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Old 10th October 2012, 01:58 AM   #1
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Default The start of my small dipole hybrid

My dipole is a test to see how my 21 x 21 foot room will work with rear dipole dispersion where the speakers have to be positioned due to my 16' diag theater screen as seen here. Obviously the speakers cant block the screen so they must perform well in a similar location to where the current monitors are. They are 4 feet from the subs, 4 feet from the side walls and 6 feet from the screen. Listener(s) are 10-12 feet from the dipoles. Please keep in mind this is simply a dipole radiation sound test. The real speakers will be a line source with a BG 50 and 9 7"woofers or a 75 with 9 8"woofers.

The room here shows the 16 feet screen with sub locations in the corners. This isnt a changeable situation. Ceilings are 9.5 feet. The room opens to the rest of the house (big). Amps are Peavey CS4080HZ sub amps x 2 and lots of crown amps to run the dipoles.
Click the image to open in full size.

Im not sure if its relevant that my home gym is a room to the rear of this 21 x 21 room. This is the only picture I have of how it opens to the home theater. It shows the 7 or so feet behind the couch that can be moved back if needed. There are glass doors that can seal off this room. Anyway, this is me. Hi. My arms are covering the bullet and knife wounds from my prior police career. I'm now a math teacher with no guns. I live near Columbine High School in Colorado so I could in theory still get shot at work or at local theaters.
Click the image to open in full size.

The speakers are essentially 3 way plus a sub pair (2 ported 15" TC sounds per cab). They use a trapezoid panel that varies from 11 wide down to 16"wide. A sealed bottom chmber will house a 12". The crossover is a Behringer 2496 at about 1900hz 4th order electrical to start. Measurements will taylor that.

The tweeter is a BG Neo 3W with felt treatment pads to essentially make it a Neo#pdr which has been on backorder by Parts Express for 5 weeks so I opted for the 3W. The midbass is a Dayton 7"aluminum cone because I had them. Again these are test speakers. If the dipole nature works with my forced placement, I will go with a BG 50 or 75 line source and 9 8"drivers.

These pics are the start of the frames ( I guess they are kind of enclosures due to the bottom chamber).

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Chamfer radiused in the rear of the 1.5" thick baffle
Click the image to open in full size.

I left room for a second 7"that can be crossed slightly lower to reinforce 100 to 500. Im not sure what to expect for lo end roll off or if its needed. It needs to only play at 5 watts or so to get an idea of SQ.
Click the image to open in full size.

Here you see the bottom chamber. Rake angle/back tilt to focus the tweeter is done by adjustable spikes on the bottom front of the base. The sealed chamber is 1.55 cubes net for a sealed TC 12" for a .57 Q.
Click the image to open in full size.

Distance to the listener from the dipole is 10 feet.

Next will be grills for the front and if the test run sounds good I will fill all iregularities with bondo, seal, and sparay an automotive paint finish.

I will try to update as I go.

Suggestions, comments, concerns, and general insults appreciated.

Last edited by SpinMonster; 10th October 2012 at 03:10 AM.
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Old 10th October 2012, 02:30 AM   #2
kctess5 is offline kctess5  United States
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Quote:
general insults appreciated.
Looks terrible

No thats a joke, they look awesome. Those are quite the baffles (and screen!!!), I like the routed edges on those. I wish I had room for some big dipoles like these.

Quote:
3 way plus a sub pair (2 ported 15" TC sounds).
2 TC 12" + 2 TC 15" should be *enough*

That will be quite the setup, I'm excited to see the finished pictures and listening impressions. I have those B&G tweeters and I must say they sound pretty darn good, especially in the test dipole horns I made.

What color will they be?

May I suggest some room treatments on those walls? Just some good looking acoustic foam would do the trick. Also if the screen is mounted an inch or two away from the wall you could put some directly behind it and it wouldn't be visible, assuming it is acoustically transparent that would help. With the dipoles it should help a fair bit to reduce the rear-wave reflection. Also with all that room and subwoofing power some bass traps could do some good. I dont have any room for any of the aforementioned items in my room but I wish I did...

P.S. this should be in the multiway forum, except for the tweeters this is conventional technology. Maybe you should ask the mods to move it over for you.

Last edited by kctess5; 10th October 2012 at 02:32 AM.
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Old 10th October 2012, 02:47 AM   #3
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Originally Posted by kctess5 View Post


2 TC 12" + 2 TC 15" should be *enough*


P.S. this should be in the multiway forum, except for the tweeters this is conventional technology. Maybe you should ask the mods to move it over for you.

Its 2 15's per sub for a total of 4.

The midbass is also dipole down to around 250HZ; it isnt conventional.

As I stated, this is a test for the dipole nature in this room, not for a finished final system so feedback and observations are solely for dipole results. Im not interested in the speaker as a final product nor am I interested in its non-dipole characteristics. If the room works for early reflections with it being dipole with the forced positions, then I can continue with building the final system.

It fits this forum by it being something other than a multi-way monopole and I dont want it moved. This section is for planars and exotics; Its exotic to me....haha

Last edited by SpinMonster; 10th October 2012 at 03:00 AM.
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Old 10th October 2012, 02:58 AM   #4
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Originally Posted by kctess5 View Post

May I suggest some room treatments on those walls? With the dipoles it should help a fair bit to reduce the rear-wave reflection. Also with all that room and subwoofing power some bass traps could do some good. I dont have any room for any of the aforementioned items in my room but I wish I did....
I think rear wall treatments are needed more for those with the speakers too close to the rear wall. At 4-5 feet the rear wave actually reinforces the depth perspective. I think its reflectons that are within the first 8ms that confuses the depth image hence why some prefer the deadening of the rear wave when its less than 4 feet, IE... 3 feet. At 5-6 feet from the rear wall its pretty stunning. I also have to contend with reflections at 4 feet from the sub which is 8 feet round trip or about 8ms.

Sidewall reflections are reduced by the 3W's limited dispersion in comparison to the 3PDRW.

The screen isnt acoustically transparent so nothing can be done hence why Im testing with these cheapo speakers before dumping 2500 into 7 foot mammoth beasts that wont work.

I ran my appgee stages years ago at 5 feet with no treatment and was as happy as can be.

Last edited by SpinMonster; 10th October 2012 at 03:01 AM.
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Old 10th October 2012, 04:08 AM   #5
kctess5 is offline kctess5  United States
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OBs would still go over in multiway (Ultimate OB Gallery), planar/exotic refers to the actual drivers, not so much the cab design. But it's up to you of course, just a suggestion.

For a test speaker set these are sure pretty impressive I'd love to see the final system if this is just the "let's see if it works" version. I wish I had the budget for that sort of thing, I consider the TCs and the B&Gs to be pretty high end

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Its 2 15's per sub for a total of 4.
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Old 10th October 2012, 08:44 AM   #6
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Originally Posted by kctess5 View Post
OBs would still go over in multiway (Ultimate OB Gallery), planar/exotic refers to the actual drivers, not so much the cab design. But it's up to you of course, just a suggestion.

For a test speaker set these are sure pretty impressive I'd love to see the final system if this is just the "let's see if it works" version. I wish I had the budget for that sort of thing, I consider the TCs and the B&Gs to be pretty high end

Thanks. The compliments are appreciated.

I figured the population in this section may be more knowledgeable on the BG 50/75 and what aspects of room limitations would apply to my target.

95% of the BG 75 users use dynamic woofers/subs in conjunction so I'm not far off as not many systems in this section are pure planars. Since Im not getting much of a response, I will ask the mods to move it anyway.
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Old 10th October 2012, 03:43 PM   #7
Pano is offline Pano  United States
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Old 10th October 2012, 08:29 PM   #8
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Hey Spin, glad you started the project. Remind me, what is the crossover going to be? MinDSP? Behr 2496? I think with good, broadband absorption(like minimum of 4" of rigid fiberglass or Bonded Logic) behind the baffles, you might be OK nearer to the wall.

You can always use the Neo3/Dayton 7" in a surround build, right?

Keep those picts coming!

Greg

PS, you going to RMAF this weekend? I was hoping to make it, but some travel for work popped up this week and the next.
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Old 10th October 2012, 11:01 PM   #9
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Originally Posted by studiotech View Post
Hey Spin, glad you started the project. Remind me, what is the crossover going to be? MinDSP? Behr 2496? I think with good, broadband absorption(like minimum of 4" of rigid fiberglass or Bonded Logic) behind the baffles, you might be OK nearer to the wall.

You can always use the Neo3/Dayton 7" in a surround build, right?

Keep those picts coming!

Greg

PS, you going to RMAF this weekend? I was hoping to make it, but some travel for work popped up this week and the next.
Its using beh 2496.

I ddint think of using them in the back. That will work better than the fullranges.

Im not trying to get closer to the front wall. My issue was in that it cant block the screen for any watching seat so the sidewalls were more of a concern. The subs are right at 4 feet whch is right at the limit of an 8ms delay for reflected sound.
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Old 10th October 2012, 11:24 PM   #10
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Originally Posted by SpinMonster View Post
Its using beh 2496.

I ddint think of using them in the back. That will work better than the fullranges.

Im not trying to get closer to the front wall. My issue was in that it cant block the screen for any watching seat so the sidewalls were more of a concern. The subs are right at 4 feet whch is right at the limit of an 8ms delay for reflected sound.
OK, well treat the sidewall then...

I just moved my room around, but for many years I was stuck with my open baffles right up against the side walls(they were 7ft out from the front wall though). I always had lousy imaging and a soundstage that seemed to moved around. Once I finally treated the side walls, it was much, much improved.

Whatever you do, try to put something up that is more effective than just acoustic foam. The majority of foam that people use does not do much below 500hz. 4" of rigid fiberglass or B.L. spaced just a little bit off the wall will work well down to at least 100Hz.

Greg
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