these tapped horn plans, but have been reluctant to post them. I would have expected Danley Sound Labs to be a bit edgy about these plans leaking out, but they don't seem to put much effort in having them taken off line. So hurray!

This thread is a building report of the TH-SPUD by Danley, a regular production model. I always think that DIY-ers can do very good designs by themselves, it is very interesting to see what practical design choices professional make and what the end result is. While I can produce any number of design variations with a linear simulated response graph, Tom Danley knows which variation will deliver in the situations his customers will use his product in. Before tapped horns, Danley gave the DIY horn community the LAB horn, a detailed and perfected design for a bass horn. It gave DIY-ers the chance to build and experience a state-of-the-art horn with predictable performance. "It still is a popular ultimate DIY horn project."

However, we're now in the age of tapped horns and while we have plenty of simulation abilities and there is considerable experience with the tapped horn principle, there has not been such a professionally designed reference tapped horn, such as the LAB is for the conventional horn principle. This is where the TH-SPUD comes in. I am not sure how these plans leaked out, perhaps they were sent to a potential customer to illustrate options and sizes. In any case, they ended up online, including several recommended drivers. Tom Danley even chimed in, in this thread and another, to offer background and advice! Apparently, DIY-builds have his blessing (quite possibly as an afterthought). I guess this is a similar gift as the LAB and I think DIYers will certainly enjoy this one!

I will it to the linked thread to give specifics, I just want to point out the following things:

- it is little deeper as an 8 inch driver (it uses two 8 inch drivers)

- it will work in many locations, but Danley's favorite placement for it is corner placement

- it has breathtakingly extended response

- it has very linear response (check the response graph underneath)

- your room will probably mess that up big time...

Jubilation, again!

The wonderful Klipsch Jubilee build report is back! A new URL, though.

Klipsch Board

It is hard to describe how proud this makes me feel: my list of Klipsch plans mentioned as a resource on the Klipsch board. Grin!

I found it through the referrals section of the hitcounter. The post is also mentioned in this simulation thread, where several woofers are considered in simulations of the Klipschorn, the LaScala and the Belle. It's good stuff. Maybe we can get them to model the Jubilee as well in that thread.

Fixing Bass

I stumbled on to these two examples of multiple subwoofer use. One is the Geddes approach, basically limiting oneself to random placement and playing with cutoff, phase and volume on the submodules. The other, by BD-Design, is more specific, precisely selecting the issue to be dealt with and using a digital crossover and a sub to mirror and cancel the unwanted effect.

Both are effective and interesting.

Impulse resp in Hornresp

A wonderful update of Hornresp. There has been a long list of updates in the tapped horn wizard, but this is (currently) only available for frontloaded horns and direct radiators: simulated impulse response.

Modern Vintage Build, the RT-2/Klason horn

As I have shown, I have a love for vintage designs. I recently posted a link to a thread elsewhere, concerning the Swedish RT-2, otherwise also known Klasonhorn elsewhere. The reason for that thread, was the build by Elbert.

In all the commotion about peceived response etc., the practical and visual side of the project was somewhat neglected. Elbert opened another thread, showcasing his work. He took a very thorough approach to building this horn. Respect!

Geddes and Harman Kardon on subwoofers, bass response

I am thinking hard about my system revision, and particularly the cornerhorn situation. I am reading a book by Floyd Toole, which I will be coming back to later. I have to finish reading it. :) The book is very interesting and is giving me quite a few concept changes about audio reproduction in the home. To paraphrase him shortly, you just have to do what you have to do to make it sound good and then it does sound good. There's a load of data and discussion to back it up, but that's not what I want to talk about. It just triggered me into realising that smooth bass response is a big issue for me (and music in general) and I need to adress it well.

With a single subwoofer or bass source, reflections and resonances in the room lead to peaks and dips in the frequency response, that also differ at varying listening positions. You can try to even them out with an EQ, but whatever is fixed in listening position A makes something else worse in listening position B. And you can take out a peak, but it's impossible to fully fill in the dips as they are cancellations. More power just means more cancellation.

Harman Kardon has a whitepaper about the use of multiple subwoofers and pre-determined, regularly spaced, placement in rooms, which leads to a similar frequency response in the bass range, for all listening seats. This response may be irregular, but it can be equalized flat and the result will be similar and linear bass response throughout the room. The strategy relies on a rectangular room and processing to get the final result right.

Earl Geddes suggests that listening rooms rarely are as predictable in their lay-out and characteristics as the testroom used by Harman Kardon and that this randomness will reduce the positive effects. He also points out that subwoofers placed in regular locations means they will have to be in sight and be very conspicuous. He suggests that randomizing subwoofer placement will work better in the random environment of the listening room, producing a better frequency response in all locations. Randomization basically means put the subwoofers where you think they are convenient. Also, this apparently gives a smoother frequency response even before final EQ and it seems people are getting by without final EQ.

Geddes has a simple approach to get started with placement and to work from there. There is a thread on diyaudio that describes the methodology and Earl Geddes participates in the discussion. There's also some measurements of results. I refer to thread that for the full background. One thing that I do want to mention here, is that Geddes advises to have one main subwoofer, that plays loudest and becomes the source, or the reference subwoofer. Other subwoofers are only there to break up roommodes etcetera, so are all adjusted to disappear into the main response. It is pointed out in the thread that dissimilar subs add to the randomization.

I want to employ this. A big hornsub in the corner and some frequency response smoothing via smaller subs here and there.

About LeCleach horns

There's an interesting thread on diyaudio, where Jean-Michel Le Cléac'h himself is answering questions about his very own horn expansion. The different horn expansion types are based on/follow different assumptions about how sound waves form and travel through air. "Jmmlc" developed one himself. Azurahorns and Musique Concrete horns are LeCleach horns, for instance. It's a very good thread, lots of theory in digestible chunks. Enjoy!

Linked

I am also quite pleased to see this blog is linked to from the Klang & Ton blog. Klang & Ton is a German DIY HiFi magazine, that I actually read. They are bold and creative and not over-analytical of their designs. They also just posted a little review of a horn home project, so we know they have "horn affinity". Welcome to Klang & Ton readers, and feel free to come back.

Been awhile

While this is not a personal blog, and while I don't intend to post a lot about myself, I would like to mention that I started a new job, a long term commitment for a reliable organisation. I am happy to have accomplished this, especially now! New jobs take up extra energy though, so it is hard to do something else. Hence the silence. But let's get on with it!

Big Bertha

Here's a fun horn. GRIN!

Precise details are unknown to me. More pics here.

Note that this thread is in Romy the Cat's domain and he's a... free thinker. There is lots of interesting hornstuff to read there, but keep in mind he is the only one that understands his own line of thought and agrees with it. He may be a genious, he may be a bit... free.

Visitors

Just a quick note, this blog has passed 20,000 visits and 60,000 page views. Thanks everybody.

RT horns, Klason horns

I've been sitting on some stuff about the RT horns, otherwise known as Klason. I was holding back because I've been on about vintage so much already and thought I'd do some new development instead.

In the meantime, a poster over at diyaudio has built one of the later models and is trying to come to grips with it. You can find his thread here.

I just LOVE the Klason/RT horns. Very convenient, very well conceived.

Determining range and crossover

Nice to get some responses to my last post. I notice some heads go up when there is new horn matter created!

I have been playing with the crossover function of Foobar (it's a third party plugin) to investigate how much range I would like and what a 100 Hz crossover sounds like. I have added a screenshot, because it shows sooo much.

What you are looking at, is a two-way setup, crossed at 100 Hz at 24 dB/octave. The top two tracks of the oscilloscope are below 100 Hz, the two lower tracks are above 100Hz. This is with reggae music (bass heavy). Visually, it already indicates the difference in frequency and amplitude. The difference in amplitude is less pronounced with acoustic classical/orchestral music, but the overall impression remains. This is why basshorns must be large.

Next, I kept lowering the crossover point, to where I wasn't hearing much. Although reggae and other music with electric bass guitar isn't supposed to go below around 40 Hz (38 Hz, or 38.8 Hz or whatever according to whoever you are speaking to), I was suprised to learn that I still have all kinds of musical sensations even when crossed around 35 Hz. Even at extremely steep crossover slopes. I could follow the bass lines, both rhythmically as pitch-wise. Reggae is extreme in this area, with strongly accentuated low bass, and I listen to a lot of reggae. It seems it makes sense going for quite a low cut off.

I think I will aim for around 30 Hz lower extension, or lower. I'll compile a shortlist of ready designs next time, or maybe come up with some new design sketches.