From the FR curves, it looks like Art may be right concerning the size of the enclosure and the size of the vents. An impedance response curve would help to confirm this.
Note: close-miked response curves for woofers should really be done with the mike within an inch of the cone. Likewise for vents. The mike should also not be placed inside the vent - in the case of small vents, this could alter the tuning a bit.
100%
100% TRUE (that)
I just chose a 4 inch for my example because it's the size I hear wild claims about most often.
p.s. An eight inch is a nice size for a wide-band driver.
100% TRUE (that)
I just chose a 4 inch for my example because it's the size I hear wild claims about most often.
p.s. An eight inch is a nice size for a wide-band driver.
It is probably the sweet spot for a FR, but they cannot move a lot of air. Even when LF extention is much the same a larger driver gives more impact.
It should be mentioned that there are also very few 10 octave multi ways.
dave
What ya talking about. I gota 4inch that plays perfect to 17000 and outputs 145db at 16hz with only 2mm of cone excursion in a bathroom sink with 1watt of input power.
Well, I found that the bass sounds a lot better if you place the enclosure with the driver facing into the corner of the room, or place it oriented vertically. It seems that having the port face the opposite way from the driver, which I have never done before, makes the room acoustics much more important to the apparent frequency response than when the port and driver are facing the same way.
It's been pretty rainy here so I unfortunately haven't had a chance to do an outdoors frequency response measurement.
@Brian Steele, when you say that the box and ports are undersized, I'm not sure I understand exactly what you mean. Does the driver simulation fail when boxes and ports get small? Or are you suggesting that the ports and enclosure are smaller than the values that I used in the simulation? I thought I measured them fairly well but it was all cut by hand so there is some error.
It's been pretty rainy here so I unfortunately haven't had a chance to do an outdoors frequency response measurement.
@Brian Steele, when you say that the box and ports are undersized, I'm not sure I understand exactly what you mean. Does the driver simulation fail when boxes and ports get small? Or are you suggesting that the ports and enclosure are smaller than the values that I used in the simulation? I thought I measured them fairly well but it was all cut by hand so there is some error.
The prototype Babb Loreleis I have did it and at a surprisingly high average/peak SPL, especially considering its very low efficiency. Certainly loud enough for most HIFI/HT apps and if Alan wasn't BSing me, they could play even louder since he claimed his had been long term tested at 400 W whereas Jim Griffin's amp [receiver?] was around 250 W IIRC.
A real pity he wasn't allowed to continue to refine it and DC Gold apparently changed it for more efficiency over a narrower BW like their [Babbs's] other drivers.
GM
Absolutely! The vent needs to be at an odd eigenmode in the vertical dimension, i.e., 3rds, 5ths, etc., so at other locations it's somewhere in a null to a greater or lesser extent, which can't be EQ'd away. Being near/at the floor, wall or corner puts it where there's the most reinforcement [1st mode].
Maybe this will help with understanding room acoustics: Auditorium Acoustics
GM
..........and why I always promote large cabs tuned lower than T/S predicts to account for VC heating, etc., when > ~1/4 rated power is required to get the desired levels [pretty much always with today's low efficiency drivers].
This one needs at least 50 L [and more if Qts is > published] tuned ~22-27 Hz [depending on room/boundary gain] to go low unless crammed into a corner and even then it needs to be located along a wall at an odd room eigenmode.
Worst case is one might have to damp the port if it has any obvious 'boom'/'loose' sound to it.
GM
It means that the (1) the box size is too small to get the best from the driver in that ported alignment, and (2) the ports are too small for the alignment to maintain the same frequency response as the power level is increased. Ports are non-linear, and the smaller they are, the more non-linear they are.
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