Anything better than a Tempest for $150?? (1 Viewer)

[Jack Gilvey]

Only advantage I see to the Tumult is a smaller enclosure.

And more clean output. According to Dan, Tumult can deliver the equivalent of three Tempests with a 10% THD limit. Still, I wouldn't bother upgrading if I already had a dual-Tempest sub, that's more output already than a human should experience.

 

[DerrickW]

Well, I did some emailing with Adire, and they believe that "In terms of real-world clean linear excursion, a single Tumult is equal to 3 Tempests." They've said this before. While most of the time I wouldn't believe such claims, in this case the XBL2 does stay more linear towards XMAX right? So two Tempests may get as loud, but it would take 3 Tempests to play as loud without sounding like @!#$ at the most extreme volume.

As far as Seth's analysis method goes, Adire Techs recommended the more 'traditional' method of inputting power into WinISD and then looking at the XMAX graph. Adjust the power until the XMAX reaches the maximum rated at the usable range of frequencies.

 

[Pete Mazz]

Regarding the 3 dB vs 6 dB....

If the subs (assuming seperate power sources) were stacked together they should couple and put out 6 dB more, although I've never tested it. If seperated, they would only sum to 3 dB more output.

Pete

 

[Ryan Schnacke]

I agree with Pete. If you double the number of woofers, the enclosure size and the input power then you will gain 6dB across the board so long as the woofers are close enough to be considered "in phase". It doesn't matter whether the enclosure volume is continuous or seperated internally. 3dB is gained by doubling the driver area and 3dB is gained by doubling the power.

The "coupling" that is necessary here is to be "in phase". If you build two seperate enclosures and put them on opposite sides of the room then you lose the acoustic coupling and you'll get cancellations at some frequencies. The result is that the frequency response at some frequencies will actually be lower than with a single sub. This is where cancellation dominates. But at other frequencies, where you happen to be in phase, you'll still get up to 6dB gain. It all depends on the position of your subs, your listening position and the frequency (wavelength, really) in question. Overall you'll get an average of +3dB or so with this kind of setup.

I have actually measured this with my two vented sonosubs. I do indeed get +6dB when they're in phase despite the fact that they are seperate enclosures.

 

[Rob Formica]

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If you build two seperate enclosures and put them on opposite sides of the room then you lose the acoustic coupling and you'll get cancellations at some frequencies. The result is that the frequency response at some frequencies will actually be lower than with a single sub. This is where cancellation dominates. But at other frequencies, where you happen to be in phase, you'll still get up to 6dB gain.
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You know that actually makes sense... thanks for clearing that up for me...

 

[Seth_L]

I agree with Pete. If you double the number of woofers, the enclosure size and the input power then you will gain 6dB across the board so long as the woofers are close enough to be considered "in phase". It doesn't matter whether the enclosure volume is continuous or seperated internally. 3dB is gained by doubling the driver area and 3dB is gained by doubling the power.

The "coupling" that is necessary here is to be "in phase". If you build two seperate enclosures and put them on opposite sides of the room then you lose the acoustic coupling and you'll get cancellations at some frequencies. The result is that the frequency response at some frequencies will actually be lower than with a single sub. This is where cancellation dominates. But at other frequencies, where you happen to be in phase, you'll still get up to 6dB gain. It all depends on the position of your subs, your listening position and the frequency (wavelength, really) in question. Overall you'll get an average of +3dB or so with this kind of setup.

I have actually measured this with my two vented sonosubs. I do indeed get +6dB when they're in phase despite the fact that they are seperate enclosures.

That unfortunately is not true. Two 110dB source when combined (in phase) do not equal 116dB. They equal 113dB. This is simple log math. You can't get around this.

In your room they seem to be coupled despite not being in the same enclosure. Good for you, you're lucky, but your results are not typical.

If you were to take you two subs put them in a large room you would only measure a 3dB gain when they're side by side because they're not acoustically coupled. If you're room is small enough and airtight enough that they act acoustically coupled even when they don't share common air behind the drivers consider yourself fortunate.

Seth

 

[PaulDF]

[Full excursion is what you should be concerned with. "Full power" is meaningless unless you're just looking for something to tell your friends.]

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I know the topic has changed since page 2, but I wanted to clarify myself.

Keeping under "full excursion" is a must, as I now know. I understand that.

What I meant by "full power" was preout +10 and plate amp gain set very near max. Obviously I was reaching full excursion at anything over a moderate volume level. Basically I was really overdoing it. The clack was only really noticable within < 4'. At first I just didn't pay enough attention! I also didn't honestly think the cone was moving far enough to be bottoming. I had thought that 250 watts was needed to push the Tempest to Xmax, but now I understand that less power is needed with my large enclosure size.

Which was my initial comment...

 

[Ryan Schnacke]

"In your room they seem to be coupled despite not being in the same enclosure. Good for you, you're lucky, but your results are not typical."

"If you were to take you two subs put them in a large room you would only measure a 3dB gain when they're side by side because they're not acoustically coupled."

My room is 20x30x10. That's 6000 cu ft not including the large openings into my front living room, dining room and hallway. Plus there's the door to the master bedroom that stays open 99% of the time. It's one of the most open floorplans you can find.

I've measured this several times and at 2 other people's houses. If you calibrate each bass source to, say 75dB, individually then you can play them simultaneously and adjust the phase until you measure maximum SPL. Its 81dB (+6dB) every time for me. It works with 2 subs. It works with 1 sub and the main speakers (right at the crossover frequency). It works with subs seperated by 12ft - my current configuration. It works at my house, Tom Simms' house and Bryant Brunner's house. So far I haven't found a case where it doesn't work. You just have to find the right phase adjustment for each case.

 

[Seth_L]

Ryan,

That still doesn't explain away the fact that 110dB + 110dB = 113dB.

Seth

 

[ThomasW]

If you were to take you two subs put them in a large room you would only measure a 3dB gain when they're side by side because they're not acoustically coupled

Seth

Let's clarify the terminology because I think your statement is going to confuse some people.

They may not be acoustically coupled to the room, but they are certainly acoustically coupled to each other (that's where the +3dB comes from). This is especially true of subs given the wavelengths of the frequencies they reproduce. People should note that this same coupling occurs at higher frequencies too, depending on the separation between the drivers. It's the fundamental reason MTM loudspeaker designs have their characteristic dispersion properities. Two drivers placed in appropriate (close) proximity act as one single larger driver.

That is one form of acoustic coupling, now room/cabin gain (acoustic coupling to the room) is a whole other issue......

 

[David Gadd]

SethL:

My understanding is that the "accoustic coupling" is occuring outside the woofer enclosure, not within the enclosure. Accoustic coupling occurs within the room.

You are claiming that a partition within a sub enclosure will drop the combined output of a two woofer sub by 3 dB; How is that possible? You don't hear the sound waves within the enclosure (that's the main point of an enclosure).

Two subs within the same box = two subs in a partitioned enclosure = two subs in separate enclosures next to one another.

My understanding:
You get 3 dB from doubling the cone area (2 woofers have twice the area of 1) which is what your "110dB + 110dB = 113dB" is true for BUT you also get 3 dB from doubling the input power (2 channels = twice the power).

 

[MichaelAngelo]

Ok, start with one Tempest, for example. If you add another Tempest to the enclosure(and double the volume of the box too),without additional amplification, you gain 3db. Then, if you double the power, you get another 3db. Right??

So, one Tempest, one 250 watt amp= Xdb
Two Tempest, one 250 watt amp= Xdb +3db
and Two Tempest, two 250 watt amps =Xdb +6db

is this right??

 

[Anthony_Gomez]

correct...and to further make your point:

one Tempest in n-Liters, one 250 watt amp= Xdb
Two Tempest in 2n-Liters, one 250 watt amp= Xdb +3db
and Two Tempest 2n-Liters, two 250 watt amps =Xdb +6db

 

[MichaelAngelo]

Thanks for the help Anthony.

 

[Demas]

Ok, start with one Tempest, for example. If you add another Tempest to the enclosure(and double the volume of the box too),without additional amplification, you gain 3db. Then, if you double the power, you get another 3db. Right??

This is correct.Some of these terminologies are going to confuse alot of people, especially since conclusive proof has been verified.Acoustically coupling deems 3db gain, double the power nets an additional 3db so the most one can gain is 6db.Side by side in different corners equals up to 3dbs as their is no coupling to contend with.

Now I not sure what happens when two different subwoofers are coupled?Possibly just 3db?

Demas

 

[Pete Mazz]

Seth's math is correct, no disputing that. Two 110 dB sources with seperate power will sum to 113 dB, "by the numbers".

The question is, I guess, how far apart do subs have to be in a room before they decouple? At 80Hz, 2 subs could be 7' apart and still create a unified wave. At 40Hz, 14'. This is, of course, w/o a room's interaction which may cloud things.

Pete

 

[Hank Frankenberg]

And of course, Pete, room interaction is always in effect, so if one or both of those subs are in a null or peak location, there goes the theoretical math out the window. As in retailing, with subs it's location, location, location.