EV SP12B Open Baffle

Badwater · « **on:** 9 Mar 2008, 01:49 am »

First time posting here.

I have a pair of EV 12" SP12B and T35 tweeters that I bought in 1975. I haven't used them for the past several years because of the size of the cabinets. I got rid of the cabinets after we moved because I had know where to put them. They were huge.

I pulled the drivers out today and mounted them on simple OB. I used what I had on hand so it's nothing special. They sound wonderful and are easily a match for my Fostex FE166-ESR BLHs.

The SP12B is running full range. The T35 is crossed using a 1.5 uf cap and L-PAD.

Anglo · « **Reply #1 on:** 11 Mar 2008, 01:28 am »

Hi

I can't see the baffles. I have as surrounds, 2 sets of SP12C's. They have 4 foot baffles that are plotted and sound pretty decent for surrounds. I have been thinking of adding a fountek ribbon tweeter to match my fronts which are EV SP15A's/Altec 515B for bass and a fountek pro5i ribbon tweeter.

Tell me, do you notice a difference in timber from one driver to another?

Also, your cap. Try Mundorf and cut at lower, like let's say 2.7 mfd or 3.0mfd. You'll be surprised. Also, the tweeter seems to sing more being beside the EV as opposed to on top. Anyways, love to hear more EV trial and errors!

Thanks again!

mor2bz · « **Reply #2 on:** 11 Mar 2008, 01:36 am »

Badwater, are the drivers 8 or 16 ohm? what do you drive them with? thanks

sundbyd@comcast.net

Badwater · « **Reply #3 on:** 11 Mar 2008, 10:26 pm »

I tried to post a picture, but don't seem to able to get it right. I will try again.

I don't notice any difference between the drivers. I will give some thought to cutting the tweeter in lower. Do you roll off the SP12B?

The drivers are 8 olm.

With respect to the amps I am using a Curcio Premium modified Dynaco PAS and ST70. Check out

http://www.curcioaudio.com

Anglo · « **Reply #4 on:** 11 Mar 2008, 11:49 pm »

Yes I just roll them off. They are surrounds. Like I said I may or may not add fountek tweeters to them.

Badwater · « **Reply #5 on:** 12 Mar 2008, 01:23 am »

Link to pictures on Webshots:

http://community.webshots.com/album/562755820iCRMRC

Anglo · « **Reply #6 on:** 12 Mar 2008, 02:07 pm »

Badwater

I looked at the pics. I like `em! They look identical to my SP12C's; actually I wonder what the difference is bewteen the C's and the A's. Anyways about the baffles, to me, the EV's are way too low and the tweeter is way to high. Coherently that must be a nightmare. As far as lobing goes, I am not sure where it hits at that height...I am sure others will chime in.

You'd want the EV to be about 91cm from the floor since it is a wideband driver and not a woofer.

Badwater · « **Reply #7 on:** 13 Mar 2008, 12:05 am »

Interesting. I modeled the baffles using Martin King's MathCad worksheet for a single drive OB. This modeling indicates that using a 20" Wide x 36" high baffle F3 is about 60 Hz and F10 is 40 Hz. I also modeled a 48" W X 48" baffle with Sp12B mounted 38"(91 cm) above the floor. For these conditions the F3 is about 55 Hz with an F10 of about 40 Hz. The major difference between the narrow baffle that I am using and the 48" baffle, based on the modeling, is a 5 db increase in system efficiency. The 20" baffle is 90 db and the 48" baffle is 95 db.

With respect the imaging they do a very very good job; everything is where they should be and the sound stage doesn't wander around. It's almost spooky how good they image. In my opinion, they do a much better job than my backloaded horns in this area. I don't detect any problems with coherency, but then again I probably have cloth ears. For grins, I flipped the baffles over putting the tweeter on the bottom and the SP12B on the top. It sounded about the same except that the highs were obviously compromised since the tweeter was on the floor.

How are you handling the low end on your system? I am using a single DIY vented sub using one 10" Seas L26. The sub seems integrate reasonably well, although at times you can tell its definite there.

Bill

Anglo · « **Reply #8 on:** 13 Mar 2008, 08:09 pm »

...I`d love for you to explain the 5 db more efficient thingy.

I run everything in OB. I never found a sub ina box with the speed and airyness of the open mids and highs. Hence I went with an Altec515B for the first few octaves. I get an FS measured in the room of 25hz, flat. Not -3db... I power the bass with a Bryston 8B. The EVs are on 845 monoblocks 30 watts each and the tweeters are on a DIY Gainclone at 25 watts per channel.

Badwater · « **Reply #9 on:** 14 Mar 2008, 01:08 pm »

Anglo,

The larger baffle 48" wide versus 20" wide increases the overall system efficiency. I don't fully understand why. Check out Martin King's white papers on the OB design at :

http://www.quarter-wave.com/OBs/OB_Theory.html

My room is too small for such a large system as you describe. I will have to more or less stay with what I have. Must also keep the wife happy too.

Bill

tanchiro58 · « **Reply #10 on:** 14 Mar 2008, 04:09 pm »

Bill,

Do you have any pictures of your EV open baffle speakers? What is the frame's design do you use? Reason for questions is because i have a plan to build a pair of OB too and have two pair of Stephen Trusonic Full range 12 inches lying around. I do not use tweeters or any super tweeters but a pair of Alnico magner horns. Thanks for your infos.

Best regards,
Tan

Badwater · « **Reply #11 on:** 14 Mar 2008, 06:54 pm »

I am in the experimental phase right now. I am exploring a bunch of ideas. My baffles they are made out of cheap plywood that I had around. I cut the holes mounted the drivers and fired them up. See one of my posts above for a link to webshots, which has a couple of pics of what I am currently doing.

Don't be shy oabout experimenting. Use cheap wood to see where it takes you. You might be surprised with what you find. Martin Kings site is a great resource of info.

Bill

tanchiro58 · « **Reply #12 on:** 14 Mar 2008, 07:55 pm »

Quote from: Badwater on 14 Mar 2008, 06:54 pm

I am in the experimental phase right now. I am exploring a bunch of ideas. My baffles they are made out of cheap plywood that I had around. I cut the holes mounted the drivers and fired them up. See one of my posts above for a link to webshots, which has a couple of pics of what I am currently doing.

Don't be shy oabout experimenting. Use cheap wood to see where it takes you. You might be surprised with what you find. Martin Kings site is a great resource of info.

Bill

Bill,

Thanks for the tips.

Do your EV open baffle have enough bass in your room (dimensions?)? I know EV anilco woofers have a tremendous bass but in this case do they have less bass compared to conventional speakers (in boxes).

Tan

Badwater · « **Reply #13 on:** 14 Mar 2008, 08:33 pm »

Bass isn't too bad. Martin's MathCad worksheets predict an F3 of about 60Hz, which seems about right. I am using a sub to cover low end beyond what the EVs can do. I am currently exploring ideas on how to add a 15" to each baffle to cover the low end and ditch the sub.

Bill

Anglo · « **Reply #14 on:** 14 Mar 2008, 08:37 pm »

..and if you do put the 15" in the baffle, you won't believe the difference in the articulation of the bass. It is quite fascinating.

smbrown · « **Reply #15 on:** 20 Mar 2008, 07:41 pm »

Great topic! I used EV Sp12B on OB with a 15" Dayton Audio IB for bass also on the same baffle. To power the 15's, I use a first order low pass from the SP12B that is set to about 50hz or so (made it adjustable), this goes to the input of a pro SS amp (200wpc) then to the 15's. So what happens is that roll off of the baffle, together with the natural response curve of the IB speakers gives me flat to about 30hz or so. Sounds great, integrates very well.

Badwater · « **Reply #16 on:** 2 Apr 2008, 10:27 pm »

After much contemplation and analysis I have finally decided what I want to do. I plan on using Eminence Alpha 15A on the bottom with the EV SP12B and T35 on top next to each other. This will be a passive solution similar to Martin King's passive open baffle project. To match the EV with Eminence I will use series resistance. Based upon sims this should be about 5 ohms. All the needed parts arrived today. I should be able to get it up and running on a temporary baffle this weekend. It should be loads of fun.

Bill

Badwater · « **Reply #17 on:** 6 Apr 2008, 12:10 am »

Trial baffles are finished. See link to photo on Webshots. The EV is crossed over per MJK at 200 hz. The T35 is crossed using a single 2.7 uf cap. The EVs are much more efficient thaan the Eminence Alpha 15A so added 5 ohm series resistance to pad it down.

They sound very good, bass is tight, although adding a sub is really fills out the bottom end. Sound stage is massive and very stable. They are very close to the my Fostex FE166 ESR horns....basically a toss up.

http://good-times.webshots.com/photo/2698954580053660797rcEZgh

Anglo · « **Reply #18 on:** 8 Apr 2008, 01:23 am »

Very nice Badwater!

Tell me, when you toe in the speakers "more" do you notice how the rythm and pace slow down?

Badwater · « **Reply #19 on:** 9 Apr 2008, 12:21 am »

Even though I added 5 ohm of series resistance to the EV's it was still too hot. I added an L-Pad to both the SP12B and the T35. Padding them down allowed to bass to emerge with a resultant very balance sound. I turned off the sub as it is no longer needed....

With respect to your question, I have the baffles toed in so that the listening position is slightly off axis to the outside. The sound is coherent and very pleasant to listen to.....everything is where it should be. At your suggestion I toed them in such that axis would intercept in front of the listening position. The sound stage compressed and seemed to loose coherency. The wide open sound was missing. To my ear the toed in position appeared to loose pace and rhythm, assuming I am interpreting what you are asking correctly. The toed out position is where I like them best.

Time to build some good looking and substantial baffles; these babies are keepers.

B