ACI Maestro... (2 Viewers)

[Mark Seaton]

Hi Craig,

When you say "kept the performance down" is that because you didn't see the Tumult itself work all that hard down low? I was the one who pointed out the amp to be the weak point with the Denali's LF performance. I would expect it to fair much better as a passive unit with a good outboard amp, or with a more stout LF amplifier which won't be limited by the internal high pass.

 

[BobAlbano]

Have I mentioned that I love to see Dave, Craig, Edward, Mike, and Mark all talking subs....very good information here from some extremely knowledgeable people! Keep it up!

 

[Craig Chase]

Mark ... The performance problem was The PR's bottoming too quickly... and in retrospect, I wonder if the AMP was introducing some infrasonic material...

And I know you were testing a bit there, of course the Tumult should show little movement in the frequency range the PR's were tuned to .

My Denali's PR's would flap uncontrollably at 95 Db levels at 16 Hz.

 

[dave alan]

Brian,

Ahhh, stuffing. If you've got what, 3 or so pounds of polyfill?

OK, .63 I buy. Thanks for pointing that out.

Craig...How it SOUNDS is what matters...and since no one else will devise a 'Sonic Signature' list of measurements that correlate to descriptive terms that translate to 'How it sounds'...I nominate...YOU!

Edward...Twin Tumults, sealed, L/T, enough power...Hmmm...

 

[Brian Bunge]

Dave,

Yep, stuffing! According to Unibox, you get .6 with heavy stuffing and around 2.25ft^3 internal volume. If you jump up to right around 2.5ft^3 or so with heavy stuffing you're down to .58 or so.

And since the subject of Twin Tumults came up, I have a customer in Philly with a full Aerial Acoustics setup...except for the subs. I built him two Tumults and an LT circuit to the exact same specs as my single Tumult enclosure and LT. He's powering it with a big QSC amp (around 1400W per channel, IIRC). It's my understanding that he feels it sounds better to him than a dual Aerial SW12 setup he's heard or any single Velo HGS18 setup that he's heard. I figure that's pretty high praise for the Tumult.

 

[Richard_M]

Now your talking Dave...

 

[Brian Bunge]

Thanks Richard. I really appreciate that. Funny thing is, this customer opted for a satin black laminate finish since the subs were mounted in the bottom section of a large cabinet. I did make sure that there was no bottom to the cabinet so that there would be no physical connection between the subs and the cabinet to create any resonance issues. Still, moving a couple of 18" cubes weighing ~130 lbs. in there must not have been fun. IIRC, there are removeable trim pieces to make installation/extraction easier, but damn...130 lbs. spiked cabinets are not easy to move around period.

Craig,

Yeah the dual 18" PR's appear to exceed Xmax right at 16Hz with 1000W of power into the Tumult in that particular enclosure.

 

[Craig Chase]

Have you ever just enjoyed soaking everything in ? This is one of those times. A bunch of guys who LOVE this stuff (Mark Seaton, Edward JM, Mike D, Brian B, Dave Alan... ) all chiming in with some great thoughts.

All guys who want the best that is available... no magazine agendas... just good sound. What could POSSIBLY be better ?

Guys who KNOW what you mean when you talk about the decay on a kick drum.

This is the type of stuff that women look at us and wonder when we will EVER grow up.

Hopefully, we never will...

 

[Jack Gilvey]

The ELF (Extended Low Frequency, patented by Bag-End) process is a technique in which a driver is put in a box small enough to push the Fc above the intended low-pass crossover of the system. The rolloff below this point is a predictable and smooth 12dB/Oct, so a simple shelving filter is all that's needed to have any desired response extension. Adequate output at these very low frequencies is a more formidable challenge, however...witness the 8Hz whisper that a mic can almost pick up from the ELF-18...

 

[Craig Chase]

Oops...:b ... You always miss some good guys... Add Jack Gilvey and Richard M. to the list of really "into this and willing to share" gentlemen.

Jack - Yep, The Bag End stuff is an interesting design. I have had several chats with audiophile "purists" who abhor tone controls (actually... ANY EQING) yet think the Bag End 18 incher is the most accurate subwoofer available.

Gotta love that ...

 

[Mark Seaton]

Ahh... It's obviously tuned a good bit higher.

Since we are talking about deep bass and EQ/processing, I want to pass on a little realization I made when dialing in a ContraBass Friday. Where most DSP's only allow filter settings down to 20Hz, they usually have flat response to 10Hz, and the filters do affect the response below 20Hz. By using shelf, parametric and different types of high pass filters, you can get pretty creative and get some interesting curves down to near 10Hz, particularly when you can easily measure the response. With more soundtracks like Black Hawk Down and Master and Commander, an 8Hz filter in the K2 is not always enough for reference level playback. The realization here was in looking at the response of different order Bessel filters, where the "specified" frequency is only the start of the roll off. In this case I was able to use an 18dB/oct. Bessel filter set to 20Hz with a parametric or two around there to take the acoustic response down to 14-15Hz while quickly attenuating 10Hz by at least 6-10dB (plenty to protect against over excursion).

So if you are working with a sub that has a tuning and output at or below 20Hz, but only can set your filters down to 20Hz, keep a Bessel filter in mind. Even a 6-12dB per octave set properly can be enough to keep from bottoming things out.

Cheers,

 

[dave alan]

Mark,

What do you think 'reference level' is at 5-10 Hz?

What sort of room gain might apply at these frequencies?

What does a ref level 8 Hz tone do as regards IMD/cone distortion, etc., when the sub is also playing everything else that's recorded up to and on the other side of the crossover point at the same time?

With the advent of Blue-Ray types of Hi-Rez audio and ever-increasing subsonic sources, might there be a need for a sub-subwoofer in the near future?

Just curious as to your thoughts on this subject.

Craig...Back to the Maestro, I keep forgetting to mention that I'm also looking forward to your first hand description of it's fit and finish and relatively small size.

It sure looks great in the pix.

 

[Craig Chase]

Dave ... Even more important: What my wife thinks of the look... She flipped over the Ref 3's ... and hated the Klipschorns, even in Black Walnut. She is really fussy about all that decor stuff. I am happy with a beanbag chair...

I will definitely report on the WAF rating...

 

[Richard_M]

Thanks Mark for that information.

I have been using shelving filters in the past, which of course don't give any protection, but do limit the amount of signal and slope below 20Hz; I guess this only works based on the levels that are seen at 20Hz. Will give those Bessel filters a try.

Makes one wonder why they encode these freq’s on the disc, as most active subs will never re-produce them.

I hooked up my K1 just so I could watch the Black Hawk Down dance routine, after I had seen it I was happy, and back using my plate amp with the 14Hz filter.

Some other amps like Behringer have a 5Hz filter, and to the uneducated could have detrimental effects on the health of the sub, building, and of course us humans.

 

[Mike Dzurko]

This is awesome. Educated, civil, fun! Time for me to shower-shave and get to my first day back at school. The first few weeks will be really hectic so I may be pretty scarce around these parts. Keep having fun!

 

[Mark Seaton]

Our designer, Tom Danley, has long worked on and consulted on non-music applications requiring significant low frequency acoustic power. He keeps coming up with more compact options. While these are still huge, scaled down designs look to be coming closer to workable in custom installations or for crazed enthusiasts.

I am not certain yet if home theaters need better, deeper subs, or are we better off with an "under sub" or such which augments our current subwoofers. There could be a strong argument for the 2 way subwoofer solution in real world installations. Think below 30-35Hz. What gets very interesting is that it is VERY easy to make extremely high performance, compact designs with response to 30-35Hz.

I have played with managable systems which deliver 5-10Hz performance *in-room*, and I can guarantee we will offer something which will get there in the next year or so; more so because we can.

One scene I want to experiment more with is the Black Hawk Down Irene scene, where I am curious to experience the ~7-9Hz pulse which is recorded after experiencing just how much the 18Hz pulsing adds tension and draws you into the scene. If you have a system capable, listen to it and then lop it off with a filter and listen again! They mastered it with a truckload of Bag End subs to actually reproduce it.

Finally, I also predict/recommend that future pre-processors will include subsonic protection in some way, just like we have peak limiting. This will let directors and engineers experiment away without torturing the large majority of subwoofers currently on the market.

My 2c.

 

[Craig Chase]

Mark... Fascinating stuff... I hope to see that 5 Hz subwoofer someday. I am sure it will be a small cube...

Mike D ... Worry not, I won't be using BlackHawk Down at 115 dB with the Maestro...

 

[Brian Bunge]

Hell, why not!? Mike would be the first to tell you how proud he is of the fact that ACI has had little to no driver failure in their subs and I believe most of their speakers as well. I say fire away! Of course, it's not my subwoofer, so that's very easy for me to say!

 

[Craig Chase]

I can see the warranty claim now ... "Mike, Brian said it was OK..." ...

 

[Mike Dzurko]

Craig:

Actually, you can change that to Mike, YOU said it was OK Brian is right. They're pretty tough. The limiter does a great job and the drivers are really strong. I say play it as loud as you want. It's probably louder than I'd want, (I need these ears for many years yet)