This is a case of a bunch of things coming together in an unplanned manner. I'm interested in your thoughts on several fronts, both component selection and design.
Goal: Drive-In speakers - DC-powered 105dB SPL, low distortion, FM radio/MP3 player
Approach: Dayton Point Source drivers and Chinese digital amp in Triska-sized split box
A recent thread had a link for a Chinese "car/motorcycle" (i.e. 12VDC) FM radio, USB card reader amp. I have no idea why I was moved to order one, a Lepai LP-V9, and fit it, a battery and speakers into a box I already had.
- the amp:
UPDATED LINK (same unit, different vendor)
- the box was for an oversize Triska sub. Built 2 for my kids, and parts for a third cut out of the same sheet.
- the Singularities showed that a simple shelf filter makes the PS220 a very nice, high sensitvity speaker
- a high senstivity speaker would get quite loud with 10-20W, a realistic output of these DC amps
- the PS220 was a drop-in replacement for my pre-cut wood, but modeled poorly at 10-12 liters
- the PS180 modeled nicely ported with a 75-80Hz tune; I made inserts (see pics, eventually)
- for other reasons, I had a 7amp-hr battery available along with maintenance charger
- PE had a 2A power supply on sale, and it got me free shipping on 1 PS180 driver
- my 13x13.5x14" oversize Triska design lets me retain 11.4L speaker volume after fitting amp and battery
So… I submit for your perusal and comment, the Drive-Ins, a PS180-based, high sensitvity speaker with a simple LR contour network. As documented for the PS220's in the Singularities, the smaller drivers are also very senstive, but with rising, ragged and narrow (if extended) high frequency output. Without a contour filter, they squalk on-axis, but smooth right out a few degrees off-axis, about the point where the high's go away. The polar behavior is very sharp.
I used a UFO202 with my laptop, REW 5.0 and a Xenyx 802 mixer/ECM8000 mic for the measurements. Driver response rises above 3KHz, and is increasingly ragged, so I used 1 octave smoothing to evaluate the results of a simple shelf filter. I show 1/3 octave smoothing, with and without contour filter, and final on-axis, 15 and 30 degrees off axis.
PCD shows unsmoothed data, rags and all as you would see in the PDF if the file weren't too big to attach. The contour filter is a parallel LR, 0.3mH and 20 ohms at this stage. No attempt to address raggedness, just suppress the peaky 3K-10KHz region without losing too much of the top octave on-axis, given how quickly it goes away off-axis.
Note that I did the measurements in-box (13wx14h", centered 1" up on long side), and with an active port. I've attached a Unibox plot, but will note this driver comes in with an Fs of 66Hz vs. 48Hz spec and 40Hz Kippel. My WT3 is suspect (1K resistor doesn't always measure 1K ohms), but this design only uses the flat upper part of the impendence curve. Bass output, however, is more consistent with the measured Fs.
The pair of speakers fit together so that the amp and battery can be mounted in the space between their back panels. Close it up with yet-to-be-ordered butterfly clamps and I'll protect the drivers with metal grills like for my Triska's. Open it at the drive-in, set them 10' apart and tune the radio to the local movie frequency. At parties, hook an iPod up to the RCA jacks. I'll get pictures once I have all the hardware.
So, comments welcome on the speaker design, and… I've heard good things about Lepai amps, and this one has the right combination of features and capabilities. Anyone have any experience with Lepai? Am I barking up the wrong tree somehow?
Have fun,
Frank
Listening impressions once I get a pair....
Goal: Drive-In speakers - DC-powered 105dB SPL, low distortion, FM radio/MP3 player
Approach: Dayton Point Source drivers and Chinese digital amp in Triska-sized split box
A recent thread had a link for a Chinese "car/motorcycle" (i.e. 12VDC) FM radio, USB card reader amp. I have no idea why I was moved to order one, a Lepai LP-V9, and fit it, a battery and speakers into a box I already had.
- the amp:
UPDATED LINK (same unit, different vendor)
- the box was for an oversize Triska sub. Built 2 for my kids, and parts for a third cut out of the same sheet.
- the Singularities showed that a simple shelf filter makes the PS220 a very nice, high sensitvity speaker
- a high senstivity speaker would get quite loud with 10-20W, a realistic output of these DC amps
- the PS220 was a drop-in replacement for my pre-cut wood, but modeled poorly at 10-12 liters
- the PS180 modeled nicely ported with a 75-80Hz tune; I made inserts (see pics, eventually)
- for other reasons, I had a 7amp-hr battery available along with maintenance charger
- PE had a 2A power supply on sale, and it got me free shipping on 1 PS180 driver
- my 13x13.5x14" oversize Triska design lets me retain 11.4L speaker volume after fitting amp and battery
So… I submit for your perusal and comment, the Drive-Ins, a PS180-based, high sensitvity speaker with a simple LR contour network. As documented for the PS220's in the Singularities, the smaller drivers are also very senstive, but with rising, ragged and narrow (if extended) high frequency output. Without a contour filter, they squalk on-axis, but smooth right out a few degrees off-axis, about the point where the high's go away. The polar behavior is very sharp.
I used a UFO202 with my laptop, REW 5.0 and a Xenyx 802 mixer/ECM8000 mic for the measurements. Driver response rises above 3KHz, and is increasingly ragged, so I used 1 octave smoothing to evaluate the results of a simple shelf filter. I show 1/3 octave smoothing, with and without contour filter, and final on-axis, 15 and 30 degrees off axis.
PCD shows unsmoothed data, rags and all as you would see in the PDF if the file weren't too big to attach. The contour filter is a parallel LR, 0.3mH and 20 ohms at this stage. No attempt to address raggedness, just suppress the peaky 3K-10KHz region without losing too much of the top octave on-axis, given how quickly it goes away off-axis.
Note that I did the measurements in-box (13wx14h", centered 1" up on long side), and with an active port. I've attached a Unibox plot, but will note this driver comes in with an Fs of 66Hz vs. 48Hz spec and 40Hz Kippel. My WT3 is suspect (1K resistor doesn't always measure 1K ohms), but this design only uses the flat upper part of the impendence curve. Bass output, however, is more consistent with the measured Fs.
The pair of speakers fit together so that the amp and battery can be mounted in the space between their back panels. Close it up with yet-to-be-ordered butterfly clamps and I'll protect the drivers with metal grills like for my Triska's. Open it at the drive-in, set them 10' apart and tune the radio to the local movie frequency. At parties, hook an iPod up to the RCA jacks. I'll get pictures once I have all the hardware.
So, comments welcome on the speaker design, and… I've heard good things about Lepai amps, and this one has the right combination of features and capabilities. Anyone have any experience with Lepai? Am I barking up the wrong tree somehow?
Have fun,
Frank
Listening impressions once I get a pair....
Comment