I need a very high quality and loud mid range for my system. Big and powerful single drivers usually don's sound usually very detailed or natural and they beam of course at higher frequencies. The smaller ones sound unnatural at lower frequencies and the sound becomes easily distorted and the driver easily might overheat at higher power levels.
I initially thought about putting four mid range drivers in a circle, but that still would have the beaming problem and I was not sure if even four small drivers would have the amazing dynamics I am looking for.
So that basically left me just one option, a line array. I now built one speaker quickly, just to test it. I used eight 6" SB17nac35-8 ohm drivers because of their really good sound quality and they are now taking care of 200 - 3000 hz area quite well.
The speaker is 2.0 meters (6.5ft) high and those eight drivers produce a sweet spot vertical listening window of about 90cm (3ft) high according to my listening. Horizontally, it's very nice and wide as you can probably guess since I am using 6" drivers.
I am very pleased with the result, this was the right choice for me and now I just want to build the final version. However I am not sure how many drivers is the optimum.. I could just do a bunch of test speakers, but I would rather skip that if you can guide me.
Based on my listening I need at least two more, so that would be 10. And since I am running the speaker to 3 khz I will also cut a slice of each driver from top and bottom to bring them closer to each other for more uniform sound field and for a little bit more higher power density. After cutting, the height would be 150mm instead of the 171mm that it's from the factory.
The maximum amount would be 16 drivers, since I don't wan't to make the speaker any higher than that. Naturally I would go for that amount, since the longer array is beneficial for the directivity, but I am worried how lowest and the highest drivers are more far away from the listener than the ones in the middle. Could that become a problem? Right now, with eight drivers it's not an issue to me, I hear the details very clearly. I could also assign two more channels in the crossover and the amplifier to delay the eight center drivers to compensate a bit.
Which amount would you choose and why?
I initially thought about putting four mid range drivers in a circle, but that still would have the beaming problem and I was not sure if even four small drivers would have the amazing dynamics I am looking for.
So that basically left me just one option, a line array. I now built one speaker quickly, just to test it. I used eight 6" SB17nac35-8 ohm drivers because of their really good sound quality and they are now taking care of 200 - 3000 hz area quite well.
The speaker is 2.0 meters (6.5ft) high and those eight drivers produce a sweet spot vertical listening window of about 90cm (3ft) high according to my listening. Horizontally, it's very nice and wide as you can probably guess since I am using 6" drivers.
I am very pleased with the result, this was the right choice for me and now I just want to build the final version. However I am not sure how many drivers is the optimum.. I could just do a bunch of test speakers, but I would rather skip that if you can guide me.
Based on my listening I need at least two more, so that would be 10. And since I am running the speaker to 3 khz I will also cut a slice of each driver from top and bottom to bring them closer to each other for more uniform sound field and for a little bit more higher power density. After cutting, the height would be 150mm instead of the 171mm that it's from the factory.
The maximum amount would be 16 drivers, since I don't wan't to make the speaker any higher than that. Naturally I would go for that amount, since the longer array is beneficial for the directivity, but I am worried how lowest and the highest drivers are more far away from the listener than the ones in the middle. Could that become a problem? Right now, with eight drivers it's not an issue to me, I hear the details very clearly. I could also assign two more channels in the crossover and the amplifier to delay the eight center drivers to compensate a bit.
Which amount would you choose and why?
Eventually I did build a 16 drivers per speaker array, and since I had noticed there was some combing around 3 khz with the standard center to center distance of the 6.5" drivers I cut a slice of on top and bottom of each driver to make them become more uniform. And it worked! the problem pretty much disappeared, I was very pleased so I highly recommend doing the same.
Here are some of the drivers waiting for the modifications
First I tried simply sanding the extra material off, but that was very slow, overheated the driver with friction, created lots of messy dust and ruined the sandpaper quickly.
Then I moved on to using circular saw with a high quality blade which worked much better. But you have to have a rigid jig for the driver of course to make the cuts identical from driver to driver.
Here are some cut drivers on a table, notice how much closer they now are. Driver height (when installed on a speaker) went from 171 mm to 150 mm.
Here are some of the drivers waiting for the modifications
First I tried simply sanding the extra material off, but that was very slow, overheated the driver with friction, created lots of messy dust and ruined the sandpaper quickly.
Then I moved on to using circular saw with a high quality blade which worked much better. But you have to have a rigid jig for the driver of course to make the cuts identical from driver to driver.
Here are some cut drivers on a table, notice how much closer they now are. Driver height (when installed on a speaker) went from 171 mm to 150 mm.
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Finally to answer my original question how many drivers would be best, well first the 8 drivers was not high enough for an array, even with the 171mm C 2 C distance. And now with 16 drivers with reduced distance the total sound producing height of the center of the lowest driver to the center of the highest driver is about 223 cm (7 feet 3.8") and that feels a bit on the high side. I think I can hear some of the drivers being closer and some more far from me when I move around the room, there is a littlebit less clarity than with eight drivers. But of course the more far away you listen from the better it is. Perhaps the number I would recommend people to use would be 12, that's pretty much the sweet spot with this size driver. However if you know you sometimes need to play some really loud and clear music at outdoor parties in a big area, I think 16 pcs is the right amount for that.
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I know how it feels, cutting drivers... I did it with hand tools though. I didn't dare use power tools.
I'm using these 3.5" full range drivers for the full bandwidth, from about 200 Hz and up to ~18 to 19 KHz. With shading/filtering, so only the center 5 play the full range, the lower in frequency you go, the more drivers are coming in to help out the bottom end.
Vituixcad is a good tool to "see" what's going on if you want to play with these type of frequency dependent shading filters.
In a thread started by nc535 we tried all kinds/sorts of array shading schematics. I've implemented a version of it in the above array.
I'm using these 3.5" full range drivers for the full bandwidth, from about 200 Hz and up to ~18 to 19 KHz. With shading/filtering, so only the center 5 play the full range, the lower in frequency you go, the more drivers are coming in to help out the bottom end.
Vituixcad is a good tool to "see" what's going on if you want to play with these type of frequency dependent shading filters.
In a thread started by nc535 we tried all kinds/sorts of array shading schematics. I've implemented a version of it in the above array.