2-channel audio only .. Sub or no Sub? - Page 4

I've used a sub in my system consisting of Energy RC-70 and Rotel components and I actually prefer the 70s without a sub. I just like how they handle the bass on their own, especially the bass drum.

Please folks,

Sub for music in a 250 ft room with Kefs XQ20: which one is better, a small one (8") or a bigger (12 - 15") one?

Using now a HK3485 (no bass management), but can add a capable AVR as pre-amp (Hk340).

My options are only Velodynes...

Thanks,

Edward

There is no reason for a properly ported sub not to reproduce all frequencies above the tuning frequency better than a sealed one. The one disadvantage of a ported sub is that the enclosure will be larger than a sealed one with a similar driver. Any talk about speed or "tightness" or.... is hogwash. The advantages of a sealed sub is all audiophile nonsense. I say this out of both experience and study. I currently have two subs, both DIY, both tuned with large passive radiators which are equivalent to ports. They are extraordinary sounding with clean bass from their crossover down to below 20Hz.
Edited by Theresa - 12/5/12 at 4:56am

The following lists the maximum undistorted SPL for a SOTA 8" driver (19 mm Xmax)

Hz SPL
20 90
30 97
40 102
50 106
60 109
70 112
80 114
90 117
100 118
130 123

Seems marginal for one device. 2-4 such subwoofers could be interesting.

In general subwoofer manufacturers seem to decline to provide actual data for driver Xmax. The above is a charitable view of what a very good commercial sub with an SOTA 8" drive can possibly do.

Just to review, the following is similar information for a SOTA 12" driver:

Hz SPL
20 99
30 107
40 112
50 115
60 119
70 121
80 124
90 126
100 127
130 132

Seems potentially useful but not spectacular. A pair could be interesting.

Just to review, the following is similar information for a SOTA 18" driver:

Hz SPL
20 110
30 118
40 123
50 126
60 130
70 132
80 135
90 137
100 138
130 143

Nice starting point!

The above is absolutely consistent with both accepted science and the personal experience of a great many. Given all of the nasty things that happen in rooms as a matter of course, small differences such as vented versus unvented, neither option of which is necessarily inferior sonically, tend to get lost in the struggle. Venting is more advantageous if electronic equalization is not used, because it provides more extended unequalized response.

How does this box behave compared to a ported box below the tuning frequency? Say if you want to EQ it up quite a lot in the ULF, say to play useful outputs in the 5-10Hz range?

The dynamic and distortion behavior of a speaker at any frequency below the point where it is mass loaded is dominated by the linearity of the cone's suspension and magnetic motor. I suspect that a vented enclosure may have a slight edge near the box tuning frequency, which in turn is near to but usually above the - 3dB point because cone motion is reduced at this point, and sound from the vent predominates.



In the picture about the blue line is the radiation from the cone which roughly tracks cone motion at low frequencies. You can see that cone motion is actually minimized around about 78 Hz. This corresponds to an area of low distortion. Instead of coming from the cone at this frequency, the sound in the room mostly comes from the port. Below the-3 dB point low frequency distortion rises pretty quickly because cone motion increases.

At 10 Hz the threshold of hearing is very high.



The threshold of hearing below 20 Hz is not generally given, but the green line shows a reasonable but not necessarily highly accurate extrapolation to approximately 95 dB @ 10 Hz.

As shown below merely having a barely audible SPL at 10 Hz requires at minimum a SOTA 15" subwoofer driver:

Freq SPL
10 95
20 110
30 118
40 123
50 126
60 130
70 132
80 135
90 137
100 138
130 143

If you want to enjoy 10 Hz, you might need a minimum of 4 SOTA 18" drivers and they would probably have to have some low bass boost!

Graphs between vented and closed boxes tend to show closed boxes winning in the ULF, do you mean they're wrong?

Yes, I have an active boost circuitboard in the plugin-slot of my active crossovers with quite some lift. For the theater, it's 6x12" sealed boxes, but that's to start with 12" diameter cones, not 12" baskets... and they're a bit better than the average SOTA. They are rated for >128dB @ 16Hz. (134dB peak)

(Use the same crossover for my stereo, but the room is not sealed so I can't get useful output all the way down, but the goal there was 16 so that's ok. )

BTW, I wouldn't call it audible - for me it's more a tactile experience when you drop below ~18.

I'm not going to dispute any well-known authority in this area.

Got one?

I can't find any, and that includes the Vance Dickensons Loudspeaker Design Cookbook which talks favorably about electornically boosted vented subwoofers (ca. page 82).

I'm not going to argue that, either. I call bass below 20 Hz perceptible and often very nice. Is it hearing? Is it feeling? It can be very nice and enhance the envelopment.

For any fellow readers who want to check that, his name is actually Dickason.