Interesting comparison
An interesting observation on the PD drivers.
I used the old version of the PD158 a lot and loved it, especially in open baffle.
It has a Mms of 107.9 g with a Bl of 27.3 giving a nice low (for a big 15 inch driver) ratio of 3.95. It was very easy to crossover all the way up to about 900Hz.
Now the new version PD.158
has a Mms of 85.2 g with a Bl of 25.3 giving a superior low ratio of only 3.36...Very good for a 98dB sensitive driver capable of handling 600 watts AES ( 2.4Kw peaks!)....
This newer version sounds even better but only up to a crossover point of about 350Hz to 400Hz....If you run it up to the same 900Hz crossover as the older version it starts to sound a bit rough, but only at high SPL, (above 103 ish dB peaks) so this may not bother a lot of potential customers.
Does this suggest that there is a sweet spot of Mms to Bl ratio? ie too low and cone break up becomes an issue....?
Too high and one loses the magic of the more dynamic & natural texture of the low ratio drivers....?
I am guessing here but the DDS horn might be nice match with this driver...?
Not my area but maybe worth looking at?
I have often thought the Polar graphs with this horn are very good, maybe Earl can comment?
Thanks
Derek.
An interesting observation on the PD drivers.
I used the old version of the PD158 a lot and loved it, especially in open baffle.
It has a Mms of 107.9 g with a Bl of 27.3 giving a nice low (for a big 15 inch driver) ratio of 3.95. It was very easy to crossover all the way up to about 900Hz.
Now the new version PD.158
has a Mms of 85.2 g with a Bl of 25.3 giving a superior low ratio of only 3.36...Very good for a 98dB sensitive driver capable of handling 600 watts AES ( 2.4Kw peaks!)....
This newer version sounds even better but only up to a crossover point of about 350Hz to 400Hz....If you run it up to the same 900Hz crossover as the older version it starts to sound a bit rough, but only at high SPL, (above 103 ish dB peaks) so this may not bother a lot of potential customers.
Does this suggest that there is a sweet spot of Mms to Bl ratio? ie too low and cone break up becomes an issue....?
Too high and one loses the magic of the more dynamic & natural texture of the low ratio drivers....?
I am guessing here but the DDS horn might be nice match with this driver...?
Not my area but maybe worth looking at?
I have often thought the Polar graphs with this horn are very good, maybe Earl can comment?
Thanks
Derek.
Those polars are useless for the most part, what can be seen doesn't look like any directivity at all.
I can agree that high BL in a woofer is desirable - actually BL/Re. There actually is science there. But I fail to see any science that says that lower cone mass is a benefit. "Micro-dynamics"? Really? Are we going back to talking about the mystical/magical aspects of loudspeakers?
I can agree that high BL in a woofer is desirable - actually BL/Re. There actually is science there. But I fail to see any science that says that lower cone mass is a benefit. "Micro-dynamics"? Really? Are we going back to talking about the mystical/magical aspects of loudspeakers?
Nothing magical i think. There's mass that has inertia and responds to the force applied with different speed. The further it is from instant the more obvious the effects. An infinitely powerfull amplifier could probably solve it, but in the real world - the ability of typical amplifier to precisely controll the cones is highly overrated...
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Its not magical at all. I agree. In fact it is pure physics and this is what happens:
In a band-limited driver like a woofer the required rise time is not instantaneous even if the input signal is. This portion of an impulse is handled by the tweeter. Hence, if the force is sufficient to move the mass at the required rate then the actual mass does not matter. How do we know if the force is sufficient? Easy, you look at the frequency response of the woofer and if it goes high enough - i.e. up to the crossover frequency - then the system has sufficient force to drive the mass up the low passed transient. If it were not sufficient then the frequency response would fall before the crossover point.
Amplifiers don't control cones. Cones are an independent mechanical system that is excited by the amplifier. There is some coupling but this is small because the loudspeaker is so inefficient.
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BL is the force factor - flux B times the length of wire in that flux L. The force on the cone is Force = BL X current.
Of course there are ways to measure the quality of a driver. FR alone is clearly not sufficient, but a full polar response and a look at the impulse response will usually tell you 90-95% of what you want to know.
High BL also implies that there won't be much modulation of the signal due to voice coil heating because there is usually a lot of L since there is a physical limit to B.
Informed Q&A is the only way forward
I am sure that there is much progress to be made in the area of correlating the physics / maths with perceived sound quality...I really believe both objective and subjective tests are required to make substantial progress.
Driver mechanics and electrical function are fascinating and I am the first to admit that some of the more complex maths involved is beyond my grasp.
But maybe some of the technical input from Earl who is far better qualified than most in this area, can be cross referenced with accurate and repeatable subjective tests?
What I am not suggesting is a whole bunch of us fire random questions at Earl and expect him to repeat basic points for the 100'th time...
But Dr Geddes is a great resource and if we (all of us who are willing to learn) can (a) respect his time and (b) offer something in return....Then maybe we can all benefit and progress together.?
What can we offer Earl...? Maybe man hours? ie collective experiences distilled down into a few important areas of study? Maybe by focusing on just one or two areas we can dispel some myths and move on....Happy days Earl!....Or, one of us might trigger a new line of thought for Earl to number crunch and possibly lead to progress?
Lastly a focus group of subjective opinions might be of use to Earl as a marketing / sales tool? At the end of the day customers listen first and only buy what they like the sound of, so knowing what sonic traits are the most popular might be of use?
I know I have a lot of maybe / might and possible in the last few paragraphs but surely there is a better way than the endless objective / Vs subjective debate which at best ends in a polite " agree to disagree" or at worst ends in loss of tempers and further alienation of the two schools of thought?
Sorry for the OT ramble ( again!) but maybe it might lead to better answers for us all.
Cheers
Derek.
I am sure that there is much progress to be made in the area of correlating the physics / maths with perceived sound quality...I really believe both objective and subjective tests are required to make substantial progress.
Driver mechanics and electrical function are fascinating and I am the first to admit that some of the more complex maths involved is beyond my grasp.
But maybe some of the technical input from Earl who is far better qualified than most in this area, can be cross referenced with accurate and repeatable subjective tests?
What I am not suggesting is a whole bunch of us fire random questions at Earl and expect him to repeat basic points for the 100'th time...
But Dr Geddes is a great resource and if we (all of us who are willing to learn) can (a) respect his time and (b) offer something in return....Then maybe we can all benefit and progress together.?
What can we offer Earl...? Maybe man hours? ie collective experiences distilled down into a few important areas of study? Maybe by focusing on just one or two areas we can dispel some myths and move on....Happy days Earl!....Or, one of us might trigger a new line of thought for Earl to number crunch and possibly lead to progress?
Lastly a focus group of subjective opinions might be of use to Earl as a marketing / sales tool? At the end of the day customers listen first and only buy what they like the sound of, so knowing what sonic traits are the most popular might be of use?
I know I have a lot of maybe / might and possible in the last few paragraphs but surely there is a better way than the endless objective / Vs subjective debate which at best ends in a polite " agree to disagree" or at worst ends in loss of tempers and further alienation of the two schools of thought?
Sorry for the OT ramble ( again!) but maybe it might lead to better answers for us all.
Cheers
Derek.
Not possible. Uncontrolled subjective 'reviews' are more than useless - they lack consistency and are subject to bias.
It is almost impossible to find someone who could consistently subjectively rate something with precision. Thats why we mortals need to subject ourselves to controls to have meaningful, workable 'data'. Be it blind AB comparison, ABX (for JND) or something else. Not happening in a hobbyist internet debate.
Why? We, as species have evolved so we constantly integrate all of our senses to form a conclusion. Also, more to a point, there is no evolutionary 'penalty' for overreacting to a non-existing stimulus. Other way around would have eliminated our ancestors from the gene pool pretty quick. So there you have it, we always debate some crazy ideas (cables, correctly functioning commodity parts, etc), even if there is no different stimulus going to our hearing apparatus. But sadly some don't realize, we constantly use all of our senses, not just hearing, and also MAKE UP DIFFERENCES WHEN THERE ARE NONE - no evolutionary penalty for doing that, remember? It's just human nature, we all have it.
It is almost impossible to find someone who could consistently subjectively rate something with precision. Thats why we mortals need to subject ourselves to controls to have meaningful, workable 'data'. Be it blind AB comparison, ABX (for JND) or something else. Not happening in a hobbyist internet debate.
Why? We, as species have evolved so we constantly integrate all of our senses to form a conclusion. Also, more to a point, there is no evolutionary 'penalty' for overreacting to a non-existing stimulus. Other way around would have eliminated our ancestors from the gene pool pretty quick. So there you have it, we always debate some crazy ideas (cables, correctly functioning commodity parts, etc), even if there is no different stimulus going to our hearing apparatus. But sadly some don't realize, we constantly use all of our senses, not just hearing, and also MAKE UP DIFFERENCES WHEN THERE ARE NONE - no evolutionary penalty for doing that, remember? It's just human nature, we all have it.
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"The God Species" ....
Hi Daniel,
Sadly you may be correct...I hope not but you do make some interesting points.
Maybe I was hoping "as a species" we could work better together on this small scale ( loudspeaker design) because I get so frustrated with the publics inability to accept overwhelming ( peer reviewed) evidence on Anthropogenic climate change....But that really is OT!!
Cheers
Derek.
PS The God Species is a peer reviewed scientific look at the humans impact on Earth and our precarious future....Awesome book!
Hi Daniel,
Sadly you may be correct...I hope not but you do make some interesting points.
Maybe I was hoping "as a species" we could work better together on this small scale ( loudspeaker design) because I get so frustrated with the publics inability to accept overwhelming ( peer reviewed) evidence on Anthropogenic climate change....But that really is OT!!
Cheers
Derek.
PS The God Species is a peer reviewed scientific look at the humans impact on Earth and our precarious future....Awesome book!
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We need a serious reflexion about our onthlogic nature... a standalone entity who need social interactions. It seems the complexity we maid takes hostages the substrate we need to live ! To convene the humanity in Standalone Personn to solve the problem is our "common" task...
Which is impossible because :
-individuality (persons or grups _ social or geographical)
- geoppolitacal interests
- verticaly social grups (as first some politicians and lobbys: economical or politicals ... ah our french comunism Greens
)- religion
A temptation could be to centralise... but this is dictature... :human being onthology is complex : competition but grup needed; There is a victim whic can not to be swap or re born : our substrate : the Earth.
I have the vertigo when I see we were 1 billion 100 years ago and now 7 billions... and we waste and talk about hifi... (I promiss I'm not a comunist even if I'm french
)complex but two cents here, sorry : one egoist bottle of wine with family and one Talisker for the End...
Could it be off topic ? Darwin reading is sufisant here...
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Correlation between objective and subjective assessments is essential. The problem is that we can never expect such a correlation if the subjective assessments are uncontrolled. You can only find correlation between stable variables.
A lot has been done in this area, but not nearly enough. The problem is the difficulty involved. It is a massive undertaking to do subjective studies. I have done a few and I can tell you that I won't be doing very many, if any, more. Only large companies can afford it. But then they have little to no incentives. I know this from the inside. Marketing will want to do listening panels and get preference inputs, but that is not reality, which is beside the point to marketing. It tells them which way the wind is blowing today and what the color trends are (like handbags for next year) and that is all they care about. Sound quality is not even on their radar as a real effect. Its all about what is perceived - as flawed as it is. If it all changes tomorrow - all the better - more sales. Do you think marketing would like to sell you "The last speaker you will ever buy!" - I think not.
So we have what we have and we must use what evidence that we have and move on from there. Maybe we can put together two pieces of data and find a third truth, but that is not always possible and there is no guarantee that it is right. But it is the best that you can do with what you have.
Toole and I disagree on one key area having to do with early reflections. There is scant data to support either of us, he has more if you look at his criteria, but I don't accept his criteria. For the vast 90% of the issues however we are in complete agreement. Surely we should all accept those areas where all the experts agree and then we can debate those areas where they don't.
I will always answer question posed from the perspective of "point me to where I might learn about this." But I will seldom answer questions when I am expected to do all the work. I also stop the minute that there is disrespect as I just tolerate that. It is never necessary and only shows contempt and ignorance. It is always possible for me to misunderstand a comment, that happens, but when its clear, I am gone.
Eldam - I could go on and on about cosmology and where we came from, but this is not the place.
A lot has been done in this area, but not nearly enough. The problem is the difficulty involved. It is a massive undertaking to do subjective studies. I have done a few and I can tell you that I won't be doing very many, if any, more. Only large companies can afford it. But then they have little to no incentives. I know this from the inside. Marketing will want to do listening panels and get preference inputs, but that is not reality, which is beside the point to marketing. It tells them which way the wind is blowing today and what the color trends are (like handbags for next year) and that is all they care about. Sound quality is not even on their radar as a real effect. Its all about what is perceived - as flawed as it is. If it all changes tomorrow - all the better - more sales. Do you think marketing would like to sell you "The last speaker you will ever buy!" - I think not.
So we have what we have and we must use what evidence that we have and move on from there. Maybe we can put together two pieces of data and find a third truth, but that is not always possible and there is no guarantee that it is right. But it is the best that you can do with what you have.
Toole and I disagree on one key area having to do with early reflections. There is scant data to support either of us, he has more if you look at his criteria, but I don't accept his criteria. For the vast 90% of the issues however we are in complete agreement. Surely we should all accept those areas where all the experts agree and then we can debate those areas where they don't.
I will always answer question posed from the perspective of "point me to where I might learn about this." But I will seldom answer questions when I am expected to do all the work. I also stop the minute that there is disrespect as I just tolerate that. It is never necessary and only shows contempt and ignorance. It is always possible for me to misunderstand a comment, that happens, but when its clear, I am gone.
Eldam - I could go on and on about cosmology and where we came from, but this is not the place.
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Did you read Kanneman - Thinking: Fast and Slow? That is what it is all about.
We have two ways to think, fast: reactionary, spontaneous, not very rational, etc. and slow: considered, rational, logical. Most people make rapid judgments about most things, we are all impatient. Do you think that they are likely to be correct or not? And we loath changing our minds!
One difficulty we have here is sharing the results : not data, but empiricals experiments. Which are already difficult without that, flawed by t many factors: subjective & cultural way of listening to, rooms, consitency of experiments... As a final check we must hear... it's individual & more individual than science which tend to do universal rule (but able to include in it subjectities interpretations).
Yes sorry for the two cents false philosophy, it's late here and Bachus was involved.... but I surmise one day Earth must be the place as no choice... oh s...t I continue (sorry !)
We have to be prudent about fast & slow... some makes slowly the same perpetual errors and others can make fast efficient statement...Culture is involved here in relation to each subject, difficult to apply this thought to fast marketing message e.g. and complex reasonment... We mix the both in many things but not necessarly in the same time. Have to be prudent about valor judgement in the way to have efficenty reasonment. Even Imagination e.g. can be involved in finding process in the most complex fundamental Sciences subjects !
Yes not a place about Cosmogony...
Yes sorry for the two cents false philosophy, it's late here and Bachus was involved.... but I surmise one day Earth must be the place as no choice... oh s...t I continue (sorry !)
We have to be prudent about fast & slow... some makes slowly the same perpetual errors and others can make fast efficient statement...Culture is involved here in relation to each subject, difficult to apply this thought to fast marketing message e.g. and complex reasonment... We mix the both in many things but not necessarly in the same time. Have to be prudent about valor judgement in the way to have efficenty reasonment. Even Imagination e.g. can be involved in finding process in the most complex fundamental Sciences subjects !
Yes not a place about Cosmogony...
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Dr Geddes,
A bit OT : What are your thoughts on coax/concentrics , esp if used with higher HP freq to reduce cone movements ? Coax/Concentrics would give equal horizontal and vertical dispersion as compared to waveguides , isn't it ?
Though based on what I have read about them, very few are good enough (like the KEFs and TADs....)
Thanks...
A bit OT : What are your thoughts on coax/concentrics , esp if used with higher HP freq to reduce cone movements ? Coax/Concentrics would give equal horizontal and vertical dispersion as compared to waveguides , isn't it ?
Though based on what I have read about them, very few are good enough (like the KEFs and TADs....)
Thanks...
Minimise cone travel & maximise efficiency...
Coming back to the specific question of midrange drivers size / Mms / cut off frequency / dispersion....
I have attached a couple of pics of an open baffle using a 15 inch Precision Devices midrange (100Hz up to 400Hz or 900Hz depending on model) with a heavier coned Beyma 15 inch covering the bass.
The Manger driver covers everything above 400Hz or any crossover point up to about 900Hz. The Manger could be easily swapped for a compression driver / horn or a full range driver.
I didn't use any horn or wave guide, just rounded baffle edges so there is no pattern control apart from the drivers natural dispersion, or in the Mangers case, lack of it!
In my experience here are a few key points relating to driver choice:
(1) Try to use the largest Sd and most efficient driver for any given bandwidth to minimise cone movement and minimise amplifier power input...I really believe this is important.
(2) Try to use the most efficient driver you can find / afford for any given bandwidth, again very important.
(3) Look at good Pro drivers which generally feature paper cones, cloth / fabric surround, lower moving mass and a higher Bl for a given Sd compared to HiFi / audiophile drivers.
(4) Rubber surround drivers are best below 150Hz (plus / minus 50 Hz depending on driver size) ...To be more specific here, even a good rubber surround driver like the Seas Excel range can be " bettered" by a good cloth surround range like PHL or Volt.
(5) Avoid driving any driver near its Fs if open baffle or Fb if in a box....Its ok to drive below Fb ( ELF principal) if the driver can handle the power and displacement required from the low end boost with Eq. Also watch the Q does not go too high...
(6) Only use passive crossovers as last resort....Active power amplification offers huge advantages over passive....99% of all high quality studio monitors and live sound loudspeakers are active...Passive crossovers are viewed as a joke...There are no successful commercial manufactures of high quality studio monitors....All our music is mixed / mastered on active monitors...Why would anyone choose passive???
(7) Take full advantage of modern DSP....DSP / crossovers / Eq offers huge advantages....Flexibility at both the design stage and the real world room / speaker interface, esp in the bass and with home cinema.
Hope some of this helps.
Cheers
Derek.
Coming back to the specific question of midrange drivers size / Mms / cut off frequency / dispersion....
I have attached a couple of pics of an open baffle using a 15 inch Precision Devices midrange (100Hz up to 400Hz or 900Hz depending on model) with a heavier coned Beyma 15 inch covering the bass.
The Manger driver covers everything above 400Hz or any crossover point up to about 900Hz. The Manger could be easily swapped for a compression driver / horn or a full range driver.
I didn't use any horn or wave guide, just rounded baffle edges so there is no pattern control apart from the drivers natural dispersion, or in the Mangers case, lack of it!
In my experience here are a few key points relating to driver choice:
(1) Try to use the largest Sd and most efficient driver for any given bandwidth to minimise cone movement and minimise amplifier power input...I really believe this is important.
(2) Try to use the most efficient driver you can find / afford for any given bandwidth, again very important.
(3) Look at good Pro drivers which generally feature paper cones, cloth / fabric surround, lower moving mass and a higher Bl for a given Sd compared to HiFi / audiophile drivers.
(4) Rubber surround drivers are best below 150Hz (plus / minus 50 Hz depending on driver size) ...To be more specific here, even a good rubber surround driver like the Seas Excel range can be " bettered" by a good cloth surround range like PHL or Volt.
(5) Avoid driving any driver near its Fs if open baffle or Fb if in a box....Its ok to drive below Fb ( ELF principal) if the driver can handle the power and displacement required from the low end boost with Eq. Also watch the Q does not go too high...
(6) Only use passive crossovers as last resort....Active power amplification offers huge advantages over passive....99% of all high quality studio monitors and live sound loudspeakers are active...Passive crossovers are viewed as a joke...There are no successful commercial manufactures of high quality studio monitors....All our music is mixed / mastered on active monitors...Why would anyone choose passive???
(7) Take full advantage of modern DSP....DSP / crossovers / Eq offers huge advantages....Flexibility at both the design stage and the real world room / speaker interface, esp in the bass and with home cinema.
Hope some of this helps.
Cheers
Derek.
Attachments
My comments on yours:
1) larger Sd is usually a good idea
2) Agreed
3) Agreed
4) Agreed, I would never use a rubber surround driver
5) this doesn't even make sense to me. Don't use near Fs? Why OK below Fs?
6) I agree that active can be made better, but that is not why everyone is doing it. they do it because it is cheaper. But the cheaper is a recent thing. Back in 2007 we built two sets of Summa one done actively and one done passively. They measured the same and sounded the same. But at that time an active box cost about $5000. Why would I or anyone else do something like that? Today with a miniDSP it costs about the same (excluding the cost of the extra amp) to do active versus passive. The actives that I do now measure just a bit better because of the high amount of flexibility that DSP offers. So while I can agree with you on this point, today, I would not have agreed just a few years back. I still sell about 50-50 active and passive. Many people don't like the extra wiring involved in active - you can't use a receiver anymore, which is why my personal speakers are still passive. Tom Danley still uses only passive crossovers in his stuff - it is not "a joke".
7) sure why not at todays low costs, unless you just don't want all those extra amps then passive is the only option.
1) larger Sd is usually a good idea
2) Agreed
3) Agreed
4) Agreed, I would never use a rubber surround driver
5) this doesn't even make sense to me. Don't use near Fs? Why OK below Fs?
6) I agree that active can be made better, but that is not why everyone is doing it. they do it because it is cheaper. But the cheaper is a recent thing. Back in 2007 we built two sets of Summa one done actively and one done passively. They measured the same and sounded the same. But at that time an active box cost about $5000. Why would I or anyone else do something like that? Today with a miniDSP it costs about the same (excluding the cost of the extra amp) to do active versus passive. The actives that I do now measure just a bit better because of the high amount of flexibility that DSP offers. So while I can agree with you on this point, today, I would not have agreed just a few years back. I still sell about 50-50 active and passive. Many people don't like the extra wiring involved in active - you can't use a receiver anymore, which is why my personal speakers are still passive. Tom Danley still uses only passive crossovers in his stuff - it is not "a joke".
7) sure why not at todays low costs, unless you just don't want all those extra amps then passive is the only option.
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