doityourself

"For a long time, the thought has been in my head to create a speaker based on the tractrix midrange horn. This is spurred by my dissatisfaction of the resonances and coloration inherent in my Cornwall's exponential horns." A bass horn is going to have all kinds of resonances and coloration. You'd better keep your Cornwall bottom end and concentrate on the midrange only.

My panasonic dvd recorder or a BD30 blu-ray player!

It depends on where the music falls in the audio spectrum. If it's concentrated in the 1-5 khz range it will sound piercing at even lower volume. That part of the spectum is where our ears are most sensitive. 105 db in the lower octaves won't be piercing.

Here's a graph by reversing the tweeter polarity and also reverseing the wiring to the midrange-tweeter. It solved the "suckout" at 3.5khz and caused a greater "suckout" at 300hz. I'm relieved now that the upper suckout is fixed. I didn't think my new "horn" rolled off that bad in the upper range. I'll see if it actually sounds different.

Here's a graph with the revised 3500 hz tweeter crossover. Still have a dip beginning at 2.5khz but new crossover did fill in dip somewhat. Dip is barely noticeable on 1/3rd octave white noise test. I can't say I hear anything lacking. The T35 has a noticeable rise from 3.5 to 8khz or so flattens and than drops. Some testing with only midrange horn running the response comes back at 5khz and extends to 6.3khz but is 4db shy of what it is at 1khz. I'm running a coil or roll off top end that is calibrated for an 8 ohm speaker at 5khz but this driver has about 15 ohm impedance at 5khz thus the coil isn't doing much.

Here's a chart I posted a yr ago or so. Not the same style of chart but you can see the dip around 4khz. I need to produce an updated chart with lower tweeter crossover freq.

I ran the T-35 down to 3500hz with a coulple of more capacitors to fill in the gap nicely in the 4khz range. Here's the finished product. Sounds nice.

I don't know about optimum mouth size is as critical as it sounds. I built a Table Tuba subwoofer that is horn loaded. It's a 13 ft length horn inside a 30x30 box 18inches wide. Mouth size is roughly 18inches by 22 inches. Sounds good down to 30 hz or so. Puts out more sound below 40hz than the khorn and it's only running an 8 inch Ford Explorer subwoofer! Corner placement is recommended but not necessary. Mouth size could be as narrow as 12 inches if used in a corner.

I found out by adding a 2 and 1 uf cap I could convert it to a 3500 hz 12db crossover that is identical to the X36 EV module. Sounds good. I doubt I'll burn out the VC since I don't play at part levels very often. I did burn up a set of diaphragms by running sine waves at higher wattage without realizing it! Smelled that burnt smell and that was it! The extra output in the 3-4khz fills out my hole real nice.

I have a hole in the 3-4khz range with my audax driver and tractrix horn and was thinking about running the t35 down to 3500 hz with a 12db crossover. Is this going to be safe? Only running a 60watt channel amp and hardly wide open. Is the hole being filled by the t35 going to be worth the risk? The audax with horn is too strong in the 5-6.3 range. I noticed when I built the low pass filter I figured on an 8ohm driver but the audax is more like 17 ohm at 5k. I need to change my coil to compensate.

The efficiency is rated at 100db/watt but some charts show only 95 db eff. between 400-1khz and than a rising response. There has been some conflicting graphs among the years. The midrang Edgar Horn article suggested using a JBL LE-5 driver with a 2inch throated horn (just longer than mine) for a 105 efficient horn. Not sure how hard those drivers are to get a hold of. The Audax is about $83 at Madisound. I saw a pair of Audax midranges (earlier model than mine but same model as Edgar used) that didn't sell for $35 on ebay a couple of weeks ago. Edgar mentioned that some cone midranges don't make good horn drivers but doesn't mention what models he tried. Just make a simple horn like mine on the first photo and experiment. Start off with a 2 inch throat and chop it off if needed.

Here's a freq. resposne graph. It does show the dip at around 4khz. My "unhorned" audax showed the same dip. Nothing to write home about but with 1/3 octave noise with my meter it shows within 2db from 500-2khz. Perhaps running the T35 down to 3500 and using a 12db filter on the audax would get rid of the dip.

I mentioned ringing but perhaps resonating is a more proper term. I haven't owned any midrange horns before to know of the affect. Here's a picture of the more finished product. Have to finish the outer corner trim, stain, and finish. Ran a freq. response with Audax sealed against horn and it is very flat except between 3-4khz but comes alive again at 6.3 (typical Audax response-perhaps a lower crossover to kill energy at 6.3 is needed). No horn coloration or maybe I got used to it already. The horn really helped the lower range of midrange (500-800hz). Balances nicely with the khorn upper midbass bump.

When installed an air bag "clock" spring in a Ford product they used to give you a small container of paste that you put on the terminals. Can't remember the name but that's what I'd put on a wire that is not making postive contact. I've got some in my toolbox and use it occasionaly.

Here's a full length picture. Bottom unit is the later Speakerlab model that has been scaled down on the outside but internals same dimensions as Khorn.