Chris A
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Posts posted by Chris A
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On 5/3/2021 at 7:51 PM, gnarly said:
I guess i don't see the SH-50 as a larger Synergy, as the entire frontal box size is 28"x28".
That's because is only has 50 degrees of coverage horizontally (or vertically). You need two stacked together side-by-side to have the same coverage as a K-402-MEH. But there seems to be some folks that have such small (or terrible acoustics) listening rooms, that they prefer that extremely narrow coverage.
As a matter of course, Klipsch designs horns have 90-degree horizontal coverage horns--basically all of them. There is a reason for this. I should add that the default coverage requirement (above) is 90 x 60 degrees. If you decide you need narrower coverage--that's certainly up to you, but my experiences are that it doesn't have "apparent source width" (ASW) that fills the front of the room, and without loss of directivity control.
On 5/3/2021 at 7:51 PM, gnarly said:And I know it doesn't take a big Synergy/MEH to reach below 100Hz, other than for how loud do we want.
It does if you want to call it horn-loaded, i.e., that it has directivity down to at least 200 Hz (or below the transition frequency of the room). Otherwise, it's a "hybrid horn--direct radiator" arrangement of drivers that gives the impression of a point source, but in reality is illuminating everything in the near field below the point of loss of directivity control. You can call it an "MEH", but at some point, it's just another direct radiator loudspeaker with a horn-loaded top end.
On 5/3/2021 at 7:51 PM, gnarly said:Can't say i've ever seen anyone build a MEH that didn't get to down to at least 300Hz...in fact i'd say it's almost impossible not to.
With directivity control? They're not really "horns"...but more like a D'Appolito arrangement of drivers below the point of loss of horizontal directivity control (after loss of directivity in the vertical axis). Some folks might be satisfied with that. I wouldn't call it a "horn", however.
On 5/3/2021 at 7:51 PM, gnarly said:I totally get and agree with what you're saying about the mids being the added power handling to the CD, but i'm not sure what you mean by the mids being a phase link.
This: http://www.tonmeister.ca/wordpress/2015/10/29/bo-tech-uni-phase-loudspeakers/
On 5/3/2021 at 7:51 PM, gnarly said:I think too much has been made of the Danley passive xovers...they seem pretty normal to me, especially when you look at the SH-50's phase trace scale...not quite so flat then. Lol.
Then I think that you've not experienced a lot of linear phase loudspeakers having passive crossovers and full-range directivity (horn loaded). That's what Tom D. achieved with a fully horn-loaded loudspeaker, but almost no one has picked up that it's the cause of them sounding so special. Tom apparently hasn't been able to break through the tough hide of "audiophiles" that full range directivity combined with linear phase transfer function response (in a loudspeaker having passive crossovers only) yields the "Synergy horn" sound quality that captivates so many listeners.
On 5/3/2021 at 7:51 PM, gnarly said:I guess what I'm trying to say, is we need to separate the size of a MEH and its subsequent pattern control , from the response of a MEH and its sonic benefits from close coupling drivers.
Go ahead...separate them...if you feel it's necessary.
I think that I'll elect to have full-range directivity control down to the room's transition frequency (i.e., at least down to 200 Hz), and 90 x 60 degree coverage. BTW: vertical coverage can be less than 60 degrees, but typically not without incurring pattern flip at some higher frequency that's too far from the room's transition frequency. Vertical coverage can be too narrow, too.
I think that D'Appolito arrangements are useful, but not really "horn-loaded". Acoustic coupling of drivers without using horn loading is still direct radiating drivers.
On 5/3/2021 at 7:51 PM, gnarly said:I think the sonic benefits are great enough to pursue any MEH that gets within reach of a sub, no matter how small the MEH.
Then you will be a fan of the type of loudspeakers described in this thread.
For me, there is too much that's lost with this approach--that otherwise significantly adds to the listening experience...when listening to full-range MEHs...(i.e., also having 90 x ~60 degree coverage as a constraining requirement).
Chris
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1 hour ago, gnarly said:
You seem to be saying, unless you go all the way to a very large Synergy/MEH, there's no point going at all. ???? If that were true, there would be no point in the SH-50...
Well, I think that the SH-50 is most definitely a "full range MEH"...
What I'm referring to, above, is MEHs whose on-axis SPL can't make it down to 100 Hz in half space (or perhaps even quarter space). The SH-50 has a -3 dB (f3) point of ~50 Hz. If you look at all the other larger Synergy horns (of which the SH-50 is one), their f3 frequencies are generally at or below 100 Hz.
When the MEH has a -3dB roll off at 300 or 400 Hz, then all of what I said above applies.
1 hour ago, gnarly said:...or any of the small-syn DIY builds...
This is where the waters part in our assessments. I don't see a lot of reason for those type of MEHs, to be honest.
1 hour ago, gnarly said:...To directly answer the question "why go to the trouble of doing an MEH on top--why not just use a 4722"?
I would say to gain the coherence of moving closer to a point source, regardless of where it looses pattern control...
Are you aware that you have to cross over to a separate (and usually direct radiating) bass bin at ~400-600 Hz? That's why I said that the 4722 is a better deal, and much simpler to implement. Doing an MEH that only goes down to 400-600 Hz is instead much easier and better done (from many different points of view) in a single 2" compression driver on the same horn--without extra drivers. The reason for the extra drivers--like the midrange drivers in the Danley--is the added power handling of the midranges to alleviate the load on the high frequency compression driver (a 1" BMS compression driver). Danley also uses the midrange as a "phase link" driver with very narrow bandpass in order to facilitate its use of passive crossover filters for fixed PA duty. That's not really a home hi-fi requirement.
1 hour ago, gnarly said:...I would try to mount some big mids on the 2384 horn just to gain coherence down as low in frequency as possible, again regardless of where it looses control...
I'm not sure what you are saying here. Could you be a little clearer in what you're saying?
1 hour ago, gnarly said:...So my advice is, heck yeah, build small syns too !...
Well, if you just like to tinker, that's certainly okay. But I wouldn't waste much time on that sort of thing, to be honest.
Chris
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1 hour ago, gnarly said:
It's clear to me you understand the physics of what's going on much better than i. But i keep learning...
I was describing the changes in acoustic behavior as the frequencies decrease (i.e., the wavelengths are increasing) to where the distance from the throat to the beginning edge or lip of the off-axis ports is several wavelengths, then eventually it's at one wavelength (i.e., an acoustic impedance bounce--generally attenuating, and eventually the wavelengths correspond to a half wavelength to the horn throat (generally a resonance frequency), and then finally a quarter wavelength (where there is strong attenuation/ cancellation).
At shorter wavelengths, the side walls behave more like canted outward mirrors as in optics. At the one wavelength, half wavelength, and quarter wavelength points, the idea is that the horn volume behaves more like a resonant chamber and the volume geometries become important, not just the side wall area presented. Remember that a horn is first and foremost an acoustic impedance transformer, then it can be viewed as a acoustic wave director--creating directivity in the emitted acoustic energy field.
At the first notch frequency of the woofers, you're seeing 1/4 wave volume resonance effects (very distantly reminiscent of a Helmholtz resonator). But what the behavior actually changes to is a function of the exact geometry of the throat-end section of the horn bounded on the outboard side by the lip of the off-axis ports. If those port edges or lips happen to be located at a pressure (or perhaps velocity) maximum for the resonant waves going by, then more disruption and attenuation occurs. So the idea is that the pressure waves (or perhaps velocity waves) are maximal at the middle of the horn walls (but perhaps not, depending on wavelength). For the geometries of the horn used, perhaps the local pressure or velocity max regions shift toward the creases or internal edges of the horn. So it isn't really clear what the dynamics of the acoustic waves are actually doing around the off-axis ports--it's probably complex.
The first bet, however (i.e., Occam's Razor) is that the mid-walls are where the influence from the side walls is minimal, and therefore where you don't want to put a penetration through the horn wall. That's the reason for avoiding placing the ports at the midpoint between the walls.
However...
Chris
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1 hour ago, tom1066 said:
Chris -
I wonder how a JBL 2384 would work? https://reconingspeakers.com/product/jbl-365359-001-2384-hornwaveguide-3732/
It looks like the 2384 is slightly smaller than the SEOS 30 horn, or at least, about the same mouth size:
I would think that this horn would behave much like a SEOS 30, and it's available in North America. If you're going to "bite the bullet" and do what I call a "hybrid horn/direct radiator", you could use the 2384 on top of your favorite direct radiating bass bin, and have performance that's very similar to the JBL 4722:
My next question would be: "why go to the trouble of doing an MEH on top--why not just use a 4722"?
Perhaps by now you might see why I want to break these types of MEHs into a separate thread. There is a lot more head scratching going on when the horizontal horn dimension is less than 35-40 inches (the actual mouth size--not the horn flange size). You begin to question why you're going to all that trouble to avoid spending a few hundred bucks.
If you're right on the edge of not being able to afford good horn-loaded loudspeakers of the full-range MEH design (i.e., the K-402-MEH), you'd be doing bottom dollar on the compression driver, woofer(s), and DSP crossover, and having to live with the system noise floor to do that (or playing with resistor attenuation networks to drop the noise floor from the DSP crossover).
I think that working an extra couple of weekends for overtime pay (if an hourly wage employee), not going out to eat for a while (i.e., bringing your lunch to work, etc., or doing dinner at home instead of fast food runs, etc.), or cutting down on your cellphone bills by cutting back the "bells and whistles" extras tacked onto your bill would be a key enabler to get a setup that avoids all these issues.
Chris
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1 hour ago, gnarly said:
I find i can get polars nearly as nice as when using off-axis ports!
"In God we trust...everyone else bring data."
Do you have some polar sonograms of the differences? I would be extremely interested in seeing that data. That's a lot of work that can be shared or perhaps leveraged with others tackling the same MEH design problems.
Some of the above leads me to believe that there is a fair amount of guesswork still occurring without a full study of the effects of where to put the woofer/midrange ports and how big/their shape should be. (I.e., if what you say is true, then Danley isn't putting the ports in the corners of the horn for polar consistency purposes--which I do find both interesting and hard to believe.)
There is quite a lot going on in terms of frequency-dependent reflections (like optics) and less-than-half-wavelength volume and area support of the developing waves going (like horns operating near their axial 1/4 wavelength frequency or operating loudspeakers below the transition frequency of a room), with a seamless transition between the two right around these extra (non-throat) ports.
I suppose you have found that crossing the lower frequency drivers to the higher frequency ones actually require a bit of overlap (or at least a "zero lap" on the 1/4 wavelength from the throat entrance plane (i.e., not the acoustic center of the attached driver). I believe that each MEH DIYer is rolling their own, and not really discussing the tradeoffs of where to cross. I've found that crossing the higher frequency driver right at or just below (in frequency) to the natural bounce frequency of the lower frequency drivers smooths out the phase and SPL response, and the polar response (to some degree).
Chris
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7 hours ago, Chris A said:
Whereas a couple of 12-inch woofers and a BMS 4590 on a SEOS-30 would cost somewhere around a grand per channel.
This is a valid design constraint--cost--and it comes up everywhere in sound reproduction as either the most limiting factor or second-most limiting factor in loudspeaker design. Probably the most limiting factor in loudspeaker acoustics performance is the rather arbitrary and extreme limitations on the visual size/shape of loudspeakers.
7 hours ago, Chris A said:The whole idea behind this is to find a solution that is as ready made as possible and here the SEOS-30 seems to be the second best option after the K-402 at a much lower price point and at least in EU it’s easily available.
Actually, I believe the best option is a plywood dual-flare horn. This is the solution provided by Bill Waslo's Synergy Calc spreadsheet.
But if you believe that you cannot do it yourself and that reasonable carpentry services are not available, then I suppose that the SEOS-30 is the best available "bought" horn, but note the limitations of its horizontal (i.e., major dimension) mouth size to control the loss of horizontal directivity to below 300 Hz (or lower) is a significant factor.
Even buying dual-flare plywood horns from abroad would be an option if carpentry rates are perceived to be too high where you live. Note that Danley uses mainly plywood dual-flare horns, in addition to its "molded Synergy" (SM) series of loudspeakers. This is an area that is clearly ripe for third parties to provide assembled or even flat-pack MEH kits. One might ask where the bass bin box that is required for use of the SEOS-30 in-room--but not in room corners--comes from. Does that also require carpentry skills to produce?
Chris
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Basically, the Dutch & Dutch 8C uses diffraction (two woofers + ports --sort of like a line array, but in this case arranged differently) to control horizontal and vertical directivity into a cardioid-like pattern.
The patent: https://patents.google.com/patent/EP3018915A1/en
Horizontal directivity sonogram:
Vertical directivity sonogram:
Chris
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53 minutes ago, Chris A said:
Also I would aim for a x-over point around 400 or 450 Hz or so, which allows for more (and cheaper) options than the Axi2050.
This is essentially the same crossover frequency as the original Klipsch Jubilee and the Klipsch KPT-942 (using the K-402 horn), as well as other KPT bass bins.
The idea of using an MEH is to get a single horn aperture to house multiple acoustic drivers that are arrayed by their pass bands (lower frequency drivers toward the horn mouth on "off axis" ports that are not on the horn's centerline, and higher frequency drivers at or very near the horn throat). It is noted that the K-402 horn itself is capable of supporting a single full-range driver (the relatively new Celestion Axi2050) down to ~225 Hz, easily, thus eliminating the need for an MEH.
So the use of a smaller MEH that may or may not use separate midbass or midrange drivers is actually borne out of the need to reduce the costs of the horn/driver combination. Secondary considerations include reducing the size of the horn mouth, but at a cost of requiring a separate (and usually direct radiating) woofer/bass bin.
So the smaller MEH should be focused on cost savings and the appearance of a smaller horn (which is actually not smaller than a full-range MEH). Examples of these sort of hybrid MEHs are found at diyAudio. Curiously, the source for the original "Synergy" and "Unity" horns (Danley) seems to avoid making MEHs that require crossing above ~100 Hz, with the possible exception of the newly announced "Hyperion", which will actually cross at 260 Hz to dual "subwoofers" (actually direct radiating woofers tuned to 14-260 Hz passband).
I do think that it's fair to also discuss at length on what the "small syn" means in terms of midbass and bass performance. In general, unless crossing to a folded horn bass bin like the Khorn, La Scala, Belle, or Peavey FH-1, etc., the smaller MEH will lose directivity below the crossover frequency to the woofers, thus requiring careful in-room placement to generate flat SPL response in the bass and midbass (midbass here is defined as being above 100-200 Hz--the typical home hi-fi room's transition or Schroeder frequency), but will create an unbalanced power response in-room unless placed in full room corners. This design trade has significant consequences, in my experience, that puts the small MEH into a different class than the full-range MEH that can cross to subwoofers below 100 Hz.
One possible alternative approach on the bass bin: use a "Dutch & Dutch" style array of woofers to approximate a line array for a narrower range of listening angles. Perhaps more discussion of that approach has merit, but note that this drives the cost (and size) of the resulting loudspeakers up to be in competition with a single K-402/Axi2050 combination with 15" off-axis woofers, than also can support a 17-500 Hz passband in quarter space loading.
Chris
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Here is the genesis of this thread from the original K-402-MEH thread:
On 4/28/2021 at 5:00 AM, Vathek said:First post and not even Klipsch related, but I think reasonably on-topic in this thread: Since over here in Europe K402 are special order through pro install dealers and prohibitively expensive, has anyone here thought about MEH-ing a SEOS-30 or even done so? That's the biggest easily obtainable ready-made horn suited for the job and relatively cheap. The flat conical surfaces should make it easy to work with regarding woofer mounting / porting too.
14 hours ago, Vathek said:Thanks everyone. The reason I’m looking at the SEOS-30 is mostly build simplicity. I’m in a big city with no back yard, garage or anything like that to use for wood work. So for something based on Bill’s spreadsheet I would have to hire a carpenter and then things get expensive quickly. Whereas a rectangular CLD box can be built at home with pre-cut wood from one of the various home depot like stores here. What intrigued me about the K-402 MEH in this thread was the omission of the midrange cone drivers by using a large compression driver, which makes it so much easier for this ready make approach. Most threads / projects go the 1-inch plus 4-inch cone midrange route, this is why I posted here.
I’m fully aware a SEOS-30 will not control directivity down to Schroeder frequency unless I put it in my shower, but if that was a sine qua non criterium there would only be a handful of speakers in the world in the first place. It’s a compromise I would be willing to live with. Since autotech don’t put their prices on the website, I’m not going to make them public here, but you could easily get a surround system for the price of a single K-402 and they’re extremely well built from about 10mm thick fibreglass (which might be just about perfect for the woofer taps). And in Europe they’re readily available, I’ve bought several of their smaller waveguides from them. I realise that the situation might be pretty much the opposite in the US.
Also I would aim for a x-over point around 400 or 450 Hz or so, which allows for more (and cheaper) options than the Axi2050. I’m not trying to make the argument that any of this is better than the Axi2050 on a K-402 (not at all!), but three pieces (LCR) of that combo would set one back around 10k over here, and that’s just for the horn and the compression driver. Whereas a couple of 12-inch woofers and a BMS 4590 on a SEOS-30 would cost somewhere around a grand per channel. And the 400 - 450Hz crossover has been proven to work in many MEH’s with the 1-inch plus (one or several) 4-inch midranges.
If I had (access to) a proper wood work shop, I would absolutely pursue the plywood version based on Bill’s spreadsheet. The whole idea behind this is to find a solution that is as ready made as possible and here the SEOS-30 seems to be the second best option after the K-402 at a much lower price point and at least in EU it’s easily available. The BMS 4590 is more expensive than a 1-inch and a couple of 4-inchers, but it’s “bolt on and done”. The key to the whole thing is the choice of woofers and the location, shape and size of the woofer taps and maybe some sort of ‘mounting construction’ for the woofers. And that’s really what my question was aimed at. I realise that was way too implicit in my initial post. And if nobody has done this with a SEOS-30, I guess I’ll have tackle it myself. But I haven’t even been able to wrap my head around Hornresp, so this might prove to be a challenge.
Chris -
Because of the inability of getting K-402 horns internationally (outside of North America), and the interest in MEHs seems to be continuing to expand, this thread is focused on those MEHs that are planned to be crossed to separate bass bins above 100 Hz.
There are several threads that can be used as resources here:
1) the original "full range" MEH thread based on the K-402 horn
2) the "small syns" thread over at diyAudio, based mainly on Bill Waslo's spreadsheet and other, smaller existing horns
3) other MEH threads at diyAudio that are focused on specific horns (with links found on the thread linked just above)
This thread is initially set up to discuss the use of the largest SEOS horn--the SEOS-30. A comparison shot of the K-402 and the SEOS-30 is shown, below:
In general, the SEOS-30 horn seems to be available in the EU (+the UK), but is rarely found in North America. This horn provides the necessary "real estate" to construct a nearly full-range multiple entry horn, but one that requires crossing to a bass bin at ~300 Hz ± 100 Hz.
Chris
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I think it's reasonable to ask that you start a new thread on smaller MEHs. I can do that for you if it's an issue for you in creating one. I think that subject of DIY MEHs probably needs to be expanded to at least two threads--with one thread focused more on the smaller MEHs--which have also been popular on diyAudio. I believe that you're going to get more constructive comments in a new thread focused on that subject than you will here. I think that path is a much better alternative than adding to the length of this current thread--which is already fairly long (IMO).
This thread was started five years ago to document my experiences with the K-402-based MEH. I would like to see the comments in this thread stay focused on the K-402-MEH for those that are building them--and we have a few people doing that right now.
EDIT: I will start a new thread to facilitate this under Technical/Modifications section of the forum (the same section as this thread). If that thread becomes focused on SEOS-30 horn use, I can easily rename it as such at a later time.
That new thread can be found here:
Chris
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1 hour ago, VDS said:
Anybody have any amp matching advice with a K402 MEH?
You can do what you like for the woofer channels--they aren't critical. The compression driver channel--probably a good class A or AB amplifier is what I'd recommend. Others may have their own opinions that includes class D. I had a poor experience with Hypex, so I'd avoid class D.
Chris
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5 hours ago, Vathek said:
So for something based on Bill’s spreadsheet I would have to hire a carpenter and then things get expensive quickly.
It looks as if you're trying to justify the SEOS-30. Good luck.
Being the OP (and the originator of the K-402-MEH), I don't really want to deal with "small syns" in this thread, i.e., those MEHs requiring separate bass bins. Would it be too much to ask you to move to a new thread that discusses that particular subject (small MEHs requiring separate bass bins)? This is the only thread on the web that I'm aware of that is discussing full-range MEHs, and your subject isn't a full-range MEH.
Chris
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On 5/2/2021 at 8:10 AM, gnarly said:
Haven't heard any frying bacon yet, but all my listening has been done fully processed...so that might be a factor.
The horns with slots that cause frying bacon sound are like the old EV, etc. "constant directivity" horns--which is the reason why most of us here don't use that term any more in favor of the term "controlled directivity"...straight-sided horns without slots in the throat--like the K-402 and the K-510 series, etc.
I always hesitate to talk about this issue, because then all the Geddes "HOMs" people tend to appear to poo-poo any discontinuities in the horn throat, in favor of "OS" (oblate spheroid) throats. I'm aware that OS throats also have their issues (that Geddes talks about..but not as if they're defects, but rather as "...well, you don't want to listen to your horns on axis anyway...", which is BS).
Make no mistake--the OS throated horns have problems, too, especially because you really can't listen to them on-axis, i.e. the polar coverage of a 2" throat horn above 6 kHz is most strongly a function of the driver's phase plug design, and not so much the horn--unless you stick a throat lens in to spread out the polars (like Roy is proposing with the "new Jubilee"), but then you've got some big discontinuities in the throat again like the old constant directivity horns, and those old horns don't sound very good above 4 kHz (i.e., the horns having 2" throats). It's 8 kHz for 1" throat horns. That all reminds me of the old JBL horn lenses of the 1950s-70s, that were eventually abandoned in favor of slotted throat and baby butt designs of the 1980s.
So it's the degree of HOMs that are generated that is the issue. With OS throat horns, I think Geddes goes too far. With the old Keele constant directivity horns, goes too far in the other direction. I think that there is a range of designs that are "happy mediums". I tend to avoid slots in throats, but that's because of the poor experiences with the D.B. Keele CD horns of the 1970s-80s.
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1 hour ago, RandyH000 said:
5000$ for a pair of Axi drivers /horns -27 lbs ---0.60 inch wall thickness
Yes, precisely.
Chris
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Here: https://www.lean-business.co.uk/eshop/celestion-lh9045r-2-90-x-45-wide-bandwith-horn-p-3318.html
Not inexpensive: £950.00 per horn.
Here's a narrower one: https://www.lean-business.co.uk/eshop/celestion-lh6040r-2-60-x-40-wide-bandwith-horn-p-3319.html
£1,050.0
Chris
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A much better shot...
I've also found that it's the length of the cavity behind the slot to the throat of the horn which contributes quite strongly to the "frying bacon" sound. I'm not sure of the length of this resonance cavity behind this slot. If it's very, very short, there may not be a lot of issues with the frying bacon sound.
Chris
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42 minutes ago, gnarly said:
but I would say whatever it is, it does have a diffraction slot.
Wow, I didn't see inside the mouth (i.e., they seem to be hiding the fact that it's got a diffraction slot):
That means that above ~5.6 kHz, you're likely going to hear higher order modes (HOMs) to some degree, depending on the abruptness of that slot transition to the rest of the horn.
Not cool to hide the slot from prospective buyers...Parts Express.
Chris
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5 minutes ago, babadono said:
I have a hard time "hearing" capacitors.
I can identify with this statement. Once you dial in the EQ (and especially if using FIR to correct phase at the same time), I'm pretty sure that no-one would be able to break 50% probability of correct identification in a blind trial. Once you get the transfer function sorted out, then almost everything sounds like clones of each other.
Chris
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Here are Mark's comments. Why he didn't post them in 2009, I'm not sure. I don't believe he wants to do these mods for others nowadays, so I have no reservations about posting them here:
QuoteThe schematic for 45 and 75 look the same. I did not try the mod on the D-75 though. If I were to do it, I'd have every confidence that it would work just as well on the D75, but there might be different tweaking of the little band-aid caps. I'd call it minor bench adjusting, but I can't foretell specifically what it might be. It might also be nothing different at all!Obtain the proper schematics for the units you get. There are, if I recall, a few revisions that account for small differences made year to year.Here's the details of the mod:CROWN MODSCrown D45 ModificationsPOWER SUPPLYC8/C9 RAIL CAPACITORS: Mouser # 598-DCMC50V123 12,000uF @ 50V computer grade capacitor. Bypass to taste. These will "just fit" exactly in the space allowed.INPUT CIRCUITU100A-D Replace with Quad OpAmp Texas Instruments TL 084 Mouser# 595-Tl084CN Quad OpAmp 14 pin DIP (1 required).14-pin Gold socket per choice.C101/C201 Black Gate "N/33" non-polar 33uF/16V from www.soniccraft.comC103/C203 Black Gate "N/100" non-polar 100uF/16V from www.soniccraft.comOther caps could be used here, but these are superb sounding and I know of no better alternatives.Remove Diode clamps D109/D209/D110/D210R103/R203 = 1.5K 1% 1/4WR153/R253/R154/R254/R255/R155/R256/R156 = 47K 1%, 1/4W**C108/C208 = 82pF - nominal*C105/C205 = 12pF - nominal*C104/C204 = 8pF - nominal*C102/C202 = REMOVEC125/C225 = Remove*These are starting values that may need tweaking on the bench to get perfect HF response with no ringing or undershoot on 20KHz square waves.**This is only done if you want to raise the input impedance to drive this with a tubed preamplifier. If not, leave these resistors alone.I don't use tube amplifiers, so that portion of the mods I ignored (the second line of 47K resistors).
Since I didn't have a "bench" O-scope back then (2009), I couldn't tell you if I had everything dialed in well.
You can't buy Black Gates nowadays, IIRC. They were NOS back in 2009 when I found a few (...for a price...).
Chris
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26 minutes ago, babadono said:
...do you know how much feedback the Crown D75(A)s have?...
I don't really know. I'm using my ears as the measurement device in this case. Also, I remember the subjective comments from the guy that did the "Duke" (Mark Deneen) 14 years ago were very complimentary of its basic performance before the "The Duke" enhancements. Mark removed the "guardrails" from the amplifiers slew rate, and increased its power supply capacitor sizes rather dramatically. So the difference between the stock version and the modified one is said to be in the extreme high end "sparkles". Very slight differences in my estimation. (I only ended up modifying one D-75A amplifier because that difference was so slight.)
As a comparison to the D-75A sound quality, I'd put them at a subjective "A-" or even an "A" (with the the First Watt F3 I use being an A+--and I'm sure that there are people that will argue this comparison), while the FusionAmp 122 sound quality as a "C" or "D" (Hypex class D amplifiers), perhaps worse. There was a difference on the Jubs/TADs with the FusionAmps which was audible--not an immediate "turn it off" reaction but rather "...what's that sound? It's strange...". I had to listen for a while to put my finger on it, and also enlisted my wife's ears to verify what I was hearing--and she independently came up with the same assessment.
So as far as the D-75A's sound quality is concerned, they do quite well. I'm presently using five of them in my pro rack (I use two of them to tri-amp the center MEH, one for the Jub bass bins, and two to bi-amp the AMT-1/Belle bass bin surrounds).
Chris
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On 4/28/2021 at 5:00 AM, Vathek said:
has anyone here thought about MEH-ing a SEOS-30 or even done so?
I think you'll wind up with a loudspeaker that requires a separate woofer--like virtually all the other "hybrid MEHs" that you'll see over at diyAudio. Only if you place the SEOS30 horns fully in room corners will you have a chance of avoiding a separate direct-radiating bass.
Here is a quote from another thread on the Celestion Axi2050 2" compression driver on a K-402 horn that should be carefully considered:
On 3/5/2021 at 7:15 PM, Chris A said:I have seen no other horns that can fully take advantage of this driver's [i.e., a Celestion Axi2050] very broad-band performance than the K-402 horn. Even the largest SEOS 30 horn isn't big enough to take advantage of the extended low end of this new Celestion Axi2050 driver.
What this is saying is that, if using the Celestion Axi2050, you can cross over to the bass bin at 200 Hz--one driver, one horn from 200 Hz to 20 kHz. And the sound is very, very smooth and precise all the way through that passband.
If you instead use a SEOS-30 with the Axi2050, you're going to need something to close the SPL gap between 400 Hz and 200 HZ. If the loudspeaker is in a full room corner--like corner horns--you can probably span that gap. But the moment that you take the loudspeakers out of eighth space (corner) loading, you've got a SPL response issue.
The problem is just physics: the horn mouth needs to be about 35-40 inches wide to control its polars down to 200 Hz--where boundary gain takes over and controls the in-room directivity below the room's transition (Schroeder) frequency. The SEOS-30 loses its horizontal directivity at ~340 Hz. That's just a little too high for how most people choose to use their loudspeakers (i.e., NOT in full room corners).
The other problem that I've had is that Auto-Tech doesn't seem to respond to requests for quotation for anything. It could be that they're simply ignoring requests from those living in the North America, but I suspect that they are not really selling the SEOS-30 presently--unless you're buying a lot of them in one large order.
Bottom line: look for a straight-sided horn with dual-flare that is at least 35-40 inches across the mouth is the major axis direction. It you're going to do a "full range MEH", that's a requirement--unless you're going to make them obligate corner horns.
I recommend doing it in plywood using Bill Waslo's Synergy Calc spreadsheet. It's a lot less expensive for material costs, and you get to control the exact dimensions (over 35 inches mouth dimension) for the horn.
Chris
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I think that if you're using passive crossover filters, the second figure looks a bit more like a normal impulse response. If you can plot the step function (the integrated impulse response), you can see this more clearly.
It turns out that there is a tradeoff in the polarity of the driver vs. the lower frequency driver. If you're using a DSP crossover, you can sometimes push the phase of the higher frequency driver closer to the lower frequency one, but you have to play with the higher frequency driver's channel delay to do that.
Chris
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I think what you're asking is if the horn-driver will need EQ. I think it will, but this can be provided upstream of the loudspeaker in some sort of EQ--probably at the source (the player). It can also be put into the passive circuitry as a very low-Q notch filter that's set up to take out the rise in SPL at around 1-3 kHz. This can be done using XSim, LspCAD or VituixCAD, etc.
I do recommend using some form of measurement to set up that EQ.
Chris
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Nearly Full-Range Multiple Entry Horns (MEHs)
in Technical/Restorations
Posted
Yes, I'm aware of the limitations of some listening room sizes to handle them. "Cheap" is another issue, not related to acoustic performance. That's a barrier to entry for some DIYers that are severely budget constrained. But when you look at the cost of a new pair of Cornwall IVs, I think the cost of the K-402s isn't quite so bad.
If that's all you can handle, then that's it. The listening room itself is the limitation. However, I would also point out that I've seen many people state that they can't handle the width when what they are really saying is that they don't like the visual width in their room. I try to go with the acoustic performance first.
This actually works quite well (I use AMT-1s on top of Belle bass bins currently as my surrounds in my 5.2 array, and they are outstanding). Using K-402-MEHs and/or Jubilees, doesn't really constrain where the listener is located, however--anywhere from sidewall-to-sidewall in multichannel music mode (LCR).
Welcome to the forum!
Chris