I'm running this speaker system http://www.diyaudio.com/forums/showthread.php?s=&threadid=69906&highlight= with a DEQX for the top three drivers. I'm planning on an active line level crossover between the 15" OB driver and the 12" PR sub driver.
Now, normally one would take into account the roll off of the woofer when designing a crossover to the sub. However in this case, equalization will be done by the DEQX on the combined pair. All I need is for a smooth transition between the drivers. Also, the OB driver and PR sub driver have a range of several octaves where they are both dropping about first order in parallel and the same output (they have the same motor). If I put my crossover in this range, I'm thinking I can just do a symetrical crossover and not worry about the roll off, or in other words, treat them as if they had a flat overlapping range. I'm thinking 4th order LR. Comments?
Sheldon
Now, normally one would take into account the roll off of the woofer when designing a crossover to the sub. However in this case, equalization will be done by the DEQX on the combined pair. All I need is for a smooth transition between the drivers. Also, the OB driver and PR sub driver have a range of several octaves where they are both dropping about first order in parallel and the same output (they have the same motor). If I put my crossover in this range, I'm thinking I can just do a symetrical crossover and not worry about the roll off, or in other words, treat them as if they had a flat overlapping range. I'm thinking 4th order LR. Comments?
Sheldon
Thanks,
I'll check it out. I had thought about the transient response a little, which is one reason I went with the DEQX. It seems evident that transient response would be audible at higher frequencies where the transients are key to realistic sound. Is transient response also readily audible at the low frequencies?
Sheldon
I'll check it out. I had thought about the transient response a little, which is one reason I went with the DEQX. It seems evident that transient response would be audible at higher frequencies where the transients are key to realistic sound. Is transient response also readily audible at the low frequencies?
Sheldon
Ah, ok let me rephrase the question. If I've badly screwed up the sub design I'll hear it, that makes sense. So I should ask if the difference between a "standard" crossover, ala LR, and a transient perfect crossover be easily audible at frequencies below about 80-100 Hz? It seems no harder to implement the transient perfect crossover, but I'm limited to 2nd order for the common published ones. So would it's advantages likely outweigh the advantages of steeper slopes? Of course, I could try both, but at some point I want to put down the soldering iron and listen.
Sheldon
Sheldon
I use the example of the badly tuned vented box as the result does resemble the result of poor crossover types. In reality, there are more often problems in even getting the crossovers there. Dealing with low crossovers is one reason why I now go two way (thought that I never would once). Some people say the ear is less sensitive to problems in the lower frequencies. Not mine. I really dislike a lack of continuity in the bass/mid region.
Ok Ind,m,
I took your advice, thanks. I went to the FRD and played with an 80 Hz crossover until I got reasonable parts values. Here's what I came up with. The first two op-amps are the 80Hz boost and the other two are labled for high pass and low pass. I built it using some TL082, as I had some, and with that frequency, I figured they would be ok. I used 15 volt regs (47uF on the input, 0.1 on the output), powered off the amp rails. It seems to work just fine and sounds good with the limited testing I've done. I do get some noise on power down after about 5 seconds, when the main amp caps run out of juice. It's not a dealbreaker, but I would like to eliminate it. Different op amps? I'm using dual 8 pin versions with sockets, so I can easily change.
I took your advice, thanks. I went to the FRD and played with an 80 Hz crossover until I got reasonable parts values. Here's what I came up with. The first two op-amps are the 80Hz boost and the other two are labled for high pass and low pass. I built it using some TL082, as I had some, and with that frequency, I figured they would be ok. I used 15 volt regs (47uF on the input, 0.1 on the output), powered off the amp rails. It seems to work just fine and sounds good with the limited testing I've done. I do get some noise on power down after about 5 seconds, when the main amp caps run out of juice. It's not a dealbreaker, but I would like to eliminate it. Different op amps? I'm using dual 8 pin versions with sockets, so I can easily change.
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AndrewT said:
They are different. The HP is 50 and the LP is at 128. The boost steepens the filters and gives a bump at 80, when is then eq'd out with no phase change, as the combined filters are linear phase. I haven't noticed any noise issues, but the top driver only goes up to 350 where it's crossed over with a 120dB digital filter with a DEQX.
Sheldon
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