GoodSoundClub - Romy the Cat's Audio Site

Horn-Loaded Speakers
Topic: Pulp fiction

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Posted by Gargoyle on 12-27-2015

What are some of the limitations to using such a light-weight composition? (frequency, resonance etc.)

I must admit the construction technique is appealing albeit somewhat slow. It lends itself to experimentation.

Perhaps rather then using traditional paper mache techniques, one could mix up a big bucket of pulp and apply it to a mold with a stucco gun.
Maybe even use a vacuum bag to compress it against the mold. With this technique maybe it would be possible to construct a pulp horn with 1/8"- 1/4" walls?

Posted by Romy the Cat on 12-28-2015

Gargoyle, I do not know the answer. I have two friends who make paper MF horns and they claim that they are fine. I did not heard their system but even if I did then there a very high change that I would not be able to say anything defiantly. To say something defiantly would require to make the same horns from wood and paper for the same driver and to listen them. I am absolutely sure that somewhere in the frequency slow would be a threshold where the mass and density of paper horn would be a factor that adversely impact sound. Where that frequency region would be I have very hard time to say. Juts out of my ass I would say that it might be 400Hz but it very much might be an octave or two lower or higher. It would depends from very many factor including the total mass of the paper horn and amount and type of damping one put on the external side. Frankly to make wooden MF horn is not so hard and not expensive to buy. The upper bass horn more costly but I would not go with them paper made.

Posted by Paul S on 12-28-2015

Gargoyle, I have not made paper horns to amplify bass, but only to use as "wave guides", to +/- "shape" the sound. My results so far agree with Romy's theory, that the paper horns begin to eat energy when I used them "too low". In this case I used 4-600 Hz with 6 dB roll-off. Of course, when the "wave guide" is also a baffle one must also allow for baffle step roll-off, and the amplifier-type horns would have to contain and direct a lot more energy. I think the paper is easier to work with than wood, especially compared to turned horns, and one might also use paper "mud" to modify wooden horn profiles. I hope you will share your results if you try this.

Best regards,
Paul S

Posted by Gargoyle on 12-28-2015

Paul S wrote:
My results so far agree with Romy's theory, that the paper horns begin to eat energy when I used them "too low". In this case I used 4-600 Hz with 6 dB roll-off.

Thanks, this gives me somewhere to start.
I am considering adding some additives to the pulp, like sand for added mass, or rubber particles to diminish ringing. If possible.

I had even contemplated thick rubber sheets (overlapping pedals) for a bass horn, but I think I will leave that for a different discussion.

Paul S wrote:

I hope you will share your results if you try this.

Best regards,
Paul S

Sure.

I think I can start by making some square sample sheets of material while I'm planing the form. I will probably try Inlow's jig to make the form mold. It uses a drywall compound, at first I thought there may be better materials, but upon further reflection it seems a good candidate.

Most likely I will use wood glue instead of flour for the binder as an attempt to mitigate some of the drying time. I don't know how this will affect tone, but I will predict that they may sound a little different. The glue will probably result in a stiffer horn then one made with flour.

Also wooden rings or ribs could be added strategically to the exterior if need be, or perhaps spiral-wind some hemp string during construction.

I don't expect miracles, I think anything that is moderately dense is going to have some issues with resonances, short of making a "soft horn".
I also share your enthusiasm for the technique compared to working with solid wood. Mind you I will still have to get creative when it comes time to make the big horn with no lathe.

Posted by Paul S on 12-28-2015

You might also want to try stiffened felt, which seemed to work "as well" as the paper for me, and it is easier to form. Just saturate the pre-shaped felt with runny "paste", whether gluten/starch or methyl cellulose, milk glue, etc. Spray starch "works", but it's expensive. I also used chicken wire or wood ribs, some stitched to the fabric; anyway, the forms need not be solid. If you think it through ahead of time you can attach the felt to pre-fabricated mounting plates or blocks as you incorporate the fixative. If you have not yet checked out the Jessie Dazzle Project on this forum, do that, too.

Best regards,
Paul S

Posted by Gargoyle on 12-30-2015

Paul S wrote:
You might also want to try stiffened felt, which seemed to work "as well" as the paper for me, and it is easier to form. Just saturate the pre-shaped felt with runny "paste", whether gluten/starch or methyl cellulose, milk glue, etc. Spray starch "works", but it's expensive. I also used chicken wire or wood ribs, some stitched to the fabric; anyway, the forms need not be solid. If you think it through ahead of time you can attach the felt to pre-fabricated mounting plates or blocks as you incorporate the fixative. If you have not yet checked out the Jessie Dazzle Project on this forum, do that, too.

Best regards,
Paul S

Thanks for the input. I have perused some of Dazzle's but will have to revisit that topic specifically.

I do not yet have a vacuum pump, researching that at the moment, but in the meantime I though if I wanted to make some little samples of material I was thinking I could weight them down to the tune of ~14.7 psi by using 5 gallons of water on a ~3" squared sample.
It might not be quite the same thing as a vacuum, but its a start.
Ideally I would make long strips of sample material so I can compare how it resonates on the edge of a table, similar to flapping a ruler in school.

Hey Paul S while I have your attention, feel free to recommend a configuration to use for testing. Perhaps something similar to the 200Hz exponential in the video I posted in the thread about surface textures? For now I just wanted to focus on materials and construction, any contributions with regard to horn theory would lighten my work load. https://www.youtube.com/watch?v=ecVXEFb0mXY

Ultimately it would be nice if the setup could be used in my future horn build, but I realize that my build should orbit around the lower frequency horn.

So that being said, we just need something somewhat decent for experimenting purposes, using something available and cheap like the Faital 5" in the video would be suited for these tests?

Posted by Paul S on 12-31-2015

Gargoyle, YMMV, but I associate LF propagation/amplification with mass; there has to be some way to really "anchor" at least the LF driver. I was thinking MF for the felt and/or paper horns, although I guess you could begin with a chicken wire form and build it up, ending with something heavy, like plaster. Again, Jesse covered the plaster very well. As for surface treatments, this is yet another case where the site is rife with ideas on the subject. My limited experience with horns is that everything "makes a difference", to the point where you could go nuts. I suggest getting the basic materials and shapes down first, then messing with surface treatments after that. There's already plenty of info here on drivers, which also vary considerably piece-to-piece as well as according to how they are "developed". My own thoughts have been to not ask much from the horns, but to try to use fast rates and some paper drivers. Still, I can't deny that the Cogent lower MF was among the best I ever heard, at least for one octave, ~ 4-800 Hz, and the Avantgarde Duo Mezzo seemed good enough at THE Show to make me wonder why people insist on fighting with all this. I would also favor "exponential" horns down to 200 Hz; but at LF you enter the World of Mystery, where you will need a Spirit Guide. Lastly, I would love it if there were some way to re-use all the "mules" and "stacks" I have built for testing. In fact, I'd settle for perfect recollection of the experiments and the results I got at the time!

Best regards,
Paul S

Posted by Gargoyle on 01-02-2016

"Gargoyle, YMMV, but I associate LF propagation/amplification with mass; there has to be some way to really "anchor" at least the LF driver. "

Noted

"I was thinking MF for the felt and/or paper horns, although I guess you could begin with a chicken wire form and build it up, ending with something heavy, like plaster. "

If I thought I could do a decent job bending up a wire horn, I may attempt it.

"Again, Jesse covered the plaster very well. As for surface treatments, this is yet another case where the site is rife with ideas on the subject"

I have been finding more information by using google to search the site. Forgive me if I haven't caught up on 100% of it yet. Things like this need the right balance of experimentation, research and inspiration.

I suppose in this thread I should just focus on the structural aspect of the horn but invariably at some point the surface finish will intertwine with the subject.

"My own thoughts have been to not ask much from the horns, but to try to use fast rates and some paper drivers."

I could see that.

" Still, I can't deny that the Cogent lower MF was among the best I ever heard, at least for one octave, ~ 4-800 Hz, and the Avantgarde Duo Mezzo seemed good enough at THE Show to make me wonder why people insist on fighting with all this. "

Interesting.

"I would also favor "exponential" horns down to 200 Hz"

Exponential it is then.

"but at LF you enter the World of Mystery, where you will need a Spirit Guide."

From that video it looks like the typical undersized bass (or any undersized) horn could benefit from having an infinite baffle to keep it from going dipole.

"Lastly, I would love it if there were some way to re-use all the "mules" and "stacks" I have built for testing. In fact, I'd settle for perfect recollection of the experiments and the results I got at the time! "

So these are like a bunch of sliced up horn sections you have for molding?

Cheers.

Posted by Paul S on 01-03-2016

Gargoyle, I don't know how much experience you already have with this stuff. I want to be clear that I have not played seriously with LF boosting horns since about 1973, and even at that time I was pretty much stuck on copying existing horns, including cellular horns, and re-building old theater systems, mainly because results from "random" experiments were all over the map. It seems likely that the closest thing you will get to "help" with this is to start where someone else left off, and this is why Romy has so many followers, because he has clearly documented and made freely available comprehensive plans for a successful installation. Again, I don't know how far along you are at this point, but I can promise you that if you simply dive in and start mixing and matching horns and drivers, then it will be a very long road, and depending on your living arrangements you may never get good results. Especially with the larger, turned horns, who can afford many mistakes? On the other hand, you might turn out to be someone who will be happy once a substantial effort is made, as long as the sound is big, etc. If anyone asks me these days, I usually "recommend" to piece together and play with an "acceptable" stock system for a few years, and to use that as a starting point. If someone has "already done that", then they "should" have a pretty good idea where they are at now, also what they want to change, specifically, also some ideas about how to make that happen. For me, the old Lamm ML-2 amplifiers were an amazing "short cut", so I still recommend these to anyone who wants to learn about what's possible with hi-fi. As for a big horn speaker system, this subject is very complex, and there are many posts on this site that may speak to you far better than I can. Certainly, I cannot point to my own successful horn installation, nor do any of my old leftovers relate to classic horn systems, such as Romy's.

Best regards,
Paul S

Posted by Romy the Cat on 01-04-2016

Gargoyle,

I am going to tell you something that is very important and that you hardly ever heard in audio. The guys who are trying to do something in higher-end audio always attribute a lot of attention and energy to tooling. For sure tools are important in audio, but to a degree. There is much more important then tools – the applications of the tool in order to get a desirable result. The application easy override the inferiority of tool or able to compromise the best tools available out there. The improper application of even the very good methods/tools is exactly where 99% of audio folks slip. It is not even applications themselves but the discrimination of causality – the region where most of audio people are clueless. Pretend you build your audio paper horn and get some kind of result. Then you did the same horn from wood. Then you mass loaded your paper horn with some kind of heavy wax, like Goto does. Pretend you load the very same driver in all of them and get 3 distinctly diligent results. You might think that you get the causality? Hm…. Not so simple. I can give you reasoning why sound still might be different and it would not have anything to do with material of the horn. So, what I always say and what audio people do not understand is following: pick you topology and perfect it internally. Efforts spent on PROPER perfection of your topology or tooling (presuming that they are potent) will way overweight and expansion in new tooling. Also, always use the main rule of my site:

http://www.goodsoundclub.com/Forums/ShowPost.aspx?PostID=432

Rgs, Romy the Cat

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