Author Topic: Flatter speaker frequency response  (Read 1138 times)

Offline pnoboy

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Flatter speaker frequency response
« on: February 07, 2016, 01:08:55 PM »
For some reason, Rhodes pianos seem more sensitive than guitars to uneven frequency response.  Closed-box cabinets can suffer from various resonances unless they are stuffed.  Ordinary polyester fiber fill is an excellent stuffing material, and it is cheap and easily available.  A stuffing ratio of about 1 lb of fiberfill to 1 cubic foot of cabinet volume is a good place to start.  I have been having some difficulty adjusting my Rhodes for optimum sound, even with the use of an equalizer.  Playing the piano through headphones showed that the issues were not the piano, but the speaker.  I already was using a good quality 12" speaker, so I opened the cabinet, and found it had little stuffing.  For a princely sum of $6.99, I bought 24 ounces of fiber fill at a local fabric store, distributed it carefully in the cabinet, and voila, problem solved. 

Polyester fiber fill does two good things in a speaker cabinet.  At low, i.e., bass, frequencies it makes the cabinet look bigger to the speaker by slowing down the speed of sound.  Given that many manufacturers like to make the cabinet smaller than it should for both cost and sales appeal, this effect is usually desirable.  At higher frequencies, i.e., midrange and treble, the fiber fill acts as damping, and prevents standing waves from occurring in the cabinet.  If you're dissatisfied with the sound of your amp, before spending lots of money on new equipment, stuffing a closed-box speaker cabinet is a cheap and quick experiment to try.

Offline pianotuner steveo

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Re: Flatter speaker frequency response
« Reply #1 on: February 07, 2016, 05:18:49 PM »
Is it better than old fashioned fiberglass insulation or just cheaper and easier to use? (no itch factor)
1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 200A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...

Offline The Real MC

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Re: Flatter speaker frequency response
« Reply #2 on: February 07, 2016, 06:42:06 PM »
It depends on the R value of the insulation.  The lower the value, the less dense it is.

Offline rhodesjuzz

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Re: Flatter speaker frequency response
« Reply #3 on: February 08, 2016, 01:04:40 AM »
Thanks for the tip!  I have similar issues with my cabinet when cranking up the volume.

--Roy
1976 Rhodes Suitcase 73 <effects loop || EHX Holy Grail Nano>
Line 6 midi keys
Scarbee Mark I, A-200 and Classic EP-88S

Offline pnoboy

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Re: Flatter speaker frequency response
« Reply #4 on: February 08, 2016, 06:23:31 AM »
Is it better than old fashioned fiberglass insulation or just cheaper and easier to use? (no itch factor)

Fiberglass is just as good, but I hate to use it because of its itchiness, and because its fibers can break and get into the air and down into the lungs.

Offline pianotuner steveo

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Re: Flatter speaker frequency response
« Reply #5 on: February 08, 2016, 08:09:50 AM »
Good to know. I never thought of this.
1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 200A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...