BK Monolith Subwoofer - the 500 watt version


New member
Aug 10, 2019
Hello everyone I wanted to upgrade my Mordaunt Short MS-309 sub because I wanted a fast sub that was effortless and without the horrible class D amplifier and heavy metal cone woofer.

         After perusing the web for a British built sub (less shipping costs/better service) etc I decided on a BK electric Monolith forward firing unit but I wanted a substantial upgrade over the MS so I got the custom version with a 500 watt MOSFET panel amp as used in REL and M&J subs with an Eminence LAB-12 12 inch woofer in light oak.

I realise that this is an over the top subwoofer for a bedroom - it has no bed because it's another living room upstairs used for hi-fi.

From what I can gather the 300 watt version of the Monolith is not that far behind a £2500 REL subwoofer and the "breathed-on" BK with bigger amp and better drive unit should be mega - it's on order and Tom at BK electric was very helpful and answered all my questions over the phone.The sub is huge and heavy at 110 lbs so it will be a 2 man lift.The Monolith is very well built out of 1 inch MDF and is critically braced with a beautiful rounded cabinet with matched real wood veneers; the equivalent build quality would cost thousands and be half the weight and probably made in China.I will review it here in a couple of weeks.

I was assured that the twelve inch woofer is bomb-proof and with a massive double magnet and light paper cone so will be responsive and fast compared to a metal woofer.The model down is measured at -3 db at 15hz and over a 100 decibels so this beast should be fantastic.The woofer alone weighs more than 22 lbs or 10kg.

I only watch films on the PC (I've got a 24" full HD monitor and Acoustic Energy Aego-M, Tannoy SFX centre with decent cable and separate good quality sound and graphics card and a separate preamplifier for switching and phones for the PC) and I don't watch my 28" Toshiba or 32" 100hz Panasonic Widescreen CRT for months at a time.I don't like the telly on much.

I prefer music and have a Sugden A21a integrated amplifier, Sugden Audition CD player upgraded to CD21 class A output spec with a Traxdata 900 cd recorder, Technics RS-AZ7 3-head cassette, Sony WMD6 Professional Walkman cassette, Musical Fidelity X-Cans headphone amplifier, Sennheiser HD-600 headphones, Linn Axis - Basik - K9 turntable, arm, MM cartridge on an Apollo Aria 5-tier rack.

Speakers are SD Acoustics OBS 3-way dipoles with Volt bass, Dynaudio midrange and top of the range Scanspeak tweeters with solid silver wired computer designed crossovers (tri-amp/tri-wired) from Wilmslow Audio and are heavily braced and customised.

Interconnects and speaker leads are QED, Cambridge Audio and Linn and the tuner is a DAB/FM shoebox Onkyo CR-505 DAB CD receiver.The remaining speakers are Mordaunt Short MS-902 and Mordaunt Short MS-302 on two foot high, heavy Partington speaker stands.

I do realise that I need to upgrade most of my kit as it's so old and friends tell me to get a big AV receiver with loads of speakers and a big thin new tv but I don't need them as I mostly listen to music.


Wow, sounds pretty exciting. I'd love to try a sub on that scale but I don't really have the room to hide it and the neighbours would probably start disliking me. Any chance of some pics? Sounds like you have some really interesting kit. Cheers for sharing.


Well-known member
Dec 30, 2007
Speakers are SD Acoustics OBS 3-way dipoles with Volt bass, Dynaudio midrange and top of the range Scanspeak tweeters with solid silver wired computer designed crossovers (tri-amp/tri-wired) from Wilmslow Audio and are heavily braced and customised.

I am very jealous. Of all of it. But mostly the speakers...

Awesome setup!


Thanks igglebert and Dougal1331 - I've got the HI-FI kit upstairs because I wanted the downstairs living room to have no television or hi-fi - just for conversation, games and jams on guitar.

I think that the dipole speakers are a bit "homemade" looking which they are haha.My ex said that they looked like 2 black tombstones and I thought they were ugly as anything being nearly four feet high.

They do sound gorgeous though - very fast transients - no boom or tizz or midrange peaks - they disappear aurally - ie - the music is totally out of the box. They have sound height, front to back depth and a massive "walk-in" soundstage heard from anywhere in the room.This is probably because they radiate backwards and forwards rather like an open pair of headphones.

The speakers are SD Acoustics OBS - open baffle speakers and they've been heavily customised - 8" volt bass, 6.5" dynaudio midrange and top of the range scanspeak 1" soft dome tweeters with custom made outboard 3-way solid silver-wired crossovers.They can outperform much more expensive designs.On their own they have good deep bass below 35hz but a sub should really make them sing.

The BK Monolith is on order and should be here by the end of the month.Unfortunately I have no pictures as my cameras went in a burglary and I only have pics of part of my setup from years ago.


Here is a bit of the hi-fi


The sub is big but needs to work less than a smaller one and will not be overpowering if one is sensible with the volume.

I got a picture of the Monolith from the net.The woofer is 12 inches to give an idea of scale.

The specifications are :

Bk Monolith (Custom)

Manufacturer: BK Electronics
Model: Monolith
Provided by: Marek Sound
Manufacturer link: BK Electronics
Price: £570 with uprated BSBPV500 Panel amplifier and Eminence LAB 12 Woofer, Soundcare SuperSpikes including packing and delivery.

Manufacturer specs:
System Type: 95 Litre reflex tuned to 20Hz, cabinet manufactured from veneered 25mm MDF and Critically braced
Distortion: 5% 102dB @ 20Hz - ( the custom unit should be 2-3 db louder and deeper )
Frequency Response at -3dB: 20Hz / In Room at 15Hz
Amplifier Input / Output Impedance: High Level 100K - Low Level 10K - Balanced 10K
Gain Control Range: 80dB
Drive Unit Impedance: 4 Ohm
Mains Input: 230V / 50Hz
Dimensions: 560D X 540H x 420W - 22 inches Deep x 21 inches High x 16.5 inches Wide approximately
Weight: 50.00kg - 110 lbs
Finishes: Black Ash Veneer, Light Oak Veneer and Cheery Veneer
True 500W continuous discrete Mosfet amplifier
Truly hand built in Great Britain, when we claim hand built we mean hand built, as there are no SMD components or other automatic placement devices
Forward Firing 300mm (12") - Eminence LAB 12 Woofer
Continuously variable frequency control
Audiophile grade toroidal transformers
Gas Tight Neutrik connection for long term consistency of sound quality
Separate controls for high and low-level input adjustment
Simultaneous connection of high and low level sources
Balanced Inputs
Thermal Protection
Anti Thump
ASP automatic speaker protection audibly transparent driver protection
4 x 16A output devices for effortless current control
IEC Power Socket
Doubled flared 4" port for reduced port noise

Configuration as tested:
Phase: 0 degrees
Front grill removed
Orientation: Woofer/port facing right




Well-known member
Dec 30, 2007
Yup- those speakers look as awesome as they undoubtedly sound! I love all the DIY stuff- I've built a couple of sets over the years with varying degrees of success. (Not kits, but own-design- have now realised that this sort of thing is best left to professional speaker designers!)

I like my speakers to look like they mean business- give me a pile of high-spec ugly drivers over chamfered-edge, real wood veneered craftsman-sculpted wonder cabinets any day! I love the look of my 753s, although they need more work on the crossover side of things (mid/treble crossover a touch rough), and have taken a back seat again, while my 601s do some work for a change...


I realise that this is an over the top subwoofer for a bedroom - it has no bed because it's another living room upstairs used for hi-fi.

I only watch films on the PC

1. Understatement of the year, dude!!!

2. 500 watt sub but you watch 'tv' on a computer?



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