Harbeth Monitor 30 Speaker Review

[Francis Vaughan]

Yet another boring supposed re-invention of the wheel. Yawn. It's been done before, bigger, better and with greater skill by the Japanese over 30 years ago.

To be fair. The BBC designs the Harbeths are based upon are pre-date the Sony designs by at least a decade. Harbeth has been in business most of this time, so I don't think Sony can make any early claim here. Tuning the panels in such a manner is a pretty well understood idea. Mechanical Engineering 101 stuff.

 

[thewas]

You can have acoustically quite dead loudspeaker enclosures also with intelligently designed high stiffness combined with some internal damping.

Here for example the Stereophile measured enclosure vibrations of some Harbeth loudspeakers



(sources: https://www.stereophile.com/content...-anniversary-edition-loudspeaker-measurements
https://www.stereophile.com/content/harbeth-super-hl5plus-loudspeaker-measurements
https://www.stereophile.com/content/harbeth-p3esr-loudspeaker-measurements
https://www.stereophile.com/content/harbeth-m401-loudspeaker-measurements =

and here of some other modern designs which combine high stiffness with appropriate damping


(sources: https://www.stereophile.com/content/kef-ls50-anniversary-model-loudspeaker-measurements
https://www.stereophile.com/content/technics-premium-class-sb-c700-loudspeaker-measurements )

The Harbeth, Spendor etc solutions are practical and reasonable solutions from times where FEM, modal analysis etc. were due to price and lack of computational power not feasible to most, but nowadays there exist also other and better ways.

 

[Shadrach]

Conversely, in a thin-wall cabinet, the lossy joints (i.e. removable baffle/back and the generally 9-12mm thin panels used throughout the box) each act as an acoustic hairline crack. They inhibit the build-up of resonance. Simple as that really!

Yeah but it isn't as simple as that though is it. Instead of having what might be modeled as a single resonant mass you now have at least 6 of them.
Separating one from another doesn't stop them resonating.
Once you add absorbent panels, you now have a capacitor in effect and it discharges.
Lots more problems with thin panels including vibration of the front baffle and that you are left by default with a non sealed enclosure.

 

[DSJR]

Hi everyone. I've been in and around this industry for nearly half a century now and have lurked here for some months, finding the reviewing approach such a welcome alternative to the gushing subjectivism elsewhere (I'm still caught between the two stools though - ouch!)

With regards to the original M30, can I suggest you look at the LS5/9 design this model was marketed as a drop-in replacement for? It's all on the HUG if anyone's interested and I don't wish to tread on anyone's toes, but in the 80's, the BBC seemingly designed speakers for *themselves* and not necessarily others. the LS5/8 and smaller 5/9 definitely had an upper mid dip engineered in for various reasons (HiFi News have a test confirming numerous subsequent published response plots done at various places and published on the HUG) and it's my understanding and subjective experience that the M30 refined this balance into the gentle but more 'seamless' downtilt (mid-bass to hf) as measured here, the current Graham LS5/9 putting the tweeter balance somewhere in between, the HiFi World 'squashed' plot done a few years back showing the mid bass rise but fairly flat thereafter.

I've directly compared my own Rogers LS5/9's to M30's 'side by side' and later, to the M30.1. Subjectively, there's no doubt of the superior subjective blending of bass unit to tweeter in the Harbeth M30 and the 30.1 definitely sounds and measures? a little livelier while keeping the smoothness of driver integration, the 5/9's I have sounding a bit 'scrappy' and 'loudness switch balance' in comparison.

P.S. Current Harbeth models do seem to sound a little livelier than before (flatter in response?), the product line more evolutionary over the years rather than massive changes. Hope this helps from a subjective anecdotal view. In addition to the Rogers 5/9's, I also have Harbeth SHL5 (again, warmer and more obviously 'organic' tones than the current model - online reviews of my 'version' now gone in favour of the current type) and a pair of inherited and antique Spendor BC2's which I sold to the original owner as a Saturday Boy in a higher end UK audio store back in 1974, which have the lovely lower mids of the classic BC1, but not as well integrated elsewhere for a variety of reasons.

 

[Shadrach]

Hi everyone. I've been in and around this industry for nearly half a century now and have lurked here for some months, finding the reviewing approach such a welcome alternative to the gushing subjectivism elsewhere (I'm still caught between the two stools though - ouch!)

I thought you liked a bit of subjective gushing Dave.

 

[Boatswain]

Interesting to look at the distortion graph.

 

[Thomas_A]

Please do not kill the messenger...

Still find the range 5kHz to 10kHz a bit conspicuous
View attachment 47555

I've not read how the Klippel adjusts above 1 kHz when gating is used, but for "normal" measurements such regular dips/peaks appearing on different speakers can be caused by reflections from small protrusions close or around microphone stand/attachment. Anyway, I believe the measurements are fine and I would say within +/-1 dB given all possible errors together is excellent.

 

[Deleted member 65]

Friend of mine have the Rogers LS3/5a in his vinylrig, very enjoyable with acoustic/vocal music. Terribly expensive nowadays though.

 

[Krunok]

Thanks @amirm Re: "The tweeter is always "faster" so it generates a response first." I am not sure what you are saying there. I presume you mean that the tweeter arrives first because it is closer to the mic than the woofer. i.e. the acoustical centres are offset with the tweeter arriving first then the woofer. This is typical of most systems that are not "time aligned" (and can't be fixed with eq).

Why do you think the situation you described with difference in acoustic centres cannot be solved with phase EQ?

Take a look at my Harlech's, both woofers are playing up to 1800Hz but one is firing upwards, so acoustical centres of woofers and tweeter differ very much:

But I still managed to get pretty nice step response (measured at LP):

 

[Francis Vaughan]

Yeah but it isn't as simple as that though is it. Instead of having what might be modeled as a single resonant mass you now have at least 6 of them.
Separating one from another doesn't stop them resonating.
Once you add absorbent panels, you now have a capacitor in effect and it discharges.
Lots more problems with thin panels including vibration of the front baffle and that you are left by default with a non sealed enclosure.

Nitpick. Adding a damping panel does not add a capacitance. It adds mass and resistive losses. There is already an equivalent RLC system made up of the panel's internal losses, mass and springyness. Adding a damping panel simply changes the RLC parameters a bit. Modelling a coupled set of panels is really pretty easy, and so long as the wavelenths are long wrt the cabinet (which they are for these purposes) it isn't hard to build a fully coupled model including the driver, box volume, and any port, as needed. No need for FEA. You could run an equivalent model in SPICE with little effort. Even back in the early 80's this was bread and butter stuff. In the 60's you could even run it on an analog computer (although I would be impressed if anyone did such a thing for a speaker design.) And in the end, you measure what you have built and see how well it fits the modelling, and tweak the modelling as needed.

 

[Krunok]

Due to low output at the frequency from the speaker, the ambient noise protrudes:

View attachment 47602

The error is well below -20 dB so I have not bothered to find the source and quiet it down.

That would probably be because of those "self-generated winds due to previous meal" you mentioned in your 1st post. I suggest avoiding beans to further lower ambient noise.

 

[Purité Audio]

There are a whole series of these BBC papers , identifying requirements, detailing specs etc.
http://downloads.bbc.co.uk/rd/pubs/reports/1979-22.pdf
Keith

 

[DSJR]

I thought you liked a bit of subjective gushing Dave.

How do I know you sir?

I only joined in because in this particular case, I feel there were genuine design decisions as to why this model was balanced the way it is and how this balance has been 'adjusted' in subsequent models according to reviews and my own comparisons. One model perhaps where the Quad-style 'tone tilt' adjustment could possibly come in handy (yes I know conventional tone controls would do the same)...

 

[thefsb]

This specific speaker came out around 2002 I think and cost US $3,200 around that time.

Each?

 

[tomtoo]

They are shure not on the cheap side. But me they give the impression of a solid produkt.
Have some kind of charakter. Measure better than i thought. I can understand that some people love them.

 

[617]

Keep high resolution! Do you feel that's the difference? No windowing needs to be applied to impedance measurements since there's no acoustic measurement being made. Mine are routinely better than 1 Hz, as are impedance traces other builders share with me from the web. A tester would have to go out of their way to make the measurement low resolution, for no real purpose.

I understand how frustrating it is fielding questions about test outcomes from so many visitors. So, please take the following solely in the spirit of trying to help, sharing some of my experience in this area.

Vibration can create chaotic signatures in the impedance trace. For example, vibration is very hard to control in free air measurements for Thiele Small parameters, causing noisy impedance traces that look similar to the Harbeths. I was discussing this with Ken Kantor many years ago, and he shared same experience "You really need to kill any parasitic vibration in the driver to get a clean, symmetrical impedance curve"

This usually doesn't affect in-box measurements, since mounting the driver steadies the frame enough to avoid these artifacts, so I usually wouldn't suspect this. However these wiggles could be caused by a vibration somewhere in the speaker itself, for example loose driver bolts (I understand its an older model)? Or perhaps very high measurement levels causing non linearities to be excited.

As well, room reflections if large enough can also affect the impedance sweep. Please see figure 5d and the analysis here:
http://pub.dega-akustik.de/ICA2019/data/articles/001506.pdf
View attachment 47544

Comparing signatures with the Harbeth:
View attachment 47547

This shouldn't affect the substantive outcome (doesn't appear to affect frequency response measures), but just food for thought.

This is very interesting. I always knew 'in theory' that room reflections could impact impedance but it's weird seeing that actually happen. Most of the time impedance sweeps are done at a very low level (the device I use is powered from USB; the sweep is very quiet) and as a result the graph is quite smooth. I am all in favor of high resolution impedance sweeps (small resonances can sometimes be smoothed out) but I would do them at a lower level in order to exclude room effects.

An impedance sweep is one of those things which is useful to designers but not that useful to consumers; Amir is providing the minimum impedance and phase angles and even that people can read too much into.

 

[anmpr1]

When I read the first line and saw 2002, I immediately jumped to a conclusion that this would measure like a well used 18 yo speaker - and not as it was when it left the factory. Is this incorrect? Does speaker performance deteriorate over time?

Electrolytic capacitors in crossovers could dry out. Woofer surrounds often deteriorate over time. Either can be easily replaced. Electrostatic panels are said to have issues with membrane stretching over years. Of course any type of speaker can be overdriven and damaged.

 

[ahofer]

I posted this thread in the HUG forum, under the M30.x topic. It didn't get past the moderator.

I love my Harbeths, but I found that disappointing. Not the first time, either.

 

[Purité Audio]

Some manufacturers aren’t always appreciative of independent measurement.
Keith

 

[anmpr1]

I posted this thread in the HUG forum... It didn't get past the moderator. I love my Harbeths, but I found that disappointing. Not the first time, either.

I never heard of HUG but found this disclaimer: Please consider that there are commercially sensitive issues that we cannot discuss in an open forum.

I guess objective measurements are one of the commercially sensitive areas that can't be discussed.

PS: How 'open' can a forum be if discussion is closed?