Bass Horn Design Question (throat)

[just a guy]

I am able to recreate the same 14-Hz Hyperbolic-Exponential horn in Hornresp. I am still however unable to create an Exponential horn, with a throat area greater than 99,999 cm^2.

Like I said, I don't like pure exponential horns so I never tried this before, and now that I have I see what you mean, it won't allow a mouth greater than 99999.99.

The workaround is to create a hypex flare and then manually change the T to 1. That should give you a pure exponential flare.

Or as I mentioned you can try TL.app or Akabak.

I'm still going to recommend you try T = less than 1. Post up your design inputs when you get the sim working.

 

[Entropy455]

tb46, I used Bass-Box software for that system (hornresp is still brand new to me).

The boxes are tuned for 30-Hz. I hooked up my signal generator, and swept from 100-Hz down to 10-Hz. The tune is nuts-on at 30-Hz (virtually zero cone movement, and very appreciable airflow in the port). I cranked up the power, and thought I was going to rattle sheetrock off the wall! And below 30-Hz, the speakers become noticeably unloaded, and I would say they’re completely unloaded at 18-Hz (where there’s a lot of huffing and puffing – and no sound). I broke the 12s and 18s in using an 18-Hz sinewave – for about 12 hours. The 12 inch drivers actually made some noise at 18-Hz (due to the sealed box), but not much. The only thing I really noticed during break-in was the skylight, and a few pictures on the wall were rattling a bit.

Within the bandwidth however, things change. . . . My front door knob has an obnoxious rattle right at 30-Hz. And my oven/range sounds like someone is taking a needle gun to it at 36-Hz (I need to do something about that. . .)

 

[tb46]

Hi Entropy455,

Thanks for the follow-up. So, now you're working on the fundamental wall frequencies w/ the full-size horn?

Regards,

 

[weltersys]

1) My plan is to make no-kidding curved exponential horns, using several layers of thin plywood and a crap-load of form-stiffeners. I must admit, four conical segments would be MUCH easier to frame & cast from concrete. . . . I really need the most recent version of Hornresp. . . .

2)The next large design obstacle on my mind, is the time delay caused by the physical driver offset.

3) Does anyone make a fully digital domain circuit, to accomplish this task? I’d like to keep my signal processing fully digital – i.e. from the CD source, through the time delay processor, and through the coross-over network (if possible). I’d prefer to go analog just prior to amplification. I found one delay circuit on the market, however it has an A/D converter on the front-end, and a D/A converter on the output - which is a big turnoff for me. . . . In my opinion, these type of devices tend to be noisy.

4)The only problem I see with this, is the air itself becomes an impedance problem across long distances – particularly above 7-kHz (which is why thunder at distance only booms, and doesn’t crack). I’m not sure if the extra 50 feet or so will make a noticeable difference or not? The bass horn walls & mouth might actually get in the way. My gut tells me Example B will cause more problems than it solves. . .

Entropy,

1) Over four decades ago I was very much into the "purity" of straight (not folded) curved exponential horns. After hearing several systems that out-performed mine using far less truck space, in 1981 I did extensive A/B testing between the same bass and low mid horn flares approximated with 3 sections, then with two sections. They all sounded virtually identical, though the straight section plywood was easier to make stiff than the damped fiberglass curved horns.
Then we truncated 15" off the offset horn (45" depth was problematic in many theaters we worked in due to the fire curtain space restrictions) and added bass reflex ports to the cabinet, adding another octave in response in a cabinet 33% smaller.

2) Digital sound processing (DSP) has advanced in the decades leading to this century to the point where delays are just another boring calculation done at minute fractions of the time duration of a 20kHz sound wave.

3) There are dozens of good companies making DSP with SN ratios better than compact disk recordings, and amplifiers with built in DSP.

Although DSP can compensate for any "time of flight" distance on axis, it can't off axis, so using a virtual single point source for the more critical upper frequencies is "the way to go" for uncolored off axis response.

To keep SPL even across long distances, elevation of the top cabinets is crucial to compensate for inverse distance losses. Unfortunately, elevating a huge bass horn is an expensive proposition, so best to keep the low crossover point at 100 Hz or lower to prevent the vocal image from "walking" up and down the vertical seperation when transitioning from baritone to soprano.

Here is a contribution to the multi-way virtual single point source concept:
http://www.diyaudio.com/forums/mult...ual-single-point-source-horn.html#post4114406

4) Air absorption at high frequencies (HF) is primarily a problem in dry, hot locations.
After 20 years in the hot, dry, high desert conditions in New Mexico, to a town near the east coast of Florida, the doubling (or more) of humidity has made it seem like my hearing is better than it was 20 years ago, as the HF is more than 10 dB louder at distance here.
This calculator will allow you to figure the HF air attenuation in any environment:
Calculation method of absorption of sound by atmosphere air damping dissipation absorbtion high frequencies attenuation sound during propagation outdoors outdoor - sengpielaudio Sengpiel Berlin

Art