OK last time I am changing the schedule. I mean it!

ben62670

Well here are a couple pics. There was some wondering about what to watch here. I do have Dish Network;)


Also the food situation was a little bleak(beer is food right?). The coons got into the frog pond. No frog legs this year, but next we are either eating frog legs, or coon.

ben62670

Well I did some playing with the SDA's, and I explained that the Dims were at 4ohms, and the stereos were at 4 ohms. With the newer XO styple(P/B) the outers needed to be 4ohms with the inners at 8 ohms. I was thinking of adding another driver to make the stereos 8 ohms, and the dims 4 ohms. I sent an email to the man the other day, and he sent me a reply pretty quick.

Ben -

When you get a moment please sketch out a diagram of the crossover and SDA circuits you are using. I might have some ideas that would help.

The reason you're not getting a really wide SDA soundstage is the impedance of the SDA drivers is the same as the Stereo drivers. Because the two SDA driver arrays are effectively wired in series the SDA signal is seeing 8 ohms, not 4 ohms. This means that the SDA signal is about half as loud as it should be. A nice experiment would be to disconnect 4 of the stereo drivers on each side leaving just the four in the middle wired series-parallel to give you 8 ohms. This will drop the stereo signal level to match the SDA signal and will also reduce beaming.

Give it a try and let me know.

Good luck!

-msp

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Original Message

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From: ben williams [mailto:ben62670@yahoo.com]
Sent: Thursday, August 14, 2008 10:32 PM
To: Polk, Matthew
Subject: RE: DIY SDA builder

Well I have saved your email for quit some time now. I have been playing with them, and making lots of changes. I now have them actively crossed over at 2250hz. The top end consist of either one, or two tweeters running. I am using Morel's for the tweeters. When using two tweeters I just run one out of phase. I know it sounds overly simple, but it seems to work very well in my environment. I never did implement a 300hz XO on the bottom, and top sets of MW's. Where I am now like you said the mids are beaming pretty bad. I get a big bump in the 300 region, and I was thinking of a 6db XO point at 250(inductor). This would throw off phase a bit, but might actually play nicely with the PR's. Some input would be appreciated. I hope to see you at PF-08. Here is a recent pic of the system as it sits now.
http://www.polkaudio.com/forums/showpost.php?p=904231&postcount=65
The little wood box in the center contains two 15mh inductors for the SDA effect. I know this isn't the best setup for my array seeing that both arrays are running 8 8ohms drivers at 4ohms, but I just couldn't afford to get 16 4ohm MW's to get things right. It works, but the sound stage isn't as wide as I would like. Someday I will ave the coin to get it right;) Have you ever played with the idea of over sized SDA's?

Thanks
Ben

Well I never thought of running just 4 stereo drivers, and 8 dims. I'll have to get back to him(those who know... know who him is;)), and see.
Pretty excited about the new idea. I just can't pull it off with that many mids in that small of an area. We were to the point of nailing up blankets to the walls!
Ben

lightman1

Well.. here goes!! Ben's a geek!!! If I had more time to pick his brain, I'd still be there. The FrankenPolks are, as I've said before, a lobor of love (for sound). Tom and myself got the long haul award, drank all the Kool-aid and I slept in the laundry room.;) Overall It was great to meet some new Polkers and hear some tunes on an ear splitting set up. Thanks again Ben for the invite.




and my boxers are under youre pillow.:D

Ricardo

Pictures WITH the polkies or it did not happen.

zombie boy 2000

Oh... IT happened. I don't remember IT, but I have the rashes, boils and scars to prove IT.

ben62670

Hey man when you coming back? I had a little help from the SDA creator, and the SDA is in full effect!
Bring some good news:)
You still have a jug of JD here!
Ben

zombie boy 2000

This weekend is probably a bust for me... or maybe not. Either way, the next should be perfect. Are you keeping dry out there?

ben62670

Wet Wet Wet. Which is better than no rain. The frogs are doing well. There is a big one ready to eat:)

zombie boy 2000

Sounds tasty. Should go well on pizza. I'm really itching to start a new rig and I think a quick jaunt to your pad should kick me in the **** and the wallet.

ben62670

I can hook you up with a real nice Pre on the cheap. You heard the dynamics, bass slam, and no noise even when we turned it all the way up. You should hear it with the LSI's I just modded. I am very excited. The rumble filter is built for the phono section, and ready to install:)
Ben

ben62670

ZB bring me some good news!