This may be a completely unimportant issue, but what about group delay. I know that group delay at low frequencies is generally a really small to non-existant issue because of the wavelengths, but it's my understanding that group delay audibility thresholds vary with frequency. How much group delay is audible at 100hz, 80 hz, 150hz, etc. Highpass filters add group delay, and the steep the filter the more delay. If you added a 4th order L-R at 100hz the group delay at 100hz would go from around 1ms with no filter (clearly inaudible) to 6-7ms. It seems that some research on group delay indicated that between 1 and 2 cycles is just audible. At 100hz, 6ms isn't a full cycle, but it's getting close. Does this become an issue? EQ add's group delay, if you eq the mains above 100hz, could the amount it adds be enough to be audible?
gedlee said:
Because the series path to earth is never broken, even if the RCA's are unconnected. It's only lifted by 10 Ohms (if the resistor is used) if the diodes do not conduct, and at most by a diode drop (0.6V for a pair, 1.2V if a bridge is used). In other words, the chassis limited to a maximum potential of 1.2V, relative to earth.
Sheldon
Patrick Bateman said:
The transformer method is fine. But, limited bandwidth can be seen at either end - HF or LF. At LF, in particular, source impedance can be very important - be sure your transformers are spec'd for LF extension you want, at the impedance from your source (lower source impedance is fine, higher will increase the roll off frequency).
Sheldon
Sheldon
Yes, but an adapter is nothing more that a plug without the ground lug. That was my point.
Markus
In thinking about it, there is nothing to prevent the customer from using "small" for all the channels as you suggest. They would just need to provide the "mains" measurements with this filter in place and the fitting algorithm would work just fine at fitting to that situation. It's not what I would do, but my technique works either way.
Yes, but an adapter is nothing more that a plug without the ground lug. That was my point.
Markus
In thinking about it, there is nothing to prevent the customer from using "small" for all the channels as you suggest. They would just need to provide the "mains" measurements with this filter in place and the fitting algorithm would work just fine at fitting to that situation. It's not what I would do, but my technique works either way.
gedlee said:
I'm moved to tears. Looks like the idea of selling more than 3 subs got you hooked 🙂
By the way I like the idea of making the mains part of the calibration. The box without a name might not be able to do so.
Best, Markus
gedlee said:
I understand. You can cut off the ground lug, or use a 3prong to 2prong adaptor (for US, anyway). If you do that, the chassis is usually still earthed through the signal connectors. If the signal connectors are too small to carry a fault current, or are not connected, or are isolated, the chassis could float up to line potential in event of a fault. Depending on the construction and probablity of a fault that energizes the chassis, this may or may not be a significant safety hazard.
If you leave the earth connection in place, but "lift" it with a resistor, antiparallel diodes, or combination, the signal grounds are isolated from the earth connections. But the chassis still has an effective, high current path to earth, which prevents it from ever floating to an unsafe level.
Sheldon
edit: even used in some sophisticated measuring gear (page 10): http://richpc1.ba.infn.it/~atauro/infn/grounding/Earth.pdf
markus76 said:
That would be a big mistake, since in the modal region one cannot make any assumptions about how the mains will work at the "crossover" point. They have to be part of the calibration or it isn't a calibration of the system.
New spectrogram with findings that might surprise some people here. This time the DVD "Slumdog Millionaire" (chapter 4, ≈4 min)—C, L and R:
Best, Markus
An externally hosted image should be here but it was not working when we last tested it.
Best, Markus
And It uses FIR filters !
But only two sub outputs...
What is the price tag for the JBL BassQ ?
But only two sub outputs...
What is the price tag for the JBL BassQ ?
pos said:
Thats a joke, right? I wouldn't want FIR filters because of the group delay. For good LF resolution FIRs would have quite long delay times.
Audyssey Xt
Since I've already used Dr. Geddes placement and mike sweeping methods with my 4 12" subs, placed as recommended, and I have Audyssey multiEq XT on my Denon receiver already in use, I'm not sure what all the fuss is about.
Dr. Geddes method works pretty well, I have even, deep, and subjectively robust bass throughout the listening area; the only dead spots are in one corner near the front of the room opposite the corner sub, and reduced bass on top of my coffee table. All listening locations sound smooth and refined... and deep, with little if any doubling distortion I've always found annoying (as in, you know there's deep bass, but all you can do is imagine it)
All 4 sonosubs I built combined for less than the cost of the unit listed. The Denon wasn't cheap, but it's multi-zoned, upconverts std. dvd's to high quality images, and meets all my other needs (except the primary remote sucks).
John L.
Since I've already used Dr. Geddes placement and mike sweeping methods with my 4 12" subs, placed as recommended, and I have Audyssey multiEq XT on my Denon receiver already in use, I'm not sure what all the fuss is about.
Dr. Geddes method works pretty well, I have even, deep, and subjectively robust bass throughout the listening area; the only dead spots are in one corner near the front of the room opposite the corner sub, and reduced bass on top of my coffee table. All listening locations sound smooth and refined... and deep, with little if any doubling distortion I've always found annoying (as in, you know there's deep bass, but all you can do is imagine it)
All 4 sonosubs I built combined for less than the cost of the unit listed. The Denon wasn't cheap, but it's multi-zoned, upconverts std. dvd's to high quality images, and meets all my other needs (except the primary remote sucks).
John L.
gedlee said:
8.5ms delay. I couldn't resist starting a discussion with the SVS guy—you might want to join us at http://www.hometheatershack.com/forums/svsound/16738-astounding-new-eq1-subeq-goes-sale-6.html
Best, Markus
Markus
I'm not dumb enough to jump into a love fest like that. Just look at the title of the thread - its not objective at all. No one there wants to know the truth, they just want to hear others applaud the product, not question it.
The delay thing, which simply goes away if you use IIR filters, and the lack of understanding of how the mains need to be part of the calibration. There is no real recognition of the details of the problem. Requiring that ALL speakers have an f3 of 80 Hz - thats real practical.
I'm not dumb enough to jump into a love fest like that. Just look at the title of the thread - its not objective at all. No one there wants to know the truth, they just want to hear others applaud the product, not question it.
The delay thing, which simply goes away if you use IIR filters, and the lack of understanding of how the mains need to be part of the calibration. There is no real recognition of the details of the problem. Requiring that ALL speakers have an f3 of 80 Hz - thats real practical.
You bad! I can't get away with that kind of thing, not in my position. Let me know if they say anything interesting, but I will probably stay out.
How practical is is to use ported mains as part of the lf solution?
My understanding is that you would need sealed mains that start to roll of up in the 150Hz range to successfully cross them with the lf subs.
My understanding is that you would need sealed mains that start to roll of up in the 150Hz range to successfully cross them with the lf subs.
fredk1 said:
I don't think that its optimum, but I also don't see any reason why it wouldn't work. Remember, I don't "cross" the mains to the subs, they overlap. Ported should work OK.