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Tuning below Fs with JBL 2226H? [message #75301]

Mon, 21 January 2013 03:53

Omholt
Messages: 7
Registered: January 2013
Location: Norway

Esquire

I'm considering building two bass units in vented boxes for a two channel setup. I want something that can be crossed over in the 200-250 Hz region. The JBL 2226H is considered a fine driver for midbass.
At the same time I would like good ouput down to about 25 Hz.

The plan would be to start with two stacked drivers on each side and increase with three or four later if it's needed.

If the cabinet is large enough, using several drivers on each side and I have enough watt, is tuning to around 25 Hz problematic and a compromise? The Fs of 2226H is 40 Hz.

Is it better to use a driver with lower Fs? What would be recommended in that case.

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Re: Tuning below Fs with JBL 2226H? [message #75305 is a reply to message #75301]

Mon, 21 January 2013 09:27

Wayne Parham
Messages: 18792
Registered: January 2001

Illuminati (33rd Degree)

The JBL 2226H is one of my all-time favorite midwoofers. And it is capable of producing subwoofer output too, but it is not optimized for that purpose. Most of the things that make it great - its motor structure with shorting rings, it's highly damped cone, it's efficiency - all work best above 50Hz.

So while you can make a good subwoofer using JBL 2226H drivers, I would prefer to use JBL 2235 or JBL 2245 woofers instead. They are tuned for subwoofer use. Another option is the LAB12, which allows me to build a very competent subwoofer in a 4ft³ box, which is much smaller than what is required for the JBL subs. The LAB12 sub is not as efficient though, naturally, because size is king where subs are concerned. According to Hoffman's Iron Law, the only way to get efficiency and deep bass extension is to use a large box.

Still, since the most important thing for good quality bass is to use several distributed subs placed around the room, I find it pretty important to have subs of reasonable size. I think some people would think even 4ft³ is large, and so for them, 8ft³ to 10ft³ cabinets are out of the question, especially in multiples. But for me, 4ft³ subwoofers aren't too large. I run a pair of them flanking the mains, and another pair behind the seating area, and this gives incredibly smooth bass response throughout the room.

Room modes, multisubs and flanking subs

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Re: Tuning below Fs with JBL 2226H? [message #75306 is a reply to message #75301]

Mon, 21 January 2013 10:10

Omholt
Messages: 7
Registered: January 2013
Location: Norway

Esquire

Thanks for the reply.
So basically it can work quite good, but it's not optimal for subwoofer range and there are better options for that.

I have been recommended JBL 2234 as a first choice for this (or 2235 as a second option), but they seem practical impossible to get hold of. Or am I wrong?

Starting with four units, I will have the possibility of trying the multiple subwoofer approach as well. From what I've tried up till today though, I have had problems with integrating woofers in the back of the room. The bass hits the back of the chair, so I end up feeling it. Maybe the room is to small for that.

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Re: Tuning below Fs with JBL 2226H? [message #75308 is a reply to message #75306]

Mon, 21 January 2013 11:27

Wayne Parham
Messages: 18792
Registered: January 2001

Illuminati (33rd Degree)

The 2234 is the exact same as the 2235, except the 2235 cone is 35 grams heavier. It is literally the same speaker with a 35g mass ring added, specifically to increase bass extension. So I personally would prefer the 2235 over the 2234 for subwoofer duty. But either driver can be used to good effect.

I suppose the real problem is the 2234 and 2235 are both out of production, so you would have to buy them used and have them reconed. This is not so bad though, because reconed JBL 22xx drivers are good as new, provided factory recone kist are installed by a competent technician. They're designed to be serviced, and factory support is good.

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Re: Tuning below Fs with JBL 2226H? [message #75310 is a reply to message #75308]

Mon, 21 January 2013 12:00

Omholt
Messages: 7
Registered: January 2013
Location: Norway

Esquire

You also mentioned the JBL 2245 which is an 18" driver.
I would prefer 15" due to size, but would open to 18" too if it works better.

What about the JBL 2242 which is easily available? Fs of 35 Hz, so a little lower.

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Re: Tuning below Fs with JBL 2226H? [message #75311 is a reply to message #75310]

Mon, 21 January 2013 13:04

Wayne Parham
Messages: 18792
Registered: January 2001

Illuminati (33rd Degree)

The JBL 2242 is an awesome prosound sub. But for home hifi and home theater, I would prefer the JBL 2245. Then again, the 2245 is no longer available, so the 2242 might be a better choice, simply because of that.

These are all prosound drivers, and all are suitable as prosound subs. In a 10ft³ cabinet tuned to 30Hz, the 2245 is flat as a ruler, strong all the way down. The 2242 in the same cabinet has a bit of an EBS alignment, which is fine. Both are awesome. Still, if I had them both available to me, I personally would prefer the 2245.

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Re: Tuning below Fs with JBL 2226H? [message #75312 is a reply to message #75311]

Mon, 21 January 2013 14:21

Omholt
Messages: 7
Registered: January 2013
Location: Norway

Esquire

Thanks you again. 2245H could be option instead of 2226H. Should work better for the deepest frequencies.

Do you have experience with B&C drivers? A little lower sensitivity and will need more power which could lead to higher power compression, but overall they look promising.
http://www.bcspeakers.com/product.php?id=162

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Re: Tuning below Fs with JBL 2226H? [message #75313 is a reply to message #75312]

Mon, 21 January 2013 15:04

Wayne Parham
Messages: 18792
Registered: January 2001

Illuminati (33rd Degree)

Yes, I've used B&C drivers. In fact, I am currently using one of their compression drivers in my line of loudspeaker products. Their woofers are also good, but I don't think they're as good as JBL.

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Re: Tuning below Fs with JBL 2226H? [message #75317 is a reply to message #75313]

Tue, 22 January 2013 09:58

Omholt
Messages: 7
Registered: January 2013
Location: Norway

Esquire

Isn't lobing an issue when stacking bass drivers where distance is greater then 1/4 of the wavelength? If it is, crossing over as high as 200 Hz would be problematic. And that's the same for spread out units too.

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Re: Tuning below Fs with JBL 2226H? [message #75318 is a reply to message #75317]

Tue, 22 January 2013 10:21

Wayne Parham
Messages: 18792
Registered: January 2001

Illuminati (33rd Degree)

Lobing from acoustically distance sources is undesirable, that is true. It is to be avoided where possible, and outdoors or in very large areas, you want point source summing, which is accomplished by keeping source locations within 1/4λ, just as you've said.

But this is impossible to achieve indoors. Boundaries are further than 1/4λ away, so point source summing loses meaning. The reflections are out of phase with the direct sound. Even a single source gets interference from its reflections, which are nearly as loud as the direct sound. The result is deep notches at some points in the room, with hot spots in between them.

Sound energy distribution is like a checkerboard of hot and dead spots, and the pattern is frequency specific. At low frequencies, in what is called the modal region, there are large, widely spaced nodes. As frequency goes up, the number of nodes increases and distances between them become smaller. Eventually - at the Schroeder frequency, approximately 200Hz or so - the nodes become so closely spaced they cannot be distinctly identified. This is where the energy distribution becomes more of a statistically averaged sound field.

Room modes are the reason to use a multisub configuration. It is done to smooth the sound field at low frequencies by making sound in the modal region act more like the statistical region. For more information, see the link below: