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In the Forum: Horn-Loaded Speakers
In the Thread: The European Triode Festival’s horns
Post Subject: The Big Throat Approach and the Wide HornsPosted by Romy the Cat on: 6/16/2008

 nl wrote:
Within that horn-loaded range, the 210/515 type combo does reasonably well, and produces rather more inspirational midbass than most direct-radiator type strategies. There is a reason why these designs persisted for roughly forty years, until replaced by smaller/cheaper/inferior sound systems (but with better low bass) to match the smaller/cheaper/inferior theaters built since 1985 or so.

Well, yeas and no. Although I agree that 210/515 type combo does reasonably well in lower midrange and upper bass but it has in my view a different upper bass then I would like to be. The 210/515 type combo never was able to play soft, nether dynamically nor tonally. Also, I personally never saw a successful integration of 210/515 type combos with lower frequency channel. All those open baffles as soon they reach the region of acoustical shortage do something to sound that poisons me. 

 nl wrote:
So, as I said, it would be interesting to understand what one gains or loses by this method instead of something very difficult to implement such as a 10 foot long 70hz horn with proper compression loading. Much easier to time align as well, which is one of the reasons for their original development in the 1940s.

OK, let look at the typical 210-like horn with 50-70Hz and dual 15” throat - we understand that it is short and wide horn, very similar to what Cressaro and many others used for their bass bin. I call it the “big throat approach”… I have writhe about it many times, look in my “Problems with horns: upper bass “thread linked to this thread. When I see the 210-like horns I always ask myself what kind of driver I need to use in this configuration. Let pretend that it is 50Hz horn, then what driver? The common rules suggest that I would need a driver with let say 45Hz resonance frequency but the Wide Horns do not load LF. We take the driver in open baffles and measure it response. Let pretend that it has 100dB at 90Hz. Then we load the driver in the horn. The end of the 210-like horn working as a horn will be not what the circulation of mouth suggest but where the driver stops hitting 106dB (depends of profile it might be more or less but 6dB is a good average). The 210-like horn will not have a lot of horn gain. The response will be speeding lower than in open baffles but it will not be the horn EQ but rather the driver acting as a direct radiator. Then we have more problems. The driver is capable to do now 50Hz as a direct radiator but the mouth is 70Hz. Some say not a big deal, in fact many idiots stick 20Hz driver into 50Hz horn but that destroys everything sonically. So, my point is that in a properly sounding horn-driver configuration the bottom of the channel response shell be the sound of horn not the sound of driver. It is imposable in 210-like horns unless you high-pass the horn at I would say 100Hz-120Hz. Then you have correct sound out of the horn but at colossus waste of the horn mouth. You can get the same effect if you use a driver with free air resonance frequency of 80-100Hz but again: why would you need 50-70Hz mouth for such a driver if the horn can’t not yield the LF gain. In my view the direction is to minimize the size of the throat and unfortunately brings the length of the horn all the way up.

So, how I found the 210-like horn with good driver sound?  It is important to understand that from my perspective there is no good drivers for 50Hz horn and 2x15” throat, there is no good hypothetical driver as the shell be cut off at 120Hz to serve inters of sound instead of the interest of  acoustic pressure. Among the few 210-like horns that I heard they all sound absolutely in the way I am describing: the excessive LF on the woofer chocks the horn’s bottom knee, making sound very hard and very stiff. The last my exposure to the mistakes I describe above was last year when I visited the Oswalds Mill guy. He has the bottom born of the same idea: modified RCA ~40Hz mouth with a pair of 22Hz Altec 515E loaded into the horn.


I usually do not comment about my private visits publicly but in the case of that dude my rules off the limit and the Oswalds Mill guy fully endorsed my attitude. So, that version of the 210-like implementation sounds spectacularly horrible and it is not an accident. Anything below 200Hz was literally shattered by the high pressure-boom coming from those horns. it sound like you have month fill of water and you are trying to sing - a horrible feeling. The Oswalds Mill listening space is huge and it dissipates a LOT of low frequency, so Jonathan was forces to crank up power at bass but the more powers this choked horn endure the more horrible it sounds as the choking in effect rise with volume of the horn.  As the result anything under the lower midrange sounded like wet dog and was truly revolting. I did not explain to the Oswalds Mill guy the details – he is not particularly smart man in audio and he not particularly knows, cares or express any interest about sound, We just listing some records I brought and it was extremely indicative. We were playing the Tchaikovsky’s Pathetique symphony and I asked the Oswalds Mill’ wife what she thinks about this music. Thanks God they do not know is and her reaction was very interesting and natural. She said that she has a difficult time to understand it because all orchestra sounds the same and there was not a lot of thing doing on between instruments. I have to add that we were listening Mravinsky from 1961 – the most articulated Pathetique even committed to record media to my knowledge. Sure, I did not explain to her that it was not Tchaikovsky or Mravinsky faults but the sonic deserters her husband implemented in his bass horn.  However, her very natural reaction was a very good depicture of what I am trying to say – the bass horn are dangers and it is better do not do it if they are not done properly. I am sure if the same Oswalds Mill guy stick 4 drivers on sealed/ported box then he would avoid many horn mistakes he made.

Rgs, Romy the caT

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