Some FR Measurements of 4" Pioneers
Here is a chart of the frequency response measurements of four different speaker systems made using the PE closeout 4" Pioneer drivers.
Basic Test Equipment:
* Radio Shack Analog SPL Meter
* Rives Audio Test CD 2 with Radio Shack meter compensation
* Response measured "in room" with no attempt to create a good listening environment
* BrianGT Gainclone
* Aiwa DVD player
* The SPL meter was mounted on a tripod 79" (2 meters) from the plane of the speaker baffles centered between the speakers.
* The microphone opening of the meter was 22 inches (~56cm) above the floor
* I sat behind and to the right of the meter during measuring
* The small speakers (MDF and Birch) were stacked with the speaker being measured on top. This put the tweeters of those systems 20" (~51cm) above the floor
* The "arrays" are floor standing models
* Speakers faced forward, no toe-in
* SPL meter was set for the 80dB range
* The 1K Hz track (RS compensated) was played and volume adjusted until the meter read 0dB
* Each track was played in succession and each reading noted
* Entire sequence was repeated 3 times for each set of speakers and readings were averaged
* Graph was created in Excel. +12 to -12 dB Y axis
* No smoothing applied
Pretty interesting. These drivers have similar curves regardless of the enclosure size and shape. In the small speakers the drivers' spike at around 7K is pretty obvious. It is lessened somewhat in both arrays. The large "array" (6 drivers) has the flatest overall response.
My middle aged ears have spent too many hours listening to Mott the Hoople at too high a volume. I have slightly depressed upper midrange acuity so bright speakers tend to sound better to me.
What can we learn from this? Probably not much. The test was conducted in room, I have not calibrated the meter or the amplifier. It is useful though as a direct comparison between the speaker's I've built in this single room. It may also yield a little info about enclosures but don't count on it!
I measured my line array TL ( uses eight of these) outdoors, flat within plus,minus 2dB from 100 to 6 kHz. Pretty impressive for chump change.
Speaker photos and measurements
I'll post photos of the speakers a little later if anyone is interested.
* MDF and Birch have identical internal volumes of .11 cu.ft.
* The MDF is 5/8", the birch is 3/4".
* Each have one 4" driver and one Goldwood $1.95 tweeter
* "Crossover" is just a highpass filter with a 1uF Solen cap
* Ports are 1" dia. 1.5" long on both
* Outside dimensions of birch 5 1/4" x 7 1/2" x 11 1/4"
* 5/8" particle board
* 4 drivers mounted from inside with no rounding over of the holes.
* 1 Goldwood tweeter
* 2.2 uF cap for highpass
* 1 rectangular port 1/2" high, 5/8" deep, 7" wide
* Outside dimensions 5 7/8" deep, 10 1/4" wide, 37 1/2" high
* 5/8" MDF
* 6 drivers flush mounted 4 1/16" on center
* 2 Goldwood tweeters
* 1uF Solen cap for highpass
* 2 ports, 3" dia. 2 1/2" long
* Outside dimensions 9" deep x 13 1/4" wide x 49 1/2" high
I plan to repeat this all outdoors, weather permitting, within a week. It will be interesting to see the response then. I'm thinking for all of these systems I may need a notch filter to even out the response. That or using a quality tweeter and a real crossover.
The rising response at 7kHz is moot, since the dispersion off-axis collapses above 6kHz anyway. You need tweeters.
OK, here is a photo with all the speakers. The smaller arrays are just covered in a wood grain contact paper. The larger arrays are covered with the "cherry" woodgrain vinyl laminate from PE. The birch speakers are natural finish with tung oil and the small MDF speakers are just sprayed black.
I would suggest also getting a sweep with the speakers toed in and pointing at the microphone, or better yet, you don't actually need to test both speakers. Just do one and have the mic two or three meters/yards in front of it and then same distance off axis if that helps relate to the previous set of measurenments. IMO the sweep will be most meaningful if it is measured at the distance you find the line array phases into focus. I find with my larger arrays this distance can easily be four meters.
I listen to all my array speakers pointed towards me. It is critical for the very best sound. When off axis walking around the room is almost as good I consider the design a re-sound-ing success.
was more than twice that much. :cool:
Can you open up any of those boxes (or rather, remove the baffle)?
small box interaction seemed (in my experiments) to introduce an interesting hump right where you're finding one (my experimentation was less scientific - sine wave sweeps and my ears).
I end up putting ~.3 cubic feet each driver.
But open baffle is where I like them most.
Some crossed at 3200hz, some at 3800hz. :)
I do have a case of these (32) left so I can continue playing with different designs. I think my next set will be a nine driver line array with a much smaller volume. Like this one-
I don't yet know how I'll mount tweeters though. I suppose I could just mount them at the top but that would make the high-end a point source while the lower end is an array.
Any ideas how that would work?
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