How about the B+W PV1D?

PV1D

A unique take on subwoofer design, PV1D uses two opposed drivers in a super-rigid enclosure to deliver fast, clean, firm solid bass 

VANDERSTEEN SUB 3

https://www.vandersteen.com/categories/subwoofers

For my 30.2's I got a JL Audio F110v2. It mates nicely with the Harbeth sound, can't even tell it's on or where it is. Just sounds like the 30.2's with a bit more bass. So that's probably the biggest trick, matching to the Harbeth voicing. I had a Volodyne that did not sound good with the Harbeth, it was a good sub, it just didn't blend well. 

But there are plenty of good subs out there, it's just that this match worked out well for me.  Wish you luck on your search. I'd love to know what you end up with.

many would say mon 40’s do not need subwoofer bass support, but get a pair of rel’s if you must

Why would you need a sub with those Harbeths? They should sound good just as is...

needing a sub and wanting a sub are two separate camps…I initially tried it just for fun and found adding a sub to be a total game changer. 

Have you called Harbeth or visited a local retailer to listen?  I personally like REL because of their high level connection.  I makes sense because they act like woofers if dialed in right.

@jl1ny

Exactly. I want the clarity the Harbeth’s bring ,however, also want the ability to emulate the feel of a live concert where the kick drum is focused and hitting you in the chest like Thor’s hammer.... 🎉

The question is do I need 2 or just 1 ....my room is Medium large ,but open ended on one side , in the process of treating it as best I can...

I've never felt the need for subs with my 40 series, but if I were to go down that path, I'd look at REL.  Sounds like you may prefer a different kind of speaker... maybe some large JBL's or Klipsch Cornwalls.

@pdreher

I have a pair of Tekton Encores which give the concert vibe , but the Harbeth’s sound is unmatched...they do sound killer , just looking for that extra bump on "Bro Night" 😉

@tommypenngotti 

My room is smaller than yours and I’m using a Rel S/510 with my Reference 3A monitors. space permitting Id go with two of them. The Rel S Line is awesome, musical, fast and dynamic. It blew away the T-9X that it replaced.

@jl1ny 

Sounding like the Rel S line deserves a listen , musical and focused as opposed to boomy...thanks 

@tommypenngotti 

Absolutely zero boom. Rel actually is spot on with their claim of it’s sonic characteristics .

@jl1ny  

good to know ....I have a cheaper SVS PB1000 & its not really focused at all, more of a HT kinda deal it would be ok ....you get what you pay for....

thanks! 

What a mess..Snappers running harbeth? Guess that's why your asking for sub ideas,lol...Have you watched videos on how the rel drivers are made on that particular sub you reference...

@missioncoonery

I watched a Rel video...Do explain oh Audiophile Overlord....

You don't need a subwoofer(s), but a parametric EQ.  For most pop/rock music the punch in the kick drum is in the mid-bass frequencies, say 100 to 160Hz.

I just replaced a Velodyne with a RELS812.  Just one 

unreal.  Don’t know why I waited so long

medium sized room. Everything got clearer

just killer

good luck

Willy-T

i would agree with the sentiment that harbeths (specifically including the mon 40s) should be driven with a high grade powerful solid state amp, if the best bass response from the speaker is to be had

while not a particularly hard load to drive, the speakers are not very efficient @ 85 db/w/m and at mostly 6 ohms impedance (down to about 5 ohms in narrow band of midbass), most tube amps won’t control the bass driver too well, if asked to play at good volumes

...and others replying about subs with other (smaller) harbeths, well those are a totally different can o’ worms, so to speak - the op query is about using the 40’s - c7, super 5 and p3 owners are in a completely different universe of bass response...

How big is your room? SVS ported subs are pretty amazing for the price. If you want the concert feel, ported subs are for you.

All the best.

JD

I must agree - my 40.2's have all the bass (and more) than I'll ever want.  And... they simply must be driven and controlled by a high power SS amp, with a high damping factor (4000 for the H590).

My 30.1's also sound superb with the H590.  

They almost have too much bass - but, that's probably the room / placement.

I'm running two JBL 2269H 18 inch drivers in two custom cabinets that are based on the JBL SUB18 cabinet.  My sub cabinets are passive, ported cabinets.  Crossover is a McIntosh MEN220 and the 18's are driven by a McIntosh MC500.  I have a concert level kick drum feel in my living room if I want it and the subs will completely integrate and "disappear" for all the rest of my critical listening.  Nothing like JBL low end...but it must be set up right.  Crossover point and slope is critical to good integration.

I highly recommend 2 subwoofers.  This has improved my system immeasurably.  I had big problems with base at 60 and 120 hz. due to room sizes. I use 2 Definitive Technology super cubes 4000. I have tried KEF, SVS and Sony but can hear nil difference. Using 2 smaller subs helps with speed and balance, I also use a Minidsp, whilst I resisted for years this has been a revelation. Removing the bass to my main speakers below 70 Hz has improved their dynamics and pace, I cut the room node frequencies by 6dB and roll off the bass starting at 40dB.  You can also try altering the phase of 1 or both subwoofers.  

I can’t really comment on the 40.3’s but I did sub my SHL5+’s. Two B&W ASW-610 subs directly underneath definitely did the trick. It took a little while to hone them in but it seriously added the punch you so desire. For the 40’s you may want to size up a little. Since my Mac C2700 allows for additional outputs I activated a second output and can turn them on or off at will. Most of the time I leave them on but there are a few Lp’s and especially CD’s out there where the bottom end is pretty enhanced already. Best of luck.

deadhead1000 04-29-2022 at 04:49pm 

 I had a Volodyne that did not sound good with the Harbeth, it was a good sub, it just didn't blend well. 

willy-t 04-30-2022 at 04:42pm 

I just replaced a Velodyne with a RELS812.  

Willy-T

Which model Velodyne subwoofer did you use?

@jheppe815 

I like that set up....bet it thumps !

Mr. Penngotti,

You and I are kindred spirits. I also like the music loud with a good thump from the kick drum. The good news is that it is doable. The bad news is that it is not quite as simple as just adding a subwoofer, though that is a good start.

In my opinion you do not need to buy expensive subs. I like the SVS SB4000. I also like Rythmik, but they don’t do loud as well as the SVS.

Regardless of what brand you end up liking, multiple subs will help minimize a lot of the room acoustic issues you could run into when you introduce powerful low end into your system.

Liking it loud with a strong low end will more than likely cause you to push your system too it’s limits so I would also be looking at subs (as well as all of your gear) that have actual balanced inputs. If you really want to achieve arena levels, you will need every bit of gain you can find and having a balanced system really helps with that.

Down the road I would look into some type speaker management system to limit the band width that your Snappers need to reproduce so they don’t get eaten alive trying to drive those Harbeths full range.

You can pm me if you have questions.

Installing subwoofers requires an even frequency response with limited decay to get tight bass. Multiple subs and feature sets included is subs are other tools to make this happen. With my limited experience I would suggest a larger subwoofer like the s812 or larger. I had an S510 with 15" main speaker woofers. While it was fine, it did not match the 'presence' and output of my speakers as well as my larger subs. 

@jl1ny

Sorry to interrupt but I am curious in what way is the S510 better than the T9. Room setup was the same for both models?

I agree that dynamic kick drum thump is doable without a sub (kick drums don’t go that low).

I was able to achieve this without subs by fixing the room and repositioning the rack on the side wall...nothing between the speakers but carpet. I also had a fantastic room at the time.

It’s not just the bass that hits hard, everything else comes into focus as well. I was able to achieve this with Salk Songtowers with 5" woofers. I no longer needed or wanted a sub. Funny thing is that I was not looking to improve bass...just trying to see what moving speakers to the other side of the room would do to imaging/clarity.

I would add the sub after you figure out optimum placement and room dynamics. I did it without software but it was a lot of trial and error over the span of a year.

The Tannoy 10" woofers in my current room could not touch the bass of the Songtowers 5" woofers in the old room.

So I ended up going with (2) 18 Eminence Tour Grade subs / BSS FDS 310 Crossed over at 80 , Crown Macro-tech 2400 powering the subs. Sounds super tight & focused and I have that concert level kick drum now...I can always ease in the subs or pull out as needed...very happy. 

Some of these Subs like the REL S/812 seemed kinda pricey....an Emminence $250 speaker in a shiny powered cabinet doesn’t seem worth $3200?

Yes it's quite expensive but it delivers.  It's the performance that matters. Some costly hifi may not perform up to expectations and that's money wasted. I have a single S510 and it transformed the listening experience. The old sub that it replaced cost close to $3k MSRP back in 2009 and there's no comparison.

@ryder 

that's awesome and exactly my final conclusion , if it sounds good to the listener , then you have arrived, good for you ! 

from what I heard, for the most part, subs are cheap thrills (cheap subs). Listening fatigue will be off the charts if it’s too deep. So far I heard two types: powerful, in your face subs I don’t like or subtle subs I can’t hear (and sometimes I got it right.) I am waiting for an ELAC to try it with a remote.

@grislybutter 

Good point, my subs are pretty great and you can adjust so not "in your face" 

Subtle subs = what's the point? agreed. 

All good points. It’s hard to explain and I presume more knowledgeable or experienced folks would be able to describe it better. My old sub can be considered as poor as it is either too "in your face" or too subtle. If the bass sticks out too much, it’s unwelcome bass as the excessive bass which sticks out like a sore thumb is making more harm than good. If it’s too subtle, you can’t hear a difference. Good subs which are able to blend in well with the main speakers will make their presence felt, and the bass won’t feel like it’s detached or separate from the main speakers. In other words it’s a perfect seamless bass. A deeper, more defined and satisfying bass without anything sticking out too much like Home Theater the-bigger-the-better bass.

I had Harbeth SHL5+ with 2 RELT9i and the sound was very big and punchy.  I am well versed in technical subwoofer integration and ultimately the best I could do still had compromises.  A subtle but noticeable slowing down of the micro dynamics and transient speed of the main speakers, easily heard when the subs were switched out.  An occasional overbearing bass despite perfect level matching, basically either too loud or not loud enough as if the levels could not be finely enough tuned.  Granted I am a very particular listener and you might find these issues a compromise worth having.  You may be best served with an amplifier that can grip the 40s so that they can deliver the bass by themselves which they are capable of.  A Rotel Michi for example.  

My final answer was a pair of full range highly efficient british towers with special flared bottom port for sub bass and they do the job well.