Time to try a 3-way.

[DrDyna]

Ok, so lately I've been mulling over the idea of making a floor standing 3 way speaker. I've played with too many 2 ways and I'm getting bored. Time to try something bigger!

I've still got a couple of Peerless 831759's available, and a couple of Vifa SC14SG-49 midbass and a couple of Vifa AC25TG05-04 soft domes.

I've considered crossover points perhaps 700/4000.

I'd like to make a fairly large cabinet with enough space (guessing 150L perhaps?) to use a 3"x 11" or so port for the peerless 10 to get it down somewhere in the neighborhood of 25-28 cycles.

Does anyone have any input on those crossover frequencies? I haven't tried to set out designing one yet (I'm usually pretty bad at it and would end up having to ask for help anyway!) but I'd really like to try my hand at a large, classic speaker, you know, the kind with terrible WAF.

Any comments, suggestions or fun-pokes are welcome!

[Loren42]

Passive Crossover Network Design

[DrDyna]

Originally Posted by Loren42

Passive Crossover Network Design

Thank you Loren

I do have several such sites bookmarked that I use from time to time. They are a good starting point, but usually the finished crossover design ends up being quite a bit different

[Loren42]

Originally Posted by DrDyna

Thank you Loren

I do have several such sites bookmarked that I use from time to time. They are a good starting point, but usually the finished crossover design ends up being quite a bit different

Here are my observations/questions:

1. What is your selection criteria for 700 and 4,000 Hz as your crossover and how did you arrive at those numbers? Can yo

2. Why the shelf port versus a round port?

3. Why the large port area?

4. Have you calculated the shelf port length?

5. Why did you select 5.3 cubic feet for the box size? At 100 Watts you reach xmax at 45 Hz.

[a.wayne]

Good choice , a good 3way can be very rewarding ...

[DrDyna]

Originally Posted by Loren42

Here are my observations/questions:

1. What is your selection criteria for 700 and 4,000 Hz as your crossover and how did you arrive at those numbers? Can yo

2. Why the shelf port versus a round port?

3. Why the large port area?

4. Have you calculated the shelf port length?

5. Why did you select 5.3 cubic feet for the box size? At 100 Watts you reach xmax at 45 Hz.

1.) Just from observation on frequency responses and what looks like good places to cross the drivers over before they start to get messy.

2+3+4.) It's a round port of PVC pipe, 3" in diameter and 11" long. I'm using it as a starting point because it's the same size and shape of a port used in a small cube subwoofer that was designed with this woofer that was tuned to 26 cycles. (well small, it's about 26"...let me go measure it....more like 22" square.)

5.) I'm not entirely sure what the size is going to end up being, I just had the looks of the box in my head and threw out that number, chances are it's going to be pretty different.

edit: 6.) You'll have to excuse my napkin scribblings, quite often I'll have a few beers and come up with something that I have to share, lol.

[Loren42]

Originally Posted by DrDyna

1.) Just from observation on frequency responses and what looks like good places to cross the drivers over before they start to get messy.

2+3+4.) It's a round port of PVC pipe, 3" in diameter and 11" long. I'm using it as a starting point because it's the same size and shape of a port used in a small cube subwoofer that was designed with this woofer that was tuned to 26 cycles. (well small, it's about 26" square.

5.) I'm not entirely sure what the size is going to end up being, I just had the looks of the box in my head and threw out that number, chances are it's going to be pretty different.

I don't have your specific woofer on file, but I bet if I ran it in LEAP I would see some pipe organ effect on the port. It may not be big, but having such a high crossover for the woofer invites the possibility of port noises and issues with the woofer cone break up (wherever that really is for that driver).

What works well for a sub does not necessarily lend itself to a multiway speaker. Generally the sub uses larger port area to reduce port noise, but cut the woofer off early before pipe organ effects take place (i.e., below 200 Hz). For a multiway you have to balance port noise with the pipe organ effect (if present), so the design is a compromise either way.

One of the virtues of a 3-way is getting a lower crossover for the woofer than you would for a 2-way and letting a mid carry some of that load. 700 Hz may not work well in this case, but without going through a lot of testing and modeling I just don't know.

All of these things are just things you need to consider and are not necessarily gospel.

[DrDyna]

Originally Posted by Loren42

Generally the sub uses larger port area to reduce port noise, but cut the woofer off early before pipe organ effects take place (i.e., below 200 Hz). For a multiway you have to balance port noise with the pipe organ effect (if present), so the design is a compromise either way.

Right. I had not really considered this. Perhaps it would be better off sealed, or ported if I drop the crossover frequency down a bit.

Sealed might be the way to go, part of the reason I was looking to build a 3 way like this was to have great power handling by letting the large driver cover as much of the band as it could.

[a.wayne]

Depends on driver QTS value ....

[DrDyna]

Originally Posted by a.wayne

Depends on driver QTS value ....

Our qts, she be .2713.