Best Material for Cabinets - More or Less Resonance

[aggienader08]

Hello all!

I'm new to the HT scene and this is my first post on htguide.com! I'm planning on building my first set of speakers (L&R 3.5 way floor standing & 3 way center channel - all vented) and I don't want to try and accomplish something like this going in way over my head.

I guess my first question is: Should I use MDF for the cabinets or use real pine or something similar? I've heard multiple sources of which I'm not sure I can trust that real wood resonates too much and that's why most cabs are made with MDF board. The musician in me says to use real #1 grade pine and let those puppies resonate all they can, but I don't want something that sounds like crap.

Any suggestions?

for my design I'm using the same drivers and components for the crossovers in this design:

http://www.zaphaudio.com/ZDT3.5.html

Thank you to David for somewhat addressing my question and landing me here.

[jeff_free69]

Almost everyone uses MDF. Building a quality HT speaker is quite a bit different from a Fender Twin - you definitely DON'T want it to resonate at all. It will muck up your bass performance. Internal bracing is usually used too. Its a very good performer and relatively cheap

Just be aware that MDF makes a very fine powdery dust when cut; it seems to float everywhere, so do it outside if you can.

A very high quality ply can be pretty good too.

[ThomasW]

Use a man-made material, MDF, HDF, or 13 layer Baltic Birch ply if you can afford it

[Bear]

Use a man-made material, MDF, HDF, or 13 layer Baltic Birch ply if you can afford it

I agree on the BB rec. Baltic Birch is both more expensive and requires better tools, generally, but when viewed from the overall budget, it should be easily affordable from the right suppliers when put into the context of the rest of the budget (e.g., a 5'x5' sheet of 18mm B/BB is $46 from Houston Hardwoods, which is comparable to a single good quality woofer).

[Brian Kingsbury]

All the previous posts are spot on. Some people on this board and in hi end audio are also using LBL (Layered Bamboo Laminate) because it has a neat look and is about as non-resonant as you can find.

I noticed you said you're using the ZRT3.5 design/crossover but didn't mention if you were using the cabinet layout. If you don't intend to stick with the original design be aware that the speakers have different responses to a different cabinets and might require a new crossover if you change dimensions/volume. The low end bass response is tuned to the precise cabinet size and port and the mid/tweeter crossover is very sensitive to the width of the front panel the speaker. Look up diffraction for a better explanation.

If you still have questions, there's plenty of answers already on this forum. Go look 'em up!

[ClosetSciFiGeek]

I have built small speakers (<0.75^3ft) out of hardwoods like Maple and Cherry, but larger speakers or subwoofers I build out of 3/4" or 1" MDF. My main speakers are ZDT3.5's made from 3/4" MDF as Zaph specified. If you build those make sure you buy some extra resistors as I have found(as Zaph alludes to) that the ND20 is a little bit on the hot side so I padded the tweeter with the largest value of resistance that Zaph specifies in his Optional tweeter level adjustments. MDF does make quite a mess. If you have the means recommend a dust collector hooked up to your table saw. It has made a world of difference in my garage.

[parodielin]

I agree on the BB rec. Baltic Birch is both more expensive and requires better tools, generally, but when viewed from the overall budget, it should be easily affordable from the right suppliers when put into the context of the rest of the budget (e.g., a 5'x5' sheet of 18mm B/BB is $46 from Houston Hardwoods, which is comparable to a single good quality woofer).

$46 for 5'x5 is an excellent price. The cheapest in my area (Washington Metro) is like $65.

[Bear]

$46 for 5'x5 is an excellent price. The cheapest in my area (Washington Metro) is like $65.

I suspect you can beat $65 with a bit of digging. The prices change constantly, and finding a volume distributor locally who turns over the stock is key. It took me a fair bit of searching, but I've now got two local suppliers who aren't either Rockler or Woodcraft. Also, the $46 is by no means the best pricing I've seen, so there are good deals out there if you look hard enough.

[aggienader08]

Thanks a lot all for the excellent and much needed advice. I haven't tried this yet, but to answer your question about using the crossover design: I didn't know that the crossover design would need to be tweaked to sound properly in another cabinet. Thanks for informing me about that before I got started. Does anyone have any links or resources that would help me out if I get in a jam with what crossover would be better to use with my cabinet design?

As you can tell, I am def. a noob at this, but very eager to learn.

[Saurav]

Does anyone have any links or resources that would help me out if I get in a jam with what crossover would be better to use with my cabinet design?

You would have to design a new one, and it would be safe to say that it would take months / years of designing crossovers before you'd accomplish anything as good as John's work. The best option would be to stick with the cabinet design. Some cosmetic changes may be OK as long as they don't impact the important dimensions. If you post your ideas on this forum, someone will probably tell you what is or isn't safe to change.

This might help:

http://sites.google.com/site/undefinition/diy-mfaq

Make sure you read Part 2. That's more directly related to your questions.

[aggienader08]

You would have to design a new one, and it would be safe to say that it would take months / years of designing crossovers before you'd accomplish anything as good as John's work. The best option would be to stick with the cabinet design. Some cosmetic changes may be OK as long as they don't impact the important dimensions. If you post your ideas on this forum, someone will probably tell you what is or isn't safe to change.

This might help:

http://sites.google.com/site/undefinition/diy-mfaq

Make sure you read Part 2. That's more directly related to your questions.

Thanks Saurav!

[Bear]

Thanks a lot all for the excellent and much needed advice. I haven't tried this yet, but to answer your question about using the crossover design: I didn't know that the crossover design would need to be tweaked to sound properly in another cabinet. Thanks for informing me about that before I got started. Does anyone have any links or resources that would help me out if I get in a jam with what crossover would be better to use with my cabinet design?

As you can tell, I am def. a noob at this, but very eager to learn.

By the way, with a handle like "Aggie Nader '08", I suspect you might be reasonably close to either the Houston or Austin groups of HTGuide folk.

[JonP]

Good info all around....

To underline a few things from above, the native resonance of various materials usually isn't as big a deal as the way you end up building with it, i.e. if you use thicker rather than thinner, and do proper bracing and damping inside. Stiffer stuff helps, but good bracing can go a long way even with "lesser" stuff.

The width primarily, and to a lesser extent the height, of the front baffle (front face of the box) has an acoustic effect on the drivers that is compensated for in the crossover. So, that width is a part of the design, it's "programmed" in to the crossover response. Also, the positioning of the drivers on that front baffle. If you build a box that shares the same width and driver placement, and is somewhat close in length, it should work well without needing redesign of the crossover.

I should add that volume of the box is also a part of the picture, but more for overall bass tuning, and optimum response of the woofer. This can be played with some more lattitude, but it's best to keep close to the original design goals.

So, by following these guidelines, you get a picture of what you can change without a problem, if you want to customize, when building your own box.

[CBerg]

LBL seems to be a popular yet relatively expensive and somewhat hard to find. I have no affiliation whatsoever other than being a customer at this particular vendor but they have LBL I had not previously seen... I would almost think it would be scarry in regards to kickback on a table saw but would likely make an amazingly inert baffle.

http://www.crosscuthardwoods.com/Countertops/count_index.html#Bamboo

I asked them pricing and it was about 275 for a 96x25.5, but can't remember which one that was for.

[wettou]

LBL seems to be a popular yet relatively expensive and somewhat hard to find. I have no affiliation whatsoever other than being a customer at this particular vendor but they have LBL I had not previously seen... I would almost think it would be scarry in regards to kickback on a table saw but would likely make an amazingly inert baffle.

http://www.crosscuthardwoods.com/Countertops/count_index.html#Bamboo

I asked them pricing and it was about 275 for a 96x25.5, but can't remember which one that was for.

Cool:T I love wood

[Hank]

I asked them pricing and it was about 275 for a 96x25.5, but can't remember which one that was for.

8O For $275, it better be wrapped in gold foil! :bluezoned:

[Bear]

8O For $275, it better be wrapped in gold foil! :bluezoned:

The local Plyboo distributor here wanted ~$200, but for a full 4'x8' 0.75" sheet.

[fbov]

...My main speakers are ZDT3.5's ... If you build those make sure you buy some extra resistors as I have found(as Zaph alludes to) that the ND20 is a little bit on the hot side so I padded the tweeter with the largest value of resistance that Zaph specifies in his Optional tweeter level adjustments. ...

(emphasis added)

...to answer your question about using the crossover design: I didn't know that the crossover design would need to be tweaked to sound properly in another cabinet. Thanks for informing me about that before I got started. Does anyone have any links or resources that would help me out if I get in a jam with what crossover would be better to use with my cabinet design?
...

We've got to keep things in context...

A prior maker of a kit (ZDT3.5s here) is telling you about a documented tweak the designer has suggested that makes for a better listening experience in some room environments. This is hardly getting you involved in crossover design.

Any good designer will periodically check for things that affect the end product. Variations among production runs are one thing that changes over time. You will sometimes see tweaks recommended when this occurs.

Also, any good builder (this is you) will want a degree of flexibility in your finished product. No designer (save you) knows what room you'll put these in, and the room has a huge effect, especially at the extremes. "Padding the tweeter" with series or parallel resistors allows you to match tweeter level to that of the the other drivers in your listening room.

In many cases, a new person simply will not hear some of the things that experienced listeners and builders may tweak as standard procedure. Build them, learn from the build but also from listening to them, see if you hear the things the tweaks affect and go after the ones that you can hear!

A hot tweeter is one that's hard to ignore, but in an accoustically dead room, it may not be hot...

HAve fun,
Frank

[aggienader08]

By the way, with a handle like "Aggie Nader '08", I suspect you might be reasonably close to either the Houston or Austin groups of HTGuide folk.

Actually I am in North Texas, Fort Worth to be exact! I did graduate from Texas A&M Univ. in '08. I guess regionally I would be in the Dallas/Fort Worth group if there is one.

[aggienader08]

(emphasis added)

We've got to keep things in context...

A prior maker of a kit (ZDT3.5s here) is telling you about a documented tweak the designer has suggested that makes for a better listening experience in some room environments. This is hardly getting you involved in crossover design.

Any good designer will periodically check for things that affect the end product. Variations among production runs are one thing that changes over time. You will sometimes see tweaks recommended when this occurs.

Also, any good builder (this is you) will want a degree of flexibility in your finished product. No designer (save you) knows what room you'll put these in, and the room has a huge effect, especially at the extremes. "Padding the tweeter" with series or parallel resistors allows you to match tweeter level to that of the the other drivers in your listening room.

In many cases, a new person simply will not hear some of the things that experienced listeners and builders may tweak as standard procedure. Build them, learn from the build but also from listening to them, see if you hear the things the tweaks affect and go after the ones that you can hear!

A hot tweeter is one that's hard to ignore, but in an accoustically dead room, it may not be hot...

HAve fun,
Frank

Thank you Frank. I appreciate it.

[victoon]

If you want accuracy, which is what ZDT3.5 designed for, then you should avoid cabinet resonance. Here is my two cents. correct me if I am wrong.
As a matter of fact, you can not reduce resonance per se. all you can do is change the resonant frequency of the cabinet, making it less likely to be excited. Whether or not a cabinet wall will resonant is affected by at least three things:
1. At what frequency the recorded material has the most energy (or bursts of energy). It’s often mid range and bass.
2. the resonant frequency of the walls
3. internal dimensions of the cabinet, which affects the standing waves in the cabinet.

So 1 is fixed. So we need to manipulate 2 and 3 to avoid the cabinet wall resonant. Generally bracing break the panels to smaller pieces thus increase the resonant frequency. However, comment practice of doubling the wall thickness is not as effective because while stiffness of the wall is increased, so does the weight, which lower the resonant frequency (because more energy is stored in the wall, imagine if you attached weights to the center of the wall but not increased the thickness). For 3, non-parallel walls and internal deflectors both reduce standing waves, thus breaking up the internal acoustic energy.

Given the above, a material that is light and stiff is preferable acoustically. Among common choices, BB ply is the king as it’s super stiff (both along and across the veneer grain) and not heavy. But it’s most likely not flat, has voids, and easy to tearout. Cheap plywood has pine veneer cores, which makes them less stiff but also lighter. Their quality is often not as good as BB ply though. Then there is the MDF, heavy and flexy, but fairly good acoustically, especially when well braced. What made it so commonly used in the commercial speakers is it’s consistency and easy to work with. MDF dust is a really issue for us diyers though. Particle board is similar to MDF but lighter. Living Voice Avatar uses them. I don’t see many problems with solid wood sonically, but they do suffer from inconsistency (such as nuts), lower stiffness across the grain than along the grain, and less (?) expansion along the grain than across the grain from temperature and humidity changes. Pine being a porous softwood, I can’t imagine it being suitable for a full size tower speaker.

[Bear]

If you want accuracy, which is what ZDT3.5 designed for, then you should avoid cabinet resonance. Here is my two cents. correct me if I am wrong.
As a matter of fact, you can not reduce resonance per se. all you can do is change the resonant frequency of the cabinet, making it less likely to be excited. Whether or not a cabinet wall will resonant is affected by at least three things:
1. At what frequency the recorded material has the most energy (or bursts of energy). It’s often mid range and bass.
2. the resonant frequency of the walls
3. internal dimensions of the cabinet, which affects the standing waves in the cabinet.

So 1 is fixed. So we need to manipulate 2 and 3 to avoid the cabinet wall resonant. Generally bracing break the panels to smaller pieces thus increase the resonant frequency. However, comment practice of doubling the wall thickness is not as effective because while stiffness of the wall is increased, so does the weight, which lower the resonant frequency (because more energy is stored in the wall, imagine if you attached weights to the center of the wall but not increased the thickness). For 3, non-parallel walls and internal deflectors both reduce standing waves, thus breaking up the internal acoustic energy.

Given the above, a material that is light and stiff is preferable acoustically. Among common choices, BB ply is the king as it’s super stiff (both along and across the veneer grain) and not heavy. But it’s most likely not flat, has voids, and easy to tearout. Cheap plywood has pine veneer cores, which makes them less stiff but also lighter. Their quality is often not as good as BB ply though. Then there is the MDF, heavy and flexy, but fairly good acoustically, especially when well braced. What made it so commonly used in the commercial speakers is it’s consistency and easy to work with. MDF dust is a really issue for us diyers though. Particle board is similar to MDF but lighter. Living Voice Avatar uses them. I don’t see many problems with solid wood sonically, but they do suffer from inconsistency (such as nuts), lower stiffness across the grain than along the grain, and less (?) expansion along the grain than across the grain from temperature and humidity changes. Pine being a porous softwood, I can’t imagine it being suitable for a full size tower speaker.

Resonance is just that. As a result, it has both amplitude and frequency. Most of your remediation techniques will affect both aspects to one degree or another. Bracing is a primary way of driving the frequency higher, while making the walls thicker is the primary way of lowering the amplitude when it does resonate. You can't ever get rid of cabinet resonance, but you can pretty easily make it practically irrelevant with a little extra work.

This is one reason I like the "translam" concept so much since thick walls with great bracing are almost part of the technique.

[JonMarsh]

Resonance is just that. As a result, it has both amplitude and frequency. Most of your remediation techniques will affect both aspects to one degree or another. Bracing is a primary way of driving the frequency higher, while making the walls thicker is the primary way of lowering the amplitude when it does resonate. You can't ever get rid of cabinet resonance, but you can pretty easily make it practically irrelevant with a little extra work.

This is one reason I like the "translam" concept so much since thick walls with great bracing are almost part of the technique.

What he said... +1 :T

[Hank]

Amen!
+2

[ClosetSciFiGeek]

Great discussion about bracing, but doesn't Zaph's "as built" ZDT3.5 design already have enough bracing?

[victoon]

Great discussion about bracing, but doesn't Zaph's "as built" ZDT3.5 design already have enough bracing?

I think so. the only thing I added to my zdt3.5s are bracing in the middle of the back panel. I also used many screws to make a stronger joint between the back panel and the sides. and the reason I made the back panel removable instead of the baffle is that the baffle will be subjected to greater vibration force. So I think a glued on baffle should offer theoretically better performance.