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For my next project I’m thinking about making some rather small speakers for use in an office-based system. Maximum size on the order of ~6.5” wide x 10” tall x 8” deep. And try to make as high end of a design as possible with low distortion and such. Given that the listener will be closer to the speakers than is typical, there are some design considerations that may need to be accounted for. So I’m hoping to get a discussion going on the topic of near field, small speakers.
Some of the considerations that I’ve been thinking about so far…
-Near field: Let’s say the listener will be about 3 feet/1 meter from the speakers. We don’t want to hear the tweeter and woofer separately, as we move our heads. And that might be an issue with “regular sized” speakers (e.g., 7” woofer and tweeter with a 4” flange = 11” height the sound comes from) at such close distances. So the total area of the tweeter and woofer should be small. For a reference, I am currently using these computer speakers from Klipsch:
Quite good for what they are and what they cost. From the top of the tweeter to the bottom of the woofer is about 5”. The 2 drivers blend together well. So that gives some idea of a tweeter + woofer height/size that can work.
-Overall design: An MT. The size probably limits us to an MT, 2-way. Alternatively we could use teeny (e.g., 3”) drivers in an MTM. But there are more options for higher quality drivers if we go to bigger M’s so let’s say it will be MT.
-Tweeter: Pick one with a small flange. Something with a diameter of, say, ~2” rather than the more typical ~4” of most tweeters. Many such tweeters exist. The problem here is that there are few small flanged tweeters of very high quality/low distortion, etc. (Vifa says the D26 is discontinued so I’m leaving that out.)
-Woofer: Small is better for these small sized speakers and we want all the sound coming from a smaller area. But then bass extension suffers. We just need to get down low enough to match with a sub. After some modeling I did, let’s say a woofer of about 5” would be good. Lots of options for high quality woofers of this size.
-Overall size: With a 5” woofer (plus flange and space to tweeter, call it 6”) and a 2” tweeter, all the sound could be coming from an area about 8” tall. Add some wood on the top and bottom, edge treatments, etc. and you get a minimum height of around 9-10”. And a minimum width of 6.5-7” to accommodate the woofer.
-Coaxial drivers can be a consideration. All the sound coming from a relatively small area. But I’m not aware of any really high quality coaxial to compete with high quality “regular” drivers. And my guess is that coaxials will have various issues, with the woofer moving in and out so much while the tweeter is trying to do its thing.
-Full range drivers could be good for this application. If there were any really good ones available. But the crossover industry is still going strong.
-Bass extension. With such small speakers there is going to be a definite need for a sub. So the speakers need to have flat output down to ~80 Hz.
-Port: If one is used it will have to be in the front. Because speakers like this will most often be pushed up against a wall or shelf. Slot ports might look prettier than a circular port on the front baffle.
-Crossover: I read somewhere (forgetting where) that near field speakers should use second- or fourth-order Linkwitz-Riley crossovers. But I didn’t see any explanation as to why.
-Baffle step compensation: Just take into account that the speakers will often be up against a wall. Take the raw driver measurements accordingly.
OK, that’s what I’ve got for design considerations so far. Feel free to chime in.
Some of the considerations that I’ve been thinking about so far…
-Near field: Let’s say the listener will be about 3 feet/1 meter from the speakers. We don’t want to hear the tweeter and woofer separately, as we move our heads. And that might be an issue with “regular sized” speakers (e.g., 7” woofer and tweeter with a 4” flange = 11” height the sound comes from) at such close distances. So the total area of the tweeter and woofer should be small. For a reference, I am currently using these computer speakers from Klipsch:
Quite good for what they are and what they cost. From the top of the tweeter to the bottom of the woofer is about 5”. The 2 drivers blend together well. So that gives some idea of a tweeter + woofer height/size that can work.
-Overall design: An MT. The size probably limits us to an MT, 2-way. Alternatively we could use teeny (e.g., 3”) drivers in an MTM. But there are more options for higher quality drivers if we go to bigger M’s so let’s say it will be MT.
-Tweeter: Pick one with a small flange. Something with a diameter of, say, ~2” rather than the more typical ~4” of most tweeters. Many such tweeters exist. The problem here is that there are few small flanged tweeters of very high quality/low distortion, etc. (Vifa says the D26 is discontinued so I’m leaving that out.)
-Woofer: Small is better for these small sized speakers and we want all the sound coming from a smaller area. But then bass extension suffers. We just need to get down low enough to match with a sub. After some modeling I did, let’s say a woofer of about 5” would be good. Lots of options for high quality woofers of this size.
-Overall size: With a 5” woofer (plus flange and space to tweeter, call it 6”) and a 2” tweeter, all the sound could be coming from an area about 8” tall. Add some wood on the top and bottom, edge treatments, etc. and you get a minimum height of around 9-10”. And a minimum width of 6.5-7” to accommodate the woofer.
-Coaxial drivers can be a consideration. All the sound coming from a relatively small area. But I’m not aware of any really high quality coaxial to compete with high quality “regular” drivers. And my guess is that coaxials will have various issues, with the woofer moving in and out so much while the tweeter is trying to do its thing.
-Full range drivers could be good for this application. If there were any really good ones available. But the crossover industry is still going strong.
-Bass extension. With such small speakers there is going to be a definite need for a sub. So the speakers need to have flat output down to ~80 Hz.
-Port: If one is used it will have to be in the front. Because speakers like this will most often be pushed up against a wall or shelf. Slot ports might look prettier than a circular port on the front baffle.
-Crossover: I read somewhere (forgetting where) that near field speakers should use second- or fourth-order Linkwitz-Riley crossovers. But I didn’t see any explanation as to why.
-Baffle step compensation: Just take into account that the speakers will often be up against a wall. Take the raw driver measurements accordingly.
OK, that’s what I’ve got for design considerations so far. Feel free to chime in.
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