【空間處理探索系列】低頻陷阱

[Yeh捨]

小經驗是.
自家空間地板2/3是架高儲物(算是某程度空腔.)
天花板4/5是間照(準空腔)
其餘擺設算一般..
結果.50~60hz嚴重隆起.不砍掉簡直...聽.

曾設計完成使用的店家展示廳空間.
整個背牆3面全是所謂空腔.角料架空12cm釘12mm松木面板內全塞滿玻璃棉..
結果.一測..低~極低乾淨哪!
猝發響應好極了.
無怪劇院展示時.110dB轟炸也不會壓迫太重..

[chsiang]

小經驗是.
自家空間地板2/3是架高儲物(算是某程度空腔.)
天花板4/5是間照(準空腔)
其餘擺設算一般..
結果.50~60hz嚴重隆起.不砍掉簡直...聽.

曾設計完成使用的店家展示廳空間.
整個背牆3面全是所謂空腔.角料架空12cm釘12mm松木面板內全塞滿玻璃棉..
結果.一測..低~極低乾淨哪!
猝發響應好極了.
無怪劇院展示時.110dB轟炸也不會壓迫太重..

這個經驗是重點中的重點,

請教Yeh捨, 有試過把地板或天花板的空腔塞起來嗎? 效果如何?

[Yeh捨]

這個經驗是重點中的重點,

請教Yeh捨, 有試過把地板或天花板的空腔塞起來嗎? 效果如何?

沒有也不太可能去動裝潢了..
所以我最佩服裝潢好整個音響室之後.實聽或後來測量發現的確不夠優.整個打掉重新來過.:O.
通常木既成舟後.只能尋求其他方法改善.
上上圖物品面積頗大的.又有10cm厚..我猜低至接近120hz囉.

[chsiang]

有人要猜一下這個產品到多少頻率都還有1以上的吸音係數嗎?

長60英寸, 寬40英寸, 厚4英吋

沒有也不太可能去動裝潢了..
所以我最佩服裝潢好整個音響室之後.實聽或後來測量發現的確不夠優.整個打掉重新來過.:O.
通常木既成舟後.只能尋求其他方法改善.
上上圖物品面積頗大的.又有10cm厚..我猜低至接近120hz囉.

沒什麼人要猜 ;(

那只好公佈答案了



答案是到65Hz都還有吸收系數都還有1, 很可怕吧!

所謂的Type 2產品厚度增加0.25英吋, 到達4.25英吋, 更是在極低頻有很大的效果!

[chsiang]

沒什麼人要猜 ;(

那只好公佈答案了



答案是到65Hz都還有吸收系數都還有1, 很可怕吧!

所謂的Type 2產品厚度增加0.25英吋, 到達4.25英吋, 更是在極低頻有很大的效果!

請參考國外網友仿造這個設計概念自行打造的低頻陷阱的測量結果,

長寬高與RPG這個產品相近,

房間未加入低頻陷阱前



很亂的阿! 尤其是50Hz那附近......

用了之後,



真的是大幅改善, 也真的對極低頻的部分有很大的幫助

這個產品的原理我日後也會探討.......

[999369]

沒什麼人要猜 ;(

那只好公佈答案了



答案是到65Hz都還有吸收系數都還有1, 很可怕吧!

所謂的Type 2產品厚度增加0.25英吋, 到達4.25英吋, 更是在極低頻有很大的效果!

Type 1 Modex Plate shown above, for Type 2 click here.

Small rooms often exhibit poor low frequency response with significant emphasis at modal resonances. This is especially true when they are sonically well isolated, due to massive boundary construction. Porous or friction based surface absorption is ineffective at these modal frequencies because the air particle velocity near walls and corners is essentially zero, resulting in very low absorption efficiency. Many bass absorption products on the market today are in fact porous material based products that can not possibly meet the specifications that they claim. For these reasons, RPG developed its Modex™ product line and is extremely proud to introduce a new and unique addition to this line, called the Modex™ Plate. The Modex™ Plate technology was developed and patented by the Institute for Building Physics at the Fraunhofer Institute, and consists of a damped metal plate system. The Modex™ Plate offers broadband low frequency absorption effective down to 50Hz in a thickness of only 4 inches, and 35Hz in a thickness of only 4.25”. The Modex™ Plate has an attractive powder coated metal finish and can be surface mounted on walls or ceiling. Every now and then a new technology comes along that can change everything. You will be astounded at the transients and clarity of sound, once the Modex™ Plate removes all of the masking low frequency reverberation. Now you can absorb more bass in less space!
Technology
Sound (1) strikes the steel plate (2) which pistonically vibrates (3) against the porous absorption spring (4), mounted on a rigid backing (8). The porous absorption also damps plate bending modes (5) and absorbs higher frequencies which diffract around the plate (6) through a perforated (7) metal frame.
Surface or corner applied porous materials lose efficiency at low frequencies, because the particle velocity or air movement associated with these long wavelengths is low. In order to maintain efficiency at low frequencies, the Modex™ Plate consists of a damped metal plate system. While the velocity is low, the pressure is at a maximum near the boundary and it is this pressure that is exploited in a mass-spring manner offering absorption via three mechanisms. First, the metal plate provides pistonic absorption down to the lowest frequencies by vibrating against the “spring” of the porous backing. Second, the bending modes of the free-moving plate are heavily damped by the proprietary adhesive coupling with the porous backing which attenuates the lower mid-range frequencies. Lastly, mid-frequency sound waves diffract around the plate’s edges to be propagated and thus dissipated in the deep passive porous absorber layer. Together, these mechanisms offer the industry’s first truly efficient, broad bandwidth low frequency absorber with a shallow profile of only 4 inches.
Absorption
Many published low frequency absorption coefficients are misleading, because the accuracy of the absorption efficiency decreases frequencies below 100Hz in standard ISO 354 and ASTM 423 test chambers, due to inadequate diffusion and modal density. Therefore, additional testing has been carried out at the Fraunhofer Institute in large scale impedance tubes with a cross section of 1.6 x 1.2 m and a special approach monitoring the decay times of the lowest axial modes in a 5x4x3 m room, with and without the sample present on one of the opposing surfaces. You can trust these data to be reliable and accurate.

Installation
The Modex™ Plate is installed by attaching metal “L” brackets to the boundary surface and sliding the panel over and screwing to brackets. Panels should be installed at high pressure locations. In order of highest to lowest efficiency, this would be the intersection of three boundary surfaces, two boundary surfaces and on one boundary surface.
補上原网站全文~~~
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TYPE 1

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TYPE 2

[kee]

談到低頻陷阱，想問大家對於寬頻低頻陷阱與專注某各頻率的低頻陷阱的看法 （尤其小空間如 3m x 4m x 2.8m), 個人經驗以多個寬頻低頻陷阱取得較大得覆蓋面積似乎能給予較大得改善，尤其以總體而講。

[chsiang]

談到低頻陷阱，想問大家對於寬頻低頻陷阱與專注某各頻率的低頻陷阱的看法 （尤其小空間如 3m x 4m x 2.8m), 個人經驗以多個寬頻低頻陷阱取得較大得覆蓋面積似乎能給予較大得改善，尤其以總體而講。

我的經驗也是這樣,

從本版關於DRC實測的分享就能知道, 絕大多數的房間並非單一頻率(或是很窄的頻帶)有問題, 尤其是低頻, 變異實在太大,

先用寬頻解決大多數的問題, 再來針對特定頻率, 會有比較顯著的成果

[THXman]

略
從本版關於DRC實測的分享就能知道, 略

若鄙人沒看錯的話
僅DRC前座點聲頻測量.

[999369]

上任為版主我想展開一個計劃,

分門別類介紹各種空間處理的方式以及深入一點探討原理,

一來可以讓大家將產品對應到要處理的問題, 破除不肖廠商誇大不實的言論甚至造成反效果,

二來如果有心的人更可以DIY, 用最低的花費改善自己的空間.

這一系列的文章, 我想先從低頻陷阱開始.

因為低頻陷阱是最容易被誤解, 也是最容易用錯產生反效果的產品,

而且就低頻很重要的70Hz到200Hz這個區段, 即使是使用小喇叭應該也很少產品會宣稱發不出來的吧?:)

所以不見得小喇叭就能逃過低頻的摧殘~~~

我會從原理, 種類, 應用到自己的經驗來切入, 也希望各位先進, 朋友一起來分享經驗,

我說的不對的地方更要用力點出來, 或者是與經驗不合的地方都需要大家一起討論來釐清:):)

就讓我們開始吧!

低頻很重要的70Hz到200Hz這個區段 嚴格講該是中低頻段 請參考[80Hz-160Hz]