Why Synergy horns?

In another thread I was asked, if I would provide more details about my speakers, so I thought why not?

I have played on active 4 way horn systems since 2016. First iteration was front loaded bass horn, midbass horn, tractrix midrange horn and tractrix tweeter horn. I worked nicely, with all the attributes associated with well implemented horns. Clarity, dynamics, realistic live sound etc.

However some problems will arise, with such horns. First of all, the center to center distance between the different horns is big, compared to the crossover frequencies. We need to be within 1/4 wave in distance at x-over for a seamless transition. For instance if you x-over from the midrange horn to the tweeter horn at 3 KHz the c-to-c distance would have to be 340/3000/4= 2.83 cm (1.11 inch). This is virtually impossible with "normal" horn configurations. This problem rears its ugly head, at every x-over throughout the audio frequency range. As frequency decreases, the wavelengths gets bigger, but so does the horns in the specific bandpass and then c-t-c also increases. It is a linear problem, that can't be solved with the regular approach, aka stacking horns on top of each other. This creates interference problems and lobing in the vertical response curves, that will color the reflection from floor and ceiling. Secondly a large column of vertically stacked horns, will push the sweet spot (SS) further back, for the horns to be perceived as more coherent and integrated, with one another.

But the biggest problem is that almost all horns beam with increasing frequency, it's their way of nature so to speak. What that means, is that the off-axis FR will not be similar to the on-axis FR. This translate into a poor power response, which is not considered a good thing, in terms of best sound quality.

Luckily we can circumvent all these problems with clever engineering and have our cake and eat it too, so to speak. Enter the Synergy horn.synergy.jpg
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Hopkins, a dip between 200-300 Hz is most common on many speakers and results from the floor bounce cancellation and as you also found out, this dip, changes with distance. The vertical driver array, when done right, can prevent that dip.
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Concerning the array of mid-range drivers, are they all playing at the same loudness level? I am curious, as this design is always criticized for its potential "comb filtering" effects.

Thanks. The very cheap (400€) Teufel speakers I use (mostly for TV and some background listening) have this issue with a dip around 250 Hz, which is more or less pronounced depending on distance you listen to. What is it about the Snell that avoid this? The height of the lower drivers, the fact that there are 2 sets of 2 drivers (top and bottom)?...
This is a mtm design, quasi D'Appolito configuration. Mostly symmetric around the tweeter. Instead of just letting the interference from distinct drivers land where it lands and produce lobing in the polar response as usual, it leverages it to contour the polar response in the vertical plane. With increasing frequency you get increasingly more controlled directivity, mitigating zeroth and first order reflections on floor/ceiling. It sounds fancier than it is.

This doesn't tell you squat (or very little at least) about the general perceptual quality of an mtm or any other config. It all comes down specifics and specific implementations. Just like the shown power response, it is a single data point in a constellation of them. I've heard mtms that sound great, flacid and outright horrible. Same for frequency response, from great to criminal all within the same +-2db in room on axis.
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So RCanelas, in your opinion frequency response and even directivity is not the most important factor in a speaker, or how we perceive sound quality? We leave out the room for now.
Though the question is not directed to me, and I am far from a specialist, it seems pretty obvious from my experience of various speakers that "resolution" is something which is not captured by frequency response and directivity.
Just for the record, I certainly don't perceive myself as a specialist either. I learn all the time and hope to continue doing so, that is a big raison d'etre for being in this hobby.

But back on track, lower distortion equals better resolution. Speaker drivers have mostly 2. and 3. harmonic distortion, the rest is filtered out, due to mechanical damping. Then you have break-up issues in the driver, perhaps some doppler effect.

Hard or soft membranes will give a bit different dispersion characteristics and soft membranes coupled with a weak motor system and relatively high loss in the suspension (lowering Qms), will sound less detailed. But it is not the soft membrane in itself, that is responsible for this. I absolutely believe as long as the driver is well constructed and used properly, the membrane will not produce a "sound of its own". But loudspeakers is full of compromises and conflicting considerations, some more than others though, so pick your poison :)
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Today I did a test with two diffrent foils and a piece of Rockwool of 50mm, for the final panels I will go for 150mm.

I tried the thinnest foil I could find, namely painters masking film with a thickness of only 7micron. I also used a slightly thicker trash bag of 15micron. You can see from the measurements that the thicker LDPE reflects less than the thinner HDPE (Low vs high density PE..).

Now RT60 is measured to only 11.5khz, so I'm worried unnecessarily. But the question is whether it still affects with your perception and whether it makes sense to find thin LDPE? Which is obviously harder to find with the right specs and dimensions. :rolleyes:

I have attached a picture of how I measured. Where the decrease in HF means it is reflected and not absorbed. (For clarification.)


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...a couple of things come to mind. Very thin mylar film is available as emergency rescue "blankets" at outdoor stores/online. Spray adhesive might work on that too (test).

It's a little bothersome to do, but I built some cylindrical "tube traps" using commercial rigid fiberglass for pipe insulation. On these, I cut vertical pieces out, leaving reflecting and absorbing vertical "strips" on half of the tube. On the other half, I removed all of the foil backing. The ends are sealed with wooden discs.

I also used different diameter tubes to mix the effect, and some I very loosely filled with fiberglass batting.

I wanted to learn hands-on about these treatments, so I researched quite a bit and built many types, mixing them with commercial products.
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So RCanelas, in your opinion frequency response and even directivity is not the most important factor in a speaker, or how we perceive sound quality? We leave out the room for now.
I don't think that is what I said at all.

Those are both of some of the most important measures to start designing a loudspeaker indeed. Alas they are highly correlated, correlated with another few parameters and most important, they are very difficult to extricate from a room. I mean, they are trivial to measure and design for, you get a kippel like us, spin it out and get a flat semi-anechoic response. From there to a real room... a lot can (will) happen. You need a more understanding of how your loudspeaker actually functions to get something interesting out of it.

This is of course for most loudspeaker topologies. Synergy horns are a fun exception due to the extremely unusual and almost linear relationship between a lot of things. MTMs are not exceptions. Their directivity is controlled, but not even, for example. They can introduce a number of other challenges, mostly due to the difficulty of balancing acoustic center distances with cone area, sensitivity, and obviously impedance.

If you ever find someone saying they have an audio magic bullet, no compromises needed, you can probably disregard them without much concern. Irregardless price, topology, size and color.
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Nick, your findings seems to be oppesite mine, regarding the plastic wrapping. I will try a small test later.
Another weekend, another concert

The annual Slay-Town one day festival blasted through the city and delivered some bone crushing metal. Especially Hate from Poland was a demonstration of precision and power with their blackened death metal. That kind of music demands top notch sound, otherwise it can turn out as an atrocity. Fortunately the sound engineer delivered the goods, with fabulous dynamics and clarity to serve the musicians and the metal crowd.

Quick and dirty mock-up cardioid speaker, with 15" P Audio C15LF and 8" Eighteensound 8NMB420 drivers. The general idea is to control the dispersion down to the upper bass (100-150 Hz). A cardioid speaker is a hybrid of a closed box speaker and a dipole, so there will not be much output below aprox 100 Hz, so subs are mandatory. Measurements will tell where and what x-over filters to use, to get the most uniform dispersion. The 8" 18sound will be low passed aprox 500 Hz and then a small synergy horn on top will take over.

PS speakers are not finished yet ;)

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Made some cab progress.

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The general idea for the 8" chamber is to make some sort of back wave trap. Don't know if it is necessary, due to to the cardioid concept, but it works for closed cabs.
Got to visit some audio folks and listen to their systems. I find that an interesting and funny part of being is this very special hobby. I focus quite a bit to be as unbiased as one can be, when I hear new systems and to be open minded, but not so much that my brain falls out :D When one visit other people, you are on their home turf and you listen on their premise. I try to understand what it is that they are trying to achieve and I don't have to agree, just reckon, accept and get an understanding of their approach.

First visit was at an elder nice fellow. We have met at various occasions and he has also been at my place for at listening visit. He is an "old school" guy, analog 90 % of the time and with a one of a kind and rare system. Speakers are 4-way Daner Open from an old danish manufacturer Daner Audio produced in the 80's. Turntable Technics SP10, Van den Hul Colibri pickup, Daner Expand MC preamp, Daner Detal preamp, Electro Research A75 cl A power amp, so vintage gear.


The front wall is damped with rockwool insulation covered with wood wool acoustic boards, taming the relatively big room (40-50 m2), which is a very clever move given the special listening situation. It is always difficult to get used to the sound in a foreign place. Different room, different speakers and different music. Sitting relatively far away from the speakers, about 6 meter is a bit unusual and naturally the music seems i bit far away and it does compromise the pinpoint image and depth to some degree, and painting all with a somewhat broader brush, but once accustomed it was ok. Having so little direct sound and hearing mostly reflected sound in the listening position, is the exact opposite of what I'm doing, so it was a bit special. Listening to some familiar music, The Police (Ghost in the machine) and some old Saga tunes (Silent Knight), the tonal balance was a bit thin to my ears, lacking some output (warmth) in 80-300 hz. The sub bass was there, but not strong and detailed enough. The upper registre was ok detailed and even with ok dynamics, but after some time I noticed a bit of listening fatigue and we played music between 75-90 dB, so not super loud by any means.

This is a premium, albeit a bit extreme, example of how different people has different approaches to hifi, due to conscious choices or necessities. Nevertheless, always good times to visit fellow audio people, which is highly recommendable.

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Unusual setup, to have the speakers so far away, moreover in what seems to be a dedicated room.

Looking forward to your impressions of the Mofi Sourcepoint 8...
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Long listening distance and little acoustical treatment = large horn speakers with narrow and constant directivity down to Schroeder.

But rear wall still needs to be treated.
Should we stick to physics and proof or what an individual thinks? Ethan Winer isn't an acoustician FIY.

You might want to read the thread you linked to. Ethan Winer is being corrected by more knowledgeable people in the field.
And, FYI, also banned on WBF. Very few have had the "honor" to be part of that rare list. That should tell the OP something.
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