diy esl suggestions thread

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Im going to attempt a DIY ESL build! Ive searched and even bought Roger Sanders book, but still have some specific questions.

Im looking to build an extremely high output 250/300hz-20khz+ (may augment with a line source super tweeter if ESL performance is abyssmal and price permits) ESL. I have the space for ~16" x 7'.

What is the best compromise diaphragm thickness for my specific passband?

What coating should I use on the mylar?

Im aware that several manufacturers use double sided tape provided by 3m to act as the spacer and glue. Is this a good alternative to epoxy? Is the bond strong and not decrease substantially over time?

What amplifier should I use? Would an extremely high power Pro-amp work? or should I consider something along the lines of an Adcom?

What should I look for in a high quality transformer? Roger Sanders mentions 8kv is a good start for a midrange ESL.
 
thadman said:
Im going to attempt a DIY ESL build! Ive searched and even bought Roger Sanders book, but still have some specific questions.

Im looking to build an extremely high output 250/300hz-20khz+ (may augment with a line source super tweeter if ESL performance is abyssmal and price permits) ESL. I have the space for ~16" x 7'.


I'm not sure what you mean by extremely high output? I have a set of 18" x 46" (active area) panels and I can debone chickens with them. A super tweeter may be problematic due to the very different dispersion patterns. If you don't segment them, your dispersion will be similar to a laser, then crossed over to something that is way more dispersive. You shouldn't have any problem running your panels up to 20K unless you use very thick diaphragms.

I drive my panels to very loud levels with a 20 watt tube amp. If I step up to a citation II, that 60 watts will make my ears bleed.

Think about it this way, my panels have 4748 cm^2 effective cone area. That's one ******* HUGE woofer, and an insanely large midrange and tweeter.


What is the best compromise diaphragm thickness for my specific passband?
There's a trade-off between tension available, diaphragm thickness, polarizing voltage, and treble rolloff. If you use thin diaphragms for best transient performance, then you may have to use slightly narrower spacers. There's a lot you can do to use thin diaphragms. The 3.8 uM mylar is great, but harder to work with than say 6 uM. I started with 12 uM and that stuff is bulletproof.


What coating should I use on the mylar?
I'd use the coating from ER audio, but there are a whole lot of choices. I use a product that DuPont doesn't make anymore. The ER Audio product is similar.

Im aware that several manufacturers use double sided tape provided by 3m to act as the spacer and glue. Is this a good alternative to epoxy? Is the bond strong and not decrease substantially over time?

I use 3M foam tape (the urethane and acrylic adhesive version). IT works really well and so far has been holding up great for like 4 years now. The problem with it is that you really only get two choices of thicknesses. That's really not a big deal, but it is a limit.

What amplifier should I use? Would an extremely high power Pro-amp work? or should I consider something along the lines of an Adcom?
You need something that performs well into very reactive loads. I like tube amps with my speakers, SET's don't work well, but push-pull generally does. I have a little bryston that works well. the Pass Aleph3 I had didn't work particularly well.


What should I look for in a high quality transformer? Roger Sanders mentions 8kv is a good start for a midrange ESL.

I use the old innersound transformers, but they aren't huge, so if you want ear-bleeding levels you may want to step up to something larger. The Pritron trannies would be a good start.


Take what roger says with a grain of salt. It's a very accessible book, but I don't agree with everything he says. He seems to be obsessed with loudness (which seems to line up well withy our goals). I don't agree with him crossing over to the panels so high. I've tried it on my panels, I it has that same "phasey" sound that some of the Martin Logan speakers have. The lower I cross my panels over the better it sounds. I cross them at 130 Hz.

Sheldon
 
Re: Re: diy esl suggestions thread

stokessd said:
I'm not sure what you mean by extremely high output?

I'd like to match the output of the RS390HF dipole woofer line array (4 RS390HF/tower) that I plan on using for 30-250/300hz, so ~115dB+.

Would it be a good idea to seperate the drivers into two seperate towers? I could build the ESL seperately and then construct a 7' H-Frame for the RS390HFs. How do I calculate the resonance of the h-frame and the effective baffle width (so I can calculate dipole rolloff)? Should I mount the drivers opposite (ie normal/inverted/normal/inverted) to cancel vibrations and lower even order distortions with no audible penalty (ie diffraction issues caused by basket/magnet obstruction)

I could probably cross lower, but that would drastically limit maximum SPL (4x displacement requirements, less surface tension), it would come dangerously close to the resonance of the diaphragm, which I am supposed to avoid (? I am supposed to cross before the resonance or can I cross during the resonance?), and it would put a strain on the transformer (i read that even the best ones can only cover 7 octaves)

The urethane foam which supposedly resists rotting only comes in 45 mil and 30 mil. Would 45 mil be large enough for such a low crossover point and the issue of acoustic coupling? The idea of 4 RS390HFs operating next to each of these is quite worrisome...

Does mylar come in sheets smaller than 3.8 microns? say 2 microns? I have a friend who works at a tooling shop and has access to thousands of catalogs where I can purchase all of these parts. What are specific things I should look for if I was looking for a product superior to mylar yet lighter and more durable (such as specific tensile strength, weight, etc etc).

Is the double sided tape superior to plexi+epoxy?

reactive loads? hmmm... (im not very good with electronics). Can you explain something specific (that may be provided by the manu. if I looked hard enough?) I heard they loved extremely high voltage rails...but arent so concerned with anything else.
 
Re: Re: diy esl suggestions thread

stokessd said:


Take what roger says with a grain of salt. It's a very accessible book, but I don't agree with everything he says. He seems to be obsessed with loudness (which seems to line up well withy our goals). I don't agree with him crossing over to the panels so high. I've tried it on my panels, I it has that same "phasey" sound that some of the Martin Logan speakers have. The lower I cross my panels over the better it sounds. I cross them at 130 Hz.

Sheldon

Hi Sheldon

With 'phasey', do you mean colouration? Becasuse that's what I can hear with some of the ML. The enclosure is not resonance-free and is directly connected with the ESL panel.
There may be a severe trade off with a crossover at a low 130 Hz because you're running the ESL down to a region where phase cancellation eats away bass.

MartinJan
 
What I mean by phasey is a weird midrange sound like the woofer and the panel are both contributing, but are offset in phase too much and there is this muddled portion of the spectrum. Not really a coloration, but a odd funkyness that I can't quite describe.

My panels are 20" wide, so my pressure rolloff starts just around 700 Hz. I compensate for that with a shelving EQ.

What crossing over that low does is limit my max SPL due to the shelving EQ pushing diaphragm excursion up.


Thadman-

You aren't planning to do a passive crossover are you? If you are doing an active crossover, you can use a shelving EQ to fix the pressure rolloff. Otherwise you are going to either segment your panel to fix the pressure feed back 6 dB per octave rolloff, or you'll have to knock it down with a passive XO and that will kill your efficiency. IF you use an active EQ, it really doesn't matter what the efficiency is. that just effects the needed power.


Sheldon
 
Hi,

famous last words: " I want to built an ESL...."
Welcome to the world of sorrow and distress ;-)

Well it´s not that bad, in fact it could be relatively easy, if You follow exact guidelines of working concepts. Surprisingly most guys starting such a project begin to think of tweaking before they already have a decent clue what a ESL is and which results one can reach with it..or not! :rolleyes:

First of all forget about extreme output. With regard to maximum SPL ESLs will not be the prime choice. Still though You can get more than enough high output for home uses with medium-sized panels (think of something of the size of the older ML Sequel). In fact even homecinema-stuff like the ´Terminator-theme´ or maximum dynamics like the CincinnattyPops playing ´RobinHood´ or ´Straussfest´ won´t stress a good panel much and the sonic performance is still far ahead of any dynamic speaker :D
The older MLs have two major probs. A terribly bad audio-tranny and a rather badly integrating bass solution, but they could play quite loud, because the conceptual basics were done right. Amongst those is a quite highish crossover-freq.

Using good trannies and dipoles for the bass can solve the sonic problems of such a concept (as ML shows with its magnificent Statements), or as it is done here in quite a similar way.
An externally hosted image should be here but it was not working when we last tested it.

I´d recommend to study how the Statement is built because here imho everything is done as it should be done to get excellent sonic results as well as high output (ok, You might argue about diaphragm thickness and if it weren´t advantageous to drive this beast completely active). :devily:

What are the major points to look at?
Use a sufficiently large panel--10"x50" (25x125cm) or more even if You want to cross over as low as 250Hz. Not only does this raise the SPL but Distortion will be lower too.
Use as small the d/s distance as possible --above 250Hz 1/25"...1/16" (1.0...1.5mm) is ok.
Use very high mechanical tension of the diaphragm that places the ground resonance roughly one octave below the crossover-freq. High tension minimizes the effect of acoustic coupling with the bass (membrane can be blown into the stator by strong bass waves)
(ML reaches a ground resonance ~ 250Hz with 1/2mil (12µm), I reach 170Hz with 1/8mil (3,5µm). My recommendation is a membrane thickness between 3µm and 6µm. Thinner won´t withstand the high tension and thicker may result in a loss of detail.
Use genuine Mylar (Type S or C) or Hostaphan (RE) for the diaphragm. Those have proven to withstand the high tension over years.
When using sheet metal stators think of bowing them. This will stiffen and stabilize the stators considerably and it looks pleasing because it keeps the panel thickness very small without the need of additional bracing. With wire stators the design will be thicker and You don´t need to bow those. Using electrical segmentation You can influence the distribution character of the panel , as well as bowing broadens the dispersion slightly with sheet metal stators.
Use thin wire or thin sheet metal (~1/25"). Thicker material may restrict the bandwidth too much.
Use sheets with small holes and high openness (i.e. RV3/4) and insulate well (PET-epoxy powder, PA-powders like Rilsan or Corvel or laquer with PU-laquer as usable for staircases, or PVC for wire insulation). If possible try to round the hole edges by sanding or etching. This will reduce the electrical stress (ageing) and the risc of flashovers.

As spacers You can use the soft foam tapes of 3M --Yes the VHB-types are expensive, but they´ll save a lot of time and Your nerves) and I recommend not to use other brands.
An externally hosted image should be here but it was not working when we last tested it.

Some epoxy-glues will work. While they resist a pull very strongly, they might fail under shearing forces, which is our case.
Too I don´t like the idea much to have a diaphragm pulled taut under high tension in a stretching frame for hours till the epoxy is completely hardened. But they may be prime choice with flat wire stator frames where the spacer is an integral part of the frame itself and where only a very thin layer of bonding material is needed. With those kind of frames I got good and stable glueing results alternatively with doublesided sticky tape from TESA for carpets.
The soft foam tapes immideately form a strong bond. There is this one risky moment when You actually place the membrane on the tape, because You have just one try to make it good! (You´ll most probabely need a helping hand here)
Because of the tape´s softness You have to take measures against the strong shearing forces of the membrane. I´ve done this (again have a closer look at ML) by pulling the membrane around the stator and glueing it to the backside of the stator too with a thin doublesided tape. This way the tension is preserved forever.

Searching the forum You´ll get answers about which coating works. Some of them can be bought, some of them can be mixed by yourself, some are expensive and some come nearly free, some are transparent, others not. Have a look and draw Your choice ;-

There is a remarkable difference between panels which are driven completely as one (sheet metal stators) and those that are segmented electrically (wire stators) and that is its capacitance. Capacitance increases with larger panel area and smaller d/s.
Sheet metal stators have a constant capacity over the frequency band (that can be calculated quite exactly from the dimensions) while electrically segmented stators have a varying and smaller capacitance. Since You have to keep the speakers impedance in mind (as specified in the amps manual) the transformation factor U depends on the design of the panel. As a guideline: the higher the capacitance of the panel, the lower the U. While medium to large sheet metal-panels will be happy with Us of ~1:50...1:75, most segmented wire stators can be driven with Us of >1:100.
Increasing the transformation factor rises the output voltage, but it costs bandwidth (and its not good for the sound and dynamics either) and puts more stress on the insulating materials (safety!!).
If You design for low Us You might even use standard offtheshelf toroidal power trannies which give excellent results (better than most ´specialized and expensive trannies btw). I use a pair of 230V/6V types per panel and got measurably and audibly better results than other trannies I tested so far -apart from those wonderful but expensive Plitron/Amplimo.
They won´t have enough inductance to drive a fullrange ESL properly but for hybrids with an elevated crossover point they are totally fine.

jauu
Calvin


damn, just 10.000 sign allowed :bigeyes:
 
Part II

As a partner to a good panel a dipole bass/midbass can be a very fine choice.
The MLs sonic problems result from the inferior matching of panel and bass. Responsible for this are the different steepness of the acoustical filter character and strong differences between the distribution character of panel and bass. Seamless integration can be reached by solving those two probs. The first is a matter of designing the right crossover and the second is a matter of choosing the right working principle for the (mid)bass.
Again have a look at the pic above or the ML Statement. Both concepts work with a line of 6.5" drivers in a dipolar cabinet (U-shape with ML, A-shape with mine). So the dipolar linesource the panel forms is augmented by the dipolar linesource the 8 dynamic drivers form.
When You use a shaped cabinet You get a resonance effect that depends on the dimensions of the cabinet. I doubt that You´ll get enough bandwidth to reach >300Hz in good quality with drivers /cabinets larger than 8". I don´t know the RS390 driver, but the number indicates a 15” driver.
It will be hard if not impossible to reach the desired high crossover freq without running into resonance problems. I wouldn´t run such big drivers far higher than ~100Hz.
In this case I´d rather put the drivers in closed compartments and drive them actively as real Subwoofers below ~80Hz and would add a linesource of smaller 5”-7” in a dipolar cabinet, that fill the range between ~80hz and 300Hz. But heyyyy doesn´t that look similar the Statement again?? :D Did I already say I that I like the Statement as a very remarkable design? :D

Driving the ESL is not easy. The problem with most amplifiers is, that they are not designed to work stable at such complex loads. The impedance an amplifier sees when driving a loudspeaker consists of an mainly resistive (ohmic) part and a reactive part. Only the resistive part is used to create sound (real power) while the reactive part represents power that the amplifier must supply for, but that is simply wasted. This reactive power ´oscillates´ between amp and speaker just putting additional load on the power supply of the amp and generating additional heat. The phase angle (electrical phase measurement of the speaker) gives an idea what to expect. A phase angle of 0° means only real power (pure resistance), a angle of eg 45° means that real and reactive power are of same magnitude. The complete power the amp has to deliver is the vectorsum of both. To deliver lets say 10W real (+10W reactive) the amp has to supply ~15W. Most dynamic speakers stay within a phase-band of +-45°, so a slightly oversized (1.5 times) powersupply and heatsink is still ok. A ESL on the other hand is nearly a pure capacitance, meaning an phase angle of theoretically 90°. In this case there is only reactive power and no real power at all. In praxi (with the help of the tranny) the phase angle is lower than 90°. So there is a part of real power that is useful, but it is relatively small, compared to the reactive power. So the amp has to have very oversized powersupplies and heatsinks to be able to supply reasonable amounts of real power to the ESL and the huge amounts of reactive power. The problem gets worse the better the tranny´s quality is. A good lowloss tranny like the Plitron/Amplimo generates phase angles up to 85° and resistive values of less than 1Ohm with an sheet metal stator, while a rather bad quality EI-Type tranny gives 70° and >1Ohm. So the better tranny is the worse one for the amplifier.
The huge phaseshift generates a second problem for all amplifiers with global feedback. The transient response is spoiled and in many cases the amp may even start to oscillate, thereby heating up and up till some fuse blows or the amp dies.
The ´faster´ the amp is, the greater the problem is. Amps without global feedback like some SEs (wether tube or sand) are usually fine as are generally tube amps.
The upcoming d-amps are probabely the best choice, since they show themselves quite unimpressed with complex loads and can drive even huge panels exceptionally well (especially at elevated SPLs). The costs for a good D-amp are comparably lower than for any other technology. So have a look what is going on there ;)

jauu
Calvin
 
The RS390HF have extremely low inductance (1.0mH if I recall) and a crazy resonance peak right around 1600-1800hz (the peak starts to slope slowly form right around 1.2khz and then things start to get nasty around 1.5khz). The third harmonic of this peak (assuming 1600hz) is 533hz and distortion will start to rise >400hz. I will be crossing nearly an octave below this, so non-linear distortion should be no issue.

Also heres a review of the HF series http://www.mfk-projects.com/rs_12_hi-fi.htm
quoted from the review

Anyway, one amazing thing about this woofer is its ability to perform well up to several hundred Hz. This is a little unusual for this kind of heavy high excursion driver. I guess if you are not too critical you could use this driver to 1Khz but personally I wouldn't use any 12" driver that high except in certain pro-audio applications. I would feel very comfortable however using this driver to 300 Hz. In most of the applications I have planned for it I will not use it above about 140 Hz but that is more because this is what the application calls for rather than any concern with using this driver higher in frequency.

I think this driver will be a first rate performer in both di-pole applications and box applications. It seems about as good as the XLS in the mid bass region with some frequencies possibly better on the XLS and others better with the RS. Generally the two are close in the mid bass region. The RS is better at very low frequency and will also be better than the XLS at frequencies above 100 Hz. The RS is also the quieter of the two making it a much better choice for any dipole application than the XLS.


Linkwitz uses XLS drivers in his orion design, and these drivers are claimed to perform better. Are you confident they could not reach 300hz?

Is there a difference in perceived detail between 3.8 micron and say 6 micron?

Also, what amplifier would you recommend that is <$600? Im perfectly willing to buy used (as long as its in good condition) on ebay or one of the forums.

What specific tape would you recommend (part numbers and a website would be quite helpful)

Where would I buy those transformers? (part numbers/website would also be very helpful)
 
thadman said:
Linkwitz uses XLS drivers in his orion design, and these drivers are claimed to perform better. Are you confident they could not reach 300hz?

Let me tell you an example. I tested following system:

- 2 x XLS-12 in H-dipole bass (HxWxD 70x36x40 cm)
- 8 x ARN 6" midrange element dipole line array, 150x25cm panel
- 2x100xm feet long ribbon tweeter

The ribbon was on the woofer and midrange line array was as close next to others as it can be. There was ~10cm air gab between. I used Behringer DCX-2496 active filter to set sharp crossover filters.

The room was quite big: I listened 2m away from the system. Walls were at least 1m apart from the speaker and I had 3 meter space behind me.

Crossover frequency 1 kHz was pretty good for the tweeter. But even then you could really hear that the sound came from 2 different direction: the tweeter and the midrange tower. And there was "only" ~30 cm between center of elements. Can you squeeze that with ESL? No. So do not use ESL as a tweeter only. You propably cannot place it close enough to any midranges.

Crossover frequency 80Hz was the best I could use between woofer and midrange tower. Above 100Hz midrange and woofer separated too much. Once again, I heard something I cannot explain better than being 2 different and annoying sources. No good. I can use 12" XLS up to 300Hz alone but it just don´t work with other dipole sources !!! I bet this is the case also with 10" woofers. It´s not matter of frequency response of a single element but how far these elements are from each others and what their polar responce is. You propably can never make ESL + dipole woofer as a midrange sound good if you set a crossover frequency above 100Hz.

Maybe if you listen 10 meters away? :)

Just my opinion based on subjective listening tests with dipole elements.
 
Hi,

@ APi
when You can hear so distintively each source, than I assume that there is something seriously wrong with the setup. Maybe some artefacts from filtering or whatsoever. I had never had anybody complaining about that point, when listening to my system and I can´t verify it either. I think that You´re right that 1kHz is too high as crossover freq and that could create probs the closer the istening distance becomes.

@MJ
does Your opinion base on any experience at all with dipole bass??
Sure, the efficiency seems to be low on first glance, but what do You compare??? Let´s have a look at a an example:
The AudioElevation Attac400 was a dipolar sub, measuring app. 70L of volume (which was actually even less than the shipping cartonage the drivers came in!!). It featured 2 15" drivers and a ~100W amp and a passive notch-filter for the upper resonance. No further equing was necessary but could be switched in (subsonic, up to +6dB possible).
It went right down to 20Hz (16Hz with subsonic) and levelled out at 106dB @40Hz. The linearity was outstanding, as several measurements in test magazines proved.
Sonically it was the most precise bass I ever heard. It even outperformed the aktive feedback subs of Backes&Müller.
Because of its outstanding linearity it was one of the very few subs that could be set up by ear in a few minutes. Since of its distribution character it excited the room resonances much less and thus was a solution for critical rooms where nearly every other sub failed.

Now find :radar:an equally compact woofer:magnify:, that is able to play that deep down, still that loud :faint:and with just an 100W amp and comparable sonic quality.:hphones:

phase cancellation:
takes mainly place perpendicular to the frontal axis of the dipole, thereby reducing the influence of the roommode of that room dimension. On axis there´s nearly no loss in efficiency!

need for equalizing:
oh come on, show me an completely unequalized Box!! Each and every passive box is one and You´d probabely a great fool not to use equing in an active box too!

reflection of antiphase sound against backwall/cancellation:
aah yes, I understand ... but what about those reflections from the backwall from a monopolic radiating driver? Are those better in any wayy and don´t they cancel out at certain freqs too? :scratch: :Popworm:

no damping of fundamental resonance:
Well, damping is inversly proportional to the Q-factor. Since the Q-factor of any driver rises when it is built into a cabinet, damping decreases. In an open baffle or dipole cabinet the Q-factor nearly remains on its free-air value, which means that the damping is in fact the highest of all possible cabinet builds!! You usually need way overdampened drivers so that -after they are built into a cabinet- the damping sinks i.e the Qt rises to the neede value!
The dipole on the other hand doesn´t rely on the cabinet to beef up its performance, but You can use drivers with the right damping/Qts-value right from the start. :D Even closed boxes store and release energy, BR adds another resonator. With every resonanting mechanism (energy storage) I add the sound quality becomes worse. I find it totally logic, that the system with the lowest resonator count should be the potentially best.
:cheers:

jauu
Calvin
 
Calvin said:
Hi,


@MJ
It went right down to 20Hz (16Hz with subsonic) and levelled out at 106dB @40Hz. The linearity was outstanding, as several measurements in test magazines proved.

The dipole sub you mention; whatt freq.range does it have to cover?
The problem I see/hear with dipoles is in the 100-250 Hz region, where there is a severe suckout. You can boost bass below , say 200 Hz, but this will boost the fundamental resonance too, so things are getting complicated. If heard several dipoles but im still not convinced of their sonic superiority. Now there are dipoles and ther are dipoles. and I've never heard some really large arrays as you have build, Calvin. So maybe I can be convinced some day. Till then I am continuimg to experiment with transmissionlines which, according to R. Sanders, should be one of the best, non-resonant, system to marry the ESL.
By the way, with my dipoles esls, I still had some nasty room modes, just as my omni-dynamic speakers.

By,
 
Hi,

the sub covered from <20Hz up to ~150Hz (depending on the settings of the woofer-amp.
See the tests
An externally hosted image should be here but it was not working when we last tested it.

another freq-resonse from a different test magazine
An externally hosted image should be here but it was not working when we last tested it.


without the passive notch-filtering there would be an rising response peaking at @250Hz.
An externally hosted image should be here but it was not working when we last tested it.

Very similar curves did I get with the A-shaped dipoles using the 6.5" drivers. The main difference beeing the higher peak-freqency at 350-400Hz and a higher Fs (~35Hz).
You simply don´t have the 100Hz to 300Hz suckout like with an open baffle and You can easily shape the response to Your needs with a simple 2nd order filter or with he help of an notch-filter.

In my case the ESL-panel´s lower cutoff-freq nicely corresponded with the woofers upper cut-off. Since both drivers feature steep slopes below/above this cutoff-point, I got similar and steep acoustical filter orders. ML -and basically everybody else- had always had the prob that their panels acoustical filter curve was much steeper than their woofer´s and that made the sound ´typical´ Hybrid.

This prob also remains when using a TL. So the TL is way away from beeing the optimum partner for an ESL. There are several points in Sanders book he wouldn´t do the same nowadays, and even some minor failures. When he wrote his book, dipoles were simply not in fashion and everybody thought they couldn´t work properly because of the nasty nasty phase cancellation.
The second point is,that Sanders proposed crossover-freqs around 500Hz. You will only get that high in frequency with an openbaffled dipole to which the problem of suckout applies again. Keeping the crossover-freq below ~300Hz You can use other shapes for the dipole cabinet, thereby solving this problem elegantely as long as the ESL panel doesn´t suffer too much from its own suckout-prob (i.e. as long as the equing can be kept small).

jauuu
Calvin
 
Calvin said:
Hi,

There are several points in Sanders book he wouldn´t do the same nowadays, and even some minor failures. When he wrote his book, dipoles were simply not in fashion and everybody thought they couldn´t work properly because of the nasty nasty phase cancellation.

jauuu
Calvin


Hi,

Are these personal assumptions or did you have some conversation with R. Sanders?
 
I'm not sure R. Sanders would do dipole bass even today. His innersound speakers were designed and produced during a time when Linkwitz's Orion speakers showed the practicality of dipole bass.

The cost of doing dipole bass is significantly higher than a TL. and that's a real issue when trying to sell a product that is already a white elephant in the speaker world.

Sheldon
 
Hi,

of course personal "assumptions", if You want to call careful reading and watching and some experience assumption :D
One point for eg. is, that RS obviously changed his mind about insulating the stators. I admit, I rather could have written minor flaws instead of failures. One shouldn´t forget that english is not everybodys native tounge here.

@sheldon
Yes, Your argument is right. Cost is a rather negative point about dipole basses. They need more complex cabinetry and more membrane area and should preferabely be driven actively and thus are more costly. Additionally You still have to ´convince´ people -as can be read in this thread again ;-) It´s much easier to sell the ´well known´ stuff, even if it were inferior in a certain application.
Trying selling a ESL is hard enough, selling a ESL and dipole bass is double hard. :xeye:
But aren´t we talking about DIY-here, where the complexity of a cabinetry is rather a matter of effort and time and not money?

jauu
Calvin
 
After reading my post concerning the RS390HFs and the review attributed to them...can you explain to me why they wouldnt reach 200/300hz? It would save me a LOT of money...$700-800 worth if I could simply use a line array of them to cover the midbass also.

Im not exactly sure why Roger Sanders recommends the TL. Sure it is an excellent way of reproducing the frequencies with high fidelity...but it falls miserably short in mating with the ESL.

First off its going to have lots of floor/ceiling reflections since the ESL will be operating as a line source and the TL will be operating as a point source. Second the horizontal dispersion patterns would be incredibly different. Third a line sources operates at -3dB for every doubling of distance, whereas a point source operates at -6dB for every doubling of distance.
 
Hi,

The dercrease in loudness as a function of distance (doubling) is supposed to be 3 dB versus 6 dB for linesource and pointsource respectively. However this is based on a theoretcal model where there are no boundaries which influences the decrease in intensity. If your speaker hangs under the Eiffel tower, than 6 dB decrease/doubling distance may be a reasonable aproximation. But speakers are set up in small listening rooms where sound bounces against the wall very soon. So you won't get that 6 dB slope, in fact you will have some room gain! So the whole story of 3 dB vs 6 dB slope makes no sense in real world situations. I would like to see some measurements in real-world listening rooms which show the exact difference between linesource-dipole vs pointsource.

Another thing is that an ESL will work as a line source only if the wavelength is smaller than the height dimension. Low bass has such large wavelength compared to the seize of the ESL that it will not be beamed like the high freq. It will behave more like a (large) pointsource than a line source. So the advantage regarding room interaction in the bass region is widely overrrated while the antiphase sound only causes a lot of trouble.
 
I agree with Dijkstra's points but wanted to add:

If a line source reaches from floor to ceiling, and if the floor and ceiling are reflective, then the line source is effectively extended in length upward and downward by the images in the floor and ceiling, ad infinitum, reducing wavelength sensitivity to a great degree. However, the side walls muddy everything up!
 
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