square tractrix midhorn vs circular?

[pumpkin1]

I am planning on building Volvotreter's design for a 77hz conical midbass horn. I want to use a Radian 850pb cd in a tractrix 300hz horn from 500hz up. Without wood turning skills, it appears a square or rectangular tractrix would be easier to build. I don't see many of these, is round inherently better?

[John Sheerin]

The main problem with square is that you have a round diaphragm in the compression driver and a round throat in the driver which is the start of the horn. If you now mate that up to a square horn, you've got a big discontinuity. If you don't design and construct a good transition, you will get diffraction which will have a negative impact on the sound quality.

You might try building a petal horn (like an old phonograph horn). This can be built to be very close to a round horn, but you cut all the pieces out of flat stock. I think there are spreadsheets around that do the calculations for you.

[bear]

you might want to follow the JMC thread on his horns... he has a calculator you can download for a petal horn...

How high up do you want to use the tractrix??

if it is not too high, then there are few concerns... I'd just make a throat section that starts round and gradually becomes that "square" form... a two part horn... you can also round off the 90 degree inside corners with a nice 2-4" fillet if you are ambitious.

What did you intend to build out of??

_-_-bear

[tomi]

I've heard it said (although without any explaination to back it up) that circular horns give a smoother frequency response. I suppose one considderation is that the square horn introduces the possibility of resonances between its parallel sides.

[pumpkin1]

THanks John- I've read a lot of your posts- you know your stuff. I don't know enuf to avoid the suggested diffration issue. I need plans to follow. I'm having difficulties just playing with hornresp. For example, is there any way to have a 77hz conical horn bend up 90 degrees without hurting the sound? Can that be modeled in hornresp?

Bear-the plan is to use my old HSU true sub from 20hz-50hz, a tap horn to 90hz, the 77hz conical horn to 500hz, the radian 840pb on a 300hz tractrix/iwata to around 10k, and a tweeter horn above that. I'll use plywood.

[woody]

You might ask Bruce Edgar the horn expert. In the past he even published plans for
a 300 or 350 hz rectangular tractrix horn. As of a few years ago he even offered
this rectangular horn in raw hdf for a VERRY low price. Just do a google for Edgar Horn.

[pumpkin1]

Thanks woody-I will search, but I just found what I think is probably the easiest DIY version of a tractrix I've seen, assuming I could find this bendible MDF he used. It's from the Klipsch site-225hz. Is there an obvious issue as far as the round throat to rectangular horn? Klipsch audio systems

Has anyone had experience listening to AG Duo's so that they might compare their compression horn system to the Duo's?

[John Sheerin]

The throat transition is still an issue. As long as the walls are not parallel, resonances really shouldn't be an issue. Here's what I came up with in a horn I was playing with (but only on the computer - never built it). It has a radius in both planes that is tangent to the throat of the driver and the walls of the horn. The section in the corner is the hard part.

[bear]

Originally Posted by pumpkin1

THanks John- I've read a lot of your posts- you know your stuff. I don't know enuf to avoid the suggested diffration issue. I need plans to follow. I'm having difficulties just playing with hornresp. For example, is there any way to have a 77hz conical horn bend up 90 degrees without hurting the sound? Can that be modeled in hornresp?

Bear-the plan is to use my old HSU true sub from 20hz-50hz, a tap horn to 90hz, the 77hz conical horn to 500hz, the radian 840pb on a 300hz tractrix/iwata to around 10k, and a tweeter horn above that. I'll use plywood.

You can fold a bass horn - conical or not...

Myself, I'd not want to use so many divergent types of drivers/horns in a system. The philosophy I prefer is to find a single source to cover the maximum range +/- 1kHz., like 250 ---> 10kHz or better, and a single way to cover below that... I feel that having the entire midrange in one driver is a significant benefit sonically speaking.

As far as the bass region, by the time you put all that stuff together below your relatively high (500Hz) horn, you'll have a big volume already. So why not just design something that covers from the bass up to some viable frequency (~300Hz?) and then something from that point up??

something along the lines of an modern variant of the Altec A7 box or else a rear loaded horn/front loaded mid horn variant will do that trick nicely. (you can likely dispense with the front mid horn and do direct radiator)

any time you do a 90 deg sharp bend at an exit, you have diffraction - but in a bass/low mid maybe it's not important...

have fun!

_-_-bear

[pumpkin1]

I can appreciate that I am using a lot of low frequency drivers, but I'm trying to use them in a way that lets them cover their intended frequencies w/o a lot of distortion. I agree that it would be nice to avoid more drivers in the mid/high, but realistically, there are few CD drivers (affordable) that will handle from 300hz up-and that also requires a very large horn-another difficult thing to produce. I also don't think the introduction of rear loading gives the same clarity of sound. Ultimately, your suggestion is good if I want to spend a fortune on a very high end driver like an ALE to manage that 300hz-whatever. I paid less for my used DUO's than that driver costs! I'm also coming to the conclusion that I might just be happy to keep my AG Duo's and attempt just to replace their poorly integrated sub w/a horn sub- so basically need to go from 170hz down in a good/fast horn design-any suggestions?