PLYWOOD vs MDF For Speaker Building - Tests Show Surprising Results

to do the testing i built a box that's around the size of the typical bookshelf speaker and i made it mostly from construction gary plywood to make this as simple as possible i left one side open so that i can switch out the panels i'm going to test i also added a brace to the box except i kept it short and it won't be touching the panel that i'm going to test then i cut four panels from three different types of plywood and a piece of mdf and i thought it'd be interesting to see how much they weigh i started with the lightest which is actually the oak plywood this has thin oak veneer on the faces and a poplar wood core the next lightest is the pine plywood and i've used that in several projects including the listening room i built in the basement it has five layers and they're all pine next is the balti birch plywood and it's quite a bit heavier it has nine layers and they're all hardwood birch in fact and finally the heavyweight champ is the mdf no surprise there i'm starting with the baltic birch plywood and i'm running a sweep from 30 hertz right up to 2000 hertz and i'm doing that four times for consistency and then i'll take those four measurements and average them and that's what you're looking at here and one thing i notice with all of these measurements is that there's not much variation above around 270 hertz i also picked one of those measurements and created a waterfall plot and what that shows is how long the panel continues the ring after the tone is played for maximum stability i clamp the box down to my very heavy workbench and i'll keep it from moving around and the next panel that i'm testing is the oak veneer plywood the accelerometer that i'm using to measure the vibrations is fastened to the center of the panel with very thin very strong double-sided tape [Music] and here are the results for that panel plus the average of the four measurements also here's the average from the baltic birch to compare it to overlaid it's the orange trace and then we can take the waterfall and we can compare it to the baltic birch plywood and we can see there's a little bit more energy down low but it doesn't hang around very long [Music] next up the pine plywood and this actually surprised me i didn't think it would look this good but it does and here's the average again and here it is compared to the baltic birch overlaid again and compare it also to the oak plywood and when we look at the waterfall that looks good next to the baltic birch as well [Music] last one is the mdf and once again i was surprised it actually looks a lot like the oak plywood with a very similar response here's the average from the oak plywood overlaid it's the green trace this time and looking at the waterfall and comparing it to the oak there doesn't seem to be a huge advantage it does look like the mdf has a slightly better decay time though and that makes sense because mdf is supposed to have some internal damping [Music] and then just go a little bit further with the mdf panel still attached i flipped the box over and measured that side in between the end and the brace so you'll have a smaller span and that's showing a little bit higher peaking up around 1k and that's not really unexpected the smaller the panel is the higher the resonance will be and when we look at the waterfall plot and compare it to the pine panel because this panel is pine the same stuff after all you can see that has an improvement in the decay time down low taking a further still again i removed the mdf put some stuffing inside the box and then put the mdf panel back on and ran the four sweeps again and that's what you see right here [Music] once again i averaged that out and here it is with the original measurement from the mdf panel without having any stuffing in the box and you can see that the stuffing made a notable difference especially up higher and that carries through to the waterfall plot as well so where does all that leave us well you can take the results any way you want you're free to look back through everything you know pause the video to have a closer look you know examine everything and draw your own conclusions from it but for me it kind of confirms what i was thinking all along and that's that it really doesn't make that much of a difference what material you use to build your speakers with as long as it's structurally sound material as in it has a certain amount of stiffness and it has a certain amount of mass it'll be perfectly fine because i don't think that there's any thing here that i've seen in these measurements that's actually audible especially not in a small speaker like this the other conclusion that i drew from it is that okay my original understanding of this like when i first got into speaker building the idea was to put damping inside the speaker as in something to stop the box from ringing okay and that can be done a couple ways you can use stuffing or you can say put some kind of membrane onto the panels so that it you know damps the panels some kind of rubberish membrane okay damping material however there was a new idea that came about that said that bracing by adding more bracing you will drive the residence up to the point where you won't be able to hear it so that kind of took over i think in a lot of areas and this doesn't debunk that i can't say anything here is conclusive but me measuring the panel the brace panel on the other side of the box shows that it did drive the resonance up but it looks like it was at a much higher level so therefore a better chance that you would actually hear it so that is not a good thing and what the stuffing or the damping actually pointed out was how that made a difference you could actually see an improvement over the majority of the frequency range that i tested all of the panels that i made were half inch thick i did find a piece of three quarter inch baltic birch and i put it on the box and that's what's on here right now and i ran some sweeps with that and i saw a very marginal improvement over the half inch but just marginal it wasn't even worth me you know going to the trouble of capturing it to put in the video because you really wouldn't be able to see a difference it looked almost identical to the half inch but just slightly better as in you know very slight okay so i guess the takeaway from this is to not stress over those things don't get hung up on oh i have to have that specific type of material mdf is the only thing that's worth using although i hate working with it because i mean even that oak plywood was almost identical to the mdf so if you want an oak plywood exterior box and you're worried about the core material of plywood you don't want to use that because it's unsuitable go ahead because they test almost identical now as for whether you can hear the difference okay because there's this kind of conception of things that okay this is the measurements the measurements using a microphone or accelerometer they don't hear you know you can hear the difference well i would dispute that right the only thing you can do if you're into this kind of thing is build a box out of all all the materials you're interested in testing and actually listen to them but try to be objective and try to realize that so many factors affect how you hear and what you hear you know your mood even your blood pressure to some extent will affect how you know things sound so have to be extremely objective in your critical listening

Channel: John Heisz - Speakers and Audio Projects

Views: 231,558

Keywords: woodworking, how to, diy, make, maker, making, i build it, john heisz

Id: 7dwAnFAMi34

Length: 9min 30sec (570 seconds)

Published: Sun Sep 26 2021