Starting my new custom SDA1C's

ben62670

OK enough resting. Its time to build some SDA 1C's. I already have the parts. Time to get kick-en on the project. I am building these for a buddy of mine. I have known him ever since I can remember. I know he will take care of them. When I am gone(Doctors don't really know whats going on when they estimate). It'll give him something to cherish. His Dad left him an old tube amp, and some real old pioneers. Well his Sis got his Pioneers, but he still has the tube amp. Stuff like that has sentimental value to him.
Off to work
Ben

xsmi

ben62670 wrote: »

OK enough resting. Its time to build some SDA 1C's. I already have the parts. Time to get kick-en on the project. I am building these for a buddy of mine. I have known him ever since I can remember. I know he will take care of them. When I am gone(Doctors don't really know whats going on when they estimate). It'll give him something to cherish. His Dad left him an old tube amp, and some real old pioneers. Well his Sis got his Pioneers, but he still has the tube amp. Stuff like that has sentimental value to him.
Off to work
Ben

Ben,

Will Polk allow us to build speakers that match the specs of their own models?

ben62670

xsmi wrote: »

Ben,

Will Polk allow us to build speakers that match the specs of their own models?

Yes. They will even help you sellect the drivers from them. You can not however build them for sale. If you are thinking of building some, and need any help building them let me know. Just PM me.

Thanks Ben

ben62670

Well I have been working on the XO's today, and have them finished. I converted some SDA2a's XO's to this application. I basically ripped everything off the Dim board, and started from scratch. On the stereo board all I modified the inductor to 2.5mh from 2.75. The 2's used blade/blade so the were a lot of spare parts left over from the conversion to pin/Blade:D

engtaz

Hey have you been sleeping too much? LOL What's your latest progress report and pics.

ben62670

I am going to finish them up north. The price to ship the boxes is way more than it is to build them here, and send the there.

xsmi

Ben check your PMs Bro...

ben62670

I'm still up north, and I won't be back till Wednessday. I have pics, but I can't get them off my camera.

xsmi

Gotcha,

I will be looking forward to hearing from you. Tuesday is the only day I will have the truck should I by 1/2" or 3/4" MDF. I plan to buy 4 sheets. If I don't need all 4 I will return some.

ben62670

Cabs

avguytx

Great looking cabinet, ben. How are you going to cover them? Wood veneer on the sides? Solid pieces on the tops and bottoms?

I love woodworking. I build lots of shelves, dining tables, coffee tables, cabinets, etc for friends and family. I have to spread them out though as it's hard to keep track of and do my work to pay the bills!

xsmi

Ben,

I know they are custom but the 1C usually has two tweets right? What purpose does the second tweeter serve?

avguytx

Hmmm...that's true. Ben, where's that 2nd tweeter? :rolleyes:

ben62670

I am using a Morel tweeter with my custom SDA setups. The imaging, and detail is superior to RDO's. They handle more power than the Polk's so you only need one. With only one the mids can be placed higher, and you don't have to worry about any phase issues associated with multiple domes. Less complicated XO, and my buddy has a kid with curious fingers! He will be finishing the cabs himself with some sort of veneer. They are setup with pin/blade, and the resistor in the signal path for the tweeter has been reduced to 2 ohms from 2.7 to yield the correct output with the Morel's. The Morels impedance curve is nearly identical with the Polk's so it is a great option for the DIY crowd.

xsmi

In the custom 1.2tl's that I would like to do, would you recommend 2 or four of the Morels?

ben62670

xsmi wrote: »

In the custom 1.2tl's that I would like to do, would you recommend 2 or four of the Morels?

I can not comment on that yet. I am implementing the XO for that situation as of now. Just got the parts today. I will know in about 2 weeks. One thing I can say is that I have done it with ONE Morel. I didn't feel like posting this because of all the nay sayers, but one morel sounded better than the Polk setup. The 4 tweeter design has so many components in it, and in the XO on the highs only there is an added 56.5 ohms of resistance (as in resistors, as in wasted currant) directly in the signal path. With one morel using the 12 uf cap, .4 mh inductor, and 2.7 ohm "roll off" resistor works excellent with one tweeter. It does not look as impressive as 4 tweeters, but having a single high frequency driver cures a bunch of complicated phase issues associated with multiple tweeters. I have driven that setup hard with 400 watts of Adcom power. I have reached 120 db clean. That is an insane level for home speakers. The money you can save by using ONE high quality tweeter, and related components presents an almost undebatable argument for using a single tweeter design. So if anyone who hasn't heard a single HQ tweeter in such an array wants to comment that it would not suffice please stick your head in your anal cavity, and ****! Others please post concerns or constructive comments.

Thanks Ben:D

Edit: BTW I wish you were closer. The HP sound stage is so incredible with one tweeter it would leave you shaking your head in disbelief.

altecman

ben62670,
How did you go with this mod?, what was the model Morel tweeter used. Its funny how you had the same idea as what I did with my SDA-1A's e.g. SDA-1A.1TL mod. Whilst I am still waiting for the RDO194's I was thinking of dropping in a pair of some older Vifa H25TG-35 horn tweeters, I have attached the PDF, what do you think? I was only thinking of trying these, as being horns should disperse the treble a lot better than the generic dome type tweeters. Good or bad idea?

Systems

I see at least 2 problems ,firsly the horn loading gives that Vifa several db of extra sensitivity so it will need some attenuation,as well its bottom end begins to roll off below 2.5k.Im not sure what the xover point is in your Polks but I suspect its closer to 2 k?If that the case then the response in the crossover region will not be ideal.

altecman

GV#27,
The SDA-1A's are 91dB, so I will have to drop about 4 dB. The xover point is 2.5K.

Systems

altecman wrote: »

GV#27,
The SDA-1A's are 91dB, so I will have to drop about 4 dB.

Yeah you will need to pad it down some, preferably using a pair of resistors in an Lpad (voltage divider). Just using a simple series resistor will change the load the crossover seas so it will shift the xover frequency somewhat.

The xover point is 2.5K.

Techno babble alert.:D With out the crossover the response of the stock tweeter likely extends down into the 1.2-1.5k region.The fact that the Vifa starts to rolls off at the 2.5k crossover point will mean that when the drivers response and the xover are combined the slope will be approx 12 db steeper than with the stock tweet.This would mean in all probaility that the Vifa would be out of phase.This is fixed by reversing the neg and pos leads on the tweet.