Good Morning. what is the best material to line the box, acoustic sponge, fiberglass or something else? thanks
I'd pick acoustic melamine foam, like Basotect. Excellent acoustic properties, long-term stable and easier to apply than mineral wools. That said, mineral wools offer bang for the buck, almost no material absorbs sound better. But I wouldn't apply them in an open system like yours anymore nowadays.
Nice enclosures by the way!
Nice enclosures by the way!
There is little point in lining walls with anything, considering one wants to damp air resonances.
If it was my project, I'd line the box with glued or stapled acoustic felt or rubbery stuff to deal with panel resonances AND foam:
The theory of reflex is you leave the box volume relatively untouched by damping. It relies on free air flow to work. And am interested in the outcome.
Many ways to skin a cat:
The bottom half of your speaker is just a plinth for a 30L reflex. But am full of admiration for your effort.
my box has 1200x250x350 on the outside. it should stay after reinforcements (19mm) with + - 60 l, tuned to 30Hz. I use the whole box. I still have to drill a lot of holes. ��
Eggcrate foam like that does very little at bass frequencies.Kicks in around 1-3kHz in the upper midrage. Where it gets near 1/4 wavelength.
In closed box you can use very heavy stuffing like fibreglass. Can up the effective volume 20%. But most of the white BAF fluffy stuff we put in speakers doesn't do much at all. BAF is used in air conditioning as an air filter too.
In closed box you can use very heavy stuffing like fibreglass. Can up the effective volume 20%. But most of the white BAF fluffy stuff we put in speakers doesn't do much at all. BAF is used in air conditioning as an air filter too.
Acoustic Foam Pyramid Panels
– SoundAssured
I use these foam pyramids, it is not the same as the egg crate foam. These are designed for things like recording studio walls, etc. They do a good job except for very deep bass obviously.
Noise Reduction Coefficient Ratings (NRC)
Range 1" Pyramid 2" Pyramid 3" Pyramid 4" Pyramid Bass Traps
125 Hz 0.14 0.19 0.24 0.28 1.18
250 Hz 0.13 0.22 0.29 0.39 1.27
500 Hz 0.31 0.45 0.55 0.74 1.26
1000 Hz 0.43 0.55 0.56 0.69 1.19
2000 Hz 0.46 0.6 0.61 0.75 1.16
4000 Hz 0.54 0.76 0.85 0.96 1.16
Overall 0.35 0.45 0.5 0.65 1.2
sorry, I couldn't get this table to copy and paste correctly, just use space bar or tab over...these work even at 125 Hz; better at higher frequencies but they do help. I use them a few inches back from the driver basket and frame. 4 inch size for larger drivers and larger box sizes. They help keep back waves from going back through the cone by absorbing instead of reflecting. Behind the foam I use poly' fill. I line the internal box surfaces with felt for damping. All 3 techniques at the same time, they all do different things.
– SoundAssured
I use these foam pyramids, it is not the same as the egg crate foam. These are designed for things like recording studio walls, etc. They do a good job except for very deep bass obviously.
Noise Reduction Coefficient Ratings (NRC)
Range 1" Pyramid 2" Pyramid 3" Pyramid 4" Pyramid Bass Traps
125 Hz 0.14 0.19 0.24 0.28 1.18
250 Hz 0.13 0.22 0.29 0.39 1.27
500 Hz 0.31 0.45 0.55 0.74 1.26
1000 Hz 0.43 0.55 0.56 0.69 1.19
2000 Hz 0.46 0.6 0.61 0.75 1.16
4000 Hz 0.54 0.76 0.85 0.96 1.16
Overall 0.35 0.45 0.5 0.65 1.2
sorry, I couldn't get this table to copy and paste correctly, just use space bar or tab over...these work even at 125 Hz; better at higher frequencies but they do help. I use them a few inches back from the driver basket and frame. 4 inch size for larger drivers and larger box sizes. They help keep back waves from going back through the cone by absorbing instead of reflecting. Behind the foam I use poly' fill. I line the internal box surfaces with felt for damping. All 3 techniques at the same time, they all do different things.