Announcement

Collapse

Midwest Audio Fest

It’s that time audio enthusiasts! Registration for the 2019 Speaker Design Competition is now open! Visit midwestaudiofest.com for details and to list your speaker project. We are excited to see all returning participants, and look forward to meeting some new designers this year, as well! Be sure your plans include a visit to the Parts Express Tent Sale for the lowest prices of the year, and the Audio Swap Meet where you can buy and trade with other audio fans. We hope to see you this summer! Vivian and Jill
See more
See less

Klipsch Forte clone?

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • Klipsch Forte clone?

    Hi,

    this is my first post here. I'm a pretty good woodworker with a full wood shop. Ive been torn between buying a set of old school big horn speakers or building them. I truly like the design of the Klipsch Forte model with the following specs:

    cabinet 36 X 16.5 X 13

    12 inch woofer
    15 inch passive radiator on back
    1 inch compression horn tweeter
    1.75 inch compression horn midrange
    99 db sensitivity @2.33
    38 - 20 khz
    5.2 kHz tweeter crossover
    650 hz midrange crossover

    I am planning on using these with vacuum tube amplifiers so I need the sensitivity, that's the number one priority.

    can I get some random thoughts from other builders here on parts, designing the crossover, what kind of sensitivity I can expect or if I can even do better than 99 db, etc. should I abandon the passive radiator and vent the cabinet? Basically anything that might help me build such a speaker. I may even be able to use better parts than Klipsch, part suggestions would be great too.

    im retired with tons of time now, I used to build speakers when I was in high schools and in my 20's. I'm finding that typical dome tweeter acoustic suspension speakers are not getting the same sound I enjoyed back in the 60's and 70's. I want a speaker sensitive enough where I could actually hear the noise floor of the amp when the volume control is completely gounding the input. Speakers below 88 db are great for class D amps but not great for single ended triodes. I could have just ordered a bunch of random parts here but thought why not see what the group thinks of this project idea first!

    thanks

  • #2
    Recently I spent some time pondering a horn loaded home system and evaluating components. For the tweeter, I can recommend the B&C DE360. https://www.parts-express.com/bc-de3...bolt--294-6042

    It is the finest HF compression driver I have ever heard or measured above 1.8kHz, when used at home levels of a couple watts or less. It is real hifi, with very smooth response and very clean impulse response. This is because the annular diaphragm greatly simplifies the phase plug design. Unfortunately, the small size means the mounting holes are closely spaced, and not many horns fit it. B&C doesn't even have a horn that fits it, although you can probably modify one easily. I used it on the small Faital aluminum horn in the 3-hole pattern, which it fits without modification. I only had one of these, so listening was done in mono. I may be able to post some plots I made on my laptop later. I am not a big fan of that Faital horn however, so I think there are other horns you could modify the mounting holes on that may sound better, depending on how low you cross it. Most horns start to sound 'honky' if you get too close to their cutoff frequency, IMHO. The Faital HF108 driver would also be an option. I also bought some of the large 'closeout' B52 horns PE sells and listened to them with B&C DE550 drivers for about 1 week, crossed at 1.3kHz to cone mids. This was also very nice, but the DE550 with it's conventional diaphragm and phase plug does not have the near ideal performance that the DE360 has, but it has a lower crossover potential. In the end, I decided to stay with my AMTPRO4 hf drivers, but the DE360 made the choice very hard.

    For a midrange horn, I was pondering the PRV D3220Ph driver, coupled to the large rectangular PRV horn. You might be able to cross it at 800Hz, maybe lower. Then you could cross to the DE360 anywhere from 1.8kHz to 5kHz. https://www.parts-express.com/prv-au...bolt--294-2853
    You could also ponder the PRV D4220Ph driver. However, I have never used or measured either one of these drivers, so I can't attest to their performance. I have used the older, similar Selenium versions of these and they were good. PRV was apparently formed from former Selenium people after JBL bought Selenium, so many of their designs are similar. I do not recommend the smaller, cheaper D250Ph or the Selenium equivalent. I have used both of these in commercial designs and they distort easily. You have to do your own QC on them and re-seat the diaphragms sometimes. If you get the idea I am not a fan of titanium diaphragms, you are right, although they can sound fine in the 800Hz to 3kHz region.

    BTW, I work in pro sound reinforcement, so I have a number of drivers and horns sitting on the shelf I have evaluated and used over the years.

    Where designs like the Klipsh and similar JBL ones fall down in ultimate transparency, IMHO, is in trying to cross a large one woofer to a horn above the frequency where the cone begins to break up. For a 15 inch speaker, this can be 500 Hz or even less. This means if you use both a mid and hf horn, you really need a 4-way system, using 2 or more 6.5" midbass speakers. Also, I wouldn't want to try and design a passive crossover for all this, I was using a DSP speaker processor for my listening. Massive eq is required to make these things approach flat response on-axis.

    I guess another factor which convinced me to stay with my direct radiating system for now was something I read a few weeks ago, where some people in Colorado did blind A/B testing a couple years ago between the JBL M5(?) with horn HF, and the Revel top of the line direct radiator. The Revel won. Someone on this board had posted a link to the information. Good luck.
    "She don't love my speakers anymore..."

    Comment


    • #3
      I guess another factor which convinced me to stay with my direct radiating system for now was something I read a few weeks ago, where some people in Colorado did blind A/B testing a couple years ago between the JBL M5(?) with horn HF, and the Revel top of the line direct radiator. The Revel won. Someone on this board had posted a link to the information. Good luck.
      thanks, I'm going to start making a list of potential drivers. I'm committed to using horns though. My wife and I went to Axpona in April and we listened to about 100 different speaker manufacturers, it was a great experience because I truly discovered that I preferred the speakers with horns! And horns were very popular this year. We listened to some dome speaker systems that cost $30,000 or more, and I soon found that every dome tweeter system started to sound like the next. In fact. Since I am using all vacuum tube amplification, that I built myself, so efficiency/sensitivity is the one goal I won't compromise on. Everything is a trade off as I know in building tube amps, but if you lock down the one parameter you're not willing to compromise on it starts to make it easier to get anywhere with the design because you learn your boundaries in the design goals. The revel system is only 88 db it would require probably over 20 watts for it to open up. I will have to use a passive crossover because I don't want to build a vacuum tube crossover! The Klipsch Forte has a 15 inch passive radiator and 12 inch driver, I've never tuned a PR system and I hear it's not an easy task. So I would consider a reflex enclosure. I don't even know if PE sells a 15 inch PR!

      Comment


      • #4
        I faced exactly your questions and took a different path. I had a like new pair of Fortes that I upgraded with new diaphragms, exotic components in the crossovers, stiffening panels, etc. I sold them because I switched to a better system. I started with a 4 Pi cabinet custom made by a local cabinet shop, Eminence 15" for bass/mids and Eminence horn plus Radian 475 compression driver for the tweets. The drivers are head and shoulders above the old Klipsch drivers. I use MiniDsp to crossover/ bi-amp the bass and tweeter. Audio nirvana with DIY 845 SET's driving the tweeters and an AES/Cary SuperAmp (PP/15 WPC with triode strapped KT88 tubes). If you have four channels of tube amplification available, a MiniDsp 2x4HD will, IMO, provide a superior system at a lower price than a DIY Forte clone. Sensitivity is that of the Eminence Bass driver, horn has to be padded down 10 dB. Will give you something to think about, keep you awake nights and maybe even keep you out of the bars while you figure out what you want to do....... ;-)

        Comment


        • #5
          If you are intent on building a horn then plan on getting it measured to be able to design a passive x-o. A ported box will also be easier to design. The Klipsch above is a large stand mount, where a full baffle step would reduce the woofer sensitivity by 6 dB.. You might consider multiple woofers or a tower speaker to pick up some sensitivity. You might also browse DIY Sound Group for ideas and pre designed kits.
          John H

          Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

          Comment


          • #6
            Originally posted by windcrest77 View Post

            thanks, I'm going to start making a list of potential drivers. I'm committed to using horns though. My wife and I went to Axpona in April and we listened to about 100 different speaker manufacturers, it was a great experience because I truly discovered that I preferred the speakers with horns! And horns were very popular this year. We listened to some dome speaker systems that cost $30,000 or more, and I soon found that every dome tweeter system started to sound like the next. ...
            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.
            "She don't love my speakers anymore..."

            Comment


            • #7
              I don't know why some of Klipsch speakers placed the Passive Radiator in the back. IMO it always sounds best when the PR is in the front as the bass just sounds more articulate.

              Comment


              • #8
                DIYSG Titans. (One of my all time fav pics). The mid is a horn loaded. cone speaker. 99db.

                Comment


                • #9
                  To the OP (or anyone), there is a relationship between the horn mouth dimensions and the dispersion control bandwidth. Simply, larger horn mouths can control dispersion down to lower frequencies. D.B. Keele wrote an AES paper about this decades ago in regards to his CD (constant dispersion) horn designs for EV. There are more exact equations involving calculus that I have implemented in a Mathcad program to help design large line array systems. But one of the major reasons I decided to abandon a horn design for the home is the vertical directivity of off the shelf horns I could buy from PE or other dealers. The largest PRV 2" throat horn is about 18" W x 10" H. So even though the horn is spec'ed at 40 degrees vertical, it will actually start to widen below about 1.5 kHz, so that by 500 Hz it will probably be approaching 180 degrees! I don't think they had polar plots on their spec sheet. And I didn't want to custom build a larger MF horn myself, so I would have had to live with a bad ceiling bounce around 1 kHz! Or rotate the horn 90 degrees, but I would still get nominally 90 degree vertical dispersion, along with other compromises.

                  Here is a post where I show the mid-high module of my current system: http://techtalk.parts-express.com/fo...the-double-d-s
                  The 30" high midrange line, along with the woofers below, control the vertical coverage very well to below 300 Hz. I have recently changed the upper crossover frequency to 2.7 kHz, which helps limit the dispersion of the AMT tweeter even more, and pulled the 'boxes' out from the back wall more, further increasing the direct to reflected energy at the listening position. I re-eq'd with Omnimic, of course (ah, the beauty of digital crossovers). I am really happy with the sound. The best I have ever achieved. I have used tweeters and mids from Accuton, Scan Speak, Seas, SB, Peerless, Tang Band, ... before I kicked the dome habit.

                  YMMV
                  "She don't love my speakers anymore..."

                  Comment


                  • #10
                    Originally posted by Roger Hill View Post
                    I faced exactly your questions and took a different path. I had a like new pair of Fortes that I upgraded with new diaphragms, exotic components in the crossovers, stiffening panels, etc. I sold them because I switched to a better system. I started with a 4 Pi cabinet custom made by a local cabinet shop, Eminence 15" for bass/mids and Eminence horn plus Radian 475 compression driver for the tweets. The drivers are head and shoulders above the old Klipsch drivers. I use MiniDsp to crossover/ bi-amp the bass and tweeter. Audio nirvana with DIY 845 SET's driving the tweeters and an AES/Cary SuperAmp (PP/15 WPC with triode strapped KT88 tubes). If you have four channels of tube amplification available, a MiniDsp 2x4HD will, IMO, provide a superior system at a lower price than a DIY Forte clone. Sensitivity is that of the Eminence Bass driver, horn has to be padded down 10 dB. Will give you something to think about, keep you awake nights and maybe even keep you out of the bars while you figure out what you want to do....... ;-)
                    Great! This sounds much like the direction I want to go in and it will give me something to think about. I've built several tube amps but my favorite right now is a KT88/6550 single-ended. I wired with a switch to the screen to run as strapped triode mode or ultralinear pentode mode, it puts out about 9 watts before clipping. I can run 6L6, EL34, KT120, or 5881 in the same socket although I have not yet rolled tubes with that amp yet, I want to verify the voltages before I try that too much. This amp sounds great with my bench speakers I now need to get a big speaker I can tweek. The other speakers in the house are good but basically not suited for SE amps.

                    I have no problem making another tube amp and driving the mid/tweeter separately from the woofer. But I'm not quite ready to put DSP in the path. But now that I think of it I may use the MiniDSP to determine the design of the passive crossover, just to easily try out and hear a lot of different crossover points and what I need to pad down. Then make a passive filter to roughly match.

                    Running some KT88's or KT120's PP for the bass and using SET (or UL pentode) for the top sounds pretty interesting and gets me over a lot of efficiency issues too with only having 9 watts currently!

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

                    Thanks a lot

                    Comment


                    • #11
                      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. ...

                      Hope this helps.
                      Of course I didn't mean to disparage domes in general... At Axpona they all just started to sound alike but they still sounded good. But they sounded alike enough that my wife and I had our doubts about a $30,000 speaker adding much value over the best $5,000 speaker. In any case these speakers didn't suit my DIY amps, they suited higher current amps. I sought out auditioning low wattage tube amps hooked up to speakers that made sense for a low wattage tube amp. IOW speakers that made sense for the amps I like to build. And at the end of the weekend we kept coming back to a few rooms with reasonably priced high efficiency horns hooked to reasonably priced tube amps. One of those was the Forte, although it wasnt the best horn we heard by far, I just used that as a starting point for build ideas. Boundaries in the audio world help you get somewhere, consumers without boundaries is where the snake oil salesmen make a killing. My design boundary now is 99db or better!

                      At Axpona efficiency and coupling the room air to the diaphragm via the horn simply made those tube amps sing more than all the other design aspects one could consider was my conclusion. A very sensitive speaker will be capable of reproducing the noise floor of an amp, the low level Johnson noise produced by carbon resistors. We've all heard that same noise from super efficient PA horns when the band is on a break. I don't mind some noise as that floor is soon masked by the music, heck when my air conditioning kicks on I have more background noise anyway, I no longer pay much attention to noise specs. Also I built a 300B amp that produces as much as 5% THD, that amp with a high efficiency speaker still sounds better than my Integra AV receiver with 86db dome Paradigm speakers listening to non-electric instruments. The harmonic distortion of the 300B is all at the second and fourth nodes (octaves). High efficiency speakers detect the smallest voltage changes and convert that to sound, measurable with a simple oscilloscope hook up. Low efficiency needs more current, the noise floor of my amps are inaudible on my 86db Paradigms. Vacuum tubes are voltage devices that swing very large voltages at any desired frequency but at very low current, the current needed to drive the low impedance speakers comes via the output transformer converting a > 500 volt swing into a few volts swing but at greatly increased current (ohms law), producing watts. Transistors produce current from the outset and need no output transformer and work great with my Paradigms. So I've boarded the big box with horns train! Thanks for your input.

                      Comment


                      • #12
                        Originally posted by Unbiasedsound View Post
                        I don't know why some of Klipsch speakers placed the Passive Radiator in the back. IMO it always sounds best when the PR is in the front as the bass just sounds more articulate.
                        I'm not sure why but most commercial PR systems I see have the PR 180 degrees out of phase with the woofer. Wouldn't a front mounted PR be producing a wave that simply cancels out the bass of the woofer? Since the PR will always be moving out when the woofer is moving in and vice versa, creating two 180 degree out of phase waves from the same baffle? Cancellation of bass energy at the listening position would occur no?

                        Comment


                        • #13
                          Originally posted by wavefunction View Post
                          To the OP (or anyone), there is a relationship between the horn mouth dimensions and the dispersion control bandwidth. Simply, larger horn mouths can control dispersion down to lower frequencies. D.B. Keele wrote an AES paper about this decades ago in regards to his CD (constant dispersion) horn designs for EV. There are more exact equations involving calculus that I have implemented in a Mathcad program to help design large line array systems. But one of the major reasons I decided to abandon a horn design for the home is the vertical directivity of off the shelf horns I could buy from PE or other dealers. The largest PRV 2" throat horn is about 18" W x 10" H. So even though the horn is spec'ed at 40 degrees vertical, it will actually start to widen below about 1.5 kHz, so that by 500 Hz it will probably be approaching 180 degrees! I don't think they had polar plots on their spec sheet. And I didn't want to custom build a larger MF horn myself, so I would have had to live with a bad ceiling bounce around 1 kHz! Or rotate the horn 90 degrees, but I would still get nominally 90 degree vertical dispersion, along with other compromises.

                          Here is a post where I show the mid-high module of my current system: http://techtalk.parts-express.com/fo...the-double-d-s
                          The 30" high midrange line, along with the woofers below, control the vertical coverage very well to below 300 Hz. I have recently changed the upper crossover frequency to 2.7 kHz, which helps limit the dispersion of the AMT tweeter even more, and pulled the 'boxes' out from the back wall more, further increasing the direct to reflected energy at the listening position. I re-eq'd with Omnimic, of course (ah, the beauty of digital crossovers). I am really happy with the sound. The best I have ever achieved. I have used tweeters and mids from Accuton, Scan Speak, Seas, SB, Peerless, Tang Band, ... before I kicked the dome habit.

                          YMMV
                          Nice project. I'm not at this level yet. I'm sure my methodology in all this will be trial and error! To make trial and error faster I will probably pick up one of those miniDSP's, try a lot of different crossover points and hopefully begin to see and understand what you mean here about horn dispersion and frequency. Most things seem to come down to selecting the best compromise in trade offs. If I'm getting my efficiency and a relatively flat response I'll be very happy, then move on to dispersion which may involve compromising something else!

                          Comment


                          • #14
                            Originally posted by windcrest77 View Post

                            I'm not sure why but most commercial PR systems I see have the PR 180 degrees out of phase with the woofer. Wouldn't a front mounted PR be producing a wave that simply cancels out the bass of the woofer? Since the PR will always be moving out when the woofer is moving in and vice versa, creating two 180 degree out of phase waves from the same baffle? Cancellation of bass energy at the listening position would occur no?
                            PR works just like a Port.

                            Comment


                            • #15
                              The passive radiator goes in and out of phase with the woofer at different frequencies. This occurs to some degree no matter where it is positioned in the box. Like a port, the PR has a frequencies where it opposes the woofers motion and frequencies where it assists the woofers motion.

                              Comment

                              Working...
                              X