Small Syns

Hi grec13,

Well, if you used that, you of course won't have the same design (much at all, really). The horizontal directivity control to a lower frequency (via array effect) will be gone, and much of the mid-to-woofer array crossover tuning will be to no real point. Also, the vertical pattern will have a notch in it's off-axis response (because the larger cone center can't get close enough to the center of the waveguide, nor be practically placed behind part of the waveguide).

But otherwise, the general idealized rule for changing a 4ohm crossover for on 8 ohm driver is that you double all inductor and resistor values and divide all capacitances by half. That of course ignores differences in driver responses and resonances, so if you go that route I'd recommend getting a measurement microphone and adjust things after you get it built for at least a good on-axis response.

(btw, the woofers I used aren't B&C, they're FaitalPro)
Hmm, in this case is better to get Faital Pro than. If I will use 4 Faital Pro instead of 2 woofers - is it required to change xover? Thank's again.
 
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@ Patrick and others: I have been scratching my head about this: when mating a small cone driver to the horn throat: could it be that better results might be obtained be not using the adapter as proposed by X, but rather design a phase plug with internal channels a la compression driver design principles, following the cone profile on the driver side, but emerging in a flat section connecting to the horn throat? Anyone willing to make a BEM sim?

Once you have a 3D printer running, there are no limits in making such items.

On issue I a foresee is how to deal with the surround of mini-cone drivers. This may require a bit of experimenting.

Good luck,

Eelco
 
I got it. What about four Faital Pro 6" instead of two?

That would certainly work better than the single 10" woofer. You might have trouble getting the waveguide assembly (with attached midrange) into it's hole with woofers on top and bottom, but it would probably still go in ok (put it in rotated 90degree and twist as you set it in).

The four woofers would put their apertures about 10.75" apart vertically (quarter wave at about 315Hz) so there might be some vertical response pattern narrowing below that frequency, but that's likely in the modal band of the room so not likely to be a real issue.

Some advantages:
  • It would be able to play louder of course (in the bass at least). Probably a worthwhile advantage if you got the sealed cabinet route and use a Linkwitz transform to extend the bass.
  • Lowest impdance (currently around 100Hz) would get raised to about double
  • Overall woofer sensitivity would stay the same (around 96dBSPL/2.83V) so the woofer crossover should still work as designed (with doubling of inductors and resistors; and halving of capacitors)

The down sides would be:
  • woofer crossover inductors would need to be twice as many mH (expensive)
  • box volume would have to be doubled (getting pretty big for something "Small")
  • Cabinet design would need to be changed/adapted (not too difficult, but some added work)
  • Of course more expensive (2x woofers, hardware, wood pieces to cut)

But it should be an interesting variation if you want to go that way. Post pix if so!
 
Potential SynsXL candidate?
fc80f78c.jpg~original


I have a pair of these JBL 4722n monsters. Any ideas come to mind?
 
I imagine you could get that waveguide to work in a synergy arrangement (if you don't mind risking drilling some holes in it). I'd make sure to do some modeling in Horn Response before you get your drill bits out!

That's a 1.5 exit throat, though, so you'd have to go with a larger format compression driver or work with a cone like xrk971 and some others are doing. But that would let you cross over lower and use a larger midrange or woofer for the synergizing. If you wanted to do the spaced woofers trick, a pair of 8" or maybe even 10" drives could probably work with something that big.
 
Hi Bill,
Yeah, the SB65 xrk971 used has really piqued my interest too. I guess I'll order the SB65's and CAD up some adapters for 3D printing. I also have some BMS 4555 that could be an option, but I don't have measurements of the combo so I'll do both at the same time.
 
Take a look here for some ideas on working with larger horn and larger format compression drivers -
https://community.klipsch.com/index.php?/topic/161404-a-k-402-based-full-range-multiple-entry-horn/

I think now is a good time to briefly discuss a related subject of interest, since Bill opened the door...;)

The first successful multiple entry horn design suitable for home use--the Unity--is no longer patented. I'll refer to multiple-entry horns (MEHs) instead of "Synergies".

The MEH brings several things to the table that other conventional front-loaded horn designs do not. I've also found that discussing requirements/ capability prioritization is highly productive. Here's an implied requirements/capabilities prioritization through the lens of the MEH:

1) Acoustic point-source (all three axes: x, y, and z).
Danley has made a lot of gains in the PA and permanent installation industries because of this design capability of the Synergy and related Paraline series. If you don't value this capability in your own designs, then using MEHs is significantly depreciated.
2) Controlled polar coverage angles/constant coverage (per axis)
Like no other loudspeaker design approach, this sets the MEH approach apart from all other approaches (especially direct-radiators). Even though I find many DIYers pay lip service to this (and nowadays wind up jumping over the horse while doing it), they don't always know why, except that "it's a good thing to do". If you've not heard a loudspeaker that can do this down to a very low frequency (without disruptions in the vertical or horizontal axes due to use of multiple horn apertures), you probably don't know the effects, in-room, of this capability. Most DIYers and commercial enterprises just sweep the frequencies below ~500 Hz under the rug by inserting another direct-radiating driver or even another horn/cone driver in a folded horn into the design. This has major effects on the resulting sound--that I've found that few want to understand.

One other topic that most "small loudspeaker" crowd want to avoid is mid-bass and bass directivity control. Most people just think that "it's too hard" and ignore the effects of loss of directional midbass control in their designs and implementations. They're losing a huge amount of performance, not the least of which is speech recognition performance and loudspeaker "fullness" or "richness" of most instruments in the most important part of the midrange spectrum.
3) Significant reduction in modulation distortion
Horn loading acts an acoustic transformer/coupler which significantly reduces required diaphragm motion to produce acoustic power. For those that eschew horn-loaded bass because "it's too hard" or "it's too large", the MEH approach offers a unique opportunity to make use of room boundaries to keep overall size and build complexity under control, but while achieving improved coupling to those boundaries over separate folded bass horns of moderate dimensions (but having implementation/design iteration issues)...or separate conventional horn designs of huge dimensions with straight axes that create their own problems. The key is to realize that "maximizing acoustic efficiency" isn't really the design requirement or goal for most DIYers, but rather significant reduction in diaphragm motion over any alternatives, while maintaining the above two capabilities (i.e., requirements coupling).

For those that aren't aware of it, horn loading virtually eliminates modulation distortion as a design concern over any direct radiating design--without exception and regardless of admonishments to the contrary that "it isn't audible". It is..and it's very audible. That's why horn loaded loudspeakers sound so different, even if constant coverage vs. frequency isn't achieved.
4) The combination of all three of the above requirements or capabilities in synchrony.
This is a desirable requirement/capability in and of itself. Having the ability to do well all three of the above at the same time, in contrast to thinking about the above one at a time, is something that is seldom discussed, much less heard in loudspeaker/room settings. Once you've heard it achieved in a full-range loudspeaker the size/shape of a Klipsch La Scala, you'll definitely recognize that this is a requirement itself.
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For those that look at a 35.5" x 21" (90 x 53 cm) mouth size horn which is able to hold its coverage angles full-range in a single horn aperture down to 40 Hz (with polar control handover room boundary support below 170 Hz), and say "it's too big", they're really choosing an alternative design of significantly reduced performance... but they're trying to split the problem into two problems at a point in the listening spectrum that's ill-advised - the midrange (i.e., close to tuning fork "A440"). I find that it's much better to push this point much lower to below 100-150 Hz.

Those lower frequencies that are being temporarily ignored in conversation have to be provided by some other means if they're to have a "full range speaker". Doing this with a direct radiator is, in my experience, the worst way that you can do it, considering the mismatch in capability that occurs when going from fully horn loaded to direct radiating.

Why not just include those frequencies in the design of a single aperture horn-loaded loudspeaker of much smaller dimensions (1/3 the size) than previously thought possible?

YMMV.

Chris
 
Not sure I understand your question. ALL of these Synergy/Unity/"MEH" (though I hate that acronym.... implies a violent yawn!) horns feature midrange drivers mounted on the side of the horn. That's basically their identifying feature.

The midrange's HF rolloff is more of a deep notch, caused by the pressure wave reflecting off the tweeter diaphragm and returning to phase cancel the midrange's forward wave. The midrange's LF rolloff is from either the horn size being too small at the low end to continue to support keeping the energy forward and/or the back chamber of the midrange driver causing the usual sealed baffle type highpass rolloff.
 
Typically I see the mid range drivers "ported" into the horn. I'm considering "surface" mounting for ease of installation. Looking in the horn you would see the mid driver on the side instead of a hole/ slot.

Using Horn Response abbreviations, Ap1 goes to Sd of the mid, Lp is nearly 0, Vtc is nearly zero, Atc is Sd.

I'm concerned the mid response will more closely follow the driver response than the predicted horn response.

I'm wondering if this has been done, tested?
 
You're talking about using a compression ratio less than one, which is not going to generate much acoustic loading on the midrange driver. The size of the full midrange cone on the horn's aperture will disrupt the expansion rate of the horn enough to likely cause issues with impedance bounces at midrange frequencies due to the shape of midrange cone itself.

I recommend at compression ratio closer to at least 3: meaning cutting a hole through the horn with about 1/3 the area of the cone, mount the midrange on the back.

Danley typically uses something like a compression ratio of 10. The reason: using larger ports will start to disrupt the off-axis polars of the horn in that axis. I use a compression ratio of 10 on the K-402-based MEH. The ports are as large as I dare make them.

Chris
 
Typically I see the mid range drivers "ported" into the horn. I'm considering "surface" mounting for ease of installation. Looking in the horn you would see the mid driver on the side instead of a hole/ slot.

Using Horn Response abbreviations, Ap1 goes to Sd of the mid, Lp is nearly 0, Vtc is nearly zero, Atc is Sd.

I'm concerned the mid response will more closely follow the driver response than the predicted horn response.

I'm wondering if this has been done, tested?

Although I've raved about arrays like the Beolab 90, the Danley SH-50 is still the imaging champ. I think this is largely because the sound of the tweeters and the midranges radiate from an area that's about as big as a tennis ball.

(A tennis ball is 2.7" in diameter; the midrange taps in a Danley SH-50 are 3.5 inches from the throat.)

You *could* use drivers bolted to the walls of the horn, but I don't see any real advantage. It's going to make your polars worse (because the pathlengths are greater), it's going to have higher distortion, it will likely have rougher frequency response.


There's ONE upside, and it's a big one:

There's a ton of drivers that don't have the right thiele small parameters for horn loading.

The Tymphany TC7 is an example of this. Of a baffle, it has wide and smooth response. But horn loaded on a Synergy Horn, it's frequency response is atrocious. This is because it's QES is way too high for a horn.
 
Good comments.

Not sure if there would be any advantages. I'm curious for "home use" if a single TC9, TC7, SB65 with no port cut off, would you gain the high frequency response of the mid?

I've not seen much information about port/ hole size or hole placement disrupting the horn performance. Bill reported disappointment about the corner slot hole placement. I saw some interesting threads with multi holes and thin slot ideas.

Currently in HR I use the hole size and port length to tune the HF roll off of the mid. If there's other links / info please share, thanks
 
Bill reported disappointment about the corner slot hole placement....

I think that disappointment was because I lost track of the necessity to keep the ports close enough together. Pushing the ports into the corners in that rectangular horn pushed them too far apart and it showed in the polar measurements.

But just on theoretical grounds, I do like the idea of minimizing the number of ports (and midrange drivers) to the amount that match the capabilities of the rest of the drivers. Prioritizing lower diffraction over higher SPL capability -- even the saled SmallSyns using Linkwitz transform to get decent bass can play WAY louder (and clean enough) than I need for music/non-HT use. Having the thin cabinets up against the back wall helps that quite a bit.
 
...I've not seen much information about port/ hole size or hole placement disrupting the horn performance. Bill reported disappointment about the corner slot hole placement. I saw some interesting threads with multi holes and thin slot ideas.

Judging from a lack of responses (other than the proximity of ports that Bill made, just above), I believe that it would be useful to have links to the threads/posts where port size, position, and their effects on performance stated. Questions still arise on the following:

1) How much area to use for off-axis ports? What happens when too small or too large?

2) Where to place the ports, and where not to place them across a horn wall? Can they be placed all the way across the horn wall? Or are there issues?

3) Does compression ratio affect the performance, and how does it affect it?

4) Can off-axis ports be used on non-flat areas of the horn?

5) What about reflex vents, like Danley uses in their horns--can they be used inside of the horn, and where should they be placed? What are their effects on performance?

6) How about the length of the ports? Is there a consensus on whether or not to use non-minimized port lengths on off-axis ports.

7) Should the ports be round, elliptical, or slotted? What are the effects? What are the effects of multiple small through holes (i.e., a "grating") on top of a larger through port?

All of these questions are relevant to "Small Syns" (MEHs). I believe that I've got a few anecdotal answers and one or two established answers to some of these questions, such as recommended port area, port placement along the length of the horn (i.e., low-pass cut-off frequency), and compression ratio (Olson, Beranek). But the other questions seem to remain open/unanswered.
 
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