The range of textiles that are offered as speaker cloth or acoustic fabric is almost impossible to grasp, particularly on the Internet. But what makes a true acoustic cloth? Here’s a short quality checklist:
1. Maximum sound transparency
Acoustic information, i.e. sound waves, must be able to penetrate the material as freely and unchanged as possible. Unsuitable fabrics will impair the sound—especially the high and high-mid frequencies—because sound waves are absorbed or diffused. That’s why simple air permeability is no sufficient criterion for the quality of a speaker fabric or acoustic cloth.
Only lab measurements will reveal what a specific fabric is actually suitable for. A direct comparison of measuring results generated with different types of speaker fabric reveals that even a double-layer of standard Acoustic Cloth from Akustikstoff.com is more sound transparent than other polyester or linen fabrics.
By the way: Strictly speaking, fabrics like molleton, which are meant to absorb sound rather than let it through, are not an acoustic fabric but an insulating material.
2. Sufficient opacity
A good acoustic fabric bridges the physical gap between sound transparency and opaqueness. It will usually be developed exactly for this purpose and produced on state-of-the-art machines, which make an appropriate material structure possible. After all, the fabric is used as speaker fabric, as cover fabric for acoustic elements such as absorbers, diffusers, and bass traps, for AV furniture and instrument amplifiers such as guitar amps, in the car hi-fi sector, and last but not least for cladding in shop fitting, exhibition stand construction, and interior design. Of course, there are physical limits to opaqueness. You can find some more details on this topic here.
Acoustic cloth requires some tension to ensure an even surface of the cabinet front. That’s why it needs to offer exactly the right amount of horizontal and vertical elasticity. Any fabric that is too elastic will warp during processing and crinkle or buckle after a while. If it’s too rigid, on the other hand, workability will suffer, which can also cause crinkles. Standard Acoustic Cloth from Akustikstoff.com can even be easily stretched around several edges and finally stapled to the frame, as this photo of a model for the speaker cover of a high-end loudspeaker shows. With the topic of stapling we get straight to the next point:
Speaker fabric is often stretched around hard edges and stapled (watch this tutorial to see how it works), and high-quality acoustic fabrics are durable enough to stand this procedure without laddering or tearing. The weight of a certain speaker cloth usually is a good hint at its stability: Fabrics that weigh between 90 and 140 grams per square metre consist of a single layer of very thin yarn—which puts them close to nylons. No wonder they are similarly sensitive. Akustikstoff.com offers only robust double jersey with a weight of 180 grams or higher per square metre. The particularly rugged PA-Type Acoustic Cloth, which is equipped with a special protective net on the front, even reaches 550 grams without any loss in sound transparency.
5. Even structure
High-quality acoustic fabric is characterised by its even structure. It’s quite easy to distinguish good material from cheap qualities at first sight in direct comparison. Simply have a look at the image: The crinkled fabric on the left is an imported fabric from somewhere in East Asia. It is offered at prices of about 8-10 euros per square meter by various stores on the Internet and on Ebay without any information about the origin and the manufacturer of the fabric. On the right there’s a photo of the more expensive proprietary fabric made in Germany by Akustikstoff.com–of course taken from the same angle and from the same distance.
6. Flawless workmanship
Acoustic cloth is a rather delicate fabric, so only high-quality raw materials and perfect processing in all steps can prevent quality defects. And as always, careful processing and consistent, fastidious quality control have their price.
An example of common quality defects are ugly traces of worn needles. Actually, this should be an absolute no-no for any supplier. Such fabrics are clearly seconds that any professional customer will reject. Unfortunately, such defects are quite common with low-cost no-name speaker fabrics such as the budget cloth in our example. Taking a look at the fabric at backlight conditions clearly shows the sloppy work. If you attach some importance to detail in the realm of your hi-fi and AV equipment, you will most probably not be pleased with such speaker fabric.
Uneven colouring due to the use of non-mixed, uncontaminated yarn is another quality flaw that can often be observed with cheap speaker cloth. It is particularly noticeable with dark colours, when somewhat lighter stripes cause an irregular surface. That’s why acoustic fabrics from Akustikstoff.com are exclusively made from high-quality, white polyester yarns.
7. HSE and social responsibility in production
Azo dyes, formaldehyde, heavy metals … There’s quite a number of hazardous chemicals that may be hidden in textiles, and the use of some of them is still not sufficiently regulated by law. Even worse, the main reason for the use of these questionable substances, which are still often found in imported textiles, is to ensure cheapest possible production processes. Questions about potential risks for humans and the environment and about the working conditions under which these fabrics are produced are simply ignored. At first glance, the end product may seem “inexpensive”, but closer inspection often brings a different picture to light.
That’s why all fabrics in the product range made by Akustikstoff.com are certified according to the OekoTex 100 standard. This long-established standard contributes to high and effective product safety. The test criteria and limit values often go well beyond the national and international requirements, extensive product controls and regular company audits ensure compliance with the strict guidelines.