A Better Sub Option - OB H-Frame Build

[Poultrygeist]

http://gallery.audioreview.com/data/audio//500/P6030007.JPG

[Feanor]

Poultry, where can I read up about the theory of these dipolar subs? What are their characteristics? What are their limitations?

[Poultrygeist]

I have never been a sub fan ( except in HT ) as I find them too plodding and slow to produce musical bass. Getting them to seamlessly integrate into a system has been painful at best and in my case no amount of fiddling ever got it right. Friend, I'm here to tell you these H-Frames get it right!

The picture above shows two blue-gray H-Frames paired with some Frugal Horn Mk3. The combination works great together as the horns no longer require corner loading due to the bass augmentation of the H-Frames.

The H-Frame is nothing more than an open-ended box of 3/4 plywood with another piece of plywood for the speaker mount located exactly in the center of the box. I used the internal dimensions of 17X17X17 but others have made them slightly smaller at 16X16X16. The H-Frames use high Qt. Eminence Alpha 15A bass drivers which cost around $60 each from Parts Express. I routed the cut outs using the PE site dimensions but a jig saw will also work. The sides of the box are screwed and glued together using a small Kreg pocket hole jig kit. Check out the Youtube video of the Kreg pocket hole jig as it's invaluable at joining wood together at right angles.

The plywood I used cost around $26 for a 4X8 ft sheet at Home Depot and they cut all the pieces free. I used Rat Shack hook up wire to connect the speaker terminal to binding posts mounted on a small block of wood at the rear. ( I'll post more pictures )

The H-Frames are driven by two Parts Express Dayton APA150 integrated amps ( pictured on floor )which can be used as stereo, mono, or sub amps as they have built in cross-over controls. They usually sell for $130 each but sometimes go on sale for $99. The APA150 is the same as the Emotiva BPA-1 which Emotiva no longer sells since PE now carries them. The manual is a free download on the Emotiva site and explains how two of these amps can be daisy chained for 150 WPC. One amp though can drive two H-Frames. Each amp has one set of inputs and one set of outputs so mon-blocking them is easy.

If you don't have a preamp with two ouputs there are still many options to bi-amp this system. You can use the analog outs of a CDP to feed the Daytons while simultaneously using a digital output to feed your regular amp through an outboard DAC. Another option is to split the signal output of a CDP using Y cables to feed your regular amp and the Dayton H-Frame amps ( as they have volume controls ). You can use the same Y cables as well to split a single preamp output which may reduce gain.

I know I haven't covered everything so please feel free to ask questions no matter how basic.

[Poultrygeist]

Bill,

Martin J. King is the guru of this design.

Quarter Wavelength Loudspeaker Design (http://www.quarter-wave.com/)

[Poultrygeist]

Rear view of H-Frames with Tang Band OB's resting on tophttp://gallery.audioreview.com/data/audio//500/P6280002.JPG

[Feanor]

Bill,

Martin J. King is the guru of this design.

Quarter Wavelength Loudspeaker Design (http://www.quarter-wave.com/)
That looks interesting, thanks.

I'll perhaps start with the OB vs. H vs. U discussion ... HERE (http://www.quarter-wave.com/OBs/U_and_H_Frames.pdf).

[Poultrygeist]

Read everything on his site as it's like the Holy Grail of TL and OB.

On another forum I was honored that Mr. King actually wanted to use my Tang Bands/H-Frames pics for his site.

Bill, you should build a pair of H-Frames for your panels.

[Poultrygeist]

Here's an example of H-Frames from youtube. I'm so struck with the H-frame sound I'm building a second set. The audio here as usual is not very good.

Dipole Fostex Front Horn - YouTube (http://www.youtube.com/watch?v=eX6VlboT-sI&feature=related)

[Poultrygeist]

Another H-Frame OB bass driver in action

Dipole H-Frame woofer - YouTube (http://www.youtube.com/watch?v=GOD2kmrPlKA)

[E-Stat]

I'll perhaps start with the OB vs. H vs. U discussion ...
I noticed that Siggy abandoned the H frame approach with his current Orions. Still open baffle, but optimized to reduce vibration. Look here (http://www.linkwitzlab.com/orion-rev4.htm).

rw

[Feanor]

I noticed that Siggy abandoned the H frame approach with his current Orions. Still open baffle, but optimized to reduce vibration. Look here (http://www.linkwitzlab.com/orion-rev4.htm).

rw
I've never really understood the reason for the dipole Orions when there are various simpler, cheaper, and likely better, planars available on the market.

[E-Stat]

I've never really understood the reason for the dipole Orions when there are various simpler, cheaper, and likely better, planars available on the market.
He says tall line sources distort image height with close miked recordings. Yep, that's true. On the other hand, I've never heard waist high speakers reproduce the natural height of musical venues I attend - regardless of the quality of the recording. ;)

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rw

[Feanor]

He says tall line sources distort image height with close miked recordings. Yep, that's true. On the other hand, I've never heard waist high speakers reproduce the natural height of musical venues I attend - regardless of the quality of the recording. ;)

rw
Yeah, well maybe or maybe not. Horizontal placement in a stereo image comes from the L & R separation; there is no vertical, (high & low), separation whether the drivers are line or point. I know I sometimes perceive height but, (I suggest), it's a pycho-accoustic illusion cause by distance clues such as loudness and timbre variations, (softer instruments/voices with less high freq. content are perceived to be farther away and also higher up).

Or perhaps it has to do with the dipole effect in some way I'm missing. But the dipole effect -- though very agreeable -- is itself an artifact and doesn't present true hall ambiance in anyway that's true or accurate.

[E-Stat]

I know I sometimes perceive height but, (I suggest), it's a pycho-accoustic illusion cause by distance clues such as loudness and timbre variations, (softer instruments/voices with less high freq. content are perceived to be farther away and also higher up).
This is where individual preferences and sensitivities are found. I am most acutely aware of "listening down" to many systems which cannot convey a realistic image height to these ears. This is true whether I am listening to music or watching a movie.


Or perhaps it has to do with the dipole effect in some way I'm missing. But the dipole effect -- though very agreeable -- is itself an artifact and doesn't present true hall ambiance in anyway that's true or accurate.
The ability to replicate accurate image height is independent of whether or not the speakers are dipolar. Harry's current Scaenas - like the Nola Grand References they replaced - are monopoles. The Nolas are arrayed as a large MTM while the Scaenas are line sources. Can either of those different speaker systems convey a natural image size to these ears? Does a bear, er sit in the woods? As for your assertion that dipolar radiation is inherently an "artifact", I don't know of many acoustic instruments that radiate only in a 2 pi space as do monopole box speakers.

Business travel recently took me to Salt Lake City where I was able to attend the Mormon Tabernacle Choir practice session in the huge conference center. It is not at all easy to replicate the scale of a 350 voice choir accompanied by a magnificent pipe organ with multiple thirty two foot stops. And yet, it isn't determined by decibel level alone. From my spot about twenty rows from the front, the loudest level I measured - which lasted for just a second - at the end of a piece that rose to crescendo with both voice and organ was only 95 db. Most peak levels rarely exceeded the mid 80s. Even when you could feel the enormous weight of 16 hz bass at the foundation of the music. I had a big grin on my face. :)

rw

[Poultrygeist]

I'll soon be building a second set of H-Frames so I can hear how they perform stacked two high.

[Feanor]

...
Business travel recently took me to Salt Lake City where I was able to attend the Mormon Tabernacle Choir practice session in the huge conference center. It is not at all easy to replicate the scale of a 350 voice choir accompanied by a magnificent pipe organ with multiple thirty two foot stops. And yet, it isn't determined by decibel level alone. From my spot about twenty rows from the front, the loudest level I measured - which lasted for just a second - at the end of a piece that rose to crescendo with both voice and organ was only 95 db. Most peak levels rarely exceeded the mid 80s. Even when you could feel the enormous weight of 16 hz bass at the foundation of the music. I had a big grin on my face. :)

rw
I attended a performance in the Tabernacle in ~1994; it was a small-scale performance but very impressive just the same.

You aren't really going reproduce that sound with any sort of home system, but I'd guess you'll come closest with a high quality multi-channel setup -- like HP's maybe. Multi-channel, done right, is the way to come closest to authentic in-hall sound. You won't with stereo, mono or dipole.

[E-Stat]

I attended a performance in the Tabernacle in ~1994...but I'd guess you'll come closest with a high quality multi-channel setup -- like HP's maybe. Multi-channel, done right, is the way to come closest to authentic in-hall sound. You won't with stereo, mono or dipole.
The two musical venues for MOTAB provide an interesting comparison with two channel and multi-channel. Most likely, you heard them in the original "loaf of French bread" shaped hall. That is a relatively intimate setting with phenomenal acoustics with all its rounded corners. Even sitting at the rear in the balcony affords a rather spectacular "surround effect". Spoken word can clearly be heard at great distances in that space. Last week was their bi-annual meeting where they performed in the 21,000 seat conference center instead - large enough to put a 747 inside. From the centered position where I sat, there was little in the way of hall reflections coming from the side walls since they were at great distance. It was more like a larger stereo image. Different - but still very impressive sounding. :)

rw

[gilchristobin]

Martin J. King is the guru of this design.

[rightaway]

i would like to try to build a pair of speakers like the one in the video, tweeter,mid and sub, does any make a kit or do you have to buy the for $1500 a pair?

[Poultrygeist]

I just added a Fostex super tweeter ( with built in filter ) to the Tang Band/H-Frames which is connected directly to the Tang Band terminals. I now have a 3 way without a crossover.

[Poultrygeist]

There are very few kits for OB's as there's little commercial interest due to low profit margins for such a simple design.

[BoJonJovi]

OK poultrygeist. It has been ages since I last posted. I kinda fell off the map after asking you for a considerable amount of help with my build based on your recommendations.
Anyway many moons ago I ordered the Eminence Betas and Alphas. then I got a way behind in my remodeling business and they just sat. Well any way I do not have a to do list, I have a get done list of projects started and never completed. I finally got this one done.
I took a slightly different route. I went to a concrete supply house and bought an 18" inch round concrete form tube. It is made of heavy cardboard. I made a plywood insert that I pushed in the middle of the tube then mounted my Alpha 15-A in that. I then cut a circle in a large plywood panel and pushed the whole thing into the panel. I then glued and screwed each to the other to make a somewhat uniform unit. I then mounted my Betas and tweet into the larger board.
I wired the Betas and Alphas in parallel to give me 4 ohm and hooked them to my class-d audio amp. I then bought a small Topping 30 wpc amp to drive the tweets.
Long story short. They sound awesome. Way beyond my expectation. You had told me they would replace my Maggies. There is no comparison. They are much better in clarity, dispersion, and expansiveness. I love to be enveloped in the sound. Further they are very clear and enjoyable at low volumes.
I love to have a glass of wine and close my eyes. I swear I can reach out and touch the instruments. Because they are so much clearer and defined it is easy to become even more critical. I also long for some Tangs but I am not sure I can justify the extra cost.

Anyway, thank you so very much.
I am lovin it!

[BoJonJovi]

This is my open baffle build thanks to poultrygeist. I love the envelope of sound. It is like being underwater only under sound. I am going under for the third time and enjoy drowning in a sea of sound.
I used a concrete form tube from a local concrete supplier for the sub. I am not sure how it would compare to the Martin King H-Frame but the volume, area, and length are all similar. Since it was much easier than building a box I thought it would simplify and speed up the project. I am ecstatic about the results.

[StevenSurprenant]

That's very interesting... How low does it go? The reason I ask is that I'd like to add a little lower bass to my system which is rated down to about 55Hz. 30Hz would be wonderful. I've heard bass using dipole and it sounded... what's the word?... purer (whatever that means). What are you using for a crossover?