Hi, everyone! While I have followed DIY speaker design for years, I have yet to actually build my own, but am considering doing so now in order to fit a big electronic church organ into my living room. Allen Organ speakers work very well to reproduce the sound of their electronic instruments, but their full-range cabinets are about 18" x 18" x 33", making even a four-channel setup just too big for my living room. I really want to fit an eight-channel or larger instrument into my living room, but you can imagine the volume occupied by eight or more of those speakers!
My difficulty in figuring out a good speaker design is that organ music is probably the most demanding in terms of frequency response. Most of the channels will need to go down to 32Hz, and the bass-only channels down to 16Hz (obviously requiring a subwoofer!). The flip side is that Allen organs offer great adjustment capabilities in their tone generation, meaning that a smooth and gradual rolloff in the bass can be compensated for by tonal adjustments, so even a 10 or perhaps even 20 dB dropoff can be corrected to sound flat as long as the curve is smooth enough.
In summary, based on what I know of speaker design, the challenges and simplifying assumptions are:
My difficulty in figuring out a good speaker design is that organ music is probably the most demanding in terms of frequency response. Most of the channels will need to go down to 32Hz, and the bass-only channels down to 16Hz (obviously requiring a subwoofer!). The flip side is that Allen organs offer great adjustment capabilities in their tone generation, meaning that a smooth and gradual rolloff in the bass can be compensated for by tonal adjustments, so even a 10 or perhaps even 20 dB dropoff can be corrected to sound flat as long as the curve is smooth enough.
In summary, based on what I know of speaker design, the challenges and simplifying assumptions are:
- The speakers have to be as small as possible, since I'll have a bunch of them.
- Cost is important for the same reason, but I'm more sensitive to size.
- They need to sound good even when placed close to a wall and ceiling. Fortunately, Allen organs offer note-by-note adjustments, so frequency peaks and valleys can be corrected for as long as they are not too great.
- Frequency response has to have good usable output down to 32Hz, but a slow rolloff as from a sealed enclosure can be compensated for in voicing adjustments. Usable output is the key; it doesn't have to be flat, although that would certainly be nice.
- Stereo imaging is not important, as each channel is independent. Broad dispersion of the sound is preferred.
- While I'm decent at woodworking, I don't plan to make these cabinets look too fancy. Pre-cut cabinets would be great, but I'm willing to do more work if it will sound better. With all these speakers, I'm planning to finish them in some unobtrusive way so they blend into the room instead of standing out with exotic wood finishes.
So, one thing that might save you. Since you're already willing to have a subwoofer you can say goodbye to the need for each speaker to go down to 32 Hz, which will give you considerable size savings. It's been shown consistently in home theater forums you can't localize all that well below 80Hz, so in my opinion you'd only need the speakers to reach down to there and let the sub take over. I'd recommend two subwoofers for smoother response.
I'd personally recommend looking at any builds that use the Dayton ND105. Fantastic bass for the size down to about 90 Hz. Perfect spot for the subwoofer to take over. You won't get much more extension out of a small bookshelf without using quite a lot of power. To get bass you need either size or power. This is known as Hoffman's Iron law: 1) Bass Extension 2) Efficiency 3) Small Enclosure <- Pick two, the third will be sacrificed.
Also, generally vented will give you better bass extension than sealed. (in general, there are always exceptions).
That ND105 would take about .5 cubic foot (including room for port). There are flatpacks from PartsExpress in that size. You'd have to do some simming to find the right one.
I'd personally recommend looking at any builds that use the Dayton ND105. Fantastic bass for the size down to about 90 Hz. Perfect spot for the subwoofer to take over. You won't get much more extension out of a small bookshelf without using quite a lot of power. To get bass you need either size or power. This is known as Hoffman's Iron law: 1) Bass Extension 2) Efficiency 3) Small Enclosure <- Pick two, the third will be sacrificed.
Also, generally vented will give you better bass extension than sealed. (in general, there are always exceptions).
That ND105 would take about .5 cubic foot (including room for port). There are flatpacks from PartsExpress in that size. You'd have to do some simming to find the right one.
I have wondered about that, but wouldn't that require me to use some sort of complicated multi-channel mixer to be able to combine the bass signals from as many as 16 channels before feeding the combination into one or two subs? That seems like a problem.
More importantly, one of the reasons for lots of channels is that electronic organ tone generation really works best with acoustic mixing of the signals rather than electronic mixing. Consider two sounds on two channels that happen to be around the same frequency and timbre (say, two flutes tuned to almost the same pitch, but not quite). When they happen to be in phase, they will constructively interfere, but when they happen to be out of phase, they will destructively interfere and can cancel each other out completely in the worst case. If this happens in the 32-64 Hz range, you'll end up with a really annoying wah-wah-wah effect that will definitely be unpleasant. The only solution to this without really complicated convolution reverb calculations is to keep the signals separate and let the sounds mix in the air.
Therefore, at least for now, I am taking it as a given that each speaker needs to reach down to at least 32 Hz (low C for 16' stops). That output can be attenuated, but has to be usable if boosted electronically in the tone generation.
PS: I realize that what I ideally want is probably impossible
. But given those three tradeoffs, I would sacrifice efficiency first. I will have plenty of power available, since electronic organs are designed to be able to fill an auditorium with sound. My living room will be a piece of cake by comparison.So if I give up on efficiency and want low bass in a small enclosure, how best should I accomplish this?
What an interesting project mlaird. Does the organ output a speaker level signal for all those channels or do you need to feed separate amplifiers? Is each output at full frequency or can you split frequencies for high and low at the organ?
Regarding the speaker selection, to keep things small and prefab, I would go with kits from parts express as well, as suggested earlier. A bookshelf and subwoofer combo makes sense. There are some great quality bookshelf kits such as the C-Notes. These will easily match with a sub. To get down to 32Hz you’ll probably need at least 10” subs. There is a Dayton Ultimax 10” kit that would fit the bill.
And curious... what is your budget?
Regarding the speaker selection, to keep things small and prefab, I would go with kits from parts express as well, as suggested earlier. A bookshelf and subwoofer combo makes sense. There are some great quality bookshelf kits such as the C-Notes. These will easily match with a sub. To get down to 32Hz you’ll probably need at least 10” subs. There is a Dayton Ultimax 10” kit that would fit the bill.
And curious... what is your budget?
The organ has its own amps for all the channels, and the typical design is N channels that are expected to handle down to 32 Hz, and a smaller number of subwoofer channels that have to go all the way down to 16 Hz. The crossover that pulls out the really low frequencies is built into the organ's audio board so I wouldn't have to worry about it.
The problem with that plan is that if I have eight channels, I'd need 8 subwoofers, and that's going to take up a lot of space. What I really want to achieve is a set of speakers similar to the original complement from the manufacturer, but smaller in size, even if I have to give up power and efficiency (since I can compromise on that).
For example, the Allen organ at my church has eight full-range channels plus a subwoofer channel. If I bought an instrument like that, I'd like to have eight smaller cabinets that can handle down to 32Hz, and one subwoofer that can handle down to 16Hz. I'd run the sub off the organ's existing bass split for the one channel that has the 32' pedal stops.
That's negotiable more than the space limitations
. The more the speakers cost, the less budget I'll have to buy the instrument itself. Part of this exercise is to figure out if this whole idea is a "pipe dream" (so to speak)! 
how much power is there for each of the built-in low amplifiers? Assisted 6th order bass reflex is one compact way but requires an underdamped 2nd order highpass filter with 6dB peaking at the box tuning frequency. A speaker for 6th order reflex would have qts around 0.3 and fs ~32 for your application.
If not for the multichannel needs, I would suggest a Karlson K12 - tapped horn setup. I have a little Karlson 12 cabinet loaded with Eminence Kappa12a and on the late Rudy Rosa's heavy string synth - it has more emotion impact and "grab" than my Klipschorn which sits behind it. That little Karlson probably only goes to ~75Hz but the upper bass and mid clarity are important. It will be interesting to see what route you take. Some sealed 2-way boxes like Henry Kloss' old "Smaller Advent" might reach 32Hz with not much EQ. That might be one way to do 8-16 channels. Are there woofers today suitable for that size box with similar parameters ?
Smaller Advent Stereophile article
The Smaller Advent loudspeaker | Stereophile.com
Description: Two-way acoustic-suspension bookshelf loudspeaker. Drive-units: 2" paper-cone tweeter with central dome, 9.5" paper-cone woofer. Frequency response: 33Hz–17kHz ±3dB (measured by 1975 High Fidelity Buyer's Guide). Nominal impedance: 4 ohms. Recommended minimum power: 15W.
Dimensions: 20 1/8" (515mm) H by 11 5/8" (300mm) W by 9 3/8" (240mm)
If not for the multichannel needs, I would suggest a Karlson K12 - tapped horn setup. I have a little Karlson 12 cabinet loaded with Eminence Kappa12a and on the late Rudy Rosa's heavy string synth - it has more emotion impact and "grab" than my Klipschorn which sits behind it. That little Karlson probably only goes to ~75Hz but the upper bass and mid clarity are important. It will be interesting to see what route you take. Some sealed 2-way boxes like Henry Kloss' old "Smaller Advent" might reach 32Hz with not much EQ. That might be one way to do 8-16 channels. Are there woofers today suitable for that size box with similar parameters ?
Smaller Advent Stereophile article
The Smaller Advent loudspeaker | Stereophile.com
Description: Two-way acoustic-suspension bookshelf loudspeaker. Drive-units: 2" paper-cone tweeter with central dome, 9.5" paper-cone woofer. Frequency response: 33Hz–17kHz ±3dB (measured by 1975 High Fidelity Buyer's Guide). Nominal impedance: 4 ohms. Recommended minimum power: 15W.
Dimensions: 20 1/8" (515mm) H by 11 5/8" (300mm) W by 9 3/8" (240mm)
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here's a $25.27 Dayton Classic 8 inch woofer in a 32 liter vented box - no eq needed
That same woofer could be put in a smaller sealed box then operated as 3rd order sealed box
by adding a series 450uF bipolar capacitor.. It has to work harder at the low end.
This is 22 liters so with fill might be made smaller - The sim says 16 liters is pretty good so maybe even a bit below 16 with fill. (?)
That same woofer could be put in a smaller sealed box then operated as 3rd order sealed box
by adding a series 450uF bipolar capacitor.. It has to work harder at the low end.
This is 22 liters so with fill might be made smaller - The sim says 16 liters is pretty good so maybe even a bit below 16 with fill. (?)
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I don't know offhand, but I believe a few hundred watts, conservatively rated. Allen usually runs their bass channels using one of the big boys at the bottom of this page:
Allen Organ Company
The SR-1 in particular looks like it would rattle the rafters with as much low bass as you could want! I won't need anywhere near that much power for a living room.
I'll have to read up on these terms to understand you
. But that should be fun.That's exactly the kind of design I was thinking of, but I don't know enough about woofers to know if there are any available today that could fill this role. The dimensions are still a little larger than I would like, but way better than 18x18x33.
Hmm, ages ago, relatively inexpensive PA ceiling two-ways such as this one were used to get an organ's 'Sturm und Drang' in a compact package and there's smaller, cheaper available, though at lower efficiency: https://www.electrovoice.com/binary/409_38109864.pdf
Then one or more 'subs' to handle the < 100 Hz BW.
GM
Then one or more 'subs' to handle the < 100 Hz BW.
GM
that $26 Dayton woofer I simulated above would be usable. As shown , less than 2/3's cubic foot would work with it for a 3rd order sealed box with 450uF capacitor. An inexpensive little fullrange could be rolled in wherever to give upper mids and treble. A crossover for the woofer would run the cost up somewhat, With the fullrange in a small sealed compartment and 2nd order highpass, the little cone would not be moving much so should remain pretty clean. The FR guys could suggest something. That arrangement used to be called a "FAST" - - - maybe "WAW" now for woofer assisted wideband (?)
I was thinking [4] of these high Xmax, low Fs horn drivers in either small sealed cabs if there's enough room/corner gain down real low or in tall 8" cardboard tube TLs to either stand up or better yet, laid down along baseboards for the <100 Hz BW: https://www.newark.com/mcm-audio-select/55-2421/8-high-excursion-woofer-120w-rms/dp/88C7835
GM
I was thinking that originally, but at least with the standard channel assignments, Allen seems to spread out the pedal stops so that this idea doesn't help much. E.g., the Swell has a couple 16' stops that are borrowed to the pedal and need to have a good bottom end, so those two channels (C/C#) both need full support down to 32 Hz. Ditto for the Great. The Choir probably could be cheated on, since it only has a couple light 16' stops, but that's only two channels out of eight on my church's instrument. I think in order to simplify construction, I'll just build N copies of the same design.
I like the possibilities in those simulated response graphs you made up; thanks! I don't mind spending more to make things sound their best, so I'm assuming I'd need at least a woofer and tweeter with an appropriate crossover. I'm afraid as a newbie here I don't know what you mean by FR and FAST. I'll try to look it up, but pointers would be appreciated.
Again, sorry for being a newbie here, but I don't follow what you're thinking. TL is transmission line, right? Those seem to usually be rather tall cabinets, or long if laid down. If I need long 8" cardboard tube "cabinets" to produce the frequencies below 100 Hz, I'd need 8-16 of those, and that sounds like it would be too much for my living room. If instead I can build 2/3 cu ft cabinets like Freddi was proposing, those I can envision fitting into my room on a shelf or stacked vertically on the sides of my organ console.
I went to the site, I looked at pictures available, even downloaded a manual, and still don't understand how it outputs the channels.
OP, could you tell us how the organ outputs eight channels?
Are there 8 RCA or XLR plugs? Is it MIDI, or USB?
I can't find a picture of the output board nor can I find information on how the channels are routed.
That would help a lot.
OP, could you tell us how the organ outputs eight channels?
Are there 8 RCA or XLR plugs? Is it MIDI, or USB?
I can't find a picture of the output board nor can I find information on how the channels are routed.
That would help a lot.
Allen sends line-level audio out of their custom audio processing boards into their amplifiers that are either mounted inside the organ console, or in external racks. So I'll have N speaker-level outputs going into N of their big speaker cabinets, and I want to shrink the cabinets down in size. Allen's speakers do a great job and can fill large auditoriums with the full range of frequencies from 16 Hz all the way up to 20KHz, but the cabinets are not designed to fit in my living room. Their amps can drive 4 ohm loads, so I'm not concerned about audio power. I just need smaller speakers that can produce the full range of frequencies, and am willing to sacrifice efficiency if needed to get the size down and the cutoff frequency low enough.
that MCM would half way work in a 3rd order box with 900uF - 8 liters airspace is tiny - not the most efficient thing/
In a 16 liter vented box, it would be strong to 32Hz - but getting a practical vent might be tough. A passive radiator is one
solution but more $. GM will come up with something cool.
In a 16 liter vented box, it would be strong to 32Hz - but getting a practical vent might be tough. A passive radiator is one
solution but more $. GM will come up with something cool.
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