Bottles as bass traps?

[cdwitmer]

I have been reading an article from a 1972 Japanese audiophile magazine about using bottles of various sizes and shapes to absorb frequencies in the low midrange and upper bass region. The author was primarily doing tests to show how their use inside an enclosure could help precisely eliminate a speaker's peaks and dips and thus create a flatter frequency response, but he also mentioned that judicious placement of empty bottles around a room could also improve the sound of the bass. (Perhaps that explains why my system always sounds better after I've been drinking.)

Does anyone have any experience with this approach? And are there any good information sources available in English?

Thanks!

Chris

[joecarrow]

An empty bottle is nothing more than a helmholtz resonator. I've heard big wine bottles with impressively low (for a bottle) fundamentals, so this could work.

A while ago I saw some architectural windows that used helmholtz resonators to cut down on outdoor noise while allowing fresh air into a room. I couldn't find a link just now, but I did find this: http://www.trenwyth.com/aw_faq.asp

As you can see, they don't need to be bottles. If you google for helmholtz resonators, you should find many resources. The math is simple enough that if you're able to approximate the volume of air in the body of the bottle and the volume of air in just the neck of the bottle, then you should be able to calculate something very close to the resonant frequency of the bottle.

[Patrick Bateman]

I have been reading an article from a 1972 Japanese audiophile magazine about using bottles of various sizes and shapes to absorb frequencies in the low midrange and upper bass region. The author was primarily doing tests to show how their use inside an enclosure could help precisely eliminate a speaker's peaks and dips and thus create a flatter frequency response, but he also mentioned that judicious placement of empty bottles around a room could also improve the sound of the bass. (Perhaps that explains why my system always sounds better after I've been drinking.)

Does anyone have any experience with this approach? And are there any good information sources available in English?

Thanks!

Chris

Earl Geddes covers that in his home theater book. You can buy it at www.gedlee.com.

[Dennis H]

The problem with Helmholtz resonators as bass traps is the very small area of the "ports." Setting aside the bottle thing, say you park the equivalent of a tube sub in your corner with the sub's port absorbing bass. Well if the "sub" has a 10" port, that 10" round tube will absorb all the bass that hits it at a certain frequency. But that port is TINY compared to the surface area of the corner where you place it. Effect -- almost none. Stuff the corner with fiberglass equal to the volume of the resonator and you'll have a lot better bass trap -- big surface area and it works at all frequencies.