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Mar 12, 2009

Of Speaker Ports & Grills

Posted by The Advanced Audiophile

Stuffing The Port

Thirsty Castle Pembroke
speaker
Some advocate stuffing a ported speaker with drinking straws. Don't do this. As another throwback to something I used to engage in, in my earlier days of tweakdom, I tried stuffing the port for the Clydes (see below) with straws. Beginners try this and are seduced by the clear and significant increase in resolution. Which brings about increased detail etc., and even subjectively, volume.  But what may be less obvious to them, is it breaks down the integrity of the proper reproduction of timbre and tone. This is the fabric of the music. You do not want to mess this up.  So don't. Resist the temptation of trying to impress your friends with high fidelity upgrades that cost pennies. Straws are for drinking, not hifi. Blocking the port from free exchange of air with any kind of filter is going to have a negative effect.



Grilled or BBQ'ed?: Testing Speaker Grill Materials (Foam vs. Cloth)

Guess what? Like everything else I come across in my audio research, speaker grills are also part of the Belt phenomenon. Bear with me. It'll take a while for me to explain what that means...

The short answer is, in practical terms, different speaker grill types and materials have an effect on your person, equally as they would on the sound you hear from their use. This all started because I needed new grills for old Castle speakers. Most of the old Castles originally used sculpted foam grills, that have by now, disintegrated. As the original company no longer exists, replacing the grills with originals is impossible. After researching this, I settled upon using reticulated foam for a replacement. But this proved very difficult to find in the appropriate size and colour needed, in anything less than industrial quantitites. So I decided to build the necessary grills, from wood and speaker grill cloth.  Just as a measure to be certain this was the right way to go, I decided to test the two types of grills on the smaller Castle Clyde speakers. One test used an old pair of grills I made for the PSB speakers; out of wood and black pantyhose. To compare against these grills, I used a piece of green reticulated foam, about one quarter inch thick, sold as a liner for fruits and vegetables, in the refridgerator crisper. It didn't quite cover the front of the speaker, but it did blanket both drivers, so fine.

The reason I say grills are part of the Belt phenomenon, is because before listening, I felt a difference each time I hooked up the different grills to the front baffle of the speaker, using two bits of blue-tak. From the feeling given by the PSB cloth grills, I knew this wasn't going to wow me. And, it didn't. Surprisingly, the green reticulated foam won out in this test. More than that, I felt that when I switched to the DIY grill, the sound was way less musical, less involving, and I was much less interested in listening to music, in this case. I ignored what both were doing in terms of frequency response, and the like, in order to focus on these more important aspects. And then things got complicated....

I reproduced the same test of DIY cloth grill vs. foam on the larger Castle Pembrokes, and this time, a reverse finding occurred. The foam ruined the sound in comparison, while the DIY grills were the ones that presented a beautiful musical focus, and tuneful bass melodies. So I took the two types of grills back to the smaller Clydes, and re-tested them. The foam was definitely not doing good things this time. Then, I got "serious".  I started checking the direction it was being placed, and ensuring that the blue tak was being installed exactly as it was on the Pembrokes.  Now, things started making more sense, as the foam grill was properly installed, and sounding much better! One last test with the grills back on the Pembroke, and that helped confirm things.


Speaker Grill Designs: Conclusions:

I'm really not sure I can say yet whether cloth or reticulated foam is better for speaker grills, as, well... it's tricky. But I feel that the details are probably more important than the materials and construction. Meaning, the way its installed and the way its adhered, can make more of a difference than the natural differences occurring between the two different types of grill design. "Theoretically", the foam should be superior, as there are no hard edges creating boundary effects. But it's never that simple in reality. Both types can sound acceptable, if care is paid to the details. If there's one thing I can conclude from all this, it's that speaker grill design is extremely important. These tests showed that a speaker grill can make or break the sound, and put it in the dumpster in fact, if you don't take this aspect of your system seriously, and make sure that things are right.

Most, predictably, will attribute the differences in grills to diffraction, and other known conventional acoustic effects. But the differences heard between the grills will be heard on headphones, as they would on speakers. You can't attribute that to acoustic effects. Another aspect that remains evident here as well, with both grills, is the importance of how the grills are positioned. This is why I "tested" all positions, to find the optimum for each, before making any conclusions.

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