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Dayton audio 15 inch UM sealed sub build
Dayton audio 15 inch UM sealed sub build
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Old 14th March 2019, 10:01 AM   #1
Elgreco31 is offline Elgreco31
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Question Dayton audio 15 inch UM sealed sub build

Hi all.

First time sub DIYer (and first time poster, so please be gentle) who is completely and utterly confused by the sheer volume of information on this inter-web thingy.

I’ve been holding off posting for fear of being told that all the info is easily available….but honestly, I’ve read shed-loads over the past 6 months and I feel
like I’m only just scratching the surface.

Disclaimer: I am not a gifted electrician and only a mediocre woodworker. I live in Belgium so will be mixing and matching metric and imperial measurements. Apologies for this.

As a brief summary/background:
I have a couple of Q Acoustics 3050s and also the Q Acoustics 3090 centre speaker that I picked up on a special offer (probably just before they launched the 3050i upgrades)

After what feels like an eternity of reading forums, I decided to try my hand at DIY after seeing prohibitively expensive prices for any subs above 10”.
I own a drill, a sander and a jigsaw so thought this would doable.

I modelled a sealed 15” UM from Dayton through WinISD and have put together ¾ of the 4cubic foot enclosure based on various guides and advice found online.
My build will be a downward firing sub (to pacify the wife and disguise it as a chunky coffee table…)

I am fully aware that a 15” will be too small for my room (I do not have a dedicated HT room and our house has adjoining rooms/areas without separation… so the TV area sits between the ‘living’ area and the ‘dining area, meaning the space is huge). However, it will undoubtedly be better than the ‘no sub’ I have now. If this project works, I will also be looking to add a second sub in future (more on that later).

I (wisely) decided to see how good of a woodworker I was before investing in the expensive elements (such as the driver and the amp). Surprisingly the thing looks solid and airtight (well, the bit that is built is; it’s still missing the bottom…). It’s also pretty effing huge, even for a sealed sub. I dread to think how big an 18” UM ported box would be.

I plan to do a double thickness bottom with the speaker recessed through the first layer and attached to the second layer to limit accidental damage to the driver from underneath (I have small kids) – if that makes sense.

I’m at the stage where I’m about to purchase the expensive stuff and I have some questions (despite all the fantastic guides I’ve seen on this forum).

The first question is pretty stupid and demonstrates my level of knowledge – it’s not in the guides because I presume it’s already obvious to everyone… but… what type of wire should I be using to actually connect the driver to the binding posts (inside the sub)? Is there a specific type?

Speaking of binding posts, I’ve been looking at getting some of these: Dayton Audio BPA-38G HD Binding Post Pair Gold as they’re available from a seller close to where I live, and simply drilling holes in the bottom of my enclosure, next to the driver and caulking them closed after inserting the posts. If that seems like a bad idea, please flag it.

I have a Denon X4400H AVR that I plan to hook up to the subwoofer amp. Probably one of the inukes since they’re cheaper and readily available in Europe. And my second question is therefore amp related, because I really, really don’t want to blow anything up later….

I’m at a loss to understand some of the power implications….. I need an amp with sufficient power to run a single DVC sub, with enough headroom to accommodate a second one (potentially) in the future, but without blowing the first one right now….

Unless I’m mistaken and as per the specs in the link below, if wired in series, the UM 15 will have 4ohms resistance for +/-800w RMS. Does series or parallel make any real world performance difference – other than the impact on resistance? If you have enough power in an amp, is there any reason to do parallel?

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If I run it through a single channel off a NU1000 I get 300w per channel (at a resistance of 4ohms). Which seems underpowered?
https://static.bhphotovideo.com/lit_files/84919.pdf

If I bridge the coils and run it off both channels, then resistance halves and power doubles? So an NU1000 would push out +/- 500w per channel and the UM15 would have 2 ohms resistance per coil? Which seems a lot better.
However, it also seems to suggest that I won’t be able to add a second sub later without everything being underpowered.

Looking at the specs, the NU3000 seems like a better bet if I’m looking to future-proof. Sub-question 1: how do I protect the single sub if I go for the larger amp now? And sub-question 2: Does 14AWG (approx. 6ft) speaker wire make sense in this equation based on the wattage we’re looking at.

And finally (for now) a small woodworking question. I plan to put the sub on wooden feet with rubber dampening soles. Is there a specific height that makes more sense? Does it matter?

Apologies for the encyclopaedic length of my post. And thank you for responses to any of the above. Every little helps!
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Old 14th March 2019, 10:38 AM   #2
wolf_teeth is offline wolf_teeth  United States
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I don't think the NU3000/1000 is 2 ohm stable in stereo. More or less, I feel the 3000/1000 would likely be okay for the pair running 4 ohms on each channel. Just don't use the second one and keep the gain down if you don't have the second woofer.
The phrase 'underpowered' is kind of a misnomer in most applied usage. Some people think RMS power is what is required, but it is just a continuous thermal power rating. You do not have to use that much power if you have enough with less.

14 or 12AWG is fine for this application. I recommend Neutrik Speakons for your sub cabinets since the Inuke will have Speakon outputs.

Do not build a downfiring subwoofer with high-mass cone drivers such as the UM line, or they will sag over time and be performing less than optimum. Your best bet is to face them towards a wall or away from view. Bass is omnidirectional anyway so this will not matter.

I use the UM10 in a small PR-Bandpass, and have a 500W plate with 6dB of boost at 25Hz. I tend to not exceed 12-noon on the gain in my 13' x 15' (open back wall) room. With that in mind, between 500-1000 real watts per channel range at 4 ohms will likely suit your needs for 2x UM15-22 subs. If you get the DSP model, you can tweak the subs to better blend with your room.

Later,
Wolf
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Old 14th March 2019, 12:41 PM   #3
Elgreco31 is offline Elgreco31
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@wolf_teeth - many thanks for the response. I was not aware of the sag issue. This was very useful. Good thing it's still a work in progress!
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Old 15th March 2019, 12:34 AM   #4
cspieker is offline cspieker  United States
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Quote:
Originally Posted by Elgreco31 View Post

Unless I’m mistaken and as per the specs in the link below, if wired in series, the UM 15 will have 4ohms resistance for +/-800w RMS. Does series or parallel make any real world performance difference – other than the impact on resistance? If you have enough power in an amp, is there any reason to do parallel?


Looking at the specs, the NU3000 seems like a better bet if I’m looking to future-proof. Sub-question 1: how do I protect the single sub if I go for the larger amp now? !
Wolf is spot on,

I'll clarify a couple of things

You'd never want to wire the voice coils in parallel, because no amp can handle a 1 ohm load. Wire in series for a 4 ohm load and use only one channel of an amplifier. A plate amplifier would be great mounted in the box as they are always fanless and one channel. Your receiver probably does auto room correction anyway? If so, dsp would be unnecessary.

Going from no sub to this is going to blow your mind. Most people are proud of their tiny 8" bandpass sub from their home theater in a box. This thing is a serious subwoofer in a whole other league. 300 watts may be perfectly satisfying for you, but it's a shame to sell yourself short. If you get a more powerful amp, it is unlikely that you will damage the driver because that level of output will be extremely loud, but it is possible. If you hear it bottom out, it will make a loud crackling noise, immediately back off and you might not destroy it the first time. To be safe, look at the winisd model driver excursion, see at what power it exceeds xmax and select an amp with slightly less power than that.
If that's confusing, let me know.
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Old 15th March 2019, 12:38 PM   #5
Think is online now Think  Netherlands
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Dayton audio 15 inch UM sealed sub build
Wiring 2 drivers in parallel is preferred to wiring in series.
Wiring 2 drivers/woofers in parallel is ok as long as the combined impedance (ohm) is not lower then the amp is specified for.
Never wire different woofers in series, but with 2 coils on the same woofer it is ok to do.

Nu3000 and Nu4-6000 are 2 ohm stable.

Nu1000 should also be 2 ohm stable, so you can hook up each coil to a channel and send about 600W clean to the sub.

If you get a 2nd sub later, output will be about the same as doubling drivers gives +3dB and you lose 3dB with going from 2 to 4 ohm (coils in series) per channel. At home it will be way more then enough. Remember that doubling power only give +3dB (minus extra power compression)

You could also use 2x tpa3116 pbtl/mono boards or a dual pbtl stereo board (1 chip each channel/ coil) and get 200W clean out of it for $10 and an old laptop adapter.
You might want to add a simple variable low pass and volume control, which you can get for $5 on ebay as well. Not only cheap and good sq, but also fan less, so quit. Idle and active power usage will be so low, that it pays for itself.
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Old 15th March 2019, 02:09 PM   #6
cspieker is offline cspieker  United States
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Excellent points. To be sure there's no confusion, because these particular voice coils are 2 ohms each, for this particular driver you won't wire them in parallel.

If those amps are 2 ohm stable, that's a nice solution. A lot of people shy away from running 2 ohm load even when amp is rated for it. For continuous high output PA use, it's hard on amps, but for use in your house I think it's perfectly fine because load tends to be less intense and continuous.

I happen to need an adjustable low pass filter for some bass shakers I'm putting in the theater. Do you have a link on the specific one? Thanks!
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Old 15th March 2019, 03:30 PM   #7
Think is online now Think  Netherlands
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Dayton audio 15 inch UM sealed sub build
Thanks, your advice was correct but TS might get the wrong impression about wiring is parallel as it is just no good in his situation as he ends up with 1Ohm.

In car audio 1Ohm stable amps are used. The inukes (not the nu6000 which is 2x nu3000 in bridge, 4Ohm) and tpa3116 are ok with 1.6Ohm and up. 2Ohm is fine for subs, but for tops/mains better use 4ohm or higher as the highs will suffer due to the class D output filters not being optimal for it, cable length and probably some more reasons.

Some low pass filters:
Single Power DC 9-32V Low Pass Filter Bass Subwoofer Pre-AMP Amplifier Board 665974429785 | eBay

or if you like to have main volume control on it: DC 12V-24V Low-pass Filter NE5532 Subwoofer 2.1CH/Pre-Amplifier Preamp Board | eBay

There is a cheaper one, but I have not used this one yet: Low-pass Filter NE5532 Bass Tone Subwoofer Pre-Amplifier Preamp Board DC 12-24V | eBay

And TPA3116 mono TPA3116 D2 DA DC 12V 24V 100W Mono Channel Digital Power Audio Amplifier Board | eBay

Warning: These are advertised as 2x120W but I guess this is not true due to the pictures only showing 1 chip on the bottom side. So probably just 2x50w@4ohm. 12V-24V TPA3116 D2 120W+120W Dual-channel Stereo Digital Audio Power Amplifier | eBay
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Old 15th March 2019, 03:47 PM   #8
cspieker is offline cspieker  United States
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Thanks! Exactly what I needed.
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Old Yesterday, 07:25 PM   #9
Elgreco31 is offline Elgreco31
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Thank you all.
I finally pulled the trigger on a nx3000 (non DSP) and will follow the advice to wire the coils in series off one of the amp’s channels.
But still got a little way to go before I get to that stage and will undoubtedly have more basic questions before I’ve finished!
Thanks again
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