aceinc - there's nothing at all wrong with it other than it's freakin HUGE. (In other words the driver is cheap, but the box will require a couple hundred dollars worth of materials - and it won't be light.) Not sure how you would incorporate something that size into the decor, unless the room has an audio decoration theme.
kstrain, MaVo and JLH, thanks for your most recent input to my questions.
MaVo: Should it not be the other way around, the mouth being 1/2 size of the Sd, not two times, which would give a compression ratio of 2:1?
JLH: No, don't worry. I did never intend to go by fixed numbers. All I ever wanted was to get some guidelines for picking out the most promising drivers of all the hundreds out there. I have now done my selection that will be modelled. I have "only" 8 or 9 drivers on my list after having done my own filtering after all given advice and info.
JLH: I forgot to ask, your Tractrix horn, is it built by the method where you make rings of different sizes of wood that you then glue together to shape the horn? If not, how did you make them?
MaVo: Should it not be the other way around, the mouth being 1/2 size of the Sd, not two times, which would give a compression ratio of 2:1?
JLH: No, don't worry. I did never intend to go by fixed numbers. All I ever wanted was to get some guidelines for picking out the most promising drivers of all the hundreds out there. I have now done my selection that will be modelled. I have "only" 8 or 9 drivers on my list after having done my own filtering after all given advice and info.
JLH: I forgot to ask, your Tractrix horn, is it built by the method where you make rings of different sizes of wood that you then glue together to shape the horn? If not, how did you make them?
MaVo: Beyma, 3 v. 4 sections
Hi MaVo: as to Posts #1811/1812/1813
On second thought: the linear change applies to the radii, so you get r_mid=r_S2 + (r_S3 - r_S2)/2. This results in a new S3 of 510.2cm^2, and then the conversion from 3 to 4 sections works just fine. Haste makes waste.....
I noticed, that you are using a compression ratio of 550/105, according to Cowan that is on the high side. Also, I could not find a Beyma 12ND1000 to verify the parameters, do you have a link?
Hi MaVo: as to Posts #1811/1812/1813
On second thought: the linear change applies to the radii, so you get r_mid=r_S2 + (r_S3 - r_S2)/2. This results in a new S3 of 510.2cm^2, and then the conversion from 3 to 4 sections works just fine. Haste makes waste.....
I noticed, that you are using a compression ratio of 550/105, according to Cowan that is on the high side. Also, I could not find a Beyma 12ND1000 to verify the parameters, do you have a link?
buggsson said:
Yes, I made them in layers. See construction pictures below. I had to rig up a pully reduction system for my lathe to handle the weight. Yes, that is 1 & 3/4" pillow bearing rated for 5000 lbs. Bigger is better in horn building.
I wrote an Excel spreadsheet to calculate the tractrix curve. I then plotted it out and sectioned it out to determine the size of each layer.
Next, I transferred the inner and outer radius of each layer onto a piece of plastic. I drilled a center axis point on the plastic and used it as a compass. I also setup alignment holes so every piece would be straight on assembly.
The biggest time saver is to set the saw angle to that of each layer. This saves a ton of time on the lathe. I transferred the angle of each piece to a block of wood.
With careful planning, there is very little waste. There were several pieces that could be cut from the leftover center pieces of the larger layers.
Drilling a precise alignment hole. The layers above and below have the same location as this one.
A simple nail in the alignment holes is all it takes during glue up. Each layer gets glue and 6 screws. The screws are used more as clamps than fastening devices. With the screws holding the previous layer, I don’t have to wait for it to dry, I just keep on building up the horn in one setting.
This is what it looks like in the rough. This looks like it is all glued up, but its not. It is actually in two pieces. I turn each half on my lathe.
A close up of the pulley reduction system for my lathe.
Here is the mouth section mounted on the lathe. The lathe stock head has a separate base than the lathe bed.
This is what the two sections look like after they come off the lathe.
Precision alignment dowels strengthen the center joint of the horn. Total horn weight without the woofer is 180 Lbs.
Here are the two halves glued together.
A closer look at the woofer chamber. Air volume is adjusted to just below the horn’s cutoff to extend the low end as far as possible.
The horn in primer before the final color is applied. And the finished product you guys have already seen in my previous post about a page or two back.
Okay, now that I have shown you guys how to make round horns I expect you to run out and buy a lathe and supplies. I want to see you completed projects first thing next Monday morning.
Tom Danley's Tapped Horn Patent
Hi JLH,
Just out of interest, do you know what aspect of tapped horn technology Tom Danley has a patent for? I must confess that I am a bit surprised that a patent would be granted - the basic principles of tapped horns have been known and well understood for at least fifty years, to my knowledge.
I guess my real question is - what is it about Tom's tapped horns that make them so unique, thereby justifying the granting of an exclusive patent?
Surely there would be no problem in people building and selling "William Cowan type" tapped horns, if they so desire?
For the record, I have absolutely no intention of building and selling tapped horns myself.
Thanks in anticipation for any further information.
Kind regards,
David
JLH said:
Hi JLH,
Just out of interest, do you know what aspect of tapped horn technology Tom Danley has a patent for? I must confess that I am a bit surprised that a patent would be granted - the basic principles of tapped horns have been known and well understood for at least fifty years, to my knowledge.
I guess my real question is - what is it about Tom's tapped horns that make them so unique, thereby justifying the granting of an exclusive patent?
Surely there would be no problem in people building and selling "William Cowan type" tapped horns, if they so desire?
For the record, I have absolutely no intention of building and selling tapped horns myself
.Thanks in anticipation for any further information.
Kind regards,
David
just a guy said:
Hi Just A Guy!
Interesting? Sure, audio always is
. Surprising? Not that much. The models used _should_ give similar result given the _same_ set of physical parameters. On the other hand, If models were showing totally different predictions, _then_ it would have been a cause for concern. After all, Mother nature doesn't care if we call it a tapped horn, quarter wave resonator, transmissionline speaker, transflex, big-bada-boom box or whatever. I dont either as long as the derived model(s) I use is capable of makeing useful predictions.
JLH:
Impressive build!
Cheers!
Re: MaVo: Beyma, 3 v. 4 sections
MaVo,
after reading the above, by tb46, I looked at the force on the cone (in AkAbak) in an approximation to your TH (the higher frequency one). Even though the compression ratio is on the high side, the peaks in the force graph were not much more than for my PD1550 TH with compression ratio 3 (for same excursion, or roughly same output - mine is smaller volume and so not quite as efficient, even with the larger driver).
I've driven the PD1550 at up to nearly 10V rms (for the excursion test), with short bursts of perhaps 20V (with scary rattles around the room at some frequencies) and would not worry at doing the same with your P1000 - I think it is at least equally robust.
Perhaps avoid driving it "full-blast" until the surround has "loosened up" a bit, so resist the temptation to do large signal tests right away... (I get the feeling that the pro-driver surrounds typically move only just enough to allow peak displacement, though I've only played with a few).
It seems that you have little option if you want a flat response with the P1000. (I vaguely remember the LX60 looking better in early modelling, when I tried almost every European pro driver, but did not keep all the models to check that.)
Ken
tb46 said:
MaVo,
after reading the above, by tb46, I looked at the force on the cone (in AkAbak) in an approximation to your TH (the higher frequency one). Even though the compression ratio is on the high side, the peaks in the force graph were not much more than for my PD1550 TH with compression ratio 3 (for same excursion, or roughly same output - mine is smaller volume and so not quite as efficient, even with the larger driver).
I've driven the PD1550 at up to nearly 10V rms (for the excursion test), with short bursts of perhaps 20V (with scary rattles around the room at some frequencies) and would not worry at doing the same with your P1000 - I think it is at least equally robust.
Perhaps avoid driving it "full-blast" until the surround has "loosened up" a bit, so resist the temptation to do large signal tests right away... (I get the feeling that the pro-driver surrounds typically move only just enough to allow peak displacement, though I've only played with a few).
It seems that you have little option if you want a flat response with the P1000. (I vaguely remember the LX60 looking better in early modelling, when I tried almost every European pro driver, but did not keep all the models to check that.)
Ken
Hi kstrain, thanks for the hint. I compared my horn to what i belief to be a close approximation of the TH115 and the force peaks are about the same. Since i have the drivers, i want to get the most out of them. I never bought them with a TH in mind, so i think i am lucky that there is a parameter set which could work.
just a guy said:
You're welcome!
Right, at the time, little seemed to be understood about how a tapped horn worked or how to design them and I didn't/don't have any real desire to obviously let any design 'cats out of the bag' that the 'inventors' haven't already published, but for those who are willing to do 'due diligence' Vs the 'scumbags' that just want to steal other's work for profit, I occasionally try to drop hints, though for the most part they seem to go unnoticed by virtually all who post. I haven't read all the thread's posts though, but the only one I'd read before yours that picked up on it not being unique to PB's design was WC.
GM
MaVo said:
Greets!
IMO to XO a TH much above 80 Hz the driver needs to be end loaded at both ends to minimize the amplitude of its out-of-phase HF.
WRT its rising response, as me and others have periodically noted, this is desirable for most low tuned alignments since it blends better with all but the largest typical room gain curves than a maximally flat one.
Anyway, here's an example you can tune a bit with series resistance:
GM
