IB for under $30/L?

[zbigb]

They are 10" small. However 12 to 14 of these in a 12" x 12" x 80" tall manifold could provide decent displacement. One of the 80" sides could face the opening to keep the distance to the listening area somewhat equal.

Here are some specs:
SD = 340
Xmax = 13mm (The holidays are over now, no Xmas:))
Qts = .394
FS = 23.1 Hz
150 Watts (EP)
Impedance 12ohms
VAS 82.15L
Outside Diam. 10.25"
Depth 4.75"

I built a vented sub using two of these last summer. Unfortunately, I did not verify the specs After break in I did check the calculated impedance for the cab they were in and it matched the predicted (Bass Pro) repines within 1 Hz.

Any thoughts/comments as how they may apply for IB use?

[ThomasW]

The way to know if any given driver will work in an IB is to compare it's T/S parameter to those of drivers commonly used in IBs.

[zbigb]

OK: Comparing these to the available Driver list: www3.sympatico.ca/bonaz/IB-Sub/IBdrv-01.htm

SD (cm^2) = 340. This is a little guy, lowest on the list in this column.

Xmax = 13mm, It’s not a SoundSplinter, but 1.3mm away from a PE/Dayton IB15"

Qts = .39 Some prefer .6, but .39 is certainly higher than many of the units in the list. Wouldn’t this result in a lower group delay than a higher qts? (Less muddy, tighter response)

FS = 23.1Hz A bit high, but in the ball park again. I understand IB’s live under FS anyway.

Efficiency (dB) = 84.5 Low, but not significantly low for IB. Being a small driver, one would expect it to be lower all other things being equal.

An issue with a smaller driver is that you will be doing a lot of hole cutting. With four 15” drivers: 4 drivers*15” diam.* 3.14 = 188 linier inches of cut.

Assuming four 15” drivers provide 10 to 11 L of displacement, 12 of these 10” drivers are needed to keep up. With twelve drivers: 12 drivers *10” diam. *3.14 = 377 inches of cut. (Over 31 feet!)

On the other hand, these units are only 4.75 inches deep. The shallow depth can come in handy in tight situations. Twelve can be mounted facing each other (to cancel shaking forces) on 12” x 12” x 74” column manifold. Keeping one 74” side open, this manifold fits into the basement-separating wall nicely. How about two 74’ columns, one on each end of the room ……

These drivers provide only .884L of displacement each, but at $25 each, that works out to only $28.28/L. Lowest in the comparison column too. It seems this is this is the reason to avoid smaller drivers, but not in this case. Twelve provide similar displacement as four 15” IB drivers but cost less. $300 for 10.5L.

If you compare this to an 18” driver with a 23mm Xmax, the 18" would have to be priced at $157.50 to match this little guy.

Am I missing any other TS parameters or other considerations relevant to IB’s? I was planning on getting a dozen, but concerned that I am missing something. Feedback appreciated!

[ThomasW]

Am I missing any other TS parameters or other considerations relevant to IB’s?

Nope.

Feedback appreciated!

If you have copious amounts of free time, and understand the fact that doing this is going to involve significantly more work and materials than a 4-15" line array, you're good to go.

[fvoelling]

What kind of amplification do you need for something like this, and would it be significantly different for a 4 x 15" IB?

Frank

[zbigb]

I was planning on starting with 350 watts to drive 14 of these, only because I already have a 350 watt amp. This is for a 2100 cubic foot room. I can always bump up the amp to something bigger if needed. These will need equalization., so a Behringer DSP1124P will be used.

I estimate these could take 550 watts, but I do not plan on driving them that hard. I do not believe the amp would be significantly different from four 15" of similar displacement, but I'm new to IB's and making some assumptions.

[ThomasW]

What kind of amplification do you need for something like this, and would it be significantly different for a 4 x 15" IB?

It's all about displacement, compare the Vd aka swept volume (Sd times Xmax doubled) for multiple 10"s vs 4-15"s.

With any doubling of the number of drivers one gets +3dB more output (this is called acoustic or mutual coupling). And if the amp doubles down (twice as much power for every halving of impedance) you get +3dB more output.

[mannthey]

Maybe I missed something somewhere. Do you have a link to the drivers you are talking about or is this some local source you have for $25 drivers?

[zbigb]

It is national source.

If you are buying 12 or more the price for these is $25 each. The woofers are made in Japan for NHT. I think by Tonegen, but not sure. I obtained mine directly from an importer, AB Tech Services. The contact email address is [e-mail].

Madisound sells these individually and the driver is described in this link:

www.madisound.com/nht10subkit.html

I bought two last July for a ported sub I built, and sixteen more for an IB project in my basement. 16 of these provide 14L of displacement for $400. The trade off is I will be eternally cutting of holes:) These are significantly more work than 4 large subs and you will use more hardware. In my case, I am working around some restrictions so the smaller size is a plus. If you don't mind a lot of sawdust and some extra hardware, these are a bargain.

I will report out on how they work in an IB, but I am just getting started on finishing the entire basement, so it may be a while.

[ThomasW]

If these have similar complete T/S characteristics to the 1259, they're not intended to be used in anything other than a small sealed box. This is due to the fact that the driver has very compliant suspension, it needs the 'air spring' of the small box to keep the cone motion linear.

[zbigb]

Thomas,

Before we continue, I just wanted to say thanks for the well run and informative website. This is a real gold mine for IB info. I am new to this forum but have been trying to read as many posts as I can the last few days. Thanks to everyone!

The only T/S parameter this driver shares with a 1259 is the Xmax. I compared suspension related paramters for woofers in the available driver list.

The suspension compliance, Cms does show this driver to be much lower than a 1259, but a bit higher than a Stryke IB 15. The Vas is much lower, but this is a small speaker. The Cms did appear to be a bit higher than many of the others in the comparison. I compared several drivers, but I did not know how to post the spreadsheet, so I just grabbed three examples

The Rms, mechanical resistance of a driver’s suspension losses, is much lower than the 1259 and lower than the Stryke IB.


................RMS........Cms................Qes............Qts
1259........5.112......0.7404............0.53...........0.445
NHT 10"....3.657......0.506..............0.44...........0.394
Stryke15...4.460......0.455..............0.48...........0.437


The Qes is lower than the Stryke, but balances the softer Cms. The softer Cms and higher Qes do result in less ridged suspension, but again do not appear out of the ball park.

The Qts is lowest of the three, but as discussed earlier in the thread, higher than many in the list.

Too soft?

[ThomasW]

That looks okay, it's not nearly as soft as the 1259, which was the primary concern.

[mannthey]

zbigb and thomasw,
Thanks for looking into this driver and going overs it's specs I am seriously considering ordering these drivers for my ib.

[mrw]

Did anyone ever try these out?? Just wondering.

W

[zbigb]

Yes. I have 16 of these powered by a Apex Sr plate amp. I had to put the project on hold due to some family health issues, but did get as far as temporarily connecting them to test for nulls. They were not equalized but even without eq the sound bass incredible. The bass is clean, tight and low but it does need eq. These can probably take far more power, but play more than load enough for me. I want to optimize what I have first when I can get back to finishing the room. These do need equalization as most IB's

[mrw]

Looks good. I need these shallow drivers in order to set mine up. Thanks a lot for your input, everyone.

w