TNT Review

This page will introduce, re-publish in full (with permission from TNT) and respond to the review of Nick Whetstone published by website.

Stop Press 5th May 2006, we have just had published the first thorough independent review on ( please bear in mind the conclusions about amplifiers are factually incorrect and we will explain this  during May but to see the review click here)

for more revie


ws and to see all the TNT site, visit

[ Home | Staff & Contacts | HiFi Playground | Listening tests | DIY & Tweakings | Music & Books ]

Resolution S.U.H.T.L loudspeaker

The World's best Loudspeakers?


Product: Resolution S.U.H.T.L loudspeaker
Manufacturer: Resolution - UK
Approx cost: 2150 UK pounds in piano black finish and supplied with the
Behringer Ultracurve Pro DEQ2496
(Resolution supply the DEQ2496 complete with connecting cables, a Behringer ECM8000 measuring microphone,  microphone stand and cable)
Reviewer: Nick Whetstone - TNT UK
Reviewed: April, 2006

Just what I like - a loudspeaker review and no DIY involved! Just sit back and listen. Well, that's what I thought before the Resolution S.U.H.T.L.'s arrived, complete with Behringer DEQ2496 (a digital sound processor that allows the user to tailor the frequency response of a hi-fi system). As it turned out, I have  never done so much work listening to one loudspeaker!

But let's start at the beginning. About a year ago, I saw some loudspeakers for sale on Ebay.  "Transmission lines", said the item description, and they used a funny looking elliptical drive unit (a car speaker said some in disgust). But what really caught the eye was the claim that these were the 'world's best loudspeakers'. And they weren't cheap either. It wasn't long before audiophiles were expressing their displeasure, presumably based on the claims of the seller as very few had actually heard the speakers. They say that any publicity is good publicity and the claims of the manufacturer, Resolution,  certainly stirred up interest, even if it was perhaps the wrong sort. Like others, I wondered if this was a serious product or somebody pulling a scam on Ebay, so I followed the debate on a well-known hi-fi forum. But when the posts died down I soon forgot about the S.U.H.T.L.'s.

That was until recently when I was contacted by Nick LeFeuvre, the designer of the S.U.H.T.L.'s. He was  exhibiting his speakers at the Bristol Hi-Fi show, not far from where I live, and invited me to go along for a demonstration. Unfortunately, I was ill that weekend but I agreed to do a review at my home.

If you visit the Resolution web site, you can read why they rate their loudspeaker so highly. Certainly the  theory behind the design of the S.U.H.T.L.'s is sound. A single-point source and a rock solid cabinet that doesn't resonate or allow sound to escape will help clarity and timing and keep the bass tight and controlled. Resolution also managed to obtain a patent on the S.U.H.T.L.'s based on the special sound-insulating material used for the cabinet construction.

Nick LeFeuvre delivered the speakers to me personally, together with a Behringer DEQ2496 and measuring microphone. Being a helpful sort of chap, he also supplied a Pioneer A575A DVD player and several amplifiers.

Originally, Resolution recommended using the S.U.H.T.L.'s with an amplifier that has tone controls in  order to boost the bass frequencies. This suggestion alone caused some to dismiss the S.U.H.T.L.'s. Many audiophiles say that tone controls on an amplifier have no place in a high end system. And shouldn't a loudspeaker reproduce a flat response anyway? Well, it is certainly unusual to ask customers to boost the bass frequencies so why did Resolution do it? The answer is found in the design goals for  this loudspeaker. The aim was to cover a very wide frequency range from around 20 Hz to 20 kHz, using a single driver, in a small(ish) enclosure. Quite obviously, to anybody who has designed a loudspeaker, there would need to be some compromise. Hence the need for some assistance for the bass frequencies.

It was a logical (and some may say more professional) step to use something like the Behringer DEQ2496 that can not only boost the bass, but correct the whole frequency range to compensate for the effects of the listening room, and (to a lesser extent) the equipment used to drive the S.U.H.T.L.'s. As TNT  caters for all hi-fi enthusiasts, and not just those who build hi-fi or have technical knowledge, I'll try and explain this business of frequency response and correction.

Frequency response and equalization

Imagine a simple piece of music, say a single piano or guitar. You will be able to distinguish separate  notes. These notes are of different frequencies, that is they cause the air to vibrate at a different rate. Bass notes vibrate at a slower speed than treble notes. We can measure both the frequency of an individual sound (in hertz) and it's loudness in ~decibels (db). If we measure the different frequencies of a sound and then plot a graph of those frequencies and their loudness, we will get something like the results in figure 1. The line on the graph represents what we call the frequency response.



Figure 1

You can see that figure 1 isn't a straight line because some frequencies are louder (more decibels) or quieter (less decibels) than others.



Figure 2

Now, if we play a set of test tones through a hi-fi, and those test tones are all recorded at the same level (loudness), we could expect that our loudspeakers will reproduce all of those tones at the same level, producing a graph like the one shown in figure 2.

In reality, this will never happen! This is due to the fact that no loudspeaker driver produces a perfectly flat response, and other factors come into play, particularly the effect of the listening room. Even if the speaker measurement is done in an anechoic chamber (where there are practically no reflections off walls and furniture etc), there will still not be a perfectly flat response.

Fortunately, our ears and brains are not sensitive enough to pick up every small deviation in the  frequency response (although we will notice if a particular band of frequencies is much louder or quieter than the others). But, in theory, a loudspeaker with a perfectly flat response should sound very good and  one with too many peaks and troughs should not. In practise, it doesn't always work out like that. What we are looking to achieve is a good balance between the lower (bass) frequencies, the mid frequencies, and the higher (treble) frequencies, and if a loudspeaker does that without any major peaks or troughs in the response, we should find the sound to our liking.



Figure 3

Just to complete this mini tutorial on frequency response, let's look at a couple of other response  characteristics. Figure 3 shows a falling response where (on average) the lower frequencies are louder than the higher ones. A loudspeaker with this sort of response would give the impression of having a lot of bass and not much treble.



Figure 4

And figure 4 shows a rising response. You have probably guessed already that this is the opposite of the response in figure 3, ie it will have less bass and more treble. A loudspeaker with a rising response is often tiring to listen to.



Figure 5

OK, back to the S.U.H.T.L.'s and the Behringer DEQ2496. If we measure the S.U.H.T.L.'s (on their own)  and draw a graph of their response, it will look something like figure 5, ie it has a rising response and as the bass gets lower, the level gets quieter. The DEQ2496 allows us to boost the lower frequencies (and  any others that we choose) so that the response is flattened out. In fact we could further boost the bass frequencies if we want a little extra bass if we are listening to rock music for example. Yes, we could do  that with a simple tone control on the amplifier but the DEQ2496 is much more versatile.

Before we move on, it may be a good time to remind everybody that there is no such thing as a free lunch . What that means in this case, is that we can't just get more bass by adjusting the frequency response if there is not enough power from the power amplifier to drive the speaker. If you use an amplifier without the power to produce the extra lower bass, it will clip. That won't sound good and may damage the amplifier and/or speakers, although typically, tweeters are far more at risk than woofers. While testing the S.U.H.T.L.'S, I tried both the Sonic Impact T-AMP, and the Charlize class-T amplifier. Both these  amplifier worked but only if I didn't try to equalize the bass frequencies below 40 Hz.

Room Correction



Remember that many factors can affect the frequency response, one of the major ones being the  listening room. Soft furnishings like carpets and sofas can 'suck out' certain frequencies so that they are reduced. Hard surfaces like walls or bookcases can reflect frequencies so that they are louder. If we knew which frequencies were affected by our listening room, and by how much they needed adjusting, we could correct the frequency response so that our music was heard as it was intended by the recording  engineer. And fortunately the DEQ2496 includes a facility to help us do just that.

One of the best features of the DEQ2496 is its RTA (Real Time Analyzer). If a microphone is plugged into the DEQ2496 and sound is played through the loudspeakers, it has the ability to measure each part of the frequency range and then correct the level, thus compensating for any peaks or troughs caused by the room.

Now, if you are thinking how wonderful all this is, and how a DEQ2496 is just what you need to make your own loudspeakers sound 'perfect', there is a catch. First off, the DEQ2496 can only equalize ('flatten') the frequency response, it can't make a poor driver sound good. It can't get rid of the sound of a poorly  constructed cabinet. It can't help with a poorly designed crossover. Neither will it solve all the problems caused by the listening room. So some research into room treatment would be a good idea before your  rush out and buy any device that does room EQ. The DEQ2496 also routes the signal through a lot of electronics and processing (the DEQ is targeted at PA systems rather than domestic hi-fi!). But with that in mind, let's find out how it all works in practise with the S.U.H.T.L.'s.

Apart from the S.U.H.T.L.'s and the DEQ2496, I was also supplied with a Pioneer DVD575A DVD player and a selection of amplifiers: a Yamaha A420, a Cambridge Audio A1 and a Sonic Impact T-amp. Resolution were interested in my opinion on which amp worked best. The S.U.H.T.L.S have an  impedance of 4 ohms so some amplifiers will not work well with them, particularly if they asked to cope with equalisation down to 20 Hz.

The first job to do, having set up the system, is to use the DEQ2496's room correction function. This is a relatively straight forward process and Resolution have been good enough to supply instructions that are taken from the Behringer manual but condensed down to an easy-to-follow step-by-step guide. If you can  program a VCR or digital alarm clock, you should be able to work the DEQ2496. If not, you will need to find somebody to help you.

With the microphone plugged in, and positioned as close as possible to the main listening position, the  relevant buttons are pushed and you can then go away to get a drink while the correction process is done automatically. After about five minutes, the process is finished and it's a good idea to save the settings.  Apart from setting the master gain control on the DEQ2496, you are then ready to listen to some music. After doing the room correction a few times, I found it all very easy. Despite its versatility, and the plethora of controls, the DEQ2496 is not difficult to use.

Having set the room correction, there is also the option to tailor the frequency response to your taste. This  may involve a little bass lift or treble cut, or perhaps some adjustment to take the edge off female vocals, or add some presence to a live recording. You may find that some recordings that you haven't liked before can now be made more listenable.

So, how does it sound? I have to start this section by saying that this was a very difficult review. Not only  did I have the speakers to listen to but the DEQ2496 as well. This makes for a lot of options. The DEQ2496 can go between a pre-amp and power amp. Or it can go before the pre-amp. A separate  DAC can be used, or (if your CDP has a digital out), you can feed the digital signal directly into the DEQ2496. Suffice to say that I spent a lot time swapping components and cables.

Not surprisingly, some combinations worked better than others. But what did surprise me was that the best combination didn't necessarily consist of the best components. In fact, I found that the better the amplification, the less I liked what was coming from the speakers. In the end, I found the best set-up was the DVD player feeding a digital signal to the Yamaha A420 integrated amplifier. That was connected to the DEQ2496 via its tape loop. I concluded that this less revealing combination masked what I perceived to be the effects of the DEQ2496 (although it could equally have been the speakers).

As regards positioning, the S.U.H.T.L.'s are best set up as far apart as possible and won't mind going right back into the corners. I had them toed in slightly to the listening position. All comments on sound quality will refer to this set-up.

But in case you are wondering how the S.U.H.T.L.'s sound without the DEQ2496, let me tell you that they  are nothing special, sounding light on bass and (for my taste) having too much top end. It's not a loudspeaker that I would want to listen to!

So let's get on to how it sounds with the DEQ2496 and we may as well start with the positives.

This set-up produced the largest sound stage that I have heard in my listening room. And imaging was absolutely spot on. On a live recording, it was easy to locate each performer within the sound stage and with plenty of space between them. The height of the sound stage was unusually high as well so that lead  singers actually appeared to be standing in front of me, rather than crouching down. The depth of sound stage on well recorded material was also very good, not quite matching my open baffles but not far away, an excellent result for a 'boxed' speaker situated so close to the rear wall! What these speakers didn't manage to do was to project the Q sound effects on Roger Waters 'Amused to Death' CD as far into the room as my open baffles do.

I have one piece of orchestral music that is very well recorded and with the S.U.H.T.L.'s it was possible to accurately locate each part of the orchestra. I also noted that the percussion section, located at the back of the orchestra was particularly clearly defined.

Despite using what I consider to be a less revealing amplifier, the clarity was excellent. I heard details on  (very) familiar recordings that I had not heard before. Live performances benefit from the clarity. Jackson Browne's 'solo acoustic' CD had a real sense of 'being there'. Each note of his acoustic guitar and piano  were crystal clear. And the ambience was clearly audible too.

The S.U.H.T.L.'s also managed to keep good control through complex pieces of music like Romantic Warrior's 'Return to Forever' and the Pat Methany/Ornette Coleman album, 'Song X Twentieth Anniversary'.

Timing was also excellent meaning that the music was highly enjoyable and addictive. Playing Nusrat  Fateh Ali Khan's 'Night Song' CD, the timing of the S.U.H.T.L.'s really made the music come to life. If the timing isn't right with this CD, it can tend to plod along and lose its appeal. Jazz recordings also sounded great, everything that I played from Diana Krall ('The Look of Love') to Bill Bruford's Earthworks  ('Footloose and Fancy Free') had real energy.

With the room correction, and a little bit of extra lift from the DEQ2496, the bass quality is reasonable. It  is tight and well controlled so there is none of that boom boom (although you can add it with the DEQ if you really want to). The bass is also 'fast' no doubt accounting for the excellent timing of these speakers.  The Easy Stars All-Stars CD 'Dub Side of the Moon' and Outrospective's 'No Roots' were particularly good through the S.U.H.T.L.'s with their bass lines tuneful and well defined.

I found the S.U.H.T.L.'s very capable of handling a large dynamic range. The Dadawa CD, 'Sister Drum'  varies from a whisper to mighty crescendos of drums and Tibetan horns but both were well portrayed. The Dafos CD (Hart/Airto/Purim) is another excellent test of a hi-fi system and the S.U.H.T.L.'s did a  commendable job with this album too.

Scale was also very good. Orchestral works felt like they were being performed by a full orchestra in a  large hall. Ennio Morricone's 'The Mission' and other tracks from his 'Best of' CD gave me a sense of being at the cinema, rather than in my own front room.

One of the hardest tasks for any loudspeaker is the accurate reproduction of the a piano. To their credit, the S.U.H.T.L.'s portrayed pianos very well.

So are these really the world's best loudspeakers? Well unfortunately no! The fact that I needed to use a  less revealing amplifier obviously compromises the system although as you can see from my comments above, it's still possible to achieve a performance that is many times better than a lot of other  loudspeakers. I suggest that there will be those that can live with the S.U.H.T.L.'s and love what they do, and others who are not so impressed by the sound staging etc and want better sound quality.

Overall sound quality was not as good as I am used to, and was probably compromised by the drivers.  As well as they did the parts mentioned above, it's asking a lot of any (smallish) single driver when it is equalized down to 20 Hz, and expected to cover the rest of the frequency range at the same time. I prefer the sound a bit more rounded, with a little more body. Switching back to my own system, drum beats for instance were much more real, more tangible.

Where I see the S.U.H.T.L.'s being popular is with customers who have perhaps a smaller listening room and a rather unsympathetic 'significant other half'. The S.U.H.T.L.'s (particularly in the beautiful piano black finish that I reviewed) are quite attractive, not too large, and can be placed out of the way in the corners of a room. But far from being compromised, they can still offer a sound stage and performance that would usually be associated with more intrusive (ie larger) speaker systems.

It should also be said that with the fantastic sound stage and imaging, the S.U.H.T.L.'s will almost certainly do a good job with Home Theatre/Cinema. Add a sub to cope with those extra thuds and bumps. and the system should do a grand job with most TV, DVD or video material.

In my opinion the S.U.H.T.L.'s are targeted at the wrong sector of the market. At around two thousand  pounds (the mahogany finish is 1950 UKP), they are competing with the likes of the Monitor Audio GR60's. I mention the latter because I have heard them and they are clearly superior to the S.U.H.T.L.'s. Now if the S.U.H.T.L.'s were targeted lower, they would appeal to a much larger audience. Yes, I appreciate the build quality, and work that has gone into them, and the fact that the DEQ2496 is included  in the purchase price but I really believe that they should be aimed at those on a lower budget. And dare I say it, to those who don't have top-end systems. The sort that sound quite nice but where the sound  usually comes from a narrow spot somewhere between the loudspeakers. The S.U.H.T.L.'s (with the DEQ2496) could elevate such systems to a much higher level with the excellent sound staging, imaging and clarity. As lower budget systems are often found in smaller listening rooms, the tricks that the DEQ2496 performs would be much better appreciated, and the less revealing amplification wouldn't  show up the shortcomings.

So where does this leave us with the S.U.H.T.L.'s? As I said, they are not the best loudspeakers in the  world but neither should they be dismissed lightly. The design is sound and their ability (with the DEQ2496) to overcome room problems and portray such a convincing 'picture' of the music is highly  commendable. They look good and should not upset SWMBO (She Who Must Be Obeyed). I can recommend taking up Resolution's offer of a 30 day home trial. If you have not experienced a top-end system, they may open your eyes, and your ears, to what stereo can really achieve!

As regards the Behringer DEQ2496, there are two camps amongst the DIY community debating whether the DEQ2496 and its sister product, the DCX2496 (that adds digital crossovers to the equalization but doesn't have the room correction facility) are worthy of a place in a domestic hi-fi. Some swear by what  DSP (Digital Signal Processing) does while others don't like what it does to the signal. I read many threads on this subject and couldn't make up my mind if I would like the Behringer in my hi-fi. It wasn't until  I actually heard the DEQ2496 in action that I could finally decide. So, I suggest that a home trial is the only  way to decide if DSP is right for you. For the record, I am intrigued enough to buy one and do some more research with my own speaker system although I will either upgrade the analogue sections or use both digital input and outputs.

© Copyright 2006 Nick Whetstone -

[ Home | Staff & Contacts | HiFi Playground | Listening tests | DIY & Tweakings | Music & Books ]


Thanks to Nick Whetstone and TNT for all their hours work reviewing this product Free of charge. These independent amateur enthusiasts with an ear for listening and a skill for writing are an important alternative to  the 'paid-off' press. Since this review, Nick Whetstone now has been equipped with an integrated amplifier and AB remote test switches, so he can run more demanding loudspeakers and instantaneously compare sources and loudspeakers/amplifiers without getting up from the listening position. .

Our response

According to Nick Whetstone - our loudspeakers were in most respects the best he'd ever heard, and generally would deserve the title of world's best loudspeakers, except clearly there is one problem.

I asked Nick and TNT to correct this, but both refused in favor of us having to treat you to an adversarial review/response. Apologies if this gets as technical as the review

You decide - is the problem that 'better' amplifiers wont work properly or the or, is it just the reviewers lack of equipment and experience?

Nick Whetstone stated above it is a fact that better amplifiers made a worse sound.....

( "But what did surprise me was that the best combination didn't necessarily consist of the best components. In fact, I found  that the better the amplification, the less I liked what was coming from the speakers. In the end, I found the best set-up was the DVD player feeding a digital signal to the Yamaha A420 integrated amplifier." )

Those 'better' amplifiers which were the 'best components' are in fact amplifiers Nick Whetstone made himself out of Gainclone kits, he has modified and packaged into sections of drain-pipe and badly sawn softwood.  The initial amp we connected of his, clipped badly every bass beat, trying to reproduce music at normal level. After lunch we tried his more 'powerful' gainclone (contradiction 'powerful' and 'gainclone') but no joy  either. I decided this was an amplifier problem, and the next day supplied the Yamaha A-420 amp, and within minutes had it setup and not distorting no matter what volume it was played at. Nick Whetstone was  astonished, and I tactfully left him to figure it out (his amps were gutless- having no reasonable power below 40hz that a full range reference system needs), but later found he was incapable to consider his amps could possibly be worse than the mid-range amp we had to loan him.

So, the only significant problem the TNT reviewer found during testing, was his own home-made amplifiers (low-power gainclones) didn't work as well as a decent amplifier that had to be loaned to him.

Subsequent to this shocking conclusion - we conducted an amplifier comparison test on how good the A-420 was?
(pic March 2006, amplifier shoot-out test Marantz PM66 SE, Yamaha A-420, NAD 3020e, Rotel RA-810a, T-amp)

You don't have to write for TNT to be able to test amplifiers, and with instantaneous AB remote switching, and an  unbiassed view, we are far more likely to pick the best amp. At the time of submission, Nick Whetstone only had 2  working amps, which he had built himself - no others. We at resolution had experience also of several brand new top -brand amplifiers being connected to the same pair of speakers - ours. So who is most experienced to judge?

my opinion, Marantz and Yamaha equally faultless/absolutely identical performance, Nad, Rotel and T-amp gutless loud below 50hz I have never heard a better amp than the Yamaha I still use in the listening lounge, even the 2k Naim system hisses more.

TNT's reviewer implies that better (gainclones) amplifiers do worse than cheaper ones (a-420)?

Clearly this is nonsense and the facts suggest the opposite: The yamaha a-420 is really a good amp. DIN 70wpc 4 ohm THD 0.01% and had  dynamic power@1khz of 115W

In a listening test last week, it had the edge over the Marantz PM66SE in detail but same bass (no clipping even at  105db SPL 1m), and that(or smaller Marantz PM40se model) is supposed (implied by Geoff Husband www.tnt-audio .com/guide/amps_e.html etc ) to be as good as a Pioneer A-400. The Marantz power is only 50W RMS into 8 ohms and thd 0.008%. I conclude that the A-420 although old, is an audiophile standard amplifier and not low quality at all like the cambridge A1 which is gutless budget amp.

At the Bristol show, we borrowed a brand new Naim Nait 5i
, and it worked superbly, providing a powerful bass so the equalizer didn't lift it so much, and at Heathrow show this weekend, we borrowed a Naim 112 and nap 150 separates with even more quality(rrp>2k)
. I couldn't detect any improvement over the Marantz I took as a spare, but it 'looked better' with the Naim kit alongside 'raising the implied value'. Did people think it was poor? - no, in fact our surveys proved how if anything more seasoned listeners were there giving much higher marks in the main. We even had one guy of 20 shows experience giving straight 10's and another with 300 shows giving 9,10,8,9,10,9.the Heathrow surveys (10) went online recently, and are at the bottom of this page...

see the endorsements letter from my Naim (112/150) customer Jeff (112/250 on photo there) http://www.resolution


That was the main error in the TNT review covered. So if you carefully read his conclusions, and accept he was wrong about the amplifier quality assumptions-as proved above, you would see that the Question "World's Best Loudspeakers?" would have been answered the opposite!

To be honest, we never expect any reviewer could have the courage to state anything was "the best" no matter how superior and thrilling the sound demonstration is, but this review is better than that, because he clearly states the only reason it isn't the best, is because of that easily disproved  misconception.

We hope more experienced reviewers of  'full-range high-fidelity reference systems' with an  interest in imaging, will now come forward and try Resolution SUHTL for themselves and their readers.

The most important thing for interested readers to do now, is listen themselves, and they should do  this as soon as they can. For details of forthcoming exhibitions, home demos, 30-day trials and showroom demos, visit our website or call us now (daytime) on 01202 470184. email

[Home] [About Us] [Catalog] [Showroom] [References] [Looks] [Reviews] [Bristol Show 05] [Bristol Show 06] [Endorsements] [London Show 06] [TNT Review] [Facts] [Sound] [Advertisements] [Professional Monitors]

Please contact our Webmaster with questions or comments.
©Copyright 2004.  All rights reserved.

[Home] [About Us] [Catalog] [Showroom] [References] [Looks] [Reviews] [Bristol Show 05] [Bristol Show 06] [Endorsements] [London Show 06] [TNT Review] [Facts] [Sound] [Advertisements] [Professional Monitors]

Please contact our Webmaster with questions or comments.
©Copyright 2004.  All rights reserved.