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lower-mid horn design

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roborg View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote roborg Quote  Post ReplyReply Direct Link To This Post Posted: 27 September 2004 at 2:13pm
Actually those drivers do have a vented pole, the vent is mostly obscured by the aluminium plate at the back, behind the little bars. So technically i do have a leaky box, but it's not too much of a leak! In fact when driving hard there doesn't seem to be much air motion at all thru the vent (i hold a piece of tissue near it), so whilst it's probably adding a few losses to the effectiveness of the rear chamber, i think the good cooling is worth it. I've got to get smaart on the job to see how much of an effect the open vents have on the acoustics tho, my suspicion (and hopes ) are not too much....

cheers
Rob
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Timber_MG View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Timber_MG Quote  Post ReplyReply Direct Link To This Post Posted: 27 September 2004 at 3:01pm
<>At low frequencies the rear chamber acts primarily as a compliance and brings the resonant frequency of the speaker up to the mid-band of the horn (ideally) as well as reducing interference of the back-pressure from the diaphragm with the output of the horn. Dynaudio used to have a resistive vent system called variovent (fancy word for leaky box).

In a mid-bass horn there is not that much air-movement as in a bass horn so I doubt whether the dustcap would move enough air for you to see a tissue move signifincantly. The resistance to the airflow from inside the rear chamber to outside would be from the spider and the path through the motor (vc gap depending on the design). Treating the spider might be another way to go about this, but now I’m really going off on a tangent. Suppose for mid-boxes it’s still a fair bit safer to use ferrite magnet drivers.

Martin
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RayVaughn Quote  Post ReplyReply Direct Link To This Post Posted: 27 September 2004 at 7:14pm
Originally posted by Timber_MG Timber_MG wrote:

And you should model into 4x pi, way too little ripple in that plot for it to be a reasonably sized horn (except if you plan on tops much wider than 50cm). That is some extreme bandwidth you have there, but TAD is very expensive and IIRC has around 100W power handling. I generally use Tractrix flares as they end up shorter and show less ripple than hyperbolic/expo horns of the same mouth area (though I may be doing something wrong)


Sorry - that plot was 2pi - here's the 4pi plot:



I thought it looked too good to be true. Perhaps you could check I havent made a glaring error in the input params:


The TAD has a Pmax (RMS) of 300w but they say 'rated power' 150w.
The width of our bass tubes is 66cm so each mouth could be that wide.
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Rog View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rog Quote  Post ReplyReply Direct Link To This Post Posted: 28 September 2004 at 9:33am

Hi Ray,

Can you get me the other T/S specs, like Qts etc.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rog Quote  Post ReplyReply Direct Link To This Post Posted: 28 September 2004 at 10:04am

Found the specs,

Heres how my version of your horn looks.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rog Quote  Post ReplyReply Direct Link To This Post Posted: 28 September 2004 at 10:24am

Hi Ray,

The above plot is using your specs taken from Hornresp.

I've done some modifications and have come up with this.

Horn lenght 0.8 meters

mouth 66 x 66 cm

throat 350 sqcm

rear chamber 15 liters

front chamber 0.5 liters

here is the lot and the expansion details.

 

Dist     sqcm   width angle

0.000  350.00  5.30 10.56
0.016  350.52  5.31 10.56
0.032  352.10  5.33 10.59
0.048  354.73  5.37 10.63
0.064  358.44  5.43 10.68
0.080  363.24  5.50 10.75
0.096  369.17  5.59 10.84
0.112  376.27  5.70 10.94
0.128  384.56  5.83 11.06
0.144  394.11  5.97 11.20
0.160  404.98  6.14 11.35
0.176  417.21  6.32 11.52
0.192  430.90  6.53 11.71
0.208  446.12  6.76 11.92
0.224  462.95  7.01 12.14
0.240  481.52  7.30 12.38
0.256  501.91  7.60 12.64
0.272  524.26  7.94 12.92
0.288  548.70  8.31 13.22
0.304  575.38  8.72 13.53
0.320  604.45  9.16 13.87
0.336  636.09  9.64 14.23
0.352  670.48 10.16 14.61
0.368  707.85 10.72 15.01
0.384  748.39 11.34 15.43
0.400  792.37 12.01 15.88
0.416  840.05 12.73 16.35
0.432  891.70 13.51 16.85
0.448  947.63 14.36 17.37
0.464 1008.19 15.28 17.91
0.480 1073.74 16.27 18.49
0.496 1144.66 17.34 19.09
0.512 1221.38 18.51 19.72
0.528 1304.36 19.76 20.38
0.544 1394.10 21.12 21.07
0.560 1491.13 22.59 21.79
0.576 1596.03 24.18 22.54
0.592 1709.43 25.90 23.33
0.608 1832.01 27.76 24.15
0.624 1964.51 29.77 25.01
0.640 2107.71 31.93 25.90
0.656 2262.47 34.28 26.84
0.672 2429.72 36.81 27.81
0.688 2610.45 39.55 28.83
0.704 2805.76 42.51 29.88
0.720 3016.80 45.71 30.99
0.736 3244.85 49.16 32.14
0.752 3491.25 52.90 33.34
0.768 3757.50 56.93 34.58
0.784 4045.17 61.29 35.88
0.800 4356.00 66.00 37.24

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Timber_MG View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Timber_MG Quote  Post ReplyReply Direct Link To This Post Posted: 28 September 2004 at 11:13am
*runs off to see how to get hold of AJ horn*

Rog, is GedLee's SPEAK any good taht you know of? Other recommendations for Horn-modeling software not listed in your FAQ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rog Quote  Post ReplyReply Direct Link To This Post Posted: 28 September 2004 at 1:40pm

Hi martin, sorry for the late reply, I have been so busy these days.

I've not used Ged Lees SPEAK, but I will try it now. I like AJ horn, for mid top its great and its predictions are good. So what you see is what it sounds like.

Hornresp is good for bass, but I'm not convinced for mid or top horns.

I also use Akabak with my own models of horns and chambers. This is the best way I have found yet. And no, I' can't send anyone the scrpits.

Rog.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Timber_MG Quote  Post ReplyReply Direct Link To This Post Posted: 28 September 2004 at 2:08pm
@ Rog: Thanks, I appreciate the time. Akabak *drool* is a "little" pricey ... methinks AJHorn would be a good value then. The results differ so greatly from hornresp it seems at high frequencies that there is little point to do a mid-horn design with it.

@ Ray: Your diaphragm mass was given as 5 grams and hence you got the insane HF bandwidth . A sim with the T/S of Thielesmall.com differs significantly from Rog's AJHorn plot none the less.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RayVaughn Quote  Post ReplyReply Direct Link To This Post Posted: 28 September 2004 at 3:30pm
Originally posted by Timber_MG Timber_MG wrote:


@ Ray: Your diaphragm mass was given as 5 grams and hence you got the insane HF bandwidth . A sim with the T/S of Thielesmall.com differs significantly from Rog's AJHorn plot none the less.


That's the mass of the diaphragm on the manufacturers website.
The cones a polymer graphite material. I assumed this is one of the reasons why the drivers are £300 each...

http://www.pioneer.co.uk/uk/product_detail.jsp?product_id=14 74&taxonomy_id=43-203

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Post Options Post Options   Thanks (0) Thanks(0)   Quote RayVaughn Quote  Post ReplyReply Direct Link To This Post Posted: 28 September 2004 at 3:39pm
Originally posted by Rog Mogale Rog Mogale wrote:

Hi Ray,

The above plot is using your specs taken from Hornresp.

I've done some modifications and have come up with this.

Horn lenght 0.8 meters

mouth 66 x 66 cm

throat 350 sqcm

rear chamber 15 liters

front chamber 0.5 liters

here is the lot and the expansion details.

 



Thanks for this. Very helpful. I'll get AJ horn too and have a play.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Timber_MG Quote  Post ReplyReply Direct Link To This Post Posted: 28 September 2004 at 3:58pm
A normal A4 sheet is 80grams per squre meter. That means that a 530 square centimetre cone would weigh in at 4.3 grams. The moving mass includes things such as a voice coil and partly the suspension elements in addition to the cone weight. I'd go with the weight of 53 grams (which is fairly light).

Their compression drivers are even more "reasonably" priced but sound absolutely beutiful.
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