土兄请进

fwi297

[em09][em09]

土八路

以下是引用fwi297在2005-4-3 19:42:00的发言：
靠！都不知道自己看到哪页了。

八路的2A3开声了没有？

目前，在J版指导下进行改进！
[em06][em06]

fwi297

靠！都不知道自己看到哪页了。

八路的2A3开声了没有？

土八路

Juliet

准备开工D1了吗？[em11]

饿狼

土八路

我只能看动一点！[em02][em02]

文招

[em12]

Juliet

Compression Chambers
The size of the compression chambers depends on the drivers and the frequency range you want from the horn. For a rear-loaded bass driver such as in a Lowther horn, the front compression chamber volume tends to vary from about 2.5 liters to 4 or more liters. Of course, a Lowther horn does not have a rear compression chamber (because of the radiation from the front of the driver).
A number of different formulas exist for compression chambers, and any one of them may not give the best size for your application. These formulas should be considered a starting point. One formula for a compression chamber volume:
<img src="attachments/dvbbs/2005-3/2005330211843581.gif" border="0" onload="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onmouseover="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.style.cursor=\'hand\'; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onclick="if(!this.resized) {return true;} else {window.open(\'attachments/dvbbs/2005-3/2005330211843581.gif\');}" onmousewheel="return imgzoom(this);" alt="" />
VB is the back volume (volume of compression chamber next to horn throat, the front chamber in the diagram on the previous page)
Vas, Fs, and Qts are standard driver parameters
Fc is the lower cutoff frequency of the horn flare (I think)
Another formula comes from the paper by D.B. Keele, Jr., Low-Frequency Horn Design Using Thiele/Small Driver Parameters from the AES (see References) which is a simple form first derived by Klipsch in 1941:
<img src="attachments/dvbbs/2005-3/2005330211910394.gif" border="0" onload="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onmouseover="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.style.cursor=\'hand\'; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onclick="if(!this.resized) {return true;} else {window.open(\'attachments/dvbbs/2005-3/2005330211910394.gif\');}" onmousewheel="return imgzoom(this);" alt="" />
VB is the back volume (volume of compression chamber)
ST is the throat area of the horn
FC is the horn cutoff frequency
c is the velocity of sound
Front and rear compression chambers are calculated differently in the Leach model.
David McBean's program (see below) can show the effects of different size front and rear chambers on the reactance and SPL generated by a horn.

土八路

Juliet

Coupling the driver to the horn
Now, before we attempt to stuff the whole thing into a box, some attention needs to be directed to the volume of air (the cavity) between the driver's back side and the horn throat. We'd like to keep higher frequencies out of the horn. A good thumb rule is to let the horn play 3-4 octavesii or less. One should therefore dimension the cavity in such a way that it will act as a low-pass filter with an upper cut-off freq. 3-4 times the horn's fc. Also, the upper cut-off should be set at a frequency where the horn's length equals an odd multiply of the wavelength (because the horn is loaded from the back of the driver, 180 degrees out of phase). This is to avoid a canceling of the frequencies around the upper cut-off. Calculate the volume of the cavity (Vc) using this formula:
Vc = (C * Throat area) / (2 * PI * upper cut-off freq.) iii
In the 'BIG FUN' horn, this wasn't considered, because I wanted to leave plenty of space available for experimenting with different upper cut-off frequencies and damping of the cavity. However, I would recommend DIY constructors to take advantage of this math.

Juliet

Carfrae号角不是指数的。
Some people are using the Tractrix expansion in bass horns for Lowther drivers, for example the Big Fun horn and the commercial Carfrae.

Fanny

还是8路比较眼尖！！我继续潜水！！！

土八路

以下是引用Fanny在2005-3-30 15:46:00的发言：
大家应该鼓励的嘛！！HOHO！！！

[em11][em11][em11]

Fanny

大家应该鼓励的嘛！！HOHO！！！

文招

近来真多无聊之人[em10][em10][em10][em10]
这样的玩笑不好玩[em11][em11][em11]

土八路

以下是引用大钳子在2005-3-30 13:08:00的发言：
请各位大哥多多关照！[em11]

[em11][em11]

大钳子

请各位大哥多多关照！[em11]

土八路

步步高DV－927K，有时也用先锋PD X707，秋叶原信号线，宝韵192喇叭线[em02][em02]

Juliet

忘记问8路兄您现在用啥音源的啊？咸菜呢？<img src="attachments/dvbbs/2005-3/200533013036110.gif" border="0" onload="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onmouseover="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.style.cursor=\'hand\'; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onclick="if(!this.resized) {return true;} else {window.open(\'attachments/dvbbs/2005-3/200533013036110.gif\');}" onmousewheel="return imgzoom(this);" alt="" />