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items: H290C Horn/Waveguide
items: Re: H290C Horn/Waveguide
items: Re: H290C Horn/Waveguide - closest equiv. in 1.5" or 2"?

H290C Horn/Waveguide
type: item
description: Wayne, I can't find H290 in Europe. Is there an alternative without having to change any thing in the crossover. I already have your 4 pi crossover at home and I'm not handy enough to change any thing. Thank you Santos
creator: santos
date: 2012-03-27T08:48:33-00:00

Re: H290C Horn/Waveguide
type: item
description: There is no suitable alternative to the H290, now designated H290C. The horn/waveguide properties are very specific, and it cannot be substituted without a complete redesign/test cycle. The biggest issue is the position of the acoustic center, which is affected both by the acoustic load and the depth of the device. The size and shape of the H290C are precisely set to provide the right beamwidth, loading and acoustic center. The problem many people are facing is that Eminence discontinued the H290 horn. They were getting them from an overseas supplier that has stopped making them. We are now making the H290C horn/waveguide - and in fact, have updated the profile to have an oblate spheroidal flare profile. It is essentially a plastic version of the wood horn we've been making for years, so we could leverage the design work we've already done. Horn/Waveguide dimensions and beamwidth So my suggestion is to purchase the horns from us. There are other suppliers that still have the H290 in stock, but it is rapidly dwindling. Besides, our new H290C is an improved device, one that can be considered an upgrade. It uses the same baffle cutout and mounting holes, so it's an easy bolt-on replacement.
creator: Wayne Parham
date: 2012-03-27T12:55:03-00:00

Re: H290C Horn/Waveguide
type: item
description: Wow! Wayne, that new H290C waveguide looks great! I wish I new about these prior to purchasing the Eminence H290 units. From a layman's standpoint, what are the noticeable audible differences between the H290 and H290C? Cheers! Joel
creator: Maxjr
date: 2012-03-29T18:26:01-00:00

Re: H290C Horn/Waveguide
type: item
description: The original H290 was a pretty good device, so you shouldn't feel like you've been left in the weeds. It's what I've long considered a happy accident, in that it had very good polars and sounded great in spite of the fact that the curve of the profile was not oblate spheroidal. But the throat shape was close, and the extra expansion towards the mouth acted as a hedge against narrowing beamwidth at the bottom end. It could have used a mouth radius, but other than that, it was a pretty darn good horn.
creator: Wayne Parham
date: 2012-03-29T19:22:47-00:00

Re: H290C Horn/Waveguide
type: item
description: Order placed.
creator: skywave-rider
date: 2012-03-29T23:28:44-00:00

Re: H290C Horn/Waveguide
type: item
description: The first couple sample H290C waveguides are ready for me to check. They look good, but they need to be measured (physical dimensions) before we go for the full production run. I may have them verify some measurements at the mold shop before even sending, but from what I can see, they look great. So we're getting close.
creator: Wayne Parham
date: 2012-05-17T00:19:03-00:00

Re: H290C Horn/Waveguide
type: item
description: Wayne, Will these be a bolt in replacement for those of us who have already built our 4Pi cabinets? I already love my 4Pi's so much (thank you, again, for a superb design!) but have an awful habit of always upgrading (cars, speakers, etc.) It must be the perfectionist in me. I'd like to sell my original H290 cheap and replace them with these. Also, do you know approx when you'll receive the production units that will be ready for consumer purchase? Thanks! Cheers, Joel
creator: Maxjr
date: 2012-05-17T21:37:32-00:00

Re: H290C Horn/Waveguide
type: item
description: Yes, the H290 horns in existing designs can be retrofitted with H290C waveguides. It was designed specifically to be a bolt-on upgrade. The old H290 was really pretty good, acting much the same as a waveguide providing nearly constant horizontal directivity and low diffraction. The most important feature I had to maintain was the position of the acoustic center, and the new H290C has the exact same acoustic center in the crossover region. I expect to have inventory in six to eight weeks or so. We already have taken several preorders, and in fact, I may have to up the initial order quantity. No problem though, the molds are good for at least a million units.
creator: Wayne Parham
date: 2012-05-17T22:05:07-00:00

Re: H290C Horn/Waveguide
type: item
description: More photos (click on photo for a close-up):
creator: Wayne Parham
date: 2012-05-18T03:52:32-00:00

Re: H290C Horn/Waveguide
type: item
description: They look great, Wayne. Take your time.
creator: skywave-rider
date: 2012-05-25T19:50:58-00:00

Re: H290C Horn/Waveguide
type: item
description: Measurements all measurements taken using DE250 driver mounted on infinite baffle, i.e. half-space drive signal 8.4v microphone distance 3M Impedance The impedance graph shows first 1/4λ mode is around 800Hz, and 1/2λ about 1.6kHz. You can also see it in the response curve below. All horns like this (conical, quadratic, oblate spheroidal) have a peak at the 1/4λ mode. The dimensions of the H290C place that peak just below the passband, which I find an attractive configuration. Its pure oblate spheroidal flare profile sets its length and mouth size based on its tangential wall angle and throat size. These are fixed dimenisions, set by its geometry, as discussed earlier in this thread. A conical or OS flare has to be at least as long as half its width to achieve the right mouth size to support a 90° pattern. You can't create a right triangle with any other dimensions. On-axis response Devices like this have a peak at cutoff, followed by reduced output through the first octave. That's because they don't really provide good acoustic loading down low. They start becoming most efficient around 1/2λ and above. That's why the π crossover provides a method for setting specific damping in the crossover region, as well as for setting the top-octave compensation for mass-rolloff. The values chosen for the π pad set the bottom-octave level (by virtue of crossover filter Q) and top-octave level (by virtue of attenuator bypass capacitor and/or shunt resistor and the rising impedance of the voice coil). So this very versatile crossover configuration is perfect for waveguides. Horizontal Response Curves, every 10° through a 180° arc Horizontal off-axis response is excellent, very uniform through the coverage pattern, and well-behaved outside the pattern too. Horizontal Contour Chart (Directivity Sonogram) Viewing the horizontal beamwidth using a sonogram, you can see that energy distribution is very uniform. However, you may also notice that at low frequencies, the beamwidth doesn't…
creator: Wayne Parham
date: 2012-07-12T13:08:35-00:00

Re: H290C Horn/Waveguide
type: item
description: Tour de force.
creator: skywave-rider
date: 2012-07-12T15:30:52-00:00

Re: H290C Horn/Waveguide
type: item
description: Wow!
creator: zheka
date: 2012-07-28T00:58:07-00:00

Re: H290C Horn/Waveguide
type: item
description: Thanks for the thumbs up, guys. I'm really proud of it. As many of you know, but some probably don't, this H290C horn is a molded plastic implementation of a horn I developed about ten years ago. It's the horn shape I always wanted. For many years, I've used horns that were close, mostly because they were available and gave me 95% of what I wanted. But this is exactly the right shape, without compromise. My first go at a no-compromise horn/waveguide was what I now call the H390C. I made it out of wood, and it is as much aesthetically beautiful as it is acoustically correct. The thing is, since it is designed to be cradle mounted, it doesn't have the benefit of the baffle, and therefore had to be made a little larger. This H290C is the exact same shape as the H390C from throat to about 70% the length of the horn - It has the OSEC (oblate spheroidal / elliptic cylindrical) flare profile in both horizontal and vertical planes, and also in the transition at the edges between them. This shape allows the wavefront to transition perfectly from the plane wave generated by the compression driver into a section of a sphere at the mouth. This transition from plane wave to spherical wave is one of the most important functions of a horn/waveguide. The biggest difference between the H290C and the H390C (besides material) is the radius to the mouth. The H290C doesn't need as much of a radius, particularly in the vertical. The baffle provides some assistance here, reducing the size requirements. That is a welcome feature, since reduced vertical size allows center-to-center spacing between sound sources to be made smaller, increasing the size of the forward lobe. That has always been important to me. This horn has been a long time coming. It really is the latest evolution of three decades of work. There are other waveguides out there, some from relative new comers, others from experts in the field. But none of them are as good as this waveguide, in my opinion. This one is the exact …
creator: Wayne Parham
date: 2012-07-28T17:13:55-00:00

Re: H290C Horn/Waveguide
type: item
description: Thank you. By the way, I personally like knowing the background and historical perspective, the maturity from long evolution of your designs. There's a lot more here than just a waveguide. Perhaps one day you can find a good place to write it. Thanks again for taking time respond. Cheers!
creator: zheka
date: 2012-07-29T13:32:41-00:00

Re: H290C Horn/Waveguide
type: item
description: Thanks for your kind words. If you're interested, some of the history is described in the following links: High-Fidelity Uniform-Directivity Loudspeakers Pi horn design philosophies Corner pi speakers π Cornerhorns - a brief history Klipschorn vs seven π cornerhorn My personal opinions of various design philosophies As for the development of the H290C in particular, I had initially been attracted to the quadratic throat waveguide, as it resembled radial horns which I had empirically found to provide the best performance. Then later, after discussing oblate spheroidal waveguide/horns with Earl Geddes, and then upon finding the documents below about Gaussian wave propogation, as well as many other texts on similarly related topics, I was convinced this flare profile made sense. Landesman dissertation about wave propogation based on the Oblate Spheroidal coordinate system Landesman Paper about the OS coordinate system An explanation of the paraxial approximation, which is relevant to this discussion Conoidal surfaces are defined by lines drawn tangent to an oblate shperoid. The resulting curve is a hyperboloid of one sheet whose asymptotes pass through the origin (x/y axis) inclined at an angle cos-1 with the z axis. You will notice on page 73 of the first paper above, equation 4.2 is the formula used to plot this flare profile, the one commonly referred to as describing an oblate spheroidal (and/or elliptic cylindrical) waveguide/horn. It forms a hyperbola created from a line drawn tangent to an oblate spheroid or elliptic cylinder. The two are the same profile, but the OS is round while the EC is rectangular. The two can be joined easily, since they are based on the same family of elliptic coordinate systems, allowing for a smooth transition between round throat and rectangular mouth of whatever aspect ratio is desired. I have also used a polynomial expression to plot this flare profile, one that tracks the trigometric function precisely, but it is a more complex for…
creator: Wayne Parham
date: 2012-07-29T15:40:04-00:00

Re: H290C Horn/Waveguide
type: item
description: These look really nice.. I have the Eminence H290 with the B&C DE250. Those DE250s are heavy! I like how the Eminence horns have the bolted plate you mount the compression driver on that reinforces the plate to the horn. The plate you bolt the driver to... Do you worry about that plate breaking free from the horn?
creator: mantha3
date: 2012-07-31T16:17:11-00:00

Re: H290C Horn/Waveguide
type: item
description: That is an important joint, certainly. Ours is extra thick there, and is a one-piece design. The mold was more expensive, but it makes the horn seamless, being a one-piece part.
creator: Wayne Parham
date: 2012-07-31T18:17:47-00:00

Re: H290C Horn/Waveguide
type: item
description: I have the Eminence horns... I have not started the build. I can't return the horns I have... Tempting to buy yours anyway. Shoot!
creator: mantha3
date: 2012-07-31T19:28:04-00:00

Re: H290C Horn/Waveguide
type: item
description: I have to say, it looks sharp. That's not really important, but nice. Wayne Parham wrote on Tue, 31 July 2012 13:17 That is an important joint, certainly. Ours is extra thick there, and is a one-piece design. The mold was more expensive, but it makes the horn seamless, being a one-piece part.
creator: skywave-rider
date: 2012-07-31T20:10:36-00:00

Re: H290C Horn/Waveguide
type: item
description: mantha3 wrote on Tue, 31 July 2012 14:28 I have the Eminence horns... I have not started the build. I can't return the horns I have... Tempting to buy yours anyway. Shoot! I was able to sell mine on the parts express forum. Give it a shot, maybe you'll get lucky. In other news, my new H290C horns are on their way
creator: blvdre
date: 2012-07-31T20:35:11-00:00

Re: H290C Horn/Waveguide
type: item
description: Some have asked why it is important to maintain 90° beamwidth in the horizontal, and why 100° or more is less desirable. For example, one of our friends here recently evaluated another similar waveguide/horn with ~100° coverage. The other horn was touted as a 90° waveguide, but all measurements pointed to it having at least 100° beamwidth in the horizontal. It became somewhat of a point of contention, with the other horn/waveguide proponents reverting to an argument of "how much does it matter anyway?" So what is the difference between 90° beamwidth and a little more, say 100° or 110°? What's wrong with a slightly wider pattern in the horizontal? How much does it really matter? If the speaker were outdoors or in a very wide open space, I would find nothing wrong with the wider pattern. With no boundaries to worry about, I almost don't care what the coverage pattern is. But indoors, in a home hifi environment, the whole point of controlled directivity is to reduce early reflections from the nearest walls. I mean, why bother with having a waveguide/horn at all if your coverage pattern allows a significant amount of energy to be reflected off the side walls? The sound radiated by a horn/waveguide doesn't end abruptly at the beamwidth "edge". Beamwidth is defined as the angle between the directions on either side of the forward axis, at which the intensity of the sound pressure level drops to one-half the value it has on the forward axis. That's only -6dB down, so sound definitely radiates outside this coverage pattern. The goals are to provide uniform coverage within the desired beamwidth and to limit radiation outside this angle, to reduce unwanted reflections. So if I were to have to choose between being a "smidge" inside or outside the goal, I'd definitely lean towards being slightly tighter than wider. I'd rather have constant directivity through an 80° horizontal arc than 100° beamwidth for this application. One shouldn't go too far with this, because too-narrow b…
creator: Wayne Parham
date: 2012-08-09T15:38:12-00:00

Re: H290C Horn/Waveguide
type: item
description: Wayne, I'd like to purchase a pair of these bolt on upgrades and replace the current Eminence H290 horns I have in my fully upgraded 4Pis. I have two questions regarding the new H290C: 1) Are there any changes needed to be done on my current crossovers? I can modify them, no problem. I'm just curious. 2) What audible differences could be expected when I compare the H290 to the H290C head-to-head with everything else remaining the same (JBL driver, crossovers, DE250, speaker enclosure, listening environment, and music) Thanks for your time and all your efforts!
creator: Maxjr
date: 2012-08-16T12:42:37-00:00

Re: H290C Horn/Waveguide
type: item
description: The H290C was designed from the start to be a bolt-on upgrade, that would require a minimum of crossover changes. The acoustic centers are in the same place and the patterns are similar, so the pre-2012 crossover used with the old H290 horn can be used and the primary lobe is forward and centered. But the upgraded H290C waveguide benefits from an upgraded crossover that has different values in a couple locations. Its impedance curve is different, necessitating the removal of capacitor C1 and installation of 16Ω resistor Rs. Check the schematic and board layout to identify and locate these components. The π crossover uses a specialized π pad for its attenuator and top-octave compensation. It provides three functions, 1. To provide full-band attenuation, 2. To provide mass-rolloff compensation in the top-octave and 3. To provide specific damping for the core-splitter, which sets the SPL level of the crossover region independently of the midband. This network provides maximum flexibility, allowing the low, medium and high frequency ranges of the tweeter's transfer function to be set independently. This network is created by components R1/R2 and the compression driver itself. In many cases, the output shunt leg of the π network is provided solely by the compression driver, and no extra shunt is required. But in the case of the H290C, a shunt resistor Rs is used. The input leg R2 sets the load on the core splitter, which sets the damping. High levels of damping (low resistor values) brings down the SPL in the crossover region. Low levels of damping (high resistor values) increase SPL in the crossover region. The attenuator R1 sets the midband SPL level, and interacts with the output leg, providing mass-rolloff compensation. Optional components C1 and Rs are used to further tailor the response. As for audible differences, remember that I always found the old H290 horn to a pretty good part, and didn't change it even when several new waveguide products began to enter the m…
creator: Wayne Parham
date: 2012-08-16T15:12:31-00:00

Re: H290C Horn/Waveguide
type: item
description: Thank you so much for that thorough response. I look forward to trying out the new H290C horns.
creator: Maxjr
date: 2012-08-16T19:11:46-00:00

Re: H290C Horn/Waveguide
type: item
description: Hi All, I got the horns in and they are huge improvement over the H295s I had in there already (got them as the original 290s were out of stock and delayed back order). Well worth the effort to put them in.
creator: gofar99
date: 2012-08-18T19:35:20-00:00

Re: H290C Horn/Waveguide
type: item
description: I just ordered my pair! I can't wait to try them out
creator: Maxjr
date: 2012-08-23T03:48:01-00:00

Re: H290C Horn/Waveguide
type: item
description: Wayne, I'm considering upgrading to the H290Cs on my 4 pis. This thread has me hooked! By the way, I've been loving my 4 pis and 3 pi subwoofers. I don't think anyone's left my apartment unimpressed. However, now I have a bit of upgrade-itis plus I'm considering a build for my dad, so I might try to knock both out in one purchase. Also not to threadjack too badly, but I'd like to get your thoughts on the best speakers for my dad. He has an entertainment center in a corner that is closely flanked by his speakers. Based on this limited arrangement (and no room for flanking subs), I'm thinking 2 pi towers might be the way to go. What do you think?
creator: Quiet_Storm
date: 2012-08-27T04:28:06-00:00

Re: H290C Horn/Waveguide
type: item
description: Quiet_Storm wrote on Sun, 26 August 2012 23:28 Wayne, I'm considering upgrading to the H290Cs on my 4 pis. This thread has me hooked! By the way, I've been loving my 4 pis and 3 pi subwoofers. I don't think anyone's left my apartment unimpressed. However, now I have a bit of upgrade-itis plus I'm considering a build for my dad, so I might try to knock both out in one purchase. Also not to threadjack too badly, but I'd like to get your thoughts on the best speakers for my dad. He has an entertainment center in a corner that is closely flanked by his speakers. Based on this limited arrangement (and no room for flanking subs), I'm thinking 2 pi towers might be the way to go. What do you think? I like two π towers, and use them for my bedroom system. It is setup kind of like you described.
creator: Wayne Parham
date: 2012-08-27T13:10:07-00:00

Re: H290C Horn/Waveguide
type: item
description: Wayne, looks like the H290C waveguides will be here Monday, though UPS says they are in NY right now! Until I get my woofers for the eventual 3Pi, I intend to set up the H290Cs in my home rig. The home rig uses the 4Pi crossover/DE250/JBL 123A-1. I have added 20dB attenuation from your chart plus an LPad for more attenuation and adjust-ability. Currently running QSC waveguides.
creator: skywave-rider
date: 2012-09-08T18:48:47-00:00

Re: H290C Horn/Waveguide
type: item
description: FYI, got the H290Cs yesterday and immediately installed them in my home rig. This is a temp setup, as I eventually intend to do a 3Pi build. But, even in my non optimized rig, I can tell you the H290C sounds superb. In comparison to the QSC HPR 152i, which I think is excellent and have been using for several years, I hear less "distortion." That may relate to modes in the WG, not sure. The feeling is that the H290C is cleaner. [The "rig" is: JBL 123A-1/DE250/H290C/4Pi crossover with 20dB attenuation as per Wayne's chart and C1 removed. Running with horn on top, not in baffle, temporarily.]
creator: skywave-rider
date: 2012-09-11T14:24:51-00:00

Re: H290C Horn/Waveguide
type: item
description: Glad your new waveguides sound good to you. Interestingly, your impressions are the same as mine. I've measured the H290C and I've listened to it, and my listening impression seems subjectively more of an improvement than the measurements show. The H290C waveguide just really sounds natural to me. Other people have said the same thing too. There's been enough time now for people to install their new waveguides and listen to them. The feedback I'm getting is very positive. I'm hearing a lot of similar opinions, using phrases like "smoother", "less distorted", "more natural" and "cleaner sounding". The measurements are good, but the old H290 measured surprisingly good too, better than most waveguides out there. So by response measurements, you might not expect much difference between the Eminence H290 and the new Pi H290C, maybe not even enough to hear. While the H290C's oblate spheroidal / elliptic cylinder flare profile is the best shape, in my opinion, other profiles can be nearly as good provided they are close enough. But the H290C is better sounding, probably because it stays true to the OS/EC flare profile. Comparison of measurements don't really show this improvement as much as one might expect. Of course, the measurements I'm talking about are just response and polar measurements, and they will only show very strong internal reflections in the form of response spikes. Smaller reflections won't show up in a response chart, and it may be that this is the difference. It would make sense, given the OSEC waveguide/horn generates the least (HOM) high-order modes. So I think the difference, while subtle, is audible. I'm also pleased to hear your comparison of the Pi H290C with the QSC waveguide. I've received emails from a few others that compared it with the JBL and SEOS waveguides as well. I'm getting unanimous feedback that the H290C sounds better. This, again, I attribute to the pure OSEC flare. Other manufacturers deviate from it for one reason or another. The …
creator: Wayne Parham
date: 2012-09-13T14:37:38-00:00

Re: H290C Horn/Waveguide
type: item
description: Here's a link to a thread that discusses physical dimensions of the H290C horn/waveguide: H290C dimensions It's handy for those that want to route a groove in their baffles for flush mounting.
creator: Wayne Parham
date: 2012-11-29T16:54:44-00:00

Re: H290C Horn/Waveguide
type: item
description: Here's a snapshot of a four π loudspeaker with H290C waveguide: four π loudspeaker
creator: Wayne Parham
date: 2013-01-30T03:04:45-00:00

Re: H290C Horn/Waveguide
type: item
description: Hi Wayne, I'm new here (you may have seen me on diyaudio) and by way of searching many links of a chain, I found your H290C. I haven't seen this question asked or answered yet, so I'll ask here. This is more a H290C question than a Pi Speakers system-question. I'm working on building a 2-way PA top with 12" woofer (probably the Beta 12A-II) and a 1" compression driver (Radian 475PB-16). Is there any reason(s) your H290C wouldn't work well for PA applications? My next step is to discover how to implement alignment in the 2-way passive crossover system, as the CD horn will be directly in front of the woofer several inches. I have downloaded your crossover primer - might I find my answer there? Best regards, Justin
creator: crescendo
date: 2013-03-20T23:45:06-00:00

Re: H290C Horn/Waveguide
type: item
description: The H290C is the best 90°x45° horn/waveguide available, truly a no-compromise design. So naturally, I would suggest it for any DI-matched two-way speaker or constant directivity cornerhorn. The loudspeaker models I make using that waveguide are the ones I found to be the best out of a few dozen that once made up my line, so I find them to represent the best of the best. I wouldn't make any other design choices than those. That said, there are plenty of other similar components that work very well. An example is the Eminence Kappa line of drivers, which are very similar to the ones I use in some of my models, and which have been used by many DIYers on this forum. There are lots of others too, lots of ways to "do it right" but of course lots of ways to do it wrong too. So my suggestion is to study the links in the Pi Speakers FAQ, especially those in the "Crossovers" and "Simulations and Measurements" sections. Also look at the "General Information" section, especially the post called "Notes for the DIYer". It has links to some of the most useful notes for designing speakers like these. For example, "Crossover optimization for DI-matched two-way speakers" describes my exact crossover design process including a video showing how to measure the forward lobe by finding the vertical nulls that mark its edges.
creator: Wayne Parham
date: 2013-03-21T02:26:47-00:00

Re: H290C Horn/Waveguide
type: item
description: "But the upgraded H290C waveguide benefits from an upgraded crossover that has different values in a couple locations. Its impedance curve is different, necessitating the removal of capacitor C1 and installation of 16Ω resistor Rs. Check the schematic and board layout to identify and locate these components." I slept through, as I have been doing since high school , the technical details of the H290C and installed them without changes to the boards. Even before the crossover change I could hear an expanded soundstage in general and clearer exposition of the minor themes of a musical score. When I woke up and corresponded with Wayne I added the Rs resistor that softened the mids. Further discussion revealed that I also had to snip C1. Once done, and liberally covered with rope caulk, the H290C are better-sounding than the Eminence: tonally more neutral with a clearer presentation of nuances like Violas under Cellos and brushes on Cymbals Speaking of Violas: What's the definition of a minor second? Two violists playing in unison. What's the definiton of "perfect pitch?" Throwing a viola into a dumpster without hitting the rim. Why do violists stand for long periods outside people's houses? They can't find the key and they don't know when to come in.
creator: Bill Epstein
date: 2013-03-21T13:46:19-00:00

Re: H290C Horn/Waveguide
type: item
description: May I ask the exact crossover changes required for both the 3Pi and 6Pi speakers? Also, it is difficult to judge the reflectivity of the H290C from the photgraphs on the website. Would you characterize it as flat, satin or glossy? Both of these factors would significantly effect the decision to replace the current Eminence waveguides or not.
creator: rkeman
date: 2013-03-21T19:20:48-00:00

Re: H290C Horn/Waveguide
type: item
description: The crossover change is simple: Remove capacitor C1 and add a 16Ω resistor Rs across the compresion driver. Alternately, there is a position on the board for this resistor so you can install it there if you want instead of hanging it across the driver terminals. The Rs position on the board is right beside C1. Here are some additional comments by Bill Epstein, followed by waveguide design philosophy information: An amazing listening session with the H290C The finish of production waveguides is satin. There are actually samples of many different ABS blends shown earlier in this thread, and that's why it's hard to tell what the finish is. There was a glossy blend I tried early on, and another blend that was a little less glossy but still shinier than what we eventually settled on. The final ABS blend I chose creates a black satin finish. An example is shown in the photo below, a picture of a four π loudspeaker with H290C waveguide: four π loudspeaker As an aside, I chose the ABS mixture largely for its dimensional stability and consistency. The mold shop gave me samples of waveguides using several different mixtures to evaluate, some that were really shiny, some that were more dull. Some held dimensions well, others less so. I placed a priority on dimensional stability, and the ABS blend that is most consistent tends to be less shiny, more of a satin finish. ABS plastic is a mix of three substances, styrene, acrylonitrile and butadiene. The proportions can vary from 15% to 35% acrylonitrile, 5% to 30% butadiene and 40% to 60% styrene. By varying the mixture, you can achieve different properties. Higher styrene tends to make a shinier finish, but we found a little bit less tends to make the device more dimensionally stable, more uniform through the hold and cooldown cycles of the molding process. Since we prioritize dimensional consistency over finish, that sets the material to one with a surface that I would characterize as being satin black. If you want a different f…
creator: Wayne Parham
date: 2013-03-21T20:28:22-00:00

Re: H290C Horn/Waveguide
type: item
description: Hi Wayne, I just recently noticed that H290C directivity sonograms are plotted over linear frequency scale. Do you have versions of the same plots but with logarithmic scale? thank you
creator: zheka
date: 2013-04-23T14:59:08-00:00

Re: H290C Horn/Waveguide
type: item
description: zheka wrote on Tue, 23 April 2013 09:59 I just recently noticed that H290C directivity sonograms are plotted over linear frequency scale. Do you have versions of the same plots but with logarithmic scale? I don't, Жека, sorry. But I'll try and get some for you, as time permits. I was really more focused on the directivity midband up, because down in the crossover region, the midwoofer and tweeter patterns blend anyway. In the crossover overlap band, tweeter directivity is shadowed by the midwoofer. That's also why I didn't consider a secondary flare to combat waistbanding. I wanted the flare to be purely OSEC, to make the wavefront propogation stay perpendicular to the walls as much as possible.
creator: Wayne Parham
date: 2013-04-23T15:28:38-00:00

Re: H290C Horn/Waveguide
type: item
description: Wayne Parham wrote on Tue, 23 April 2013 10:28 I don't, Жека, sorry. But I'll try and get some for you, as time permits. I was really more focused on the directivity midband up, because down in the crossover region, the midwoofer and tweeter patterns blend anyway. In the crossover overlap band, tweeter directivity is shadowed by the midwoofer. That's also why I didn't consider a secondary flare to combat waistbanding. I wanted the flare to be purely OSEC, to make the wavefront propogation stay perpendicular to the walls as much as possible. I am not sure I can tell from the sonograms where the waistbanding takes place. The normalized ones seem perfectly uniform all the way down to 1K. is that because of the scale?
creator: zheka
date: 2013-04-23T16:03:44-00:00

Re: H290C Horn/Waveguide
type: item
description: Yes, it really is. More so the algorithm that creates the stratified sonogram, I think. It appears to try and fit each curve into 6dB slots. In that case, I think the individual curves probably jump from 5dB to 7dB, so the 6dB bin isn't filled until the curves that reach 7dB, something like that. Because you can see the waistbanding in the bottom octave in the 12dB strata, but not so much in the 6dB strata on that sonogram. You can see it a little better on the unstratified charts and also on the chart that isn't normalized. But as I said, it's not something I am really concerned about, since the midwoofer and waveguide patterns blend in that region.
creator: Wayne Parham
date: 2013-04-23T16:15:44-00:00

Re: H290C Horn/Waveguide
type: item
description: got it, thank you.
creator: zheka
date: 2013-04-23T16:20:15-00:00

Re: H290C Horn/Waveguide
type: item
description: In the chart above, you can only really see evidence of waistbanding in the 12dB strata. As I said, I think this is largely caused by the renderer, which seems to fill the strata with any values less than the stratification level without any interpolation or curve fiting. The waistbanding level is less than 6dB lower than midband, so it just doesn't show up. Also, the scale is logarithmic which reduces the size of the waistbanding region, making it more difficult to see. To help better illustrate waistbanding in the H290C, we can change the scale of the sonogram to logarithmic. That stretches the area where waistbanding occurs. See the charts below: H290C horizontal sonogram using logarithmic scale H290C vertical sonogram using logarithmic scale These are sonograms made for the H290C using a different renderer and plotted on a logarithmic scale. The measurements were made in a different environment too, so there are slight differences in the data but it shows general agreement with the other measurements. The biggest difference is in the rendering and the logarithmic scale, where here we can sort of put the waistbanding region under a magnifying glass. See the color scale at the right side of each chart. This legend shows us a color gradient mapped to SPL. You will notice that horizontal waistbanding centers around 1.8kHz, and its effects are about 2dB reduction of sound at 45° compared to the midband levels. That's what waistbanding does. It reduces output slightly at the edge of the beam. As a sanity check, we can calculate waveguide beamwidth using formulas from Keele's paper, "What's so Sacred About Exponential Horns?" Pattern Control Lower Limit = (106 / Mouth Width * Wall Angle) Waistbanding Frequency = 1.5 * Pattern Control Lower Limit Waistbanding Pinch Angle = 2 * Pattern Control Lower Limit / 3 Therefore, the H290C has properties somewhere in this range: 106 / 11" * 85° = 1070Hz (lower limit of pattern control) 1070 * 1.5 = 1.6kHz (waistbanding center freq…
creator: Wayne Parham
date: 2013-04-30T18:15:00-00:00

Re: H290C Horn/Waveguide
type: item
description: More information in the thread below, including implementation considerations and comparisons with other designs: Uniform Directivity - How important is it?
creator: Wayne Parham
date: 2013-06-12T15:45:31-00:00

Re: H290C Horn/Waveguide
type: item
description: There were several influences that drove my decision to create this horn. The most important one was an observation that radial horns having relatively constant horizontal directivity sounded best to me. Objectively, they had smooth response and uniform horizontal directivity. Their physical features were much like modern waveguides, having no sharp edges in the flare. The H290C is very much like a radial horn of similar size, except that its OSEC flare profile is defined as the hyperbola created from a line drawn tangent to an elliptic cylinder or oblate spheroid: When I first heard about this flare profile, I began to study it and found this shape was used in other disciplines as an antenna, horn, lense or other waveform radiator. This is an important "litmus test" for me, because the most successful ideas tend to be used in all engineering fields. Where I see things in just one field (and especially in audio), I am skeptical. Audio is saturated with fads and misguided pseudo-science, some even coming from big names in the industry. But this isn't one of them, and devices created using this profile provide fairly clear advantages. However, the advantages are only found if (and this is a big "if") the waveguide/horn is properly built. Just having this basic shape isn't enough. Just like you can make a good exponential horn or a bad one, or even more so a good conical horn or a bad one, this flare profile has a few "sweet spots" and a bunch that aren't so hot. One is well advised to model the horn, optimizing it for best response and beamwidth/coverage. It isn't a "given" that this particular profile can be used no matter what exit angle is desired. Some work well, but some, not so much. That was the basis for the last post, just above. It gives a feel for a well designed horn, and one that isn't optimized as well. Both have the same coverage pattern, but one has significantly more ripple. More information: The Sound Field and Radiation Impedance of a Hyperbolic Hor…
creator: Wayne Parham
date: 2013-12-03T22:32:04-00:00

Re: H290C Horn/Waveguide - closest equiv. in 1.5" or 2"?
type: item
description: It has been almost seven years since Wayne posted this amazing analysis and explication of waveguide optimization for room use, and a compelling case for the H290C. I bought my pair and I'm convinced. For a different system though I want to use a larger compression driver, with 1.5" or 2" exit. Wayne, are you aware of a large format waveguide that is consistent with the design principles in the H290C? There are a lot of constant directivity 90x40 waveguides out there and I'm pretty lost.
creator: tubino
date: 2020-09-17T19:41:39-00:00

Re: H290C Horn/Waveguide - closest equiv. in 1.5" or 2"?
type: item
description: I put all of my focus on the H290C, and it's predecessor, the H390C. That was a wood horn/waveguide with the same profile but with much more mouth radius because it was designed to be free-standing and therefore have no baffle loading. But both are for 1" exit compression drivers. I was able to do most of the acoustic development work back when I was making the H390C because it was cut on a CNC machine. So I was able to cut a physical model, test it and make incremental improvements. Sometimes, lessons learned with one size driver don't transfer to another. But I find this more true of cone drivers than of compression drivers. So some of what I learned while optimizing the 1" drivers might transfer to larger drivers. Here are a few main points: 1. The basic flare starts with an oblate spheroidal profile and then transitions to a flare based on elliptic cylindrical geometry. Said more simply, the throat is round and the mouth is rectangular. The same OS expansion equation is used to plot each axis, but the asymptotic angle is different in order to get the 90° x 40° shape. A similar profile can be created with a OS to PS transition. That's oblate spheroidal to prolate spheroidal. It makes a very similar horn/waveguide but the mouth is oval-shaped instead of rectangular. Each of these three coordinate systems are related: OS, PS and EC. They all make very similar flare profiles, just with different shaped mouths. Oblate spheroidal horn/waveguides are round, prolate spheroids are oval and elliptic cylinders are rectangular. 2. I find that acoustic loading is important. Waveguides are closely related to conical horns, which don't load well at low frequencies. But they still provide some acoustic loading and I think this is important to sound quality. So do not discount the quality of acoustic loading. 3. Radiusing the mouth edge, gradually opening up wider than the OS/EC profile, helps reduce waistbanding at the lower frequency range. With the right amount of radius area…
creator: Wayne Parham
date: 2020-09-18T04:09:24-00:00

Re: H290C Horn/Waveguide - closest equiv. in 1.5" or 2"?
type: item
description: Thanks, Wayne. That will take me a while to digest, but it confirms my suspicion that the common PA options are limited in several ways... BTW, so you have any of the wood 390C available to sell?
creator: tubino
date: 2020-09-18T11:40:23-00:00

Re: H290C Horn/Waveguide
type: item
description: tubino wrote on Fri, 18 September 2020 06:40 BTW, so you have any of the wood 390C available to sell? Sorry, no. The H390C was very expensive and we stopped stocking them after we had the H290C mold made.
creator: Wayne Parham
date: 2020-09-18T13:38:47-00:00