whats your favorite sound machine? just to get an idea....

cheers,klaus

Klaus, this thread is for Jessie's horns.  My own speakers, if that's what you're after, are mentioned in my Lamm ML2 and K&K phonostage threads.

This post will self-destruct in 24 hours.

Best regards,
Paul S

Klass wrote :

"...ribs stiffer than sandwich? Can you explain?..."

It's not what I wrote, or meant to express. For the same given thickness, a sandwich would be more stiff than a ribbed and otherwise non-sandwich construction (in fact the "ribs" I imagine would best be described as foam-filled cores, a sort of localized sandwich construction).

Depending on the number of ribs, their placement, the depth of their section, how many layers of laminate on either surface, etc, one could end up with a structure that is super stiff, and way easier to make than a full sandwich type construction of comparable stiffness.

What I like about this approach is the following:

1) It accommodates compound curvature!!!! This is a big deal... For example, the transition from round throat to rectangularish mouth is easily accommodated, as are bolt flanges. And, lest we forget, giving a form compound curvature is in itself one of the very best means to impart structural integrity to that form (This is one reason why chickens do not lay six-sided eggs)

2) It uses techniques I already know (ah, brainless progress!) : I.E. A big plaster core on the floor of my kitchen, onto which can be laid a thick laminanate, followed by deep ribbing.

3) It concentrates most of the material on the inner wall, which means an inner wall having more density, more mass, higher acoustic impedance, which in turn means (provided the whole of the horn doesn't start resonating!), cleaner sound coming out of the horn. If one could create a sandwich having compound curvature and a dense inner wall, it would be superior in terms of overall rigidity and in resistance to resonating as a whole structure. But when I say sandwich, I mean a sandwich having a thickness appropriate for the scale of the horn... So not a 6mm piece of foam between a few layers of fiber and resin... For a 45 Hz exponential horn (nearly 3m in length with driver) I would go with a minimum of like 75mm thick walls.

4) Purely practical... No need to transport, manipulate and store large sheets of plywood and foam (remember, I am doing this in a Paris "apartment").

5) In my case, it would probably end up being faster if adopting this process, and would result in better quality of the finished parts

Here's the stuff I would use to make the ribs (it will conform to a curve if desired... Section depth up to 200mm or 8", more depth via special order)... Scroll down a bit : http://www.compositesolutions.ch/pdf/tds/omegaf.pdf

The drawback is that the materials cost would likely triple. More layers of fiber + More liters of resin... I was shocked at the prices for Epoxy resin over here, but along with superior mechanical properties, this stuff would go unnoticed by my neighbors; it's more or less odorless. (This not being the Wild West, one cannot just kick off a few gallons of polyester resin in one's kitchen).

jd*

Tuga wrote :
"...Could you provide the contact for the Carbon suppliers you have found?..."

Tuga, sure.

Email me; click on my pseudonym (user I.D.); Let me know where you will be wanting to use the materials (what continent?), as shipping adds a lot.

jd*

jessie.dazzle wrote:

The thraot size will be 7 inches.

Wow, THAT IS BOLD!!!! The 45Hz how from 7” throat – that is very-very cool and very positively-obnoxious.

jessie.dazzle wrote:

Yes I have thought about paying someone else to do the work, but that sort of skilled labor is super expensive around here.

Jessie, I just interested what money are we talking about? A few months back when in the GOTO thread:

http://www.goodsoundclub.com/LatestPosts.aspx?ThreadID=5901

Jeffrey Jackson suggested that to build the horn similar that he has built for the GOTO distributer he would charge around $15K. As I understand you are a software engineer, so with $100/per billable hour of your salary the $15K is just a little bit more than a month of work. Do you think it worth to consider? Also, you are in Europe and get paid in Euros and you can always found a builder  to who you will hay lea - in countries with their economic:  China, Russia, India, USA, Mozambique, Mexica, Taiwan etc…

jessie.dazzle wrote:

And... Yesterday I had a sort of "big day" with regard to defining the process. I'm still working it out, but it may not involve breathing chemicals, and could be quite simple.

Hm, will it include a wishing well; the seven lit cane and a necessity to sacrifice a chicken?  Well, perhaps I know little about the building technologies but within my clouded views the 7-throat to 45Hz will be pain no matter what you do…

jessie.dazzle wrote:

On another subject : I'm considering having all drivers remagnetized via a local guy who used to deal with Vitavox (and other) drivers.

Do not forget to make the measurements of the flux before and after. That would allow you in future to monitor your driver’s charge.

jessie.dazzle wrote:

The only difference I can see between the K15/40 and the AK151 lies in the resistance of the coil; the K15/40 being wound for 15 Ohms R, and the AK151 for 7 Ohms R. (In fact, the cone replacement kit one installed would allow him to change between the two drivers). According to the spec sheet, the K15/40 was intended to be used as a direct radiator. The AK151 was intended to be horn-loaded. Vitavox's resoning here must have bene that once loaded into a horn, the impedance in the case of the AK151 would come up. (Impedance at 400Hz for the K15/40 is 15 Ohms. Impedance at 400Hz for the AK151 is "determined by the charastics of the associated horn")

I never thought that impedance maters. I was thinking about impedance when I used off the shelf amps but when I went for my own amps and was able to moderate the plate load myself then I became much more flexible with impedance requirement. Anyhow, I did not play a lot with differences between the AK151 and K15/40. When I decided to stop with Vitavox bass drivers I confirmed foe myself that they were better then 515G and it was the further I ever went as I did not have a proper horn. However, in my mind I was thinking about 9-10” throat. You went for 7” – it is much nobler but it I still the 15” driver…  You will have too large front chamber. It will give you more gain but no one knows what else it does with sound. Generally for 7” hole I would like to see 10” driver… but I do not know any 10 incher of good sound. The LF section of Tannoy Red or Silver would do but they have 100dB less sensitivity then necessary…. I would look more or perhaps try to use the Vitavox 15” and to see what happen… Thankfully you will have so much aggravations with your horn that the driver size will be the least of them… :-)

jessie.dazzle wrote:

I do my best to remain ignorant of the price for which I sell off the hours of my life. (Btw, I'm not a software engineer; I design cars). Yes I could pay someone to do the work, but I'd rather put the cash toward the purchase of a good room. There's more to it... It will sound backwards, but the truth is that I am just too lazy to have anyone else do it.

Well, I have to admit that there a sinister subtext in what I say. Should you outsource the constriction of midbass-horns for a third part I might consider to go for my own midbass-horns. I do not have space to use them and I do not have any particular strong itch for pursue them but I too much like what you are trying to do and I would make them and store them for now. Who, know, perhaps building 4 horns would be cheaper then 4 horn…

jessie.dazzle wrote:

65% is also the ratio of throat to cone (minus the suspension) in the case of the Fane driver when installed in the 115 Hz horn (4-inch throat); this horn works well.

Well, there are no evidences (or any data) that if the Fane were loaded into 3” throat and the horn were slightly longer then the result was better or worse. I am not saying the it would be I just said the I do not know. We use the MF horn principles as the neat reference for throat/mouth ration but no one says the LF horn work at the same best ration as HF horns. In the end they might just the arbitrarily numbers that we just convince ourselves that they are correct.

Regarding the rest. Your midbass horn looks perfect for me, in fact it is exactly that I would like to have myself when I ripe for it. However, I do not agree with the way how you intend to use it. First: you shell not put a LF source between the MF channels – very bad for imaging. Second, I have an alternative idea for you. This is what I will be trying to do if I will be trying...

Thanks for the thoughts,

I was just on the phone with a guy who sells prototyping materials; we discussed the idea I had this weekend... His opinion is that it should work. If so, it will really make the process much quicker.

Romy wrote :
"...Well, I have to admit that there a sinister subtext in what I say. Should you outsource the construction of midbass-horns for a third part I might consider to go for my own midbass-horns..."

I will keep this in mind; it would very much be to my benefit.

"...You shall not put a LF source between the MF channels – very bad for imaging..."

Yes I thought you might say that.

The lower-bass enclosures started off located on the outiside, just as in your illustration. The CAD image was done while conducting an experiment : I wanted to try putting the existing horns closer to the side walls for better coupling.

Result : Yes I got better coupling (of the bass horn particualrly), but the bass got muddy and worst of all, all intimacy was gone. Another thing I noticed : Anything even slightly dynamically compressed was just unlistenable.

It took me a couple days to realize what was going on... This was not the only change I made; on top of that, I was not getting enough sleep to trust my ears. In fact I had to pull the frames away from the side walls before understanding the extent of the damage. That's what I was doing last night. I still have to move the lower-bass enclosures back to the outside.

Btw, I have also moved the 180Hz horn back up, leaving more space for the tweeter.

Regarding the set up you illustrate above... This may be possible (I need to measure); it would require that I modify the house a bit.

jd*

jessie.dazzle wrote:

"...Horn installations are ugly from female perspective..." Yes, and this type of woman is, from my perspective, as interesting as your average cabbage....

 …and here are the horns that this beauty with whiskers does: