Micro Sub using ND105 4" driver

[Fastskiguy]

Re: Micro Sub using ND105 4" driver

The baby sub project caught my attention and I have something going. It's the nd105 4" driver with a 25 watt amp in a box...inside measures 21.5mm per side so just a little under 10L volume and a tube for the port...7" long and 1.5" ID. I have the baffle taped in place and just held an old sock around the port to get an idea of how it sounds. It's...not exactly loud but it adds a fair bit of bass to the pair of realistic minimus 7 speakers I'm going to use with it. What do you think? Seal this baby up and get rockin'? I'm asking because....I don't really understand all of those fancy charts LOL. Thanks guys

Joe

[bkeane1259]

Re: Micro Sub using ND105 4" driver

What do you think? Seal this baby up and get rockin'? I'm asking because....I don't really understand all of those fancy charts LOL. Thanks guys

Did you line the box interior with egg-crate foam or something similar? If you have that sub up on your desk facing you, you might get unpleasant midrange leakage from that port. You can compensate by adjusting the XO point on the amplifier down below 80Hz, but with a driver that small, you'd probably want to have a higher XO point.

If you tuck that sub under your desk, it will help mask port leakage problems also.

[DanP]

Re: Micro Sub using ND105 4" driver

If your amp is a subwoofer amp with a lowpass (usually at least 18dB/octave), you shouldn't get any midrange leakage, so no lining or stuffing is necessary. This will definitely dig deeper than your Minimus 7s, which I think run out of steam at about 120Hz. Box size and port dimensions look good, so close it up and let her rip.

Dan

[diy speaker guy]

Re: Micro Sub using ND105 4" driver

Also had another idea. What about a mini version of lilmike's tapped horn design? I mean, the whole thing would have to be smaller, but this driver might work for that. I guess more analysis of the driver's parameters would have to be done. There's also 4th order bandpass, and push/pull type enclosures to think about.

This should give you an idea of what's possible. All 3 designs use the same nd105 and are shown at 4 mm excursion, all shown corner loaded. The light line in the first graph is ported (approx. 9 liters), the dark line in the same graph is a tapped horn (approx. 40 liters), and the second graph shows a larger front loaded horn (approx 80 liters). (Note that the large front horn is tuned a couple hz higher than the others, but close enough, I don't have time to make this a perfect comparison.)

The tapped horn doesn't seem to have much advantage over ported, but the tapped horn (and the larger horn) take less power to reach xmax and have no small port, so the horns will not suffer nearly as much from power and port compression, so in the real world it wouldn't be so close.

None of these are particularly good designs, not optimized at all, only presented as a rough example of what the driver can do. Personally I would never use this driver as a sub but to each their own.

[bkeane1259]

Re: Micro Sub using ND105 4" driver

If your amp is a subwoofer amp with a lowpass (usually at least 18dB/octave), you shouldn't get any midrange leakage, so no lining or stuffing is necessary. This will definitely dig deeper than your Minimus 7s, which I think run out of steam at about 120Hz. Box size and port dimensions look good, so close it up and let her rip.

Dan

Dan is right. Even the Dayton SA25 has a 2nd order (12 db) low pass. So you should be fine. He's also right about the M-7's. Even with the famous Zilch XO mod, they are really only useful down to about 100Hz. BTW - I'd highly recommend that XO mod. It makes a huge difference in the midrange with those classic speakers!! RIP, Zilch.

[Fastskiguy]

Re: Micro Sub using ND105 4" driver

You guys are awesome, we've got opinions, graphs, and even some bonus info on the minimus speakers! Yes it's the dayton sa 25 amp and it's going under the desk. I think we are all set here, it's a wrap. Thanks again

Joe

[Fastskiguy]

Re: Micro Sub using ND105 4" driver

And here we have it. It's not loud but it sounds pretty good. A bit of port noise ( I think) at about 35-40hz. It goes 10hz lower than my inexpensive commercially made 15" sub! So I'm please, it was fun and it'll sound good for a long time

Thanks again everybody

Joe

[Fastskiguy]

Re: Micro Sub using ND105 4" driver

Here's the back...and a hand for scale ;)

[Chris Roemer]

Re: Micro Sub using ND105 4" driver

And here we have it. It's not loud but it sounds pretty good. A bit of port noise ( I think) at about 35-40hz. It goes 10hz lower than my inexpensive commercially made 15" sub! So I'm please, it was fun and it'll sound good for a long time

Thanks again everybody

Joe

Next time, run the vent out the back, even if you have to put the amp on the side. Chuffing will be less noticeable that way.

[greywarden]

Re: Micro Sub using ND105 4" driver

With 12 of these, you could replicate the BG RADIA in-wall subwoofer and still be about $4k under budget haha...

http://www.bgcorp.com/PDFs/Support/BGX-manual%2004302010.pdf

[Fastskiguy]

Re: Micro Sub using ND105 4" driver

Next time, run the vent out the back, even if you have to put the amp on the side. Chuffing will be less noticeable that way.

I'll do it, thanks for the tip

[stan]

Re: Micro Sub using ND105 4" driver

With 12 of these, you could replicate the BG RADIA in-wall subwoofer and still be about $4k under budget haha...

http://www.bgcorp.com/PDFs/Support/B...2004302010.pdf

Haha, that made me think of the old Sweet 16. Man, 16 ND105's per channel would move some air, wouldn't it? Here is a link: http://www.roger-russell.com/columns/columns.htm#sweet

Even 9 per channel, ala Blose 901, would move some serious air.

Stan

[Chris Roemer]

Re: Micro Sub using ND105 4" driver

Haha, that made me think of the old Sweet 16. Man, 16 ND105's per channel would move some air, wouldn't it? Here is a link: http://www.roger-russell.com/columns/columns.htm#sweet

Even 9 per channel, ala Blose 901, would move some serious air.

Stan

I've thought about the 901 configuration. You wouldn't need the massive EQing (like the 901s) to make bass with these babies.

I've estimated that one ND105-4 is equivalent (in swept volume) to a pair of 5.25" or a single 6.5" Classic.

A pair (like in my ntns) is equivalent to a pair of 6.5's, or a single 8".

A quad is like a pair of 8's, like the "Dayton 8".

16 would be equivalent to a 12" sub with 15mm Xmax, or a 15" w/9mm Xmax.

Of course, they'd cost $430 for a set, maybe $240 on sale. Also, they'd need 5 cu.ft. Makes the RS Subs look pretty good.

[Taterworks]

Re: Micro Sub using ND105 4" driver

Things I've thought about, but will probably never do:

A Linkwitz-transform sealed slim subwoofer (similar to the BG Radia sub concept) with eight ND105-8 in two vertically-stacked groups of four, facing each other, radiating out of both 'sides' of the enclosure - about as much cone area as a 12" driver...

A version of the Bose 901 using the Bose replacement drivers with eight in a vertical line on the rear of a tower enclosure and one driver on the front at ear height, DSP-eq'ed, called the "Line-Oh-One"

There are just too many 'so-so' ideas out there, and I'm the kind of guy who's easily swayed by novelty. I'm only 26 and I'm realizing I'm never going to build all the speakers I'd like to build, so I try to stick to only the very best ideas and consign the rest to the "Maybe Someday" pile...

After hearing the ND90-based "Kenny" micro-sub at Kentucky, I have a lot of respect for what the Neo-Sym drivers are capable of. However, I also agree that a sub is probably a waste of their capabilities, since they can cover such a broad range while remaining clean from bottom to top.

The reason for the copious vent chuffing with the sub designs using these drivers is that they are mid-Qts drivers, and that means that vented alignments using them will be '6th-order' vented alignments where the output from the vent will be more energetic, because the driver is less damped and so it provides less damping to the vented system as a whole. This also means that the bass may be fairly boomy, but this doesn't seem like that much of a problem in a subwoofer where your ears are less sensitive to the time domain in that passband anyway. This type of alignment probably wouldn't work well for accurate, 'tight' bass in a larger enclosure, but you'd definitely get the 'gee-whiz' effect from the overall level and depth of the bass.

[greywarden]

Re: Micro Sub using ND105 4" driver

I have all sorts of rediculous ideas all the time too, don't worry, you're not the only one, haha.

I've even drawn out detailed plans for a copycat of the RAAL omni's :o I only got discouraged when it came time to attempt simming them, haha.