Yup, Perry's work is interresting cause using an hybrid approach DSP to EQ beyond the usual size of drivers usually used in dipoles (i.e. 6" + 3" +1" to manage the first null of the drivers) AND coax + back radiation behavior of the tweeter made by another one at the back, here there is not the dipole cancelation.
Think it is desaerving its own thread cause Perry Marshall is sharing his design for the community.
Think it is desaerving its own thread cause Perry Marshall is sharing his design for the community.
The Flanagangsters
A Heretical Reflex+Open Baffle Hybrid
Constant Directivity, 96dB SPL, 300 Watts, 35Hz-20KHz
Crafted from Live Edge Wood
A Heretical Reflex+Open Baffle Hybrid
Constant Directivity, 96dB SPL, 300 Watts, 35Hz-20KHz
Crafted from Live Edge Wood
This design is Bass Reflex below 100Hz and Open Baffle above 100Hz, using one 12” woofer as a Point Source bass and the other as a Dipole Midrange. It combines the stage, imaging and open sound of Open Baffle with the bass and power output of a reflex.
Is this heresy? To a Dipole purist, undoubtedly so. But it delivers a huge un-boxy stereo image with the bass punch of a traditional ported design.
I’m proud of the polar response spectrum, it exhibits excellent Constant Directivity from 150Hz to 20KHz; it has -6dB points at about 45 degrees off axis, very consistently from 200Hz on up. Notice that even at 20KHz the pattern doesn't narrow much; this is because of the waveguide:
Frequency response at 0, 15, 30, 45, 60, 75 and 90 degrees off axis:
1/6 octave curve at 0 15 30 45 60 75 degrees:
The above measurement doesn’t capture the bass output of the port. Here is the measured response of the port + lower woofer.
I made these for my friend Jeremy Flanagan who loved the Bitches Brew Live Edge Dipoles but needed something much smaller and more economical. These deliver 80% of the performance for 20% of the cost. I wanted these to have the luxurious room-filling sound of Open Baffles but be capable of functioning as “party speakers” when called upon to do so.
The woofers are Dayton PA310s with 96dB SPL sensitivity and 3-inch voice coils. The lower woofer operates from 35Hz to 100Hz in a 40-liter reflex tuned to 42Hz. The upper woofer operates as a midrange from 100Hz to 2KHz in open baffle configuration.
Front tweeter: Audax TW034X0 34mm classic soft domes matched to Troels Graveson waveguides. (http://www.troelsgravesen.dk)
Rear tweeter: Peerless by Tymphany BC25SC08-04 1" Silk Dome Neodymium Tweeter
Crossover & Digital Signal Processing is handled by a MiniDSP 2x4HD with FIR time correction for linear phase. Configuration files: https://tinyurl.com/flanagangsterfiles
Some readers will be puzzled as to my unorthodox choice of using two identical 12” woofers, one as a midrange and the other for bass. I chose the Dayton PA310 for its high sensitivity and for its suitability for a DSP assisted reflex alignment in a small box, and because of its ultra-smooth midrange requiring very little help from the crossover.
The woofer has 5mm Xmax. This would fall far short of what’s necessary in an Open Baffle, but 5mm is plenty in a reflex, especially since the DSP filters out frequencies below 35Hz using a high-Q shelf filter. There is surprisingly little excursion at high volumes, and plus it doubles as an excellent midrange. And even with the small baffle size, the 12” dipole midrange effectively operates down to 100Hz.
This is the simulated reflex alignment of the woofer:
Below is the MiniDSP EQ correction curve for the woofer – notice the 9dB of bass boost at 40Hz which complements the above curve and renders the system flat to 35Hz:
Everyone is going to ask how the Dipole-Reflex hybrid sounds. Well, it sounds like normal low bass of course but with the very low crossover point of 100Hz to full dipole midrange, these sound more like dipoles than box speakers. They most emphatically do not sound “boxy,” and they have that huge, wide, lush imaging that Open Baffle designs are famous for.
NOTE: I used Precision Port 4” ports (large diameter ports are absolutely essential to prevent power compression). since there’s so little room on the inside of the smallish box, I had to cut the inside port flare with a jigsaw to leave enough space to install the bottom woofer.
The 100Hz crossover is a 6dB/octave "series" configuration instead of the conventional parallel. It has better impedance interactions. This curve shows the drive signal of the 12" midrange, which is much steeper below 100Hz than a standard parallel design would be:
The blue curve is the input signal to the whole system, and the green curve is the voltage measured at the terminals of the midrange. The impedance curve of the woofer is being turned "upside down" and being impressed on the midrange. This is reducing the output of the midrange at 20Hz and 60Hz, which is desirable. A standard parallel network would impress the midrange's impedance curve "right side up" on the response, which would be undesirable.
Schematic:
The LC circuit on the woofers is a 100Hz "series style" crossover. The capacitor on the TW034X0 is just for protection; the 10uF capacitor on the Peerless tweeter rolls it off at about 3K because I have concerns about driving it at lower frequencies. The rest of the crossover action is in the DSP.
Seth's CAD drawing:
My original sketch:
The tweeter, an Audax TW034X0, is one of the longest-in-production tweeters in existence. First introduced in the late 1970s, it’s used in the BBC LS5/9 and many other designs. It’s a famous mid-tweeter and when used conventionally (without waveguide) it’s a solid competent driver that gets slightly beamy in the high end, with 93dB sensitivity and response up to 16KHz.
However, when used with the Troels Graveson waveguide, sensitivity jumps to ~98dB and is no longer beamy in the top octave. The waveguide renders it a true Constant Directivity device. I use the DSP crossover to 1) establish a 2000Hz cutoff, 2) apply FIR filters for linear phase, and 3) extend the high end out to 20KHz.
The Audax 34mm tweeter has a round, soft, mellow sound with no listener fatigue whatsoever. It won’t appeal to people who prefer the etched hyper-detailed Titanium, Beryllium and Aluminum domes, but it certainly does not lack clarity. Especially with the waveguide, it has excellent dynamics. It is able to keep up with a high sensitivity 12” woofer, at least for aggressive domestic applications. (I wouldn't actually use these in a PA system, you'd probably blow out the tweeters.)
Open Baffle speakers that radiate from both sides via woofers but have tweeters only on the front sound “wrong” to my ears. I prefer true dipole behavior across the whole range, so I added a Peerless 1” dome tweeter with waveguide on the back. This is the frequency response on the back side, measured 45 degrees off axis:
NOTE: The tweeters are wired in parallel and the impedance dips to 2.6 ohms. Since sensitivity is around 98dB and since most music doesn't have large power requirements above 2KHz this won't be a problem for most amps. But this could be an issue for some people.
I feel these do successfully achieve their objective of: Delivering most of the power and impact of the Bitches Brew Dipoles, without the expensive high-end drivers and huge size.
The Constant Directivity sound pattern means every seat in the house is excellent. You can stand right next to the right speaker and hear the left across the room with an intact stereo image. The DSP assisted reflex means with a 200+ watt amp and 96dB, these will play at loud party levels without stress or fatigue. A few months ago, I hosted a listening party at a hotel for 40 people and they easily filled a medium sized hotel ballroom with sound.
At low frequencies the DSP delivers a 6-9dB boost between 35 and 55Hz, so at low frequencies the SPL is 87-90dB not 96dB. I greatly prefer that to a speaker that requires no bass boost but is 87dB across the whole spectrum. The 100Hz crossover means that the midrange 12” driver is never even going to move visibly so it has very low distortion regardless of what’s happening in the bass registers.
The cabinets were built by Seth Cothron (@studio38designs) and the 1.5” thick front baffles provide more than enough rigidity to get the job done.
Here are the DSP configuration files: https://tinyurl.com/flanagangsterfiles
These have great stereo imaging everywhere in the room, tremendous dynamic range, and achieve the advantages of Dipole + Reflex with almost none of the disadvantages. Distortion is incredibly low and they have a creamy midrange and very non-fatiguing high end that's easy on your ears.
I would love to hear from others who create Open Baffle hybrids with other enclosure types. Acoustic suspension is possible, perhaps even TLs and horns.
Attachments
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these wood planchas are definiyty good looking 
. Thanks for sharing.
I notice you use two famous tweeters that has good feedback from hifi enthusiasts. Often the tweeter is doing a lot in a speaker for the voicing. How would you definite the treble sound of this design in relation to the BB or the Cotton Wood, please ?
. Thanks for sharing.I notice you use two famous tweeters that has good feedback from hifi enthusiasts. Often the tweeter is doing a lot in a speaker for the voicing. How would you definite the treble sound of this design in relation to the BB or the Cotton Wood, please ?
@diyiggy The Cottonwood Dipoles (SB Acoustics Beryllium 29mm tweeter with waveguide) sound VERY different from the Audax 34mm domes. Even with all the DSP in the world there is no way to make them sound the same - even though you can make them have identical frequency response - and even though the polar pattern might be very similar.
The diaphragm materials have a signature sound that is utterly different.
The SB29Be has an incredibly transparent, fast, shimmering quality. Tom Perazella says they're the best tweeters he's ever heard and I tend to agree with him. Amazing imaging. Brisk and holographic.
The TW034X0 have a soft, laid back, round sound that is more "midrange-y." They are less detailed. Warm and buttery. They still have a good top octave. (But the DSP also provides a +6dB boost at 20K; without the DSP they would be even warmer and more midrange-ey.)
Like I said completely different.
There is no question for me that the SB tweeter is superior. It's also about 3X more expensive.
The titanium coax in the Bitches Brew sounds much more similar to the SB than the Audax.
The Beryllium coax in the Birch Dipoles sounds even more similar to the SB29Be in the Cottonwood Dipoles.
You can see all of those other designs at www.perrymarshall.com/speakers
If someone wants a more aggressive "etched" tweeter sound in the Flanagangsters, I would suggest using a Visaton waveguide WG148R and matching it to a 25mm dome tweeter of your choice. This option will also be less expensive as neither the Troels Graveson waveguide nor the Audax 34mm are cheap.
The diaphragm materials have a signature sound that is utterly different.
The SB29Be has an incredibly transparent, fast, shimmering quality. Tom Perazella says they're the best tweeters he's ever heard and I tend to agree with him. Amazing imaging. Brisk and holographic.
The TW034X0 have a soft, laid back, round sound that is more "midrange-y." They are less detailed. Warm and buttery. They still have a good top octave. (But the DSP also provides a +6dB boost at 20K; without the DSP they would be even warmer and more midrange-ey.)
Like I said completely different.
There is no question for me that the SB tweeter is superior. It's also about 3X more expensive.
The titanium coax in the Bitches Brew sounds much more similar to the SB than the Audax.
The Beryllium coax in the Birch Dipoles sounds even more similar to the SB29Be in the Cottonwood Dipoles.
You can see all of those other designs at www.perrymarshall.com/speakers
If someone wants a more aggressive "etched" tweeter sound in the Flanagangsters, I would suggest using a Visaton waveguide WG148R and matching it to a 25mm dome tweeter of your choice. This option will also be less expensive as neither the Troels Graveson waveguide nor the Audax 34mm are cheap.
Damnit, @perrymarshall … stop offering up so many interesting designs to pick from! I literally just got my BOM together for the 18” live edge dipoles, and now you have me rethinking which design to build!
@perrymarshall can you elaborate on the 200uF cap you used on the PA310 bass woofer? Trying to cost out a BOM for these… thanks.
@perrymarshall
Thanks for sharing your designs and thoughts here. Learning good stuff.
I wanted to pick your brain in regards to baffle width especially for midrange. I'm interpreting from your posts that imaging is very important to you - same here.
I noted from an earlier post (#4054) about the Bitches Brew Open that you selected the 15" coax to allow crossing over to the bass drivers at 110Hz. I was wondering about your experience using narrower baffles for the midrange (in my mind to improve imaging) and raising the xo to the bass. How much of a tradeoff is this in your view? How big of a factor was aesthetics in your choice?
I'm using an 8" mid on a 12" midrange baffle, crossing to an 18" on a wider baffle, but crossing at 300Hz. Maybe I should consider a wide baffle throughout like your Bitches Brew Open, Spatial Audio, etc.
Thanks for sharing your designs and thoughts here. Learning good stuff.
I wanted to pick your brain in regards to baffle width especially for midrange. I'm interpreting from your posts that imaging is very important to you - same here.
I noted from an earlier post (#4054) about the Bitches Brew Open that you selected the 15" coax to allow crossing over to the bass drivers at 110Hz. I was wondering about your experience using narrower baffles for the midrange (in my mind to improve imaging) and raising the xo to the bass. How much of a tradeoff is this in your view? How big of a factor was aesthetics in your choice?
I'm using an 8" mid on a 12" midrange baffle, crossing to an 18" on a wider baffle, but crossing at 300Hz. Maybe I should consider a wide baffle throughout like your Bitches Brew Open, Spatial Audio, etc.
ALL: I created a new dedicated thread at https://www.diyaudio.com/community/threads/open-baffle-bass-reflex-hybrid.393837/
@tlarwa and @diyiggy I responded to you there, see https://www.diyaudio.com/community/threads/open-baffle-bass-reflex-hybrid.393837/post-7217451
@Juhazi
@kd4ylq
@Studley
@perrymarshall
First off, thanks for bringing so much joy at the end of what has been a semi-crummy year. I plan on making one of your projects part of my new year.
I ended up using the Linkwitz LXmini because his bigger LX521 was not recommended for the size room I'm using at the moment, which is 12.5' x 14'. So what about the Bitches Brew? What's your minimum size recommendation?
First off, thanks for bringing so much joy at the end of what has been a semi-crummy year. I plan on making one of your projects part of my new year.
I ended up using the Linkwitz LXmini because his bigger LX521 was not recommended for the size room I'm using at the moment, which is 12.5' x 14'. So what about the Bitches Brew? What's your minimum size recommendation?
You're welcome, can't wait to see what you create.
Your 12x14 is exactly the same size as my room where the BB's are right now.
I do think my room is too small. But it's the room I've got and they still sound great.
FWIW I think they'll sound optimal in a room that has 2-5X that much space.
WUNDERBAR!!! Just what I wanted to hear! Now, I can shut HER down, and move on!
In a few years I'll have a much bigger space, but I was telling myself how nice it would be if I could work in the BBs now and slowly plan the elements of the ecosystem they'll eventually occupy.
Yes, the radian15 inch beryllium is twice as expensive and the dispersion pattern is quite a bit narrower than the B&C in the top octave. The B&C has a really nice radiation pattern all the way to the top.
Perry,
due to some confusion on my part concerning the sketches of the slabs, I find that my beechnut slabs are actually properly sized for the original Birch Live edge design and I think that is perhaps the better choice design for me for a few reasons. I like that the Kappa 18" woofer has more area and that the Radian 5208c is higher from the floor(+new 5 degree tilt). Also, the Radian has available the Beryllium compression driver in a coaxial configuration inside the mid-bass driver. The latest update on the crossover and DSP files (12-22-2022) will be added to my BOM and download document package. If you would, comment on your subjective critique of these latest birch version vs the (Be) cottonwood. Thanks so much!
Birch vs. Beryllium Cottonwood:
The Birch dipoles have 1/2 octave deeper bass. Cottonwoods need to be cut off sharply at 35. Birch go down to 25 and play a little louder.
Be Cottonwood is more more "measurement accurate." However they're also a little clinical and analytical. The Be tweeters are superb, no question about it.
I personally slightly prefer the Birch Dipoles. All the reasons listed above tilt slightly in their favor, most of all the bass.
Also, you could use an SB 15OB350 instead of the Eminence 18, it has comparable sensitivity and moves just as much air, and has a higher Q. Your choice. But you would have to mess with the EQ.
Too much nice woodworking in here, I figure I can bring the average down a bit with my latest OB lab project:
Top to bottom:
ESS Heil tweeter 1550 Hz & up
Eminence Beta 8a 450 - 1550 Hz
Faital Pro 15FH500 (8 Ohm) 80 - 450 Hz
Dayton RSS315HF-4 80 Hz & down (in the sealed box in the background, there's a second one midway down the left hand wall)
The Faitals were the only new drivers for this round, and they were on sale for a very good price. The rest I owned.
The rest of the system:
RPI 4 running Moode via SPDIF coax out, or Qobuz streaming via PC and Topping D10 DAC Toslink out
miniDSP 4X10HD
4 channels of Modulus 86 amps for the tweeters and mids, built by YT
Audiophonics Hypex NC252 stereo amp for the woofers (also new for this build)
Crown XLS1000 for the subs
The construction is crude, a 4x4 and some scrap plywood slapped together in an afternoon. The mid and woofer are held in place with paracord. The hood on the Heil was done a while back, so long ago that I can't tell you how much it actually changes the response.
The woofer is tipped back to aim the forward lobe more at my ears than my ankles (or the floor), and to put the nearby drivers as much as possible into the null of the woofer's response.
Getting good measurements of an OB system in a small room (14 x 11 ft) is not easy, but here's what I have today from REW and a UMIK-1. The sub measurement is a single sweep at the listening position with both subs on, PSY smoothed and level adjusted by eye. The rest were taken about 32" from the tweeter, mic centered on the tweeter, no smoothing beyond gating @ 30 ms (7 ms on the tweeter) and a 1/24 octave frequency dependent window. The green trace is the combined response without the subs:
Tweeter to mid to woofer crossovers are all LR4 slopes, with whatever EQ was needed to get there. The T-M-W physical offsets worked out so that no delays are needed in the DSP. I put a first order highpass on the woofers to keep excursion low. There is a LOT of EQ on the Faital, but it's so efficient that I can get away with it.
The room has a huge peak at 39 Hz, deep notch filters are needed on both the subs and the OB woofers to flatten that out.
Here's what I get with the mid phase inverted - pretty decent nulls if I say so myself:
OB bass is not supposed to work in a small room, but this sounds pretty good so far. In fact the whole thing sounds pretty decent IMO. I'm going to live with this a while before making any changes, and contemplate how to make it prettier.
Bill
Top to bottom:
ESS Heil tweeter 1550 Hz & up
Eminence Beta 8a 450 - 1550 Hz
Faital Pro 15FH500 (8 Ohm) 80 - 450 Hz
Dayton RSS315HF-4 80 Hz & down (in the sealed box in the background, there's a second one midway down the left hand wall)
The Faitals were the only new drivers for this round, and they were on sale for a very good price. The rest I owned.
The rest of the system:
RPI 4 running Moode via SPDIF coax out, or Qobuz streaming via PC and Topping D10 DAC Toslink out
miniDSP 4X10HD
4 channels of Modulus 86 amps for the tweeters and mids, built by YT
Audiophonics Hypex NC252 stereo amp for the woofers (also new for this build)
Crown XLS1000 for the subs
The construction is crude, a 4x4 and some scrap plywood slapped together in an afternoon. The mid and woofer are held in place with paracord. The hood on the Heil was done a while back, so long ago that I can't tell you how much it actually changes the response.
The woofer is tipped back to aim the forward lobe more at my ears than my ankles (or the floor), and to put the nearby drivers as much as possible into the null of the woofer's response.
Getting good measurements of an OB system in a small room (14 x 11 ft) is not easy, but here's what I have today from REW and a UMIK-1. The sub measurement is a single sweep at the listening position with both subs on, PSY smoothed and level adjusted by eye. The rest were taken about 32" from the tweeter, mic centered on the tweeter, no smoothing beyond gating @ 30 ms (7 ms on the tweeter) and a 1/24 octave frequency dependent window. The green trace is the combined response without the subs:
Tweeter to mid to woofer crossovers are all LR4 slopes, with whatever EQ was needed to get there. The T-M-W physical offsets worked out so that no delays are needed in the DSP. I put a first order highpass on the woofers to keep excursion low. There is a LOT of EQ on the Faital, but it's so efficient that I can get away with it.
The room has a huge peak at 39 Hz, deep notch filters are needed on both the subs and the OB woofers to flatten that out.
Here's what I get with the mid phase inverted - pretty decent nulls if I say so myself:
OB bass is not supposed to work in a small room, but this sounds pretty good so far. In fact the whole thing sounds pretty decent IMO. I'm going to live with this a while before making any changes, and contemplate how to make it prettier.
Bill
Every time I look at these I smile. Crude?
To my eyes industrial cool
Very nice
Here is the measured distortion, excluding the subs, in actual SPL and relative. In each graph distortion below the noise floor is greyed out. Both the 15FH500 and the Beta 8a show a bit more 3rd harmonic (yellow trace) than I would like to see, but I'm not sure how audible that would be. I do ponder what drivers would improve performance in those two positions.
Bill