Best 15 Inch Sub for ~82L Sealed Box

[Felix2]

Hello,

So I build a couple of subwoofer enclosures that were originally intended for the Dayton RSS390HF. The enclosures are about 83L and with the RSS390HF that'd give me a qtc of 0.810 with the driver taking close to 400w before bottoming out at 20hz according to WinISD.

However, I recently stumbled upon the relatively new Dayton MX15 driver. This driver would have a qtc of 0.701 in the same enclosure while also having a higher xmax and power rating, allowing it to play a bit louder. This driver would bottom out at about 700w at 20hz.

I'll be using a Crown XLS 2502 to power them so switching to a MX15 at this point shouldn't be a problem as it will also fit in the enclosures I have made.

As this is my first subwoofer build I have no reference as to which qtc will give a better end result, all I can rely on is that most people say .707 is the "best" or "gold standard" or whatever.

Which sub would be better for pure sound quality? The RSS390HF because of its aluminum cone and supposed lower distortion? Or the MX15 with its closer to "optimal" qtc?

I'll post some WinISD simulations below. They're both SPL graphs showing the difference in SPL when running them both at 380w and then running them both at the max before bottoming out.

Yellow: RSS390HF, 83L enclosure, 380w, qtc: 0.810
Blue: MX15, 83L enclosure, 380w, qtc: 0.701

Yellow: RSS390HF, 83L enclosure, 380w, qtc: 0.810
Blue: MX15, 83L enclosure, 700w, qtc: 0.701

 

[puppet]

You need to look at each drivers excursion at the required signal level. You can do this in WinISD. Under "signal" (lower left) input the listening distance, pull down the "excursion" tab at the top of the screen and add "system input power" to the driver in watts till you get near the red line that defines the drivers excursion limit. Do that for both, then pull down the "SPL" tab at the top of the screen to see how loud each will be at the listening position. Don't forget to include any EQ you for see using in the "filters" tab as well. This will also increase excursion.

Something to bear in mind is that higher excursion comes with higher harmonic distortion. Some want to stay within 60% of the drivers capability ... depends on driver quality really.

 

[kipman725]

The unequalised response doesn't matter so much, look for excursion capability and the voltage required to achieve it. At the extremes in capability you have drivers like this:

Data-Bass: Subwoofer Measurements

data-bass.com

Data-Bass: Subwoofer Measurements

data-bass.com

 

[Felix2]

You need to look at each drivers excursion at the required signal level. You can do this in WinISD. Under "signal" (lower left) input the listening distance, pull down the "excursion" tab at the top of the screen and add "system input power" to the driver in watts till you get near the red line that defines the drivers excursion limit. Do that for both, then pull down the "SPL" tab at the top of the screen to see how loud each will be at the listening position.

The second graph is just this, but measured 1m from the subwoofer

The unequalised response doesn't matter so much, look for excursion capability and the voltage required to achieve it. At the extremes in capability you have drivers like this:

But the qtc matters? and the quality of the drivers?

 

[Felix2]

Something to bear in mind is that higher excursion comes with higher harmonic distortion. Some want to stay within 60% of the drivers capability ... depends on driver quality really.

So the MX15 would be better judging by this? As it has higher RMS capabilities?

 

[kipman725]

But the qtc matters? and the quality of the drivers?

Not really as long as the drivers motor exerts enough force to get the cone to the required excursion with the voltage available from the amplifier. The driver will have below hearing threshold distortion up to the point some limiting phenomenon occur such as the motor BL falling, amplifier clipping, suspension over tight. Check out these kipple results for a large driver: https://audioxpress.com/index.php/a...s-nsw6021-6-21-neodymium-low-frequency-woofer

Displacement limiting numbers calculated by the Klippel analyzer for the NSW6021-6 were XBl at 70% Bl = 18.8 mm and for XC at 50% Cms was 21.4 mm — which means that for this driver, the Bl was the most limiting factor for the 20% distortion level.

Some drivers however have a lot of mechanical noise at these extreme excursions; but this is mostly an issue for alignments where the driver rear is exposed.

 

[puppet]

Felix2 .. I don't see an excursion graph.

 

[kipman725]

I would recommend using Hornresp to simulate as it can produce a 'Max SPL' graph which shows the maximum output within power, voltage and excursion limits against frequency.

 

[kipman725]

Incidently for a small hit in distortion performance you can just size down the enclosure till your approaching maximum voltage swing to hit maximum excursion at your target minimum frequency. For very strong motored woofers the minimum size box often turns out smaller than is practical to build.

 

[kipman725]

http://www.baudline.com/erik/bass/xmaxer.html this calculator lets you compute the maximum output for a given excursion quickly

 

[Felix2]

Felix2 .. I don't see an excursion graph.

I meant I checked the excursion to find the max power for each driver and the second image is what it looks like when the drivers are bottoming out at like 15 hz

 

[Felix2]

I would recommend using Hornresp to simulate as it can produce a 'Max SPL' graph which shows the maximum output within power, voltage and excursion limits against frequency.

Okay I'll try this
Edit: I have no idea how to use Hornesp so I don't think I'll try it...

 

[ppataki]

As this is my first subwoofer build I have no reference as to which qtc will give a better end result, all I can rely on is that most people say .707 is the "best" or "gold standard" or whatever.

If you are going to apply DSP the Qtc value will not matter at all
I agree with the others before me that you shall rather focus on checking:
- the max SPL at certain frequency(ies)
- and the cone displacement a given driver will have at that freq/SPL (that xmax will be the limiting factor actually)
- and finally how many watts will you need to meet the above in what box size (larger box will require less watts but will consume more space in the room)

All these can be simulated with a box design solution such as Bass Box Pro (that is what I am using at least)

 

[Felix2]

If you are going to apply DSP the Qtc value will not matter at all
I agree with the others before me that you shall rather focus on checking:
- the max SPL at certain frequency(ies)
- and the cone displacement a given driver will have at that freq/SPL (that xmax will be the limiting factor actually)
- and finally how many watts will you need to meet the above in what box size (larger box will require less watts but will consume more space in the room)

All these can be simulated with a box design solution such as Bass Box Pro (that is what I am using at least)

Okay in this case the MX15 will be the "better" driver. I guess I'll just go for that then since it's both cheaper and had better performance.

 

[voodooless]

But the qtc matters?

Not really. You don’t just hear the sub, but also the room interaction, like room gain and standing waves. The resulting response is what determines the sound the most.

Since EQ is sort of mandatory anyway, the Q isn’t all that important. You can better design a box/driver combo for extension and power handling.

 

[jhaider]

Okay in this case the MX15 will be the "better" driver. I guess I'll just go for that then since it's both cheaper and had better performance.

Better how? One is a very nice driver with a cast frame and shorting rings in the motor, the other is an entry level air pump with stamped frame and no indication of inductance control in the motor. So yeah, the latter one might get louder, and if linearity is not your thing I guess that's better.

 

[Felix2]

Better how? One is a very nice driver with a cast frame and shorting rings in the motor, the other is an entry level air pump with stamped frame and no indication of inductance control in the motor. So yeah, the latter one might get louder, and if linearity is not your thing I guess that's better.

Yeah I was thinking about this but I got the impression that I should just go for the one with higher xmax and power handling, which in this case is the MX15.

So for sound quality, the RSS will be the better choice?

 

[kipman725]

Better how? One is a very nice driver with a cast frame and shorting rings in the motor, the other is an entry level air pump with stamped frame and no indication of inductance control in the motor. So yeah, the latter one might get louder, and if linearity is not your thing I guess that's better.

I would counter that shorting rings are not very important for sub bass frequencies as they can't be made thick enough to have effect. Stamped frames also they are associated with cheaper drivers but do they have issues in the sub bass range?

 

[kipman725]

The MX15-22 looks like a great choice for a sealed home use subwoofer as the crucial number "XBL (Klippel verified excursion @ 70% BL) 24.4 mm" is huge, twice as much as an ordinary 15" sub bass driver so in terms of output is like owning two subwoofers.

 

[fpitas]

Yeah I was thinking about this but I got the impression that I should just go for the one with higher xmax and power handling, which in this case is the MX15.

So for sound quality, the RSS will be the better choice?

Depends on how high you intend to cross it. I cross at 110Hz, and I don't need tremendous output below 20Hz, so I chose the RSS390HF.

I'm using the Parts Express 3ft^3 knock-down box, somewhat modified with extra bracing. I stuffed it completely with waste cotton and fiberglass insulation.