REL T/5x – Do you need a subwoofer for Stereo?

REL and LS50

REL T/5x

Tested at $650 (750€ in Serbia)



Ease of integration







  • Speed and control
  • Integration
  • Adds depth to the sound


  • Requires some experimenting

REL T/5x is the second smallest subwoofer in REL’s latest budget offering, but it is the first subwoofer that I’ll ever try to integrate into my own system. Because I don’t have much experience with subs, except listening to them in other people’s systems and at HiFi shows, this will be more of a personal experience than a traditional review. Instead of telling you how this sub compares to competitors, I’ll share my line of thoughts, why I chose it, what I expected, and what I got. T5/x costs 750 EUR in my country, which is roughly around 850 USD, so in the end, I’ll share my thoughts if it’s worth adding it to a stereo setup or not.

Why I need it

My system is built around well-known and praised KEF LS50 speakers. I love those little guys for their forward and energetic presentation, for the resolution, and for the soundstage too. But one thing they never had is the weight and punch of a bigger speaker. Having a friend that uses KEF R3, and auditioning systems with floorstanders, I realized that in some songs my setup lacks proper heft. But buying a bigger speaker that will keep all of these qualities that I like, while adding more weight and punch is not an easy task. I’ve heard many of those and ones that can completely match LS50’s speed and resolution, just on a bigger scale, cost significantly more. I’m not talking double here, something such as KEF R7, for example, simply can’t match LS50’s incisiveness. So it’s more likely we’re talking about four to five times the price to achieve that on a bigger scale. Following this line of thought, I came to the logical conclusion that I should try to integrate a sub.

Now choice for me was quite easy really. I’ve heard several subwoofers from traditional speakers manufacturers such as B&W, KEF, Monitor Audio, Canton… and I was never impressed with these. They always added a lot of weight to the system but in a sluggish and bloated way. I didn’t want that – there’s a reason I like LS50 so much and I didn’t wish to drown its qualities. At the same time, I’ve kept hearing praises about RELs, their speed, resolution, seamless integration thanks to high-level connection, etc. So I’ve decided to give it a go.

My room, system

My setup is located in my living room that’s roughly 4.4 by 7.2 meters (15 by 23 feet), with some open walls in the back that lead to the kitchen and the hallway. All of those together make an open area of 40 m2 (430 sq ft). This was the system at the moment of the sub’s arrival:

I won’t go into cabling this time, but several months have passed since then and Hegel left the system. In its place came Acoustic Invader Preamp and Amp combination which is a force to be reckoned with, outshining even Hegel H190 in my setup. That change however didn’t have any influence on my subwoofer use and impression because REL will indiscriminately take the signal it was given from the amp, the same way the main speakers do.


My first attempt to integrate REL T/5x into the system happened in the evening just after I brought it home. I prepared beforehand by watching dozens of video tutorials, many of those by REL’s own John Hunter. Dominant idea was that the sub should go in the corner of the room since walls will enforce the bassline, and our hearing can’t really locate the low-frequency source. Theory aside, no matter how low I dialed the sub, as long as it was anywhere near the corner it would produce a boomy bass that feels very disconnected from the main speakers. To put it simply, the bass was noticeably lagging behind the rest of the spectrum. I felt tired and deflated that evening, and I went to bed utterly unimpressed.

The next morning I took another direction, the one that made much more sense to me right from the start. I put the sub just next to the left speaker stand, on the outer side. The result was immediately better, with the sub finally starting to sound like a part of the system and not a part out of the system. But I still felt that bassline was slower than many online impressions made me expect it to be. During the next few days I had it moved to the outer side of the right speaker stand (my room is not completely symmetrical) and it clicked on that side even better. There I was quite happy and spent the next two weeks enjoying it. After some time I tried moving it right in between speakers (not practical really because it stands in front of the HiFi rack) before finally settling on the inner side of the right speaker. There, that was my favorite spot. The sound latched to the main speakers really nicely without me being able to tell that there is a subwoofer in the room, it just felt as if the speakers got a little bit bigger and started playing a little bit deeper, that’s all.

The dials on the back are another thing you’ll spend some time playing with. I’ve started with both gain and crossover points set quite high – around eight to ten clicks for both. Most of us do so we can notice the subwoofer more. But as time went by I started to notice the tracks where the sub was still a bit too noticeable for my taste, so I dialed down both knobs slightly until I arrived at my current setting – 6 or 7 clicks for the crossover and just 4 clicks for the gain. This is something that will vary with different speakers, different rooms, and finally different tastes. So don’t try to simply copy the numbers, chances are it won’t work in your setup and you’ll need to tune it by ear for your specific situation.

Oh, and not to forget this, at all times I have been using high-level input. I don’t own an amp with a subwoofer out, and I also wanted to achieve the best possible integration where the sub is receiving the exact same signal as the main speakers, so there is no difference in color, speed, etc.


Once everything is set up properly, which is not an easy task, I was ready to critically listen to what I’ve got with this addition.

Bass extension

Let’s start with the most obvious thing – bass extension or how deep it can go. Well, this is a fairly small subwoofer, extending to 30+ Hertz, meaning it will not move your bowls like subs in cinemas do. If that kind of earth-shattering bass is what you need, this is probably not the product for your needs. But for someone used to a small set of speakers that doesn’t go much below 50 Hz, added depth and weight are quite noticeable. That deep grunt is most noticeable in movies and music that actually have deep bass. I remember watching A Quiet Place 2 soon after purchasing T/5x and being very happy with the physical kick and punch while aliens were ravaging our cities. This certainly added a new level of excitement to the whole experience. The same was true if I played some bass-heavy music. Let’s take Winter Songs (Icemusic) album by Terje Isungset as an example. Listening to the first song on the album – Fading Sun – it was so obvious that there is depth, physical kick, and just the sense of the weight to the sound that is completely out of the reach for LS50 playing on their own. But if you listen to some acoustic recording, country song, etc. the chances are that you’ll barely notice the difference…at first.

Impact on the tone timbre

Luckily for us, the function of the subwoofer is not only to add that sub-bass at the bottom that your speakers can’t reach. REL T/5x actually extends higher than that, gradually fading with higher frequencies but helping very gently all the way to 100 Hz or even higher. This makes the handover from the sub to the main speakers more gentle and gradual, but it also helps bolden that whole part below one hundred Hertz where LS50 nominally reaches but doesn’t have high enough output to sound bold and authoritative as some bigger speakers. Just look at how it starts to lose power as soon as we dive below 100 Hz.

This is a KEF’s own reading inside of the anechoic chamber. There is a bit more bass response in most real-life listening rooms due to the bass reflections, but LS50 still starts to slowly roll off as soon as it hits 100 Hz. So knowing this you can easily guess that even frequencies that LS50 can nominally play (50 to 100 Hertz) can be helped and noticeably improved by the sub, and brought to a much more equal level with the rest of the spectrum. And you definitely hear that. Even if a song doesn’t have really deep bass, everything sounds fuller and bolder with a sub. Vocals, drums, bass guitars, double bass, etc. This added fullness helps with the overall tone timbre. It makes everything sound more palpable and natural, less wiry, and less harsh. Listen to the music with the sub on for a few days then turn it off. Even in the parts where there is no deep bass, you’ll notice how vocals and instruments become a bit drier, artificial, and grainy.

Impact on the soundstage

I can only guess that at least some of you will be like – now you’re BS-ing me, that’s just not possible. But let me explain before you leave this page and call me a sellout. By the way, did I mention that I purchased this REL out of my own pocket and I didn’t get it for free or anything? The explanation is quite simple really – our brain is trained to analyze the frequency spectrum of every sound it receives. As you may know already, higher frequencies travel the shortest while the lowest ones travel the longest. That’s why when something happens right next to you, you hear every tiny detail while if it happens far away you hear a deeper and darker sound with plenty of echoes. Quick example:

  1. A car crashes into another car’s bumper next to you – you’ll hear a loud thump, as well as metal screeching and scratching very noticeably.
  2. A car crashes into another far away from you at the end of the street – you’ll hear a thump, echos of a thump bouncing off the buildings, and much more subdued scratchy metallic noises.

What this means is that sonic information coming from far away contains much more low frequencies that can survive that trip than higher ones that will get absorbed and dispersed along the way. When a music recording is made, most of the spatial cues about the size of the recording space, positions of walls, positions of instruments, etc. are contained in those lower parts of the spectrum. The lower part of a note will travel to the back wall of a big room, reflect, and return to the microphone in a form of a delayed reflection. And that is exactly what you will notice more when you add a sub into your system. It feels as if the soundstage suddenly became bigger and there is more darkness behind the musicians. At the same time, every tone feels more three-dimensional and more palpable too, which makes it more realistic and more believable.

Another way to go about this would be to make an analogy with drawing, which is something I liked to do in my spare time. You use a harder pen first to sketch all the lines and fine details, but the drawing doesn’t really come alive until you add some deeper shades with a softer (bolder) pen.

Well, small speakers do what a hard pen does, while a subwoofer adds deeper shading just like a softer and bolder pen does. In a sense you could say that subwoofer is shading the sound, making it more lifelike.

What a sub can not do

This one is quite simple – it can’t grow your speakers into bigger, more dynamic, and bigger sounding speakers overall. Everything the sub does it’s doing by manipulating frequency response or let’s say augmenting it. More bass means more physical feel, a fuller tone, and more threedimensionality. There’s a real added energy to the sound as the subwoofer pressurizes the room more than small speakers alone could. REL T/5x is quite a punchy little thing itself so that added bass is nimble and well-controlled, not slow and lazy by any means. However, everything above those 100 Hertz is still played by your main speakers. If they can’t handle huge dynamic swings like my LS50 can’t, the sub can’t change that magically. If they couldn’t create a huge wall of sound before, once again, the sub won’t make them sound tall and huge either. A speaker that was more dynamic and punchy, to begin with, will continue to be more dynamic and punchy. For example, KEF R3 will still handle big dynamic swings better than LS50 + REL because it sounds more dynamic in the whole frequency range.


I entered this whole experiment not truly knowing what will come out of it. Sure enough, I expected a better extension into the lower notes and I got that. I also expected to get a fuller sound and nicer tone timbre overall, because the root of most sounds is low enough for them to be influenced by the bass region. This soundstage improvement however was something I’d only read about but couldn’t fully understand until I experienced it myself.

Listening to the REL 5/Tx for several months now, I don’t like what I’m hearing if I turn it off. The difference is not huge in most recordings, but it’s there and once you get used to it, it’s hard to let go. When the sub is off, I now feel as if my sound became just a little bit flatter and less lifelike. So I turn it on immediately. Does it take away anything from the LS50? No, when properly integrated so the bassline from the sub can latch to the bassline from the speakers, it doesn’t do anything negative to the sound. But the road to achieving that is not necessarily easy. It sure took me several weeks to find the sweet spot for it and dial everything the way I want it to.

Finally, am I happy with my purchase or do I think I could’ve spent this amount of money in a better way? For the first part of it – yes, I’m definitely happy with it and I don’t regret a single dollar (euro actually) spent. As for the second part and spending this in a better way – honestly, I don’t have a clear answer to that. I don’t feel that adding a sub is a life-changing experience. It’s very nice for sure, but not something you can’t live without. So my train of thoughts on this matter goes along these lines – get your system up to your standards first. Make sure that you’re happy with its resolution, speed, tone color, layering, and soundstaging. Once you have done that and you feel that no significant upgrade could be made by investing those dollars into one of the main components (source, amplification, speakers), then you can think about adding a sub and lifting the whole experience slightly. And lifted it will be, fuller and more lifelike, but not essentially changed. But hey, you already knew that, right? We’re audiophiles, people used to pay a lot for small advancements, and enjoy them much more than a “normal” non-audiophile person would expect.


TYPE: Closed Box, down-firing driver
ACTIVE DRIVER SIZE & MATERIAL: 8 in. FibreAlloy™, 200mm long-throw, inverted alloy dust cap, steel chassis
INPUT CONNECTORS: High-Level Neutrik Speakon, Low-Level single RCA, LFE RCA
POWER OUTPUT: 125 watts (RMS)
Dimensions: 11.8 x 12 x 12.3 in., (300 x 307 x 313 mm)
NET WEIGHT: 31.5 lbs. (14.3 kg)
FINISH: High Gloss Black, High Gloss White, 5 coats

Official product page

8 thoughts on “REL T/5x – Do you need a subwoofer for Stereo?

  1. That picture is shaded by AI. You’re suggesting they’re your images?
    Soft/hard/bold – you bring yourself unstuck.
    Shame, because it’s a good sub. Your conclusion said you weren’t sure why the sound image benefited from having the subwoofer on.

      – The image is only for the illustration of what I’m talking about, it’s not mine because I’m not this talented and it would take me a lot of time to create similar before and after (that still wouldn’t be this good). Also not sure why you think it’s AI shaded but that is completely irrelevant to this analogy.
      – Next, not sure what the problem is with mentioning hard and soft pens. Generally speaking thinner and harder pen cores are used for sketching while softer and bolder ones are for shading.
      – As for the conclusion – yes, I understood the theory but I couldn’t fully grasp all the differences it would make until I tried it for myself.

You write: “KEF R3 will still handle big dynamic swings better than LS50 + REL”. Would that change your conclusion about adding this subwoofer to a system with larger speakers?
My system includes:
Hegel H190 amplifier
Kef R3 speakers
Room size ~18sq meters

    R3 has noticeably deeper bass than LS50. I believe that T7x would be needed to add any meaningful extension to them. T5x could enforce some frequencies that R3 is already doing so you could have even more bass quantity… But it will not add much in terms of reach and lowest and rumble below that threshold that R3 is already capable of.

if your system can’t play 20hz-20khz you are not getting the “entire picture” as the artist intended. a sub is a must in most setups.

I am not very sure if I really need a sub. My system is a pair of Monitor Audio Silver 200 (6G) driven by Cambridge Audio CXA 81 that is used for 80% jazz listening in a room of approximately 35 m2. Thank you very much, your review has been extremely helpful.

Your post is really informative,and i like your post a lot.Thanks a lot for sharing such a useful information.


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