ACI Maestro... (2 Viewers)

[Craig Chase]

Mike... Would you like to tell us why it sounds better? Or would you have to kill us? ...

It IS pretty common that the effect of "eq"ing a sealed design causes some phase delays similar to a ported design.... You have not experienced any such problems with the Maestro ?

 

[Mike Dzurko]

Craig:

All else being equal, a lower F3 will sound better because the group delay is lower in frequency and less audible. I don¡¦t want to have to kill anybody but the technology is proprietary, and we don¡¦t own it. It has been around for many years and is a property of the U.S. OEM company that we purchase the amplifiers from. We¡¦ve used it in the Titan for over 12 years and the Force for over four years. The way I understand it, in terms of Q, the driver thinks the cabinet is approx. twice as large as it really is. Measurements confirm this and show the more gradual roll-off of the left and right inputs vs. the Theater input. The following close mic chart is of a Titan sub, (don¡¦t have the Maestro file here but they look very similar with the Maestro showing a bit more below 20):

 

[Craig Chase]

Mike... Thanks for the clarification and the graph. This is shaping up to be a fun test !

 

[Jack Gilvey]

http://www.trueaudio.com/basslst2.htm

http://sound.westhost.com/linkwitz-transform.htm

 

[Edward J M]

I assumed you were using an LT to preserve Qtc at 0.6. I do believe this will introduce additional group delay vs. the theater input, but I agree - the human ear is insensitive to increases in GD in the bandwidth we are discussing.

Craig, it would be interesting to measure GD and impulse response on the Maestro with both the theater input and the speaker inputs and see if the measurements correlate with any of your subjective impressions between the two inputs.

It would also be interesting to compare the impulse response and GD of the Maestro using the speaker inputs to that of a 4th order vented sub with a 20 Hz tune.

Regardless, the LT will chew up excursion and amp power way down deep, so its a good thing you've got that beefy amp and high excursion 15", Mike.

Craig, maybe measuring THD limited output in the lower registers would also be helpful, since the sealed sub relies exclusively on increased cone excursion to maintain SPL as the frequency drops, and this becomes even more of an issue when EQ is used to extend the response.

 

[Craig Chase]

Ed - I will listen for audible delay against the UFW-10's we have here, and if I hear anything, we can go from there.

The distortion idea makes sense... and is a pretty easy measurment.

 

[dave alan]

Curious to know why it would be interesting to measure Group Delay if it's inaudible?

With the EQ boost, the GD will actually improve to about 30 Hz, (which is where it matters subjectively) and then it shouldn't increase more than a couple of ms below that.

I'm sure the amp will clip before excursion becomes the main problem down low.

I also find it hard to believe that a 15" driver in a 2 1/2 cu ft box has a Q of .6 without EQ.

With 12 dB of boost and only 500 watts, the driver has to have efficiency into the 90s.

Answers, Craig...we want answers!

 

[Craig Chase]

The first answer... After having The SVS PB2+, B4+, Hsu VTF-3 Mark II, Velodyne FSR-18, PSB Subsonic 7 twins, Quad Rocket UFW-10's, Sunfire Signature Twins, VMPS Larger Subwoofer Twins, and several other subwoofers in this system...

I want to find out how the Maestro SOUNDS... Then we will get to all that measurement stuff...

 

[steve nn]

I want to find out how the Maestro SOUNDS... Then we will get to all that measurement stuff...
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I'm all for that Craig. We're going to have to impose a two beer/two glasses of wine limit on you during your listening sessions though.:p)

 

[Craig Chase]

Steve... I can handle that. (note to everyone else... there was NO limit on martinis listed) ...

Steve, Honest... I have better hearing after 4 martinis.

I am also a great dancer then, too.

Come to think of it... after SIX martinis, Rosie O'donnel starts to look good, too...

 

[Brian Bunge]

Actually, I'm pretty sure that ACI is not using an LT circuit. I spoke to Mike a few years ago and he told me what it was called, but I can't for the life of me think of it right now. The term he used definitely was not "Linkwitz Transform" though. Whether or not the two work in similar fashion is a question that I imagine only Mike can answer.

BTW, if you have a high excursion driver and plenty of power an LT circuit is a beautiful thing!



Dave, what's so hard to believe about that? Having the right driver with the right parameters makes this highly possible. The first driver that comes to mind is the Adire Audio Tumult, which is a 15" driver. Another is the Blueprint 1503. The real feat would be to achieve a low Q AND a low F3 in a small, sealed enclosure without having to use any boost/EQ.

 

[dave alan]

I agree that it's a beautiful thing!

The Tumult is an exception, even though I would think it's closer to .7 than .6 in 2 1/2 cubes. Check that...the Tumult is THE exception.

Not familiar with the Blueprint except for a vague memory. Has it been around for a long while?

The only company I know of that holds a patent on the L/T type of EQ is Bag End.

I heard that your gonna kick around a Rocket UFW-10 in the near future...I hope you'll post thoughts. I'm very impressed with that little 10" sub, myself.

Craig uses 4 of them as subwoofer headphones.

 

[Craig Chase]

Dave ... It has been mentioned that I have a big head... but four subwoofer headphones ? ...

One thing that made the UFW-10's so compelling was value. I got the first pair for $895 as a returning customer, and the second for $795... All four subwoofers for $1690.

Picture a 53x13x13.5 inch subwoofer, 2000 watts of amp, phase control and eq for EACH driver, 208 pounds, and 4x10 inch drivers for $1690.

And yes, hearing the Maestro with an SVS B4+ on one end and the UFW-10's on the other end... lots to talk about

As an aside, did you see Frank is looking at 750's now? He might want to put a pre-order in for B-Stock when the 1000's start coming in...

BRIAN ... Good to see you here. Pardon my manners eariler... yes, it will be fun testing a sealed sub again...

Perhaps when Mike D. gets back next week, he can tell us a little more about the driver in the Maestro...

 

[Edward J M]

Hi Dave:

I thought it would be interesting from an academic standpoint to compare the GD curves and the impulse response for the two inputs just to see how the EQ circuit affects them both. It's cool to learn how the system actually reacts to these changes, rather than just trusting theory or modeling software.

It would also be interesting to see if the GD and IR for the speaker inputs resemble those of a 4th order alignment with a similar FR curve and F3 - a no free lunches type of comparison.

I didn't say GD was in audible; it is audible in certain bandwidths (as you stated above). Below 30 Hz, we are relatively insensitive to it, and I was hoping both Craig's measurements and his subjective impressions would support this.

 

[Craig Chase]

Ed - I am up for anything, after the listening tests are done, we can get Mike D. involved in the measurements.... and go from there.

What I am MORE looking for from the Maestro is how it will work with something like the Onix Ref 3's in two channel running the McIntosh Amp and modded Denon 2900 Universal player. The prices for Amp, Speakers, and Player total over $11,000. Other than the 15 to 30 Hz range, this system will go toe to toe with anything I have heard for under $40,000... and that is no small praise.

Adding the Maestro takes the list price to $13,000 ... for a true high end system, that is a solid value, especially if the Maestro gets that last Octave.

Mike D. also makes some nice high end speakers, and I would guess a lot of owners of their stuff would like to know whether a good subwoofer enhances the listening.

I doubt the single, sealed, 15 inch driver will "outgun" an SVS PB2+ for output, but I will still be looking for its performance in a high end home theater set up as well.

So... I will really be listening for "exceptional" bass quality.

By the way, Mike ordered the wood last week, so fiugre it will be around October before I receive the unit.

 

[Brian Bunge]

You forgot to add stuffing! In just under 2ft^3 my Tumult's Qtc is around .63, IIRC. With the LT I have a Qtc=.6 and have in room response flat to 10Hz.

Kyle at Acoustic Visions is selling the Blueprint drivers again.

 

[Craig Chase]

Speaking of the Tumult.. When we had the Denali here, The passive radiators seemed to keep the system's overall performance down. For real world performance, I would like to see Kyle add a second Tumult to the unit, lose the PR's, and raise the price the $200-$300 needed....

 

[steve nn]

I would like to see Kyle add a second Tumult to the unit, lose the PR's, and raise the price the $200-$300 needed....
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Never thought of that. Terminal to terminal shipping would still come in very favorable also.

 

[Craig Chase]

Steve... Exactly, It would STILL be heavy enough to use as a boat anchor... And I think it would have a much higher SQ... Someone had also mentioned the Keiga Plate amp was also a limiting factor...

 

[Edward J M]

Unless Kyle uses an LT (or equivalent) a dual driver sealed Denali (of that enclosure volume) wouldn't have the extension that the PR'd version currently offers. Of course adding the LT woulnd't be that big of a deal, and Brian clearly had success with his sealed Tumult LT design.


Indeed....in that price range you should expect nothing less.