Debating on 3 way vs 4 way

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illcrx

Member
Joined 2022
#1
I am listening/designing my new speakers. 1.25" ScanSpeak Tweeter, 4" Dayton Reference Mid, 10" Morel Subwoofer. I am still auditioning drivers but it will be a couple of days until I can make a 4 way box and I was curious if anyone has any experience with a 4" to a 10" difference/gap. The 6" mids I auditioned were murdered in clarity by this 4" mid so I am going to keep it, and the 6" killed in the lower midbass! I am just worried it doesn't have the cone area to deliver the power of the lower mid bas. Here is my latest measurement at 1/12 smoothing and there are some nasty peaks/dips in there and the 100-250 area seems a bit low so I am thinking that is where a 6" would take over, I'll have to see when I get it mocked up. This is a hodgepodge of a setup right now with my mid being held in a too big box with some foam lol but I am enjoying the auditioning nonetheless!

I just wanted to get some thoughts if anyone has traveled this road.

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#7
You are definitely on the right track. Most midbass is distorted by IMD in sub bass unless the driver is losing out some other way or is incredibly expensive. This is normally a sub but you could stick it in a tower. Not sure it's easier that way.
 
#9
D1sco said:
You are definitely on the right track. Most midbass is distorted by IMD in sub bass unless the driver is losing out some other way or is incredibly expensive. This is normally a sub but you could stick it in a tower. Not sure it's easier that way.
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Can you elaborate please? It sounds like you are saying that some subs kill mid-bass. But what do you mean by "unless the driver is losing out some other way or is incredibly expensive." Are you saying that the sub should be very high quality/expensive to not have these distortions? Could these be related in some way to cabinet factors? The Sub is the Morel Classic Advanced 10", I have their Ultimo for car and its mindblowingly good. This isn't quite on that caliber but its also pretty good, not sure if fits in your super high quality category though.

The setup is in a tower and cannot be changed.
 
#10
Any driver that has a smaller bandwidth (say 20-80Hz or 2 octaves) will have less non-linear distortion than a driver with a wider bandwidth (say 20-160 Hz or 3 octaves) assuming the driver's are otherwise equal. In this instance then it's better to have more drivers covering a greater number of bandwidths (which practically speaking means 4-way is better than 3-way all-else-equal).

Note: that Morel driver has a LOT of mechanical resistance and a fairly high Mms for it's diameter - I would separately power that woofer with its own amp.
 
#12
ScottG said:
Any driver that has a smaller bandwidth (say 20-80Hz or 2 octaves) will have less non-linear distortion than a driver with a wider bandwidth (say 20-160 Hz or 3 octaves) assuming the driver's are otherwise equal. In this instance then it's better to have more drivers covering a greater number of bandwidths (which practically speaking means 4-way is better than 3-way all-else-equal).

Note: that Morel driver has a LOT of mechanical resistance and a fairly high Mms for it's diameter - I would separately power that woofer with its own amp.
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So centering the driver around its "sweet spot" is a good idea it sounds like. So a sub doing 20-80, mb 80 to 320, mid 320 to 4k in my case and tweeter from 4k up. So more than 2 octaves on the mid but its not really feasible to do an 5-6 way! I may ditch the Morel, in my recent listening sessions its not keeping up. Any tips on how to find a good sub that will 'keep up'?
 
#14
Sub can be placed anywhere. That's the point of the low enough crossover to not be able to localize it. You can have your 3way lean tower, well placed, good looking... plus the sub, or two, hiding in the corner or someplace else. It can even be used as small table fulfilling double duty.

Your 4.5 cu ft is plenty to reach the 80Hz or so.

Proper sub? That's totally up to you. I would go one 15".
 
#15
illcrx said:
Can you elaborate please? It sounds like you are saying that some subs kill mid-bass. But what do you mean by "unless the driver is losing out some other way or is incredibly expensive." Are you saying that the sub should be very high quality/expensive to not have these distortions? Could these be related in some way to cabinet factors? The Sub is the Morel Classic Advanced 10", I have their Ultimo for car and its mindblowingly good. This isn't quite on that caliber but its also pretty good, not sure if fits in your super high quality category though.

The setup is in a tower and cannot be changed.
Click to expand...
Just the opposite, actually. Some woofers, when expected to play low, don't play midbass or mid particularly well at the same time. The superimposed signal is smeared by gross changes in the low range. Adding a sub can greatly ease this burden from the woofer that is also playing higher, in the midbass or even up to the midrange. If you design a competent two-way, it will be better with a sub. If you build a competent three-way, it will be better with a sub. Frankly, if you build a really good four-way, it may still benefit from a separate subwoofer. Separating it from the "mains" and changing it's position can help with your room's cancellation or rattling gains.

IMD, Inter-Modal Distortion, is a measure of this and is slowly becoming more common in measurements. There are a couple of ways to reduce IMD, sometimes the cheapest is the above method-- you don't ask a tweeter to play bass, A 10" can't necessarily play low and high in the same way a 7.5" or 4" can't. They're all compromises. Some of the most expensive drivers can't help you here, which is why multi-way speakers even exist. It's cheaper to throw more drivers and crossovers at the problem than to design the newest, hottest purifi woofer.

What I'm saying is, the principals you've abided by on your way to these choices are very sound. Whether you go for a 3 or 4-way, you should consider the advantages of the system. With a 10" sub, you may not need a full four-way system. It could take enough strain off the woofer that it plays much more cleanly at high volumes. That's really up to the room, bigger needs more bass. A ~1" tweeter, 4" mid, and an 8-12" woofer is a classic combination. Throwing a midwoofer in there is going to allow much higher volumes from each driver before they start having problems. The implementation is going to be the deciding factor. Box, bracing, crossover, and baffle design is going to be the next most important part of the design.
 
#16
D1sco said:
Just the opposite, actually. Some woofers, when expected to play low, don't play midbass or mid particularly well at the same time. The superimposed signal is smeared by gross changes in the low range. Adding a sub can greatly ease this burden from the woofer that is also playing higher, in the midbass or even up to the midrange. If you design a competent two-way, it will be better with a sub. If you build a competent three-way, it will be better with a sub. Frankly, if you build a really good four-way, it may still benefit from a separate subwoofer. Separating it from the "mains" and changing it's position can help with your room's cancellation or rattling gains.

IMD, Inter-Modal Distortion, is a measure of this and is slowly becoming more common in measurements. There are a couple of ways to reduce IMD, sometimes the cheapest is the above method-- you don't ask a tweeter to play bass, A 10" can't necessarily play low and high in the same way a 7.5" or 4" can't. They're all compromises. Some of the most expensive drivers can't help you here, which is why multi-way speakers even exist. It's cheaper to throw more drivers and crossovers at the problem than to design the newest, hottest purifi woofer.

What I'm saying is, the principals you've abided by on your way to these choices are very sound. Whether you go for a 3 or 4-way, you should consider the advantages of the system. With a 10" sub, you may not need a full four-way system. It could take enough strain off the woofer that it plays much more cleanly at high volumes. That's really up to the room, bigger needs more bass. A ~1" tweeter, 4" mid, and an 8-12" woofer is a classic combination. Throwing a midwoofer in there is going to allow much higher volumes from each driver before they start having problems. The implementation is going to be the deciding factor. Box, bracing, crossover, and baffle design is going to be the next most important part of the design.
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Ok, thanks for the explanation. I made a test enclosure and the baffle allowed for me to just add the 4" to the 6" mid and so now I am testing the 4 way and wow! It filled in every gap, I can see how people can think that a 1" and 6" sounds good, and it does. But with the drivers I had I can see what you are talking about. The 6" can't go up that high and play 80 hz. Its a 4 way for this build.

I did hear the B&W 804d4 which is a 2 way 1" and 6" ported that sounded amazing as well. But at 8500 its a bit much! The diamond tweeter is likely replaced by this 1" and 4"! So like you said cheaper to add more drivers.

What do you think about this... in this configuration I am testing, it was super easy to just series the 4 and the 6" together and its really great! They do occupy the same frequency range for the most part. I just wonder if there are some hidden IMD (hey look at me) in there somewhere, so its likely a better method to seperate them, but the crossover is 125 and I think the 4" can play near there just not loudly, more likely the 6" is killing some 2khz with distortion. Anyway it saves some amp channels and crossovers! I'll keep playing and testing but so far its a good solution, and a very lazy one.
 
#17
It's not unheard of. Normally there's a series inductor between the two to give it a low, first order roll-off between the two. The issue there is Directivity and cancellation. And oof. That's a whole other can-o-worms. I'd probably still recommend crossing somewhere between 500-1khz. That way they don't fight each other. You can always use lower order crossovers to let both woofers do more work. After a while, the "more is more" wears off for me in my projects and I start preferring high order and close crossover arrangements. Recently went through this with my sub and all the tactile response it gives.
 
#18
D1sco said:
It's not unheard of. Normally there's a series inductor between the two to give it a low, first order roll-off between the two. The issue there is Directivity and cancellation. And oof. That's a whole other can-o-worms. I'd probably still recommend crossing somewhere between 500-1khz. That way they don't fight each other. You can always use lower order crossovers to let both woofers do more work. After a while, the "more is more" wears off for me in my projects and I start preferring high order and close crossover arrangements. Recently went through this with my sub and all the tactile response it gives.
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Fair points, I think there is some cancelation going on. Lots of ups and downs in the frequency response graphs. I'll check out the first order filters, maybe that'll do the trick.
 
#20

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