Drivers Concentric

Coaxial drivers for home audio applications have been a staple in the industry for a number of years, especially designs that are similar to the KEF Uni-Q/Tannoy Dual Concentric products where the tweeter is located at the location normally reserved for a dust cap. They utilize a relatively large 1.75' compression driver that can go a bit lower than a run of the mill 1' tweeter. The concentric arrangement serves as a waveguide to the tweeter, narrowing its dispersion pattern. Find many great new & used options and get the best deals for Tannoy Pair of Monitor Gold 15' Speakers Drivers Concentric Loudspeakers great! At the best online prices at eBay! Free shipping for many products!

  1. Drivers Concentric Model
  2. Drivers Concentric Definition

Loudspeaker science has made some incredible progressions since the daysof the phonograph and quite frankly, we're living in a marvelous timeto be an audioholic. Professionally listening to and evaluating loudspeakers over the last 15 years or so has given me a perspective which isn't without its downside. I often getthe question “What are the best speakersin the World?” from fellow Audioholics and/or from family or friends. I typically tell them that it really dependson the situation. Of course, peoplethat don’t know audio are often surprised when I DON’T tell them Bose is thebest. I usually retort that “best” and“most popular” are often not synonymous, and a few analogies outside of audiooften help them to understand the lack of relation such as: Beer:Budweiser, Pizza:Dominos and Burgers:McDonalds,etc.

I don’t liketo be boxed into a corner of declaring an absolute best, even when the type ofspeaker and the application are known. Price is NOTalways a contributing factor, but it usually correlates with sheer outputcapabilities, low end bass extension, and nicer build quality when comparingspeakers from competent speaker brands. However, if you want it all, it's usually going to cost some serious coin. Performance, aesthetics, budget, pick two. That said, I’ve conjured up with a list ofvery notable designs for each category type that we’ve come to know, love andrespect over the years.

Feel free topost your favorites or voice yourcomplaints in the related forum thread on this site.

Bookshelf Speakers: Salk Silk

MSRP:$3,495/pair moreinfo

Who doesn’tlove a speaker that can throw off a life size image from a pint size box? We were completely floored upon first listenof the Salk Silk bookshelf speakers at the Audioholics 2012 GTG Event. Their ability to present a soundstage of alarge tower speaker with the delicacy and precision inherent in a small speaker was mostimpressive. The RAAL tweeter was silkysmooth like the name implies, and anyone who has seen a Salk speaker up closeknows that their fit and finish is second to none. These are wonderful speakers for a nearfieldmonitor application, or used in conjunction with a high quality subwoofer for a 2.1 channelsystem. If you want more output and bass extension, Salk has larger floorstanding models that are equally impressive in their performance and aesthetics.

JBL M2 Master Reference Speakers

Horn Speakers: JBL M2 Master ReferenceMonitors

MSRP:$20k/pair moreinfo

The JBL M2 isa revolutionary new horn speaker design that is said to produce the bestFrequency Response results on the 360 degree spinorama at Harman. Their waveguide dubbed 'Image Control'provides neutral off-axis frequency response and is touted to be one of theworld’s most accurate loudspeakers. The D2 compression horn driver is crossedover at 800Hz, and everything on down is sent to their 15” woofer. Both thetweeter and woofer utilize dual voice coils for increased power handling andheat dissipation, which is why these babies are able to muster up a whopping123dB output at 1 meter. The systemcomes as an active solution with Crown amps and has enough SPL capability tomake Grandpa Simpson’s teeth explode with ease. If you’re a horn lover, it is doubtful you will find a speaker that canbetter the neutrality and dynamics of the M2 monitors. If you can't manage the enormity of these speakers for your room, check out JBL's new 7-Series which feature the same horn technology and much of the trickle down technology developed for these speakers in a much more compact form factor.

Status Acoustics 8T Modular Speaker System

Modular Floorstanding Speaker System: StatusAcoustics 8T

MSRP:$50k/pair moreinfo

It isn'toften that I review a product that fundamentally changes the way I listen andexperience audio. Status Acoustics, the premier line of RBH Sound, has managedto do just that with their flagship Titus 8T floorstanding loudspeakersystem. The sound of this speaker systemtranscends their physical cabinets, being grandiose and in your face whencalled to do so, yet delicate like the petals of a rose beckoning you tocarefully listen, rewarding you with pure unadulterated audio perfection. The bass response is epic thanks to the three10” high excursion sub drivers in each cabinet, which allows these monsters toexceed the Audioholics Extreme Bassaholic rating. The 8T’s are truly what I consider to be“speakers for life” and why they are the reference speakers in the AudioholicsShowcase Home.Be warned, these speakers are huge and heavy, tipping the scale at over 350lbs each. RBH Sound does offer a fabulous bookshelf version called the Status Voce Fina but it's uber expensive.

Point Source Speakers: KEF Blade

MSRP:$30k/pair more info

Billed as theworld’s first single apparent source loudspeaker, the KEF Blade is nothingshort of a technical marvel. The key to the Blade is an advanced UniQ driver, aconcentric design that places a 1” aluminum dome tweeter at the center of a 5”Li-Mg-Al/LCP hybrid cone. Covering the low end, the UniQ array is flanked by noless than 4 – 9” woofers in a dual-opposed, force-cancelling configuration. Thenthere’s the unique cabinetry to discuss: suffice it to say, the Blade isn’tjust another boring box. The shape is unique, being optimized to minimize theeffects of diffraction. We also note that there’s no MDF here; instead, KEFutilizes a stiff glass-reinforced composite material to ensure you don’t hearthe cabinet humming along. If you don’t happen to have $30,000 to spend, youcan still rest assured that technology from the Blade hastrickled down to KEF’s Q, R, and Reference series speakers.

MartinLogan Neolith Speaker System

Electrostatic: MartinLogan Neolith

MSRP: $80k/pair info

There is a cult following of audioholics that live and die by electrostatic speakers, and for good reason. A really good ESL literally beams the sound into your head unlike a typical conventional cone driver speaker system is capable of doing. Neolith is a bold new loudspeaker, the product of an ambitious 3-year-long development process that combines the very best technology MartinLogan has to offer. Neolith features MartinLogan's largest-ever electrostatic radiating surface. Its proprietary curvilinear electrostatic transducer is allows the speaker to deliver an enveloping three-dimensional soundstage. Unique Controlled Dispersion Technology gives each transducer the ability to reproduce nearly the entire audio spectrum in any room. Neolith loudspeakers embody the MartinLogan ethos, and achieve 'living sound'; revealing audio as it was originally performed.

Whatabout Budget Designs?

Noteverybody has thousands of dollars lying around to buy a high performancespeaker system. So what about the budgetstuff? Typically you can still get really goodsound from budget gear if you use it within its design limitations. It's usually a good idea to pick small speakers, bass manage them, and let a dedicated subwoofer handle everything 80Hz and below. This is especially true if you're also integrating your speakers into a multi-channel surround system. Well engineered budget products are a special breed because they give folks a taste of good audio in hopes they'll one day refine their palettes to upgrade to the next level and beyond. As an avid beer enthusiast, I'd often give Bud drinkers a Samuel Adams Larger to get them started on the path to better beers. It usually isn't too long before they develop a taste for a fine USA made microbrew beer or a Belgian Ale.

NHT 2.1 Super Stereo System (left pic) ; Pioneer SP-FS52 Tower Speakers (right pic)

Affordable 2.1 Speaker System: NHT Super Stereo

MSRP:$499/set moreinfo

What happens when you add NHT's Super 8 subwoofer totheir legendary SuperZero bookshelf speakers? You get the Super Stereo system:a reasonably efficient, compact, high quality 2.1 setup perfect for small rooms. The best part is theprice. For under $500, you get acompetently designed speaker system that is great for two-channel audio and/orbuilding a modest surround system with high spousal acceptance factor. Use these as an alternative to the popular cube speaker systems!

Affordable Towers: SP-FS52Tower

MSRP: $258/pair moreinfo

Drivers Concentric

They’re fugly, they don’t hityour chest with thumping bass, or part the Red Sea. Yet, I can comfortably say that I’ve neverheard or measured a better balanced, better sounding tower speaker for under $500/pr thanthe Pioneer SP-FS52 speaker system. This 2 ½ waytower speaker features (3) 5 ¼” mid bass drivers, a 1” silk dome tweeterflanked in a waveguide to improve dispersion and lower end efficiency all matedto an 8-element crossover. Pioneer hiredAndrew Jones (the same speaker designer of Pioneer’s high end TAD brand) tosqueeze out every ounce of performance on a shoestring budget. Missionaccomplished!


Are these the “best” speakers out there? I’m not sure anyone can answer that. In my opinion, our selections do represent state of the artperformance, and design from what we’ve seen. However, we recognize there are so many other great speakers out there from the likes of Aerial Acoustics, Focal, Legacy Audio, Revel, etc etc. Speakers have really evolved over the last 20-30 years. There are more excellent brands and products today than ever thanks to the wealth of knowledge available on loudspeaker design philosophy, modern developmental tools via computer software, and established measurement techniques and practices; all of which help govern good design practices.

No matter how much science one wishes to throw at quantifying the 'best' speaker, one must also realize we aren't robots. Even Spock would agree that logic is only the beginning of understanding, not the end. We can't fully objectify our subjective preferences. While accurate sound reproduction can to a large extent be quantified, there is also a highly emotional response to how we listen to and enjoy music. What may be best for my needs and ears may be completely different for yours. Pick the best speaker system you can afford but most importantly, pick the ones that sound right to you. The 'best' speaker system should elicit an emotional response that just begs for you to listen more intensely to rediscover your music collection and even broaden your horizons to expand beyond those boundaries.

Makesure to share your favorites and tell us why you think they are the 'best in the world' or at the very minimum and most importantly, the best to suit your needs.

Also check these MG15 pages:

A pair of dual concentric Tannoy drivers have been on my wish list for a long time. Try Google 'tannoy monitor gold' and you will be flooded with web pages describing aural nirvana from these drivers. Read here: http://www.hilberink.nl/speaker.htm
I rush to tell that I did not become a Tannoy owner this time due to price. Something in the range of 2,000 USD is serious money and possibly the price is right, but this was not the time to invest in speakers that wouldn't be my main speakers anyway.

Fortunately we have a 'Mister Tannoy' here in town and a call provided me with two 100 litres closed cabinets and 5 x 15' Monitor Gold drivers plus a box of crossovers. 'Take your pick! And be sure that you will never hear what the Golds can do from these 100 litre cabs, they rather need 150-175 litres - or even better, 250 litres!' Initially I asked for some 12' drivers, HPD 315, but the face of 'Mister Tannoy' went pale and his quick advise was to forget all about anything other than the Golds - and preferably the 15' drivers being superior to the 12' Golds!

250 litres is definitely into red WAF zone, but who knows. So, I took the whole lot home and started measuring the SPL response of the bass and compression driver without any crossover attached, trying to pair two drivers - because these 35-40 years old drivers do not necessarily measure the same!

Left: These 15' MGs are huge! Here on top of ScanSpeak SP38 speakers. Right: No, this is not how my test cabs looked, but surely some of these vintage cabs are beautiful.

Vintage drivers and what can be found:

Left: Apparently the HPDs are from a period where everything at Tannoy went wrong. The factory moved to Scotland with major start-up problems. The membranes got thinner in order to maintain efficiency from new and poorer magnets, the outer surround was made from rubber rather than corrugated, coated paper; the compression driver phase plugs were sometimes badly machined, etc., etc. All adding to poorer performance compared to the golden age of Tannoy, the Sixties and early Seventies. I found this picture on the web from a HPD driver, and yes, this phase plug is a really bad.

Middle: Actually one of the units had the compression driver voice coil stuck at one side in the magnet gab - and this driver has probably been delivering the 'Tannoy sound' for decades with a major 10 dB dip around 2 kHz as can be seen below. This was how the pole piece (= phase plug) was centered:

Right: The aluminium dome of the MG15.

Above is seen the impact on frequency response from various settings of the 'level' knob on the crossover and yes, if I put the 'level' on maximum and 'roll-off' on maximum, I could get a profile that started looking reasonably linear, but this was not how the MG was meant to be! This driver was over and out. So, even if you're buying MGs, be prepared for a bad day in the Sixties at the assembly line of Tannoy. I have to tell I once owned a British car build early Seventies, and it wasn't until I bought a Honda Civic that I found out that cars could start every morning for ten consecutive years! Hmm...
Hard to believe that this driver was not rejected in some quality check procedure. These drivers were big money even at that time. Eventually I found two drivers and two crossovers that seemed to work properly for initial listening tests. Crossovers? Yes, these were anything but consistent in performance. Here's a picture of the interior:

MG15 Crossover

Most of these components are of good quality and the reason for serious deviation from target is the electrolytic capacitor in the bass lowpass section. I measured from 13.3 to 24 uF (!) for the intended 16 uF. The lowpass section is simplicity itself: a choke and a capacitor (1.2 mH and 16 uF). 12 dB/octave and a point of crossover around 1200 Hz.

Late MG 15 crossover:

Left: Rear panel with terminals and rotary switches for adjusting tweeter level and tweeter roll-off.

In this late - and very well kept - version of the MG15 crossover, the electrolytic cap is replaced by a new capacitor, most likely made the same way as film caps, only here from etched foil based on physical dimension. Also for the tweeter section new - and better - caps have been used.
I can only admire the nice wiring job done here. All in best of order with twisted wires and secured leads. It takes time to make a crossover like this.

MG15 Crossover Up-Grade

Left: Click image to view large. Right:
Up-grade kit finished. Click image to view large.


Left: MG step response. As can be seen, the tweeter is connected with inverted polarity. Actually it's connected with positive polarity, but being mounted with the inverted dome facing the horn, the output comes out inverted.
Right: Above is seen a nearfield measurement of bass/mid and tweeter. Point of crossover appear to be around 1200-1300 Hz. Very steep slopes despite the 2nd order crossover. Based on medelling the sloped are close to LR4. A nearfield bass driver reading producing a flat response down to 50 Hz is not an everyday sight, I can tell. And a nearfield reading is highly dependent on where you actually place the microphone, so don't pay too much attention to dips and bumps. The Tannoys do not measure nice, but as seen from a lot of other big speakers, this does not seem to compromise sound. Another example of not putting too much into FR readings of loudspeakers. It tells very little of how they actually sound. So, with this fine-tuning I could start listening - and what a sound!

It's hard not to be completely swept off your feet when you first time connect these monster drivers. Every time I hook up a new pair of speakers I run a test CD to check left-right, polarity, etc., at it's not often you actually hear 'something' from the 31 Hz warble tone on the test CD, but here it was.
I had never thought my Copland could provide the speed and transient attack as it appeared connected to these drivers. 90-92 dB sensitivity and 6-8 ohms impedance is yummy to most 2 x 50 W valve power amps - and the Copland loved it.
I have never been able to hear female vocalists this loud without serious distress to the ear (= distortion) and I've never heard applause from an audience from live recordings this clear. Acoustic bass starts getting the right proportions and a full drum kit from these speakers is aural nirvana. No doubt about it.

That's not to say the MGs like to be played loud, they are very good too at low volumes and don't need a whole lot of power to be 'energized'.
In my listening room I have the speakers on the long side. Usually 1 metre from the rear wall and with 1.8 metres to the sidewalls. Use to work fine and so did the Tannoys - except that they simply appear to be too large for listening at 2-2½ metres distance. The very first thing that came to mind when I played music on the Tannoys was my earphones. Listening nearfield to these drivers is like putting on a giant pair of earphones, except that you now can actually feel the bass. I'm certain the earphone association came from the coherence of the sound coming from these drivers. This dual-concentric principle is a little wonder but I have always been suspicious about the integration of a 90 grams heavy paper cone and a 'no-weight', horn-loaded compression driver. How can this go well? But it mostly does here. I guess that the large radiating area of the horn driver - actually of exactly the same size as the paper cone, as the paper cone is the horn - is part of the explanation why it performs so well.

This does not imply that the Tannoys do not have a 'sound' - they very much do so. When it comes to midrange transparency and neutrality they are somewhat behind the Acapella SE set-up. The Acapella SE has a much more neutral midrange presentation and much better pin-point imaging compared to the MGs.
Pin-point imaging: Well, we would think that the dual-concentric principle would make a further contribution to the overall coherence and seamless integration of midrange and treble, enhancing pin-point imaging, but this was not my experience. Sitting at 2½ metres distance I sometimes found it hard to render the same ease of localisation of vocals and instruments in the acoustic scenario. These membranes are so huge that vocals seemed to come from all over the place. I've experienced the same thing with panel speakers and I guess that's part of the reason Peter Walker added the delay lines to the famous QUAD ESL63. To get better dispersion and to target a point source radiator. So, we're back to the discussion from the 'Infinite Baffle Speaker' file on pinpoint imaging, and again: Paul Messenger:
'Narrow speakers with a very wide radiation include more of the listening room and help create an illusion of bringing the musicians into the room; while more directional designs like horns and dipole panels give a precise view onto the recording itself.
The Tannoys are to my experience quite directional speakers. I have measured the horizontal dispersion - no need to do a vertical dispersion here as it will be the same due to the dual-concentric principle - and it is very good. You measure the same FR all over the place, but when listening in stereo, they are quite directional and you move the speakers around and you move your head around to find the best position for stereo integration. These speakers need large rooms and a listening distance of 4-5 meters to perform the best. Not my cup of tea for near-field monitoring. I guess the 12' or 10' would be better suited for this situation but with sacrifice of deep bass.

Monitor Gold Type LSU/HF/15/8

New crossover

From the frd and zrd files of bass and tweeter I modelled a new crossover trying to get as close as possible to the 1.2 mH and 16 uF used in the original low-pass section. This persistently came closer to a point of crossover around 2 kHz against the claimed 1 kHz point of crossover. Measuring all the drivers - with original crossover - there appear to be a major overlap in the crossover region and no matter what polarity was given to the tweeter, the nulling effect wasn't visible at all. The phase-tracking between these two drivers is indeed very poor.
The weird thing about the MG is that the coil in the LP section can be varied a lot without affecting the midrange much, this partly due to the impedance profile. And this driver is so big that measuring the FR at 1 metre distance is really too short. We're getting into near-field conditions and these drivers should possibly be measured at two metres distance, but my workshop won't allow this and I didn't have time to take the drivers outside for proper measurements.
However, with 1.2 mH and 16.4 uF+2R2 a reasonably flat response could be achieved with a point of crossover around 2 kHz. In fact the same I measured from some of the drivers fitted with the original crossover. The compression driver however, seems to target a point of crossover around 1.2 kHz but due to the drivers being out of phase the overall result is a reasonably flat response when the 'level' and 'roll-off' setting is used properly.

Left: The measured FR is close to the predicted. Disregard actual dB level. This reading was not generated with 2.8 V input.
Right: MG/original crossover (red) compared to Acapella SE (blue, only midrange+ribbon).

The frequency response (FR) of these Tannoys looks awful! Why is it this doesn't leave this driver useless? I've seen FR from electrostatic speakers that look even worse and yet these speakers sometimes deliver the best of sounds. After delivering back the Tannoys I connected the SP38s again and yes, these speakers are much more well-balanced, the dispersion is much better - it's simply a more truthful presenter - but it can never deliver the bass punch and hard beat of the snare drum that hits you like a bullit from the MGs.

So, what's to be learned from these Monitor Golds? Well, sensitivity is an important parameter and they tell you that most of today's speakers really do not have the transient response capability of these ancient drivers. I read that a lot of enthusiasts using single ended amplifiers will use high sensitivity speakers in order to cope with the sometimes very few watts available from these amps. We see 15' coax Fane drivers used with 5 watts SE amps, but 15' Fanes are meant for PA application and not for hifi. Aren't we getting back to some JBL sound - for better or for worse - in order to provide the necessary sensitivity? Where is the smooth, well-balanced sound from high sensitivity speakers? Where are the high sensitivity speakers that will cope will all sorts of music and not just trio jazz?

I tried playing some of the old Beatles LPs with the Tannoys - the very same speakers that were used for mixing at Abbey Road - and it really didn't sound too good. I wonder if this was what George Martin was hearing at the mixing desk.
These medium-sensitivity Tannoys come close in being able to handle almost anything. I don't find them particularly transparent but they will for sure tell you that there are a lot of things your current speakers probably are short of.

Drivers Concentric Model

I cannot thank 'Mister Tannoy' enough for lending me his wonderful drivers!

Comments from UK reader, who wants to stay anonymous:

Drivers Concentric Definition

Hello Troels, I enjoyed your story about the Monitor Golds very much. You ask yourself at one time after playing Beatles recordings: Is this what George Martin heard when he was doing the recording? Taken into account the many variables like room acoustics, amplifiers etc. It is save to say he probably did.
I used to work with Tannoy 15' units placed in large Lockwood cabinets at Polygram. These units were used in many studios around the world during the sixties and seventies. The sound was not spectacular HiFi nor very detailed. That is not what a recording engineer is looking for in the first place when selecting a professional monitor system. These Tannoys deliver a reliable sound pattern that allows engineers and producers to balance the sound and use the large array of filters and outboard equipment to do a mixdown of a multitack recording. In studios the HF horn was most likely to die long before problems with the LF unit would arise.
After we moved to the newly built Wisseloord studios in 1977 the Tannoys were abandoned. At Wisseloord a completely different system with JBL units was used that gave a far more detailed sound and better defined spacing of the instruments. This system was part of the acoustically designed control rooms.
To double check the voice/orchestra balance we often used the Philips 9710M units in a realtively small enclosure. Out of large quantities 9710M frames selected units were used by Dutch radio to serve as monitor speakers in broadcast studios. I had the pleasure of meeting Mr. Koppinga the designer of the 9710M during the seventies. In Holland there is still a strong demand for these wideband units after nearly 50 yaers since their introduction.
With kindest regards.