Subwoofers are named so because they're design is optimized to produce sub-bass in minimal space. Sub-bass being around 70hz and below. There's no rules that say it has to hit 20hz to be a subwoofer nor is there an upper frequency limit to define it. It is about what the driver's design was optimized for. This usually means heavy cones and stiff suspensions. Which I believe has a stronger correlation to a subwoofer's upper frequency response than inductance which is so often mentioned.
To clarify a bit for this topic, first off the cone's moving mass on its own doesnt define the upper limit of the driver. The BL factor is key to this and a driver with a high BL and Mms will be able to play higher up as long as VC coil inductance Le is low enough.
Another deciding factor is the air volume behind the dust cap. Some sub drivers use a large and heavy dust cap and the air cavity formed by the dust cap and pole piece can create a resonance in the lower mids which can muddy up the driver if forced to play above 100 hz or so. The impedance plot will show if there are any issues like this in the form of smaller peaks throughout the lower mids.
Suspension resonance can also ruin a subwoofer's sound if it occurs in the lower mids. This also shows itself with smaller impedance peaks in the lower midrange.
The way a driver is vented in its motor can have a negative impact on lower midrange performance and limit the sub's upper bandwidth and output level. Many subwoofers have airflow restrictions in the VC gap. While a tighter vent path around the VC can accelerate airflow to it and aid cooling, it can also cause very audible and unpleasant distortion in the lower mids at higher output levels. This is especially true with open baffle subs, since the driver rear motor is open and exposed, making restrictive VC venting more audible.
Higher VC inductance on its own can cause increased IMD in the lower mids at higher playback levels. The higher the Le and cone excursion are, the worse it gets as the VC rapidly changes inductance as it increasingly moves closer to and further away from the magnet pole piece.
A good example IMO of a decent LF driver that can do both subwoofer and midbass duties is the old Vifa M26WR09-08. This driver sounds great from the mid 20 to 300+ hz. I believe it has alot to do with the higher compliance, smaller dustcap and well engineered motor. That may be why Aerial Acoustics used this driver in their model 10T and Dunlavy also employed it in some of their larger models.
Another deciding factor is the air volume behind the dust cap. Some sub drivers use a large and heavy dust cap and the air cavity formed by the dust cap and pole piece can create a resonance in the lower mids which can muddy up the driver if forced to play above 100 hz or so. The impedance plot will show if there are any issues like this in the form of smaller peaks throughout the lower mids.
Suspension resonance can also ruin a subwoofer's sound if it occurs in the lower mids. This also shows itself with smaller impedance peaks in the lower midrange.
The way a driver is vented in its motor can have a negative impact on lower midrange performance and limit the sub's upper bandwidth and output level. Many subwoofers have airflow restrictions in the VC gap. While a tighter vent path around the VC can accelerate airflow to it and aid cooling, it can also cause very audible and unpleasant distortion in the lower mids at higher output levels. This is especially true with open baffle subs, since the driver rear motor is open and exposed, making restrictive VC venting more audible.
Higher VC inductance on its own can cause increased IMD in the lower mids at higher playback levels. The higher the Le and cone excursion are, the worse it gets as the VC rapidly changes inductance as it increasingly moves closer to and further away from the magnet pole piece.
A good example IMO of a decent LF driver that can do both subwoofer and midbass duties is the old Vifa M26WR09-08. This driver sounds great from the mid 20 to 300+ hz. I believe it has alot to do with the higher compliance, smaller dustcap and well engineered motor. That may be why Aerial Acoustics used this driver in their model 10T and Dunlavy also employed it in some of their larger models.
Anyone tried the Peerless XLS 10 (P830452) above the usual sub range? The first real wiggle in the published impedance and response plots is around 600 Hz.
That Peerless start to resonate rather strong at 350Hz (see frequency plot) so that is not a good id. It's the impendance and frequency (on and off axis) plot that tells how high you can cross it. That Peerless is usable to maybe 150Hz i think, except with a very steep crossover to lower the resonances low enough to make it irrelevant for the total outcome...
I tend to think that the current usage of "subwoofer" refers to a bass driver that is located away from the "main" loudspeaker box, and only reproducing low frequencies. Many drivers can be used either as subs or as main woofers in a large loudspeaker, it's just the usage that determines the terminology.
I have a pair of RSS315HF-4's that are sold as sub drivers, but have quite smooth response up to 1kHz. I have used them up to 250 with the 'main' speakers on top and wasn't mad at them at all. I considered them woofers. Now they are pushed to the walls of the room and crossed at about 75 Hz, and voila, they are subs.
Bill
I have a pair of RSS315HF-4's that are sold as sub drivers, but have quite smooth response up to 1kHz. I have used them up to 250 with the 'main' speakers on top and wasn't mad at them at all. I considered them woofers. Now they are pushed to the walls of the room and crossed at about 75 Hz, and voila, they are subs.
Bill
That line of Dayton drivers is nice. They have really good (quiet) motors and Alu cones. I'd consider them woofers too, not just subs.
The American made Dayton Titanic line is real nice, over 22 lbs of beasty sub. I'm putting the 10 inch mk lll I uploaded back there through its paces. I like it better than the Peerless XLS thus far. Too bad the titanic series stopped being produced.
The Dayton Audio RSS265HE-22 10" Reference Series looks pretty nice for an alternative. https://www.parts-express.com/Dayto...-Excursion-Subwoofer-22-ohm-295-290?quantity=
The Dayton Audio RSS265HE-22 10" Reference Series looks pretty nice for an alternative. https://www.parts-express.com/Dayto...-Excursion-Subwoofer-22-ohm-295-290?quantity=
Can I ask what it is you like better about the Dayton? And what sort of application for each? Their specs are a bit different - 0.44 Qts for the Dayton, 0.22 for the XLS. Dayton has more excursion, but quite a lot more inductance too.