Some questions for the horn guru!
Steve,
Thanks for chiming in on our thread! I value your input and knowledge of horn design and theory!
Quote:
Originally Posted by
Steve Schell
Hi guys, really good discussion. I once had an early '50s Jensen Triplex three way system that included that back loaded corner horn and it sounded pretty darn good for something of such reasonable size.
Could you comment on the bottom end LF response if you remember from back then?
Opinions vary about the hyperbolic horns though. Dr. Edgar uses a hyperbolic 35Hz. flare in his Seismic Sub to approximate a 20Hz. exponential flare in the nine foot path length of his design. He does this for the reason indicated in the response graph; low frequency extension.
I always thought the horn flare was 35hz and Bruce used EQ to extend the bottom LF response.
I never could see using EQ on a horn for lowering response. Would that not introduce quite a bit of distortion compared to using EQ for a sealed/ported system?
Some have opined that in general a very rapid cutoff will have an attendant rapid phase shift which may sound unnatural. If there is room to use an exponential flare horn of adequate length and mouth size then a more natural sound may result. Problem is that bass horn construction is such a large undertaking that direct comparisons are rarely made.
According to Jensen Technical Bulletin No 3 (1952) which I referenced in a website link previously in this thread, the theoretical flare cutoff is 43hz when corner loaded, if they are sidewall loaded, would the cutoff frequency then be approx 86hz using the 40" horn length?
Thanks from a horn rookie!
Regards, Ron
You have right on the nose.
Quote:
Originally Posted by
Beowulf57
Thanks for the insights Steve. I haven't noted much "boom" down low, as the room resonances higher up in the mid-bass (say around 160-180Hz) are more prominent. I'm intrigued with the actual result of the corner loading continuing the horn flare particularly when the output is from a split 2-section horn and is augmented from the front-firing woofer. Frankly the physics and audio math necessary to figure out how this horn actually performs is beyond me, though Figure 2. in the PDF I posted in post #28 does show the interference effect you have mentioned around the flare cutoff.
If Jensen is specifying the flare cutoff at 43Hz (which has a wavelength of around 26'), I think this must be using the additional flare of the room walls?
Almost as if the entire cabinet is a loading chamber feeding the throat of a 1/2 horn formed by the room corner? I say 1/2 as the top of the horn is open with only the sides and bottom in place (walls and floor). Though I may be way off base (bass...:blink:) here as I don't know how much loading a horn has when one of the 4 walls is absent? However, the Klipschorn seems to work this way. I'm interested in your thoughts on the audio physics of this, since once you are out into the room or in another room, one has the impression of the whole room loading the driver. I recall as a child that my father was playing around one day and cranked the system up full with pipe organ music...he cracked open a window in our den and closed the door to the room before he stepped out into the street. I could have sworn the pipe organ was the whole house as a loading chamber playing for the outside world.
The whole room becomes part of the horn!;)
When I walk from my living room through the dinning room at the far end on the dinning room the bass is just something to feel, coming from my JBL loaded "K" horns. With corner horn speakers the longer the walls are from the corner the better the bass. The effect of the room loading of the horn is something to feel.:)
I've got a pair of those giant Imperials
Quote:
Originally Posted by
spkrman57
Nice link! I have a pair of these beasts in my basement, and it is quite amazing what they can do with JBL LE15B drivers (and with Tannoy dual concentrics, and with Altec 515E's ...) Even with crazy-loud and crazy-low bass making objects dance off the shelves, the cones will have extremely low excursion -- so they sound remarkably clean over the rest of the frequency range. I also have Tannoy GRF-R's, which are a considerably smaller version of the giant Jensens (30 cu ft: 5' tall x 3' wide x 2' deep). With a crossover at 800hz and the HF done with a 2" compression driver on Yuichi horns (which I got from Woody on this forum!), it's a truly remarkable two-way.
A friend of mine was inspired by my pair to build his own, and I recently heard the TAD 1601a in there. Impressive.
After re-reading your post many times.....
Steve,
I think I was getting ready to make a mistake in using a driver in my horns that have a Fs of 40hz (JBL 2225).
Now after reading your post over and over again enough times for my feeble brain to understand what you are trying to say, I'm going to use my JBL D131(reconed w/2202 conekits). They have a Fs of 70hz without being broke-in!
I ordered the cork gaskets for them from edgewound(Thanks Ken!) and after my windows get installed(next week or so), I'll get new baffleboards cut and install the D131/2202 drivers and get them broke in and see how they sound.
If the horn has a theoretical horn flare frequency of 43hz and I have a driver with 70hz, how low will the horn reproduce the bottom LF response?
Thanks, Ron
Quote:
Originally Posted by
Steve Schell
Some designers yield to the temptation of placing the driver resonance down around the flare cutoff frequency. This will produce more output down low, but at the cost of some boom. I have always had better results using exponential horns of low cutoff frequency and placing the driver resonance somewhere up higher in the passband where it is swamped by the horn load.
Sometimes I know better, but have to hear it from someone else to believe it!
Thank you Steve for once again educating us!
I will also explore the issues that occur using the "sidewall" position that Jensen indicated is possible in the technical note No. 3.
I'm guessing that the horn will lose some LF response without the full corner-loading. But I will be interested in trying it out anyways when the time comes. I have to do these projects in my bedrooms as they are the only rooms with usable corners right now!
As soon as windows get replaced the project will continue along!:bouncy:
Thanks, Ron