I’ve seen more than one person assert that you don’t need expensive drivers to make a really good MEH. I have no reason to doubt that, but what if you wanted to simplify things by just making a 2 way MEH, but you also wanted it to be full range ie no subs required. There is at least one mid/ woofer which seems not only capable of covering say 30hz to 1000hz but of doing so with exceptional performance. I am of course talking about what may be the best driver yet produced, the Purifi 10”. Yes its expensive, but I’m wondering if you could make a really great sounding full range MEH with just one Purifi 10” + CD per channel and hence save on buying multiple other mids and woofers ?
There are plenty of experienced MEH builders of this parish and I’d love to hear their thoughts on this.
There are plenty of experienced MEH builders of this parish and I’d love to hear their thoughts on this.
An MEH would need to be stand mounted or similar……so the space below is better served otherwise than a stand IMO……a quality pro 15” woofer driven up to 600hz is all that’s needed……use a 1.4” compression driver in a large horn instead….theres’s your very efficient and effective two way where the low bass frequencies can benefit from the boundary gain of the floor.
Won't work:
1) The reason that the Danley SH-50 is a three way, is because the Synergy Crossover depends on the drivers radiating from various points along the Z axis. Basically, the passive filter on each segment (highs, mids, lows) leverages the delay that's introduced. For instance, the midrange taps in an SH-50 are 9cm from the throat. 944Hz is 36cm long. The SH-50 is crossed over at approximately 944Hz. Those numbers aren't coincidental; the passive crossover introduces a delay, and that delay is what causes the radiation from the mid and tweeter to be in-phase EVEN THOUGH THEY RADIATE FROM A DIFFERENT POINT IN SPACE. That's the critical part; a Synergy Horn is radiating a wavefront that's in-phase both on and off axis, BUT IT DEPENDS ON THAT DELAY.
2) If point number one makes sense, then you'll see that the wider the bandwidth of a Synergy horn is, the more driver ranges you'll need. To get an SH-50 to play down to 30Hz, you would certainly need an additional band of drivers. You would need a four-way. Which is basically what happens when you put an SH-50 on top of a Danley Sound Labs sub, especially if you bring the subwoofer 'forward' of the SH-50 top.
If you google "Bend it like Bateman", I published a design for a two-way Unity horn that used two drivers: an 8" woofer and a compression driver.
It didn't work; it basically behaved like a conventional two-way. I could get it to measure flat-ish on axis, but the off-axis response wasn't well behaved, because the radiation of the woofer isn't symmetrical. (Because there's only one.) Probably about as close as you could get, with two drivers, would be something like the Danley SPL-Runt. That had two Eminence eights and a BMS 4550 compression driver. It's F3 was something like 150Hz! The SPL Runt was one of the very few sealed Unity horns. Not sure why that was. It may have been due to the phase response, or perhaps it was simply because the woofers had a QTS that wouldn't work in a vented box.
@Patrick Bateman; at point 1 you said the passive crossover introduces a delay. Surely its the physical separation that creates the delay ?
If instead of using a passive crossover you used a super powerful DSP solution like AudioLens then you would be able to get perfect time and phase behaviour across the full frequency range. I take the point though about the off axis response problems associated with using just one mid / woofer.
If instead of using a passive crossover you used a super powerful DSP solution like AudioLens then you would be able to get perfect time and phase behaviour across the full frequency range. I take the point though about the off axis response problems associated with using just one mid / woofer.
Passive crossovers introduce a delay. The length of the delay depends on the frequency of the filter and the slope of the filter.
The midranges and the woofers in a Synergy Horn are closer to the listener, to compensate for that delay, and to generate a wave front that's in phase, even though the drivers themselves are NOT radiation from the same point in space.
I don't think there are a heck of a lot of people who've heard a Unity horn and a Synergy Horn side-by-side, but I have. Despite the devices looking similar, they sound very much different. I think the soundstaging of the Synergy Horn is a big step up from the Unity horn.
My assumption, is that a lot of that is the crossover, specifically the things I describe above.
I know it's a meme by now, but there really ARE things that can be heard that aren't easily explained by measurements, and this is one of those things I think. If you look at the Klippel data that Erin published on the SH-50, it doesn't look great. But anyone who's heard them in stereo, they know they can image like crazy.
When I rented a set of SH-50s, I owned a set of Vandersteens. Both speakers are known to image well, but to me, the SH-50 was in a completely different ball park, it wasn't even close. And, again, I think that the DEPTH of the waveguide plays a big part here. The Vandersteens use first order filters, and because of that, the distance from the listener to all of the drivers is about the same. The SH-50 uses higher order filters, and because it does, we have to do some 'tricks' to get that wavefront in-phase. (Which I describe in post #3.)
The midranges and the woofers in a Synergy Horn are closer to the listener, to compensate for that delay, and to generate a wave front that's in phase, even though the drivers themselves are NOT radiation from the same point in space.
I don't think there are a heck of a lot of people who've heard a Unity horn and a Synergy Horn side-by-side, but I have. Despite the devices looking similar, they sound very much different. I think the soundstaging of the Synergy Horn is a big step up from the Unity horn.
My assumption, is that a lot of that is the crossover, specifically the things I describe above.
I know it's a meme by now, but there really ARE things that can be heard that aren't easily explained by measurements, and this is one of those things I think. If you look at the Klippel data that Erin published on the SH-50, it doesn't look great. But anyone who's heard them in stereo, they know they can image like crazy.
When I rented a set of SH-50s, I owned a set of Vandersteens. Both speakers are known to image well, but to me, the SH-50 was in a completely different ball park, it wasn't even close. And, again, I think that the DEPTH of the waveguide plays a big part here. The Vandersteens use first order filters, and because of that, the distance from the listener to all of the drivers is about the same. The SH-50 uses higher order filters, and because it does, we have to do some 'tricks' to get that wavefront in-phase. (Which I describe in post #3.)
Yeah, you got it basically right, though when I was tinkering with a POC using some BW limited 4" 'FR' drivers it could be done with no XOs, just some notch filters and IIRC Tom mentioned that the passives were strictly for backup in case of electronics failure.
Anyway, when I auditioned their ~free space setup suspended in a big metal warehouse with a BR? video of a Diana Krall solo w/piano; well, 'you had to be there' in more ways than one, didn't even need to close my eyes to feel like I was back at our near front row center seats at her 1st performance at Atlanta's 'Fabulous' Fox Theater.
As for bass, there appeared to be at least one of every model at the time seemingly willy-nilly scattered around the room with apparently no matching pairs, but never was able to locate where it was coming from even though they were all offset to the left side by the open! bay doors and the video on the right with closed wall.
Went there to audition the Matterhorn sub, but was behind schedule, so also watched part of some then popular sci-fi movie that had a bit of infra bass, which was an even greater 'eye opener'! Not sure my gut could have handled what the Matterhorn's performance potential could have done with it.
That said, never seen so much electronics outside Cape Canaveral and Marshall Space Flight Center's mission controls, though didn't look closely enough to try and trace it all out.
Anyway, when I auditioned their ~free space setup suspended in a big metal warehouse with a BR? video of a Diana Krall solo w/piano; well, 'you had to be there' in more ways than one, didn't even need to close my eyes to feel like I was back at our near front row center seats at her 1st performance at Atlanta's 'Fabulous' Fox Theater.
As for bass, there appeared to be at least one of every model at the time seemingly willy-nilly scattered around the room with apparently no matching pairs, but never was able to locate where it was coming from even though they were all offset to the left side by the open! bay doors and the video on the right with closed wall.
Went there to audition the Matterhorn sub, but was behind schedule, so also watched part of some then popular sci-fi movie that had a bit of infra bass, which was an even greater 'eye opener'! Not sure my gut could have handled what the Matterhorn's performance potential could have done with it.
That said, never seen so much electronics outside Cape Canaveral and Marshall Space Flight Center's mission controls, though didn't look closely enough to try and trace it all out.
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And me too……but at and below 600hz, if the center to center distance of the woofer to the CD can be kept less than a wavelength, it’s a non issue…….so the apparent gains of driving the bass from a separate enclosure take over from a performance standpoint. What you’re looking to build is a two legged tripod.
Art Welter's SynTrip is exactly what you are asking for: a 2-way MEH covering 100 Hz up. It uses a pair of 10" woofers in bass reflex with a 1.4" CD and crosses to the CD just under 1 Khz. Back in the day, I built a 2-way corner MEH using 4 4FE32's with a BMS4550 CD that sat on top of a 15" woofer and crossed to the woofer at 300 Hz.
Yes I’m aware of the SynTrip thanks. It isn’t what I was envisaging though because, as you point out, it only goes down to c.100hz. The Purifi 10” can happily do 30hz - 1000 + hz. That’s one of the things that makes it special.
So based on the comments received so far, it looks like my idea doesn’t work and I should look at using cheaper drivers to get me down to a crossover frequency where some separate 15” / 18” woofers could take over.
You could do that, but note that you're really looking at reduced bass output capabilities for such small diameter woofers. I'd also recommend looking at 12" diameter woofers (two per horn) to keep the midbass/midrange modulation distortion sidebands down to inaudible levels.
Been there--here. Please don't underestimate the displacement needs for the bass below ~100 Hz, where the horn loading of MEH woofers transitions from the horn aperture to room gain. I strongly recommend using Hornresp to simulate the bass performance within quarter or eighth space room loading.
And note that you will really want to cross at or below 500 Hz (not 1 kHz) to the compression driver--or you're going to end up with a Danley Unity or Synergy midrange (phase link) design, like was mentioned above.
Chris
Thanks for the comments Chris. As I’ve indicated I’m now dissuaded from using the Purifi woofers in this way. However it’s worth saying that it would be a mistake to judge them on the basis of other 10”woofers. I’ve heard speakers that utilise them and they had exceptional, clean, taut and very deep bass - better than any 15” that I’ve heard. I have no affiliation with Purifi BTW.
Running the CD down to 500hz would require one of the dual diaphragm CDs; everything is a compromise . . .
Running the CD down to 500hz would require one of the dual diaphragm CDs; everything is a compromise . . .
modulation distortion is another reason you don't want your midwoofer doing double duty as your subwoofer
If I had a pair of the Purifi 10"s, I believe i'd try making something similar to the Meyer X-40.
(knowing I'd still be using sub(s).......can't no stinking two-way ever not need subs 😛)
As far as in a MEH...in addition to the difficulties already raised, the 25mm xmax would be a real pain to incorporate.
(knowing I'd still be using sub(s).......can't no stinking two-way ever not need subs 😛)
As far as in a MEH...in addition to the difficulties already raised, the 25mm xmax would be a real pain to incorporate.
If you design with good margins in displacement (i.e., large enough woofer diameters, and number of woofers used per horn) and also pay attention to the 1/4 wavelength drop-off frequency (e.g., in the K-402-MEH, this was ~100-160 Hz where the first 1/4 wavelength transitions from the horn to the room boundaries (preferably either quarter space [against a wall] or eighth space [in a corner]...and within 1.2 m (about 47") of the floor) will be smooth and support acoustic horn loading to the woofers below that horn 1/4 wavelength transition frequency.
If your MEH (the horn itself) is a bit deeper than 17"/43 cm of the K-402 horn, you will be able to support horn loading to a lower handover frequency to the room boundaries. This means that you can place the MEHs a little further from the room walls/floor and still achieve good horn loading of the woofers below that midbass transition frequency.
The whole trick is to maintain fairly good horn loading across that transition frequency from horn loading to room boundary loading, then you can take the EQ boost on down to 30 Hz or even lower (if using DSP). I personally get 18 Hz (-3 dB point) out of my center K-402-MEH prototype with the two 15" woofers (about 18 dB of total boost relative to midrange band while in quarter space loading). You could probably get about as low of a -3 dB point in a smaller listening room using 12" woofers. Just keep the MEH backs against a wall.
If you're willing to use a separate subwoofer, then all these figures used above will require less stringent boundary loading and smaller diameter woofer(s).
JMTC.
Chris
If your MEH (the horn itself) is a bit deeper than 17"/43 cm of the K-402 horn, you will be able to support horn loading to a lower handover frequency to the room boundaries. This means that you can place the MEHs a little further from the room walls/floor and still achieve good horn loading of the woofers below that midbass transition frequency.
The whole trick is to maintain fairly good horn loading across that transition frequency from horn loading to room boundary loading, then you can take the EQ boost on down to 30 Hz or even lower (if using DSP). I personally get 18 Hz (-3 dB point) out of my center K-402-MEH prototype with the two 15" woofers (about 18 dB of total boost relative to midrange band while in quarter space loading). You could probably get about as low of a -3 dB point in a smaller listening room using 12" woofers. Just keep the MEH backs against a wall.
If you're willing to use a separate subwoofer, then all these figures used above will require less stringent boundary loading and smaller diameter woofer(s).
JMTC.
Chris
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