Dual Opposed Dayton UM-18's for infrasonic art installation - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 113 Old 01-19-2019, 06:21 AM - Thread Starter
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Question Dual Opposed Dayton UM-18's for infrasonic art installation

After some research and advice I have a plan to use 2 18" Dayton drivers in a sealed box. The drivers will be positioned to be opposed to each other to prevent any vibrations.

I looked around for plate amps that could power both drivers in the same box and only found the SpeakerPower SP1-2400 Subwoofer Amplifier. It has 2400 watts. Since that plate amp is $1100 I have also been considering the Behringer NX3000 Ultra Lightweight Class D 3000W Power Amplifier instead.

The Behringer amp has speaker connections and I believe I . need to use Neutrik NL4MPR Speakon Connector 4 Pole Round Chassis Mount connections on the outside to the sub box.

I would use it with a MiniDSP 2x4.

The goal is as low of hz as possible to have an infrasonic experience in a museum installation.

I am still designing the box but am not sure how to optimize for low hz vs HT sound range. Is it better to have a vertical box with the drivers pointing up and down or a horizontal box? I will be cutting the box out on a CNC.

Is this a reasonable plan of action? What am I missing for low hz output?
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post #2 of 113 Old 01-19-2019, 06:47 AM
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I look forward to seeing the finished project. However, the NX/inuke3000 very likely will not have enough power for two UM18 drivers especially in a sealed box. I have used the inuke3000DSP with two separate UM15's in sealed boxes and they were a bit anemic until we switched to the NX6000DSP. I suggest looking into a used inuke6000/NX6000 (DSP not needed with mini DSP) since the UM18's need at last 1000 watts. Also, how large is the space you are trying to fill with infrasonics? How loud and low are you shooting for? My understanding is if the space is large, you need many drivers/sets of drivers and a good amount of power.
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post #3 of 113 Old 01-19-2019, 06:59 AM - Thread Starter
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Does the NX3000 not have enough power because the UM22-18's have two 2ohm coils that would wired in series to act as 4 ohms? The power output of the UX3000 is: 2 x 1500W @ 2 ohms, 2 x 900W @ 4 ohm so the 900w 2 would not be enough?

I only have 1 dedicated 20amp circuit for the amp so that will be the limiting factor. I have no problem using the NX6000 if it is needed. I have another circuit in the room but some of that is used for lighting but I could theoretically add another set of smaller dual opposed subs. Power will start to run out though

The room is 26' x 37' so I will not be able to cover the entire room due to electricity limitations but want to do the best I can.

I am mostly interested in below 20hz, hopefully down to 12hz but 15hz would be good. The concept is to have the sub ramp up to berely audible and then go down in hz for the visitors to the gallery to "feel" it as loud as possible. If handheld paper brochures flutter 12' feet from the sub that would be acceptable even if it can't be felt in the whole room.
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post #4 of 113 Old 01-19-2019, 07:11 AM
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If you are only looking only for infrasonics, why not consider a bandpass tuned really low. I THINK you would her way more output at low frequencies for the same power.

It might have the added benefit that the driver is stealthiest and all you would be looking at would be a port, which could also be turned in a direction that is not observed (possibly).

Bandpasses are very efficient and also prevent the driver over-excursion at low frequencies. I think hornresponse will let you model them.

It depends on your goals and how wide a frequency response you are looking for

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post #5 of 113 Old 01-19-2019, 07:40 AM - Thread Starter
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Originally Posted by kennyandersen View Post
If you are only looking only for infrasonics, why not consider a bandpass tuned really low. I THINK you would her way more output at low frequencies for the same power.
Is that the same as using the MiniDSP to flatten out the low frequency response? If using a bandpass tuned really low would be better I am all for it but just do not know what that means.

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It might have the added benefit that the driver is stealthiest and all you would be looking at would be a port, which could also be turned in a direction that is not observed (possibly).
By port do you mean not using a sealed box? Would it still be 2 opposed drivers but with an opening?

Drawing of room.

..................<- 37' ->........door
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post #6 of 113 Old 01-19-2019, 08:54 AM
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What am I missing for low hz output?
More details so we can help you more
Exactly what frequencies are to be reproduced? This is really critical. The lower and lower and lower you go, the harder and harder and harder it is to get significant output. The size (in 3 dimensions) of the listening area AND connected areas is also critical, as more and more spatial volume needs more and more cone motion to activate it. And at infrasonic frequencies, the ear is quite insensitive, you need to generate enough sound pressure to FEEL the vibration. But if there was a seating component, maybe bass shakers could be a better solution, or near field subs. Depending on the installation and the area, some kind of horn solution *might* be indicated, or a homemade version of the Bose Acoustic Wave Cannon.

P.S. Another factor is what is the sound LIKE? Constant tones? Just occasional sounds? Because peak amplifier power is a different beast from constant continuous tones. And about the amplifier power (having measured a LOT of amplifiers over the years): amplifier specs are a narrow and often inaccurate picture of an amplifier's power output into a resistor, not a real speaker. Driving amplifiers into a low impedance inevitably means less efficiency and more heat, and likely only a very small increase in power at clipping with actual music. If this is a long-term install, get a bigger and/or more amps than you need, don't load them to the minimum impedance so they don't break. Also, at the kind of power levels you're talking about, you cannot get that much power out of a wall outlet except for short peaks. You need to investigate where electrical power will come from, and what else is on that circuit. You don't want to crank up the install and blow out all the lights, or the staff refrigerator, for instance.
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post #7 of 113 Old 01-19-2019, 09:13 AM - Thread Starter
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More details so we can help you more
Exactly what frequencies are to be reproduced? This is really critical.
The size (in 3 dimensions)
Frequency range of 12-15hz up to 30hz for occasional audible output is my initial thought.

Space is 26' x 37' x 14' height (When I have posts I will post images and layouts of the space.)

There is no seating component so seat shakers will not help. Depending on the installation and the area, some kind of horn solution *might* be indicated, or a homemade version of the

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P.S. Another factor is what is the sound LIKE? Constant tones? Just occasional sounds? Because peak amplifier power is a different beast from constant continuous tones.
The concept is to have a semi constant barely audible rumble in the above 20hz range. This will increase and decrease in volume in sync with an LED light display. Then for brief periods of time (1 to 5 minutes) the sub would as low and loud as possible while a different sequence of lights happened. Then it would cut all playback, wait quietly for a few minutes before slowly playing audible greater that 20hz sounds before preparing for the infrasonic drop cycle.

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Also, at the kind of power levels you're talking about, you cannot get that much power out of a wall outlet except for short peaks. You need to investigate where electrical power will come from, and what else is on that circuit. You don't want to crank up the install and blow out all the lights, or the staff refrigerator, for instance.
One circuit is 20 amp 100% dedicated to the Subwoofer amplifier. The other 20 amp circuit is 100% dedicated to the exhibition lighting of the installation. It has some extra capacity but not more that 10 more amps. No other infrastructure on these circuits.

I know that the 80% continuous draw from a dedicated 20amp circuit of 1920 watts will be my limiting factor. I can have short bursts of 2400 watts. I want to do the best I can with that. Trying ti figure out box size, sealed / unsealed.

Thanks.
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post #8 of 113 Old 01-19-2019, 09:21 AM - Thread Starter
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Originally Posted by kennyandersen View Post
If you are only looking only for infrasonics, why not consider a bandpass tuned really low.
I am unfamiliar with a bandpass tuned really low. Is this the same as using the MiniDSP to flatten out the low frequency?

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Originally Posted by kennyandersen View Post
It might have the added benefit that the driver is stealthiest and all you would be looking at would be a port, which could also be turned in a direction that is not observed (possibly).
The sub will be behind a fabric object similar to a curtain so I am not concerned about the visibility of the drivers. I am most concerned with maximizing the infrasonic output from 12 - 20hz with the wall power limitations that i have. I am not locked into any design at this point so am open to a ported design if that is what will work best.
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post #9 of 113 Old 01-19-2019, 09:52 AM
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The inuke/nx3000 puts out about 600 watts per channel at 4 ohms. In bridged about 2000. The inuke/nx6000 puts out about 2000 per channel. In a more than 13K cft room corner loading may also be beneficial. I may have missed it but are you severely space/placement limited? What about a pair of Mini/Full Marty's? They are tuned to 17-18 hz and can be slightly modified to 15 HZ. These should have significant output into your required 12 hz range especially if corner loaded compared to the sealed option.
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post #10 of 113 Old 01-19-2019, 10:24 AM
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Frequency range of 12-15hz up to 30hz for occasional audible output is my initial thought.
My initial thought is if you can find an old Danley rotary sub https://www.danleysoundlabs.com/. They started off making special enclosures to play back elephant calls for researchers in Africa, in a similar or even lower range than what you are talking about. One time when I visited, Tom Danley showed me a piece of a long array used by NASA in Alabama to recreate sonic booms-3 Hz IIRC at like 170 decibels!!! No, I am not making this stuff up.

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Space is 26' x 37' x 14' height (When I have posts I will post images and layouts of the space.)...There is no seating component so seat shakers will not help.
The whole thing sounds very cool. What city will this be in?
The space will be enclosed? Or open? Another thing to consider is a raised dance hall/Saturday Night Fever false floor with shakers built in. A company I was associated with did that for the Consumer Electronics show one time. Of course, that is a different sensation, and you won't have the sound leaking into other areas. With subs, the sound will leak all over, which could be a cool kind of advertisement for the installation or could turn into a huge headache if it, say, resonates into the Director's office. Such low frequencies really travel and cannot be contained. Unless on concrete, they will also transmit through the floor from vibration of the sub itself.

As for the rest, you are basically running at continuous power for significant lengths of time. And yeah, the power you can draw from the wall has a limit, and you cannot draw 100% in real life as the breakers will trip. So the big big BIG key here is making the speaker highly efficient.

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I am unfamiliar with a bandpass tuned really low. Is this the same as using the MiniDSP to flatten out the low frequency?
No, not at all. MiniDSP can boost but uses more power to do so. Here are how speakers work (grossly oversimplified ha ha):
- Sealed: the cone moves air back and forth, making a pressure wave in the air, which is sound. (The air itself does NOT move from one place to another like if a fan were blowing, more like the air rocks back and forth as the wave passes through(
- Ported: like sealed at midbass and higher frequencies. Around the port tuning frequency, the physical air in the port acts like a mass sitting on the air in the box, which acts like a spring. So, like you on a trampoline, there is a magic frequency where when you bounce up and down at just the right rate you get in sync with the trampoline and bounce more and more. In the speaker, this means the cone motion is reduced a lot and the sound pressure comes mostly from the port.
- Bandpass (dual bandpass, to be picky): like a ported box on the front AND the back of the cone. You get the port effect at a higher and a lower frequency. Over a limited range like you need, the most efficient besides a horn.
As the system gets more complicated, the sound quality worsens because the time response (ringing, i.e. the sound continues out of the speaker after it stops from the amp, like if you stop jumping on the trampoline you still keep moving for a while). You don't need to worry about this for your application, so a bandpass is fine. Note that Bose claims patents on the dual bandpass, even though actually that was patented long before. Since you are not selling commercially I cannot imagine this should apply at all; disclosure I am not a patent attorney nor do I play one on TV.

- The Bose Acoustic Cannon is basically (bass-ically? ) an organ pipe on each side of the cone. Very faintly like the dual bandpass, one side resonates at a somewhat higher frequency and the other side at a lower frequency. I think that could be designed-perhaps in a program called AkAbak-to be very effective with your setup.

- Horns are different; some kind of cone moves air back and forth and, just like those old Victrola gramophones, the horn helps the tiny cone "grab" the air more efficiently. It is a transformer, acoustic instead of electric. (Note even an 18" cone is "tiny" compared to the Earth's entire atmosphere). Whether this could be effective in your installation depends on a lot more specifics, especially whether the install can be in a corner of hard walls.

Consider the speaker portion could be made very funky looking to complement the installation.
Here https://www.diyaudio.com/forums/subwoofers/ are a lot of crazy folks who could help. Describe the installation as you did, plus information about the space.
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post #11 of 113 Old 01-19-2019, 10:28 AM
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The miniDSP and SpeakerPower amp is the best way to go. I would avoid all of the other pro amps in this case due to fan noise...

Every time you double the power you gain 3db, the SpeakerPower will already max out the 20A breaker so there is nothing more that can be gained from power.

Do keep in mind that a 20A breaker can pass 40A for a brief amount of time, 20A is not a hard limit per se...
Burst figures mostly come from the internal bank of capacitors that some amplifiers have (you will notice a distinct lack of caps in the inukes vs a PowerSoft K20 or FP20k...)





Every time you double the number of cones, you gain another 3db, this carries on to infinity even if the wattage stays constant.

It takes about 32watts to push 32 18's to 1mm excursion, but it takes 3200watts to push 1 18 to 32mm's excursion, and both are the same SPL...

If you are limited by power, and you are, then chasing after more-cones and bigger-cones is the way to go.

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Originally Posted by subbuilds View Post
If handheld paper brochures flutter 12' feet from the sub that would be acceptable even if it can't be felt in the whole room.
That will require about 32 18's ported or horned to 10-15hz...

Every octave lower, gets 4x harder to produce (and 4x the equipment/price needed.)
1hz is 4x harder than 2hz
2hz is 4x harder than 4hz
4hz is 4x harder than 8hz
8hz is 4x harder than 16hz
16hz is 4x harder than 32hz

To make lots of low bass requires a LOT of displacement (which is cone area x excursion) [+ port displacement if applicable...]

To hear 20hz requires a minimum of 70db @ <10% THD.
To hear 10hz requires a minimum of 100db @ <10% THD.
These are minimums, not maximums...

The threshold for ear damage at 1-5hz is ~190-170db.
The threshold for ear damage at 5-10hz is ~170-160db.
The threshold for ear damage at 10-20hz is ~160db.
You won't be anywhere near these levels... so sky is the limit.

Every time you double the distance between the cones and your ear, you lose 6db.
That said, if you get too close to the sub you will be in the nearfield zone where ULF is weakest....
in many cases you will find that walls, ceilings and floors amplify the bass louder (it can also cause them to null out.)

I would highly recommend a CSL UMIK-1, those are professionally USA calibrated from 5hz to 25khz +-nothing, they are <$100. The stock UMIK-1 is 10-20khz, China calibrated.

It terms of making low-bass, nothing beats a 24 or RE-18. It's all about woofing as much air as possible.
The rest is box optimization and placement optimization.

The miniDSP can EQ and XO to at least 10hz, so you should be good there. Most other products stop at 20hz.
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post #12 of 113 Old 01-19-2019, 11:21 AM
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There is a fairly good chance you'll end up smoking 2 UM-18's within the first few minutes of ULF.

2 18's just simply isn't enough for this task.

In any case, I highly recommend you have computer fans inside the boxes that blow air directly on/across the coils to help keep them cool, that will significantly increase their run-time and/or recovery-time.

Removing the heat from the box will be another problem. You already know how hot a 60w bulb gets, now imagine a 2400w bulb trapped in a box surround by plastics and glues. Don't let the magic-smoke out

If you want some truly frighteningly-low bass, I recommend you download the remix of this song in the vid description.
It is at least entertaining, if nothing more.

There are actually very few songs that go below 20hz.
BassILoveU is 6.5hz and 17hz or so, and most consider that a pretty rare "extreme" bass song. Most of Bassotronics songs are...

Beyond that you'll be limited to ultra-high quality recordings of space shuttle launches, doorslams, elephants, blue whales, earthquakes/road noise, thunder, 128ft pipe organs, and synthetic sinewave tones.

Unfortunately most recordings aren't high quality, they use cheap china mics that rolloff at 20hz, not something decent like the Zoom HD mics or AcoPacific or Lewitt 540S mics...

There just isn't much down that low, and the number of quality sources that capture that are even lower.
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post #13 of 113 Old 01-19-2019, 12:12 PM - Thread Starter
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Originally Posted by Zarkoff500 View Post
I may have missed it but are you severely space/placement limited? What about a pair of Mini/Full Marty's? They are tuned to 17-18 hz and can be slightly modified to 15 HZ. These should have significant output into your required 12 hz range especially if corner loaded compared to the sealed option.
I have seen these Marty's referred to in the forums but am not familiar with them. I am not completely space limited but can only put the subs on 2 walls shown in the attached image. IF it will give me better coverage with subs on both walls rather than a sealed box with the subs in opposed configuration I am ok with that. I was trying to avoid audible rattle of the sub boxes by using an opposed configuration.

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What city will this be in? The space will be enclosed? Or open?
It will be down south, will post details as project gets further along. It will be indoors, I posted a layout in the post above.

The idea of a shaking dance floor seems cool but won't work for this application. Maybe in the future.

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As for the rest, you are basically running at continuous power for significant lengths of time. And yeah, the power you can draw from the wall has a limit, and you cannot draw 100% in real life as the breakers will trip. So the big big BIG key here is making the speaker highly efficient.
Yes, as BaseThatHz also pointed out, power will be my limiting factor. I wish there was more but there isn't for this room. Now the goal is to use the 20amps I have as best as possible.

Thank you for your primer on speaker tech. It was really helpful. From your description it seems that I might be better served by a dual bandpass or a diy cannon. I would not know how to calculate the design of either but have the fabrication skills to build them. I thought about having the subs be part of the visual installation and might be ok with that but for now will be keeping them behind the fabric structures.

What information do I need to make the calculation for the bandpass and / or cannon design ?
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Thank you for showing me the inside of the amps. Very obvious with the plate amp having more caps. Wouldn't having the plate amp in the sub box worsen heat disbursement?

Quote:
Originally Posted by BassThatHz View Post
It takes about 32watts to push 32 18's to 1mm excursion, but it takes 3200watts to push 1 18 to 32mm's excursion, and both are the same SPL...

If you are limited by power, and you are, then chasing after more-cones and bigger-cones is the way to go.

That will require about 32 18's ported or horned to 10-15hz...
Fascinating about having more cones but using less power to get the same result. I cannot afford 31 18's for this project. I could swing 4 and possible 6 18's but wouldn't I be running out of power to drive them since I only have 20amps?

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Originally Posted by BassThatHz View Post
To hear 20hz requires a minimum of 70db @ <10% THD.
To hear 10hz requires a minimum of 100db @ <10% THD.
Thank you. That is what I "want" then. Is that possible with my 20amp circuit limitation?
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post #16 of 113 Old 01-19-2019, 12:34 PM - Thread Starter
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There is a fairly good chance you'll end up smoking 2 UM-18's within the first few minutes of ULF.

2 18's just simply isn't enough for this task.

In any case, I highly recommend you have computer fans inside the boxes that blow air directly on/across the coils to help keep them cool, that will significantly increase their run-time and/or recovery-time.
I was afraid of that physics reality. I don't mind having fans run to cool the drivers. There will be other fans in the room so fan noise is not a problem.

I have one dedicated 20amp so at 80% that is 1920 continuous watts. I could "steal" another 1000watts from a nearby circuit but that would be the max available.

I could add up to 6 UM-18's but am not sure if there is enough available power to drive them.

What would you do if you had that power limitation?


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There are actually very few songs that go below 20hz.
It will not be used to reproduce music or movies. It will play artificially generated sine tones. I am working with a musician to do that.
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post #17 of 113 Old 01-19-2019, 12:43 PM
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I could add up to 6 UM-18's but am not sure if there is enough available power to drive them.

What would you do if you had that power limitation?
If you can go with 6 drivers that is going to boost efficiency no matter what design you ultimately go with. Something as simple as 6 ported boxes as big as you can reasonably make them will probably get you to your goals while using a modest amount of power, while helping to alleviate the heat issue since you are spreading the power over more coils and boosting efficiency a ton.
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post #18 of 113 Old 01-19-2019, 12:55 PM - Thread Starter
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If you can go with 6 drivers that is going to boost efficiency no matter what design you ultimately go with. Something as simple as 6 ported boxes as big as you can reasonably make them will probably get you to your goals while using a modest amount of power, while helping to alleviate the heat issue since you are spreading the power over more coils and boosting efficiency a ton.
Does that mean that I would not ever drive the UM-18's at their 1000w?

How do I go about determining the box sizes and power requirements for the added drivers?

It seems that with only one 20amp circuit I wouldn't be able to drive more than two 18's to their max.
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post #19 of 113 Old 01-19-2019, 12:59 PM
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Originally Posted by subbuilds View Post
Does that mean that I would not ever drive the UM-18's at their 1000w?

How do I go about determining the box sizes and power requirements for the added drivers?

It seems that with only one 20amp circuit I wouldn't be able to drive more than two 18's to their max.
6 cones getting 2400W will vastly outperform 2 cones getting 2400W, though. Maximizing efficiency is going to be your path to success given that you are power-limited. The alternative designs others are throwing out there (bandpass, horn) are just other ways to increase efficiency at the cost of complexity. You could also do 6 of them if you wanted to go all-out.
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Video: Sony 85" X900F @ 80" eyes-to-screen (49.4° viewing angle)
Audio: Denon AVR-X4400H 7.2.4 Atmos
Mains: Fusion-15 LR, Custom Tapered Ported Volt-6 Center, Ported Volt-10 Surrounds, Custom 45°/45° Double-Angled Ported Volt-6 Atmos
Subs: The Two Towers (HT18 32cf 11.5Hz x 2), UM18 4cf x 2, Crowson MAs x 4
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post #20 of 113 Old 01-19-2019, 01:07 PM
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Quick and dirty model of 6 ported UM18s in 20cf each tuned @ 15Hz getting 400W of power each produces 120-125dB @ 15Hz @ 3m away assuming wall/corner boundary reinforcement and no room gain.

The same boxes with a quantity of 2 getting the same 2400W total come in about 4.8dB less.
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Take the Red Pill (BassEQ) BassEQ Demo Clips
Video: Sony 85" X900F @ 80" eyes-to-screen (49.4° viewing angle)
Audio: Denon AVR-X4400H 7.2.4 Atmos
Mains: Fusion-15 LR, Custom Tapered Ported Volt-6 Center, Ported Volt-10 Surrounds, Custom 45°/45° Double-Angled Ported Volt-6 Atmos
Subs: The Two Towers (HT18 32cf 11.5Hz x 2), UM18 4cf x 2, Crowson MAs x 4

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post #21 of 113 Old 01-19-2019, 01:09 PM
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Like bass that hz said, You need better drivers if you want them to handle some power. For the same price you can add two layers to the voice coil.

https://www.skaraudio.com/products/e...nt=30196958669

These skar audio have 4 layer 3 inch coils. vs 2 layer for the Daytons, and the price is cheaper!

I would shop and see how much you can maximize your voice coil size for the money as there are lots of subs.

I always said more displacement always beats more power...............
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A Good amplifier requires a adequate power supply, It does not matter what the amplifier is capable of if the power supply will not provide the power required. Most amplifiers have under rated power supplies. It is up to you to make sure you get the ones that are least under rated if at all.
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post #22 of 113 Old 01-19-2019, 01:16 PM - Thread Starter
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Quote:
Originally Posted by aron7awol View Post
Quick and dirty model of 6 ported UM18s in 20cf each tuned @ 15Hz getting 400W of power each produces 120-125dB @ 15Hz @ 3m away assuming wall/corner boundary reinforcement .

The same boxes with a quantity of 2 getting the same 2400W total come in about 4.8dB less.
Thank you. Your explanation along with others' about efficiency has convinced me. I will get as many drivers as I can budget. I can definitely get 4 18's but will strive for 5 or 6.

20 cubic feet per driver? Those will be big boxes, might run out of room.

Does the wall/corner boundary reinforcement refer to the sub boxes, the placement in the room or closing the room up? Would I be able to line all 6 up on one side of the room? Will these individual boxes have significant more vibration than the sealed dual opposed version? I might have been worrying about nothing there. I want to avoid making sound with vibrating subs and want to focus on the potential of "felt" sound.
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post #23 of 113 Old 01-19-2019, 01:22 PM
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Quote:
Originally Posted by subbuilds View Post
I could swing 4 and possible 6 18's but wouldn't I be running out of power to drive them since I only have 20amps?
No.

NO! NO! NO!

Quote:
Originally Posted by BassThatHz View Post


Every time you double the number of cones, you gain another 3db, this carries on to infinity even if the wattage stays constant.

It takes about 32watts to push 32 18's to 1mm excursion, but it takes 3200watts to push 1 18 to 32mm's excursion, and both are the same SPL...
Read that again. More drivers equals more volume (spl). Even if you never add another watt of power.
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post #24 of 113 Old 01-19-2019, 01:25 PM
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You could go more extreme with something like 16 PA460s, but at some point the number of boxes you have to build, the amount of space they take up, and the hassle of moving them around becomes unreasonable.

You don't have to go 20 cf per box, you can go smaller and give up some efficiency.

20 cf would be ~1.8dB louder at tune than 15cf, which is ~2.8dB louder at tune than 10cf. Another trade-off to decide on.

I wouldn't be concerned with not going dual-opposed.
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Video: Sony 85" X900F @ 80" eyes-to-screen (49.4° viewing angle)
Audio: Denon AVR-X4400H 7.2.4 Atmos
Mains: Fusion-15 LR, Custom Tapered Ported Volt-6 Center, Ported Volt-10 Surrounds, Custom 45°/45° Double-Angled Ported Volt-6 Atmos
Subs: The Two Towers (HT18 32cf 11.5Hz x 2), UM18 4cf x 2, Crowson MAs x 4
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post #25 of 113 Old 01-19-2019, 01:29 PM
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Going with multiples helps in so many meaningful ways. As mentioned, more efficiency which means more SPL for the same power, but also consider the other benefits. Less distortion, less power compression, less port compression, less heat to dissipate per coil.

Also worth considering IMO is how useful they'll be after the art installation is over. You'll have 4-6 awesome HT subs to use. That's a big reason, along with simplicity, that I'd choose ported over a more exotic design such as a bandpass. And if your future HT application isn't as power-limited as this art installation, you have even more headroom to add amps and gain even more SPL.
subbuilds likes this.

Take the Red Pill (BassEQ) BassEQ Demo Clips
Video: Sony 85" X900F @ 80" eyes-to-screen (49.4° viewing angle)
Audio: Denon AVR-X4400H 7.2.4 Atmos
Mains: Fusion-15 LR, Custom Tapered Ported Volt-6 Center, Ported Volt-10 Surrounds, Custom 45°/45° Double-Angled Ported Volt-6 Atmos
Subs: The Two Towers (HT18 32cf 11.5Hz x 2), UM18 4cf x 2, Crowson MAs x 4

Last edited by aron7awol; 01-19-2019 at 01:42 PM.
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post #26 of 113 Old 01-19-2019, 01:45 PM - Thread Starter
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Quote:
Originally Posted by aron7awol View Post
Going with multiples helps in so many meaningful ways. As mentioned, more efficiency which means more SPL for the same power, but also consider the other benefits. Less distortion, less power compression, less port compression, less heat to dissipate per coil.
I am convinced.

I still need to decide between sealed ported. It seams that is already decided since I need to go ported for efficiency. The ported box design has to be designed / tuned for low hz correct?

Would it be better to use 500w plate amps on each box or make each a passive sub with a rack amp? Should I put 1000w plate amps in each box for future use even though I can't use that power in this case?

Is it best to have each driver in its own ported box or to have 3 boxes with 2 drivers in each one?

I am learning a lot, thank you.
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post #27 of 113 Old 01-19-2019, 01:49 PM - Thread Starter
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Quote:
Originally Posted by johnplayerson View Post
These skar audio have 4 layer 3 inch coils. vs 2 layer for the Daytons, and the price is cheaper!

I would shop and see how much you can maximize your voice coil size for the money as there are lots of subs.

I always said more displacement always beats more power...............
I am by no means wedded to the UM-18's but the Skars that you linked to have a frequency response of 37hz vs the 19hz of the UM-18's. Wouldn't i have farther to go to get down to 15hz?

I do like the price. I would be able to get 6 of the Skars if they would work for the low hz requirement.

How does the 4 layer coil add more displacement?
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post #28 of 113 Old 01-19-2019, 01:58 PM
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Quote:
Originally Posted by subbuilds View Post
I am convinced.

I still need to decide between sealed ported. It seams that is already decided since I need to go ported for efficiency. The ported box design has to be designed / tuned for low hz correct?

Would it be better to use 500w plate amps on each box or make each a passive sub with a rack amp? Should I put 1000w plate amps in each box for future use even though I can't use that power in this case?

Is it best to have each driver in its own ported box or to have 3 boxes with 2 drivers in each one?

I am learning a lot, thank you.
Yeah ported is going to crush sealed at 15Hz.

Making them passive is going to be much cheaper and easier.

Each driver in its own box will be easier to move around and more flexible for future use so that's what I'd go with personally.

If you settle on the ~10cf size you might as well go with Full Martys for the simplicity of the build.
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Take the Red Pill (BassEQ) BassEQ Demo Clips
Video: Sony 85" X900F @ 80" eyes-to-screen (49.4° viewing angle)
Audio: Denon AVR-X4400H 7.2.4 Atmos
Mains: Fusion-15 LR, Custom Tapered Ported Volt-6 Center, Ported Volt-10 Surrounds, Custom 45°/45° Double-Angled Ported Volt-6 Atmos
Subs: The Two Towers (HT18 32cf 11.5Hz x 2), UM18 4cf x 2, Crowson MAs x 4

Last edited by aron7awol; 01-19-2019 at 02:03 PM.
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post #29 of 113 Old 01-19-2019, 02:06 PM - Thread Starter
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Quote:
Originally Posted by aron7awol View Post
Yeah ported is going to crush sealed at 15Hz.

Making them passive is going to be much cheaper and easier.

Each driver in its own box will be easier to move around and more flexible for future use so that's what I'd go with personally.

If you settle on the ~10cf size you might as well go with Full Martys for the simplicity of the build.
According to other threads, it looks like if I change the port size of the Full Marty from 3" to 2.5" that would get 15hz.

Thank you to you and everyone else. Now I have a basic outline of a plan. I will continue to research and then come back with more questions after I have played with some designs and iterations of placement.
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post #30 of 113 Old 01-19-2019, 03:17 PM
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I will go back a bit and again suggest the dial bandpass subwoofers.

1) very efficient
2) ability to tune low
3) protects driver from big excursion at low frequencies
4) you don't care about phase, ringing, or integrating to another driver in the upper frequency.

If you go ported you lose the efficiency, and you would need to meet with a high pass filter to protect the driver.

My guess is you could make enough SPL with (4) 18" band pass subs. You might could add 2 more, but you will have to be careful how everything is wired up so that you have the right impedance match with your amp i.e. if your amp will drive a 2 ohm load you want the speakers to present that. That might mean it is difficult to do 6, defending on the driver impedance.

As previously stated, it is generally better to have more, if you can work that out. VLD (very large drivers) require very large and heavy boxes. IMHO that would make then impractical -- heavy, boxes for the 18s will already be a handful!
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Last edited by kennyandersen; 01-19-2019 at 08:07 PM.
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