At last! My greatest subwoofer is complete! 4 driver, 15", custom IB install! PICS!

I might sound a bit proud about this, but believe me, it was worth the wait. The subwoofer was a part of the house remodeling project from the very beginning, and as such, the room, floor and structure was created *around* it. All for cheap, too!!!!

It's a 4 driver, 15" C-V HED-15 based subwoofer. During testing, I powered it with a two channel Rotel RB-1070 amp. I removed it because a) I needed it to power a pair of DM-602's, and b) I couldn't stand the volume - and the amp wasn't even close to clipping! To put this into perspective, I'm now running the sub with "barely" 200W of power (a pair of Audiosource monoblocks). That's the beauty of DIY - since you are not constrained by economic or marketing limits, you can do a lot more with less (that, and it also helps that the manifold may be rated at around 94-96 dB / watt!)

Anyway, the sound is absolutely incredible. If you have never heard an IB subwoofer, you really owe it to yourself to listen to one. The box disappears... it's the lightest, most precise, most accurate bass I've ever heard - but it hits incredibly hard in the lowest frequencies, too. I still have to calibrate my 24 band parametric EQ for the room, but that will take some time.

I still need to route the cables and tidy up the whole install. Actually, the only thing currently working is the sub

Anyway, some pics...

 

Here's the whole room, with my DIY screen, and the whole Energy speaker array. "The Incredibles" painting on the wall was painted by my dear wife

 

What is IB?

 

Excuse me but, do you have a license to own and operate that thing

Congrats....enjoy

 

Very nice, Javier!

Judging by the screen and the wire dangling from the ceiling, i assume you are/will be using a video projector? I have an InFocus X1 and i love it.

 

How low can you go!

 

Infinite Baffle. It's a sub which doesn't have an enclosure - it just has a barrier that separates its front and rear waves.

It can also imply a subwoofer which enclosure is +10 times the Vas of the driver. In my case... my enclosure was my former swimming pool. No, it's not a joke...

 

Yes, that's one of the things that is missing. I have an Infocus, too! Great little projectors.

According to my simulation, the question of "how low can it go" is... F3 of around 23 Hz, without any kind of equalization, and useful output down to 16 Hz or so. With the parametric EQ, I think I'll shoot for a flat 20-80 Hz frequency response.

The only license I have for operating it is my marriage license.... and believe me, the first time I tested the sub, I was about to lose it.

 

Javier...i like how you think "out of the box". (No pun intended.)

I've heard of mounting a sub in the floor and using the crawlspace of the home as an enclosure. The downside is that you've got to be VERY certain about where you want it.

 

Thanks for the explanation.

 

Terrific work. You have every right to be proud.

 

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Thank you very much This was a very rewarding project, and one that (I think) I had in mind one way or the other for the past 10 years... I can only say I found DIY to be the most rewarding aspect of audio.

Yesterday, I made some quick sweeps using TrueRTA, to see how low could I really go. Without doors (those will come in later), I have a very pronounced dip on the 80 Hz range... but to my great surprise, I have excellent response down to 16 Hz, without any sort of external equalization! No wonder this thing sounds so good with so little watts - it has an amazing frequency range.

 

What is the dB rating?

 

According to my speakers' booklet, the manifold should be close to 96 dB/W.

According to my own calculations and measurements, its closer to 93-94 dB/W. Still pretty high (for a subwoofer).

With 200 W RMS, I can drive the whole manifold to XMax at around 14 Hz, so I'm not sure whether adding 200 " more is such a good idea. 200W is plenty enough to make the entire HT structure rattle like crazy, anyway.

I have tested the sub now with real music. Here's my opinion.

IB subwoofers have the best bass I've ever heard. No ifs, ands or buts.

I can't believe the quality of the bass I'm getting. It's as if the 6.5" woofers on my towers were covering the entire spectrum of music. The transition is seamless (mostly because the sub is longitudinally aligned with the mains), and the sub simply disappears. Once you listen to how a "boxless" sub sounds, you are hooked. I can't believe my Adire Audio Alignment DIY 15" Tempest (225L!) sounds so ugly next to this el-cheapo C-V sub.

If you have a chance... build this thing. I still can't get over how good this sounds.

 

I like the floor!

 

Tube time!!!

Are your speakers "fast"? Does the sub keep up with a "quick" monitor?

I don't know how I need to take some electronic courses.

How much do the parts cost?

 

Now you just need to build a second one so that you can have stereo subs!

I am sure the neighbors will love it

 

Are all 4 woofers in phase?

 

at the risk of sounding like an idiot, why four speakers? and is phase making sure that the positive wires are connected to positive terminals and vice-versa for negative?

 

Phase is a measurement of time. If the drivers are in phase, they are generating their waveform from the same starting point. This system is not in phase, their voice coils are not lined up. Polarity is +-

Don't worry, everyone gets phase and polarity mixed up. Most people say phase when they mean polarity. In the studio, I always laugh when someone says "hit the phase invert switch". I laugh and say, that little button is not going to turn back time You cant invert time, but you can invert polarity.

 

so how could you tell if it was out of phase?

 

The drivers are not lined up.

 

His design looks good, and should only have phase issues at higher frequencies. As long as he crosses over by around 100 Hz or so, he should be fine.

 

Hi,

While the sub is very efficient, I'd never run it using a tube amp. It thrives on current, and besides, I shudder to think how much money I'd need to spend for a tube amp that is comfortable driving a sub 4 ohm load at 100W RMS from 80 Hz down

Subs actually aren't really fast or slow - but the concept you are talking about is the Qts, or the propensity of the system to "ring". A "slow" subwoofer has a very high Qts, meaning that the system has an overshoot and ringing at its resonant frequency, and a sharp drop in frequency response. Basically, you get "one-note" bass and no real low frequency response. Most commercial subs have a high Qts, so that you think they are "powerful".

My sub has a Qts of around 0.659, meaning it's an overdamped alignment. A commercial sub may have a Qts of double that amount, or more. For comparison, a critically damped sub has a 0.7071 Qts, and its generally considered the most acceptable trade-off between frequency response and ringing. With such a low Qts, and the IB alignment, the sub is able to reach very low frequencies with a controlled roll-off at the lower end. It's a pretty "fast" sub, since there's no air pressure slowing down the cone motion. I'd say it'd make the perfect sub system for Maggies or MartinLogans.

It's a very easy to build project, too. Parts cost was around $300 for the 4 drivers, $200 for the cabinet, $250 for the amps, and $100 for the parametric EQ. $850 (plus labour, which I didn't carge to myself, thankfully) for the entire system.

Ugh, don't even joke about it! It was a fun project, but I'd rather not do it again The good thing is, the former swimming pool is basically a concrete room built into the house, so my neighbours won't be very bothered about my sub. Actually, they have wild parties every Saturday and Friday night, so I don't think they'll care that much about sub 20Hz frequencies coming from my home (they must be deaf by now anyway )

DaWoofer, yes, every speaker has to be in phase. If I tried to invert polarity or delay the signal to any group of woofers I'd basically cancel the entire system. Since low bass is mostly unidirectional, it's a must.

t3h, the reason why this sub needs four drivers is actually a very powerful one. While a boxed subwoofer is limited, mostly, by the current capacity of the windings and the termal capacity of it, an IB is limited by the excursion capabilities of the driver. Meaning that I lose quite a bit of dB's by doing an IB (my 2 vented 12" DIY subs have more output capabilities than the IB, although they can't go as low). In order to avoid having a wimpy system, you need to go with multiple drivers.

I think I could go a bit higher than that, since the manifold is quite compact and the bass wavelengths are quite large. Still, since my mains can handle quite a bit of bass, I used an 80 Hz crossover setting. I'd have liked to go lower than that, but it's the lowest setting my system can handle.