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Small Speakers for 5 channel single ended amp

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#42
I think I am going to do just that. the form factor is nice, everything i know about tube amps should like that impedance graph, and the design of the box looks easy. One question tho, looking through cabinet designs, all of them have what looks to be a brace butted up firmly against the magnet of the speaker. and that always have holes in it.

Two questions just out of curiosity. do the holes serve any purpose other then allowing air to pass through? and secondly, the brace is just to hold the speaker still? or is it to transmit sound?
 
#43
ryuji said:
...what looks to be a brace butted up firmly against the magnet of the speaker. and that always have holes in it.

Two questions just out of curiosity. do the holes serve any purpose other then allowing air to pass through? and secondly, the brace is just to hold the speaker still? or is it to transmit sound?
Click to expand...

The baffle -- because of the hole(s) in it, is the weakest panel in a box. The way most boxes are built, it is asked to handle all of the reactive energy from the driver> The holey brace distributes the energy to at least 3 (all stronger) panels as well, so no one panel has to deal with al the energy. Less energy to excite resonances. It also braces the panels it connects to.

The holes are primarily to allow air-flow, but also reduce the volume. They also make the braces resonances higher in frequency and, of most of the way across the air space of the box, complicate the distances across that spece (complicating the standing wave structures in the air space,

dave
 
#45
bought a set of FR88eX speakers, the wood i can pick up from local lowes. Glue for all pieces i assume? or do you use nails/screws too. i assume for the fabric i just need to pick up some thick wool type material from fabric store. i think the purpose is just to break up the resonant sound waves just like the baffle does?
 
#47
I copied the magnet brace idea from the guru, Dave.

Yes - wood glue all around - and with a small hole in the front for the driver you don't have much chance to 'fix' things inside the box later. For example, you may prefer to use a terminal cup instead of the simple terminal bolts I used since in my case I had to carefully solder the wires to he insides of the terminals before gluing on the back of the speaker. I like to glue everything - solid and less susceptible to movement at the joint from humidity changes in the environment.

You need to line it with something that will absorb the high frequencies, so thick felt is ideal because it's reasonably dense without using up a lot of volume. Glue the felt to the inside of all the wooden pieces.

One thing about these drivers - at least mine - they were too 'cheap' to include gaskets for mounting to the enclosure so I had to find something suitable and cut my own.
 
#48
ryuji said:
bought a set of FR88eX speakers, the wood i can pick up from local lowes. Glue for all pieces i assume? or do you use nails/screws too. i assume for the fabric i just need to pick up some thick wool type material from fabric store. i think the purpose is just to break up the resonant sound waves just like the baffle does?
Click to expand...

A "true believer" would not cover the drivers with a cloth grill. But us skeptics think the cloth does very little and think it is really just for cosmetics. But if you really think it might effect the sound you can buy real speaker grill cloth for about $15 per yard

What I do depends on the intended use. For guitar speakers I use a sturdy steel grill that would survive a good kick, a flying chair or a roll down a flight of stairs. For home stereo speakers I don't cover the drivers unless they might be quite low to the ground.

Glue is good enough for home stereo speakers that have internal braces. For guitar speakers, I'll use cleat blocks inside all glued corners. These are 3/4" square strips of hardwood screwed and glued to the inside corners with two #10 or #12 screws every 3 inches.

I've done some destructive tests where I built a glued joint then bash it apart with a sledge hammer. Glued MDF fails at the glue line. Using hardwood plywood with oak cleat blocks, the join never fails, the plywood splinters off first. Assuming your home speakers will never be sledge hammered the edge glued MDF is good enough as long as it is braced to prevent flexing, if it flexes at all glued MDF comes apart.

Nails are useful aid while clamping the parts. They keep the parts together but add almost zero strength to the final product. I use small nails twice as long as the material thickness. Counter sink the heads and fill the holes.
 
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