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lxmyers 11th July 2013 01:13 PM

ScanSpeak 12" Driver(s) Enclosure?
Hello All,
Really new to this sort of thing and would love a kick in the right direction. I apologise in advance if my terminology is incorrect.

I am interested in building a Subwoofer primarily for use in a Music System (2.1). I was hoping to use the Scan-Speak 30W/4558T00 12" drivers and the matching Passive Radiators (if necessary...).

Unfortunately the room where the Subwoofer will be used is not great acoustically and I don't really have much space for a large enclosure.

A few months back, I had the opportunity to listen to the Wilson Benesch Torus. I had never heard anything like it. It's ability to shake the entire room yet remain completely transparent was remarkable.

I would love to be able to build something that could come close to providing sub20Hz yet still remain transparent enough not to ruin the soundstage.

Any help on this would be greatly appreciated.

Thank you in advance,

Inductor 12th July 2013 06:06 PM

3 Attachment(s)
Hi Alex,
The sub really goes to 20Hz (alignment).
I'm not sure about the Wilson Benesch Torus that I'm not acquainted to or it's specs, but I'm sure I already saw it somewhere maybe a magazine. For some reason they call it Infrasonic Generator maybe it's sound output is severely manipulated/degraded with EQ. But take it as you like, maybe it works. :D
Now thee are a few constraints you have to observe.
Depending of the designs you choose and alignments like so.
First I would say that the "most" (ideal) alignment as a starting point is a bass reflex with enclosure, when we reference volume is going to be for internal volume (net) then you have to make space for ports and others (drivers), of VB = 93.5 L and tuning or port FB = 16.9 Hz. As this port/vent is very unrealistic because of it's practical dimensions you will have to go to the passive driver type of speaker.
Then I will check a different alignment, a BR enclosure like VB = 93.5 L tuned to FB = 20.3 Hz with a more plausible port like 4"diam. and 47cm length. You see this a very long port that's why to use in addiction the passive you mention.
Let's say that in the limit (reduced dimensions) you go to the small box of 43 L net, then you are above the 26Hz LF threshold not the 20Hz you mention, what is in practice the same for a good audiophile experience. This is specs for the passive radiator because as was said of impractical dimensions and air speed in the port. You can pair it with the 30W/0-00-00.
The sonotubes are also used with this driver, some on this forum.
A moderate enclosure would be a 80L. As in the more squeezed kits that I consider a minimum for the SCANSPEAK 30W/4558T00, VB = 43.0 L, FB = 18.0 Hz.
This type of enclosure (passive kit) can really go to infra sound at the low frequency extensions /10Hz as you think, and want it does. :cool:
30W/4558T00 - Scan Speak Discovery 12” subwoofer 4ohm - Europe Audio
30W/4558T00 'Discovery' Scan-Speak [30W/4558T00] - €189.00 : AUDIO-HI.FI, Loudspeaker shop
Scanspeak 30W 4558T00 Discovery
The Madisound Speaker Store
Strassacker: Speaker Building, Components
New sub build: Scanspeak 12" 30/4558t00 in 80 liters | - UK Online
Wilson-Benesch Owner’s/Admirer’s Circle

lxmyers 13th July 2013 12:41 PM

Hello Inductor,
Thank you very much for replying, that is almost an overwhelming amount of information. (I think I may have bitten off more than i can chew...)

The last enclosure (43L with a 26Hz FB) that utilises the matching Passive Radiator seems potentially suitable but I am a little confused regarding the variation in FB or frequency. How is it that the frequency can vary from 32Hz to 10Hz? (listed on the graph)

Thank you again for your help so far.

King Regards,

Inductor 13th July 2013 01:37 PM


Originally Posted by lxmyers (
How is it that the frequency can vary from 32Hz to 10Hz? (listed on the graph)

That's from the roll-off in this case -3dB (F3)/ -24dB (F24), characteristic of the (43.0 L/18.0 Hz) specif alignment used. Not considering the room gain. :)

GM 13th July 2013 05:12 PM


Nice driver! Vented requires a PR or TQWT alignment [inverse tapered TL] to go low with a 17 Hz [Fs] being a good tuning point [Fb]. No clue about the Torus or what ‘transparent’ means to you, but this driver’s very low inductance [Le] and reasonably low power requirements will surely help, ditto a very low tuning that in most HIFI/HT apps is low enough to blend well with room gain.

The TQWT will be higher sound quality [SQ] due to its much lower group delay [GD], flatter phase response and depending on the XO point/slope could be somewhat more efficient in the bass due to needing less internal damping.

What are your floor space restrictions? How high can it be? How much power is available to drive it? Desired XO point/slope?


lxmyers 14th July 2013 01:03 PM

Hi Guys,
Room gain, thats a new one... The room where the subwoofer will located unfortunately is not the best for this sort of thing. It is not rectangular (sort of a squared off "s" shape), has wooden floors and furniture every where it fits. (including a rather large couch) Is there a equation for roughly calculating Room Gain or does that need an Acoustic Analysis package?

Floor space is a bit limited, I have two options. The first is a space between the couch and the wall, it is roughly 165L but the only surface not covered by either the couch or the wall is only 10" x 22". The second option is a small area on the other side of the room, the 43L cabinet mentioned by Inductor would be about the limit for that space.

Would an Isobarik configuration help with the space requirements?

Sorry guys, not as versed on the terminology as I should be. By transparent I meant very low distortion(?) or no port noise, I was not able to localize the subwoofer so the sound stage remained intact.

Cross-over Point and Slope, another new concept. The main speakers are Rega XEL's, from memory their frequency response was something like 40Hz to 20kHz. Is there an equation for calculating the XO parameters or does that need to be calibrated per room?

Not entirely sure on amplification at this point, that would have probably been a follow up question. I was hoping a 500W Plate Amp would provide adequate power. Any recommendations on a suitable Plate Amp?

Thank you again for your patience so far, a really have very limited knowledge and this is a considerable help.

ODougbo 14th July 2013 01:43 PM

I don't think a Iso is necessary - I'd go for the 2.5cf vented box, with a slot port.
#4 suggestion - The Madisound Speaker Store

Inductor 14th July 2013 06:44 PM

I would do that, very close to the 80L I mentioned in post #2.
2.5ft³ = 70.792L

A moderate enclosure would be a 80L

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