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Klipsch Forte clone?

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  • #17
    The 8" has the TB sub on the bottom and a 10" PR in front.

    Project #2: The 'Tenacious Bass 6' and 'Tenacious Bass 8' Subwoofers - Techtalk Speaker Building, Audio, Video Discussion Forum

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    • #18
      "Did you happen to post any information on this build here, parts list, write up, tuning the cabinet, etc.?"

      No. The cabinets are precisely the 4 Pi cabinets, the bass speaker (Eminence 15") and alignment is exactly what Wayne (at Pi Speakers recommends). The Radian compression driver is reputed to be better than the cheaper ones recommended for the 4 Pi speakers and can be crossed second order at 1,100 Hz. Basic procedure is build everything, measure the responses of each driver in the completed cabinets, go to Active Crossover Designer and input the responses and tweak various filters and combinations until you get what you like, input the resulting filter coefficients into MiniDsp (simple cut and paste from ACD to MiniDsp plugin), connect music source to MiniDsp, MiniDsp to amps, amps to speakers and listen. Tweaking as simple as MiniDsp to your computer and you can make changes even while you listen. Have fun!

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      • #19
        Originally posted by wavefunction View Post

        I think the reason dome tweeter systems sound so similar is because of the power response, you are listening to the room nearly as much as the system. Dome tweeters are hemispherical radiators over much of their bandwidth. Hence they throw large amounts of energy to bounce off the ceiling, walls, and floor (assuming no carpet). I would never consider using one for a serious build without a waveguide to control the dispersion. The designs which use them typically use a single small mid which also has wide dispersion. Horns can be very good at controlling dispersion both vertically and horizontally (if used within their limits), keeping mids and highs off the room surfaces, increasing the critical distance where the direct and reflected sound is equal level. The links from a month or so ago were to work from Floyd Toole of JBL/Revel/Harmon and Earl Geddes. Basically, to have good sound and imaging, the first reflections need to be 10ms or more after the direct sound, and the direct sound from 700Hz to 10kHz needs to have very smooth frequency amplitude response. Phase response is not that important, as long as the group delay within that range is 2ms or less (to the best of my recollection). One way to do all this is to use horns from 700Hz and up, with their controlled directivity. Another way to do this is to use tall ribbon, AMT, or planer magnetic tweeters and line-array or semi-line array midrange configurations, along with a wide room that gets the walls far enough away from the speakers, and/or absorbers and diffusers on the walls (bookcases make diffusers at midrange and absorbers at HF, at least better than nothing). This second way is what I use. I think this is part of the reason many people like tall tweeters, the limited vertical dispersion helps with the biggest culprit for many, the ceiling reflection. People often don't realize how much of an effect that has. At a show like Axpona, judging from Youtube videos I have seen, most of those demo rooms are just shoebox hotel rooms, and the bare walls play a big part, so that speakers that also control horizontal dispersion, i.e. horns, have an advantage.

        In regards to the A/B testing of a JBL horn system vs. a Revel cone and dome system, from pictures of the test room that were published, I think the ceiling height was 10' vs. the typical 8', and there were decorative beams which could act as diffusors and the room was somewhat wide, helping out the Revel. The Revel tweeter is loaded by a small waveguide, helping to limit the dispersion down the 4kHz, I would estimate. And reading the listeners comments, it seems the people that liked the Revel more because of the bass response and midrange transparency. Multiple low efficiency woofers can go quite low, and dedicated small midranges are more transparent than a single high efficiency 15" paper cone driver that is used from 40 Hz to the neighborhood of 1 kHz. Even though the JBL box was expensive, it was still a compromise.

        Hope this helps.
        OK, a dome tweeter can be flat on axis, but has a falling off axis (power) response. A horn often has a rising on axis response, however it will have a flat power response. There may be some exceptions to this but it generally is true.

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        • #20
          Originally posted by AEIOU View Post

          A horn often has a rising on axis response, however it will have a flat power response. There may be some exceptions to this but it generally is true.
          Every compression driver mounted to a horn that I have ever seen, either on a manufacturer's spec sheet or measured myself has a falling HF response when measured without EQ. It is called the mass rolloff. Using exponential horns (as compared to constant directivity) helps minimize the rolloff on axis, but then results in even more pronounced HF rolloff when off axis (they beam the highs more). Yes, the resulting system of driver and horn is equalized flat on axis or at a chosen angle, just like a dome tweeter would be, but the resulting horn system has much tighter dispersion (higher directivity index or DI) than a dome tweeter when used correctly within it's design bandwidth. A CD horn can have a more constant response within it's dispersion window, where the audience is supposed to sit, but the power response outside that window falls very rapidly beyond that. That is what they are designed to do, so that the critical distance in large, reverberant rooms is as large as possible, and speech can be understood.

          There may be some super tweeters with very beamy response that come close to flat on axis response without eq, but I think they are more the exception rather than the rule.
          "She don't love my speakers anymore..."

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          • #21
            Originally posted by wavefunction View Post

            Every compression driver mounted to a horn that I have ever seen, either on a manufacturer's spec sheet or measured myself has a falling HF response when measured without EQ. It is called the mass rolloff. Using exponential horns (as compared to constant directivity) helps minimize the rolloff on axis, but then results in even more pronounced HF rolloff when off axis (they beam the highs more). Yes, the resulting system of driver and horn is equalized flat on axis or at a chosen angle, just like a dome tweeter would be, but the resulting horn system has much tighter dispersion (higher directivity index or DI) than a dome tweeter when used correctly within it's design bandwidth. A CD horn can have a more constant response within it's dispersion window, where the audience is supposed to sit, but the power response outside that window falls very rapidly beyond that. That is what they are designed to do, so that the critical distance in large, reverberant rooms is as large as possible, and speech can be understood.

            There may be some super tweeters with very beamy response that come close to flat on axis response without eq, but I think they are more the exception rather than the rule.
            Obviously, I'm going to have to quote a reputable source to settle this, just a matter of me finding it.

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            • #22
              Roger Hill, thanks I'm looking into the pi and minidsp. Being a tube guy I was hesitant to use DSP until I saw that it can actually serve as a DAC , I thought it would be doing an extra A/D conversion. For vinyl it would have to incur another conversion, but for lossless FLAC files it may be fine considering my input to the tube amp is from a DAC today. This looks like a route I'm likely to be successful at in the end.

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              • #23
                Hi Windcrest. Vinyl adds one more decision point to the equation. Some of the Minidsp units have both analog and digital inputs before doing the DAC that is the heart of the thing. You will have to look at the input/output specs or pictures and decide which inputs you want. The real decision for me came after my original Minidsp 2x8 died after perhaps 12 years. (actually, I may have killed it by plugging something in with reverse polarity) I went with an upgrade replacement unit (the DA8) that allows FIR processing, so that you can do linear phase crossovers, i.e. transient perfect speakers. I am now in the process of upgrading my software skills to use REW and rePhase. I'm not there yet,still listening to the old set of filters re-input to the new unit. I have just gotten bored with keeping vinyl clean and am perfectly content to listen to only CD's. Have fun with this, it is more straightforward than learning to engineer passive crossovers.

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