Dual XLS-12" sub design, cracked it? thoughts?

[Sjoerd v L]

Idea:
Subwoofer with good output; 15Hz-40Hz for music and 15Hz-60Hz for movies.
Port only active in lower regions to prevent smearing.
No port noise.
Low Q. Low group delay.
Netto box volume max 110L.

Design:
2x Peerless XLS 12
Box 110L netto, small amount of fill, tuning frequency 11Hz
1x tube 11,1cm inner size, 209,4cm length
1x 240W NAD214 amp

Pro's:
good output <20Hz
1st port resonance 82Hz
cone excursion limit only reached below 9Hz with 240W
low group delay 25ms at 12Hz
Air velocity in tube 17m/s at 240W at 10Hz
Reasonable box size.


I'll post the screens from winisd.
Any thoughts about this design? Did I miss something?

Sjoerd

[Sjoerd v L]

SPL 240W

[Sjoerd v L]

transfer function magnitude

[Sjoerd v L]

cone excursion with 240W

[Sjoerd v L]

Air velocity in the tube with 240W

[Sjoerd v L]

The first room resonance is at ~28Hz, so I expect higher output below this frequency. With an active crossover and correction filter, I expect a flat response till well below 20Hz. (15Hz?)

Sjoerd

[Sjoerd v L]

and nearly forgot group delay...

[paulspencer]

Looks to me like not much different to a pair of sealed subs, which would actually give you more flexibility. This might not be the response you are looking for, but why not just use a pair of small sealed subs with a LT? They may give you a better in-room response that way, or if placed next to the mains they may give a better integration since distortion products will be close to the mains. Distortion can cause localisation problems with any subwoofer driver.

I've had bad experiences using NAD power amps with subwoofers. I powered my pair of drivers with a 2100 and watched firewords inside the amp when a transient hit. It just blew up! I would be very wary of this. The XLS is very easily powered with a moderate and affordable plate amp.

In room response is difficult to predict. I have simulated my room, and I have used measurements and they are nothing alike! Keep that in mind. You need something fairly sophisticated to deal with room modes like BFD.

How are you going to switch between music and HT mode? I'm not sure the difference will be worth the hassle in the long run. I've seen (and more importantly, heard) the XLS used in ultra high end cost-no-object speakers and they are great drivers. Done right they should sound very accurate.

I can't see anything wrong with what you planned, or anything you missed as such. I'm just suggesting alternatives.

[BassAwdyO]

looks like a great box to me.... except your rolloff is a bit steep. A bigger box would help with that, but it also lowers the dampening on the cone which will increase excursion at lower power levels. I'd say virtually what you have there is a sealed box with an extra few Db from 11-13hz or something. I like it. It should sound very musical indeed.

[Sjoerd v L]

Thanks for the response.

Originally posted by paulspencer
Looks to me like not much different to a pair of sealed subs, which would actually give you more flexibility. This might not be the response you are looking for, but why not just use a pair of small sealed subs with a LT? They may give you a better in-room response that way, or if placed next to the mains they may give a better integration since distortion products will be close to the mains. Distortion can cause localisation problems with any subwoofer driver.

What do you mean with LT? Transmission Line?
Thought about it; it has two downsides:
-a large box
-haven't found the right simulation software

I've had bad experiences using NAD power amps with subwoofers. I powered my pair of drivers with a 2100 and watched firewords inside the amp when a transient hit. It just blew up! I would be very wary of this. The XLS is very easily powered with a moderate and affordable plate amp.

I'm thinking about buying a plate amp, but currently I'm using another XLS-12 sub (single driver) and it works out great.
The NAD214 has softclipping, so I'm probably save.

In room response is difficult to predict. I have simulated my room, and I have used measurements and they are nothing alike! Keep that in mind. You need something fairly sophisticated to deal with room modes like BFD.

I agree, I want to build a crossover + correction filter.
Possibly with a notch filter for the first resonance.

How are you going to switch between music and HT mode? I'm not sure the difference will be worth the hassle in the long run. I've seen (and more importantly, heard) the XLS used in ultra high end cost-no-object speakers and they are great drivers. Done right they should sound very accurate.

With the filter mentioned above, I should be able to switch between crossover frequency easily.

I can't see anything wrong with what you planned, or anything you missed as such. I'm just suggesting alternatives.

Thx