Beyond the Ariel
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 Multi-Way Conventional loudspeakers with crossovers

 Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Jmmlc
R.I.P.

Join Date: Oct 2005
Hello Lynn,

The expansion of the wavefront area for a Le Cléac'h horn follows the general formula for the hyperbolic horns.

See formula (11) in Bjorn Kolbrek' excellent paper "Horn theory" published by AudioXpress:

http://www.audioxpress.com/magsdirx/...olbrek2884.pdf

For the DIYer the T value can be chosen from 0 to a value over 1.

T = 1 is for an exponential expansion of the area of the curved wavefront. With most high efficiency drivers this results in a slightly upwarding slope of the frequency response curve.

For T =0 you'll obtain a horn with a catenoidal expansion of the area of the wavefront. It is rarely used (but simulations of Le Cléac'h horn with T = 0 shows very few reactance above the acoustical cut-off (but a narrow and tall peak of reactance at acoustical cut-off frequency)

Martin Seddon's Azura horns generally use T from 0.7 to 0.8. This gives a very flat frequency curve on axis. Give a look to the measurements:

http://www.azurahorn.com/Yamaha_on_204.pdf

http://www.azurahorn.com/Yamaha_on_204.pdf

Values of T lesser than 0.7 may be interesting with a driver having (when loaded) a resonance frequency near the acoustical cut-off of the horn.

Low T value also results in longer horns.

Large T values over 1 lead to profile having similarities with conical horns.

Estimation of the acoustical cut-off frequency of a horn from the perimeter length of the mouth is IMHO useless for quasi-infinite horns like the Le Cléac'h horn (or with the Kugelwellen if mouth opened at more than 360°). I call quasi-infinite horns, horns whose mouth shape is able to reduce drastically the reflection of waves (and diffraction at the edges of the mouth).

Measurements shows that if a Le Cléac'h horn profile is calculated with a full mouth curvature (360°) then its cut-off frequency is exactly what was introduced in the calculation (by my spreadsheet or by HornResp ).

The crossover solutions I studied are not devoted to the Le Cléac'h horn specifically. My goal was to obtain low phase distortion and very constant "in coincidence response curve" (this differs of the "power response curve".

Best regards from Paris, France

Jean-Michel Le Cléac'h

Quote:
 Originally posted by Lynn Olson Jean-Michel, I want to thank you for joining the thread - as the designer of the Le Cleac'h profile, I give particular weight to your remarks. I was curious myself about the air-load reactivity of the larger vs smaller horn, and the possibility of "wasting" some of the potential midrange bandwidth of the 1.4" format 288 compression driver due to the 550 Hz horn being just too small to take full advantage of it. (If that's true, perhaps the best application of the 550 Hz horn is to mate with 1" format compression drivers.) I've been curious why the 340 and 550 have the cutoff frequencies they do, since the 340 is just about twice as large (in every dimension) as the 550. At first glance, it would seem like either the 340 is really a 275 Hz horn, or the 550 is really a 680 Hz horn. Martin Seddon tells me that with a 1-3/8" (35mm) throat and mounting plate (to match an Altec 288), the AH-340 is 349mm long, has a 600mm overall diameter, and is 500mm across when measuring the portion of the horn-mouth that is at a 90-degree angle to the central axis. With the same size mounting plate, the AH-550 is 168mm long, and has a 300mm overall diameter (and I'm guessing is 250mm across where the flare reaches 90 degrees). I'm curious what the "T" function of the equation represents - is that the net overall flare-rate of the entire horn, or a ratio that represents possible shapes with either more or less curvature than a Tractrix? Does this control the sharpness of the acoustic highpass filter? I plan to use an elliptic highpass function with the notch tuned to the Fs (in the horn) of the 288 driver, in order to control out-of-band excursion as efficiently as possible, but without the time-domain penalties of a high-slope 24 dB/oct crossover. This filter topology should allow freedom from having to "tune" the horn cutoff and rear-chamber volume in order to form an acoustic highpass filter - this was necessary when the Altec 12 dB/oct crossover was all that was available, but today we can use more sophisticated filter functions to control excursion and optimize time-domain response. I'll also looking at the filter function you have described on your web-page - whatever gives the best performance for the application (which in this case is mating with a 12" woofer, either Altec 414, Tone Tubby, or 18Sound). If the 340 delivers an extra half or two-thirds of an octave compared to the 550, that's a considerable advantage in terms of matching with the 12" woofer, regardless of crossover topology.

 2nd April 2008, 08:02 PM #3272 Anglo   diyAudio Member   Join Date: Mar 2008 Lynn Thanks for the response. I'll show you some measurements and maybe we can work from there? ++++++++++++ >Beaming sounds unnatural to me< I am aware of beaming, I have a 15" wideband driver that is run fullrange. I know, scary. Now what exactly sounds unnatural to you with regards to beaming? Thanks
 2nd April 2008, 08:06 PM #3273 JoshK   diyAudio Member   Join Date: May 2004 Location: Toronto, ON I abhor the head-in-a-vise affect of beaming. Move your head a fraction of an inch while listening and the FR changes. No thanks. But then again I am a type #2 & type #3 type.
 2nd April 2008, 08:44 PM #3274 Anglo   diyAudio Member   Join Date: Mar 2008 Thanks Josh Tell me, how can one measure beaming? Would it be safe for me to say, I should put the meter on axis and just measure one driver, the one that would present beaming? Thanks
Magnetar
Banned

Join Date: Feb 2004
Location: Portal 2012
Quote:
 Originally posted by Anglo Thanks Josh Tell me, how can one measure beaming? Would it be safe for me to say, I should put the meter on axis and just measure one driver, the one that would present beaming? Thanks
The easiest way is to put on some music and move your head around. If the sound changes a lot then the speaker is beaming. Panel speakers and big non-CD horns are the worst for this in my experiance. It really screws up the 'power response' too, very unnatural and fatiguing to me. Seems some people live with it though. Big headphones unless you move

Jmmlc
R.I.P.

Join Date: Oct 2005
Lynn,

May be that's the legend of the picture:

http://www.homecinema-fr.com/forum/a...php?pic_id=798

In fact, the legend of the picture is erroneous and the system on the picture don't use a single Lowther driver. This system was demoed by Marco Henry at the last Hifi show in Paris few weeks ago and the drivers are 2 x 46centimeters PHL on open baffle (in the corner of the room) to reproduce the lowest frequencies. 2 x Altec 515 in small front horns for bass, one Radian 950 (from memory) on the large circular 200Hz horn and then a small BMS compression driver on 500Hz horn for the high mid + treble.

It was the best sound of the show.

About 2" drivers, a friend of mine use a JBL2441 but with a Radian diaphragm and I could listen his system and appreciated it a lot (far better than with the original JBL diaphragm).

Best regards from Paris, France

Jean-Michel Le Cléac'h

Quote:
 Originally posted by Lynn Olson JMMLC, thanks again for the detailed design criteria for your horns, and the parameters that you've chosen to optimize. I guess I would fall between the Group 1 and 2 listener, although I don't much care for the "giant headphone" effect of some of the biggest horn systems. The big systems I've heard (with Lowther drivers) had almost no depth reproduction at all, but I could lay that at the door of the Lowthers, with their very uneven wavefront going into the horn thanks to the whizzer driver. A rough, incoherent wavefront at the input end will surely be far worse when it comes out the other end, and that in turn will have severe effects on time-domain and polar-pattern performance. Marc Henry (of Music Concrete fame) is reporting good results with the 340 Hz horn and the big Radian 950 (2" throat, 4" aluminum diaphragm with Mylar surround) compression driver. JMMLC, are there any other drivers that are personal favorites - old and new?

 3rd April 2008, 03:43 PM #3278 Anglo   diyAudio Member   Join Date: Mar 2008 Hi Thanks Josh and Magnetar for your response. I do know what beaming is, it is the unnatural part that got me intrigued. Of course when sitting in the "sweetspot" the sound is fine and yes once you move out of that spot, well--- it is a different story! I understand what you mean by unnatural when it is explained this way. Again, thanks and yes I agree. The thing is the slam and weight that the big (see here 15") wideband driver gives makes any other " less beaming" driver (see here smaller) seem obviously smaller. Instruments lose weight and they sound empty, somewhat filled with helium air at times and tone also lacks density. Those aspects bother me, but again if I could tame the beaming I would probably be "happier". Any suggestions for this would welcomed. Is there anywhere in this thread where the beaming of a big driver used as a wideband covering the most critical part of the sound i.e 200hz to 4Khz has been talked about? ++++++ Lynn, o.k. thanks. I will do such measurements and address the floor bounce. Looking forward to addressing some issues. Thanks,
 3rd April 2008, 05:53 PM #3279 John L   diyAudio Member     Join Date: Oct 2001 Location: Cary NC Gosh, this has got to be the most successful thread I have EVER seen! It is impossible to go through it all in a practical sense. So, let me ask: Are all the items that go into the Ariel, still current for purchase? __________________ My Home Site & Favorite Battleground
Robh3606
diyAudio Member

Join Date: Nov 2002
Location: Destiny
"Is there anywhere in this thread where the beaming of a big driver used as a wideband covering the most critical part of the sound i.e 200hz to 4Khz has been talked about?"

I will post a LEAP plot for you of a 15 on an IB board. There is quite a bit of beaming going once you get above 1K. You also use this old nomgraph. I like the LEAP plots better.

Rob
Attached Images
 -6db points.jpg (79.0 KB, 1075 views)

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is Off Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Site     Site Announcements     Forum Problems Amplifiers     Solid State     Pass Labs     Tubes / Valves     Chip Amps     Class D     Power Supplies     Headphone Systems Source & Line     Analogue Source     Analog Line Level     Digital Source     Digital Line Level     PC Based Loudspeakers     Multi-Way     Full Range     Subwoofers     Planars & Exotics Live Sound     PA Systems     Instruments and Amps Design & Build     Parts     Equipment & Tools     Construction Tips     Software Tools General Interest     Car Audio     diyAudio.com Articles     Music     Everything Else Member Areas     Introductions     The Lounge     Clubs & Events     In Memoriam The Moving Image Commercial Sector     Swap Meet     Group Buys     The diyAudio Store     Vendor Forums         Vendor's Bazaar         Sonic Craft         Apex Jr         Audio Sector         Acoustic Fun         Chipamp         DIY HiFi Supply         Elekit         Elektor         Mains Cables R Us         Parts Connexion         Planet 10 hifi         Quanghao Audio Design         Siliconray Online Electronics Store         Tubelab     Manufacturers         AKSA         Audio Poutine         Musicaltech         Aussie Amplifiers         CSS         exaDevices         Feastrex         GedLee         Head 'n' HiFi - Walter         Heatsink USA         miniDSP         SITO Audio         Twin Audio         Twisted Pear         Wild Burro Audio

 New To Site? Need Help?

All times are GMT. The time now is 07:11 AM.