Planar speaker project

[nerdorama]

Did a bit more measurement work yesterday and today. I couldn't duplicate the FR that's posted in the ebay ad. I kept getting a lot of HF rolloff. A downward slope starting at under 1kHz and continuing all the way through the treble. In the middle of the night I wondered if the felt which is glued on the back could be a cause. I took one of my extra units and peeled it off. It came off pretty easily. Big difference as the measurements were now very smooth from 700Hz to about 17k. There is still a lower frequency hump below 1kHz but that could be something in my room or in my setup. Anyway my next step is to hook up the miniDSP to some amps and give 'em a try. Probably tomorrow as we have plans for the evening. Happy weekend.
John

 

[nerdorama]

Listened in mono with the miniDSP as crossover. Don't know about relative polarity but I could hear a clear difference when flipping polarity on the woofer in the DSP. Promising so far but I'll know more tomorrow in stereo. Transients like drum hits and rims and symbol whacks are really sharp. I used both channels of my test amp so I didn't have to worry about mismatched channels between woofers and planar. I'll need to start with some measurements when I get different amps hooked up to each half as I won't really know if each amp is inverting or non and the relative gains.

 

[nerdorama]

More measurements yesterday. Listened in stereo today biamped thru minidsp with Heath W3's on the planars and SS on the woofers. 500Hz 24dB crossover and a few mild notch filters based on measuring. Enjoyed the session. More work to come.

 

[616]

How did the project work out? Satisfied with the GAS planners? Seems like quite a good deal if they deliver great sound.

 

[nerdorama]

I've only listened for a couple of hours but I liked them quite a lot. Dynamics and inner detail are good. I biamped them at 500Hz 24dB/oct with a minidsp. I also added some small notch filters to smooth out some minor peaks. I set this project aside for a while to work on a tube amp idea. I'll get back to these soon.

 

[Rick Owen]

I've only listened for a couple of hours but I liked them quite a lot. Dynamics and inner detail are good. I biamped them at 500Hz 24dB/oct with a minidsp. I also added some small notch filters to smooth out some minor peaks. I set this project aside for a while to work on a tube amp idea. I'll get back to these soon.

Why did you choose open baffle with these, any particular reason?

 

[nerdorama]

Just seems like the way to go with this sort of driver. I've had open baffle ribbons before and liked the sound. Just seems more 3D to me but the room plays into this with the back wave. As an aside, when I got them they had some sort of porous cloth glued over the backs. They measured with a decided downward tilt in the high frequencies. I think the cloth was meant to absorb the back wave when installed in a wall cavity as I assume they were mounted originally. When I removed this material the FR was much improved and more even.

 

[Rick Owen]

Just seems like the way to go with this sort of driver. I've had open baffle ribbons before and liked the sound. Just seems more 3D to me but the room plays into this with the back wave. As an aside, when I got them they had some sort of porous cloth glued over the backs. They measured with a decided downward tilt in the high frequencies. I think the cloth was meant to absorb the back wave when installed in a wall cavity as I assume they were mounted originally. When I removed this material the FR was much improved and more even.

Like when your near a mountan and you shout, and hear an acho?
I have always struggled with this conceptionally.
That is two of these in your picture, correct?

 

[saabracer23]

Just seems like the way to go with this sort of driver. I've had open baffle ribbons before and liked the sound. Just seems more 3D to me but the room plays into this with the back wave. As an aside, when I got them they had some sort of porous cloth glued over the backs. They measured with a decided downward tilt in the high frequencies. I think the cloth was meant to absorb the back wave when installed in a wall cavity as I assume they were mounted originally. When I removed this material the FR was much improved and more even.

If you could do it over again would you? I’m considering picking up a few pair, but I need more raw drivers like I need a hole in the head. I have several nice ribbons like Raal 140-15ds, Aurum Cantus, and a few others along with beryllium compression drivers, beryllium domes. But these has line array written all over them. Your comments lead me to believe that overall you’re pleased, but maybe not as impressed as you thought you might be????

Dan

 

[nerdorama]

Don't get me wrong. I do like them a lot. Just not into too much superlative when describing things. They are a fun project. I have to admit that I was hoping, but not really expecting, a bit higher sensitivity. Was hoping that I could work up a passive crossover. Made the electrical and acoustic measurements and put them into Xsim. Had a hard time finding a crossover scheme that gave me a reasonably flat FR and an impedance curve that didn't dip too low. That's when I decided to press on with the minidsp and biamp. The result sounded great but biamping adds system complexity and it's harder to try different amps, which I seem to do often enough, since you have to readjust the balance between hi and low. I'm mostly a tube amp guy so the flat impedance of the ribbons is an additional attraction.

@saabracer23 , since you are in PNW, if you can visit the seller in Renton I think you can work a cash deal. We can do a PM and I can give you his contact info. Originally he also had them on Seattle craigslist which is how I contacted him. My problem is similar, I need more projects like a hole in the head but I'm a sucker for one that seems like it will be fun.
John

 

[getdadams]

Bought 2 pair of these to do exactly what you did, open baffle with pair of OB woofers crossed over using a minidsp. Using wings like Danny at GR for the rear wave. I’ve found it very hard to get useable measurements on a line array.
Below is current experiment using Monsoon and GRS planar drivers.
I’ll be making a new baffle to hold the GAS drivers for this setup.

 

[nerdorama]

Nice project. How did you come by that many Monsoon drivers? I need to get back to this project but I've been working on a tube amp lately.

 

[getdadams]

Nice project. How did you come by that many Monsoon drivers? I need to get back to this project but I've been working on a tube amp lately.

Bought them on eBay like the GAS planar drivers.
The top section of my speakers comes off the mid bass section so I can unscrew the wings and put a new baffle in. Fun to play

 

[getdadams]

I was curious why you crossed these over at 500Hz. With 2 of these per side, I’m hoping to go closer to 200Hz.

 

[StimpyWan]

I was curious why you crossed these over at 500Hz. With 2 of these per side, I’m hoping to go closer to 200Hz.

VMPS RM Series speakers used those same Monsoon drivers. I believe Brian Cheney crossed his over at around 275Hz. But, that used 6dB first order slopes. So, the drivers should be able to go lower, with a steeper crossover.

Oh, I have a bunch of those drivers too. Spares for my Monsoon tower speakers. I've thought about building a line array, with them. The only thing holding me back, is I really don't need more speakers...!

 

[getdadams]

VMPS RM Series speakers used those same Monsoon drivers. I believe Brian Cheney crossed his over at around 275Hz. But, that used 6dB first order slopes. So, the drivers should be able to go lower, with a steeper crossover.

Oh, I have a bunch of those drivers too. Spares for my Monsoon tower speakers. I've thought about building a line array, with them. The only thing holding me back, is I really don't need more speakers...!

Sorry, I was referring to the GAS driver crossover point.
I’ve played around with Monsoon frequency. With 6 drivers, I’ve been able to get closer down towards 200Hz but can’t remember where exactly.

 

[nerdorama]

My last go 'round I had the crossover at 400Hz. The resonant frequency is around 125Hz and even though it is a very mild resonance it is normal to cross at least an octave or more above that point. Probably could do 250Hz without too much risk at 24dB/oct since the resonance is hardly noticeable on an impedance measurement. Next time I set them up I'll try 250Hz and see how it sounds.

 

[getdadams]

My last go 'round I had the crossover at 400Hz. The resonant frequency is around 125Hz and even though it is a very mild resonance it is normal to cross at least an octave or more above that point. Probably could do 250Hz without too much risk at 24dB/oct since the resonance is hardly noticeable on an impedance measurement. Next time I set them up I'll try 250Hz and see how it sounds.

Thanks! I’ll let you know when I can get baffles built and installed in speakers to try them out as well.
I’ll be using the 4x10 HD minidsp for crossover.

 

[getdadams]

One test baffle ready. Finishing a house project before I can do some measurements and work on minidsp filter.
I left room on baffle in case I decide to add tweeter array.

 

[getdadams]

Made some quick measurements with 2 drivers in parallel. The highs drop off severely after about 14k. Will be removing the felt backing as Nerdorama suggested and test again.