Home theater rebuild phase 1: Center channel

[BoomieMCT]

Redid this test with two changes. One this is now a MTMWW and an active x-over (not what I'm going to end up using). Two I used only Jentzen air core inductors in 1.5mH increments. So here is 0, 1.5, 3 and 4.5 mH. I think this is looking pretty good!

Doing listening tests with this new setup sounds great. I think the Neo3PDR and the Dayton RS125S-8's are a great match. The only problem now is the level match very well without any padding. Sadly I need to pad the tweet a bit because I don't want a 4 ohm load. For my minimum 6 ohm load I'll need to add 2 ohm in series which will cut the tweeter 3dB.

Maybe I'll contemplate another tweeter . . . but I don't want to!

[BoomieMCT]

I was thinking that my level issue might be partly related to the fact I was using an active x-over. I thought that the Neo3PDR's efficiency advantage over what was essentially two RS125S-8's in series should allow me to use some padding on it. So I whipped up some passive x-overs with parts I had lying around. I did not have exactly the values I needed but this is enough to put the Neo3PDR back on the menu. Below is a (very imperfect) second order electrical x-over with 2 ohms of padding on the tweeter. Looks like the levels are about right!

[Anthony]

Um, was there supposed to be an image?

[BoomieMCT]

Anthony wrote:

Um, was there supposed to be an image?

I can see one. Try again!

[Anthony]

Now it's there.

The rise at the crossover point would make me think you need to swap polarity. Worth a quick try and remeasure.

[BoomieMCT]

Anthony wrote:

Now it's there.

The rise at the crossover point would make me think you need to swap polarity. Worth a quick try and remeasure.

I did and it didn't look much better. With the baffle effects this ends up being (roughly) a 3rd order LR so polarity *shouldn't* matter. I think the main reason that hump is there is I didn't have the exact values I needed and the tweeter is crossing over 100-200 Hz low. Also the Neo3PDR has a little bit of a bump right around the x-over frequency. I may need to move the tweeter's x-over above 2.2kHz or use a steeper slope. Given the fragilitiy of the Neo3PDR both would be fine by me.

I'm going to play with it when I have more time.

[BoomieMCT]

Got an enclosure to test now. Sadly I don't have the proper port for it and the cardboard one I made is too wide so the tuning is too high. Still, here is a quick test run. It sounds great. I switched to better x-over parts and now the tweeter is too hot. No biggie - I can pad it more and redo the x-over.

Subjective impressions: Dispersion is great as is articulation. Although only medium efficiency I can run these pretty loud without hearing distortion creep in. I think these will fit the bill.

Next step is to play with the tweeter level and .5 woofer inductor to find what works best.

[BoomieMCT]

Got the last of my parts in and put it all together. I haven't done a carefully set up test yet but the three quickies I did all were +- 3dB from 70Hz to 20kHz. It sounds real clear and quick but, I'll be honest - I have trouble doing real listening tests without having speakers be in pairs. Well, that's my next project anyway.

In case anyone is interested the crossover is real simple. The tweeter is a second order electrical network with C=5.1 uF and L=1.0mH. I put a 4 ohm resistor in series with the tweeter. The woofers are a second order electrical network with L=1.3mH, C=4.7uF and the inductor for the .5 woofers is 1.0mH.

[mayhem13]

Looks really nice Boomie. Why the sloped baffles?

[Jason Schultz]

Hey Boomie
how did you deal with the rise in the response of the RS 125's at 2000 Hz or did you get away with the xo doing the work. PS they look great and i like the waterfall plot of those tweeters. should sound great.

[BoomieMCT]

mayhem13 wrote:

Looks really nice Boomie. Why the sloped baffles?

Since this is a center channel it has to sit on the floor. I sloped the baffle so the tweeter would be on-axis with my ears where my couch is. The slope is less then it may appear - ony 11 degrees. The L and R mains will be similar except no slope on the baffle.

[BoomieMCT]

Jason Schultz wrote:

Hey Boomie
how did you deal with the rise in the response of the RS 125's at 2000 Hz or did you get away with the xo doing the work. PS they look great and i like the waterfall plot of those tweeters. should sound great.

I dealt with that and the hump near that same spot in the crossover. When all things are combined these have an x-over of about 2,200Hz.

And, yes, I do like these tweeters a lot!