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SVS PB12Plus/2 or Adire Tempest/Tumult DIY? (1 Viewer)

Dustin B

Senior HTF Member
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Mar 10, 2001
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Very similar. It's about 1L behind in Vd, larger Vas, higher sensitivity, lower Fs and $200 cheaper. In other words it's a Tumult that was designed to work in slightly larger enclosures with less power for less money. It's a little better than 80% of a Tumult for 60% of the cost.

This guy replaced dual Tumults with quad Avalanche 15 subs.

http://www.hometheaterforum.com/htfo...hreadid=225994

Oh, and Ascendant Audio also has an 18" version of the Avalanche. 6.2L Vd for $100 less than a Tumult but needs some seriously large enclosures if you want to use two :D



Given your space considerations Jack and knowing you're as sick as I'd like to be I think the question isn't whether you should, the question is whether you can afford to. I can't, if you can, well you owe it to the DIY forum ;)
 

dave alan

Second Unit
Joined
Aug 30, 2002
Messages
256
Actually, if I had already had 2 Tumults, I would have just gotten 2 more, in which case, all else being equal, you'd have a lower 'Q' and a couple of dB higher output for a couple hundred less bucks.

Yes, the numbers for comparison's sake are correct, but the Tumult won't be so easily unseated from it's throne, IMO.

Aside from what the numbers say...on paper...the Tumult is constructed like no other driver I've had experience with. If you're gonna apply the sorts of power that a sealed, EQ'd sub of this caliber requires, thermal handling, spectral contamination and long term structural integrity matter.

Only time will tell if the Avalanche is 80% of a Tumult.
 

Eric Ha

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Sep 27, 2004
Messages
146
I suppose if there was one thing I would like more of, it's more dynamics from my sub. I'll notice that it's shaking the house during a movie, but don't feel it in my chest like a good mid-bass passage on music can do with my 8" driven mains. Here's a couple questions:

Is that more a matter of hz level, or is it as I have heard, a matter of group delay?

If so, can group delay be reduced

Is is possible to feel more bass impact without shaking the house more? Would a sealed and eq'ed Tumult or Avalanche sub do this?
 

EdwinK

Agent
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Oct 29, 2004
Messages
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I have a similar question: Living in a very solid concrete building seems a huge disadvantage in experiencing "chest (?) impact". So much so that I am considering buying a buttkicker to "shake the couch/ (elevated) floor" by some other means.

The question being: Is my view correct, or are all those people exaggerating the impact they are experiencing?

ps: my current configuration has flat bass from 20Hz up, but sharply drops off below that.
 

Eric Ha

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Sep 27, 2004
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Well, I am on a concrete slab and I feel tons of shaking through the couch, and feeling the walls during heavy passages makes me worry about the house structure! I just want to feel the vibes "through the air".
 

Edward J M

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If you run an FR sweep at the listening position, you might find you have a moderate null in the 40-50 Hz region.

Even if you have a flat response in the mid bass, this can often be perceived as lacking in oomph when compared to a set of 8" mains which probably have an exaggerated response around 40-50 Hz.

Again, running the FR sweep is the best way to learn quite a bit about your room modes and mid bass response differences between the mains and the subwoofer.

If you find that the mid-bass is flat or slightly depressed, you could experiment with a PEQ and boost this portion of the curve slightly if that type of sound is more to your liking.

If the couch and walls are shaking hard, you are definitely hitting some high SPL. Have you measured the SPL peaks with the RS meter on c-weighted fast?

I prefer concrete floors because they don't transmit nearly as much vibration as wood, but they can reduce the sensation of "felt impact" to some extent. As for feeling the air move, you could try the sub in a location closer to the key listening positions.

BTW, group delay has nothing to do with what you are hearing or would like to see improved.
 

Eric Hargrove

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Nov 24, 2001
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153
EdwinK,

You are 100% correct. A concrete slab does kill the tactile effect. My basement is on a concrete slab and I have very high output with two CS Ultras but the tactile feel is much less than my dads' single PB10 on his wooden floor. A Buttkicker would give you the tactile feel you are looking for. I have four Aura Pro bass shakers in my couches and it makes a noticeable difference. The key is to not overdue the gain on the tactile transducers so that they blend well. Being in a basement is not all bad. You may very well get flatter response out of your system.
 

Mark Seaton

Supporting Actor
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Oct 10, 1999
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Mark Seaton


Quite simply, you are chasing the wrong qualities and capabilities to solve the problem you have identified.

Ed's response above was on the right track. What I would add to his response is that the chest cavity resonance is typically near 75Hz and again around 150Hz. What this means is that the 60-200Hz range is critical to this subjective quality. In terms of loudspeaker and subwoofer performance, this means your main speakers should have good dynamic linearity/capability below 200Hz down to ~80Hz. From the subwoofer's perspective, we would prefer to keep the top end of the subwoofer's range to be reasonably linear. The primary source of problems in this range in fact comes from overdriving the system at lower frequencies. When low frequency content drives a system past linear limits, everything being produced gets distorted, not just the lowest frequencies. This is a form of intermodulation distortion. For larger spaces and higher playback levels, there can be good justification to trade off some sub 20-25Hz energy in reducing the occasions a subwoofer will be significantly overdriven.

With reasonably capable speakers you are far from guaranteed to achieve the desired results, as the room and the interaction of the subwoofer and main speakers adds a huge variable to the mix. This is why we need to pay so much attention to the placement of our main speakers as well as our subwoofers. Examining the response of our subwoofer and mains at the listening position, we can look to insure there isn't a deep recession in this region of interest. For the main speakers, you are first and foremost concerned with the >100Hz range, and you want your subwoofer to not have a serious depression (greater than maybe 6-8dB in the 60-90Hz range. If you have the flexibility in your bass management settings, you can adjust the crossover frequency to work with the strengths of either's placement.

While applying EQ to the subwoofer may be relatively straightforward, the less obvious and more tedious task tends to lie in the interaction of the subwoofer and the mains. I prefer to use EQ, level, and distance/delay settings as my variables. While the phase/polarity adjustements on some subwoofers help with fine tuning, I prefer to first use the delay setting. If you don't have a means of looking at sort impulse for phase response, I will invert the polarity on the subwoofer or the mains and adjust for the greatest knotch at the crossover frequency and then put the system back to normal polarity before making final level and EQ adjustments. With some speaker/room interactions, you should also not be afraid to set the crossover artificially high to achieve the resposne you need. In other words, if your main speakers are giving you too much energy below 80Hz, try a 100Hz or even 120Hz crossover and then engage the crossover in the subwoofer to best mate it with the resulting response of the main speakers. The integration of the center and L/R speakers are the most important to our subjective experience, and should be prioritized in these cases over minor concessions which might be made in the surrounds.

So far as the DIY route, the sealed, dual Avalanche-15 makes for a monster subwoofer at modest cost, but would require EQ to achieve comparable extension. In a well enclosed room, the sealed solution with a pair of high excursion 15" drivers offers the potential of much more output below 20Hz than the PB12+2 mentioned above.

As others have said, the biggest benefit to DIY is the ability to maximize performance within your size/space limits. The closer some of the better subwoofers are to your maximum size/space limits, the less benefit you will find. Intelligent use of EQ allows much more room for "slop" in a DIY design. There are most certainly reasons for going with a production design. There are many choices to be made, and specialized EQ, limiting, high pass filtering, and overall design trade-offs have much more flexibility in a production design, where flexibility with these factors only come at somewhat higher cost levels in the DIY world.

I would say that DIY offers the best chance to exceed expectations when you are striving to achieve more or different performance than is easily available in production offerings. Do remember that SVS very much evolved from DIY efforts which there was a demand for.

Best Regards,
 

Dennis Pagoulatos

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Here's a dumb question:

How do you calculate how much volume you need for a given # of drivers in an IB?

I have thought of going IB in the house I'll be moving into in the next 2 months, since the family room has a flat ceiling and decent low attic space above the entire thing...

-Dennis
 

Mark Seaton

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Oct 10, 1999
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Actually, in many often cited texts, "IB" is used as a descriptor for any ~sealed enclosure which does not fit the description of acoustic suspension. When originally described and used by those at Acoustic Research, it was defined as the air-spring in the box dominating the restoring force. As a general rule of thumb we see this condition with a driver in a box less than 1/3rd the Vas. From this perspective, anything larger can be considered an IB.

The only real concern with respect to total volume is the resulting response of the drivers in that contained volume, and the rigidity of the containing walls which adjoin the listening space. This is related to the total volume dispacement capability, not the Vas. In other words, a pair of 15s moving 1" p-p in 3 cu.ft. will produce much more force over the small surface area of the box walls vs. the same drivers moving the same distance (thus producing the same SPL) in a very large space where the pressure change is much less and distributed over a much larger surface area.
 

Jack Gilvey

Senior HTF Member
Joined
Mar 13, 1999
Messages
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I have my pair of Atlas 15's mounted in a closet of ~3600L, or ~5(Vas). The pressure they put on the closet door at full tilt (with only 150 watts!) is amazing. I was surprised at this, since it's such a large "box" (although small for an IB).
 

Eric Ha

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Joined
Sep 27, 2004
Messages
146


That's all great info also Mark, thanks. I'll start working with my receiver and sub crossover settings. Here's my FR chart of my SVS. I suppose I should flatten this curve?:

FREQ SPL (compensated
16 88.5
18 90.0
20 92.5
22 90.5
25 88.5
28 85.5
31.5 89.0
36 84.5
40 82.5
45 83.5
50 84.5
56 86.5
63 86.5
71 86.0
808384.5

Also, am I right in guessing that while I love the range my newly built Adire ported 281's have, I will probably need to cross them fairly high? They have such a nice low end.
 

John-Tompkins

Second Unit
Joined
Jan 21, 2003
Messages
326


Even though I have two svs 20-39+'s in a smallish room with wooden floors that shake...I decided to try a buttkicker attached to my couch ..Man, this thing worked out better then I though it would..added that extra rumble I was looking for and doesnt unwantingly call attention to itself ( blends well with my svs's ) to create the effect I was looking for... I did buy a 50hz inline fmod crossover from parts express to limit the buttkicker, as I didnt want it going off at inapropriate times.
One thing I didnt want is just vibration.. extra buzzing would have drove me crazy ..Thats the great thing about the buttkicker..its powerfull enough to actually rumble (not vibrate) just like a powerfull subwoofer when playing down low ..Anyway, A big thumbs up from me, Plus it saved me from buying two more svs's to go with the two I already have :)
 

EdwinK

Agent
Joined
Oct 29, 2004
Messages
38
Thanks John, for this extra bit of information on the buttkicker. I hadn't heard all that much feedback on this gadget. :)
 

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