To me those questions are pretty much irrelavent, but they have been answered many times before. But I guess that I'll do it again.
They are all closed box - Q below 1.0. The baffle step - which is a theoretical concept - is automaticaly "corrected" (whatever that means) when I do the crossover since I use data from the drivers in the box. The systems are all flat, measured in a free field, on the listening axis, within 2 dB throughout the important range of 100 - 10 kHz.
John,
ATCs do have lower Q alignment than VAFs (0.5 vs 0.7), but they are also MORE capable in the low end, and certainly are baffle step compensated. ATC bass is not typical pro driver (it does have rubber surround, not ultralow loss paper/cloth of most 'pro' bass units), and both speakers are vented, so that only adds to the mystery. I really don't know what makes them subjectively more dynamic.
In video applications, it Modulation Transfer Function seems an important measurment of how well the dynamics can be reproduced. Application of this seems a bit more complicated in audio.
Not sure if this still applies:
Windows 7 may have limited XP downgrade rights | Beyond Binary - CNET News
Free Windows 7 XP mode:
http://www.microsoft.com/windows/virtual-pc/download.aspx
The virtual machine concept is old and well developed in Intel processors.
Last edited:
I have had nothing but trouble with Win 7 and legasy programs.
I am aware of "XP mode" but it is a rare platform that can impliment this. I checked mine and none can. You need the latest Intel processors - the high end at that - and the top levels of Win 7 (Pro or Ulitimate). Basically unless you have a megabuck system you can't do it. Nice idea, bad implimentation.
In fact the "test" won't even run on my current system.
Last edited:
Did you turn VT on in your BIOS? What processor do you have?
Intel processors have implemented virtual machines since the 386,
and they do it well.
You mention win 7 64 bit, I'd certainly go back to a 32 bit version,
and probably all the way back to XP Pro if your processor is so limited.
Perhaps look into a processor upgrade for your system, it is not exactly
megabuck systems only - processors start around $100 with VT.
Intel processors have implemented virtual machines since the 386,
and they do it well.
You mention win 7 64 bit, I'd certainly go back to a 32 bit version,
and probably all the way back to XP Pro if your processor is so limited.
Perhaps look into a processor upgrade for your system, it is not exactly
megabuck systems only - processors start around $100 with VT.
Last edited:
I certainly can not agree that the woofer alignment is irrelevant.
Anyway, I did a google search for independent Summa reviews. All I could find was a review of the Abbey from Enjoy the Music. They agree the Abbey is very nice sounding and they are dynamic, but they seem to disagree regarding bass response, "Then we have the bass, or lack thereof. Even though a 12-inch woofer is used the Abbey does not play low". When I look at the woofer you use in the Abbey, your enclosure size and your quoted system sensitivity compared to woofer sensitivity spec I see a very low Q system (less than 0.5) and I don't see how you can achieve 95dB {edit: "midrange"} sensitivity (same as the woofer spec) and compensation for the baffle step (which would required that the sensitivity drop by somewhere between 3 and 6 dB).
There is nothing wrong with any of that, particularly since your speakers are intended for use with multiple subs, but it does seem to fit with my previous observation.
Last edited:
Yes John, none of my speakers are intended to be used without subs so talking about their bass response without them is rather pointless isn't it.
The "alignment" of any LF source gets swamped out by the room and also in my case by the subs. Hence it becomes pretty much irrelavent.
No I don't think your observation fits.
The "alignment" of any LF source gets swamped out by the room and also in my case by the subs. Hence it becomes pretty much irrelavent.
No I don't think your observation fits.
Last edited:
Not at all true about Intel processors. Even Intel's site lists those that can do "XP mode" and those that cannot. Not even all of their current processors can do it. I suspect those are mostly laptops. My 2 month old laptop with Intel dual core cannot do it according to MS own test.
One of my computers that I checked is an AMD dual core processor and there is no switch in the bios.
The one I am on now is also dual core AMD and the MS program that checks its capability won't run. There is also no switch in the bios. So I have to assume that its not capable. These are not low end computers by any means.
Lack of bass can be properly EQed if the driver has a good Xmax. Digital music playback is not only increasing in convenience, but also in quality. So there is more convenient means of applying EQ to compensate for any speaker response, this actually presents lots of potential for speakers like these even if no additional bass is added. Further more, the advantage of such type of design may resullt in better resolution in the bass.
As far as visualization goes you can use 3rd party software as well. I have used VMWare on a P4 Dell so I am pretty sure you don't need virtualization in the processor. VMWare costs money though but Virtual Box is free and open source. Worth a try.
And I have been wondering about the Xmax bass stuff. This is what a Linkwitz Transform is right? What are the downsides to extending bass response this way?
This bragging point from Meridian had me wondering about it.
"Bass Extension
There is more to an active loudspeaker than simply improving the efficiency and overall performance of the system. An active approach can deliver benefits that are simply impossible for a passive system to realise. We can’t change the laws of physics, but we can use them to our advantage.
There is a known relationship between the low –3dB cutoff frequency (f), the physical volume of the enclosure (V) and the efficiency (e). It is:
e = V/f3x K
where K is a constant relating to the system’s design. In a nutshell, this means that the cost of a smaller cabinet is either less bass or lower efficiency. The ability to consider an active loudspeaker as a total system – an active crossover with filtering, amplifier, power supply, driver and enclosure – allows the overall response and performance of the system to be modified, essentially altering that constant, K, in the equation above.
For example, the original Meridian “Interactive Bass” system used auxiliary filtering, and the particular alignment provides a sixth-order rolloff plus an additional octave of bass compared to a passive speaker of the same volume and efficiency (see Fig. 4, below).
Putting this more impressively, a passive speaker with equivalent bass response would need to have eight times the volume, or twice the linear dimensions. In addition, this alignment minimises cone movement of the bass driver for a given output – indeed, cone deflection for a ported system such as the DSP7200 or DSP5500 is one third as much as using the same drivers in a passive sealed box with equal broad-band excitation."
And I have been wondering about the Xmax bass stuff. This is what a Linkwitz Transform is right? What are the downsides to extending bass response this way?
This bragging point from Meridian had me wondering about it.
"Bass Extension
There is more to an active loudspeaker than simply improving the efficiency and overall performance of the system. An active approach can deliver benefits that are simply impossible for a passive system to realise. We can’t change the laws of physics, but we can use them to our advantage.
There is a known relationship between the low –3dB cutoff frequency (f), the physical volume of the enclosure (V) and the efficiency (e). It is:
e = V/f3x K
where K is a constant relating to the system’s design. In a nutshell, this means that the cost of a smaller cabinet is either less bass or lower efficiency. The ability to consider an active loudspeaker as a total system – an active crossover with filtering, amplifier, power supply, driver and enclosure – allows the overall response and performance of the system to be modified, essentially altering that constant, K, in the equation above.
For example, the original Meridian “Interactive Bass” system used auxiliary filtering, and the particular alignment provides a sixth-order rolloff plus an additional octave of bass compared to a passive speaker of the same volume and efficiency (see Fig. 4, below).
Putting this more impressively, a passive speaker with equivalent bass response would need to have eight times the volume, or twice the linear dimensions. In addition, this alignment minimises cone movement of the bass driver for a given output – indeed, cone deflection for a ported system such as the DSP7200 or DSP5500 is one third as much as using the same drivers in a passive sealed box with equal broad-band excitation."
An externally hosted image should be here but it was not working when we last tested it.
The virtual mode with 386s was X86 mode to run real mode sessions such as DOS or any other real mode OS. I'm saying they have extensive experience with it. Yes you do need a newer processor to run MS XP mode however as I said they start at $100 so you might consider a processor upgrade rather than buying a copy of XP.
Others have pointed out free software that supports VM if you don't want to spend the bucks. It is going to take some work but it should be possible. Perhaps VT should be on your list of requirements when buying your next laptop.
Look up assisted alignments in Thiele and Small theory - a B6 vented alignment for example if you want more background on this. Remember, the boost requires more power, so while the passband efficiency might be higher it is not higher at Fb. Power is cheap these days so not a major issue - however there is also more VC heating. Assisted alignments usually add a peaked filter that increases the order by 2 - sealed goes from 2nd to 4th and vented from 4th to 6th. This HP filter helps to remove out of band material that wastes excursion and power.
A Linkwitz Transform is a sort of special case that maintains a sealed system as a 2nd order system but does alter the alignment.
As I pointed out in my article at Rod Elliots site, the QB5 I alignments optimise box size and frequency response extension, and the II series optimise power handling.
In my own system I put the main speakers in the quarter quarter position that minimises standing wave excitation in both the smallest room dimensions, and then use a subwoofer at a position that gives the smoothest overall bass frequency response.
If you look at Smalls constant kp, then the rise from around .85 in a sealed box, to around 6 for the typical QB5 I box is a increase of more than six times acoustic output capability and is definitely worthwhile doing.
rcw.
In my own system I put the main speakers in the quarter quarter position that minimises standing wave excitation in both the smallest room dimensions, and then use a subwoofer at a position that gives the smoothest overall bass frequency response.
If you look at Smalls constant kp, then the rise from around .85 in a sealed box, to around 6 for the typical QB5 I box is a increase of more than six times acoustic output capability and is definitely worthwhile doing.
rcw.
I believe that "real mode" (which has been arround since a 386) and what is required for "XP mode" under Win 7 (called VT I believe) are completely different things. And disappointingly, "XP mode" require Win7 Pro or above. Most computers come with Win 7 Home premium and the upgrade is $89. So this and a new processor and I may as well just buy a new computer.
Yes real mode VMs emulate the 8086. I worked in CPU design for a company that cloned the IBM 370 mainframe architecture which also supported VMs. My point is that Intel knows what they are doing as far as virtual machines go and VMs do often work very well.
There is a newer VT mode as I have agreed with you for the last 3 messages or so - Yes, as I said you might want to buy a new computer. And again others have commented that there is 3rd party VM software that works with even a P4. All Pentiums support virtual machines, however it seems that there is an enhanced VT mode that the MS VM software requires.
Xmax is the excursion capability of a driver in which the driver reacts quite linearly. In a low Q aligned system, especially a sealed box, is like increasing stiffness of the spider, and sort of compresses large signals that require more excursion. Using an electronic filter like that seems to change the overall Q of the system. While this might be better than using a ported alignment because the interaction between port and driver is eliminated, I wonder how it would compare audibly against the same speaker using equalization. Using the electronic filter still restricts where the cut of point is; whereas, using equalization, it seems possible to adjust the settings to utilize the driver until you feel the distortion becomes unacceptable.
Air as a spring - like a closed box - is quite linear and in fact a driver in a closed box is more linear than the same driver in free space or ported. This is because the air is more linear than the spider. The amount of "linearization" depemds on the relative stifnesses of the two components - the ccone spider and the air sring.
Agree.
One thing that I have not really explored is how the variation of air pressure on the diaphragm impacts the driver at the higher frequencies because the air inside the enclosure will create different damping effects on the diaphragm modes. If we only use the piston mode range of the driver, then possibly this would not be a problem.
Another thing that would be interesting to explore is the symmetry of the total Kms curve.
I thought it would be interesting to see what the Kms of a driver without a spider would look like.
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
- Status
- Not open for further replies.