[Craig Treusdell]

I would like more bass mainly for HT.

I'm currently using one Adire Tumult (the original, from 2003) with a QSC RMX2450 amp, but have other plans for it and his twin.

So I need another sub or 4.
The RMX2450 puts out max power of 2400 watts bridged into 4 Ohms. I must work around this.

When modeling the 4 Shiva-X2s against the Mealstrom-21, with 2400 watts (max available) across the 4 Shivas and 1500 watts (max recommended) on the 21, the Shivas win, at least down to 18Hz, by 2dB SPL.

But how accurate is this analysis using Thiele/Small parameters and WinISD? And is the simulation accurate?

So:
4 Shivas each in 3.5 cubes for 14 cubes tuned to 20Hz - plus is 2 enclosures that better integrate in my living room, but more expensive than the 21
or
1 Maelstrom-21 in 19 cubes tuned to 18 hZ - a bit big for my living room, but do-able

Are these simulations accurate? What would you do?

[Kevin Haskins]

The simulations are accurate at low levels where the T/S parameters are stable.   When you are comparing the maximum output levels though the simulations are a "best guess".   

But I'd estimate that the simulation is probably right in that the four Shiva build would have an output advantage.   A Shiva has approx 500 cm^2 and four of them give you 2000 cm^2 of surface area.   The Maelstrom 21" is around 1550 cm^2 so you have an advantage is cone area that heavily favors the four Shiva build.   The extra stroke of the Maelstrom won't make up for it. 

That is assuming you build the four Shiva sub into on enclosure where the four drivers are close enough together that it acts as one acoustic source.   If you split it into multiple subs you get cancellation and the single Maelstrom would likely have more output.   It is academic though.    You are not talking about huge differences in SPL so I'd go with the solution that fits your room and budget the best.    By that I mean.... what kind of enclosure do you have space for?   What will the wife allow?    If you don't have space and size limits that opens up a lot of possibilities but most people end up with at least one or two physical constraints on the size of subs they can build and the location/space they have available in the room.    That drives the choice of drivers as much as anything.

[Craig Treusdell]

I kinda figured that but I wanted to get some other opinions. Just hard to believe since the 21 has a 30% lower Fs, a 4dB efficiency gain, and almost a 25% stroke advantage...

If I do 4 Shivas they will be 2 on each side of the entertainment center, which is quite large, and I should get some acoustic coupling between each two (if that's the correct term), and I know the two sets spaced apart should create constructive and destructive interference at difference frequencies.

I must be the only married guy who has an unlimited WAF 
But even I am tired of raw MDF boxes in the living room for the last 10 years...

I mostly want the 21" because of, well, it's BIG! And I'm sure it sounds good. But anything other than a sonotube enclosure would require a forklift to move. And I still haven't seen a sonotube design that appeals to me. Ideal would be mounting 2-4 in the basement firing up through a vent, where weight/looks wouldn't be an issue since they would be permenant. Problem is this house is on a slab.

Any other opinions? I'm not fixed on just these two subs, just on the amplifier where a 4 Ohm load is ideal.

[Kevin Haskins]

I kinda figured that but I wanted to get some other opinions. Just hard to believe since the 21 has a 30% lower Fs, a 4dB efficiency gain, and almost a 25% stroke advantage...

If I do 4 Shivas they will be 2 on each side of the entertainment center, which is quite large, and I should get some acoustic coupling between each two (if that's the correct term), and I know the two sets spaced apart should create constructive and destructive interference at difference frequencies.

I must be the only married guy who has an unlimited WAF 
But even I am tired of raw MDF boxes in the living room for the last 10 years...

I mostly want the 21" because of, well, it's BIG! And I'm sure it sounds good. But anything other than a sonotube enclosure would require a forklift to move. And I still haven't seen a sonotube design that appeals to me. Ideal would be mounting 2-4 in the basement firing up through a vent, where weight/looks wouldn't be an issue since they would be permenant. Problem is this house is on a slab.

Any other opinions? I'm not fixed on just these two subs, just on the amplifier where a 4 Ohm load is ideal.

There are a number of ways to skin a cat.   The efficiency doesn't really have any consequence in subs.   It is a byproduct of the choice of box size and extension you choose and I'd ignore it.    Model the drivers you want to consider in the range of box sizes I recommend in the application notes and choose the ones that fit your room the best.    If you want a rough guide for how they will compare in maximum output you can look at the total swept area of multiple subs and compare that with the single 21".    It is a rough rule of thumb because there are other variables..... especially when you get into multiples but it gives you a good general idea of how multiple drivers of model 'X' compare to a number of drivers 'Y'.    It only falls apart when you separate the subs in-room.    The multiples will have significant destructive interference and you lose a lot of output compared to a single sub in one location.   The upside is you will on average have a smoother in-room response compared to the single. 

[chlorofille]

Hi Craig,

While the 4 Shivas might produce slightly more output, do note that the Mael 21 will be much lower in distortion especially in the 18-30Hz region. Similar case to a 8 inch reproducing 30Hz vs an 18 inch playing 60Hz. Massive difference in tonal accuracy. I'd say stick with the larger driver.

[Kevin Haskins]

Hi Craig,

While the 4 Shivas might produce slightly more output, do note that the Mael 21 will be much lower in distortion especially in the 18-30Hz region. Similar case to a 8 inch reproducing 30Hz vs an 18 inch playing 60Hz. Massive difference in tonal accuracy. I'd say stick with the larger driver.

Actually.... it makes no difference.    You can use multiple smaller drivers and achieve the same thing.   How much distortion you get is a function of a couple factors other than just the drivers (box design) but there is no reason that the 21" would inherently do better than multiple smaller drivers, especially when they have more swept volume than the larger driver.   Not only is the Sd larger but the overall motor/Sd ratio is such that power handling favors the x4 Shiva build.     Of course.... the x4 Shiva build would cost about twice as much.

Distortion limits are typically only an issue with 1st/2nd octave bass when you get to gross levels so I wouldn't expect non-linear distortion to be an issue with either of these builds.    I'd make the choice on what to build based upon budget, size, and other practical matters like where you expect the finished boxes to fit into the room.   

 

[Craig Treusdell]

So here is a third idea:

Instead of the 4 Shiva-X2s ported, why not 8 Exodus DPL-15s, IB in the attic.
This would give me just a little more than the Shivas especially below 15Hz using my current amplifier.

Now my concern is with neighbors and heat. Anyone have any experience using an IB in the attic? The motor would be mounted such that it would be in the conditioned space of the house with the front of the cone exposed in the attic. I will read up on another forum that discusses this in great detail tonight, but would still appreciate any feedback.

I really don't want to drag a sub up there, hook it up, and listen from outside the house...

And this weekend looks like a good time to buy 

[Kevin Haskins]

So here is a third idea:

Instead of the 4 Shiva-X2s ported, why not 8 Exodus DPL-15s, IB in the attic.
This would give me just a little more than the Shivas especially below 15Hz using my current amplifier.

Now my concern is with neighbors and heat. Anyone have any experience using an IB in the attic? The motor would be mounted such that it would be in the conditioned space of the house with the front of the cone exposed in the attic. I will read up on another forum that discusses this in great detail tonight, but would still appreciate any feedback.

I really don't want to drag a sub up there, hook it up, and listen from outside the house...

And this weekend looks like a good time to buy 

I'll save you some time.... I only have four DPL-15s in stock and after they sell the DPL-15 is not coming back.    They don't sell well enough to keep in inventory and the Tempest-X2 does everything the DPL-15 can do at a slightly higher price.   It also has a little more stroke too but it doesn't make sense to stock both....especially since the DPL-15 sells so slowly. 

There is no problem with IBs...... the biggest issue is that it is highly situation dependent.   You also don't have the same freedom of moving the sub around to optimize location.   It is essentially a very large sealed box so it has all the tradeoffs associated with large sealed designs.   It is a good idea to run a subsonic filter too because the box is so large that it provides no protection via the normal HP function of a box.