GoodSoundClub - Romy the Cat's Audio Site - Vertical Axis Midbass Horn

Horn-Loaded Speakers
Topic: Vertical Axis Midbass Horn

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Posted by skushino on 08-08-2012

I've had a long-time desire to replace my Edgar 80hz midbass shells with a better performing solution. My Edgarhorns arrived in 2005, and I made incremental improvements over the years until now they have little in common with the original Edgarhorns, besides the MR and 80hz horns. The MR will be replaced in the future, and replacing the 80 hz horns is the subject of this post. There's a fuller description of my current configuration in a past post. My bass is actually listenable now as is, due to a lot of effort, many failed experiments, and two or three successes. But it could still be better. I think much better... The problem, like anyone who dabbles with horns knows, is coexisting with bass horns in a typical residential listening room. Mine is 15' x 18' x 8'. I've exhausted the typical solutions and discarded each for various reasons: front loaded horns, folded horns, onken box, sealed box, and line arrays.

The purpose of this post is to explore bass-sized vertical-axis horns, as used by Bruce in his subwoofer and Slimline designs, and more recently by Tuneaudio Anima. My desire is to use a pair of bass horns for each channel, both vertically oriented, one each exhausting to the floor and the ceiling. I have an idea that spatial presentation will gain a big boost with both up and down firing bass horns. bty I had the Edgar subwoofer and it sounds surprisingly good, considering everything. Like a helicopter that looks like it shouldn't fly but does, the Edgar Seismic Sub looks like it can't sound good, but does. It could be straightforward to fabricate a pair of 55hz horns, around 5' long, same sized mouth as Anima (~1100 sq in, 8 sq ft), with one pointing up and one down. A second pair would be made to complete the bass channel.

The Anima was discussed here in the past:

http://www.goodsoundclub.com/Forums/ShowPost.aspx?PageIndex=1&postID=12129#12129

My Goals:

- Replace Edgar 80hz horns
- No folded horn architecture
- Both floor and ceiling loading for full spatial reproduction
- Gain horn eq down to 50 - 60 hz
- Limit sub bass upper cutoff to ~40 - 50hz
- Hf upper limit ~ 300hz for 180hz crossover to lower midrange channel

My Concerns:

- Which driver to use? 12" - 15" are the obvious choices to balance low-end displacement and seamlessly match lower midrange @ 200hz
- Time alignment with other channels. Need clarity on how to measure. Is it distance from driver to listener, or need to include horn path length in consideration?
- Hf limit
- Imaging and soundstage considerations with horns not pointing at listener
- Driver cone sag in vertical orientation. Is this a credible concern or too much hand wringing about nothing?

I'll post more thoughts on this topic in the future. IF anyone has first hand listening experience with the Anima, or other design considerations to share, I would like to hear your feedback.

Posted by Romy the Cat on 08-09-2012

skushino wrote:
My desire is to use a pair of bass horns for each channel, both vertically oriented, one each exhausting to the floor and the ceiling. I have an idea that spatial presentation will gain a big boost with both up and down firing bass horns.

An idea of using boundaries to get more interesting midbass is great idea. The problem I see in the actual implementation. Midbass from horn in small room can be hugely benefited if it bounces but to make the assembly of horns visually pleasant, time aligned and functional at the same time is a big question. I do like the notion of Midbass fires to the floor but did you see any attempt to do it esthetically pleasing? For sure the beauty id the eyes of beholder but I personally do not like visually any inhalation I have seen with vertically positioned midbass. Also, the vertically positioned midbass are always undersized… Anyhow, I am still looking for some kind of innovative industrial design solution that would implement vertically positioned midbass but in a pretty way and that would not make an acoustic system to look like it’s trying too hard to make sound.

skushino wrote:
Which driver to use? 12" - 15" are the obvious choices to balance low-end displacement and seamlessly match lower midrange @ 200hz

There many 15” drivers to choose but if you do for 55Hz horn then probably 12 inch driver would be preferable. The park of 12-inchers is strange. It looks like companies did not do a lot of good 12” drivers. You might look for some older Electro-Voice 12” drivers, or perhaps find something new. You need to look for high-sensitivity before a horn, at least 98-100dB and then look for everything else.

skushino wrote:
Time alignment with other channels. Need clarity on how to measure. Is it distance from driver to listener, or need to include horn path length in consideration?

Yes, the time alignment will include the horn path length, the distance from the boundaries sand so on. In case of boundary use you will be at much less critical time alignment demands and you will have a lot of diffusion of sound and your midbass will not shape an impulse too well. So, I would take the time alignment in consideration but would not go too anal retentive to it as I insist to do in case of direct radiator horns. At 55-200Hz and with indirect radiation you will have a LOT of room gain going on. You might pay a toll and have some kind of funny imaging but you might gain in many other aspects.

skushino wrote:
Hf limit

I would say 200-300Hz and do not expect that your upper region will be too great. The lower you go the best.

skushino wrote:
Imaging and soundstage considerations with horns not pointing at listener

It is very hard to estimate what will happen with imaging. If you wish you can flip you current midbass horns vertically and to see what happen. Be advised that you would need a good month to work on your playback and to modify the associated channels in order to make your playback to sound properly with flipped midbass. Will you go for that investment of time and efforts?

skushino wrote:
Driver cone sag in vertical orientation. Is this a credible concern or too much hand wringing about nothing?

Yes, the drivers sag and they sag even a driver hung in horizontal plane. How many people flip the drivers 180 digress each 2-3 years? However, the sagging is most applicable for drivers that are trying to be full range and have large excursion. In your case you will pick a high sensitivity driver that most likely will have very hard suspension and very limited excursion – this type of drivers is suited for horn loading. With very short and hard suspension I would not worry about sag.

Rgs, the Cat

Posted by skushino on 08-09-2012

Midbass from horn in small room can be hugely benefited if it bounces but to make the assembly of horns visually pleasant, time aligned and functional at the same time is a big question. I do like the notion of Midbass fires to the floor but did you see any attempt to do it esthetically pleasing?

"Visually pleasant" - Yes, this is a challenge... My original idea was orienting the horns back to back, or driver to driver, with one pointed up and the other down. Sort of an hour glass shape. But the ceiling is only 8 ft high, and the max path length in hour glass configuration is around 3 ft per horn, less than 80 hz fc, hardly worth the effort. In order to make a longer horn, the throats will need to overlap, running parallel to each other but in opposite directions. This is a mess of an industrial design and I don't have an answer yet.

"Time aligned" - see below. If the vertical bass horns are located ahead of the mains by a distance equal to the path length, I think the problem is solved. Am I understanding correctly?

"Functional" - This idea is the result of answering the question of how to fit a 4' - 5' horn in my room. The only way I know to do it is vertically. There are other benefits like coupling with boundaries, and the opportunity to have both floor and ceiling coupling. The idea of having bass extending the entire height of my room is very cool.

Yes, the time alignment will include the horn path length, the distance from the boundaries sand so on.

If I understand correctly, the bass horns need to be in front of the satellite mains by a distance equal to the length of the horn. This seems logical to me. So looking at Tuneaudio Anima, the design could be improved by separating the bass horn from the MF and HF drivers, and moving the bass horn forward around 5 ft, correct? I want to make sure I understand this point correctly.

In case of boundary use you will be at much less critical time alignment demands and you will have a lot of diffusion of sound and your midbass will not shape an impulse too well. So, I would take the time alignment in consideration but would not go too anal retentive to it as I insist to do in case of direct radiator horns. At 55-200Hz and with indirect radiation you will have a LOT of room gain going on. You might pay a toll and have some kind of funny imaging but you might gain in many other aspects.

Well this is the part that's most interesting. I expect it will take a lot of experiments to find the balance between boundary gain, imaging, and flat bass response. My lower mid horns play down to ~ 160 hz. So I could move the x-over lower than 200, in theory. Would need to validate by listening first.

It is very hard to estimate what will happen with imaging. If you wish you can flip you current midbass horns vertically and to see what happen. Be advised that you would need a good month to work on your playback and to modify the associated channels in order to make your playback to sound properly with flipped midbass. Will you go for that investment of time and efforts?

This is a great idea! But rather than flipping my midbass horns up, I will point them down, with an appropriate gap separating the mouth and floor. This would simulate down firing and floor coupling together. I would expect more gain resulting from coupling to the floor boundary, and who knows what effect on imaging. Thanks for the idea.

Posted by zztop7 on 11-03-2012

Driver cone sag in vertical orientation.
Last year I sold off my system because it was just too heavy. Almost every piece needed two or more people to move [Duntech Sovereign speakers, etc.]. I have been replacing everything with tube components and speakers that I can lift. The speakers are built by me for my personal use, and all have light paper cones that point towards the ceiling. I like the bounce sound off the cathedral ceilings [>>>OK - everybody can now "slam" me<<<]. I do not anticipate any cone sag toward the floor or ceiling. My belief is that cone sag would be a problem with cheap components in any orientations, and heavy cones add to the problem. Horizontal [line bisecting cone & voice coil] orientation with heavy cones would have a sag that would need a face lift, but current manufacturers use stiff outer edges.
Skushino, I see that you are in Seattle. I am in Bellevue, and you are welcome to see the slowly evolving speakers.
David.
P.S. I have been reading old & new posts on this site for over a year - Great Information.

Posted by skushino on 02-08-2016

This project just woke from a long slumber.

I've been granted access to tools and people to move this forward. The tools are a large-scale CNC cutting machine and paint shop, used to fabricate volumes (large 3D shapes) attached to climbing walls at indoor climbing gyms. The people are the shop owner / operators. They're excited about re-purposing their activities to create a better music playback. The volumes are large enough to climb over and around, are very strong, and are finished in a coarse, durable, sandy epoxy paint texture for friction.

Would interested readers comment with any problems or topics of interest you see in the design? We plan to begin cutting soon. I'm less interested in debating the merits / demerits of a vertical horn. I think Bruce Edgar and Tune Audio have already confirmed proof of concept.

The horn design is a two-segment conical approximation of a four ft exponential horn. I didn't see the benefit of hyperbolic for a downward horn limited to 200 - 250 Hz on top. The range is expected to be around 60 - 200 Hz.

Details:

Throat - 480 sq cm / 8.6 in square
Mouth - 6250 sq cm / 31 in square
Segment 1 length - 86 cm
Segment 2 length - 40 cm
Total horn length - 126 cm / 49.6 in
Back chamber length - 11 in
Est. back chamber volume - 31 L
Est. gap of mouth above the floor ~ 7.5" (per Edgar. Legs will be height adjustable to tune response)
Est. total height of horn ~ 162 cm / 64 in

Still unresolved:

- How to fasten the back chamber (18" diameter very heavy PVC pipe used in commercial building construction.) on to the horn throat.

- How to design a fastening system to attach the two conical segments together, but with the option to disassemble for convenience when moving.

- How thick should the horn walls be? Using 1 inch baltic birch but perhaps should double up? Nominal thickness would be 1.5"

- Stand design. Right now the plan is to separate the bass horn from the MF and HF horns.

- Bottom exhaust. Could keep it simple and fire straight down onto the floor. I think there are benefits to adding a very robust floor platform beneath the mouth, maybe with a reflector, similar to Bruce Edgar's Seismic Sub. I used to have the Seismic. It was large and ugly but the sound was surprisingly very good.

Posted by zztop7 on 02-09-2016

Hello Skushino,

Glad to see "it's alive". I am near you, but I have a different phone #. You can PM me for it.

>>> back chamber: an 18" flange / Google 18" diameter PVC flange. If you use the glue on type, make sure you use the very heavy gray glue [make sure you use the compatible primer - extremely important].

>>> conical segments fastening: I would build a hefty flange on each segment & bolt together with a felt gasket material that will compress and will be easily replaced; no stickies, no glue.

>>> I use a lot of Baltic birch. Great stuff. I believe the 1 inch is only available in 5 foot by 5 foot sheets. You could consider marine grade plywood with Lloyd's of London approval/certification. Crosscut Hardwoods might stock this. Also compare price @ Compton's.

>>> Stand design: I would have to see a close to final design of the horns.

Best to you,zz.

Posted by Romy the Cat on 02-10-2016

skushino wrote:
Bottom exhaust. Could keep it simple and fire straight down onto the floor. I think there are benefits to adding a very robust floor platform beneath the mouth, maybe with a reflector, similar to Bruce Edgar's Seismic Sub. I used to have the Seismic. It was large and ugly but the sound was surprisingly very good.

The whole idea of bottom exhaust has own beauty: minimization of foot print and elimination of direct firing toward to a listener position. Usually, bottom exhaust system, not only horn but floor standing loudspeakers (like Eidolons) and subwoofers (like REL) have what I would call “accurate” sound. I have no idea why.

The Edgar's Seismic is kind of freak of a nature of its own. It is not “really” a horn. It uses 18” driver and has for all intended person “covered” 32 by 24 mouth. It is rather a horn-pretentious waveguide system. Even more ugly: it heavily equalized and driven by Edgar's provided $100 plate SS A/B amplifier. Still, I need to admit that as many times I heard it I did like it. It has the same very “accurate” sound. It has aloe what I always was trying to get in lower bass: that feeling of softness and pliability. In a way my love to the ribbed Scan-Speak 25w/8565-00 come for that their array if driven properly gives a lavish and indulgent bass. Not the “tight bass” that all stupid audio magazines and industry retards are promoting but rather slow bass with super-domination of second harmonic. I heard this bass for a first time in 1999-2000 in Belgium. I do not already remember where it was. I was visiting a guy and he has some Czech-made made tube PP amp with Dunleavy IVA. The sound was nothing special but bass was beyond of what I expected. That was the day when I discovered the 8565-00 in the Dunleavys.

The Audio people are ignorant in majority and they do not get it that bass has to be “slow” with proper articulation of upper bass. The necessary transients of bass are set by upper bass horn not midbass horn and certainly not the ULF channel. As soon a person goes with separation of bass over 3 different channels and has a control for individual channel amplification’s loading then many industry stupid fantasies about “fast and tight bass” are evaporation…

Posted by skushino on 02-11-2016

zztop7 wrote:
Hello Skushino,

Glad to see "it's alive". I am near you, but I have a different phone #. You can PM me for it.

Best to you,zz.

Thanks for sharing your ideas, ZZ. Much appreciated.

Ironically, I'm finding that designing the details for the supporting equipment is as challenging as the horns themselves. I'm fortunate for the support I'm getting from the CNC shop. A couple guys were over last night to work on the project. Their input is surprisingly refreshing. They aren't "audio people", so they also are not constrained by audio culture. One guy is also a glass artist (Chihuly school). He visualizes objects in a manner different from me. My perspective is purely functional. He brings a strong aesthetic eye to the project. I've visualized these horns in my mind for a decade, and the ideas the new people bring are ones I never considered. Their input about designing for easier fabrication and including "art elements" is welcomed. One example - I had planned for the horns to be square or rectangular in cross section for ease of fabrication. They lobbied for a more visually interesting shape and we settled on a regular pentagonal cross section. This results in a significantly more interesting "object", that stimulates visual senses while the pentagonal shape eliminates parallel walls for better function. This shape would be extremely challenging to create using traditional construction, but it seems to be almost trivial using CAD and CNC.

I'll post a rendering when ready.

Posted by skushino on 02-11-2016

It's too long ago for me to remember the sound of your system, but not too long to remember my reaction to your playback. I remember the bass being different. The adjectives that come to mind are only words, but for the benefit of readers who may never experience a similar playback, I think "big, round, bouncy, effervescent, bubbly (visualize a glass of sparkling wine / champagne)."

Sadly the words mean nothing without the listening experience. My point is simply that this was a different type of bass, with personality rather than "slam" or other audio silliness. It was educational.

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