Sunday, December 28, 2008

Development Project

There are many things to consider when working on your dream loudspeaker system. Physics, technology, the cool factor. Another one is living around the thing. In my case, after moving to a new house, the system is proving too large to be practical. I am using LaScala bass horns (filtered to have flat response to 40 Hz) and horns with fullrange drivers for midrange and (some) treble. Due to the layout of the room, we have to sit pretty close and the integration between bass and the rest is hard. It also looks imposing and my girlfriend and I keep bumping into the things.

I have come to the conclusion that it's better to change my approach and my system. I'm looking towards cutting edge and vintage answers to this problem. Some of the legendary hornsystems were cornerhorns and some of the arguments for using corners were that they provide opportunities for excellent bass response and are convenient use of space. (See Klipsch for reasoning.) In my personal case, I only have one corner available and I am not about to go mono. Luckily, there's plenty of material that suggests that at a cutoff of 100Hz or below, it's impossible or at least very hard to locate a sound source, so going with something other than stereo below 100 Hz is OK.

Based on this, I have decided to take a new approach to my system. I will build a horn, to be placed in a corner, for frequencies below 100Hz and will have to stretch the mid/high sections' response down to that point. Exactly how, I don't know yet.

Now, a horn in a corner is still a wide concept. I can go for a frontloaded cornerhorn (Klipschorn, Jubilee, Hartsfield), a rearloaded cornerhorn (Jensen, Tannoy, Schmacks), I can stuff a tapped horn in a corner, I can design a frontloaded, rearloaded or tapped horn myself for in a corner. The DIY (do-it-yourself) and DIY (design-it-yourself) options sound good, so I hereby announce my horn design project.

I will have to work out parameters to work with. I need to decide on desired cutoff and acceptable size. We may simply end up with the conventional tapped horn coffin, but we might end up with something very different. Of course I have ideas cooking. One hint: think Olson...

7 comments:

Benkev said...

Hello Ivo. Before you reinvent the wheel you might want to take a look at the LAB bass horn project. Documentation can be found here. http://www.prosoundweb.com/article/lsp_documentation_page_drawings_photos_specs_and_more/ And an adaptation that may be of interest to you can be found here. http://www.livesoundint.com/archives/2003/dec/means/means.php Keep us posted on progress.

Philip Barrett said...

Firstly - please describe for us LS owners the "flat to 40Hz filtering."

Second - don't forget your LS's will reap most of the benefits of a corner horn merely by placing them in a corner! I have mine situated in just that fashion. The bass produced from cabinets lacking a rear driver/phase configuration (mostly seen in concert systems) is omnidirectional to all purposes.

Third - you are correct about the ear's inability to detect LF direction & the upper limit is actually closer to 200HZ so a single in a corner would be fine. The awesome sub-woofer action you hear at concerts is almost always mono and in fact placing stereo subs will generally cause more problems (cancellation/comb filtering) than they solve.

Happy to discuss further if you like. My e-mail is philipbarrett2003@gmail.com

Philip Barrett said...

So how about that La Scala bass tip? We're waiting!

Ivo Tichelaar said...

Philip, thanks for your interest. My LaScala's are fitted with Altec 416 drivers (non-standard, clearly). These drivers have a roughly 12 dB/octave lower roll-off, starting at 200Hz. I use a passive line level filter to EQ the bass flat. Efficiency at 200 Hz is very high, I use a 6dB/octave lowpass equalizing from ~45Hz upwards and another 6 dB/octave lowpass from around 100 Hz upwards. The range from 100-200 Hz is flat by filter, the range from 40-100 Hz is flat by filter and increasing roomgain with decreasing frequency. This driver choice and filtering strategy was thought up by Bert Doppenberg of BD-Design, I actually bought his. The great benefit is maximum efficiency at crossover-point, which matches well with high efficiency midrange drivers. The transition between midhorn and bass horn is great (great for cello etc), but these things are just too big in my home.

Ivo Tichelaar said...

As for the LAB and other readily available projects, I am aware and I am keen! :)

KAREL said...

Hi Ivo,
I think, you have a nice dream project "common corner horn" .....
I think , it would be give wonderfull music.
There is a study/project/réalisation of this (nice) horn in the French "AUDIOPHILE" ....(and other forums).
The concept: it (one horn) take place in the corner with driver (close cabinet) on the floor and the mouth at the ceiling ....nice.
Ivo, do it.
Allez, salukes.
Karel

Ivo Tichelaar said...

Hello Karel,
You are the man with the Western Electric BIG horns, aren't you? Wow! Welcome to this blog...
Do you have a link to the French horn you describe? I would like to take a look. Thanks!