Hestia Hybrid

[fernandov]

I have been building open baffle speakers for several years and have been looking to integrate a few new ideas. The Hestia Hybrid uses a single dipole point source combined with a larger monopole up firing driver that is mounted in a tuned and damped slot loaded enclosure. Both drivers operate without a crossover and should not require additional signal processing.

This is intended as an alternative to studio monitors, combining some of the benefits of dipolar / full range loudspeakers with the manageable size and stand-alone characteristics of traditional bookshelf speakers.



Drivers:

Primary – Jordan Eikona II / 100mm aluminum cone (other 3-5” full range drivers may be substituted, and attenuated as needed)

Secondary – Peerless 830869 / 8” Nomex cone

Cabinet:

PE/Denovo Audio Knock-Down MDF 0.67 cu. ft. Speaker Cabinet (modified)

Here’s what I’m hoping to test:

Both drivers operate full range electrically and avoid the monopole to dipole null that would occur around a fixed crossover point if a crossover were used. This helps maintain a symmetrical figure eight pattern associated with classic dipolar dispersion. (Eval 1).

The right angle driver coupling helps reduce frequency modulation distortion (Eval 2) and is a preferred method for combining two full range drivers and minimize lobing.

A tuned and heavily damped slotted enclosure provides low frequency reinforcement that sums constructively with the dipole driver. (Eval 3). The tuning frequency is centered at the -10dB roll off point of the dipole driver for cohesive (non- destructive) low frequency support.

An adjustable driver mount is used to better align the acoustic centers of both drivers and optimize phase coherence (Eval 4) at the listening position.

The adjustable dipole mount provides micro toe adjustments as well as a way to help manage floor and ceiling reflections (Eval 5).

[andykriech]

Wow, very interesting and a great use of a bath grab bar!
ak

[fernandov]

Wow, very interesting and a great use of a bath grab bar!
ak

LOL, good eye! The steel bars hold three 5 inch carriage bolts which allow for forward adjustment of the dipole's acoustic center, without blocking the drivers rear wave. It also lets me have multiple baffles that can be swapped easily when testing new drivers. The thumb nuts let you dial-in vertical and horizontal pitch adjustments as well.

Here's a close-up shot.


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[PWR RYD]

I like a lot about your concept except for the lack of any crossover, passive or active. The system will be extremely SPL limited due to the Jordans running completely fullrange with no baffle.

[fernandov]

I like a lot about your concept except for the lack of any crossover, passive or active. The system will be extremely SPL limited due to the Jordans running completely fullrange with no baffle.

The Jordans have to be attenuated with an inline resistor to approximate the output level of the slot. So even though there is no highpass filter, they are operating around 10 dB lower than the Peerless. Due to significant dipole cancellation, they essentially function as a mid/tweeter in this design. Even though IM distortion is typical for that of a full range driver, I'm hoping the reduced output will help in this case. Plan B would involve a high pass filter if necessary. Will be interesting to see.

[ani_101]

looks interesting. The tests should be interesting too.

[aditya1384]

The Jordans have to be attenuated with an inline resistor to approximate the output level of the slot. So even though there is no highpass filter, they are operating around 10 dB lower than the Peerless. Due to significant dipole cancellation, they essentially function as a mid/tweeter in this design. Even though IM distortion is typical for that of a full range driver, I'm hoping the reduced output will help in this case. Plan B would involve a high pass filter if necessary. Will be interesting to see.

Very curious to know about further developments Sent from my GM1911 using Tapatalk

[fernandov]

I experimented with different value first order high pass filters on the Jordan, and settled on a single value capacitor along with a quality bypass cap, and revised the resistor value on the Peerless to match. Also, the resistor was placed ahead of the caps in the final design, which presented a friendlier load with the caps in place. I'm not convinced the high pass was absolutely necessary at my listening levels, but agree the Jordan can be played louder if needed. I listen to the hybrids every day, and have found few speakers I prefer all things considered.