You could go with a smaller speaker and use waveguides to limit dispersion. Horns are basically doing that. At low frequencies the horn would need to be rather large.
Martin Logan's recommendation would bring into play more room acoustics, which would add a sense of spaciousness, but that sense of spaciousness would be the same for every recording, and is a step away from actual fidelity. David Griesinger, formerly of Lexicon, talked about that in one of his papers. I'd hesitate to over do that. It will blur imaging if that matters.
It seems counter-intuitive to say this, but less room reflections is not necessarily the goal. If you had only one reflective surface in a room causing comb filter effects, the cancellations might be 12dB deep (typical of my measurements), and less but still substantial at all the integral multiples of the fundamental cancellation frequency. If you then add another reflective surface to the environment randomly, it's probable that where in frequency one comb filter mechanism causes a 12 dB cancellation, the other comb filter mech won't have it's cancellation, so it somewhat fills in the cancellation from the first mechanism at the listening position. In real world typical listening rooms, there will be many reflective surfaces, some much more dominant than others.
I set up my stereo in a room with no carpeting one time, in an old victorian house, expecting it to sound awful. The room was very "live" with reflections. Much to my surprise it actually sounded very good. Significantly better than the carpeted room I had previously been in. There were so many reflections in this room that virtually all cancellations were largely filled in.
Down around 100HZ - 200HZ (the Shroeder frequency area), where half wavelengths fit between room boundaries, most rooms get into trouble. You'll only have one or two paths so maybe no real fill in potential. Bass gets "boomy". Although I haven't done it, I suspect that having two woofer towers may combat this pretty good. To illuminate the room on all 3 axis with bass frequencies. I notice that several high-end speaker companies are doing this (Infinity, McIntosh, etc.)
A separate issue is room ringing from the presence of parallel walls. The victorian had a bay window that lessened the amount of parallel wall surface area. Ringing didn't seem to be a big problem.
How did you implement the back wave reflectors?
I have mdf boards behind my Martin Logans angled at 45 degrees so it shoots the sound upwards. It makes the wall behind the speakers much less sensitive to rear wave stuff, i.e. putting acoustic foam there only makes a minor difference.
Thanks for explaining.
Keep in mind that the segmented ESL simulation includes LF boost from the proximity effect. Based on the curves I would guess you simulated at 1m. The array of 8 dynamic dipoles would experience a similar boost but it doesn't look like it was included in their SPL estimate.
I agree that at LF the main factor limiting SPL for dipoles is volume displacement(area x excursion). If the 8 dynamic drivers were spaced along the height of the ESL and their baffle was the same size as the ESL they would produce similar LF max SPL for for similar volume displacement limits. However, the dynamic driver array would not be required to produce high quality midrange sound. This frees up the option to include extended baffles edges(H-baffle, U-baffle...etc) which would boost LF output capability significantly.
The pictures of the panels in this link is the basic setup I used,
http://www.diyaudio.com/forums/plan...t-panel-angles-8-vs-9-panels.html#post2170405
I had also built up a top barrier using a bunch of stacked up heavy books and sealed the edges with some tape.
This worked well.
Then I tried to dampen the back wave even more by using some very thick (8" or so) fiberglass insulation but and it did help somewhat but if the insulation was within less than 10" from the diaphragm it decrease the fine detail and high end finesse that they have.
The setup became much bigger than it was worth for what I was trying to do, and logic told me that normal proper wall treatment is the only feasible choice for a larger panel.
You can put foam up on the walls behind them and this will help but it won't do anything for the lower midbass to bass frequency's depending an the type of foam you are using.
Here is a picture of the foam wall I once had and a crappy picture of one of my Apogee Duete's later positioned in front of it were the Piano was.
jer
http://www.diyaudio.com/forums/plan...t-panel-angles-8-vs-9-panels.html#post2170405
I had also built up a top barrier using a bunch of stacked up heavy books and sealed the edges with some tape.
This worked well.
Then I tried to dampen the back wave even more by using some very thick (8" or so) fiberglass insulation but and it did help somewhat but if the insulation was within less than 10" from the diaphragm it decrease the fine detail and high end finesse that they have.
The setup became much bigger than it was worth for what I was trying to do, and logic told me that normal proper wall treatment is the only feasible choice for a larger panel.
You can put foam up on the walls behind them and this will help but it won't do anything for the lower midbass to bass frequency's depending an the type of foam you are using.
Here is a picture of the foam wall I once had and a crappy picture of one of my Apogee Duete's later positioned in front of it were the Piano was.
jer
Attachments
Hi,
the dynamic dipole bass also profits from the inherently higher force/area it can put out.
It also profits from a cabinet (folded dipole), while a ESL-panel is best without wings or supporting cabinet structure (increase active panel area instead of fudging with wings et al).
Example:
A MartinLogan CLX and my smaller esl share a similar-sized-in-width mid-high panel.
But while the ML pairs a double membrane ESL bass panel, my esl features a dynamic dipol tower with 6pcs. of 6.5" drivers.
The outer dimensions of the CLX are ~180x65x37cm (over all), the esl measures 130x54x31, of which the bass tower takes up a footprint of just 22x15cm.
Due to active filtering the tower is equed either down to 35Hz wo. subwoofer, or 50-60Hz w. subwoofer.
Already with the 35Hz setting the dynamic capabilities exceed those of the CLX, not to talk about the higher precision and better definition around Fs due to much lower Q.
Set to 60Hz -which is the CLX´s lower bandwidth limit- the bass tower is close to its Fequal - the frequency where a dipole offers same SPL as a monopole.
Here, just 2-3 drivers would suffice to keep up with the Logan.
Don´t know about the THD, but that will probabely be worse with the CLX below 200Hz too.
Summed up, the dynamic dipole is smaller/more compact, more efficient and more precise.
jauu
Calvin
the dynamic dipole bass also profits from the inherently higher force/area it can put out.
It also profits from a cabinet (folded dipole), while a ESL-panel is best without wings or supporting cabinet structure (increase active panel area instead of fudging with wings et al).
Example:
A MartinLogan CLX and my smaller esl share a similar-sized-in-width mid-high panel.
But while the ML pairs a double membrane ESL bass panel, my esl features a dynamic dipol tower with 6pcs. of 6.5" drivers.
The outer dimensions of the CLX are ~180x65x37cm (over all), the esl measures 130x54x31, of which the bass tower takes up a footprint of just 22x15cm.
Due to active filtering the tower is equed either down to 35Hz wo. subwoofer, or 50-60Hz w. subwoofer.
Already with the 35Hz setting the dynamic capabilities exceed those of the CLX, not to talk about the higher precision and better definition around Fs due to much lower Q.
Set to 60Hz -which is the CLX´s lower bandwidth limit- the bass tower is close to its Fequal - the frequency where a dipole offers same SPL as a monopole.
Here, just 2-3 drivers would suffice to keep up with the Logan.
Don´t know about the THD, but that will probabely be worse with the CLX below 200Hz too.
Summed up, the dynamic dipole is smaller/more compact, more efficient and more precise.
jauu
Calvin
Huh .....
I agree with Calvin , if doing a panel speaker best to go hybrid if seeking SOTA sound , boomy bass is from bad application/design, radiating output has to be similar so if using sealed bass , best to use bipolar setup or if vented, rear firing ports , linesource application is good too , if panel cutoff is too high it will interfere with bass integration and lead to boomy bass also , you have to balance panel cutoff with xover and woofers acoustic center , if not integration will be poor and boomy ..
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The pictures of the panels in this link is the basic setup I used,
http://www.diyaudio.com/forums/plan...t-panel-angles-8-vs-9-panels.html#post2170405
I had also built up a top barrier using a bunch of stacked up heavy books and sealed the edges with some tape.
This worked well.
Then I tried to dampen the back wave even more by using some very thick (8" or so) fiberglass insulation but and it did help somewhat but if the insulation was within less than 10" from the diaphragm it decrease the fine detail and high end finesse that they have.
The setup became much bigger than it was worth for what I was trying to do, and logic told me that normal proper wall treatment is the only feasible choice for a larger panel.
You can put foam up on the walls behind them and this will help but it won't do anything for the lower midbass to bass frequency's depending an the type of foam you are using.
Here is a picture of the foam wall I once had and a crappy picture of one of my Apogee Duete's later positioned in front of it were the Piano was.
jer
Interesting Gerald, i have found foam kills the sound of dipoles fast , finding best to diffuse and leave rear wall live , if apply foam to problem areas i use very sparingly ...
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There's no such thing as a feasible dipole bass unless you have no interest in strong bass below 40 Hz - unless you are trafficking in lucky-spaced room resonances or piggy-backing on driver resonance for a one-note boost (as I do). Do the numbers.
Yes, you can design UNFEASIBLE subs with 3-inch excursions and 16 drivers and 60dB Linkwitz boosts at 20 Hz.
I wish all this loose talk about direct and reflected sound would start being coherent. The main issue is straightforward to anyone who has taken the time to read Toole (and if you haven't read Toole you should the decency and modesty to keep quiet).
The vicissitudes of the front sound are well known if not exactly as simple as they appeared before Gedlee's time.
The "rear" sound connects to the parameter of satisfaction known as ambiance. While that single word doesn't "explain" what is happening in all respects, it does provide a coherent framework for discussing the effects of rear propagation and control of absorption.
Ben
Ben
Yes, you can design UNFEASIBLE subs with 3-inch excursions and 16 drivers and 60dB Linkwitz boosts at 20 Hz.
I wish all this loose talk about direct and reflected sound would start being coherent. The main issue is straightforward to anyone who has taken the time to read Toole (and if you haven't read Toole you should the decency and modesty to keep quiet).
The vicissitudes of the front sound are well known if not exactly as simple as they appeared before Gedlee's time.
The "rear" sound connects to the parameter of satisfaction known as ambiance. While that single word doesn't "explain" what is happening in all respects, it does provide a coherent framework for discussing the effects of rear propagation and control of absorption.
Ben
Ben
I have taken the approach of building narrower panels instead of wide ones.
I like their horizontal dispersion characteristics better.
I also have started to employ electrical segmentation in my latest build as well, I just haven't gotten the needed resistors yet.
I also use a bit more D/S than most, 1.85mm is what my new panel is set and may need to be increased a little, as this will allow for more output at the lowest frequency's than your typical panel made just for the midrange and higher with a typical D/S of 1/16".
I can get really good performance down to the 150hz to 250hz range just at the edge of diaphragm\stator clipping with a D/S of 2mm (3/32") and a width of 3.25" (and a 9.75" length) or so, and it is quite loud at this point (est. about >105db at 1 meter).
To compensate for this I use a much higher Bias voltage as well.
And higher transformation ratios (1:150-250) as well are possible increasing the overall efficiency using smaller area panels.
When the panels width equals one wavelength or greater than the frequency being produced, Then the dispersion starts to transition form a figure 8 pattern in to a narrow beam and keeps getting narrower as the frequency rises.
It also produces main smaller lobes off to the sides as well.
I have no issues of getting a high output from my little panels even down to the 200hz to 300hz range, providing that the stator coatings are up to the task of with holding such high voltages and there is plenty of D/S spacing.
At the lowest Frequency's the output level is directly related to diaphragm displacement and of course the dipole cancelling effect otherwise it would have a circular horzontal dispersion because the diaphragms width is much much less than one wavelength of the frequency being produced.
Wings can help with this and in a small setup I have found that it can increase the low end output by as much as 3db.
I have had better luck with not ruining the sound quality by using reflectors directly behind the diaphragm than I have had trying to dampen the backwave with some sort of absorbing material that is close the the diaphragm.
The back pressures created from anything within about 10"-12" from the diaphragm would reduce all of the finest details in sound that ESL's are so well known for, in my earlier experiments.
Using wings will help with the low end roll off as per dipole action, But the width of the diaphragm itself will determine the horizontal dispersion effects (beaming) for the higher freqeuncys.
And the more the displacement, This helps with the low end.
It is obvious as to why ML suggests to toe out there speakers!!
Its due to the delays and refraction issues of using a curved panel.
When using a taller panel in a line source arrangement the top and bottom reflections from the ceiling and the floor give the impression of having a larger room such as mirrors would do using light waves.
Giving an extension to a virtual room, If you will.
At least that is the way I understand it from reading a lot material on the subject.
Having any space from the ends of the driver to the ceiling and floor is when the reflections are refracted differently and unequally.
FWIW
jer
I would prefer flat panel no more than 14 inch wide with wings and hybrid woofer design ...
When I went and listened to the Linkwitz Orion speakers, with very high quality program source, the midrange and treble were amongst the best I'd ever heard, but yes, the bass was barely there. Low bass was gone. the system I built is acoustically flat down to 20HZ, so I'm used to that.
The thing is, our ear-brain mechanism interprets sound substantially differently depending on frequency, so the idea that a panel speaker can only sound good with an OB woofer seems ridiculous to me. And the tube people say things don't intergrate well if you have a solid state poweramp on the woofer, and tubes on the rest. Naa... there are other variables at play.
Ideally a panel should go down as far as it can do well, maybe 80HZ if possible, before crossing over to a woofer. I say this because the panels will illuminate the room with lower mid and upper bass on all three axis, which should minimize boominess. Below 80HZ, the wavelengths are about 15 feet and larger, so MAY not have as many problems with room acoustics creating boomy bass. 60HZ might be significantly better for a crossover point.
I'm confident that Toole is pretty adept, and constantly studies and experiments, but nobody knows it all. Anyone should always take what they read with a grain of salt. Same thing with Linkwitz, and all the rest. Speaker design and room acoustics are very complicated. Many mechanisms at play. How we hear and comprehend everything is equally complicated. And then there's the recording side... All the same challenges in reverse.
I couldn't agree more. Actually, the problem is that aliens from Mars have been stealing the secrets from Toole's book and so when people read it today, some of those secrets are missing, esp in the middle chapters. If someone could convince the aliens to return the secrets, you could read Toole's book (which is essential reading as a pretty good compendium of everything known about speakers and rooms for music reproduction yet easy to grasp) and have ALL the secrets exposed to you.
I must thank whoever invented the web for giving me this opportunity to explain my views.
Ben
I must thank whoever invented the web for giving me this opportunity to explain my views.
Ben
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The B&W DM Model 70 Continental loudspeaker system.
Has anybody first hand experience with these old speakers?
Has anybody first hand experience with these old speakers?
This will happen if you have ,limited or no bass, the mid/highs take on excellent detail, but the tonal balance will never sound right ....
Hi Bob, I have a large room here with Acoustat 2+2's in it. Its approx 32'w x 80'l with mostly 12' ceiling, the room is open and live yet no echoing at all. I have my 2+2's aprox 20' from front wall and 5' off side walls, they are set with aprox .5" tow out. they image well, takes very little power to fill the room to 90db, The bass is something I have never heard from any other speaker I have owned, the big Aps and Infinitys, when moving them for postion I found that the bass at low freq went from deep tite bass sound into a waveform where as you feel the sound in waves on the body, I sit 50' from them. I feel there is a timing factor from the front wall that sets this all into play, exact timing creating a much lower bass response. Also they don't beam anymore, but I do get HF ringing now and then. Whats your thoughts on this? Thanks
More than satisfied with the bass, Like to get rid of the high freq ringing somehow, very hard to detect where it's coming from, ceiling is all acoustic tile, with glue lams every 12' about 2' deep, sometimes wonder if their creating it. Thanks for your response. Al
PS: Love your city. spent alota time down there with fellow GWRRA memebers.
PS: Love your city. spent alota time down there with fellow GWRRA memebers.
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My living room is about 20ft. X 12 ft. with a pretty standard I think 8.5 ft. ceiling (I haven't actually measured it). When I first moved in here I'd clap my hands and hear ringing in the upper midrange.
After a bunch of research I decided to put 2 inch diameter cotton rope (from a fabric store) in most corners of the room. I nailed it tight into the corners along where two or three walls came together. It killed the ringing very effectively.
Since cotton rope is very flamable, I can't recommend it, but Auralex makes 4 inch X 4inch X 24 inch foam pieces that should work even better. They also make 12 inch X 12 inch X 12 inch cubes that would be optimal for three surface corners (room corners). You might try that. I'd try doing the corners of the room first and see if you can hear the difference, especially the area around the speakers. Aualex also sells a spray adhesive you can use to glue the foam to the walls, which is allegedly removable without damaging the paint on the walls. There may be a cheaper product from Home Depot or (?) that will do the same thing. It's very important that the foam be tight to the wall surfaces or it won't work nearly as good.
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