from Harbeth 30.1 to SHL5+, an upgrade or lateral move?

I wouldn't call it a lateral. The SHL5+ are more expensive and bigger. I think it really depends on the type of music you listen too. I use to owned a pair of Harbeth C7s and I was thinking about upgrading to the SHL5+ because they were a better match for my taste in music (from classical to jazz to EDM to pop to reggae), which frankly is all over the place. The 30s were never in play for me. The SHL5+ gave me that added bass that the 30s were just not able to produce. The 30s I admit sounded a bit more refined in the details but honestly though your choice of amp would make a bigger difference. The mid range on both are truly beautiful. If you’re like me in terms of music, the SHL5+ maybe a better match. What kind of music do you listen too? For me, in the long run I wanted speaker that were full range so I ended up buying a different set of speakers all together. I do miss the Harbeths. Good luck!

To me, the SHL5+ is somewhat of an outlier in the Harbeth line.  It sounds quite different from their other speakers--it has a more modern, conventional sound (not as warm, tighter sounding and punchy bass).  I like the SHL5+, even though I don't like most modern speakers, but, the only Harbeth I really LOVE is the 40.2 (very much NOT a modern sounding speaker). 

I've owned the Monitor 30s and the SHL5s and I really think it's a matter of taste.  The 5's have a bigger, fuller sound that some might describe as less "accurate" than the M30s.  The 5's are also more forgiving of lesser electronics, IMO.  Depending on your setup and room, the differences could be minimal.  Frankly, I would want a home audition before dropping the kind of money they're getting now for the 5s.  When I bought mine they were 4k.  

Unless you are ready to step up to 40.1's, I'd keep the 30.1's and get a decent subwoofer, as that will get you closer to the 40.1 sound than buying SHL5+.  I've owned the SHL5's (non + version), and am now on my second pair of 40.1's, which I love and have no intentions of selling.  The SHL5's were nice, but not in the same league as the 40.1's IME.

I moved from the C7ES3 to the SHL5+ and it was certainly an upgrade. I will never buy a pair of 40/1 as long as I live because they're too large for my room. I'm also running a REL B3 and a class A Accuphase so things aren't too shabby around here. If you have plans of some day purchasing a pair of 40.1's, I'd keep what you have an get a sub like pdreger suggested. Ultimately an in home demo would be your best bet but we know how hard that is.

Thank you for your valuable advice. I dont have chance to audition, all I can is read comments, reviews and order from audiogon, ebay... that's why all your answers are of great help to me. So for now,I guess I will buy a sub or upgrade amp, source for 30.1s. I the future when my budget for audio is bigger I will think about 40.1s :). 
Thank you again!

I had SHL5s some years ago and didn't really like them - I found them rather soft and woolly sounding, particularly in the bass. I sold them and moved on to something else for a few years.

More recently I came to hear the M30.1s and ended up buying a pair. I love them. They are far more neutral and natural sounding than the SHL5s in my 4 x 5m room. Bass is not all that deep, but it is tight and rhythmic. The M30.1s are also more extended and cleaner in the treble, and the midrange is more refined and more transparent.

So, personally, I would consider the SHL5 a downgrade from the M30.1s. But I wouldn't discourage you from hearing them - they may just be what you are looking for. But I agree with others that an amplifier or source upgrade may be a better option.

The M30.1s are truly amazing speakers and I would be interested to know why you are feeling the urge to upgrade them.

The SHL5 Plus does not sound soft and woolly as the SHL5. The bass of the SHL5+ is fuller, deeper, tighter and punchier than the M30.1. The largest difference or transformation between the SHL5 and SHL5+ is in the bass department apart from better integration between the drivers which in turn produces an overall smoother and more coherent presentation.

the shl5+ extends lower and have better bass overall. id say its a upgrade to go from 30.1 to shl5+.

I agree on many above and think that the shl5+ is like a 30.1 (wonderful midrange) but with deeper bass and more 3D feeling. I would want switch some day.

I'm shopping Harbeths actually too; after auditioning the 7s, 30.1, 40s, and SHL5+; I found much of the feedback in this forum to be spot-on.  I'm finding that selecting the "right" Harbeth to be really music, personal taste dependent. I listen to classic rock and really like the bass extension and treble of the SHL5+ compared to the other Harbeths, very noticeable.  I second the "sub" suggestion for consideration if you're satisfied with most of your music genres and the 30.1.

To Rossb: The type of music I listen to is classical , jazz, vocal, pop. I agree with you that 30.1 has a very refined and natural  midrange. However, I feel the urge to upgrade because the soundstage of 30.1 is not wide (it could be due to my small room: 12 x 15 feet) and contrabass in jazz sounds weak and thin, which makes the song does not have the necessary bass. 

Do you experience the same on your 30.1 pair? I am using Quad 99 and 909 for it. 

@quanghuy147
In that size room you should give a listen to the smaller P3ESR. Bigger is not always better. I've owned larger Harbeths and preferred the P3's in my smaller room!

@quanghuy147 It looks like you gotten some solid advice.  Per some earlier suggestions, why don't you try using a subwoofer first.  If you have audio stores that will allow you to audition at home, great.  If not, go to BestBuy or Crutchfield and try out one of their subs.  If you think it improve the sound and gets you closer to what you're looking for, keep it or consider buying a higher end like a REL or JL subwoofer. Many Harbeth owners use REL in their setup, just like @donjr.  It's a great combo.  I usually don't like the idea of buying something to return, but without any real brick and mortar shops to audition equipment, not much of a selection or not much of a choice.    

I know all the discussions here are centered around comparing the speaker models but if you really like the sound of your current speakers and just need more bass, you may want to try a different amplifier - or even a preamplifier, to see if they can plug that missing bottom end. I don't know the what the output impedance of the Quad amplifier looks over the frequency range but if they were designed to match/support the weird impedance curve of the Quad speakers, it may simply not be a good match for the Harbeth speakers. Just something to consider.

"Do you experience the same on your 30.1 pair? I am using Quad 99 and 909 for it. "

I mainly listen to classical and jazz. I find the soundstage perfectly fine, but then soundstage is not something that concerns me too much.

I also find the bass to be satisfactory. Obviously, the 30.1s do not go very deep, and a bigger speaker or subwoofer would go much lower. But I don't find the bass with the 30.1s "weak" or "thin".

As others have suggested, it could be an amplifier issue. I'm not familiar with your Quad amps, and I'm using Exposure (MCX preamp and 3010s2 power amp). It might be worth trying another ampllifier to see if this improves things.

I agree with all the comments here. I was trying to buy the 40.1 a few years ago but could not afford them so I bought the SHL5+ in the fall of 2015. They are driven by my Audio Research Reference 75 and the soundstage is really great. Bass will never be like the bigger Harbeth's but these are so musical that i'm sure that if I ever sell them, i will deeply miss them. I hope to upgrade now to the 40.2 soon. Will be great if I can keep both.

Hi all, this is a follow up after 1.5 year using 30.1 .

To recap, I had problem with bass of 30.1, it was 'thin' and 'weak', i was disappointed with it and wanted to move to other speaker (SHL5+)
However, last week, a friend suggested me to use power conditioner in my system. I never believed in the power conditioner of any kinds but I still bought one because this friend has long been sensible in choosing audiophile equipment.

After getting a power conditioner from eBay, I put it in the system. I played tracks that I usually played to see if there is difference brought by the power conditioner.

Here are the improvements that I notice:
- the bass is noticeably stronger, more defined- musical instruments are separate, also, their positions on the stage are more pin pointed.
- the background is darker- the mid bass is revealed, I never knew I missed this range of frequencies and did not  much understand when people talked about "mid bass" 
The music is now more musical, especially the guitar is more romantic.

Everything is just like I have upgraded to a better amp or better DAC. Or to put it simple, the difference is like when you view the same picture in 720p and in 1080p. Everything is sharper, more beautiful. Now I have no complain about the bass of 30.1 anymore. Together with the marvelous mids and highs, I know I am going to keep these speakers for a long time. :)

FYI, the power conditioner I bought is a used Richard Gray Pole Pig, I used it with a RGPC High Tension power cable. I paid about $600 for these.

I believe there are other power conditioners that can make the same improvements, if it's possible, please share your experience with your power conditioner so we have more options to choose regarding the power conditioners.

Thank you all.

Best,
Huy.