Big Box XLS200?

I was just wondering ( ) what you guys thought about BK offering a larger cabinet for the XLS200. I've gathered that the more cabinet volume a drive unit has the better it seems to perform. I've seen a comparison between the original few subs that BK offered (SDA-XLS10) that had slightly larger cabinets and it was said to sound better than the XLS200 so what if BK could be tempted to design a significantly larger cabinet option for all us XLS200 owners. It would be a simple case of us installing the amp plate and driver into the new cabinet which is easily done.

I realise allot of people bought these subs because of their small size/footprint but a larger cabinet doesn't have to mean a large footprint as the extra volume can be incorporated upwards as is the case with the SVS cylinders. Also it would give them another sub addition to the XLS200 family.

So what's you opinions on this good or bad?

 

Sounds like a good idea. They could also make it ported like the MS309 as well as make the box bigger. Let the peerless driver really show what it can do.

 

A bigger box would certainly be interesting, as you say, there were a couple of earlier models and some one-offs that were larger and used larger drivers/amps.

I suppose the problem with making the cabinet larger is that the bracing will have to be significantly improved making manufacture trickier. Also remember that there's a 12" version of the Peerless driver (the XLS12) and I believe that there's an uprated version of the driver although I've not seen that in this country.

I'm not sure if venting the cabinet would be a good plan as some more aggressive driver protection circuitry will be necessary. I have it on good authority that the XLS200 incorporates no low level EQ to boost response and no infrasonic filter to protect the driver from over excursion. As the cabinet is sealed, over excursion isn't a problem (the trapped air acts like a spring) and the speaker protection circuit in the plate prevents driving it too hard. Basically, a complete redesign of the amplifier plate would be needed to do this. The amplifier doesn't start to rolloff until ~8Hz (DC protection presumably) and I've measured a reasonably flat response down to the low teens in frequency terms. I have to admit that I've no idea what BK have up their sleeves though, they certainly have plenty of options and who would have predicted the downward firing version?

Bear in mind that it was only a year or so ago when stock was extremely limited as they were originally only produced to help use up a surplus amount of the drivers!

If you're after better performance you can't go wrong with adding a second to make a stack. Useful output now extends down to the low teens and the power on tap is phenomenal, I can feel waves of air hitting the side of me in my listening position! Basically, it improves everything that a single might be lacking in spades and (if they're stacked) retains the same small footprint.

 

A bigger cab,driver and amp would prob all be great but i would think to make it a ported sub would make it a different beast altogether

 

What's the point? I mean, we already have PB10.

Isn't the compact size it's main benefit on the market? You can always make the cabinet yourself, Peerless is a DIY-driver for many. Just my opinion..

 

Eviljohn,

So according to your post it's not as simple as just designing a new cabinet. You mention the need for an infrasonic filter on a ported design but is this feature common on ported designs? Is the EQ necessary too?

As far as using two subs how come you now get output down in the low teens? I would of thought that adding another sub would just give more bass weight I certainly didn't expect the frequency output to drop lower! I get a flat reading in my small room of 22Hz using one sub. Also at what volume level do you start feeling the waves of air? With mine I can start to feel the waves at around -10db but thats just a bit too loud!


Docta,

I agree a 12inch peerless unit, 300W min amp and a large ported cabinet from BK would be a dream. SVS rival for sure


Diamond,

My DIY skills aren't that great that I can put together a solid enough cabinet for a sub I can just about use a soldering iron . Also I believe it takes some skill to design one that doesn't have port chuffing issues. Besides I don't think I'll have the time once I get hold of (hopefully) the speakers I've wanted to own for a while now. They need plenty of TLC as they're in a bit of a state.

 

Mmmmm, im thinking dual stacked PB10's Now that would shake the foundations

 

Can I ask a dumb question please !
How to you attach 2 subwoofers to an AV Amp ?

 

With y-cable I believe. It makes one rca go two ways.

 

Grinder,
It certainly isn't quite as simple as putting the lot in a bigger cabinet. A bigger sealed cabinet should work fine although I'd be inclined to put a larger amp panel on in this situation purely because the additional space would be available for it but that's a different story. You're right that using a larger cabinet should increase performance to some extent.
As sealed subs are airtight, the pressure inside varies as the driver moves in and out. This difference in pressure either side of the driver always pushes the driver back to the equilibrium position thus preventing over-excursion unless you're seriously overdriving the unit. In this case the speaker protection in the BK amp panel will cut in.
This equalising force (caused by the difference in air pressure either side of the driver) doesn't exist in a ported cabinet so the driver can quite happily travel as far as it wants. This is far more likely at lower frequency levels in this case so an infrasonic filter is usually incorporated to help prevent the situation and potentially damaging the driver. The infrasonic filter just cuts low frequencies so has the effect of reducing overall extension.
You're right that adding an additional sub doesn't increase the depth a subwoofer can reach but it does significantly increase headroom (ie. the amount of power available, usually by ~6dB). This has the effect of significantly reducing distortion at all levels as neither unit is being driven as hard. The BK actually has output down to these deep levels but it distorts quite heavily and isn't particularly impressive with the single unit. I've posted some graphs in my "Dual Subs" thread which should help demonstrate this. It really is a stunning unit and becomes several times better when you add another one. You're right that you don't really feel the bass from a single unit unless it's turned up very loud, adding the second really makes a difference[/b]/
Just bear in mind that every sub design type (sealed, ported, isobaric etc) is a compromise in some way.

JohnG,
Y-splitter is definitely the best way in my experience although there are a few other options such as connecting the second to your centre pre-out or main pre-out. It depends what effect you're after really.

 

Well I'm just about to join the subwoofer clan - I ordered an XLS200 yesterday, so I may look at getting a 2nd one sometime in the future

 

Eviljohn,

Thanks for the detailed explanation. I don't think it would be a good idea then to simply put the parts in a bigger, ported enclosure as without the protection circuitry it would risk the sub bottoming out (?). A larger sealed enclosure would be ideal but would a bigger amp really be necessary? I would of thought most users wouldn't get anywhere near using the full capability of the existing amp. I can however see it helping to reduce distortion at higher levels though (?).

I may need to buy another sub anyway as the speakers I've just bought (Magneplanar SMGa's ) aren't renowned for their bass extension but I'll see once they're fixed up. I think two subs for my HT would be too much of an extravagance right now but who knows . Anyway we'll see what BK have to offer us in the future. I think it's about time Ruark replaced that ageing CL300 of theirs don't you reckon? .

JohnG,

You won't regret it, the XLS200 is a cracking sub for the money. A real bargain.

 

Grinder,
I think you've got it.
You're right that the bigger plate amp wouldn't be necessary but it certainly wouldn't do any harm particularly at higher levels. You've also got that using a ported enclosure isn't quite as simple as drilling a hole in the box! You also need to consider tuning the cabinet with the port length, shape and diameter. I gather that the SVS PB10 is actually tuned to below 20Hz.

I think it's worth emphasising here that neither sealed nor ported cabinet designs are "better" than the other. They each provide different characteristics, trading one benefit for another.

A sealed sub won't have the same outright "extension" (ie. the -3dB point will be at a higher frequency) but the rolloff below the 3dB point won't be sharp.

A ported sub will extend slightly deeper but output will severely drop off below this.

Other design choices include using an Isobaric design or using a passive radiator although the costs of design and manufacture mean they're not really seen at the lower end of the market.

John, You're going to be really happy with the BK. Let us know how you get on.

 

One can always buy a ported one, and stuff it. Can't recommend any models, but with PB10 it seems to work well. These are measured in Ilkka's room.

Here it's ported.


And here it's sealed.


Referring Illkka: "Sealed version had the same extension but it was more "musical". Tight and not boomy at all."

Pretty good without EQ'ing. He said it's tuning point is 17.5Hz.

 

Hi Grinder
My DIY sub uses the Peerless 12" XLS in a 1.27 cu.ft. cabinet w.14" d.12" h.24" which I feel is an acceptable size. Any larger then internal bracing can become a problem. It is a critically-damped closed box with a 200W. amplifier. Frequency response is down to 10Hz. at -6dB. The amplifier is heavily modified especially in the sub-sonic filter which is still under development as care is needed to avoid over excursion with LFE sources, although ok so far.
Currently testing it against the relatively huge Tannoy RSUB-15 which is only in the lounge for test purposes. (I normally use it on my Hammond electronic organ in another room.) If BK were to produce a 12" version of the XLS200 then that would be interesting. The Peerless XLS speaker range is highly rated in the DIY area.

sonic65

 

Shake em? You'd probably need to find a new home


Eviljohn,

Thanks again. If nothing else turns up from BK in the near future I will have a go at making a larger sealed cabinet myself. Nothing professional just something that will show what benefits can be gained from a larger enclosure. It's only cheap MDF after all! It will have to wait though till my speakers are fixed in a couple of months time.


Diamond,

That graph looks very impressive considering no EQ was used. Must have a largish bass friendly room or is that typical with SVS's? Mine has a couple of nasty peaks, which I can swear are audible, one being 15db above level.


Hi Sonic65,

Your modification of the amp interests me greatly as I've always wondered what can be gained from upgrading things like opamps and capacitors especially seeing as I can use a soldering iron. I can't see there being much else to change though . Did you start off with a BK amp and what mods have you done to it so far and also what improvements have you noticed after the mods you made. What exactly does critically damped mean? (sorry).

 

No, it's not typical, at least in that measure. It's really a small room, about 9 x 10' room. It was placed between the Emerald 97s, a nice spot for bass. The smoothest I've seen.. And it really bounced with Master and Commander.

(My room is a different story, but BFD is on its way)

 

Hi Grinder
No not the BK amps as I wasn't aware that they had plate amps at the time. Plate amplifiers appear to be made by quite a few manufacturers, Parts Express, Jaycar, and MCM for example. I chose MCM because they willingly emailed me the full schematic diagrams which were needed for in-depth circuit modifications.
My RSUB-15 has developed a loud hum and Tannoy will not (for whatever reason)supply the circuit diagrams. Okay I will be able to manage without for this type of fault. What I am saying is get the technical info first and then buy the amp, not the other way around. In the past BK have been very helpful and have supplied me with circuits but check first, as policies change and most suppliers will refuse.
The Critical Q subwoofer is described in detail on the following website:
http://members.ozemail.com.au/~joer/sub_index.htm (Must find out how to patch a live web address, sorry)
I used the info therein as a basis for my circuit changes but have varied component values to obtain the results I required.

The modifications on my amp are:
(1) Increased gain on input op amps (I needed the extra power output)
(2) Sub-sonic cut-off filter lowered in frequency to extend LF resonse.
(3) Input capacitors changed from electrolytic to audio grade.
(4) Added additional low pass filter circuit.
(5) Feedback loop capacitor changed from electrolytic to bi-polar.
(6) Crossover filter- frequency lowered.
(7) Switching for extended LF (music/movie mode) in process.

Results are dramatic even at 5Hz. the cone movement was energetic to say the least, so I changed some component values temporarily to obtain 10Hz. at -6dB. (to play it safe on LFE sources.) Using AB switching I tested my sub against the RSUB-15. I used the switch blind so I did not know which sub was selected to remove any pre-conceived ideas. Overall the differences were not as great as expected, as I thought the RSUB-15 would walk away with the prize. Okay the tests were purely listening at this stage but my sub sounded deeper, cleaner, better transient response, and importantly, more musical, more Hi-Fi. It soon became apparent which sub was operational. The bass could be felt even at moderate volume. This was on CD music sources. A DVD movie source with LFE is yet to be evaluated.
The Q value or magnification factor at the box resonance can have a range of say around 0.1 to 10. Where 10 is a highly peaked response and 0.1 falls off sharply. Where there is a resonance, if the Q is kept down to or below 0.5 it can be described as critically damped. I think the term originated from the Linkwitz-Riley 2nd. and 4th. order crossovers having a specified Q of 0.49, again this is mentioned in the above website. Hi-Fi buffs usually like a Q of 0.7 for a smooth bass but that is very different from from an equalised sub-bass. All the above is based on using the Peerless XLS 12" loudspeaker which costs around £150 so great care is needed. I tested my amplifier into a 8 Ohm resistive load, and only when satisfied did I connect the speaker.

sonic65

The above website will error if clicked....Perhaps easier to search on Google.
Type in "Critical Q"

sonic65

 

Thanks sonic65 for the link and the info.

I think all those mods are a bit extreme for me at the moment. I think I will start with trying a larger cabinet first then if need be have a look at changing a few of the more critical parts in the amp plate that affect the sound quality the most. Caps first as they seem to be the easiest to replace for a novice like myself then try some different opamps, although they look quite difficult to change over. The amp plate itself seems to be of a good spec but I just want to see if there's any room for improvement with a few choice part replacements. I'm basically looking for improvements in resolution (and detail) and the ability to 'feel' the bass at lower levels aswell as getting a lower output.