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:

Now that is what I call a woman.

Nice; I can smell the metal.

Dominique, let's have a beer sometime.


jd*

Im in the process of building a pair of 115hz MDF horns.  Any suggestions, on the size and type of vent for the the back chamber? Ive seen Jessie's implementation but I am pretty sure I will not be able to do that in my situation.  I assume a simple hole sealed with silicone would not suffice given the amount of pressure build up in the rear chamber? Thanks in advance!

Jp,

what do you mean by “vent for the back chamber”. Why are you planning to make the back chamber vented?  The side would be depending from the type of your driver, but generally it will be always smaller then you think.

The Jessie's implementation is unquestionably wonderful if it is easy for a person to do but I with all sincerity ask if it necessary to go into this extend. The back chamber setting is one time deal (per a driver) and there are many other ways, way less demanding but identically effective, to set the back chamber’s size.

jp wrote:

I assume a simple hole sealed with silicone would not suffice given the amount of pressure build up in the rear chamber?

The pressure that builds up in right rear chamber is truly enormous.

jessie.dazzle wrote:

… adjusting chamber volume will not be as convenient as turning a threaded shaft, but once the correct volume is found, you're done.

Even when we are talking in context of one non-changeable driver it opens up a ground for a great discussion: what happen when the resonance of chambered driver and mouth rate “almost” match? We have a few variables: the type of the driver and the location of the horn in the room. It is easy to measure where the Fs of chambered driver sits in relation to the horn’s rate. However no one ever told about what happen with Sound when the Fs ascend for ½ hertz. It might be that the precision in it is not important at all but it also might be that a very precise dialing of Fs creates some interesting sonic benefit. How, that “precise dialing” might be changed by driver or by position of the horn relative the back wall only God knows.

Sure, the “smart” people use the HornResp… :-)

jd wrote :

"...I may have come up with a way of making the BIG horns fairly painlessly..."

Yes well, I really must give up the absinthe !

Lbjefferies7 wrote :

"...Not "end-of-life"in the sense that it will be built and then I'll never have to mess around with speakers again, but more in the sense that it's a project that will likely kill\cripple me..."

Been a bit slow on posting progress reports lately because I've had to delay construction of the second mid-bass horn. This was due to having herniated a disk in my back while moving the first mid-bass horn out of the way.

Here it is (throat = 8", cutoff = 40Hz)... Just test-listening here ; no filter, no rear chamber, driver not securely fixed but just placed on a box... Original plan was to listen for a few minutes, then get it out of the way and start on the second horn... I ended up leaving it in place for about a week, eventually adding an approximate filter :





Photos were taken about 3 months ago... Horn is laying on its side; shold be rotated 90° with short side on floor.

Still lots of finish work to do... Finish work will commence once second horn is to this same rough state.
I am now back to work on the second horn, which is about 1/4 of the way done. It is extremely boring and repetitious work.

Lbjefferies7 wrote :

"...My system certainly follows the 'form follows function' rule but I have wondered how the looks of a speaker (or entire system) effects the listener's perception.  Of course we have all experienced some male grunting and hooting over the shinny things and glowing tubes.  This only led me to believe that the appearance of a system can theoretically produce a more sophisticated and music-friendly perception.  How to accomplish this while keeping axioms intact is a daunting challenge..."

I chose to give priority to the axioms... In the case of these mid-bass horns, my intention is to leave the deeply ribbed exteriors out in the open, letting them work as diffusers for the mid and high frequency channels (their primary function being of course structural). These horns will eventually get a coat of semi-flat black paint inside and out. I may one day (if forced by a woman) have to build a sort of case around the outside of each one, or build them into a house.

jd*

To answer Romy's questions :

Drivers :  

Vitavox AK151

Resonant frequency  :

I did not try to measure it. Can anyone confirm the following : I assume this parameter is most easily determined by playing a series of tones at constant signal strength (volume setting) while measuring the SPL; the frequency of a tone that gives the highest SPL is the resonant frequency of the assembly. Is this correct?

Filters : 

Initially I ran the horn full range, without the other horns. I was immediately sort of horrified at how high (in frequency) it would play. I then stuck a 5mH coil in front of it, so as to low pass somewhere around 200Hz (really could have used a 3.5mH coil, but didn't have one on hand). Next I made a band pass filter to give a theoretical operating range between 90 and 185 (normally I'd let it go higher, to around 250Hz but again, I didn't have exactly the right stuff sitting on the shelf... Used a 150µF cap followed by a 10mH coil; driver measures around 6 Ohms). In case its not clear, the filter is first order. So now with things reined in a bit, I sat down to listen, both with and without the other horns. 

Sound : 

First, I may be totally off here, as I was extrapolating potential from a situation where the horn was about 15 ft out in front of the other horns, so any evaluation in the context of the rest of the system is to be taken lightly. Given that disclaimer, I will say that I was satisfied in a very basic way. This may seem obvious; I sought first to confirm the presence of real mid-bass as compared to what happens when filling in for the absence of this horn as I had been doing, by running the other channels beyond their ideal range (running the 115Hz horns down lower than they should go, while running the lower bass enclosures up higher than they should go... For this session, I did go to the trouble of changing the filters on those channels, moving their operating ranges out of mid-bass territory). Well so do I now have real mid-bass? At this point I can only say that this bass differs in that it is not as constrained sounding, but more weightless and relaxed... Somewhat a contrast to the way the horn looks. Next I would say that despite being way out in front, in the context of the rest of the system, the sound of the additional channel did not call attention to itself; my neighbor however, listening from his apartment, did ask if I hadn't changed something... To me, the system did not seem any louder. Removing the horn from the system (to make space for creation of the second one) turned out to be difficult, and not just because of its mass; given the horn's position, I know how silly this will seem, but momentarily disconnecting the channel had already confirmed that its contribution would be missed; the result was that it stayed there for about a week. I will post more observations once I get the pair of them up and running.

Weight :

One horn without driver, rear chamber or supporting chassis and wheels weighs around 900 lbs. Heavy yes, but not excessive; with music playing at live listening levels, one's hand is enough to detect whether or not the horn is working. The assembly comes apart in quarters split along the horn's firing axis (see clamped flanges in photos above). A single multi-layer lamination (about 1" thick) over the forming tool or buck yields one pair of mirrored quarters, or half a horn. I will post photos of the construction process some time in the future. 

Hang on a minute... I see what may be a sign of progress in the ability to upload images to the cat's server via a Mac navigator... I'll now attempt to post an image of the forming tool (do not hold your breath) :

Well I'll be damned ! Meow !

Above is the forming buck, soon to receive a coat of shelack, followed by several coats of wax.

jd*

Whoa... An "Edit" button! Nice work Romy !

Ok, its a bit screwy (done several edits trying to get the font and colors right and the thing seems to have a mind of its own) but this is real progress.

jessie.dazzle wrote:

Resonant frequency  : I did not try to measure it. Can anyone confirm the following : I assume this parameter is most easily determined by playing a series of tones at constant signal strength (volume setting) while measuring the SPL; the frequency of a tone that gives the highest SPL is the resonant frequency of the assembly. Is this correct?

Well, it is a bit incorrect way to determine resonant frequency as it will be “colored” but other factors.  The easiest way to get the resonant frequency very accurate and very prices of connect resistor of a few Ohm   in series to a mounted driver and to drive the driver with generator, sliding frequency up and down, measuring the highest voltage rise on the resistor. It will be very prices as the peak will be very sharp. Now, it is simple to move resonant frequency up and down but to associate the moving consequences with subjective sonic results is way more complicated as it will greatly depending from the positioning of you horn, filters and many other things.

jessie.dazzle wrote:

Filters :  Initially I ran the horn full range, without the other horns. I was immediately sort of horrified at how high (in frequency) it would play. I then stuck a 5mH coil in front of it, so as to low pass somewhere around 200Hz (really could have used a 3.5mH coil, but didn't have one on hand). Next I made a band pass filter to give a theoretical operating range between 90 and 185 (normally I'd let it go higher, to around 250Hz but again, I didn't have exactly the right stuff sitting on the shelf... Used a 150µF cap followed by a 10mH coil; driver measures around 6 Ohms). In case its not clear, the filter is first order. So now with things reined in a bit, I sat down to listen, both with and without the other horns.

I think you will eventually end up with second order filter, consider the rest of your system. BTW, for this particular midbass channel if you stay with speaker-lever filter you might have inner-debate what to chose – the use of lowest possible series DCR or use air-core coil. Both are great but they are mutually excessive.  I went both ways: had high inductance air-core coils with 8ga wire and have some metal-core low DCR coils. My vote goes for lowest DCR and huge air-core coils with ultra high sensitively spacers is in a way a recipe for various problems.  In my time, when I was experimenting with speaker level filters (before the DSETs), I paid a LOT of money for custom-made low DCR C-Core toroidal Inductors. Nowadays they are available and none expensive:

http://www.parts-express.com/14-gauge-c-core-toroidal-inductors.cfm

jessie.dazzle wrote:

Sound :  First, I may be totally off here, as I was extrapolating potential from a situation where the horn was about 15 ft out in front of the other horns, so any evaluation in the context of the rest of the system is to be taken lightly. Given that disclaimer, I will say that I was satisfied in a very basic way. This may seem obvious; I sought first to confirm the presence of real mid-bass as compared to what happens when filling in for the absence of this horn as I had been doing, by running the other channels beyond their ideal range (running the 115Hz horns down lower than they should go, while running the lower bass enclosures up higher than they should go... For this session, I did go to the trouble of changing the filters on those channels, moving their operating ranges out of mid-bass territory). Well so do I now have real mid-bass? At this point I can only say that this bass differs in that it is not as constrained sounding, but more weightless and relaxed... Somewhat a contrast to the way the horn looks. Next I would say that despite being way out in front, in the context of the rest of the system, the sound of the additional channel did not call attention to itself; my neighbor however, listening from his apartment, did ask if I hadn't changed something... To me, the system did not seem any louder. Removing the horn from the system (to make space for creation of the second one) turned out to be difficult, and not just because of its mass; given the horn's position, I know how silly this will seem, but momentarily disconnecting the channel had already confirmed that its contribution would be missed; the result was that it stayed there for about a week. I will post more observations once I get the pair of them up and running.

You might want to get yours a test crossover to found a good configuration between midbass upper knee and upperbass lower knee. I might be complicated each time take the turns from coils or to solder caps. You might rent in your local pro shop for a weekend some kind of digital crossover or but it for 100 used.  You will not get good sound from it but you will have a good modeling tool. With some experience you will be able to prototype the results. It might be a bit tricky as low-path at line level and low-path at speaker level always sound and act slightly different, so it needed some time to learn and use to the difference. Still, the test crossover is a good tool to see if you move to the right direction…

jessie.dazzle wrote:

Weight : One horn without driver, rear chamber or supporting chassis and wheels weighs around 900 lbs. Heavy yes, but not excessive; with music playing at live listening levels, one's hand is enough to detect whether or not the horn is working. The assembly comes apart in quarters split along the horn's firing axis (see clamped flanges in photos above). A single multi-layer lamination (about 1" thick) over the forming tool or buck yields one pair of mirrored quarters, or half a horn. I will post photos of the construction process some time in the future.