Ultra Light Weight Bass Cabinet

[Petebass]

Did you research foam materials other than polyester i.e. polyurethane, klegecell, etc? Is the 1-1/2" thickness a calculated parameter? Ever consider vaccum bagging?

Just trying to make a decision whether its worth it for me to try a little prototyping...

I used West systems as well. Every boat enthusiast I spoke to mentioned it by name, it's what Zac used. It wasn't the cheapest stuff but I though it was reasonably priced considering how easy it us to use and how well it sets. You can probably substitute it with any epoxy resin as long as it's compatible with the foam core.

The foam used is actually extruded polystyrene. Go to your local Home Depot and check out the price. Now check out the price of an equivalent sheet of Klegcell or Divinicell. Make sure someone who knows CPR is standing nearby though, you may need them Honestly the performance benefit is only small, but the price jump is enormous. If you MUST have panels than are thinner than 1 inch, then "maybe" it's worth considering higher performance cores.... but only for a while before you go back to XPS.

Seems to me like you're looking to save a buck on the resin but blow it unnecessarily on foam cores

 

[DukeLeJeune]

I have tried to measure the effects of that design (ports on the front and the back), but the problem is that the only theoretical effect the rear port will have is in close proximity to a wall, and once you do that, (at least for me), thats inside, and then the room comes in to play.

Hard to measure, but not too hard to describe. If you've ever experimented with subwoofer placement in a home audio system, you may have found that movements of a foot or less can make an audible difference. This is because how the bass source (subwoofer) interacts with room boundaries has been changed, and the resulting peak-and-dip pattern has been modified. I subscribe to the school of thought (for home audio) that says, the ideal is to use lots of bass sources distributed around the room so that each generates a different peak-and-dip pattern, and the sum of these dissimilar patterns will be smoother than any one of them alone. The frequency response variation is reduced, and (unlike EQ alone) the spatial variation is reduced as well.

I do believe that there is a small but worthwhile improvement in bass smoothness from spreading out your bass sources on a single home audio speaker in a small room like a living room, such as significantly displacing your ports relative to the woofer (or even relative to one another) in all three dimensions. However in a large room, where a live performance is more likely to take place, I suspect the effect is negligible as best.

Also, In my opinion (again, I'm trying to stay out of trouble here), it is not the fundamental tone of the bass note that is important, but rather the harmonics of that note that give it the quality that people like to hear. In my book, it's not the harmonics of the cabinet that you want, it's the harmonics of the instrument and strings.

Very much agree. When I was pushing the compact cab end of the envelope, my target was to still do justice to the first overtone of low-B, and that seems to be adequate... though a cab like yours that goes deeper is going to have a more satisfying low end, even before that ultrarigid enclosure comes into play.

 

[dhomer]

I'm well aware of the price of some of these materials.. Just wanted to know if the hard research was done, not so much on a price basis, but performance basis.. if there was a conscious, performance-based decision made on what components to use.. Sorta like the guy who asked why some of these other speaker brands weren't used.. Polystyrene.. yeah I knew that...lol... just don't use it w/polyester resin..

From my model boating days, I knew vaccum bagged carbon fiber was the lightest possible construction.. any advantages to doing that in this application??

 

[robthebassplaye]

I'm well aware of the price of some of these materials.. Just wanted to know if the hard research was done, not so much on a price basis, but performance basis.. if there was a conscious, performance-based decision made on what components to use.. Sorta like the guy who asked why some of these other speaker brands weren't used.. Polystyrene.. yeah I knew that...lol... just don't use it w/polyester resin..

From my model boating days, I knew vaccum bagged carbon fiber was the lightest possible construction.. any advantages to doing that in this application??

Hi There - these are not cheap to make. Of course, because I am "a little anal" I kept track of all of that. And, so I have attached my cost spreadsheet....

For me, it was absolutely a "cost is no object" kind of build, what is the best thing in the world I can make at any cost...

I know that doesnt fit everyones requirement, but that's where I started.

So, I attached a spreadsheet with the info on what I spent. Perhaps you can find or manufacture some of this for less, but I think for the average guy, this is probably what it will cost... It includes everything from Tyvex bunny suits (which suck to wear, but I would suggest that you do wear them, this material is not very friendly...) to the foam glue for the carpet... I think I captured most of the costs here...

I need to say upfront that this is not current and up to date, but it's close...

It's not a perfect design by any measure, the fiberglass and neo drivers do weigh less, but it's not a whole boatload less, but it is significant, and is actually difficult to justify from a cost perspective, in my mind (back to the question of would I do it again...).

Thats why I'm not sure if this kind of construction could ever be financially viable. But, I'll leave that to other folks on here to discuss...

Thanks!
Rob

 

[Petebass]

From my model boating days, I knew vaccum bagged carbon fiber was the lightest possible construction.. any advantages to doing that in this application??

The only disadvantage I can see is you'd have to do it in a minimum of 2 separate pieces, then join them together somehow. The current design is a monocoque and has no outer joints, and therefore no points of potential weakness.

You'd probably also have to use a mold with vacuum bagging. The people I spoke to tended to steer away from using molds with true rectangles as they don't easily come out from the mold. Their suggestions was to make the cab into a very slight trapezoid to help with this, but even then they were reluctant to recommend it. They also gave a distinct vibe that it's something a novice should work up to rather than dive straight into. Having built two mold-less cabs, I can see their point. Get down and dirty first, then start thinking about ways to "cheat".

 

[robthebassplaye]

Hello, again.. Obviously my questions aren't in the technical end, methinks you have that covered... but more how this was built.. I recognized the West System epoxy in the pics. I have used this before in my R/C model race boat days.. I'm just curious, since obviously you have thought long and hard about everything that went into this.. is there an advantage to using West Systems over other epoxy systems?? Did you research foam materials other than polyester i.e. polyurethane, klegecell, etc? Is the 1-1/2" thickness a calculated parameter? Ever consider vaccum bagging?

Just trying to make a decision whether its worth it for me to try a little prototyping...

I definately don't claim to have any serious knowledge about the differences in the epoxy systems. I have, however, read all of the info on the West systems web site, and it makes sense to me, so I feel comfortable using it.

But, honestly, I'm not comfortable saying it's better than anything else (only because I really don't know, and I don't want to endorse stuff ever...).

I am comfortable saying that I trust it, and that I trust the engineering behind it. Everything on the web site makes sense to me. Seems like they have their act together.

This can be dangerous stuff if used incorrectly, so keep that in mind! Like anything, if you are not properly prepared, you can get hurt...

Remember, in the ened, it's just Audio!

Rob

 

[robthebassplaye]

Hey Rob,

Looks like someone else posted the link. Welcome to Talkbass, by the way.

I have done some crossover modeling in LTSpice myself. Have you looked into using some subcircuit models for the speaker loads, rather than just using 8 ohm resistors? Also, did you measure frequency response on the actual baffle installed on your cab, or at least model baffle step and diffraction effects?

Nice build. I have a fair amount of experience working with composites for watersports toys, and if I ever bother to build any more DIY cabs I would prefer that sort of construction to wood by a large margin.

Hi! Really nice to talk with you... I can't belive that I am having the opportunity to correspond with such experienced folks such as yourself! This is awesome, to me. Thank you!!!

For me, and perhaps I have this wrong, but the xover is sort of the simple problem to fix on these builds. If it gets close, it's probably good enough (at least for us bass players). To me, thats not the thing that makes the biggest difference in these build.

But, why not make it perfect? It costs the same (pretty much), and takes the same amount of time to make (make it right or make it wrong, either way, you need to make it) - so let's do it right!!! I think you have a lot of experience here, so I definately want to get your input.

What would you suggest for this kind of build? Do you think the properties of the cabinet affect the crossover design? I have measured the cabinet and it's response, is there more data that would be valuable in deciding this?

I know that flies in the face of audio purists (I'm sort of one too - I bought Dahlquist DQ10s back in 1980 instead of buying a car!!! My mom didn't understand, she probably still doesn't...), so I definatelly understand where you are coming from! Then I modified them, phase aligned them, mirror imaged the drivers, etc.. and I was only 18 back then! Not really sure if I could hear that difference, but I knew it was worth doing!

What was enlightening to me was the clarity, and the accuracy of the sound coming out of the box for this build. Holy Cow, that was really new and special. I've never experienced that before...

So, that is hard to describe for me

Rob

 

[BogeyBass]

I do believe that there is a small but worthwhile improvement in bass smoothness from spreading out your bass sources on a single home audio speaker in a small room like a living room, such as significantly displacing your ports relative to the woofer (or even relative to one another) in all three dimensions. However in a large room, where a live performance is more likely to take place, I suspect the effect is negligible as best.

I feel likewise from a Hi Fi view flared round ports will sound the best and be more accurate.

I also feel that a suggestion that Eminence recommends is the best method for Live sound applications.

Which would be, 4 evenly placed round ports mounted closely to the Driver.

I have tried to model different ports with a Acoustic simulator to
see the effect of forward and rearward ports. Also was interested in the effect of a single shelf port compared to multiple ports.

The model is showing sound pressure by color, you can apply negative/positive pressure to whichever color you like. Lets just assume red is positive and green is negative pressure, and a sinewave waveform is being produced.

I took a screen shot for each one at the same cycle. Should show a Green negative pressure leaving the baffle including the driver and port pressure that has just combined for a Half cycle of the port resonating. I captured the positive pressure when the port energy is just starting to leave the port. This would be very shortly after the volume has filled with positive pressure from the previous negative pressure that has just left the cone.
This also would be slightly after the same time where the cone shows little movement since it is pushing against a volume completely filled with pressure.

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so this was my concern with slot ports, you can see distortion when the pressures combine, and with more evenly placed ports its much smoother. Also having a large single port still leaves a large amount of pressure in the enclosure which adds to the creation of standing waves, and with more evenly placed ports almost all of the pressure is pushed out, for each half cycle of the sinewave.
big post.......sorry

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[robthebassplaye]

I'm well aware of the price of some of these materials.. Just wanted to know if the hard research was done, not so much on a price basis, but performance basis.. if there was a conscious, performance-based decision made on what components to use.. Sorta like the guy who asked why some of these other speaker brands weren't used.. Polystyrene.. yeah I knew that...lol... just don't use it w/polyester resin..

From my model boating days, I knew vaccum bagged carbon fiber was the lightest possible construction.. any advantages to doing that in this application??

No doubt that carbon fiber will be the best option, at least in my way of thinking.

That will certainly get to the lowest weight / performance ratio...

But, Ouch thats gonna be expensive, even for me!!! Thats why I didn't go that route, and one of my fundamental rules was "Cost is no object"...

But, I am certain that carbon compoiste willl cost 3 to 4x the cost of my basic fiberglass materials. I dont personally think it will provide any advange technically , but definately it will look very cool! And, no doubt, that is worth something..

So, I don't know how to put a price on that... Malybe its not necessary...

Rob

 

[Mike Arnopol]

There are other drivers that may equal or surpass the Eminence, at least in certain areas. The Beyma neo 12MW/ND looks interesting. There are also some Faitals that look ok. When you get into fuller range 8's and 10's the Beyma, Faital, and Ciare neos look good. I'm building 2 uber light composite cabs using 8inchers more for upright players using the Faital in one and the Ciare in the other. The Faital will weigh about 10# loaded and the Ciare about 16#. The Faital should be about as loud as a normal 10incher, while the Ciare should begin to compete with 12's. For old fart upright players like me. And now (which wasn't the case a year ago) the Eminence drivers are the most expensive. As far as epoxy, I'm using one from U.S. Composites that works well and is about 1/2 the price of West.
Vacuum bagging looks interesting--I think Robby is doing it. I've heard that you can save as much as 25% epoxy weight by doing it. But it adds to the cost buying the peelply and breather cloth, film and whatnot. Still looks cool, though.
I LOVE the port simulations---how cool is that?

 

[Petebass]

But, I am certain that carbon compoiste willl cost 3 to 4x the cost of my basic fiberglass materials. I dont personally think it will provide any advange technically , but definately it will look very cool! And, no doubt, that is worth something..

When I asked about it Carbon fiber was 10 times the price of woven fiberglass (I'm in Australia, so YMMV).

Let me put it another way:-

I didn't build it, but this is a CF version of one if my older designs. Long story short... At one particular gig, the guy who hired us asked if he could plug into my amp and play a song or 2 on his Stienberger. Afterwards, he asked a million questions about my entire rig and I mentioned I was planning to one day build a cab from composites. Little did I know he has won Olympic medals in sailing and from that, has some very good friends who are world class Carbon Fiber experts.

One thing led to another and the end result is he bought an Acoustic Image amp just like mine, then got two of these Carbon fiber versions of my 1x12s cabs made up. Now let me tell you, this guy is LOADED, and I mean Multi-Millionaire, big mansion, money to burn wealthy! Yet he built two of these cabs by pulling favors rather than outlaying the cash. That does that tell you about what the price would have been for cash?

I'd also be loathe to cover a CF cab. You'd have to leave the CF exposed wouldn't you for that cool Look right? That means I'd either have to invest in a vacuum bagging and mold setup , or pay someone else to do it for you - both would cost more.....

 

[Passinwind]

so this was my concern with slot ports, you can see distortion when the pressures combine, and with more evenly placed ports its much smoother. Also having a large single port still leaves a large amount of pressure in the enclosure which adds to the creation of standing waves, and with more evenly placed ports almost all of the pressure is pushed out, for each half cycle of the sinewave.

Bogey, what sim program are you using? Can you post a few screenshots of a model of behavior at say half an octave below port tuning?

 

[robthebassplaye]

When I asked about it Carbon fiber was 10 times the price of woven fiberglass (I'm in Australia, so YMMV).

Let me put it another way:-

I didn't build it, but this is a CF version of one if my older designs. Long story short... At one particular gig, the guy who hired us asked if he could plug into my amp and play a song or 2 on his Stienberger. Afterwards, he asked a million questions about my entire rig and I mentioned I was planning to one day build a cab from composites. Little did I know he has won Olympic medals in sailing and from that, has some very good friends who are world class Carbon Fiber experts.

One thing led to another and the end result is he bought an Acoustic Image amp just like mine, then got two of these Carbon fiber versions of my 1x12s cabs made up. Now let me tell you, this guy is LOADED, and I mean Multi-Millionaire, big mansion, money to burn wealthy! Yet he built two of these cabs by pulling favors rather than outlaying the cash. That does that tell you about what the price would have been for cash?

I'd also be loathe to cover a CF cab. You'd have to leave the CF exposed wouldn't you for that cool Look right? That means I'd either have to invest in a vacuum bagging and mold setup , or pay someone else to do it for you - both would cost more.....

Wow - holy cow, that is beautiful!!! I would not cover that either, can't blame you. It is geourgous!!!

I've wondered what something like this would look like, and, BAM! - there is it is!

I love this site! Where else in this world could you find that!!! AHHH, Thank you SO much for posting pictures of that. I bet it sounds awesome! You are a very lucky fellow to own that..

Rob

 

[robthebassplaye]

Bogey, what sim program are you using? Can you post a few screenshots of a model of behavior at say half an octave below port tuning?

Hi Everyone,

Porting simulation is just that - it's a simulation. I have analized this up the wazoo (to use a technical term)... Ports and all, that is....

There is the theory, and that holds absolutely true (based on my measurements and analysis) for small to medium signals. You can use all of the equations, and that works and is correct.

But, once you crank it up, that is, when you have the ports really pushing out air, those equations break down. And, some of that is audible (at least to me)...

Even if you have a simulation that reports back air velocity through the port, I am not satisfied with that - I' ve build cabs different ways with different ports, and its really hard to describe what you hear from those ports. Some folks call it "farting", and that is very obvious, once you have heard it. But, there are definately more sublte effects that are also audible, and I don't really know what to call those... Even things like having the end of the port close to a rear wall are audible. There are guidelines that you can use for designing those, but it's very interesting to actually hear those effects and decide what you are OK with.

So, once you reach the point of really having significant airflow out of those holes, I would recomennd you use your ears to decide what you like.

From my experience, ears are one of the best instruments on the planet. Use them, decide what you like, and then go that way.

Experiments are a great thing. And, luckily with ports, it's not that hard to modify them, to make them bigger or smaller...

I love equations, and physics, trust me, that is my bread and butter. But, there are no, absolutely no, replacements for ears.

Once you hear what you like. then make the port design permanent.

Thats my advice, anyway...

Rob

 

[robthebassplaye]

Bogey, what sim program are you using? Can you post a few screenshots of a model of behavior at say half an octave below port tuning?

I would also be very interested in seeing this...

To me, this is a very 2nd or 3rd order effect, and based on my experience, most models and simulations dont get this right. At least, the one's I've been exposed to.

And, it's really hard to get the right environment to make this kind of measurement. At low frequencies, the room (or the environment that the measurements are being taken in) can really affect the results.

The room "becomes" part of the cabinet, especially at low freqs.

Cool thread!

Rob

 

[LarryR]

I know nothing about cab design but I admire all you guys for your knowledge and willingness to share it. Just thought I'd mention the company Flite, who's been building (i think foam) cabs for over 20 years. No idea how they sound, but according to their site they are def the lightest cabs I've seen.
Single 10 neo = 11.5lbs, single 15 = 17.5lbs
Flite Ultralite Speaker Cabinets - Bass Cabinets

@Petebass, thanks for sharing that pic and story. What a cab!

 

[Bass Unique]

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so this was my concern with slot ports, you can see distortion when the pressures combine, and with more evenly placed ports its much smoother. Also having a large single port still leaves a large amount of pressure in the enclosure which adds to the creation of standing waves, and with more evenly placed ports almost all of the pressure is pushed out, for each half cycle of the sinewave.

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In your model, have you accounted for the effect of the floor? It looks like it is in free space and any symetrical model would appear smoother. With the floor in place, the shelf is extended forward compared to the speaker which should straighten the image slightly.

An otherwise symetrical box would also then be distorted by the floor.

 

[alexclaber]

Does that simulator allow you to continuously vary the phase and magnitude of each source? Those graphics suggest identical phase and equal SPL from each source. Also once you get up to rock band SPL there's a whole host of non-linearities involved. And how do the pressure modes transform to velocity modes and deliver the wave?

 

[robthebassplaye]

I know nothing about cab design but I admire all you guys for your knowledge and willingness to share it. Just thought I'd mention the company Flite, who's been building (i think foam) cabs for over 20 years. No idea how they sound, but according to their site they are def the lightest cabs I've seen.
Single 10 neo = 11.5lbs, single 15 = 17.5lbs
Flite Ultralite Speaker Cabinets - Bass Cabinets

@Petebass, thanks for sharing that pic and story. What a cab!

Wow, that is awesome, I was very excited to see that someone is trying to make a living at building these types of cabs - thank you for sharing that.

I really hope that is working out, it's a very nobile undertaking (at least, in my book, thats what I think)

I went on line to order one, honestly, becuase I really would like to support this kind of thing. I wanted to send him an order, and to buy a few!

When I went to pay, it said that flitecabs wasnt accepting orders - payapl had some kind of problem with it. So I'm not sure whats up with that... Maybe it's a problem on my end...

Anyway,

The prices seemed really very reasonable (less than $!K !!! for a bass cab!! ). So, however they are making that work, is a very opportunity for bass players, In my opinion.

If its a fiberglass epoxy build, for that price, I definately would buy one! Or 2, or 3! Trust me, I know how much work goes into making one of those, and if they are willing to sell them at that price, I'm definately a buyer!

I'm definately going to give them my business and buy one, and I'll certainly let the folks on this forum know my observations. But at that price, I think its going to be awesome!!!

Rob

 

[Mike Arnopol]

I don"t think that Flite uses this technology. As I remember it was some sort of cardboard honeycomb with some sort of plastic or resin panels. They might have changed, though. But at their price point (very reasonable) I doubt it.