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Discussion Starter #1
I just saw your announcement and preliminary specs Kevin. Nice!:T If you can hit that target I think you'll have a real winner. I know everything is preliminary, or guesstimate's at this point, but what would the minor differences to the Mal-X motor be? I assume that the spiders, magnets geometry and venting will all be the same. Changes to the vc wind/ gap?
 

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Changes would be to the VC wind & gap but otherwise pretty much the same motor. The spider will be different only really in compliance. I'm happy with the suspension as it is so I don't see any need to monkey with it.

The cone and basket are bigger. :) It will be a dual 2-ohm design like the rest of the lineup. It will be a the same sort of cone, dustcap design as the rest of the lineup. It will have the same AlCu inductance configuration that is working really well based upon the Klippel data with power, stroke and frequency. Overall, there is no reason to make radical changes to the motor and there is some economy of scale in keeping it common to both drivers.


Kevin Haskins
Exodus Audio
 

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I like the specs so far, Kevin. This could be a really solid driver and as long as the price is reasonable (for me, keep it under $600) then I could see this being a popular driver in addition to the Mal-X. Especially those out there that are looking to maximize power density per cubic foot.

I'll be keeping my eye on this beauty. :D
 

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I am working on my box for it now. 19 cubes before displacement (sub and port). Is an 8.5" tube large enough, or will it need at least 10"? I'm guessing there's so many reasons why this sub shouldn't be ported... too long so 1st harmonic and so on...forgetting that, would 8.5" be enough? 10"?

I just went to Menards to grab a 10" and came to find they make 3 sizes for every given size for shipping purposes. The 8" was 7.75", 8.25", and 8.75" external.... they ship them in groups of 3, smallest inside. There were no 10", they don't carry them but there were instructions on how much concrete is needed to fill 8" 10" 12" and 16". None of the 12" tubes were actually 12" either.
 

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It is going to take large boxes for resonant builds, no way around it. That actually helps on the ported front, because larger = shorter port for a given tune. If you model it, you can see that you can get any reasonable sized port to chuff given enough power. What you have to consider though, is that the output level when something like an 8" port starts to make noise is a fearsome amount of LF output. You can build a design knowing the port will limit you and still have a "good" design if it hits your target goals.

The other option is to build a PR. A pair of PR-18s works pretty good. I know most people use the rule of thumb that the PRs should be twice the total Vd of the active driver but if you model it, you run the PRs pretty hard but well within their limits. I'll have to build one and see if I can tear apart the PR-18s once they are in stock but from looking at the simulations, I'd say with a proper subsonic filter you could easily get away with a pair of PR-18s and tune it as deep as you need.

Kevin Haskins
Exodus Audio
 

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Kevin, this is going in-car... no more debates on "can" and "should"... So here's what I have:

48" wide, 32" tall, and 24" deep external. Single layer 3/4" MDF. Either the 8.75" tube or about a 10" tube if I can locate someone that sells them. Probably not an aeroport or anything fancy... strait pipe.

I agree with you, if I am tuning somewhere around 15Hz-25Hz, with a 22" driver and an 8" port, port noise should not matter... but I am more worried about port compression and efficiency in this case. (without getting too technical)

So I should be OK with an 8" port?
 

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Kevin, this is going in-car... no more debates on "can" and "should"... So here's what I have:

48" wide, 32" tall, and 24" deep external. Single layer 3/4" MDF. Either the 8.75" tube or about a 10" tube if I can locate someone that sells them. Probably not an aeroport or anything fancy... strait pipe.

I agree with you, if I am tuning somewhere around 15Hz-25Hz, with a 22" driver and an 8" port, port noise should not matter... but I am more worried about port compression and efficiency in this case. (without getting too technical)

So I should be OK with an 8" port?
Now this is a guy I can have a beer with. :T Go with a 10" port.
 

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Kevin Haskins said:
Latest Updates: 3-20-2009


Maelstrom-21" on track. I should have early Klippel data within a couple weeks.
So what did the Klippel Data reveal? Want to tease us a little?! :R
 

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So what did the Klippel Data reveal? Want to tease us a little?! :R
Mainly, we use them to confirm suspensions, centering and the location of the shorting rings. Some of the data is useful, some of it useless but I don't really have any tasty tid-bits.

Kevin Haskins
Exodus Audio
 

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Discussion Starter #12
Some of the data is useful, some of it useless but I don't really have any tasty tid-bits.

Kevin Haskins
Exodus Audio
:foottap: :sad:

What's the projected weight on this guy? 60lbs?

This is a bit off topic but, which driver did you have made first? The Tempest X? I was just wondering why you don't use the same or a very similar motor as the Mal-X's on the 15" Tempest X? That was my complaint with gen1 of that driver was that it needed some more BL to be optomized for smaller boxes. The price on it was great but it needed pretty large boxes. If it was a better fit in a 3ft sealed, 4-6ft PR'd, smaller ported enclosures it'd fill a really good role in the market about now. I'm hoping version 2 makes a move towards this end?
 

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:foottap: :sad:

What's the projected weight on this guy? 60lbs?

This is a bit off topic but, which driver did you have made first? The Tempest X? I was just wondering why you don't use the same or a very similar motor as the Mal-X's on the 15" Tempest X? That was my complaint with gen1 of that driver was that it needed some more BL to be optomized for smaller boxes. The price on it was great but it needed pretty large boxes. If it was a better fit in a 3ft sealed, 4-6ft PR'd, smaller ported enclosures it'd fill a really good role in the market about now. I'm hoping version 2 makes a move towards this end?

Yes... it should be about 3-5lbs shipping weight heavier. The raw weight isn't that much more because the aluminum basket isn't that much more and paper, foam, rubber doesn't add a lot of weight. The motor dominates the weight.

What I've tried to do is to have an intelligent progression of box sizes as you move up the line. As you said, the first generation Tempest-X had a weak motor for that size of a driver. It ended up wanting bigger boxes. The second generation is getting a stronger motor but the Tempest-X will still be a large box driver.

I could do a 15" Maelstrom, but it would have a Maelstrom price (about $400) and the Shiva already has issues with port sizes in those size boxes. The motor is where all the money is in the design. Going down a basket size & cone size don't make that much of a difference in the cost of manufacturing. That works out ok because most of the people in that price category are looking for the most bang/$. A small box design of the Tempest-X, optimized around 4-6 cubic foot resonant builds wouldn't work well unless you used Passive Radiators. It would also require even more BL (and more cost in the motor) hence you would end up with very expensive 4-6 ft^3 PR boxes. Most people are going to just buy a Maelstrom-18, equalize it and run it in that same size and get roughly the same output once you get into that price category.

But... with a weaker motor, that goes with larger box sizes, people can build larger cabinets with large ports and still get great performance with the tradeoff of the larger box. Sonotubes and other large box designs with 6" ports and the BASH 500W amp makes for very high bang/$ builds for people who have lots of space.

Here is the run-down on how I see the box sizes for the driver lineup.

Shiva-X:

1.5-3 cubic feet sealed for automotive use
2.5-4 ft^3 sealed for home use
4-6 ft^3 resonant builds

Tempest-X

2.5-3 ft^3 automotive
4-7 ft^3 sealed home
7-10 ft^3 resonant builds home

Maelstrom-18"

3 ft^3 & up for automotive
4-7 ft^3 sealed home
6-8 ft^3 PR Builds
8-11 ft^3 ported

Maelstrom-21"

6-10 ft^3 sealed
8-10 ft^3 PR Builds
To much output for a port


Those are just general guidelines but you can see a progression up the size/output/price scale as you go.


Kevin Haskins
Exodus Audio
 

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Wow to much output on the 21" for a port. Would that mean that sealed it wouldn't have more low end than the Maelstrom 18" ported? Sorry if this is a lame question.
Also Kevin do you think this will be available by August?
 

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Wow to much output on the 21" for a port. Would that mean that sealed it wouldn't have more low end than the Maelstrom 18" ported? Sorry if this is a lame question.
Also Kevin do you think this will be available by August?
Three things you deal with. Remember Hoffman's Iron Law. Box size, efficiency and bandwidth are all related. Change one, you have to compensate with the others.

Assuming everything else is the same, the box size scales with the surface area of the driver. If you keep the box size the same and increase the surface area of the driver, you pay for it in bandwidth (everything else remaining the same). That means if all other parameters are the same, as you increase the cone size by 30% you need to increase the box size by that same proportion in order to maintain the same F3.

Many people automatically think a bigger driver will go deeper. That isn't the case. A bigger driver gives you more potential output (given the other variables stay the same) but it won't go deeper (assuming you hold all other variables fixed). You need to either equalize it or design the system with a large enough box to get good bandwidth AND good extension.

What you will find with the Exodus driver lineup is that we have chosen parameters that allow close to the same bandwidth, as you scale driver & box size. This is a little bit of a simplification and not strictly true but I tend to pick parameters based upon a given modeled response. Bigger drivers just get bigger boxes on average. I bend the rules slightly with the Shiva-X because it is one of the smaller drivers. Try to push a 12" to deliver really deep bandwidth and you will quickly find it running out of excursion. For that reason, I tend to like to run the ported alignments of the Shiva a little higher than I would a Maelstrom. I'd tune a Shiva @ 20-22Hz, and the Maelstrom @ 16-18Hz. Why? Because the Maelstrom has a lot more potential output and is less likely to reach it's limits. Another rule of thumb to remember is that you need about x4 the amount of air movement capability for every octave you drop given the same SPL. Smaller drivers just don't have the same headroom as does a big 18" or 21" driver and when your pushing for really deep extension at high SPLs, you need every bit of driver you can afford.

Oh.... horns follow different rules. Horn loaded systems are not within the scope of these rules and for most 1st/2nd octave applications, they are not a viable choice. Horns are awesome but they are devices that have a very narrow bandwidth. True subwoofer horns are rare because of the size needed. Danley has done some really cool things with horn loading and Tom's much more of an authority than I on the subject. For most DIYers horns are an extremely complex build. Wiggins did a horn design with the original Tempest and while it was capable of scary dynamics, it was bandwidth limited. It used the sealed box behavior of the driver for the very bottom part of it's bandwidth so it had limitations based upon the driver on the bottom. Up higher, it was capable huge dynamics but it just didn't sound right in a typical living space to me. Bruce Edgar makes a big sub using a pro-sound driver that sounds great. It is bandwidth limited even though it is the size of a refrigerator. It wouldn't be a great HT sub necessarily.

Like any engineering exercise, your playing with trade-offs. You don't get a free lunch. You just have to figure out which lunch you can afford and which one is most likely to fill your belly. :T

I'm projecting sometime in August. Right now that is a promise from the factory. They tend to be optimistic on their delivery schedule so it could always slide. I'll have firmer dates in about a month.

Kevin Haskins
Exodus Audio
 

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Thank you for taking your valuable time. I am quite willing to go 16 ft^3 +. I have a lot of space to use in a 3200ft^3 room. I currently have 2 15" atlas 15" in an IB set up. I love it for music but it just doesn't do it for me in all HT circumstances.
 

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Thank you for taking your valuable time. I am quite willing to go 16 ft^3 +. I have a lot of space to use in a 3200ft^3 room. I currently have 2 15" atlas 15" in an IB set up. I love it for music but it just doesn't do it for me in all HT circumstances.
Hoffman's Iron Law is a generalization that assumes the ability to design the driver. We play with the variables to some extent and make a choice on the box sizes for a given driver.

Contrary to what is commonly thought, there is not an optimal size for a driver. There is a RANGE of optimal volumes.

So... you don't gain anything by building larger than the range the driver is designed around. You could build a big ported Maelstrom-18". You need a BIG port. An 8" port is not oversize. It is much easier and you end up with a much more compact build if you use a pair of Passive Radiators. That allows you to tune it deep (16-18Hz) without the need for LONG ports and big boxes. On both, you need a subsonic filter. My recommendation is to budget for a Velodyne SMS-1 (room measurements, EQ and subsonic filter) and a big pro-amp. Several thousand watts is not too much for a Maelstrom.

That gives you a massive HT sub with some serious output. The big sonotubes make good sense for ported Maelstrom builds because it keeps weight down. You will need to be able to move the sub at one point.

Kevin Haskins
Exodus Audio
 

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Thanks Kevin. I am really not afraid of going up to a 10" port. I have the room and to keep the cost down I don't mind ported designs. I am in the middle of a remodeling project in the kitchen( knocked out part of a wall and put in wet bar) so budget is a little tight for now. I could go Sono but I just don't care for the look that much. I have a DCX 2496 I can use for a filter. Thanks again.
 

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Thanks Kevin. I am really not afraid of going up to a 10" port. I have the room and to keep the cost down I don't mind ported designs. I am in the middle of a remodeling project in the kitchen( knocked out part of a wall and put in wet bar) so budget is a little tight for now. I could go Sono but I just don't care for the look that much. I have a DCX 2496 I can use for a filter. Thanks again.
10" port :), I just had to model that with the M-21. This is with 90 volts input (say, a bridged EP2500), and a 2nd order highpass filter at 12Hz (Q 0.707). I don't know if it's possible to get a 2nd order hpf which works as low as 12Hz, if you know one, let me know. :T

You'd need the 10" port to be 3ft in this box. Net volume of the box is 17ft^3, with 50% stuffing.

 
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