Building SMV5- Newbie questions

[nullstring]

I talked to my dad this weekend about making speaker cabinets, and he seems to be up for it.

I've decided upon the SMV5, but I have a few questions to get me started.
Zaph|Audio - ZMV5 - MCM / Vifa 5" System

1. My dad has particle board that is covered in Melamine resin. Is this plastic covering going to affect the sound? Would covering it in Sonic Barrier damping as Zaph does negate any affect?
2. Some resistors aren't marked on the madisound BOM. What wattage should those resistors be? R2,R7,R10. (And brand?)
3. How exact do the dimensions need to be? Do I need to worry about the port and tuning and such if I am a little off? or will it not matter too much?
4. How do you mount the crossover inside the enclosure?
5. Because the 2ohm Eagle Resistors are unavailable, I plan on paralleling 6ohm and 3ohm Eagle resistors.
6. Any other feedback is welcome.

Thanks,
nullstring

[nullstring]

I don't really like bumping things...
but, here goes.

If any one has any feedback, it would be greatly appreciated.

[gfiandy]

Hi,

R2,R7,R10. are the internal resistances of the inductors so you do not need to purchase them. They are due to the resistance of the inductor wire.

The melamine covering will probably help as it will form a basic constrained layer damping (although it may not look great). Using the sonic barrier damping will undoubtly improve it further.

Dimensions should be close but a few mm either way will not affect the alingnement significantly but cm will. The port should also be within a few mm in terms of length, the diamater needs to much closer as its effect is more significant try to be within 1mm if at all possible.

The box needs to be securely glued together with no air leaks, this is really important. It sometime helps to think what it would take to make it water tight as people can often imaging water leaks more eaisly than air leaks.

Use gaskets behind the drive units so air dosn't leak past them. Some thin foam is good for this. Others have reported that free thin mouse mats cut to the right shape work well. (I have not tried this) or window draft excluder works well (I have used this)

Parrallel resistors should be no problem.

I would mount crossover with spacers and self tapping screws into the cabinet. Put it in the bottom if it is accessible and large enough as this is likely to be the best damped part of the cabinet so the least vibration will be transfered to the crossover. You may want to put some foam behind the crossover to damp it slightly as it looks quite large. (looking at the picture on Madisounds site)

Best of luck,
Andy

[ScottTracy]

I absolutely agree with everything gfiandy says. I'm sure the particle board is fine but you should use some form of damping too. There are cheaper options (such as floor tiles) if you don't want to use sonic barrier.

Dimensions don't have to be to the nearest 1/1000th of a mm and there's some freedom in where to place the port. The width and height are more important because they influence diffraction as well as bass tuning. Be sure to get as big a round-over as you can around the front edge to smooth diffraction too.

Good luck.

ScottT

[nullstring]

Originally Posted by gfiandy

R2,R7,R10. are the internal resistances of the inductors so you do not need to purchase them. They are due to the resistance of the inductor wire.

I am pretty sure I knew that at one point.. hmm
Oh, I feel silly, it says so right on the schematic.

Originally Posted by gfiandy

The melamine covering will probably help as it will form a basic constrained layer damping (although it may not look great). Using the sonic barrier damping will undoubtly improve it further.

Thats interesting. I would've thought that the plastic wouldn't have been the best thing for the audio to bounce off of.

Originally Posted by gfiandy

Dimensions should be close but a few mm either way will not affect the alingnement significantly but cm will. The port should also be within a few mm in terms of length, the diamater needs to much closer as its effect is more significant try to be within 1mm if at all possible.

Thanks for this clarification. we'll have to try to be close.

Originally Posted by gfiandy

The box needs to be securely glued together with no air leaks, this is really important. It sometime helps to think what it would take to make it water tight as people can often imaging water leaks more eaisly than air leaks.

Does it need to be glued together?
I was thinking about using screws and then caulking the corners.

Originally Posted by gfiandy

Use gaskets behind the drive units so air dosn't leak past them. Some thin foam is good for this. Others have reported that free thin mouse mats cut to the right shape work well. (I have not tried this) or window draft excluder works well (I have used this)


I would mount crossover with spacers and self tapping screws into the cabinet. Put it in the bottom if it is accessible and large enough as this is likely to be the best damped part of the cabinet so the least vibration will be transfered to the crossover. You may want to put some foam behind the crossover to damp it slightly as it looks quite large. (looking at the picture on Madisounds site)

I don't believe I understand the gasket information, but I'll have to do more research.


Thanks again.
I appreciate it.

[nullstring]

Originally Posted by ScottTracy

I absolutely agree with everything gfiandy says. I'm sure the particle board is fine but you should use some form of damping too. There are cheaper options (such as floor tiles) if you don't want to use sonic barrier.

I'll have to do more research on damping alternatives.
Floor tiles seems like an odd one. Floor tiles made out of what?

[gfiandy]

Hi to achieve some damping just about anything that has a different resonance to the particle board firmly stuck to the box will help. So any self adheisive tile like the cheap stick on ones would do. You may find you Dad has some lying arround I know I do.

To reduce reflections in the box use foam to line the walls of the box, for best results about 2cm thick. Ensure the foam does not obstruct the port or the path to the port from the back of the bass driver. The foam has two effects it absorbs teh reflections in the box so they are reduced more quickly and as the sound wave passes through the foam it slows down as this means it takes longer to hit the wall it effectively increases the size of the box a bit. Zaph will have taken this into account when fitting the sonic barrier damping and so if your not going tof fit it something like foam will help to match the response.

Screws and caulking is OK so long as you are sure you seal it.

The gasket goes behind the speaker driver between it and the box to seal any gaps that there might be and stop air leaking out between the speaker drive and the box.

Regards,
Andy