cooky1257
pfm Member
OK one more time. Perhaps it would help if you looked on it as rather than testing individual speakers Toole was actually testing the listeners....
Speaker/Room Measurement Witchcraftery
- Thread starter S-Man
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cooky1257
pfm Member
Well given that very few have the facilities available to Toole and the Spinorama measuring capabilities at Harman they need to be 'serious'.
poco a poco
I'm Jim
I don't think it was the DM70s at the demos I heard as I remember those quite well. It was a bit over 40 years ago though, so my memory is a bit hazy, DM6s and DM70s were both in their range then so they could have tried it with different models at different demos and I don't know for how long they continued with this type of demo.
'Nothing new under the sun' as they say. I think Gilbert Briggs did this type of demonstration on a much bigger scale at the Royal Festival Hall in 1954 with multiple musicians and Wharfedale speakers. The Hall was apparently packed with listeners, only 60 watts of amplification was used, but listeners deemed it a great success!
I was only 7 then so even a bit before my time to report on
but when "Mary had a little lamb" first spluttered forth from from the horn of Edison's phonograph in 1877 people commented on how real it sounded! Did he measure the in room response first I wonder??? 
Purité Audio
Trade: Purite Audio
Edison used live versus recordings too.
https://blogs.loc.gov/now-see-hear/2015/05/is-it-live-or-is-it-edison/
Keith
https://blogs.loc.gov/now-see-hear/2015/05/is-it-live-or-is-it-edison/
Keith
John Phillips
pfm Member
The first part is true - but Toole made the connection between that part of what he documents under "the wisdom of the ancients" (quoting references back to 1936), and controlled subjective tests. And he (and his team) did a lot more which seems to get overlooked.
However I fear we may now be in a world where product differentiation sometimes trumps good technical practice.
For example, from John Atkinson in the Stereophile review of the B&W 804d (my emphasis):
"In 2004, I visited Bowers & Wilkins' Research Center, in the village of Steyning, West Sussex, nestling in the shadow of England's South Downs, north of Worthing. I was impressed by both the depth and the breadth of the engineering talent and resources I found there. There is no doubt in my mind that B&W's engineers can design a loudspeaker to have any response they desire. That the 804 Diamond does not have a flat on-axis response is thus a mystery. …"
And there are other manufacturers whose loudspeakers I have listened to which seem to make music sound striking and euphonic rather than reproduce it as neutrally as possible.
ToTo Man
the band not the dog
Going back to the topic of room measurements, I've noticed another interesting effect in REW's Room Sim feature. Increasing the absorption coefficient for all surfaces equally does not have the effect one might expect of leading to a smoother response at all listening positions. e.g. -
With my room dimensions and a fixed loudspeaker position, an absorption coefficient of 0.15 for all surfaces predicts the smoothest response is +/-11dB at 36% from the rear wall. If you increase the absorption coefficient to 0.2 for all surfaces, it creates a narrow but deep null at 96Hz which worsens the response to +/17.5dB at 36% from the rear wall (the optimum position is now +/-10.5dB at 41% from the rear wall). If you want to keep the original listening position of 36% from the rear wall and maintain a 0.2 absorption coefficient for all other surfaces, you need to significantly increase the absorption coefficient of the rear wall to get rid of the 96Hz null.
This is actually pretty much mirrors what I discovered when I placed a couple of 'Monster' absorption panels on my rear wall a few years ago, it created a deep null around 97Hz at my preferred listening position!...
With my room dimensions and a fixed loudspeaker position, an absorption coefficient of 0.15 for all surfaces predicts the smoothest response is +/-11dB at 36% from the rear wall. If you increase the absorption coefficient to 0.2 for all surfaces, it creates a narrow but deep null at 96Hz which worsens the response to +/17.5dB at 36% from the rear wall (the optimum position is now +/-10.5dB at 41% from the rear wall). If you want to keep the original listening position of 36% from the rear wall and maintain a 0.2 absorption coefficient for all other surfaces, you need to significantly increase the absorption coefficient of the rear wall to get rid of the 96Hz null.
This is actually pretty much mirrors what I discovered when I placed a couple of 'Monster' absorption panels on my rear wall a few years ago, it created a deep null around 97Hz at my preferred listening position!...
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camverton
pfm Member
Perhaps you can tell that to those who use the results of his research to make the point that Logan’s are poor loudspeakers. Logan’s can be set up to sound poor but set up well can sound excellent. It’s a bit silly to dismiss a loudspeaker based on sub optimum setup, and it is the loudspeaker that some people are seeking to use the results to criticise, including Toole in one of his videoed lectures. Rather like not setting the boundary controls correctly on a D&D speaker and then claiming that the bass was poor because it was out of phase.
I have had three pairs of Logans, one still in daily use, so I do know how tricky they are to “get right”. The rewards, however, are great for those who bother. Whilst I like them for the sound they can produce they aren’t necessarily my favourite speaker. If shopping now with unlimited funds I would be listening to MBLs from the middle of the range up (excluding the extreme, £250k is just silly and I might have to cut a hole in my ceiling to accommodate them!), or the current models of Quad electrostatics which I found sound much better than the older versions. The problem with them, for me, is not one of sound but the look of two large panels in the room. I would certainly have a listen to Logan’s from higher up their current range but then the prices don’t compare favourably with Quads. If I was always listening with a group of people rather than on my own the Logan’s would be very low on the list and the MBLs high. Horses for courses.
Another point does occur to me, and that in these days of easy and high quality DSP the intrinsic frequency response of a speaker is less important as we can manipulate it to preference or what is considered correct. What is less easy to manipulate is the interaction of the speaker with the room and that is down to taste. No right no wrong, just preference based on how we hear and what we as individuals are trying to achieve.
camverton
pfm Member
Very interesting, thanks. The room sim feature is a handy tool and a great way to find a good starting point for listening and speaker positions. Fortunately, I have found actual measurements in the room don’t look quite as frightening as the sim predicts. Not surprising in that our rooms often aren’t a simple box with consistently reflecting coverings on each wall, and of course there is the arrangement of furniture to take into account. I usually end up with the sub in the best position as predicted by the sim tool, but with main speakers adjusted for my ears. Mind you I do use these odd speakers that some very rudely refer to as effects boxes
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Purité Audio
Trade: Purite Audio
I can’t see how absorbing bass would create a null?
Keith
tuga
Legal Alien
It would be fine if the problems with the BnWs were only a tailored frequency response. But as it often happens frequency response anomalies are the result of problems in other areas or the result of topology choices (i.e. hard cones and first order crossovers).
ToTo Man
the band not the dog
The guys at GIK didn't believe it either until I showed them my measurements (REW didn't have a Simulator back then, otherwise I could have used it to corroborate my findings!).
From a starting point of 0.15 absorption coefficient for every surface, a null at 96Hz gets progressively deeper until the coefficient for every surface reaches 0.21, then it begins to get progressively shallower as the coefficients are increased further. Also, the 96Hz null appears more responsive to absorption on the side walls and less responsive to absorption on the front and rear walls or floor and ceiling. E.g. doubling the coefficients of the floor and ceiling from 0.21 to 0.42 improves the null by 19dB, doubling the coefficients of the front and rear walls improves it by 22.5dB, but doubling the coefficients of the side walls improves it by 25.5dB.
PS - My experiences also agree with @camverton in that the actual in-room low frequency response is never quite as bad as the Simulator predicts, so obviously the lossy characteristics of the typical domestic room must equate to a coefficient factor that's greater than the 0.15 that REW defaults to. I therefore usually increase the coefficients by a few percent until I get a curve that's as close a match to my in-room response as possible.
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The speaker's directivity can't be altered by processing of the signal sent to the speaker, so the character that imparts to the sound remains.
camverton
pfm Member
I don’t quite follow. I was referring to the frequency response curve, which can be altered easily. The impulse response can also be modified, to some degree, by software such as Dirac. I am not quite sure what you mean by directivity, so rather than assume, perhaps you could elaborate. Many thanks.
March Audio
Trade: March Audio
Off axis response. Which is very important. Major reason why the logans are problematic.
March Audio
Trade: March Audio
There are plenty of alternative excellent speakers out there that don't suffer the significant issues of the logans, which even in your own admission are very difficult to get to work. So dismissing them would be quite a pragmatic and understandable response.
We get the idea you love em but the criticism of how they perform and their inherent unpredictability depending on precise location of the speakers, the listener and the room reflectivity is valid.
So can we move on?
The way the frequency response changes off axis, there are a few ways to define it - Nyal Mellor covers them in this article.
cooky1257
pfm Member
If the axial response is substantially flat, the inverse of the directivity index gives a useful approximation of how the speaker will measure in a room.
Directivity index is pretty fundamental to the area of Toole's work we have been discussing. Understanding what DI is is pretty 'page 1' if you intend to follow let alone question Toole's work.
camverton
pfm Member
Thanks, and for the link. I was reluctant to make assumptions but that is what I thought you mean’t and I agree.
Indeed, it is what makes Martin Logan’s a challenge if more than one listener. However badly some perceive them and their measurements they have given me much listening pleasure over the years, and their entry model is lower in price than Quads and particularly MBLs. That Martin Logan are a long established company may indicate that I am not alone in enjoying their sound. Oddly enough their variable off axis response means that they can be tuned for taste and done right can give exceptionally realistic sound, albeit with a narrow sweet spot. So many things are a compromise and pushing the envelope in one direction can mean limitations in others.
In the end it is knowing what works for us as individuals and measurements can help in that quest but nothing can substitute for listening in our own unique living space.
Indeed, it is what makes Martin Logan’s a challenge if more than one listener. However badly some perceive them and their measurements they have given me much listening pleasure over the years, and their entry model is lower in price than Quads and particularly MBLs. That Martin Logan are a long established company may indicate that I am not alone in enjoying their sound. Oddly enough their variable off axis response means that they can be tuned for taste and done right can give exceptionally realistic sound, albeit with a narrow sweet spot. So many things are a compromise and pushing the envelope in one direction can mean limitations in others.
In the end it is knowing what works for us as individuals and measurements can help in that quest but nothing can substitute for listening in our own unique living space.
Ayya Khema
pfm Member
toole test was all made in basically very poorly treated room. in a untreated room, flat on axis response and smooth off axis is very important.
in a treated room, i suspect Logans, or other planar/hybrids with flat on axis but less then ideal off axis might work extremely well.
concerning toole, he only showed listener preference in untreated rooms and i pretty much agree with him. but i may be tempted to think that in a well treated room, panel speakers could be extremely good.
to me its like testing cars in snow. the best car in the snow will not be the best car on dry road.
EDIT: now the vendors will come and say that dsp can replace a well treated room and this is simply ridiculous.
in a treated room, i suspect Logans, or other planar/hybrids with flat on axis but less then ideal off axis might work extremely well.
concerning toole, he only showed listener preference in untreated rooms and i pretty much agree with him. but i may be tempted to think that in a well treated room, panel speakers could be extremely good.
to me its like testing cars in snow. the best car in the snow will not be the best car on dry road.
EDIT: now the vendors will come and say that dsp can replace a well treated room and this is simply ridiculous.