Harbeth Monitor 30 Speaker measured by Amir of ASR

[ToTo Man]

There aspects of performance that affect "soundstage" which can be measured.
The aforementioned BBC dip is one of them – by artificialy exaggerationg or attenuating the presence region the phanton sources appear subjectively closer or more distant –, another is dispersion width and smoothness and the way it interacts with the room boundaries, etc.
But as mentioned by @h.g. the "soundstage effect" is significantly affected/enhanced by the acoustic properties and topographic characteristics of the room.
And because sharper image focus is achieved by toe-ing the speakers towards the listener, "imaging" and "soundstageing" tend not to go well together.

Just to make clear what I mean by "imaging" and "soundstage" (from Stereophile's Glossary):

imaging The measure of a system's ability to float stable and specific phantom images, reproducing the original sizes and locations of the instruments across the soundstage. See "stereo imaging."

stereo imaging The production of stable, specific phantom images of correct localization and width. See "soundstaging," "vagueness," "wander."

soundstaging, soundstage presentation The accuracy with which a reproducing system conveys audible information about the size, shape, and acoustical characteristics of the original recording space and the placement of the performers within it.

I believe dispersion must play a key role but wonder if crossover design is also of significant influence? It was a long time ago when I compared IMF Professional Monitor mk3 and IMF Professional Monitor mk4, two models that share identical drive units, similar enclosures (mk4 has more internal damping than mk3), but different crossovers (same XO frequencies but much higher component count on the mk4 crossover). The mk4 produced an image that was crisp and transparent but it seemed small/narrow and sounded like it was coming from the location of the enclosures with not much sound filling the spaces to each side or between. Whereas the mk3 produced an image that was slightly less transparent and more diffuse, but it filled the spaces to each side and between much more convincingly. Since both models used identical drivers and similar enclosures, one would expect dispersion to be extremely similar if not identical. I was therefore puzzled by the difference.

 

[h.g.]

Since both models used identical drivers and similar enclosures, one would expect dispersion to be extremely similar if not identical. I was therefore puzzled by the difference.

The brain uses a number of factors to determine the strength, location and environment for sound sources. Reflections play a major role but so too do the difference in loudness at the two ears, the difference in arrival time at the ears and how sound diffracts significantly differently around the upper body, head and ears with source direction (Head Related Transfer Function). Stereo gets the last two wrong and, as mentioned in the post above, a small dip will generally make it sound less wrong by modifying the effective HRTFs at the two ears. The small differences in your two crossovers are likely to be introducing small bumps and dips which the brain is similarly processing as differences in the HRTF and hence source location, width, envelopment,...

 

[AndyU]

The brain uses a number of factors to determine the strength, location and environment for sound sources. Reflections play a major role but so too do the difference in loudness at the two ears, the difference in arrival time at the ears and how sound diffracts significantly differently around the upper body, head and ears with source direction (Head Related Transfer Function). Stereo gets the last two wrong and, as mentioned in the post above, a small dip will generally make it sound less wrong by modifying the effective HRTFs at the two ears. The small differences in your two crossovers are likely to be introducing small bumps and dips which the brain is similarly processing as differences in the HRTF and hence source location, width, envelopment,...

+ head movements which stereo also cannot deal with, though I think 5.1 systems do a better job for center signals at least. Iirc it was Rogers who used to argue that you should toe your speakers in more than 30 degrees so that as you moved say to the left, you moved further off axis of the left-hand speaker thus counteracting to some extent the increase in volume caused by moving leftwards and so closer.

 

[cooky1257]

Regarding the BBC dip, this is taken from a piece written by H. D. Harwood (Harbeth's father) for the Wireless World magazine in 1976 titled "Some Factors In Loudspeaker Quality":

Context is everything and as I understand it this observation relates to BBC monitoring situation ie in the back of an outside broadcast van seated right on top of them.

 

[cooky1257]

I'd argue it's for stereophile to fork out on a Klippel rig rather than for amir to follow their methodology.
Crossover design can 'steer' the output of a speaker-as visible in the 3D rendering which indicated the lobing and cancelations.

 

[Nagraboy]

Context is everything and as I understand it this observation relates to BBC monitoring situation ie in the back of an outside broadcast van seated right on top of them.

But then it’s also valid for home listening. No-one sits as close to an orchestra as they do to their speakers at home.

 

[cooky1257]

But then it’s also valid for home listening. No-one sits as close to an orchestra as they do to their speakers at home.

Except that would imply every speaker without a BBC dip would be too in your face which isn't the case-btw I quite like the softening effect of the BBC dip.

 

[ToTo Man]

If the rationale for the BBC-dip to maintain perspective of the different rows of an orchestra is true, it seems like a very broad brush, downstream solution to fix a relatively specific upstream issue. Would changing the mic placement / recording technique not have been a better place to start?

 

[AndyU]

If the rationale for the BBC-dip to maintain perspective of the different rows of an orchestra is true, it seems like a very broad brush, downstream solution to fix a relatively specific upstream issue. Would changing the mic placement / recording technique not have been a better place to start?

It does seem a strange rationalization. What about all the other forms of music, and all the other possible venues?

 

[Dougal]

The M30.2 was £3895 but was a 'limited edition' and is now finished.

The M30.1 is £2995 in Cherry.

The measurements of all the models has improved noticeably over the 18 years since that M30 was produced.

Dave, have you had a chance to compare the M30.1 model against the M30.2 Anniversary? I wondered if they are essentially the same except for the finish and WBT binding posts.

 

[h.g.]

If the rationale for the BBC-dip to maintain perspective of the different rows of an orchestra is true, it seems like a very broad brush, downstream solution to fix a relatively specific upstream issue. Would changing the mic placement / recording technique not have been a better place to start?

Yes it would seem reasonable to expect a decent stereo recording to compensate for the effect in the recording in the expectation of it being played back on speakers with a flat response. However, as mentioned by someone in the comments, the dip in the Harbeths is almost certainly not to do with this BBC dip effect but to help turn down the directivity mushroom of a 2 way. Below the crossover frequency the midwoofer is beaming and above it the tweeter is radiating widely in all directions and so in a reflective environment turning down the level of the frequencies just above the crossover helps restore some perceived tonal balance. A much better way to address the issue is to use a waveguide to maintain a smooth directivity and a flat on axis response but a small dip can be a perceived improvement.

 

[Paul Burke]

Yes it would seem reasonable to expect a decent stereo recording to compensate for the effect in the recording in the expectation of it being played back on speakers with a flat response. However, as mentioned by someone in the comments, the dip in the Harbeths is almost certainly not to do with this BBC dip effect but to help turn down the directivity mushroom of a 2 way. Below the crossover frequency the midwoofer is beaming and above it the tweeter is radiating widely in all directions and so in a reflective environment turning down the level of the frequencies just above the crossover helps restore some perceived tonal balance. A much better way to address the issue is to use a waveguide to maintain a smooth directivity and a flat on axis response but a small dip can be a perceived improvement.

Agreed. Also the waveguide used to be able to lower the crossover point substantially when done well, without stressing the tweeter. Contributing to the midwoofer in a 2 way not beaming as much in the first place. Always a bit of a compromise in a 2 way, too small a midwoofer and no real bass extension and lack of headroom, or too large of one and having to cross much closer/into beaming and break ups etc

 

[hifi_dave]

Dave, have you had a chance to compare the M30.1 model against the M30.2 Anniversary? I wondered if they are essentially the same except for the finish and WBT binding posts.

Yes, have done that demonstration many times. AS reworked the crossovers of all the Anniversary models and so they do measure and sound slightly different to the standard models. It's not just components and finish.

The Anniversary models are now all, pretty well, sold out.

 

[Nagraboy]

It’s funny, all this theoretical stuff makes it sound like two-way speakers are fatally flawed, yet home listening to the Harbeth P3ESR for 8 years (and in recent weeks the M30.1) has been so enjoyable. The jump to the M30.1 has been quite an ear-opener for me re bass performance. I always liked the P3 bass performance and didn’t really find them lacking on acoustic and most other material either. I do play at lowish/moderate levels in a smallish room. The M30.1 has provided useful weight in the bass which has made Rock and Electronic music more involving. I’m yet to try symphonic music as it’s never been my thing. On small scale classical the M30.1 and P3 are delightful.

 

[tuga]

Some models like the LS5/8 from '79 had a flat response on-axis:

 

[Chris81]

LS 5/8 was an active design!

 

[h.g.]

*grabs popcorn and waits for Alan shaw*

Not sure we need Alan Shaw. Some of the natives are now getting upset at Amir due to his lack of interest in much of what engineers and scientists would consider important. Nonetheless let's hope he sticks at it and posts some more interesting factual information on speaker performance even if the accompanying words may leave something to be desired.

 

[Alex S]

All well and good but folks are gonna have a big shock when they buy Amir’s latest greatest measuring speakers and get them into their listening room that will have a far greater effect than any measured dip here or there.

 

[h.g.]

All well and good but folks are gonna have a big shock when they buy Amir’s latest greatest measuring speakers and get them into their listening room that will have a far greater effect than any measured dip here or there.

The point of more complete speaker measurements is that an informed user can use them to help determine which speakers are likely to work well in their room given their preferences. One can see the beginnings of this in the review where off-axis information is given more consideration and is subsequently used to predict a typical in room response. Earlier in this thread doing something similar with imaging was discussed. Unfortunately to develop this successfully requires technical/scientific knowledge and interest that Amir lacks. Whether he is interested or capable of finding and working with others that possess this knowledge and interest is debatable. Even if he doesn't more factual information on speakers is useful to those with the knowledge to work with it. The lost potential may upset the more scientific types but it is moving things forward a bit and perhaps someone else with a similar level of commitment and drive (you cannot fault Amir here) will run with it.

 

[tuga]

We already have Stereophile and Soundstage and AVHub and a few other British and German and French magazines making competent measurements.

Do we really need Amir's incompetent ones?