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Questions about Midrange Horns

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JulianDA View Drop Down
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    Posted: 05 February 2020 at 1:14pm
Hi there!

I have a few questions that came up while i started designing a midrange horn for a driver that was collecting dust in my basement. So the Project is just for fun and to learn more about the horn design process. 

The Horn will be designed around the Oberton 10M300 Chassis and should cover something like 200-2000/3000Hz. 
Since i came across a few hornloaded midtops at different partys and events (like the please in Frankfurt), i had a rough size for the horn in my head (You know the typical F1, Turbosound or Void Midranges). I have also read a lot of the horntheory in the form of scientific papers.

But here lies the general problem. In theory everyone says, that a perfect horn should be designed so that its cut off frequency is about one octave lower than the desired actual frequency of the highpass in order to exclude the biggest peak in groupdelay from the operating frequency range. This seems absolutely logical to me and i would like to do excactly that for a nice sounding horn in the mid and high frequencys. 
To get there, my horn would have to be 1,17m long and have a mouth area of almost one square meter (so the cut off is at 100Hz and i can use it from 200Hz up). This seemed just a little to big to be practical, so i started to look at the commercial horns and did rough simulations.

For example there is the Funktion One Evo 6EH. It has a 10" Midrange horn that is roughly 40x60cm and cant be deeper than 50cm (the whole box is 56,5cm). They state that the frequency range starts at 170Hz and in the Crossover settings they state to use it from 180Hz upwards. 
If i put the horn data into hornresp (so S1 between 100 and 300cm2, S2 at 2400cm2 and L12(exp)at 50cm) the minimum cut off frequency i get is 200Hz with a groupdelay peak of 6-7ms between 200 and 300Hz (depending on S1). 
I get the same results for all the other designs too. 

So is everyone using their midrange horns to the absolute minimum cut off frequency including the big groupdelay peak that comes with it, or am i making a mistake?
(or maybe really everyone does it and thats one of the reasons that all the F1 Tops that i listened to sounded good with Electronic music, but, lets say, questionable with everything else)

So is there someone that can answer my question and maybe get me on the right way of designing my horn?

Cheers, 
Julian
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Elliot Thompson View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 05 February 2020 at 5:08pm

A lot of commercial horn designs are based on using multiple boxes in order to create one large horn. It is not uncommon to have measurements based on half-space or to a lesser extend quarter-space. Also, some will actually vent the box to achieve an extended low frequency response.


Group Delay, like Phase, is not mentioned in a lot of horn designs for it would not make the design as impressive as marketing claims.


Best Regards,




Edited by Elliot Thompson - 05 February 2020 at 5:09pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JulianDA Quote  Post ReplyReply Direct Link To This Post Posted: 06 February 2020 at 1:31pm
Thanks for your reply Elliot!

I know the fact that you have to use multiples of most horns. What baffles me, is that some designs like lets say the Void Air Motion is clearly a standalone Top (maybe used in duals). And with its ~2300cm^2 horn mouth and roughly 40-45cm length of the low-mid horn it should not be able to achieve the stated 140Hz. The same story goes for the Air Vantage, and those are not ported.
But still i got to listen to both tops quite often and they sounded good to my ears (but i have to say the music was always psytrance or techno, i think live music with a singer would not be as good)

I would like to design a Mid-horn to sit over the latest design of my kickbin, so it would start at roughly 250Hz. But i really dont want a ported design, since i just designed the kickbin to get rid of the resonator (They were HD15 before). I dont want to introduce another resonator even higher in the frequency range LOL
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Elliot Thompson View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 06 February 2020 at 6:45pm

Achieving 140 Hz could be accomplished from a horn that is not ideally 140 Hz. The loudspeaker will do all the work hence, acting more like a direct radiator in a sealed box. With a high dose of equalisation to boost/decrease certain frequencies, it is possible. Of course, excursion will be greater in a sealed horn than a vented horn.

 

This is one of the reasons why loudspeakers aimed for horn-loaded designs tend to offer more xmax than loudspeakers aimed for reflex cabinets. Loudspeakers designed solely for horns are subjected to work harder by brute force at the lower frequencies as the cabinet is not efficient (large enough) to achieve the desired frequencies with ease below the horns cut off point.

 

You really need to have a good understanding of TS Parameters and not assume the most ideal driver for horns would be the best for such a design when, you are making such compromises in the enclosure design.  

 

Of course, the efficiency/sound will not be remotely close to an actual 140 Hz horn. A 140 Hz straight horn half space will be around 121.9 cm width, 121.9 cm height and, 121.9 cm in depth. That is not taking in account the room to house the loudspeaker. When you create such an imaginary image using measuring tape, how many boxes have you actually seen/heard that falls within that category by commercial manufactures produced today?

 

Only boxes that stem from the era when valve amplifiers were standard would you have an opportunity to see commercial manufactures promoting horns of such size.

 

Best Regards,     



Edited by Elliot Thompson - 06 February 2020 at 6:53pm
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gen0me View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 16 February 2020 at 11:30am
Depending on the shape of expansion you will get different frequency responses at the bottom end. More exponentioal expansion and you will get more flat characteristics than with conical expansion.

Edited by gen0me - 12 March 2020 at 12:16pm
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