Hello dear,
thanks for contributing to this post so enthusiastically. I see your points guys. But as a mathematician/statistician I don't trust this graphs. These are based on models which only take into account 50% of the story, the other 50% is room (as mentioned before). I listen to music in my room, I don't need to sell my projects, so I just don't care what happens under anechoic conditions.
Today I and an expert with a CLIO we measured again this MCA15RCY on a 40cm baffle getting 90db at listening point (2.2mt distance, about 38 degree off-axis), the driver is mounted asymmetrically wrt the center of the buffer. The FR is flat (+/- some usual fluctuation) from 300Hz to almost 3K, I am sorry but this is what we measure. This is consistent with what Troel Gravesen has found. Moreover if I add two 5cm legs to the sides of the baffle (to form an U shape) with the these two sides internally covered with egg-foam the linearity becomes even better.
Anyway, my post started from a question which had nothing to do with FR. I am concerned about distortions caused by excursion. And the question was put an HP or to no HP at 300Hz in order to prevent excess excursion?
I tried to play 50Hz, 100Hz, 200Hz and 300Hz pure sine tones as suggested before in the thread. At low level I cannot hear any distortion or strange sound, at high level with the pure 100Hz I can hear some strange artifact which is probably distortion... now I wonder whether the same volume position will produce an insane pressure when a real music program is played. So I tried to play 500-2KHz white noise with volume in the same position when the 100Hz signal was dirty, I honestly cannot listen to this level, so I imagine it is insanely loud! So in absence of a distortion/excursion measures... I will probably keep the xover simple and let the midrange work without a high pass.
I have to say that while this MCA15RCY is considered a midrange it has a rather low resonant frequency, it seems more a mid-bass. The reason I love the sound of this driver is its transient behaviour, it is one of the most dynamic midrange I have ever heard... thanks to its large acceleration factor it has ( I mean the ratio BL/Mms*1000).
Best Wishes
Pierre
thanks for contributing to this post so enthusiastically. I see your points guys. But as a mathematician/statistician I don't trust this graphs. These are based on models which only take into account 50% of the story, the other 50% is room (as mentioned before). I listen to music in my room, I don't need to sell my projects, so I just don't care what happens under anechoic conditions.
Today I and an expert with a CLIO we measured again this MCA15RCY on a 40cm baffle getting 90db at listening point (2.2mt distance, about 38 degree off-axis), the driver is mounted asymmetrically wrt the center of the buffer. The FR is flat (+/- some usual fluctuation) from 300Hz to almost 3K, I am sorry but this is what we measure. This is consistent with what Troel Gravesen has found. Moreover if I add two 5cm legs to the sides of the baffle (to form an U shape) with the these two sides internally covered with egg-foam the linearity becomes even better.
Anyway, my post started from a question which had nothing to do with FR. I am concerned about distortions caused by excursion. And the question was put an HP or to no HP at 300Hz in order to prevent excess excursion?
I tried to play 50Hz, 100Hz, 200Hz and 300Hz pure sine tones as suggested before in the thread. At low level I cannot hear any distortion or strange sound, at high level with the pure 100Hz I can hear some strange artifact which is probably distortion... now I wonder whether the same volume position will produce an insane pressure when a real music program is played. So I tried to play 500-2KHz white noise with volume in the same position when the 100Hz signal was dirty, I honestly cannot listen to this level, so I imagine it is insanely loud! So in absence of a distortion/excursion measures... I will probably keep the xover simple and let the midrange work without a high pass.
I have to say that while this MCA15RCY is considered a midrange it has a rather low resonant frequency, it seems more a mid-bass. The reason I love the sound of this driver is its transient behaviour, it is one of the most dynamic midrange I have ever heard... thanks to its large acceleration factor it has ( I mean the ratio BL/Mms*1000).
Best Wishes
Pierre
You're absolutely right, you should also take the room into the equation! Room reflections affect the frequency response a lot more than the baffle shape, the worst being the first floor reflection, which is also the most tricky reflection to do anything about. Who wants a diffusor or absorber on their floor? I dont....
The speakers need to illuminate the room uniformly to mask (not remove) its effect. The human hearing ignores second replicas of sound, but not if they're different. Thus smooth polar response is very important.
The smoothest polar response I've measured and heard is actually the omnidirectional Pluto. And in some area like imaging they are better than the dipoles I've built. They sound almost holographic. In this area the closest match I've got is using extremely narrow baffle (20cm).
I'm curious about your 250Hz suckout and I've never encoutered it after many builds. The only 'dip' I got is 100-200Hz which is easily solved with 100-200 shelving highpass as per Orion and Phoenix, and is due to half-space to full-space transition. Is it anything to do with U-Frame response?
Hi, not sure what you meant. My finding is that the relative (not absolute) size of driver vs. baffle is the dominant factor.
In my earlier post, an 8" on 24cm baffle works as well.
I would guess a 10" driver on 30cm baffle may work too, but measurements will be needed to confirm.
I guess the question is what driver you are using below the mid, and where are you crossing it in? Ultimately, you would want to measure the completed loudspeaker to make sure the two drivers are integrating well. Usually, 'anechoic' measurements are part of the process to make sure things are working as planned, but I always check in room measurements too - below 300Hz (generally), the room can cause a lot of problems.
White noise has a larger amount of high frequencies present, so it may sound a bit louder than music at the same volume (which generally has more low/mid frequencies).
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I was trying to resist getting into the narrow vs. wide baffle debate again. I do not buy into the importance of the relationship between driver size and baffle width and the potential negative impact on off axis performance if the baffle is wider then recommended.
So I ran an experiment. I took my MathCad model of the Fostex FE-103E and Eminence Alpha 15A two way passive OB design and calculated the response on axis, +/- 30 degrees off axis, and +/- 60 degrees off axis. I think this design violates most of the rules of the "cult of the narrow baffle" in that the baffle is very wide compared to the full range driver diameter and even worse the full range driver is offset closer to one edge.
I lined the plots up vertically from -60 degrees to +60 degrees in 30 degree increments and compared the responses, the on axis response is optimized to be as flat as possible. The responses were very close to symmetric with the biggest anomoly as a function of angle being the directional response of the FE-103E driver rolling off the high frequencies as you move off axis. But that effect is due to the driver geometry and not the relative baffle width, it would be present in any width baffle. The rest of the differences were not very big and nothing stood out. There were no big humps or severe dips as shown in some of the measurements, simulations of single drivers on a baffle, or SL's drawing that were presented in previous posts.
In my opinion, focusing on only baffle width as a function of driver diameter is ignoring many other more significant variables. If you design your OB system taking into account baffle size and shape, driver size and location, crossover frequencies and slopes between drivers then there is no reason not to expect a relatively symmetric smooth SPL radiation pattern that is free of significant humps and dips. You need to factor in all variables and not base the design on a plot produced by the EDGE and some guess work.
rule of thumb: baffle width <= 2x driver diameter is not meaningful
In general, I would agree with Martin - baffle width is not the only thing to consider. But I fall in the 'narrow baffle' camp.
The point to remember is that above the baffle peak, off axis frequency response becomes irregular. Whether this matters is up to the designer. Also, my impression is that it is very difficult to accurately simulate the off-axis response, due to particulars of the driver's frame. I can say that all my measurements showed significant irregularity off axis above the dipole peak, and effect the mid, but especially the tweeter (if it is a dipole tweeter).
The point to remember is that above the baffle peak, off axis frequency response becomes irregular. Whether this matters is up to the designer. Also, my impression is that it is very difficult to accurately simulate the off-axis response, due to particulars of the driver's frame. I can say that all my measurements showed significant irregularity off axis above the dipole peak, and effect the mid, but especially the tweeter (if it is a dipole tweeter).
My first OBs were actually large baffles it follows natural intuition and they sounded good at that time after moving away from box paradigm. But it went a lot better later on with the iteration to smaller and smaller baffles. It's not a 'cult', it's a finding.
MJK, do you have measured on and off-axis response, and not only simulation?
Hi,
The foam is a good idea, it suppresses resonances.
This driver sounds very good. You can use the MCA15 on an open baffle, just take care about the crossover frequency and its slope. 300Hz seems to me the extreme limit with a high slope, I am afraid at high level, it can be yelling. I would use it above 500Hz with a second order high pass filter. You should make test with a crossover.
This is a response on-axis of two 5" on my open baffle project.The driver is offset on the panel (40cm width).
The responses are quite different. I think, it is difficult to place a small speaker on a large panel but not impossible. Polar response and bass limit are two opposite parameters to optimize for the designer.
Ok but you cannot ignore anechoic conditions because you cannot ignore the phase between the drivers.
The foam is a good idea, it suppresses resonances.
This driver sounds very good. You can use the MCA15 on an open baffle, just take care about the crossover frequency and its slope. 300Hz seems to me the extreme limit with a high slope, I am afraid at high level, it can be yelling. I would use it above 500Hz with a second order high pass filter. You should make test with a crossover.
This is a response on-axis of two 5" on my open baffle project.The driver is offset on the panel (40cm width).
An externally hosted image should be here but it was not working when we last tested it.
The responses are quite different. I think, it is difficult to place a small speaker on a large panel but not impossible. Polar response and bass limit are two opposite parameters to optimize for the designer.
Off axis response 600 - 3500 Hz
Thanks for responding Ang
I’ve looked into line arrays a lot. James Griffin has a really good paper on guidelines of designing line arrays for living rooms, “Design Guidelines for Practical Near
Field Line Arrays”. Not written for open baffles, but as long as there’s enough driver Vd in the bass, it should apply to open baffle line arrays.
Dynamic capability is very important to me too.
From Griffin: Small multiple drivers in with parallel/ series connections have these advantages:
- Provides higher power sound pressure levels
- Reduces distortion, as power is dispersed among several drivers
- Enables higher power handling to be attained
Comb filtering occurs at frequencies > a wavelength corresponding to the centre to centre distance of the drivers.
With the Fountek FR88-EX that I’m considering (which had excellent test results at zaphaudio) its nominally 3”, but from side to side it’s 88 mm (3.46”). That corresponds to a wavelength of c 3900 Hz. So to avoid comb filtering, I’d crossover to tweeters at say 3500 Hz.
It hadn’t occurred to me to double up the mids. As a rough indicator, 8 * 3” drivers have 1.7 times the cone area of a 6.5” driver; so 85% of the area of two 6.5” drivers.
However to run over the range say 600 - 3500 Hz, I suspect I’d get as good or better dynamics, and better off axis response.
If I’m wrong, please let me know.
Thanks for responding Ang
I’ve looked into line arrays a lot. James Griffin has a really good paper on guidelines of designing line arrays for living rooms, “Design Guidelines for Practical Near
Field Line Arrays”. Not written for open baffles, but as long as there’s enough driver Vd in the bass, it should apply to open baffle line arrays.
Dynamic capability is very important to me too.
From Griffin: Small multiple drivers in with parallel/ series connections have these advantages:
- Provides higher power sound pressure levels
- Reduces distortion, as power is dispersed among several drivers
- Enables higher power handling to be attained
Comb filtering occurs at frequencies > a wavelength corresponding to the centre to centre distance of the drivers.
With the Fountek FR88-EX that I’m considering (which had excellent test results at zaphaudio) its nominally 3”, but from side to side it’s 88 mm (3.46”). That corresponds to a wavelength of c 3900 Hz. So to avoid comb filtering, I’d crossover to tweeters at say 3500 Hz.
It hadn’t occurred to me to double up the mids. As a rough indicator, 8 * 3” drivers have 1.7 times the cone area of a 6.5” driver; so 85% of the area of two 6.5” drivers.
However to run over the range say 600 - 3500 Hz, I suspect I’d get as good or better dynamics, and better off axis response.
If I’m wrong, please let me know.
Hello Dears,
last night we tried a further experiment: placed the speaker 50cm to the side wall and 50 cm to the back wall. The off-axis response (from the listening point) became horrible! My optimal placement is at least 1mt from side/back walls.
The idea of building up such a speaker has got me after an experiences with the Dalquist DQ10 which has a closed box for the range <=500Hz, and OB going up from this point. The DQ10, even if very hard to drive, is one of my favorite.
But a five months ago I had a revelation! I had the chance to audition the Nola Accent Baby Grand reference (http://www.nolaspeakers.com), a lucky friend of mine who lives on the Sorrento's Coast bought a pair of these completed with a pair of custom made closed box active subwoofers for the extreme low-end. The sonic experience I lived was under controlled conditions, I know this guy's room/equipment very well. This is the best dynamic loudspeaker I have ever heard. Impressive image, details, and HUGE dynamic from low to high frequencies. These speaker are based on the idea that the mid-high should operate with open back.
I think the NOLAs cannot be considered a pure OB design, isn't it? As you see from the pictures the back emission of the mid (4.5" drivers on a 12" baffle) is partially absorbed by a cover which plays the role of "mechanically" filter out what happens in the back/side, however this "no-box-design" let the driver "breath". Guys you could "touch" the voice of Jim Morrison with your hands.
I am not a fan of OB designs. I listened to all sort of OBs, even with posh drivers such as PHY-HP. But letting the midrange breath... this is the goal. I played around with several mids, what I learned is that if you close the box the micro-dynamic in this department disappear! Now, what is the best way to "open the back" of a 4/5" drivers seems to remain an unanswered question!
Best wishes
Pierre
last night we tried a further experiment: placed the speaker 50cm to the side wall and 50 cm to the back wall. The off-axis response (from the listening point) became horrible! My optimal placement is at least 1mt from side/back walls.
The idea of building up such a speaker has got me after an experiences with the Dalquist DQ10 which has a closed box for the range <=500Hz, and OB going up from this point. The DQ10, even if very hard to drive, is one of my favorite.
But a five months ago I had a revelation! I had the chance to audition the Nola Accent Baby Grand reference (http://www.nolaspeakers.com), a lucky friend of mine who lives on the Sorrento's Coast bought a pair of these completed with a pair of custom made closed box active subwoofers for the extreme low-end. The sonic experience I lived was under controlled conditions, I know this guy's room/equipment very well. This is the best dynamic loudspeaker I have ever heard. Impressive image, details, and HUGE dynamic from low to high frequencies. These speaker are based on the idea that the mid-high should operate with open back.
I think the NOLAs cannot be considered a pure OB design, isn't it? As you see from the pictures the back emission of the mid (4.5" drivers on a 12" baffle) is partially absorbed by a cover which plays the role of "mechanically" filter out what happens in the back/side, however this "no-box-design" let the driver "breath". Guys you could "touch" the voice of Jim Morrison with your hands.
I am not a fan of OB designs. I listened to all sort of OBs, even with posh drivers such as PHY-HP. But letting the midrange breath... this is the goal. I played around with several mids, what I learned is that if you close the box the micro-dynamic in this department disappear! Now, what is the best way to "open the back" of a 4/5" drivers seems to remain an unanswered question!
Best wishes
Pierre
No one's going to tell anyone how to suck eggs
Build 2 dipoles, one wide and one narrow then measure and compare them. I don't trust simulation. They are accurate up to certain extent only.
http://linkwitzlab.com/faq.htm#Q24
Step 2,3,4 can take quite sometimes.
Don't take narrow baffle as a philosophy. It's simply a requirement to achieve a specific goal. If one does not want the goal, he wouldn't need to meet the requirement.
Build 2 dipoles, one wide and one narrow then measure and compare them. I don't trust simulation. They are accurate up to certain extent only.
http://linkwitzlab.com/faq.htm#Q24
Step 2,3,4 can take quite sometimes.
Don't take narrow baffle as a philosophy. It's simply a requirement to achieve a specific goal. If one does not want the goal, he wouldn't need to meet the requirement.
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