3L设计漫话 [复制链接]

原帖由 olive13381 于 2009-10-1 18:15:00 发表 如此DX，期待更多量产精品！

都是个案，量产？量产等同破产，罢了。

原帖由 天神 于 2009-10-1 17:59:00 发表 很强啊，3L哥，近来喝什么好茶了？

云南茶算玩透了，维持关注，遇到合心水的收点，兴趣转回安溪茶。
还有，转玩咖啡~~~

不错

原帖由 3L-AUDIO 于 2009-9-30 1:24:00 发表 这对Classic Boy“驾世仔”书架箱完成于2005年秋，专门为Jsming兄而作，世上仅此一对。 中低音单元亦为本人设计，高音单元为SCAN-SPEAK D2905／950000。 [img]http://www.3l-aud

喇叭线要从电感中间穿过去，绝招？

没那么玄，方便拍照而尔。

BASS-REFLEX·低音反射式，密闭箱中附加声管的声箱，容积设计与密闭箱一样。

附加声管的截面积Sv，取值与声管的Fb，单元的Sd及单元的Xmax有关。

Sv有最小值要求，低于最小值，结果是灾难性的......

表达式 Sv≥K·Fb·Xmax·Sd

別问我要表达式中K的值，那是我用血汗和青春换回来的，我非GC主义者......


天书Loudspeaker Design Cookbook 7th editon BY Vance Dickason

声管计算




上图，dV为附加声管的直径，Vd为最大线性位移体积=Xmax·Sd.


表达式 Sv≥K·Fb·Xmax·Sd，与上图的式2可转换。

范例

SEAS DIY KITS Mimir



http://www.seas.no/index.php?opt ... w&id=210&Itemid=202


http://www.seas.no/images/storie ... eet/mimir_plans.pdf

Mimir    


Named after Mimir , a primal god of Norse mythology who was renowned for his knowledge and wisdom, we present
a new high-end two-way speaker kit.The Mimir  consist of an 18 cm long throw woofer with a coated paper cone - CA18RNX , and a 27 mm coated fabric tweeter - 27TDFC .

  
Enclosure and stuffing

The Mimir loudspeaker is based on a standard 14 litre vented cabinet that is available assembled and finsihed at some DIY loudspeaker shops. This cabinet was chosen to give people an easy start to building a loudspeaker. Ask your local loudspeaker dealer if he can help you obtain this, if your not thinking of building it yourself. The important thing to remember when you are building this, is to keep the baffle width and internal volume of the original enclosure. Adding braces to stiffen the cabinet is a good tip for the advanced builder to take the loudspeaker just a little bit further.

The amount of stuffing and port tuning is based on measurements and extensive listening. The cabinet is filled with 100 g of Acousto-Q. The stuffing is distributed evenly in the box, but kept away from the port opening to allow free movement of air. This to ensure that the airflow noise stays as low as possible. The port length is 20 cm including the flanged end and the inner diameter is 5 cm. This gives a port tuning of 42Hz providing a smooth low frequency roll-off.

  
Drive units

The woofer used in this system is the SEAS CA18RNX . This is a long throw 18 cm woofer with a coated paper cone. The classical coated paper cone gives a smooth extended frequency response with a controlled roll off. The large magnet system gives good transient response, and the bumped back plate together with the very long, and light weight copper clad aluminum voice coil allow for extreme coil excursion with low distortion. The extremely stiff and stable injection moulded metal basket, keeps the critical components in perfect alignment. Large windows in the basket both above and below the spider reduce sound reflection, air flow noise and cavity resonance to a minimum.

The tweeter is the SEAS 27TDFC . This is a 27 mm High Definition precoated fabric dome tweeter with a wide, soft polymer surround. The dome and surround materials give high consistency and excellent stability against variations in air humidity. The voice coil is wound on an aluminum voice coil former with adequate ventilating holes to eliminate noise from internal air flow. The voice coil is immersed in low viscosity magnetic fuid, for high power handling capacity and simplifed crossover design. A stiff and stable rear chamber with optimal acoustic damping allows 27TDFC to be used with moderately low crossover frequencies. The chassis is precision moulded from glass fibre reinforced plastic, and its front design offers optimum radiation conditions. For detailed technical parameters on the drive units see the data sheets.


Crossover

The crossover is designed in LspCAD from IJData, with the objective to obtain a simple design without sacrifcing the overall quality. Driver response and impedance were measured with the drivers mounted in the box at 1 metre distance 15 degrees off the tweeter axis in an anechoic room. This reference point was used in the design to minimize the influence of baffle edge diffraction. By measuring the drivers at the same point it is easy to simulate the summation of and phase response between the drivers. The crossover was developed empirically, without confinement to the traditional textbook filter formulas.

The drivers should be in phase at the crossover frequency, and the sum should be flat when both drivers are at -6dB relative to the pass band level. Now the inevitable vertical off-axis cancellation, which is always present with the use of non-coincident drivers, is at least outside the listening axis (tweeter axis). To accomplish the design goals it was necessary to use a 2nd order electrical filter for the high pass section, with an “l-pad” for attenuation because of the different sensitivities of the drivers. The low pass section was realised with a 2nd order electrical filter and a baffe-step compensator consisting of a parallel connection of an inductor and a resistor in series with the driver, thus providing a flat frequency response. The crossover schematics is shown in figure 2.




Measurements

Anechoic free field response at 1 meter, 15 degrees off tweeter axis, measured at 2.83V.
Impedance measured at 2V.



As seen in the figure the average sensitivity is 84dB and the response lies within ± 2dB.  The black curve shows the response with the tweeter connected with opposite polarity. In this curve we look for a deep and symmetrical notch around the crossover frequency, which indicates that the drivers are in phase in the crossover region. Here the notch is more than 25dB deep, and that confirms that this system has a very good phase response. The blue and green curves show respectively the response of the woofer and the tweeter.

The 2nd order electrical crossover combinedwith the natural roll-off of the drivers gives a 4th order acoustical Linkwitz-Riley slope. The crossover frequency is 2.2 kHz, high enough for the tweeter to operate inside its limits, even at high amplitudes, and low enough so that the woofer doesn’t become too directional, and thus providing a smooth power respons. The off-axis respons of the Mimir is shown below.



This figure shows that the power response is very smooth throughout the whole frequency range, and the controlled off-axis roll off of the tweeter.
  

The next figure shows the 2nd and 3rd order harmonic distortion with an output of 96dB at 1m. The overall distortion is very low and without any peaks that might become noticeable. This makes the reproduced music very clean and without coloration.

范例

ZaphAudio ZA-SR71

http://www.zaphaudio.com/SR71.html

详细内容看官自己去看。




ZaphAudio ZA-SR71箱体


Enclosure

This system is designed specifically to fit in Madisound's MD14 enclosure with their baffle pre-cut for Seas 7" woofers and standard series 1" tweeters. Dimensions are provided for those who would like to build their own however. The fit and finish of the Madisound enclosures is first rate. The "TD" terminal cup and Precision 2" flared port fit perfectly. I did however place a couple of hardwood dowels across the sides to reduce vibration. Any piece of wood or two will do this job fine.

I love "TD" cup terminals. It's not because I support bi-wiring - that's a complete waste of two amplifier channels. Basically, when you're initially hooking up your drivers and testing your crossover, you can wire each driver right to a terminal and have the crossovers external for easy tweaking. Then when things are finalized, you can put the tweeter and woofer filters on separate boards and wire each one to a terminal. Later on, if you ever have a problem such as a blown component or loose solder connection, you can listen to each individually to help isolate it. You can even reverse the phase externally at the terminals to see if you hooked up a driver wrong.

The tweeter countersink is multi-purpose. It's designed to fit a few of Seas newer tweeters with 6mm flanges. For those using 104mm tweeters with 3.5mm thick flanges like the one in this design, a shim or spacer of some sort will be required to bring the front of the flange up to level with the baffle. If you don't do this, there will be some diffraction issues with the exposed ridge. There are a lot of ways to deal with this, such as weatherstripping tape or some rolled sealing caulk. I used 4mm hobby foam from a craft store, cut to a circle with a little hand made wood and razor blade jig.

It would be important to note that I did not round over or chamfer the inside of the woofer hole. I do chamfer the inside on designs with smaller woofers that need a reduction in airflow resistance, but the Seas 7" woofers are well ventilated. All response plots for the woofer as shown in this design are with the precut baffle as supplied. This is partially a concession to those who would like to build the kit but do not own a router. Just be aware that I would not have not have let it go if the effects were obvious and audible. For those who buy the precut baffle and do have a router with a chamfer bit, go ahead and chamfer the inside radius. It's certainly not going to hurt the design, and will likely result in a tiny bit smoother response on the top end of the woofer's working range due to a small reduction in the inside edge reflection back through the cone.

I used Whispermat 3 layer WM2 on the back and bottom and 2 layer WM1 on other surfaces. There are a lot of options for damping, take your pick. Just be careful of carpet padding and generic egg crate foam, as they may not have optimal acoustic properties. If your damping/absorption material is thin, double up on the back and bottom. Note that you can't go very thick up on the top because the inside port flare needs some clearance.

The 2" flared port comes in three pieces - the two end flares and a lengthening middle section. To reach my goal 44 Hz tuning, the middle section needs to be cut to 2-1/4" long. If you'd like to try a higher tuning, eliminating the middle section will result in a 50 Hz tuning. I don't recommend going any lower than 44 Hz because the port length would begin to have restricted airflow against the tweeter and front baffle.

节录部分文字

SEAS DIY KITS Mimir ， ZaphAudio ZA-SR71用同一型号高音单元。





H1189-06 27TDFC


SEAS DIY KITS Mimir 的中低音单元 H1215-08 CA18RNX




Specifications



*IEC 268-5 SEAS reserves the right to change technical data



ZaphAudio ZA-SR71 的中低音单元 H1456-08 ER18RNX




Specifications



*IEC 268-5 SEAS reserves the right to change technical data


SR71的结构基本与Mimir一样，容积也极接近，以发布时间断定，SR71的箱体设计源自Mimir。

两个中低音单元的Sd及单元的Xmax是一样的，Mimir的声管的Fb为42Hz，SR71的声管的Fb为44Hz。

两者的声管的截面积Sv最小值要求基本相同。

很巧，两者均使用Φ50mm声管。

很不幸，两者的Sv取值远低于最小值要求，各位看官可据天书Loudspeaker Design Cookbook 7th editon自行核算。

较之过去的老型号，SEAS现产品目录上的型号，Xmax大幅提高。换种讲法，SEAS现产品多为长冲程设计。

设计低音反射式箱体时要充分考虑反射管的截面积，否则大功率驱动时反射管会有气流声，低频响应混乱。

范例

Classic Boy 2011

http://www.3l-audio.com/bbs/read.php?tid=610






中低音单元 H1488-08 L16RNX



L16RNX is a 5” High Fidelity woofer with an injection moulded
metal chassis, intended for bass reflex and transmission line designs.

Stiff, yet light aluminum cone and low loss rubber surround show
no sign of the familiar 500-1500 Hz cone edge resonance and distortion
assosiated with soft cones.

A bumped back plate in the magnet system, together with the very long and light weight copper clad aluminum voice coil, allow extreme coil excursion with low distortion.

A heavy copper ring below the T-shaped pole piece reduces non linear and modulation distortion.

Extremely stiff and stable injection moulded metal basket, keeps the critical components in perfect alignment. Large windows in the basket both above and below the spider reduce sound reflection, air flow noise and cavity resonance to a minimum.

This driver use Seas SpiderRing® technology.

Frequency response



The frequency responses above show measured free field sound pressure in 0, 30, and 60 degrees angle using a 28L closed box. Input 2.83 Vrms, microphone distance 0.5m, normalized to SPL 1m.The dotted line is a calculated response in infinite baffle based on the parameters given for this specific driver. The impedance is measured in free air without baffle using a 2V sine signal.

Specifications



*IEC 268-5 SEAS reserves the right to change technical data.



Classic Boy 2011三声管的截面积Sv →27.2 平方厘米，比Mimir的声管的截面积还大。

强箱得顶.

Classic Boy 2011
中低音单元 H1488-08 L16RNX


H1488-08 L16RNX
L16RNX is a 5” High Fidelity woofer with an injection moulded
metal chassis, intended for bass reflex and transmission line designs.
Stiff, yet light aluminum cone and low loss rubber surround show
no sign of the familiar 500-1500 Hz cone edge resonance and distortion
assosiated with soft cones.
A bumped back plate in the magnet system, together with the very long and light weight copper clad aluminum voice coil, allow extreme coil excursion with low distortion.
A heavy copper ring below the T-shaped pole piece reduces non linear and modulation distortion.
Extremely stiff and stable injection moulded metal basket, keeps the critical components in perfect alignment. Large windows in the basket both above and below the spider reduce sound reflection, air flow noise and cavity resonance to a minimum.
This driver use Seas SpiderRing® technology.
Frequency response

The frequency responses above show measured free field sound pressure in 0, 30, and 60 degrees angle using a 28L closed box. Input 2.83 Vrms, microphone distance 0.5m, normalized to SPL 1m.The dotted line is a calculated response in infinite baffle based on the parameters given for this specific driver. The impedance is measured in free air without baffle using a 2V sine signal.
Specifications

*IEC 268-5 SEAS reserves the right to change technical data

高音单元 E0006-06 T25CF001



The T25CF001 is a 25mm fabric dome with moderately high efficiency.
An optimally shaped dome and a wide SONOMEX surround, both manufactured by
SEAS, ensure excellent performance and consistency.
Low viscosity magnetic fluid which provides excellent cooling while maintaining a low resonance frequency.
6 mm solid metal front plate with a slight loading characteristic which ensures
linear frequency response, and a stiff and stable connection to the cabinet.
A substantial injection-moulded rear chamber, with complex internal shape and
reinforcing ribs, which eliminate unwanted chamber resonances and reflections.
A double magnet system which increases sensitivity and provides better control of the voice coil.
This system also reduces the magnetic stray fields, making the T25CF001 an ideal choice in high end A/V applications.

Frequency response

The frequency responses above show measured free field sound pressure in 0, 30, and 60 degrees, mounted in a 0.6m by 0.8m baffle. Input 2.83 Vrms, microphone distance 0.5m, normalized to SPL 1m. The impedance is measured without baffle using a 2V sine signal.

Specifications

*IEC 268-5, via High Pass Butterworth Filter 2500Hz 12 dB/oct. SEAS reserves the right to change technical data.

藕前一对书架箱设计



2005年底的事，六年了......

而之前的Classic Boy箱体，是上世纪末所作，唉......

关于音箱设计，要唠叨的太多太多......


有兴趣玩玩音箱设计的看官，可look下天书：

Loudspeaker Design Cookbook 7th editon BY Vance Dickason





不过，别以为天书在手，好箱即有，没那么简单......