This is another design I came up with in the mid 90s that I never got to build. The mid-woofers are still Peerless but they are a bit different than the originals. They have nearly identical T/S parameters but they have truncated frames.
The original tweeters were going to be the horn loaded Morels which are still available but, with the truncated frames, I thought the tweeters should have them too.
Enter the RST28F tweeters.
Whipped this test box up in a few hours. Came out ok. Might be able save it as a final box. It needs work. Just needed it good enough to take measurements. Had some left over total trash plywood to build it with.
This one should be a low cost tower for HT or even a party speaker. They should do 122 db a pair at 3 ft. Will only get to about 50 hz for F3 in 2 cubic ft. I would use them with subs. Some people might like them as is.
Woofers are P830874 Peerless drivers. Will start crossover work Wed. after some measurements for XSIM.
That tweeter sounds better in a SEOS-8 waveguide, IMO - might work well with those drivers and give you a better XO slope/knee . . . Love the project, Erik!
There was another variant called Prisstina, which used the RS52A version 1, and a little Dayton ND20. Yet, another had 5 woofers used, one as mid and quad woofers.
I’m using those woofers individually with single 2" unflared ports. I’ve not heard it chuff with any of the excursion tests I’ve done. I’d bet a double flared 4" precision port would be fine. Just take note of their length estimates for the flared sections. Looks like the 4" flare is 3" long but they suggest using 2.5" as it’s length for calculations. And if need be you can join the flares together with the connecting ring they sell for down to 5" length.
My powered 12” subs use a 3” flared port, and only chuff at levels well above my normal listening levels. They may start compressing before chuffing occurs but if so I do not find it audible.
Using the optimised port allows you to use a smaller port for the same output capabilities. Great for low turning in a small box, or in this case maybe just one in the place of two.
That port designer said I need two 5” D X 14” ports.
I am just going to try a single 4” and see what I get. I am using a 3” with a 12” sub in my living room and don’t hear any noise at 110 db from the port. Winisd says it is hitting 227 air velocity!
Ok, so I put a crossover together today. Didn’t even use XSIM. Just through some parts at it and it seems to be very good. Drivers are easy to work with. Looks like it is 94 db at 2.83 volts. With about 5 volts going to it, it was doing about 100 db. Distortion at 2.83 volts was mostly down in the 0.2 percent range and 2 percent at 20 hz!
These things are super clean and they punch me in the chest and shake the concrete floor.
Just for testing I used two 2.12” diameter ports. WinISD said to use 1.75” length for 53 hz tuning. When measured, it was 43 hz. In room response gets to low 30s. Did not expect that at all. I heard no chuffing at all and the sound coming out of the ports were very musical. No one note boom.
Impedance gets down to 2.6 ohms at the lowest but it is at 0 degrees phase. It is a 4 ohm speaker. I do have a large peak at 1100 hz. Don’t know why. Will have to investigate that.
tweeter sounds better in a SEOS-8 waveguide, IMO - might work well with those drivers and give you a better XO slope/knee . . . Love the project, Erik!
