T Coefficient
I haven't heard any thoughts on the T Coefficient. Looking at the AudioXpress Horn article [wiki=http://www.audioamateur.com/media/kolbrek2884.pdf]%[/wiki]
I'm leaning toward a T Coefficient value between .4 and .6, which seems to be a good balance of loading and SPL output at cutoff. But I still feel the need to do more investigating. Any opinions?
I haven't heard any thoughts on the T Coefficient. Looking at the AudioXpress Horn article [wiki=http://www.audioamateur.com/media/kolbrek2884.pdf]%[/wiki]
I'm leaning toward a T Coefficient value between .4 and .6, which seems to be a good balance of loading and SPL output at cutoff. But I still feel the need to do more investigating. Any opinions?
Not familiar with this horn calculator, but IME, down in the hyperbolic range, there's too much throat distortion, so I personally would only use them well below 80 Hz as even a truncated 70 Hz expo with its minimally 'pinched' presentation through a 500 Hz XO's BW has proven unacceptable over time, so I'm at the point now where only conical WGs are acceptable since I no longer need the extra acoustical loading.
That said, I've seen a number of postings over time where 0.7 - 0.8 has been an acceptable trade-off.
GM
That said, I've seen a number of postings over time where 0.7 - 0.8 has been an acceptable trade-off.
GM
Thanks GM - I'm currently running a pair of conical upper bass horns with 15" woofers, but I'd like to try a pair of Fane Studio 8Ms and get up to 109 db through horn loading to put them on par with my 110 db round midrange horns. Do you have any idea how hypex in the 0.7 - 0.8 range would compare to tractrix?
After re-reading Edgar's Show Horn article, he goes into much more detail than the AudioXPress article and includes many more values of T (I believe the article refers to it as "M"). His assessment leads to a value between .5 and .6 to give the best response down to the flare frequency. In the article, he gives a formula to determine "M" based on the driver parameters at a point which benefits from reactance annulling.
Hello,
I tend to disagree somewhat!
Throat distortion being due to the non linearity of the air itself is generally less harmful (H2 based distortion) than distortion due to large displacement of the membrane (H3).
and for the same input signal the loudspeaker loaded by a conical horn will provide -10dB to -20dB SPL compared to the same loudspeaker loaded by the hyperbolic horn (e.g. T = 0) at the same test frequency taken near the cut-off of the hyperbolic.
Equalizing the response of the loudspeaker loaded by a conical horn will result for the same SPL acoustical output in a very large displacement and therefore to a distortion much more audible (H3 based distortion ) than for .
the hyperbolic horn (and the + 10dB to + 20dB equalization will result in a pressure at the throat of the conical horn in the same range as the hyperbolic.
Best regards from Paris, France
Jean-Michel Le Cléac'h
I tend to disagree somewhat!
Throat distortion being due to the non linearity of the air itself is generally less harmful (H2 based distortion) than distortion due to large displacement of the membrane (H3).
and for the same input signal the loudspeaker loaded by a conical horn will provide -10dB to -20dB SPL compared to the same loudspeaker loaded by the hyperbolic horn (e.g. T = 0) at the same test frequency taken near the cut-off of the hyperbolic.
Equalizing the response of the loudspeaker loaded by a conical horn will result for the same SPL acoustical output in a very large displacement and therefore to a distortion much more audible (H3 based distortion ) than for .
the hyperbolic horn (and the + 10dB to + 20dB equalization will result in a pressure at the throat of the conical horn in the same range as the hyperbolic.
Best regards from Paris, France
Jean-Michel Le Cléac'h
You’re welcome!
Yeah, don't know why T became M over time. Maybe Prof. Leach decided to personalize his T/S compression horn design routine.
Yes, I recall you having some low throat distortion horns, hence my response suggesting you might not want to insert a high throat distortion horn into the ‘mix’, instead implying building a different alignment to get the desired gain BW at low distortion.
Assuming you built a typical tractrix that unloads at ~1.4x above its F0, then the hypex would theoretically need to be tuned similarly, which will cause the excursion issues cited if you don’t oversize it enough for the XO to attenuate it. This will also lower efficiency a little due to it having a wider gain BW. Not many ‘free lunches’ in audio design.
If max efficiency to Fc is the prime design requirement though, then use one of the horn calculators to find the optimum flare frequency, factor that causes it to ‘ring’ at the desired Fc once all the series resistance is factored in.
GM
Just tend ? ;-)
I would add that a good tool to evaluate the linearity of a horn is to compare the impedance curve of the driver on it test tube with the one of the same driver charged with his horn.
It talk a lot in one sight.
[T] & [m] are Subordinate to .....
... the overall dimensions of the horn. [T] and [m] address horn behavior at the lower frequency bound of the horn as well; however, this is true only so long as the horn overall dimensions remain larger than wave length of the low frequency energy passing through it. When wave length becomes larger, [T] & [m] become acoustically transparent and horn length and mouth perimeter become the principal determinants of horn low frequency performance. So, the order of the questions to be answered is:
1) Is the horn acoustically big enough to pass, unscathed, the lowest frequency of interest?
2) Have [T] & [m] be set appropriately for this size horn and the driver to be used with it.
Regards,
WHG
... the overall dimensions of the horn. [T] and [m] address horn behavior at the lower frequency bound of the horn as well; however, this is true only so long as the horn overall dimensions remain larger than wave length of the low frequency energy passing through it. When wave length becomes larger, [T] & [m] become acoustically transparent and horn length and mouth perimeter become the principal determinants of horn low frequency performance. So, the order of the questions to be answered is:
1) Is the horn acoustically big enough to pass, unscathed, the lowest frequency of interest?
2) Have [T] & [m] be set appropriately for this size horn and the driver to be used with it.
Regards,
WHG
Notes
The JMLC 200T provides adequate loading down the recommended 350 Hz. high-pass limit. At this frequency I would recommend a 24 db/oct slope be used. The lower you crossover the compression driver the closer you come to exceeding its displacement limit when reproducing a demanding program signal; so, the steeper filter slope buys you some extra margin. A dc blocking capacitor between the amplifier and the driver will also provide some additional protection; assuming you are using dedicated amplifiers. If you go with a super tweeter, the TAD and JBL/Be compression drivers become overkill options for the mid-range, particularly at a low-pass filter setting of 7 kHz. From my experience, when the horn and compression driver are well matched, limiting coverage to about a decade frequency band yields the best performance.
Regards,
WHG
The JMLC 200T provides adequate loading down the recommended 350 Hz. high-pass limit. At this frequency I would recommend a 24 db/oct slope be used. The lower you crossover the compression driver the closer you come to exceeding its displacement limit when reproducing a demanding program signal; so, the steeper filter slope buys you some extra margin. A dc blocking capacitor between the amplifier and the driver will also provide some additional protection; assuming you are using dedicated amplifiers. If you go with a super tweeter, the TAD and JBL/Be compression drivers become overkill options for the mid-range, particularly at a low-pass filter setting of 7 kHz. From my experience, when the horn and compression driver are well matched, limiting coverage to about a decade frequency band yields the best performance.
Regards,
WHG
200t and TAD
I also own the 200t and tried a TAD TD-2002 With a 1 inch to 2 inch adapter. I preferred my JBL 2440 and other 2445 better with the 1000 Hz Lecleach using the TD-2002. The beaming sounded worse than the Radian aluminum diaphragm in both of my JBL 2440 and 2445 on the large 200t horn. The beryllium would need to band passed If I were to buy the truextent. However I like the truextent's polymer suspension for lower frequency extension on the assumption it is similar to the Radian products. Personally I prefer the aluminum Radian diaphragm because it does not need to be band passed compared to my smaller Tad.
I also own the 200t and tried a TAD TD-2002 With a 1 inch to 2 inch adapter. I preferred my JBL 2440 and other 2445 better with the 1000 Hz Lecleach using the TD-2002. The beaming sounded worse than the Radian aluminum diaphragm in both of my JBL 2440 and 2445 on the large 200t horn. The beryllium would need to band passed If I were to buy the truextent. However I like the truextent's polymer suspension for lower frequency extension on the assumption it is similar to the Radian products. Personally I prefer the aluminum Radian diaphragm because it does not need to be band passed compared to my smaller Tad.
Shortened Large Le Cleac'h Horns?
Does anyone have any thoughts on shortening a Le Cleac'h horn to reduce mouth size? This may come across as a ridiculous question as I understand the benefit of the Le Cleac'h horn is the rolled back mouth flare that reduces waves reflecting back into the horn, but the size of a 100 Hz Le Cleac'h horn (almost 2 meters across) gets impossible to integrate with a multi-way horn setup while keeping everything in phase and avoiding a DSP to compensate. I graphed several curves (Tractrix, Le Cleac'h with T=.55, Hypex with T=.55, and a 105 Hz Le Cleac'h with shortened mouth, the circumference of which is equal to one 105 Hz wavelength. The shortened Le Cleac'h comes in somewhere between a Tractrix and Hypex. It looks like the new profile would have the throat impedance of the Hypex (T=.5). Would the shortened Le Cleac'h horn retain response down to flare frequency better than the Tractrix while reducing reflections closer to the mouth better than the Hypex?
Thoughts?
Does anyone have any thoughts on shortening a Le Cleac'h horn to reduce mouth size? This may come across as a ridiculous question as I understand the benefit of the Le Cleac'h horn is the rolled back mouth flare that reduces waves reflecting back into the horn, but the size of a 100 Hz Le Cleac'h horn (almost 2 meters across) gets impossible to integrate with a multi-way horn setup while keeping everything in phase and avoiding a DSP to compensate. I graphed several curves (Tractrix, Le Cleac'h with T=.55, Hypex with T=.55, and a 105 Hz Le Cleac'h with shortened mouth, the circumference of which is equal to one 105 Hz wavelength. The shortened Le Cleac'h comes in somewhere between a Tractrix and Hypex. It looks like the new profile would have the throat impedance of the Hypex (T=.5). Would the shortened Le Cleac'h horn retain response down to flare frequency better than the Tractrix while reducing reflections closer to the mouth better than the Hypex?
Thoughts?
Attachments
You will loose the low frequency loading . And a fair bit of the directivity control that you are looking for. What you have shown graphically is no longer a LeCleach horn profile.
In short your back to a modified Hypex.
If you are seeking the advantages of a controlled directivity and good loading characteristics down to the horn Fc then you cannot really change the calculation to fit what you want. THere is reasoning behind all this stuff.
And keep in mind that many of the commercially designed horns out there are really compromised in terms of what could be accomplished with proper horn design and unlimited constraints from the marketing departments.
If you are doing your own custom design go for the brass ring buddy.
In short your back to a modified Hypex.
If you are seeking the advantages of a controlled directivity and good loading characteristics down to the horn Fc then you cannot really change the calculation to fit what you want. THere is reasoning behind all this stuff.
And keep in mind that many of the commercially designed horns out there are really compromised in terms of what could be accomplished with proper horn design and unlimited constraints from the marketing departments.
If you are doing your own custom design go for the brass ring buddy.
From what I understand, the response of the Hypex is fairly strong down to the flare frequency, so with this "modified Hypex" would the more aggressive mouth flare impact that response? How would it compare to the full 100 Hz Hypex in the illustration? Would it be better to go with the Hypex over the modified Hypex?
For low frequencies it won't matter much - it's mostly length and mouth diameter. It's the higher frequencies that it will effect. I did some simulations where I truncated the roll back, and basically you need to have the mouth roll a bit past 90 degrees to the primary axis to get most of the benefits. For a horn that large, why not put it on the floor or on the floor in the corner and make a half or quarter horn, still keeping the roll back if you want it to go up to (relatively) higher frequencies?
Thanks for the response John - I'm looking for a range of 100-500 Hz where it will cross into a 320 Hz round tractrix (12db slope). I wouldn't think that range would be too difficult for the horn based on the Hypex simulations I did where it starts slowly dropping at 500 Hz. I understand that a square front 1/2 or 1/4 size horn can work when sitting on the floor, but I'm planning to build a round horn, and I'm assuming that the round mouth wouldn't load to the floor properly. Have you compared the large Le Cleac'h horn with a Hypex? In your simulations, does a 1/2 or 1/4 size Le Cleac'h with its compromises have benefits over a full size Expo or Hypex? Another option is a semicircle Le Cleac'h sitting on the floor...
What I meant was make a section of the a round horn, either half a horn or a quarter of a horn. Like this: http://www.6moons.com/industryfeatures/vsac20082/experience1.jpg