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Discussion Starter #1
It only took about 1 1/2 years, it was well worth the wait. The drivers are rs225's, rs150 and a Vifa PL series tweeter.



More photos can be found on my web site.
 

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Elite Shackster , HTS Moderator Emeritus
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Nice. OB midrange, ported bass cab, and sealed tweeter?

I like the two tone, and the oak really ties in well with the mission-style equipment rack.

Good job!
 

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Thanks, the bass boxes are sealed. First time for a open mid-range, so far they sound real good. The sweet spot seems to be a much larger area.
 

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Elite Shackster , HTS Moderator Emeritus
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I have been trying for a full OB setup using the same bass drivers and a different MTM arrangement up top. The general shape of the current design is very similar.

Sadly, we are selling our house soon, so all my effort has been in cleaning and maintenance and apparently potential buyers don't like to see speaker parts strewn all over the basement!

Do you have any measurements of the final product? I'd love to see the impedance profile and FR of this.
 

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Discussion Starter #5
Moving does make it tough, I moved three years ago.

I did save some frequency reponses from Arta. I also can use my Woofer Tester to post a impedance profile. I'll have to setup the test rig again so that I can post the info. I can only do the impedance test separate because I use active crossover's, not sure if this will help you.
 

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Discussion Starter #6
Do you have any measurements of the final product? I'd love to see the impedance profile and FR of this.
Anthony,

Here is a response taken from my living room and the speaker is at it's normal sitting place. The Mic was 1 meter from the speaker at a height of between the tweeter and the mid driver. I would like to take some measurements outside but I would have to bring the DCX and the amps outside. The one big draw back of using active crossovers.

The green line is the response, disregard the other color line. I will try to get some impedance plot soon.

 

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Thanks,

I'm liking the sound very much, it seem to open the sweet spot, making it much larger. The clearity of the drivers really stand out.

I'm going to build one mid-tweeter box sealed to compare the two.
 

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Elite Shackster , HTS Moderator Emeritus
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OB is great for any driver because it has no (or very little) box resonance. Lack of that and a delayed back wave make the brain interpret the sounds as spaciousness. Your brain has sort of a "gate" filter on hearing. Anything a few ms after the initial sound is interpreted as ambiance, i.e. not part of the main signal. The effect is mesmerizing.

The first time I saw Magnepan 1.6's demonstrated, I did a double take because it sounded like the guitar was really in the room.

Problem with OB's is the bass. The cancellation rolloff is pretty severe and you need some rather large baffles to get down to just 80 Hz. Disturbingly large if you want down to 20 Hz.

So Ken's solution is what many believe to be ideal: sealed or ported bass section, OB midrange, and a tweeter to fill it out. A good compromise taking in the best of each of the drivers and cabinet designs.

Ken, one other thing you may want to try is a second tweeter out of phase behind, to give you full dipole in the upper octaves. A buddy of mine did that and the effect was remarkable. It does require a bit of tweaking of the crossover, though -- usually just adjusting the padding resistors, though. Since you are active, it shouldn't affect you at all. Worth a try if you have two more tweeters laying around.
 

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Discussion Starter #10
I do remember Henry Kloss selling a tower speaker through Cambridge Audio Works that used the rear firing tweeter. They did sound very good. I don't know if they sold many.

The only draw back to the OB mid is the looks. I'm thinking about building a enclosure out of grill material that will hide the back of the drivers.
 

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Those look fantastic. I just can't believe the talent that hangs out on this site. You should be very proud of your creations, they look great!
 

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Ken, they look great, don't cover them up! Unique speaker projects like that are what make DIY so cool! You can make the open back look great as well by dressing up any wire connections with some thicker wire and nice heatshrink, techflex, or as I just saw for the first time in this thread by StereoClarity, solid copper!

Nice spikes too.
 

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Discussion Starter #16
Thanks for all the feed back.

I haven't made any changes to the setup, I guess I'm loving the way they sound. This winter I will be building a set of closed mid/tweeter boxes to compare against the open mid setup.

Ken
 
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