[WC]

What sort of amp are you using to drive these?

I have a set of the Eikona II's that I was putting in a small TL cabinet, but it would be interesting to try this out. Just need the two peerless drivers an a bit of MDF for the base cabinet. Interested to hear how you like them.

[matevana]

What sort of amp are you using to drive these?   Interested to hear how you like them.

I use a Digital Amplifier Company Stereo Maraschino amplifier. It's a class-D amp with just 2 balanced inputs, a passive volume pot, and speaker outputs.   

I have used the Jordans in several configurations and have always liked them. After several years I feel like I know them well and can assess the pros and cons of enclosure changes effectively. I plan to do a lot of listening this weekend and then write some impressions.   

[matevana]

Listening Impressions, 5/3/2020

Room: 14’ x 19’ with 8’ ceilings / average brightness / no room treatments

Equipment:

Speakers: Hestia Hybrid dual full range – open baffle / tuned slot
Source: Sony NW-ZX300 Digital Audio Player
Amplifier: Digital Amplifier Company Stereo Maraschino / 60v DIY power supply
Interconnect: LQi Cables, Balanced 4.4mm TRRRS Sony connector to Dual XLR / Silver coated copper
Speaker Wire: Western Electric cloth covered copper, 14 AWG, circa 1950, 8 ft. sections

Evaluation Material:

Iiro Rantala & Ulf Wakenius, Good Stuff, 2017, 96kHz FLAC
Deep Purple, Perfect Strangers, 1984. 44.1kHz AIFF
Gyorgy Cziffra, Liszt: Hungarian Rhapsodies, 1975, 44.1kHz AIFF
Nicki Parrott, Stompin’ at the Savoy, 2018, 44.1kHz FLAC
Denis Matsuev, Shastakovich: Piono Concerto No. 1, 44.1kHz FLAC

Technical Observations:

These are the most phase coherent speakers I have owned. Even though they use two distinctly different drivers they seem to mesh seamlessly. The sound arrives at the listening position completely in-tact, regardless of the complexity of the musical track. This was not the case when the same drivers were mounted on a single flat panel. Also interesting is the much wider sweet spot compared to the prior iteration.

This improvement is likely a result of three things. (1) Combining two drivers on separate planes, while maintaining the alignment of their acoustic centers; <the combination of direct sound from the dipole driver along with the more omnidirectional radiation of the up-firing driver seem to trick the brain into hearing a single point source throughout the full frequency response>; (2) Crossover-less systems do not add additional phase shift or time anomalies; (3) the ability to mechanically adjust the arrival time of the higher (faster moving) frequencies at the listener’s position.

What surprised me most was the significance of the Peerless driver in this design. I originally envisioned the up-firing driver to be more supportive in nature as it was in the flat panel design. In reality though, it is a major contributor to the Hybrid’s overall sound.

Contrary to the above, it seems that the Hybrid’s character is more reminiscent of the Jordan Eikona. It’s interesting that when you disconnect the Peerless driver, the image completely collapses. The Jordan in its minimalist baffle is incapable of supporting full range listening to anything other than the near field, but it helps to set the table for the Hybrid’s overall character. I am very familiar with the Jordan in a large baffle, as they (along with an active sub) have been my main speakers for the past few years. The illusion created by both drivers in tandem has me believing that I am listening to a single much larger driver, without sacrificing any of the Jordan’s smooth sound and superior dispersion. .

I mentioned during the construction stage that I expected to have to attenuate the Jordan driver after factoring-in dipole cancellation in order to match the slot’s output level. 9.5 ohms of resistance ended up being the perfect amount. This was achieved by combining a 27 ohm and 15 ohm Mundorf M-Resist resistor in parallel. The parallel resistance also allowed for more power handling. Substituting dipole drivers would require an adjustment to the amount of added resistance.     

The slot does an excellent job of adding low frequency weight to the dipole driver in a manner that was never possible with my flat panels + subwoofer. I am particularly referring to bass quality over quantity. Perhaps this is a function of the better electronics associated with a main amplifier compared to that of a plate amplifier, the fact that the input signal is not split, or the slot’s proximity to the other drivers, but the level of coherency is a marked improvement. The amount of low frequency energy is similar to that of like-sized bookshelf speaker. It would be an easy task to integrate a sub below 60Hz, but for now I am enjoying them solo.

I should mention that I made a design change regarding fill and the resulting bass quality. I have used Acousta-stuff in prior sealed cabinets. However the bass in the finished design sounded more constrained than what I was hearing during the initial construction without any fill. There may have been too much absorption taking place prior to reaching the slot. Instead, I lined each adjacent interior wall with carpet tile and scrapped the Acousta-stuff entirely. This eliminated the constrained character and changed the bass presentation to a more natural wet/dry balance.

So how do they sound?... really.

Good.  Really good in fact. I usually start to notice shortcomings once the newness wares off.  Maybe that’s why I’m not married.  But so far I am thoroughly enjoying them.

Personally I am more sensitive to phase shift than other design challenges. This was a major consideration in the Hybrid’s design. I am very pleased with the outcome. This may explain why I am a fan of well-designed full range drivers and no crossover. Their primary downside (higher intermodulation distortion) is offset here by a properly integrated second driver allowing for higher system SPLs, with each driver doing less of the work. The Jordan’s 4” cone is also less prone to beaming than larger full range drivers.

The timbre produced by the Jordan/Peerless mashup is very realistic. The sparkle around a piano’s highest octave is excellent, as is the tone of brass instruments. I attribute this to the Jordan’s metal cone and proprietary phase plug design. I have not detected any noticeable lobing in the design. The Peerless brings warmth and weight to the party. Although it is designed primarily as a woofer, it has a fairly smooth natural roll-off at higher frequencies and is not shamed by the lack of a crossover, especially in an up-firing alignment. The Jordan, while being a very capable driver, is essentially a 4“ speaker and cannot be expected to move the amount of air necessary for the lowest registers in an open baffle setting. Together they not only mitigate each other’s shortcomings, but create a synergy where tone is concerned. 

As mentioned earlier, the sweet spot has grown significantly compared to the same drivers being mounted in a single flat panel. This has not impacted imaging adversely. The spatial location of musicians are well preserved, and depth perception seems to have increased over prior iterations. The width of the soundstage in my room is consistent with prior designs, and was not compromised by the up-firing driver.

If I had to find fault with the Hybrids it would involve low volume listening. This is my first slot loaded design and it may be a quality of the slot itself, compared to other types of vented designs. I have noticed that slots seem to require a decent amount of air to pressurize the room. They really excel at average listening levels and beyond, but there is a notable drop-off of low frequency energy at reduced volume. I should mention that my amplifier does not have a loudness function or midnight mode, and perhaps this might help. For a number of reasons, I do not suggest substituting a conventional port tube in lieu of the slot with this particular design.

Several people contacted me about the high cost of the Jordan Eikona 2, and asked if I could recommend a lower cost alternative that would be successful in this design. I have no reason to believe that the Hestia Hybrid would not excel with a variety of full range drivers. Due to the concern over beaming, I would suggest keeping the driver as close to 4” as possible. This will also help preserve the off-axis response. The dipole’s total Q (Qts) is less of a factor here, as this driver functions primarily as a mid/tweeter due its small baffle size. 

All things considered, I would definitely recommend this design to anyone interested in exploring open baffle speakers, without the added complexity of having multiple amps, digital signal processing and crossovers.   

[WC]

Thanks for the detailed write up. I am interested in trying this in the future. I may even have enough 3/4” MDF to build the boxes.

[matevana]

An Interesting Variation




Flipping the larger driver so it fires into the cabinet makes for a thought provoking variation on the design. A little less low frequency energy emerges from the slot, but the mid frequencies radiate out into the room more prominently. You can compare this to the directionality of a guitar string as opposed to a typical speaker baffle.  You must remember to invert the polarity of the larger driver to maintain a positive phase relationship between the slot and the dipole driver.

I only tried this with one speaker so I can’t comment on how accurately these might image, but I would expect them to throw a wide (almost exaggerated) sound stage. In my situation I plan to listen without subs, so I did not fully explore this variation.   

[Madcapwoodwright]

Matevana,
Hi, I was referred here from a post of mine over on tech/talk.

I have questions.

You need to know I am just beginning my audio adventure. As a woodworker, I have been seeking something different to build, and as a music junkie, this fits a lot of my needs.
Hybrid open baffle, and omission of crossover design/build, chief among them.
I wonder if I might pick your brain a bit?
I have some GRS BOFU clones. I know nothing of their specs, and even though I know the specs are available, I have no idea what I'm reading, so you need to read this as though a child were writing it.

My main question is, do you suppose I could realize similar results using the BOFU clones, and another, preferably inexpensive driver?  I.E. for the 4"-6" full range on top?

The slotted enclosure is 12"x12"?

How tall is the slot? Looks to be about an inch?

Anything you would change or add/subtract in the design or fabrication
of the enclosure?

Regarding the D-class amp , is this off the shelf?
Would one of the mini amps (d-t class) power these sufficiently enough using a phone streaming Spotify as source?

Sorry for the artillery barrage of questions. I'm new, and as I mentioned, just joined up to address you about these speakers, though I'm totally sticking around. (Verification gauntlet appreciated but tiresome.)
Lol
Anyway, thanks in advance, these look pretty stellar. I hope I can get close to the quality sound you describe, if even on the very cheap!

[Madcapwoodwright]

One more request....lol....sorry.

Any chance of getting dimensions? True box size, slot size, size of interior baffle and it's distance from the back wall of the interior?

EDIT to add (sorry)
The raw size of the Jordan's baffle prior to cutting the driver's radius as well as the handle bar sizing/source would be pretty important I think .
Looks like I'm going to give these a try

[matevana]

Matevana,

I have questions.


My main question is, do you suppose I could realize similar results using the BOFU clones, and another, preferably inexpensive driver?  I.E. for the 4"-6" full range on top?

The slotted enclosure is 12"x12"?

How tall is the slot? Looks to be about an inch?

Anything you would change or add/subtract in the design or fabrication
of the enclosure?

Regarding the D-class amp , is this off the shelf?
Would one of the mini amps (d-t class) power these sufficiently enough using a phone streaming Spotify as source?

Sorry for the artillery barrage of questions. I'm new, and as I mentioned, just joined up to address you about these speakers, though I'm totally sticking around. (Verification gauntlet appreciated but tiresome.)
Lol
Anyway, thanks in advance, these look pretty stellar. I hope I can get close to the quality sound you describe, if even on the very cheap!

Hi and sorry for my delayed response. I'm usually pretty prompt.  

Would you be able to provide the part number for the GRS woofer that you already have? I'm sure we can find an inexpensive small full range driver that will work well in combination.

The enclosure's outside dimensions are 12" x 12" x 12" and the walls are all 3/4" MDF.  That makes the internal volume right around .7 cubic feet.

The slot height is 3/4" and it's depth is 8".  We may have to change the dimensions slightly to tune for the GRS woofer. The slot height and depth determines the cabinet's tuning, similar to a cylindrical port tube in a typical vented speaker.

If you are planning to have the speakers sit on a shelf or table, I would leave the slot as-is. If you are planning to use stands, I would be tempted to move the slot's mouth to the top of the front enclosure wall, leaving the woofer where it is. You can do this by orienting the slot so it runs vertically along the front panel. I can provide a drawing if this interests you.

My particular amplifier is made by a company called Digital Amplifier Company, but any decent stereo amplifier should work fine. The amp should be able to drive a 4 ohm load, which should be no problem for most solid-state amplifiers and even some tube amplifiers.

The baffle that supports the full range driver will be the same width as the widest dimension of that driver. It's as minimal as possible in this design. The center of my particular driver is suspended 7" above the top of the enclosure. 

The grab bar is made by Kohler and it is a 12" model with exposed screws on the mounting flange (you want this). Most grab bars have a more finished sliding bezel that hides the screw holes which will not work in this application. It measures around 15" from the furthest point of each mount. It is stainless and the tube diameter is 1 1/4". 

Please let me know which GRS model you have and I can make some recommendations.

[jonasz]

An Interesting Variation




Flipping the larger driver so it fires into the cabinet makes for a thought provoking variation on the design. A little less low frequency energy emerges from the slot, but the mid frequencies radiate out into the room more prominently.

Hi Matevana! Why is there less low frequncy with the inverted orientation? Or do you mean less in relation to the elevated mids?

[matevana]

Hi Matevana! Why is there less low frequncy with the inverted orientation? Or do you mean less in relation to the elevated mids?

That’s a great question Jonas.
 
Here’s some speculation on my part, which may just come down to physics (efficiencies and losses).

The Fb of the box (frequency at which the slot is tuned) relies on three factors, two of which are fixed in either case (the length/cross sectional area of slot and the speed of sound in air). That leaves the third factor which will vary depending on the orientation of the driver.

Factor #3 is the internal volume of the enclosure, which was previously measured taking into consideration the driver’s displacement. By inverting the driver, you are effectively increasing the enclosure’s volume and a loss of optimization will result based on the existing tuning. Since the enclosure is small to begin with, this change in apparent volume is not insignificant and measurable losses will occur compared to a fully optimized system. 
 
That being said, if the initial parameters had included the increased volume from inverse mounting, and the slot dimensions were altered accordingly, there should be little difference.   

[jonasz]

That’s a great question Jonas.
 
Here’s some speculation on my part, which may just come down to physics (efficiencies and losses).

The Fb of the box (frequency at which the slot is tuned) relies on three factors, two of which are fixed in either case (the length/cross sectional area of slot and the speed of sound in air). That leaves the third factor which will vary depending on the orientation of the driver.

Factor #3 is the internal volume of the enclosure, which was previously measured taking into consideration the driver’s displacement. By inverting the driver, you are effectively increasing the enclosure’s volume and a loss of optimization will result based on the existing tuning. Since the enclosure is small to begin with, this change in apparent volume is not insignificant and measurable losses will occur compared to a fully optimized system. 
 
That being said, if the initial parameters had included the increased volume from inverse mounting, and the slot dimensions were altered accordingly, there should be little difference.

Thanks for a great reply. That was also the only explanation I could think of, just wanted to check that I haven't missed any fundamental knowledge! 

Btw, love your "simple" but ingenious designs!

[Madcapwoodwright]

Matevana has a wonderful way of explaining concepts to a fledgling like me.

Great info in his builds. Always take something from his posts.

[Ian J]

Hi Matevana,
interesting project! Can I ask a question?
You say the Jordan's output will be down by ~10db at 70Hz, is this from measurement or calculation?
Thanks for sharing,
Ian

[matevana]

Hi Ian,

When I measured the Jordans for the Univesals' project ( https://www.audiocircle.com/index.php?topic=154866.0 ) there was a 10dB difference at 70 Hz in open air.  The baffle used in the Hybrid project won't prevent much cancellation so it will likely be about the same; in this design the baffle mostly supports the dipole driver and provides some forward reflection for the upfiring driver. When my university eventually reopens, I will have better access to a measurement room.

[sjhomey]

Hi Matevana
I have been contentedly listening to the Hestia Vs for several years. Lately though my audio buddies have been building this and building that, so here I am. I would like to build the hybrids unless you have something else in development. At this point I am just gathering parts and have a few questions.
I bought a pair of Mark Audio Alpair 11 MS Gen 2 full rangers and have been looking for woofers. The Peerless have been discontinued and while I still see a few on Ebay I have been looking around. The Dayton Audio RS225-8 8" caught my eye. I am not sure of all the parameters you are using to pick the woofer, but am wondering if these would be good candidates?
Secondly, I am wondering about the enclosure size. I believe you are using the Denovo flat pack. It seems a little small compared to PE's recommendations for both the Dayton and the Peerless in an unsealed application. Does the enclosure size make a big difference with the hybrids?
Thank you as always for your advice.

[matevana]

Hey SJHomey,

Placing the Peerless in a smaller than optimal enclosure provided the necessary upper bass hump I needed to create a flat-ish response with the Jordans. It was a balancing act between the FR drivers roll-off, the increased sensitivity of the woofer (compared to the FR driver) coupled with the above mentioned hump, and the low output from the port. When I was experimenting with the hybrids it became clear that all of these things were interrelated, maybe more so than in a conventionally aligned speaker with all the drivers on the same plane. Updating one typically required adjusting the others.

A few things to keep in mind.

The Jordan is essentially a 4” driver while the Alpair 11’s are closer to 6.5”. The larger Alpair with an appropriately sized baffle/mount will have a different roll-off. In this case you likely don’t want the same upper bass hump I was seeking, or you might want it centered at a lower frequency. If the Alpair is more sensitive, you will also want to select a more efficient woofer. You will need the extra headroom to address the Alpair’s LF cancellation.
   
I’m sure you saw that the Denovo flat pack in question is a sealed box. If you choose to start with that, you will need to modify the box if you are mimicking the Hybrid’s slotted design.

I have experimented with a few newer designs, none of which are better than the Hybrids.  If I were to redo the Hybrids today, I might move the port from the bottom to the top (also front facing). The port’s closer proximity seems to couple even better when all three sound waves essentially originate from the same plane. (I’m including the woofer’s reflected output against the FR driver’s baffle in the “same plane” reference).
Hope that helps and feel free to PM as needed.

[szach00]

Hello Matevana!
I really like the simplicity of this design. Any comparisions to LX521?

[motosapien]

I built the upper part Mcm/Vifa some years back and brought them down from the attack a couple days ago.  Going to run them along with my Overnight Sensations for now.  The Hestias bring in some pleasing midrange while the modest but musical base from the OS's complete the party.  Was considering adding a Klipsch 10" powered SW at some point.  It would be placed on the floor between the Hestias.  This is only for music ( not John Wick ).  the hestias will be about 12 feet apart.  Do you think the SW would integrate o.k. this way?  I will run all this at modest volumes.

[matevana]

Hi Motosapien,

Just so people don't get confused, I believe you are asking about the original Hestia design? (you are posting in the Hybrid thread currently).  If so, the originals are fairly easy to integrate with most subs and what you are asking about should be fine. The Hybrids require a little more care when choosing a sub.

[matevana]

Hello Matevana!
I really like the simplicity of this design. Any comparisions to LX521?

Hi szach00,

Unfortunately I only got to hear the LX521's at a show, in a really poor room. I have much more quality ear-time with the Orions, which I thought were great.

The Hybrids can offer sound staging similar to some Linkwitz designs but have a scaled down presentation, more like that of a classic British studio monitor.  They are well balanced for their short stature, but can't come close to the almost perfect octave to octave balance and strong dynamics of the LX521, or even the Orion for that matter.