sub transducer sizes

[johndenim]

I have been thinking about this for a while.

 

I have also noticed that a few companies are bringing out 21" drivers in their subs.

My question is why?

Would a 21" driver go lower?

What about x2 15"?

Or even x2 18" for that matter?

 

Available are subs or twins of 12", 15", 18". Is there a x2 21" out there?

 

If someone could explain the differences please that would be great.

[Killyp]

Funktion One makes a sub with 2x 21" drivers - 106dB/1w down to 40 Hz ;) They make a horn for it as well :unsure:

 

From my (limited) experience, a dual 18 will generally give a bigger 'kick' improvement over actual musical sound when compared to a dual 15, but with single drivers, the difference between 15 and 18 seems to be bigger. I've never used a 21" sub, but have heard them, and while they do feel like they're going to tear your clothes off, I didn't think it sounded any louder.

[Charlie Jeal]

Danley Sound labs also have a new 2 x21" sub and there's also the Adamson T21.

[johndenim]

Hmm, you are correct on the Funktion one subs, for some reason their opening statement is " 30hz and below" yet the F- 221 sub is rated at only 106dB and 40-280 hz?

[TomHoward]

Opus Audio make a 2x 24" sub, the UB224. I've seen them in the flesh but they don't seem to be listed in their product catalogue, although they are on the listed on the product section of the web site.

 

[Edit] Link

[Killyp]

Hmm, you are correct on the Funktion one subs, for some reason their opening statement is " 30hz and below" yet the F- 221 sub is rated at only 106dB and 40-280 hz?

 

The opening statement is probably referring to ±6dB measurements, wheras the statement on the spec sheet is ±3dB (at a guess).

 

Opus Audio make a 2x 24" sub, the UB224. I've seen them in the flesh but they don't seem to be listed in their product catalogue, although they are on the listed on the product section of the web site.

 

[Edit] Link

 

232 kg!! I'll have nine.

[johndenim]

I didn't even know a 24" driver existed!

 

Wow, what's next, 27"? 30"?

 

Edit*

 

23hz? that's low!

 

Does the dB scale still apply when we get down here?

 

 

"Fittings: 4 x Metal bar handles"

 

haha, what, 1 for each fork lift? :P

[Killyp]

Yup, dB still works in just the same way. As you get below 20 Hz though the amount of energy required for the ear to hear a sound increases massively. At 16 Hz, the energy required is something like 114 dB, which is neigh on impossible to reproduce, although I have heard some (consumer) speakers which will do it. Useless for PA applications really...

 

EDIT: I was aiming a little high, at 15.5 Hz, you need 92 dB with 12.3 dB/oct slopes below that.

[csg]

I think that transducer size very much depends on your application and requirements - but it also depends massively on the enclosure type being used.

 

If you are using reflex or bandpass loading techniques then I would reccommend looking at larger diameter units - these, by virtue of their larger surface area will couple to the air more efficiently, so they can transfer the engery they are producing in a more effective manner.

 

However, when you start looking at horn loaded techniques, there is now a very strong argument for employing smaller diameter units ( my current preference being for 12 " drivers). A well designed horn will provide an effective impedance match between the driver and the air, and will improve efficiency considerably. Having a smaller driver can allow you to fit a longer horn path length inside a reasonable sized enclosure, giving the benifit of a lower cutoff frequency, but also a faster impuse rise time due to the lighter transducer diaphram. This will give you a sub that can play low, and maintain a fast articulate sound.

 

Where funktion one sub enclosures differ is through their use of short bandpass horn enclosures. These are a combination of a 4th order bandpass enclosure, where the front volume vents to a horn with a short path and high expantion rate. This style of enclosure requires a larger diameter driver to achieve good efficiency, hence the 18 and 21 inch options.

 

The 24" driver used in the opus sub has its origins in another Tony Andrews design - the turbosound TSW124. The driver is made by precision devices.

[paulears]

What exactly goes through the subs? If they are 15" ones, then as they go a bit higher, the crossovers will let the kick drum and the lower two strings of a 5 string bass plus perhaps and synthesised low bass to be 'supported'. Move to 18" drivers and you're left with the B string on the bass, and a bit of the very left hand end of the synth keyboard. Go bigger still and its pretty well the 'duh' of the kick. This assumes the kick drum itself is a big one. Big kick drums shift a lot of air - when teaching, we used to demonstrate this with a lighter being blown out through the mic hole in the front skin. There seems little point having subs with bigger surface area than the kick drum. To get the gut tingling thud, their ability to shift air very quickly is the key. Sonic performance can't be measured in the same way as ordinary wider range sound quality can - you can't really listen to a sub, you feel it in the diaphragm.

 

To even consider huge drivers, huge boxes and the extra weight, you'd have to really need mega power at frequencies you can't hear? I guess that if Metallica need them, then others may do too - but how many of these beasts and their amplifiers can ordinary people afford?

[drsound]

The 21"+ drivers are probably better suited to installs in large scale non-live (ie club) venues than to live touring use as a rule. I guess if you're spending half a million quid on your PA just to let some ludicrously wealthy shell-suited monkey who looks like he might have just nicked your telly play other people's music then it's worth spending a bit extra just to recreate one note on one track at an SPL capable of shattering kidney stones.

 

Not my type of gig as you may have gathered... :P

[Doug Siddons]

Slightly OT but I once spent an afternoon with a customer who wanted to reproduce the sound of a church organ, the lowest notes coming from a 32' pipe. Trying to demonstrate a box reproducing these frequencies and prove that it is when you can't even hear them ( or not at my age!) was challenging. Same applies for the top end as well :P

[Stan Hope-Streeter]

<br />I didn't even know a 24" driver existed!<br /><br />Wow, what's next, 27"? 30"? <br /><br />Edit*<br /><br />23hz? that's low!<br /><br />Does the dB scale still apply when we get down here?<br /><br /><br />"Fittings: 4 x Metal bar handles" <br /><br />haha, what, 1 for each fork lift? <img src="style_emoticons/default/tongue.gif" style="vertical-align:middle" emoid=":P" border="0" alt="tongue.gif" /> <br /><br />

 

ElectroVoice were making 30" woofers in the 1970's. The Royal Exchange in Manchester had some for sound effects.

 

There were several manufacturers in the 80's offering large drive units, the best known probably being Mitsubishi who made them up to 60" diameter.

 

The applicatons are rather limited and consequently there isn't a large market for them, so they were always expensive niche products.

 

In most cases a horn loaded system using smaller drivers is far more efficient and cost effective, provided you have enough room for it. If a direct radiator is essential, you can get the same results using multiples of 18" or smaller drivers.

 

One difficulty with all oversize (18" plus) woofers is that it's difficult to design a suspension that will not sag, over a period of time, with the heavy weight of the cone. The old Turbo 24" used to suffer badly from this as did the 21" when used in fixed installations. It was essential to turn the drivers in the cabinets every few months to even out the wear on the suspension.

 

Makes for an impressive looking hifi or studio monitor though...

[johndenim]

So the reproduction of LF is based on the frequency?

By that I mean an un amped kick drum would produce x frequencies, so a sub the same size would be appropriate?

This would matter in comparison to the physical size of the sub?

 

In other words a larger diameter driver can or should go the the bottom end of our audible range?

 

Why not have x3 10's or 12s?

Or 4?

Would anyone say that a x2 15" sub would be better that a 18"? same make and model of course.

Lots of questions I know!

[mostlyharmless]

B&C have made a new 21" driver - hence everyone putting it in subs all of a sudden!