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The Reflexos: A simple, elegant OB / VB, passive / active hybrid speaker.

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  • jonasz
    replied
    Re: The Reflexos: A simple, elegant OB / VB, passive / active hybrid speaker.

    Originally posted by fjhuerta View Post
    Nevertheless, when I sat down in the sweet spot and turned up the volume, bass was indeed... strange, for the lack of a better word. It was there - just not the way I'm used to. I'm now assuming that due to the radiation pattern, I was getting bass without so many nodes. As I said before, the level was correct. It was just lighter and far, far more defined.
    I think this is a little strange because your woofers are still boxes right? Maybe the combination of small woofers that don't dig very deep and the fact that the upper bass is dipole make the illusion of all dipole bass?

    I hope you continue to explore dipoles, there's a need for more designs that don't cost a fortune I think. If you're not a real bassjunkie a couple of decent 10" or even 8" in an H-baffle will provide enough bass for normal listening levels. Of course you will need some eq, but you have the minidsp anyway so...

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  • jclin4
    replied
    Re: The Reflexos: A simple, elegant OB / VB, passive / active hybrid speaker.

    Super cool project and stellar execution! I particularly found your impressions on midrange response useful and encouraging. I've got a passive 3-way with open mids project in the works (need to pick it up again come springtime) and I'm sure I'll be referring back to your writeup many times.

    Leave a comment:


  • fjhuerta
    replied
    Re: The Reflexos: A simple, elegant OB / VB, passive / active hybrid speaker.

    Poor man's power response.Click image for larger version

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  • fjhuerta
    replied
    Re: The Reflexos: A simple, elegant OB / VB, passive / active hybrid speaker.

    Some semi-boring tech stuff.

    Bass alignment. Sorry professor, my dog ate my homework. I can't seem to find the bass alignment documents. I want to have this speaker fully documented, so I'll re-do it later.

    Cone displacement. Again - it's dependant on the bass alignment documents. Suffice to say, speaker extension on the dipole is not an issue - there's more displacement on the vented box module than on the dipole. Surprising, to say the least. That's also the reason why the bass box has a bandpass filter, and not a lowpass one. The box is tuned at 30 Hz, and the bandpass filter's low limit is 30 Hz, 48db/Oct L-R.

    Off axis response. This is interesting. No, really, it is. From 0 to 60 degrees. No bass module included - this is the dipole panel only, corrected for dipole cancellation (using the MiniDSP).

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    0 Deg.

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    15 Deg.

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    30 Deg.

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    45 Deg.

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  • fjhuerta
    replied
    Re: The Reflexos: A simple, elegant OB / VB, passive / active hybrid speaker.

    Some pics of the finished speakers.

    I'll be using Flickr... the PE forum's setup really messes up photos!











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  • arlis_1957@yahoo.com
    replied
    Re: The Reflexos: A simple, elegant OB / VB, passive / active hybrid speaker.

    wow, those look really nice. good write-up

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  • jonasz
    replied
    Re: The Reflexos: A simple, elegant OB / VB, passive / active hybrid speaker.

    Awesome!
    Fun that more people get into dipoles.

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  • fjhuerta
    replied
    Re: The Reflexos: A simple, elegant OB / VB, passive / active hybrid speaker.

    Listening impressions
    Last edited by fjhuerta; 01-06-2013, 09:11 PM.

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  • fjhuerta
    replied
    Re: The Reflexos: A simple, elegant OB / VB, passive / active hybrid speaker.

    Crossovers

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    I didn't use any stock files with added diffraction / dipole modeling. Every measurement I did I took from my own baffle, JustMLS and my calibrated Dayton ECM-8000.

    My target curves were 4th order L-R all around. In order to reach them, I used a 4th order electrical on the tweeter, and a 2nd order electrical with a tank on the woofer, to kill any hint of a break-up in them. Simple... very simple.

    BONUS: check out the crossover. See anything unusual? Well, no. Everything is pretty normal - except for a simple thing. There isn't a single resistor there. The minimal matching I needed to do between woofers and tweeter I accomplished by using the DCR of the inductors. Some of them are 14 GA, others 15, 18 and 20GA. The tweeters and woofers simply came together perfectly. I was impressed at the way I picked the exact drivers I needed to accomplish this (actually, I'll be brutally honest - it was sheer luck, and I was actually very worried the tweeters would not reach the woofers' output at 1W).

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    Here are the RS150's with the Neo3. Look at that dipole response. It needs some TLC. But that isn't going to happen on the passive crossover - this will help in keeping efficiency as high as possible. The Neo3 will never win any awards for smooth FR, but at least in a dipole its response looks a lot better than anything I've ever seen with their cups on. I'm not going to try to fix the dips at 3 and 7 KHz. They sort of fill up off axis, anyway. I suppose the front of the Neo3 (with its metallic grille) really doesn't help FR. Anyway.

    The active crossover does quite a lot of things. It bumps up bass response on the mid-panel, then crosses over to the woofer using an L-R 12db/Oct filter set at 120 Hz. On the woofers (which are tuned at 30 Hz), it helps with BSC, and crosses over at 120 Hz, 24db/Oct at 120 Hz. I had to drop the panel response by 6 dB, too.

    I simulated the whole thing using LSPCad and a DCX2496 module. Came up with something like this.

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    Again - you'd need the .XML file to configure the MiniDSP. I can send it to you if you'd like. PM me.
    Last edited by fjhuerta; 01-06-2013, 10:11 PM.

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  • fjhuerta
    replied
    Re: The Reflexos: A simple, elegant OB / VB, passive / active hybrid speaker.

    Dipole panel modeling.

    I used The Edge to model the baffle. At first I tried to minimise the baffle effect. Realistically, though, it didn't matter. As long as I followed ABCDipole's instructions on not going above around 22 cms. width, response was pretty good.

    Construction.Click image for larger version

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  • fjhuerta
    replied
    Re: The Reflexos: A simple, elegant OB / VB, passive / active hybrid speaker.

    Preliminary tests.
    You can read all about them here.

    Suffice to say, cutting the baffles to size makes all the difference in the world. HINT: Do read and understand John K's ABCDipole .zip package - follow the instructions and you'll end up with an extremely nice speaker!

    Design.
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    Google SketchUp was my friend. I'm not building any other speaker without modeling it there first. I placed the speaker in different rooms, and got an excellent idea on how the speakers would look at home.

    The dipole panel is a simple L-shaped piece, with a reinforcing piece on the back. The vented box is about 33L in size. If you need accurate dimensions, you can open the SketchUp file I attached to this post.

    EDIT: The forum didn't let me attach a .zip, .rar or .skb file, so if you need them, just send me a PM and I'll get you the files.
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  • The Reflexos: A simple, elegant OB / VB, passive / active hybrid speaker.

    Objective.

    To build a slim, small, high-WAF speaker not easily affected by room acoustics.

    I've wanted to build an open baffle / dipole speaker for quite some time, but size considerations and driver price kept me away from them. Due to solutions like the MiniDSP, and efforts like John K's NaO speakers, I decided to build a hybrid speaker in every way.

    It's not fully active - the x-over between the woofers and the mid / tweeter panel is active, but the mid / tweeter X-O is passive. The active x-over does some response shaping and time alignment too - plus I'll eventually use it to add basic loudness contours (since my equipment does not have tone controls). (The MiniDSP is simply incredible).

    And it's not fully dipolar - from 120 Hz and up, the mid / tweeter panel crosses over with 4th order L-R slopes; below that, from 30 Hz to 120 Hz, a bandpass filter allows the bass enclosure to deliver solid bass without overloading the little woofers.

    It's fully fun, though. And a revelation to listen to, coming from boxed speakers.

    The name.

    The original name was Valkyries. I don't know why. For a while, they were going to be the Elyseums. Neither name stuck. Then I listened to them and one word came to mind: "truth". Unfortunately, Veritas, and Verita are already taken.

    So I looked at the glossy finish, and the way the drivers interact with their surroundings, and one name came to mind: Reflections.

    "Reflexos" is portuguese for that word. Why portuguese? Because that's the language the word looked the nicest.

    The hardware.

    Living abroad, buying big drivers is sometimes out of the question. The last time I tried I spent close to $500 for 4 RS270s. I'm not doing that again anytime soon.

    Besides, I wanted a slim design. True, I could use the woofers in a side-firing configuration, but this being my first OB, I didn't want to add too much complexity to an already unknown design. Plus, once I decided on a Vented Box bass alignment, I could use smaller drivers.

    The RS-150 drivers fit the bill. I could use 4 of them - 2 on the mid panel, 2 on the vented box. They are small. They can be used in slim speakers. They sound great - I've already tried them and liked them. They can go up to 1.8 KHz or so using a 4th order filter. And I already had 8 of them.

    Allright, so the whole design was born because I had 8 RS-150s.

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    (Yep. I used the old ones, with the bucking magnet).

    The tweeter was a bit more complex. At first I wanted to use the Seas DXT tweeter - then I decided I wanted a full dipole from 180 Hz or so on up, so I'd need two DXT's - expensive. I figured I had a pair of Neo3 PDRs from a box speaker I wasn't using anymore, so I decided to take them out of their enclosures and use them on my new design, with a round flushmount faceplate.

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    (I sanded them, removed the B&G logo and painted them gloss black. No free advertisements here!).

    The MiniDSP was sort of a given - I already had it because I used it to integrate a set of small bookshelfs with a 15" woofer succesfully. And I needed it to shape the response, in order to counteract the dipole bass loss and whatever FR abherrations I could find, and the baffle step for the vented woofers.

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    (Yeah, it's the balanced one. No way I'm using the non-balanced unit - with a 1V output, I'd be wasting a lot of amplifier power).

    For amplification, I wanted to go fancy and use a McIntosh MC-250 for the bass units, and two McIntosh MC-30 amps for the dipole panel. Realistically, though - tube amps are a coin toss when it comes to mating with a particular set of speakers. So I took out my Rotel RB-1070 pair of amps.

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    Last edited by fjhuerta; 01-06-2013, 09:23 PM.
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