Maelstrom-18" Gen II Landed

**Kevin Haskins** · **06-19-09, 08:40 PM**

The Maelstrom-18" shipment arrived at the warehouse today a week ahead of schedule. I put everything else aside and spent some time getting updated parameters.

Measured the same way I do all our big subs. I use Praxis and a relatively higher voltage than something like the Woofer Tester in order to get a more realistic representation of the Cms.

These are dual voice coil drivers. Each voice coil is a nominal 2-ohm load so you can put them in series for a nominal 4-ohm load, or run them in parallel for a 1-ohm load. This is the major difference with this production run.

You will notice from the updated parameters that we have picked up some BL & Mms. This dual 2-ohm coil is a little stouter than our last coils. I wanted the extra BL for the new Maelstrom-21" and it also gives us a little more power handling while allowing for slightly smaller boxes than the first generation Maelstrom. I've updated the power rating to 1800W to reflect the extra copper mass in the coil.

Here they are in all their glory. Note: The driver looks exactly the same. They are identical on the outside the only real build difference being the coil and the spider.

I took the parameters with the VC in series. Did some quick calculations to get the rest of the numbers. If you see anything askew, let me know. I'm in a rush to get home for a weekend hiking trip so I rushed to get these up before I left. I'll be back on Monday if the Mountain Lions don't get hungry.

These start shipping on Monday. I'll update the web site when I get back.

Kevin Haskins
Exodus Audio

**robseyes** · **06-20-09, 02:09 AM**

Hi Kevin,
Is the inductance really that high for the coils in series?

**dynamowhum** · **06-20-09, 07:03 AM**

Some one now needs to make a WinIsd on this updated driver.

**Mike P.** · **06-20-09, 07:31 AM**

I'm working on it. Waiting for clarification on the Le spec.

**Jugix** · **06-20-09, 09:41 AM**

Looks nice. Q=0.704 in 130liter box. Fb seems to be little higher but MAX-SPL is the same with little more power input. I like the change.

**Kevin Haskins** · **06-20-09, 01:50 PM**

Quote:

robseyes wrote:

Hi Kevin,
Is the inductance really that high for the coils in series?

Yes and no.... if measured at 1K with an inductance meter the raw coil will read about 2.0mH per coil. The first version had dual 4-ohm coils, each being around 2.0mH per coil, in parallel about 1.0mH. The single 4-ohm coil was around 3.3mH. We added some L in order to increase the BL and power handling so they inductance did go up in proportion to the extra BL but not much. You have to look at BL/Re ratio, not just the raw BL number. It didn't change much. It is marginally higher than the original coil.

I wouldn't get too caught up in a 1K inductance measurement. You don't run them at 1K. The inductance under 100Hz is down around 3.5mH with the coils in series. It also changes with power, frequency and it changes with coil posistion. It is also just one non-liniearity. You would have to look at all the non-linearities to get a perfect picture of what the driver does in real boxes under real use. The T/S model is a very simple picture of what occurs under a very limited set of conditions. If people saw representations of what happened to the WINISD models when they modeled the actual non-linearities, they would have a cow.

Here are a couple of the White Papers that Wiggins did in the old days describing DVC drivers. It is good reading if your new to the concept.

http://adireaudio.com/Files/DualVoiceCoilWiring.pdf

http://adireaudio.com/Files/DualVoiceCoilDrivers.pdf

Kevin Haskins
Exodus Audio

**Mike P.** · **06-20-09, 03:14 PM**

18" Maelstrom-X Gen. II WinISD file has been added to the downloads page.

http://www.hometheatershack.com/foru...tml#post127390

**robseyes** · **06-20-09, 03:40 PM**

Quote:

Kevin Haskins wrote:

Yes and no.... if measured at 1K with an inductance meter the raw coil will read about 2.0mH per coil. The first version had dual 4-ohm coils, each being around 2.0mH per coil, in parallel about 1.0mH. The single 4-ohm coil was around 3.3mH. We added some L in order to increase the BL and power handling so they inductance did go up in proportion to the extra BL but not much. You have to look at BL/Re ratio, not just the raw BL number. It didn't change much. It is marginally higher than the original coil.

I wouldn't get too caught up in a 1K inductance measurement. You don't run them at 1K. The inductance under 100Hz is down around 3.5mH with the coils in series. It also changes with power, frequency and it changes with coil posistion. It is also just one non-liniearity. You would have to look at all the non-linearities to get a perfect picture of what the driver does in real boxes under real use. The T/S model is a very simple picture of what occurs under a very limited set of conditions. If people saw representations of what happened to the WINISD models when they modeled the actual non-linearities, they would have a cow.

Here are a couple of the White Papers that Wiggins did in the old days describing DVC drivers. It is good reading if your new to the concept.

http://adireaudio.com/Files/DualVoiceCoilWiring.pdf

http://adireaudio.com/Files/DualVoiceCoilDrivers.pdf

Kevin Haskins
Exodus Audio

Thanks for the clarification. I have the original dual voice coils, so i was just curious. It modeled differently from the original in unibox. The original stayed fairly flat north of 90hz while the new model starts to roll off past 90 hz.

Thanks for the reading....I look forward to studying it.

I really like the extra BL!

**Warpdrv** · **06-20-09, 04:03 PM**

Nice work Kevin, Gen II's look like they will be winners.... Still loving the pounding I'm getting from the 3-Gen1's I have running.... I may just have to pick one of these up

**Kevin Haskins** · **06-20-09, 04:53 PM**

Quote:

robseyes wrote:

Thanks for the clarification. I have the original dual voice coils, so i was just curious. It modeled differently from the original in unibox. The original stayed fairly flat north of 90hz while the new model starts to roll off past 90 hz.

Thanks for the reading....I look forward to studying it.

It is a fairly complex situation with inductance. I just talked to Wiggins about writing a simple 1-2 page White Paper on Inductance in Subwoofers. I think that is what is needed because there is a lot of misinformation about what is and is not important. In a nutshell, the biggest issue is Le with power & stroke, as long as the native inductance isn't such that it negatively impacts the bandwidth of the device. Varying inductance with power & stroke basically ends up modulating the corner frequency with output and it generates flux modulation and distortion products in the motor. Hold the Le constant, and you mitigate those issues. That is the mojo behind the AlCu inductance rings and why they are better than a simple sleeve that may drop the static Le measurement, but they actually increase the variance of Le with stroke and power. Your better off with the higher static Le, yet keeping it constant.

Lets quickly look at the effect of inductance on the output of a subwoofer in a box. Since we are talking about the Maelstrom, may as well use it as a test-mule.

The box model here is using our current parameters from the Maelstrom-18" Version II. The box is a 7 ft^3, 15% fill Passive Radiator build with a pair of PR-18s. It is tuned around 18Hz and I have a 16Hz subsonic filter on it.

Here is the frequency response if our inductance was an imaginary 1.0mH. If we clicked the Le feature on/off in LSPCad you would see very little difference over this frequency range.

Here is the exact same model but I just increased the inductance to 2.0mH.

Ditto.... just increased it to 3.0mH.

And finally this is the inductance with our 3.5mH which is probably representative of what you will actually get from running the newest model in series.

Not much of a difference. About the most you can say is you get a subtle 1-2dB lift in the upper side of this range. One thing to keep in mind is that your going to be using some sort of Low Pass filter in real life. You don't run the sub full range so lets look at what we get when we use a 80Hz 2nd Order LP filter. That is about the highest corner frequency people will use. Most will use a lower corner frequency with possibly higher order slopes, which of course will show even fewer differences.

Here is the response with an imaginary 1.0mH coil, and 2nd order LP @ 80Hz.

Here is the exact same box as above, with the 3.5mH coil.

You can see it has even less of a impact on the final response. I'd say about 0.5dB @ 50Hz. When you put that design in a room, that difference is going to be totally swamped by the room issues. The actual effect of the Le on the FR of the system is minimal. What IS important, is that the Le remains constant as possible with stroke & power. That is the secret mojo behind all of the Exodus motor designs.

Kevin Haskins
Exodus Audio

**SteveCallas** · **06-21-09, 03:45 AM**

People will grab and hold on to anything they read - whether accurate or inaccurate, whether understanding the concepts in play or not, whether rumor or truth. This DIY crowd is such a fickle market...I gotta imagine you're

a lot of the time Kevin.

Keep up the good work.

**vili** · **06-21-09, 05:21 PM**

Awesome to know that the Gen IIs are here. I have a question and I'm pretty sure I already know the answer, but it sounds like a neat option possibly for the future (if it can happen).

Is there any way to "lock" a PR so that it doesn't work as intended? So that someone can build a dual PR box and they can use it like normal or they can "lock" the PRs so they don't move and the box then behaves as a sealed enclosure. I guess there would have to be someway to lock the suspension or something, but it seems like a neat idea. That way people could have a PR build and then switch to what sealed would sound like in the same enclosure. I realize then the PRs would merely be expensive place holders, but at least you would know how a ported enclosure sounds and a sealed enclosure. Just a thought.

**Kevin Haskins** · **06-21-09, 10:18 PM**

Quote:

SteveCallas wrote:

People will grab and hold on to anything they read - whether accurate or inaccurate, whether understanding the concepts in play or not, whether rumor or truth. This DIY crowd is such a fickle market...I gotta imagine you're

a lot of the time Kevin.

Keep up the good work.

I'll admit to getting frustrated now and then. For the most part, that has more to do with my short comings though. Most DIYers are great people to deal with. I get an occasional difficult person but by far, most are fantastic people to work with.

There is a lot of education that goes into the process. That also tends to get me into some trouble because there is a lot of opinion in audio. Some of that is natural. People passionate about any subject are going to have heated disagreements.

I just try to keep improving what I'm doing every year. Sometimes I wish I could just waive the magic wand and have everything perfect but producing anything is an exercise in patience and perseverance.

Thanks for the kind words Steve.

Kevin Haskins
Exodus Audio

**Jason_Nolan** · **06-21-09, 10:47 PM**

They look really good to me. I still haven't decided on the 18's or the 21's. That's mostly due to me being in process of house shopping.

I only wish you had different voice coil options, but I understand the reasoning behind keeping cost down.

Nice job.

**robseyes** · **06-23-09, 12:07 AM**

Quote:

Kevin Haskins wrote:

It is a fairly complex situation with inductance. I just talked to Wiggins about writing a simple 1-2 page White Paper on Inductance in Subwoofers. I think that is what is needed because there is a lot of misinformation about what is and is not important. In a nutshell, the biggest issue is Le with power & stroke, as long as the native inductance isn't such that it negatively impacts the bandwidth of the device. Varying inductance with power & stroke basically ends up modulating the corner frequency with output and it generates flux modulation and distortion products in the motor. Hold the Le constant, and you mitigate those issues. That is the mojo behind the AlCu inductance rings and why they are better than a simple sleeve that may drop the static Le measurement, but they actually increase the variance of Le with stroke and power. Your better off with the higher static Le, yet keeping it constant.

Lets quickly look at the effect of inductance on the output of a subwoofer in a box. Since we are talking about the Maelstrom, may as well use it as a test-mule.

The box model here is using our current parameters from the Maelstrom-18" Version II. The box is a 7 ft^3, 15% fill Passive Radiator build with a pair of PR-18s. It is tuned around 18Hz and I have a 16Hz subsonic filter on it.

Here is the frequency response if our inductance was an imaginary 1.0mH. If we clicked the Le feature on/off in LSPCad you would see very little difference over this frequency range.

Here is the exact same model but I just increased the inductance to 2.0mH.

Ditto.... just increased it to 3.0mH.

And finally this is the inductance with our 3.5mH which is probably representative of what you will actually get from running the newest model in series.

Not much of a difference. About the most you can say is you get a subtle 1-2dB lift in the upper side of this range. One thing to keep in mind is that your going to be using some sort of Low Pass filter in real life. You don't run the sub full range so lets look at what we get when we use a 80Hz 2nd Order LP filter. That is about the highest corner frequency people will use. Most will use a lower corner frequency with possibly higher order slopes, which of course will show even fewer differences.

Here is the response with an imaginary 1.0mH coil, and 2nd order LP @ 80Hz.

Here is the exact same box as above, with the 3.5mH coil.

You can see it has even less of a impact on the final response. I'd say about 0.5dB @ 50Hz. When you put that design in a room, that difference is going to be totally swamped by the room issues. The actual effect of the Le on the FR of the system is minimal. What IS important, is that the Le remains constant as possible with stroke & power. That is the secret mojo behind all of the Exodus motor designs.

Kevin Haskins
Exodus Audio

Thankyou for the detailed explanation. I appreciate you effort very much. I am a quiet lurker who likes to learn ..... I certainly did not want to imply that I was "calling you out" so to speak. I have a pair of your original maelstroms that are a wonderful product. I was just a little curious about the changes.

Cut me a little slack Steve...

**Kevin Haskins** · **06-23-09, 10:44 AM**

Quote:

robseyes wrote:

Thankyou for the detailed explanation. I appreciate you effort very much. I am a quiet lurker who likes to learn ..... I certainly did not want to imply that I was "calling you out" so to speak. I have a pair of your original maelstroms that are a wonderful product. I was just a little curious about the changes.

Cut me a little slack Steve...

I didn't take it any other way than a simple question. I figured it was something I better answer with a good explanation sooner rather than later. That was mainly the reason for all the detail.

Also... we are working on a White Paper for inductance in subs/midwoofers. It gives a better explanation for the reason for the shorting ring design used in the Exodus motors. Your question was a good one that leads us into that subject. I didn't feel "called out" in any way. Keep them coming.

Kevin Haskins
Exodus Audio

**Kevin Haskins** · **06-23-09, 10:55 AM**

Quote:

vili wrote:

Awesome to know that the Gen IIs are here. I have a question and I'm pretty sure I already know the answer, but it sounds like a neat option possibly for the future (if it can happen).

Is there any way to "lock" a PR so that it doesn't work as intended? So that someone can build a dual PR box and they can use it like normal or they can "lock" the PRs so they don't move and the box then behaves as a sealed enclosure. I guess there would have to be someway to lock the suspension or something, but it seems like a neat idea. That way people could have a PR build and then switch to what sealed would sound like in the same enclosure. I realize then the PRs would merely be expensive place holders, but at least you would know how a ported enclosure sounds and a sealed enclosure. Just a thought.

There is a way to accomplish most things. It always comes down to cost, and viability. If someone approached me with a wad of cash and wanted such a thing, I'd happily find a way of doing it.

On ported systems, you can easily just plug the port. I find that most people don't use the system with the port plugged. It is virtually free for them to experiment with the two and most people don't. The passives are already expensive for people who are comparing them with an essentially "free" port. I'm mainly looking at ways to decrease their cost. Anything adding complexity runs counter to that goal.

Kevin Haskins
Exodus Audio

**SteveCallas** · **06-23-09, 08:55 PM**

Quote:

robseyes wrote:

Cut me a little slack Steve...

No worries, all you did was ask a question.

What I was referring to was the products that have disappeared and even companies that have gone out of business due to innaccurate tales being told about a product or manufacturing process on audio forums. It has happened many times.

**robseyes** · **06-24-09, 01:06 AM**

Quote:

SteveCallas wrote:

No worries, all you did was ask a question.

What I was referring to was the products that have disappeared and even companies that have gone out of business due to innaccurate tales being told about a product or manufacturing process on audio forums. It has happened many times.

No problem. I understand what you are saying. It seems like everyone is an authority when it comes to DIY. Kevin has always been a standup guy...even when I showed up once at his shop a few years ago. He was very gracious & polite. I will always do business with a fellow business owner like him.

**ironglen** · **06-24-09, 03:32 AM**

Maelstrom just landed- and already being shipped! Thank you Kevin for the excellent service: feedback via email, updated thread on HTS, and very prompt shipping. (if the driver performance is similar to the customer service, then I'm in for a shocker

**Mario** · **06-24-09, 12:42 PM**

I've been contemplating an LLT sub based on Maelstrom driver and had all parameters figured out quite nicely. But the new driver seems to mess up the pretty picture. I can't figure out how to get a nice, flat response. What am I doing wrong?

**Mike P.** · **06-24-09, 01:36 PM**

Delete the Maelstrom-X file that you have and download the Maelstrom-X Gen I file. It has been updated with the Le parameter. A fairer comparison can then be made.

**Ricci** · **06-24-09, 01:45 PM**

The Gen 2 needs just a bit less airspace to do it's thing and other than that should be about the same. I don't think that the inductance has changed radically like the sims are showing. Read Kevins comments on inductance in subwoofers above. (looking forward to that white paper Kev

). Don't worry about a ruler flat response. Any room that you place the sub into will do much more damage to a pretty response than that.

**vili** · **06-24-09, 01:55 PM**

Amen about the room. With my 26" cube I had to use 3-12db cuts within about 10hz of each other in order to pull the low end down. Below 40hz or so was ridiculous with room gain. Almost makes me wonder if I would get the same effect with a sealed with my room as I would with the PRed since I have to cut the low end.

**Kevin Haskins** · **06-24-09, 02:00 PM**

Quote:

Mario wrote:

I've been contemplating an LLT sub based on Maelstrom driver and had all parameters figured out quite nicely. But the new driver seems to mess up the pretty picture. I can't figure out how to get a nice, flat response. What am I doing wrong?

You need a smaller box. Anytime you get that lazy hump curve your trying to use the driver in a bigger box than it needs.

The GenII Maelstrom is suitable for slightly smaller boxes. I'd say 10ft^3 (280L) is a plenty large box at the higher end of the scale.

Kevin Haskins
Exodus Audio

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