Anybody make (SEALED) Monitor Statements & CC ??

[randyc1]

Has anybody built the "Monitor Statements & Center Channel (SEALED)

Would like to build them Sealed to go along with my Subs for my HT ??

Searched many threads but cannot find ?

Thanks !

[BeerParty]

The only sealed version of the Statement series I have seen is the full sized Statements.

Why do you want to build sealed versions of the Statement Monitors or Center? The ported versions will work with a Sub just fine. Sealed versions would have to be the same size and require the same positioning due to the driver spacing and transmission line Mid-woofer, so you wouldn't gain anything going sealed.

[randyc1]

The only sealed version of the Statement series I have seen is the full sized Statements.

Why do you want to build sealed versions of the Statement Monitors or Center? The ported versions will work with a Sub just fine. Sealed versions would have to be the same size and require the same positioning due to the driver spacing and transmission line Mid-woofer, so you wouldn't gain anything going sealed.

essentially we're eliminating the content produced by the system port.....it's not needed as the subwoofers are handling that range......and far more effectively that any port ever could. Ports exist for one reason and one reason only........to extend response in the most efficient way possible. Now it's important to remember that port output is 180 degree phase reversal from the system woofer.....and probobly 180 out from the subs too. Hence the problem with sub integration and ported designs.

[AdelaaR]

I understand ... but if you were to cross with a sub ... wouldn't that mean that the ports wouldn't do anything anyway because they wouldn't get any frequencies that would use them?
In that case ... does it matter?
Even more: isn't a free floating driver more responsive compared to a boxed one?

[dar47]

essentially we're eliminating the content produced by the system port.....it's not needed as the subwoofers are handling that range......and far more effectively that any port ever could. Ports exist for one reason and one reason only........to extend response in the most efficient way possible. Now it's important to remember that port output is 180 degree phase reversal from the system woofer.....and probobly 180 out from the subs too. Hence the problem with sub integration and ported designs.

This design was optimized for open back mids and port to dig low. If your doing music as well you may like just the towers ported with no sub as long as your room isn't to big. I've heard them crossed to a sub and they do well. Maybe a better option is to consider one of the other designs optimized for sealed, why reinvent the wheel and the sound is vary close? I did the RS 3-ways and they are close on budget, maybe the Khans they both have matching centers and surrounds as well.

[technodanvan]

I guess I would prefer some speakers that could dig low enough that using a lower crossover to the subwoofer becomes feasible. I would think this would be a lot more important than any phase issues of the bass, especially seeing as how many subwoofer amplifiers have options to adjust that anyway.

That said, I would think if you're really serious about making them sealed - while maintaining the open back and all other dimensions - you could just play with an RS180 in WinISD to find out how much of a volume reduction is necessary, then fill that volume with additional MDF or other solid material. It wouldn't be my choice, but it would work.

[randyc1]

This design was optimized for open back mids and port to dig low. If your doing music as well you may like just the towers ported with no sub as long as your room isn't to big. I've heard them crossed to a sub and they do well. Maybe a better option is to consider one of the other designs optimized for sealed, why reinvent the wheel and the sound is vary close? I did the RS 3-ways and they are close on budget, maybe the Khans they both have matching centers and surrounds as well.

I am keeping the open back mids!

[randyc1]

I understand ... but if you were to cross with a sub ... wouldn't that mean that the ports wouldn't do anything anyway because they wouldn't get any frequencies that would use them?
In that case ... does it matter?
Even more: isn't a free floating driver more responsive compared to a boxed one?

The compliance or box air spring will make it much easier for a woofer to stop an start when asked to do so. In a leaky aperiodic box or ported enclosure, the woofer has a much more difficult time stopping, and relies on high motor strength to do so....as in subwoofer drivers......in 7" midwoofers.....not so much. So what does this mean ..., the sealed variant will have more accurate, phase coherent bass.

[technodanvan]

The compliance or box air spring will make it much easier for a woofer to stop an start when asked to do so. In a leaky aperiodic box or ported enclosure, the woofer has a much more difficult time stopping, and relies on high motor strength to do so....as in subwoofer drivers......in 7" midwoofers.....not so much. So what does this mean ..., the sealed variant will have more accurate, phase coherent bass.

I really think that isn't an issue at all when using a quality driver and appropriate amplification. The RS180 should have more than enough motor strength to start and stop such a small driver. You see incredibly large motor structures on subwoofers because the cone might be traveling a full inch while moving far more mass - in order to start/stop them you'll need a magnet exponentially larger that that of a small woofer.

I understand your concerns with phase (though I doubt I'd ever hear it myself), but accuracy of a good driver in a sealed vs. ported alignment should not be an issue in a good design.

[Face]

If you're keeping the open back mids, it may not be a problem. I would contact the designers about what the appropriate woofer volume should be.

[JonMarsh]

I understand your concerns with phase (though I doubt I'd ever hear it myself), but accuracy of a good driver in a sealed vs. ported alignment should not be an issue in a good design.

Oh, but it most definitely is! There are significant tradeoffs for that bass extension in a ported system- it is called a Helm-Holz resonator, you know.

I'll post this evening when I have some time and highlight in the context of the Isiris design and Mike's similar Isis clone.

The drivers are important for the T/S parameters needed to work "correctly" in a given alignment, but the enclosure adds a lot to the output when ported. It's like blowing across the mouth of a coke bottle.

Regards, Jon

[JonMarsh]

OK- sealed box versus ported.

Let's be sure to get some fundamentals clear. A woofer in a sealed box is a high pass system of 2nd order, and can be described in a straight forward way regarding both it's frequency response and transient response with classic mathematics used for 2nd order electrical systems- because mass and compliance have their direct analogs in inductance and capacitance. T/S parameters describe the combination of mechanical and electrical parameters working in concert which describe the total 2nd order HP characteristic.

Q is the "quality factor" which is a way of stating the normalized response at Fs compared with the passband response. For a Q of 0.5, the response at Fs will be 1/2 of the pass band (applied signal). This correlates with what we call -6dB down in level. A Q of 0.5 is also known as "Critically damped", as it will have essentially zero overshoot for the application of a step function. For a Q of 0.707, the level at Fs is 0.707x the passband level, or -3dB. It's not critically damped at this point, and their will be some overshoot. Higher 2nd order Q's are possible, and this is what leads to things like a Q of 1 or 1.2 or whatever- this is what happens when you put a driver with a small motor (low electrical damping) with high Qms in a small box.

Now, ported systems are more complicated. Sealed are 2nd order high pass, a basic ported system is a 4th order high pass. The driver is part of the equation; the tuning of the enclosure, with air mass in the port and enclosure compliance is the rest. Basically, we have a Helm-holz resonator which is driven by a driver. Resonator. Hmmm. That sounds like energy storage and amplification in some range of frequencies, and that's pretty much what is going on.

You can make a concerted effort to design a ported system for relatively low Q as ported systems go, and this does help- but how much?

Let's look at case 1 for the Isis clone Mike has built but not yet finished. His cabinets have a woofer working volume of 127 liter; he wanted extension to 20 hz, and the defined system tuning is setup for box Fs of 18 Hz.

With the Aurasound NS12 drivers, this is somewhat damped ported alignment, with the response down about 6 dB at 20 Hz.



A maximally flat alignment (often used by designers) would require moving the box Fb up to around 30 Hz; below box Fb, the driver unloads, and the system response rolls off at 24 dB/octave. Though the driver is trying to put out sound down there, the port output is out of phase and canceling with the woofer output.

What does the step response look like?



There is some significant overshoot, and about a full cycle of damped ringing following the step; the ring frequency predicted buy Unibox is ~ 36 Hz.

This is what we call "overhang", and it is not so much the response of the driver as that of the box. With an underdamped driver, the Q is higher, and the level and duration of ringing are higher.

What about the sealed version? I chose a sealed design for reasons I'll explain a little later, but specifically I was targeting a smaller enclosure and a controlled roll off that would work well with typical boundary reinforcement effects with correct room placement. I didn't want a system Q much over 0.5; 0.55 or so being OK.

Here is how the alignment looks plotted (this is anechoic response, like the previous graph).




For this alignment, predicted response is -6 dB at 34 Hz.

Calculated Step Response:



This, to me, is a lot nicer looking, and more articulate sounding. This is what "fast" bass is, with essentially zero ringing on the step response.


But what about the in room response? Years ago a friend and I prepared a MathCAD sheet for calculating the boundary influence based on three adjacent boundaries, nominally floor, rear wall, and side wall. For a tower speaker, floor distance is a fixed parameter created in the design. We were half too clever with recursive functions, and this wouldn't work on later versions of MathCAD.








Plotted pretty in Excel:



The optimum setup is for a golden mean spacing on the boundary dimensions. The absolute magnitude of these dimensions must be tied in with the Fb and Q so that the room curve and the box/driver curve are complementary to produce an extended system response.


Taking another example, if you do this properly for the boundary distances, you can pretty smooth response:



If you use poorly staggered dimensions, the results can be quite audible, not in a good way:




Using a big speaker in a small room with close adjacent boundaries is just asking for trouble... and trouble is what you get!




(and that's in additional to strong short delay wall reflections which will create strong combfiltering in the frequency response).

So, re sealed, I say, go ahead and try it. But you might want to model in Unibox or a similar program, and see how you want to adjust the enlcosure volume for a more optimum sealed system. Also, drivers with a Qts of 0.32 or less don't really lend themselves to sealed alignments, unless you're looking for a small box and high Fb. Then too, factory data on Qts isn't always the last word in accuracy; for instance, I find most SS drivers to not be as low as claimed; it seems their magnet systems aren't charged as strongly in production as some of their prototypes.

[technodanvan]

That is a heck of a response Jon, I must have caught you on your day off!

I have a multitude of questions regarding the 'read speed' of the human ear based on frequency, the audibility of such a phenomenon in that lower octave, the effects ringing may (or may not) have on other frequencies when played by the same driver, and extent of ringing based on excursion of the driver. I will do some homework tonight and see what I can find.

If the OP is interested I can post here, otherwise I may have to set up a separate thread.

[randyc1]

That is a heck of a response Jon, I must have caught you on your day off!

I have a multitude of questions regarding the 'read speed' of the human ear based on frequency, the audibility of such a phenomenon in that lower octave, the effects ringing may (or may not) have on other frequencies when played by the same driver, and extent of ringing based on excursion of the driver. I will do some homework tonight and see what I can find.

If the OP is interested I can post here, otherwise I may have to set up a separate thread.

No problem post here if u like !

[impala454]

Is there a size constraint? The sealed full sized Statements are larger, but not too terribly much larger. Though I suppose it could be a cost consideration as well.

Statements Monitors: 22" x 10.5" x 12"
Sealed Statements: 40" x 11.5" x 16.5"

[randyc1]

Is there a size constraint? The sealed full sized Statements are larger, but not too terribly much larger. Though I suppose it could be a cost consideration as well.

Statements Monitors: 22" x 10.5" x 12"
Sealed Statements: 40" x 11.5" x 16.5"

Monitors Statements will do fine since my subs will be handling everything below 80hz