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  • Raal/Purifi

    Hi everyone, first of all I’d like to say I’ve been deep in this forum for a long time and appreciate all of you. I never post but I’d really appreciate some direction here since an idea of mine would be such an expensive experiment to undertake given my limited experience building almost only kits.
    What do you guys think about pairing the 6.5” purifi woofer with the raal 7020xr and an active crossover using a hypex plate amp?
    Good idea? Bad idea?
    I’d like to put a lot of love into something really special here and I mean it when I say that I’d appreciate any reply I can get.
    Thank you, Luke




  • #2
    This is worth a read - https://www.diyaudio.com/forums/mult...ompact-tl.html

    XRK has done a number of designs with the Purifi but I think this is his favourite. I would go with his design and add a Purifi stereo amp to go with it, search Nord Acoustics, Ghent Audio, and obviously the Purifi site. Or you could go Hypex NC500 or possibly NC400 if you can get hold of some.

    However, if you want to go the Hypex active route no reason why you can’t copy XRKs crossover in the active domain.

    Comment


    • cornajatwa
      cornajatwa commented
      Editing a comment
      I appreciate your reply. I have seen that thread and read through it again after your reply. Lots of good information there. I’ve been hedging my optimism though because I don’t know how much I can trust “XRK”’s judgment. Do you have an opinion concerning either his knowledge or thoughts reflected in his thread?
      Thank you

  • #3
    Originally posted by cornajatwa View Post
    Hi everyone, first of all I’d like to say I’ve been deep in this forum for a long time and appreciate all of you. I never post but I’d really appreciate some direction here since an idea of mine would be such an expensive experiment to undertake given my limited experience building almost only kits.
    What do you guys think about pairing the 6.5” purifi woofer with the raal 7020xr and an active crossover using a hypex plate amp?
    Good idea? Bad idea?
    I’d like to put a lot of love into something really special here and I mean it when I say that I’d appreciate any reply I can get.
    Thank you, Luke


    I'm doing a passive crossover right now for that combination. Keep in mind the low impedance of the RAAL in the lower frequencies. A series capacitor is a must. Here's the impedance graph of the RAAL. Click image for larger version

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    Comment


    • cornajatwa
      cornajatwa commented
      Editing a comment
      You should have a PM. Thank you very much for the reply!

  • #4
    Originally posted by cornajatwa View Post
    I never post but I’d really appreciate some direction here since an idea of mine would be such an expensive experiment to undertake given my limited experience building almost only kits.
    What do you guys think about pairing the 6.5” purifi woofer with the raal 7020xr and an active crossover using a hypex plate amp?
    Good idea? Bad idea?
    I’d like to put a lot of love into something really special here and I mean it when I say that I’d appreciate any reply I can get.
    To a fair extent it depends on your objectives but for most in your position (i.e. expensive to you, little experience) it is likely to be a bad idea.

    A 6.5" 2 way is a budget speaker configuration. It combines a lower midrange sized driver and a tweeter in smallish cabinet with a relatively simple cheap crossover. It has inadequate low frequency performance due to the absence of a woofer, inadequate SPL to handle transients unless you sit fairly close, significantly compromised upper midrange, too large a change in directivity between drivers, etc... It can be a good compromise for a budget speaker and OK with a waveguide as a desktop. Subwoofers will raise sound quality significantly. But a small 2 way with very expensive drivers makes no sense if sound quality in a technical sense is important. A competently designed 3 way speaker (or even 4 way depending on just how expensive the drivers are ) using appropriately sized standard range drivers will offer significantly higher technical performance.

    Having said that DIY is about having fun building what you want. Technical performance is only one aspect and for some it is relatively unimportant. Examples of this are enthusiasts of 1 way speakers, valve amplifiers, and similar. Perhaps this is the case for yourself whereas using the currently most expensive and fashionable drivers is important to your enjoyment. This is for you to decide but the words expensive and really special plus you being new to designing speakers prompted me to post.

    In general the difference between a standard range driver and a premium driver is that the former has a narrower operating range over which it performs well. If a speaker is designed to keep the drivers within their comfortable operating range then the difference in sound quality will be small. At standard levels in a typically sized room in a home with reasonable acoustic properties a competently designed standard range 10-12" or 2 x 8" woofer/s combined with a 3-5" midrange will offer significantly higher sound quality than a 6.5" midwoofer no matter how exotic.

    Comment


    • cornajatwa
      cornajatwa commented
      Editing a comment
      Wow, that was thoughtful. Thank you for taking the time.
      I can always add a sub but is there a different driver combination you’d suggest investigating with that budget? I know that’s a big question.
      I have two reasons for leaning toward that plate amp.
      I’d like to de-clutter by selling my emotiva stuff, stand and put the tv on the wall. The other is the idea of figuring out those active crossovers just sounds fun.

    • rickcraig
      rickcraig commented
      Editing a comment
      Yes, it's building what you want and not what someone else dictates to you.

  • #5
    Click image for larger version

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    • #6
      > I can always add a sub but is there a different driver combination you’d suggest investigating with that budget? I know that’s a big question.

      TMW, TMWW, WMTMW, coaxial T+M plus W (abbreviation?),... Floor standing tower, monitor on stand, on wall either side of the TV,... Sealed, ported, TL,... The configuration is up to you.

      Given a configuration one can rough out the cabinet design and look for standard range drivers to fit. Adjust a bit for actual driver parameters. Iterate and firm up dimensions.

      DSP active crossovers are flexible in terms adjusting crossover points and addressing bumps and dips but one still needs to design the cabinet/waveguide shape and it's influence on the radiation pattern.

      Not sure this has helped much but the question was a bit too open ended. One can of course look at existing designs for ideas and costs. The use of an active DSP crossover will greatly ease the process of substituting drivers of similar size.

      PS How are we supposed to reply to a comment?

      Comment


      • a4eaudio
        a4eaudio commented
        Editing a comment
        Technically, you can't reply to a comment. If that person has posted a regular post I usually just hit quote on the post and copy and paste to replace the post with the comment.

    • #7
      Originally posted by andy19191 View Post
      A 6.5" 2 way is a budget speaker configuration. It combines a lower midrange sized driver and a tweeter in smallish cabinet with a relatively simple cheap crossover. It has inadequate low frequency performance due to the absence of a woofer, inadequate SPL to handle transients unless you sit fairly close, significantly compromised upper midrange, too large a change in directivity between drivers, etc... It can be a good compromise for a budget speaker and OK with a waveguide as a desktop
      Look, I'm a multi way proponent as well but to be fair, I don't consider a two-way design a "poor mans" alternative - not at all. And don't forget that two-way is not limited to two drivers. My last three speaker designs have been two way floor standers capable of well south of 40hz and the performance is outstanding. Will they have the bass SPL output of a 12" high sensitivity woofer - of course not - but is their performance accurate, dynamic and substantial in a reasonable room and at a reasonable listening distance - you bet it is.

      Comment


      • #8
        Originally posted by DeZZar View Post
        Look, I'm a multi way proponent as well but to be fair, I don't consider a two-way design a "poor mans" alternative - not at all.
        Given the price of the 2 way the OP is proposing it certainly isn't for poor men. The laws of physics however will limit sound quality for the reasons listed whereas it won't for designs that use appropriately sized drivers.

        Originally posted by DeZZar View Post
        My last three speaker designs have been two way floor standers capable of well south of 40hz and the performance is outstanding.
        Is that supported by independent assessment such as measurements at standard levels?

        Originally posted by DeZZar View Post
        Will they have the bass SPL output of a 12" high sensitivity woofer - of course not - but is their performance accurate, dynamic and substantial in a reasonable room and at a reasonable listening distance - you bet it is.
        Tempted to take that bet if we can agree on a definition of high quality sound reproduction. Many audiophiles define it as "sounds good to me" which is obviously problematic and if that is your definition then we don't have a practical way to assess it. Others define it more in terms of technical performance with the output following the input with low levels of distortion and, in the case of speakers, broad agreement on what is a reasonably neutral radiation pattern and what is less so. The room response also needs controlling if one is to assess the speakers and not the room particularly at low frequencies where the room response typically dominates the sound quality. If this is more how you define sound quality then perhaps we can work up something together with which to assess the performance of 2 ways of the kind proposed by the OP.

        Comment


        • #9
          Originally posted by andy19191 View Post
          Is that supported by independent assessment such as measurements at standard levels?
          nah man I'm just some micky mouse DIYer with no clue who just slapped any ol drivers into a box I found on the side of the road and yee haw I knew they were goodn's when the neighbours dog didn't run howling from the room...!


          All I'm saying is that you made a two way loudspeaker sound like some pathetic all out compromise and although you can certainly do better with multi way systems I don't believe a well designed two way is so inherently flawed that it will not result in a quality and enjoyable listening experience.

          Otherwise, please, you better help explain to sonus faber that this sad flawed and compromised product was a waste of time https://www.sonusfaber.com/en/products/maxima-amator/ or assist Spendor realise that they've been heading down budget two way street this whole time and have no idea what they're missing out on.

          I guess you might as well just say that unless you have this https://gryphon-audio.dk/shop/loudsp...peaker-system/ your only experiencing budget hi-fi - how sad.

          Comment


          • #10
            Originally posted by cornajatwa View Post
            Hi everyone, first of all I’d like to say I’ve been deep in this forum for a long time and appreciate all of you. I never post but I’d really appreciate some direction here since an idea of mine would be such an expensive experiment to undertake given my limited experience building almost only kits.
            What do you guys think about pairing the 6.5” purifi woofer with the raal 7020xr and an active crossover using a hypex plate amp?
            Good idea? Bad idea?
            I’d like to put a lot of love into something really special here and I mean it when I say that I’d appreciate any reply I can get.
            Thank you, Luke


            OP, if you are serious about pursuing the active path then I'd suggest you check out the Directiva project at Audio Science Review. Its using the Purifi and the DXT tweeter with hypex. https://audiosciencereview.com/forum...project.20407/

            It is in line with what you're trying to do and addresses many of the so-called shortcomings of a 2-way. Any design has tradeoffs and the Directiva aims for low distortion, decent bass in a 0.56 package (Denovo flatpack), good directivity and off-axis performance and good SPL.

            The purifi has been used in some high-performing designs already. Rick Craig responded to you earlier and he's already done one with the Purezza. See here https://www.erinsaudiocorner.com/lou...audio_purezza/ and Selah audios website

            That said, are you set on a RAAL and ribbon tweeter - have you heard that one? The advice of caution before shooting for an end-game design with expensive drivers as a 1st timer is sound. You can always start with a couple starter drivers with comparable crossover points to get comfortable with the active crossovers and then order the Purifi and tweeter when ready. Also keep in mind that designs like this are designed to be excellent and go "low enough" with 2-channel but even better with a couple subwoofers and some sort of bass management.

            I wouldn't get stuck on floorstander or nothing. Depends on your goals, room size and listening distance.

            Comment


            • cornajatwa
              cornajatwa commented
              Editing a comment
              Awesome stuff thank you. I have the continuums and have had the speedsters but haven’t heard any raals. I only know I’m interested in these drivers after reading a lot about them. It’s an experiment I’m willing to take if I can lean a bit on some of this very sort of forum support (like yours) I value and appreciate a lot of perspectives on this site and am curious enough to roll the dice a little bit.
              Thank you very much for taking the time to help me

          • #11
            Originally posted by Colonel7 View Post
            The advice of caution before shooting for an end-game design with expensive drivers as a 1st timer is sound. You can always start with a couple starter drivers with comparable crossover points to get comfortable with the active crossovers and then order the Purifi and tweeter when ready
            Agree. Excellent advice. The only variable is that we don't really know the OP's financial situation. If these things represent chump change to you, congratulations, and by all means, have at it. Personally the shipped price to Australia makes my eyes water so I don't think I'll be considering them for my 50th set of speakers let alone first.

            Comment


            • Colonel7
              Colonel7 commented
              Editing a comment
              Certainly. OP did call them expensive. Expensive to me is $80-125 of drivers per cabinet.and that's a special project.

          • #12
            I think context is important. And needs.

            when I first got into this hobby, I was a college student- plenty of time but limited funds- just working the weekend shifts at the local Radio Shack type shop, and earning some cash tutoring high school students.

            I knew nothing about woodworking or soldering- I hadn’t even picked up a hammer or saw!

            But I set myself the task of building some loudspeaker cabinets. And I had 2 good friends to bounce ideas off.
            I used good drivers, not the best but not the worse. But I did followed an established design and had incredibly the gentleman who build the ProAc Response 2.5 clone website lived in my town!

            After that build I experimented with cheaper drivers, and quicker/simpler cabinets. 50% the cost and size for 80% the performance.

            after 2 more 2 ways; I experimented with building second hand and modifying established designs (MTM). Still they did not compared to DIY designs from experienced designers.

            and then I moved to dipoles. And then I went back to monopoles, this time a 3 way WMTMW.

            This was my dream speaker

            until I had to move overseas.

            After moving into a small apartment I went to small speakers. By small I mean 1/4 cu foot. All the while following other designs; experienced designers with good science/measurements; Troels Gravesen, John Krutke, Dennis Murphy, John Krevskovsky, Curt Campbell/Jim Holtz, and Jeff Bagby.

            I got into room correction with Dirac. Well that got me into the basics of measurements and interest in the speaker/room interface; how far away measurements differ form near measurements, and before you know it individual driver measurements.

            When I went to design my first speaker from scratch, I really didn’t want to wonder “have I chosen the right driver?
            I know I wanted to start with a 2 way, and I just went for the best 7” midwoofer for a 2 way at the time.

            Compared to how much time it takes to properly measure, properly model, and listen/reiterate/refine; a $250 mid woofer purchase seems to easy- if the speaker sounds crap it’s to really on me.

            Think of it this way- I could go and do extra work for $$/hour instead of spending time with my young kids. But I choose the latter. Well-that’s priceless.

            so it all depends.

            Comment


            • #13
              Just to play devil's advocate, I can see a 2 way being more "optimum" if you have a small room and must sit relatively close to the speakers. The integration will probably be better than a 3 way. Plus, you aren't demanding much output, so the advantage of a 3 way is diminished.
              Francis

              Comment


              • JRT
                JRT commented
                Editing a comment
                Much depends on details... If the woofers cross low enough, near 100_Hz rather than mid-triple digits, and if the cross is adequately steep to get them out of the way in the midrange (eg. LR4), then I think that a couple of meters propagatation distance, shouldn't be a problem.

                On infinite baffle firing into halfspace, 2pi spherical, swept volume requirement rises in inverse square proportion to frequency for flat response, quadrupled at halved frequency, one octave. And extending down to 100_Hz requires that midrange has to handle the baffle step transition, another doubling of swept volume requirement in the full transition at lower frequencies to full space from half space, 4pi spherical from 2pi.

                A small midrange wouldn't be suitable in that application if realistic SPL is part of the requirement, which could be as much as 85_dBA from both monitors summed uncorrelated at the listening position at -20_dBFS signal level without pushing drivers beyond Xmax on 0_dBFS crests (Dolby Labs' recommendations for monitor level utilized in high quality mastering). However, some are happy with little fullranges at much lower levels, regardless the distorted listening perception that imposes, the nonlinearity of that perception illustrated in the Fletcher-Munson equal loudness contours, or the more recently in ISO-226.

              • fpitas
                fpitas commented
                Editing a comment
                If you can sit a couple meters away, and if your ears are near the tweeter axis, then maybe. I still think of 3 way as a "larger room" solution.

            • #14
              Originally posted by fpitas View Post
              Just to play devil's advocate, I can see a 2 way being more "optimum" if you have a small room and must sit relatively close to the speakers. The integration will probably be better than a 3 way.
              Due to the wavelength compared to listening distance the integration that is most important is the tweeter and midrange/midwoofer which is likely to be better with a 3 way due to a smaller midrange. A 3 way also has the midrange and woofer integration which a 2 way doesn't but this is less of a concern. So it will depend but with a fair chance a 3 way will edge it.

              Originally posted by fpitas View Post
              Plus, you aren't demanding much output, so the advantage of a 3 way is diminished.
              Clean SPL to resolve transients at standard levels should be OK for a 6.5" driver above 80-100 Hz at 1m. As you move further away it will start to become marginal requiring the lowering of the listening level to maintain fidelity. The low frequency response will obviously still be inadequate and the high frequency compromised by resonances. The former can be addressed by adding subwoofers and increasing the number of ways albeit not optimally but the latter will remain.

              The advantages of 2 ways are lower cost, lower complexity and smaller size. The disadvantage is lower technical performance. The former are going to win for most applications which is why there are so many 2 ways. If you look at a list of commercially available "midfield monitors" there are few 2 ways and those that are listed look rather like "nearfield monitors" with optimistic marketing claims. The reason for looking at studio speakers rather than home speakers is that sound quality at standard levels is an important parameter in this sector and they distinguish between desktop speakers and main speakers.

              Comment


              • #15
                Originally posted by andy19191 View Post

                Due to the wavelength compared to listening distance the integration that is most important is the tweeter and midrange/midwoofer which is likely to be better with a 3 way due to a smaller midrange. A 3 way also has the midrange and woofer integration which a 2 way doesn't but this is less of a concern. So it will depend but with a fair chance a 3 way will edge it.

                Clean SPL to resolve transients at standard levels should be OK for a 6.5" driver above 80-100 Hz at 1m. As you move further away it will start to become marginal requiring the lowering of the listening level to maintain fidelity. The low frequency response will obviously still be inadequate and the high frequency compromised by resonances.
                To connect back to the thread, these statements don't apply to the Purifi driver as measured. The point is that though the driver is extremely expensive (to me at least) it is not a standard 6.5 due to lack of distortion and extended linearity. See Erin's audio corner klippel and hificompass besides the manufacturer spec sheet. I'm sure others have tested it on their own bench.

                ​​​

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