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Speaker Asylum General speaker questions for audio and home theater. |
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Speaker Asylum General speaker questions for audio and home theater. |
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In Reply to: RE: As An Observation, Looking at Your Rig - Not With Your Speakers... posted by thetubeguy1954 on October 19, 2010 at 08:33:04:
Hi
“I'm presently using a pair of 15" Hawthorne Audio OB "Augie" woofers in my system to cover from 100Hz and lower. In addition to that, in the past I've had Hartley 24" woofers and still have a single Harley 18" woofer at present. So I've "heard" what I believe to be bass.”
I am sure you heard something BUT…..
An open baffle cannot couple to your room gain slope by virtue of the fact that the larger the wavelengths get, the closer the two phases are and more completely they cancel out. The Hartley woofers were impressive…once. Now one can easily exceed their performance in a smaller space.
A suggestion for a DIY project.
Take your rooms longest dimension, find the frequency where that distance is 1 / 2 wl (sound travels about 1132 feet /sec).
Look for 12 or 15 woofer with a low Fs and large Xmax (like 10mm or more. DO NOT consider power handling, brand or studly looks.
Model each of these in a sealed box of a volume you would accept in your room (some people don’t mind a refrigerator in the corner).
Pick the one that gives the low corner knee nearest your theoretical room number and nicest shape. If you have a giant volume, try two drivers.
Overlay these, it is easier to see the figure of merit for each when you consider the model predicts at a given voltage or power, so the area under each curve is what you want. An alignment that is say 6dB higher along the low roll off slope with a lower overall or upper range sensitivity may be what fits your room better, your looking for LOW bass now, part of that is the roll off slope.
IF you have a suitable crawl space or an opening into another space you can use, then mount the driver in the wall or floor. With a much larger volume behind the speaker, it is much easier to get the Fb close to Fs in line with a large room.
What may not be optimal here is the Q or shape of the low corner. If one has an amplifier where you can adjust the output impedance (was often a damping factor control), then one can easily raise the Q to result into a optimally flat response.
Alternately, a series R will have the same effect although throws away some power.
The goal being that you align your low corner with the rooms estimated lowest mode. This makes the speakers roll off compliment the room gain in the smoothest way. If you can do this with “enough” capacity, the effect is not subtle and you will likely find there is vlf content you have never heard in many things. Understand this frequency extension IS NOT anything like "Turning the subs up"
It is true real rooms do not have the theoretical 12 dB / octave rise that a sealed concrete bunker has, the rooms I have measured tended to be more like 3 to 9 dB per octave. Still, the more one can take advantage of the room gain, the less volume you must displace to have a meaningful signal. By meaningful, I mean that until one reaches and exceeds the threshold of hearing, and then masking, there is no point is even producing the very low frequencies.
Without sufficient fundamental capacity, one produces much too much upper harmonic spectrum often leading to the conclusion that adding a subwoofer muddies the sound. Well, in that case, it does but not from the low frequency output but rather the much more audible harmonic distortion.
Lastly, cross this into your system as high in frequency as possible as the lower the crossover F and or greater slope, the greater the crossover delays involved are. Given what your crossing into doesn't have a defined / measured phase response i have seen, trial and error listening should govern the selection.
With TEF measurements a passive or with a loudspeaker controller, an exact electronic crossover solution is possible.
Best,
Tom
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Follow Ups
- RE: As An Observation, Looking at Your Rig - Not With Your Speakers... - tomservo 12:16:31 10/19/10 (3)
- I Need More Help To Understand - thetubeguy1954 08:29:42 10/20/10 (2)
- RE: I Need More Help To Understand - tomservo 09:45:35 10/20/10 (1)
- Thanks Tom. I Have A Couple Of More Questions, Ok? - thetubeguy1954 13:34:03 10/20/10 (0)
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