mrMDF and Birch PLY question

[sebna]

Hi All,

My first post.

I am about to get subwoofer cabinets fabricated for me and fabricator recommended MR MDF.

I will most likely, instead of priming and painting, fabric wrap them using adhesive Velcro glued to construction.

My questions are:

1. Health wise, is it safe to leave MR MDF exposed without painting it? I assume MR MDF is made with some higher does of chemicals and I know that some MR / WR MDF is not meant for internal use because of that. Or does not make it any difference painted or exposed? (I am thinking higher off-gassing over time etc. or off-gassing of more harmful substances used for MR treatment)

2. Which would be better material in your view PLY or MR MDF? I believe that Birch Ply will be lighter but I guess it uses same toxic substances to bond it's layers as it is used for (MR?) MDF bonding?

Thank you

 

[Sideways]

From the few speakers - including subs - that I've ever opened up, I think MRMDF is the preferred material of the commercial companies who will actually have the resources to have done proper testing of the product's acoustics.
MDF is a heavy, "dead" material better at damping vibration and avoiding resonance. And it's the sound that matters most, yes ?

MRMDF is more dense, more glue than cheap MDF. There are higher grades of MRMDF that are more dense and much more expensive that are preferred for quality built in cabinets. That's the stuff I'd want for speakers. Not even standard MRMDF.

 

[sebna]

From the few speakers - including subs - that I've ever opened up, I think MRMDF is the preferred material of the commercial companies who will actually have the resources to have done proper testing of the product's acoustics.
MDF is a heavy, "dead" material better at damping vibration and avoiding resonance. And it's the sound that matters most, yes ?

MRMDF is more dense, more glue than cheap MDF. There are higher grades of MRMDF that are more dense and much more expensive that are preferred for quality built in cabinets. That's the stuff I'd want for speakers. Not even standard MRMDF.

Thank you for getting back to me. That is great info.

What do you think about leaving it unpainted? (fabric wrapped)? Re off gassing etc.?

 

[porker]

Looking at a COSHH sheet for one of the manufacturers, the only real risk is the dust which means vacuum and face mask. In sheet form it doesn't appear to be a risk. This was Caberwood for reference.

 

[sebna]

Looking at a COSHH sheet for one of the manufacturers, the only real risk is the dust which means vacuum and face mask. In sheet form it doesn't appear to be a risk. This was Caberwood for reference.

I will reach out and see if I can get the brand and model so I can check the spec sheet if available.

 

[Agent_zed]

Off gassing is something that does concern me slightly but more so for everyday items. If you buy a new carpet, unless it's a natural material, you have a large volume of material that will be off gassing. New car smell! yeah that's because everything is new and off gassing. New chipboard flooring or Ikea wardrobe, oh yeah wood chip held together with glue with varying levels of formeldehyde.

Covering your speakers in another man made material is unlikely to help. Might slow the process down slightly?

As above though my understanding of the safety warnings is the manufacture process rather than the finished product. Where will the sub be stored? that will also have a bearing on it. If you are storing it in a garage it's not going to be such a problem. If its for a car then if you want to be safe just roll down the windows and clear the stale air for a few mins each time you drive for a few months.

I got some of these the other day https://www.jpleisure.co.uk/Vector_WS12_MK2.htm (although not subs) and they are birch plywood that is finished in a textured black paint. Not sure where you get this type of paint from but it could be an option?

I've also made my own valve guitar amp and cab and covered those in vinyl type material. Spray contact adhesive is the way to go with that.

 

[Ozi]

Would it be practicable to have the cabinets sit somewhere well ventilated for a month before assembly, if so that would get rid of the bulk of any nastiness coming off

 

[MF1000]

My sub cabinets for my lounge system are constructed from 30mm mdf with 18mm internal bracing. They are clad in 18mm yellow belau hardwood. Subs generate large internal forces from the volume of air moved by …in my case a 18” driver so the internal cruciform bracing is essential. My ported cabs including the drivers weigh around 150 Kg each.

 

[sebna]

My sub cabinets for my lounge system are constructed from 30mm mdf with 18mm internal bracing. They are clad in 18mm yellow belau hardwood. Subs generate large internal forces from the volume of air moved by …in my case a 18” driver so the internal cruciform bracing is essential. My ported cabs including the drivers weigh around 150 Kg each.

I am building 4x (sealed) Subwoofer 18" each, and the cabs will be made using only 18mm mrMDF with 36mm front wall. But they will not be driven hard as 4 will be sharing the load so in fact they will be barely doing anything.

I expect them to weigh around 35-40kg each, driver included (around 100l internal volume). But the drivers are very light at only 10kg each. Lovely BMS 18N862.

 

[MF1000]

Whilst 4 drivers will not work as hard …they will move large volumes of air in total. My cabs are 150 litres and go down to 18 Hz using Volt drivers which are bomb proof but £££££. I have an internal cruciform brace with an adjustable pad that supports the rear of the drive magnet too.

A sealed cabinet will definitely need substantial internal bracing to stop wall flexure which can lead to ‘muddy’ bass notes.

 

[sebna]

Whilst 4 drivers will not work as hard …they will move large volumes of air in total. My cabs are 150 litres and go down to 18 Hz using Volt drivers which are bomb proof but £££££. I have an internal cruciform brace with an adjustable pad that supports the rear of the drive magnet too.

A sealed cabinet will definitely need substantial internal bracing to stop wall flexure which can lead to ‘muddy’ bass notes.

They are certainly not the cheapest around

Never heard of them before. What was your reasoning to go for that particular one? Do you use one sub with it? Is it for movies or music primarily?

What do you think about such bracing (all walls and bracing will be 18mm mrMDF)?

 

[MF1000]

Here are some pics from my build …3 years ago.


Bare cabinet with bracing


Test fit of 100mm port pipe


Bracing after drilling out air holes and starting to line with d’dead sheet’


Test fit of the Volt driver


Rear magnet brace


Cabinet before fitting port outlet and balau cladding

Cabinet walls are 30mm mdf and 18mm bracing.