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  • 8'' two-way any reason why not?

    Is there anything wrong with building an 2-way with an 8'' woofer. They seem to be frowned upon. I was at a get together last week where I mentioned that I was thinking about building a TM with an 8'' woofer and I got 'no, no, no, you don't want to be doing that'. It will sound awfull. I didn't have time to persue the subject because we were all getting ready to leave. So, what are your thoughts?
    No matter where you go, there you are.
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  • #2
    Re: 8'' two-way any reason why not?

    No reason why not. Don't know if these drivers are still around, but this is a good one.

    http://murphyblaster.com/content.php...ifa_Tower.html

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    • #3
      Re: 8'' two-way any reason why not?

      I've actually been wondering about trying to get into the DIY design phase of this hobby by putting together some fairly straight forward TM 2-way's. The drivers in question are the Hi-Vi M8n (not the a variant, because of cost) and Dayton's RS28A-4. My big issue is trying to get some modeling information so I could put these things together in software to see what they'd act like, but the sensitivity in their respective documentation is pretty similar and the freq. response curves make me want to think they'd be a good combination.

      Eventually I'd like to do an MTM center with the same driver set as well. Cap it all off with a powered sub of some sort (I keep going back to 13.5 in JL Audio "car" subs with this paper tiger) and that could all be something... Thoughts on this mess?

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      • #4
        Re: 8'' two-way any reason why not?

        I have a HiVi F8 / Seas 27TDFC design in the offing. Several other people I know are also working on some 8" 2-ways. The "frown" on this layout comes from off-axis frequency response, the staunch reply being that the 8" will start to narrow its polar response at the crossover frequency, and thus not sound as natural. This is generally true, I think.

        It does depend on both the driver and XO frequency. The F8 has flat 30 degree off axis response out to 2Khz+, 45's aren't shown on the mfr graphs. It'll go deeper than most 7 inch drivers, and it'll sweep a lot more air - 210 square cm of Sd vis 140-150 square cm for a 7" driver. So it'll play louder, too. And, with some of the tweeters available now, you are NOT limited to 2Khz + for a tweeter. Lots of great designs using the 27TDFC (or the RS28 or other robust tweeters) go to 1600-1700Hz, and usually with an LR4 XO.
        Is it a compromise? Yes. You are giving up some of the off-axis response (past 30 degrees off axis) for higher SPL and generally deeper bass.

        I chose the F8 because there aren't any peaking nasties to deal with, requiring an unusually low crossover frequency. It sounds smooth out of the box and looks really cool, too

        Cheers + Happy Thanksgiving!!

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        • #5
          Re: 8'' two-way any reason why not?

          I agree. With some of the current tweeters, 1.5-1.8k crossovers are not a problem and should mate well to an 8". The bass and lower mid clarity can be better. The only real drawback is a larger box.
          audioheuristics isn't around right now...

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          • #6
            Re: 8'' two-way any reason why not?

            Six and a halfs allow going higher to the tweeter, and if you use two in an MTM you can get more displacement than with one eight, along with improved vertical pattern control and higher sensitivity to compensate for the baffle step.
            www.billfitzmaurice.com
            www.billfitzmaurice.info/forum

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            • #7
              Re: 8'' two-way any reason why not?

              Decades ago, 8" 2ways were fairly common... and many sounded real nice. Problem is, not many drivers are made similar to those types... which often had better upper midrange, but less low bass response/output.
              I'm not a fan of ear-level tweeters, but a 8" 2way might benefit from the woofer being above the tweeter, but the xover might be a pain--Haven't studied passive filters yet, but sure one would be common... active would need delay.
              Thinking about a future 8" 2way myself, and if it goes forward, I'll get a 24db active filter with delay. I'd go sealed, and might try a 3/4" tweeter to match the narrower dispersion at xover.

              GC

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              • #8
                Re: 8'' two-way any reason why not?

                One reason to not use an 8" driver in a 2 way is the beaming at higher frequencies, but folks like Mark K, Linkwitz, Jon Marsh have had good results with tweeters that can cross low enough to eliminate most of the beaming problems associated with larger diameter midranges.

                I've had my eye on the Seas Excel 8" nextel woofer for something like this. Looks like it is very extended in the lower treble.

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                • #9
                  Re: 8'' two-way any reason why not?

                  So if we're lucky enough to find an 8'' woofer that can extend to about 2K, that would be good?
                  No matter where you go, there you are.
                  Website

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                  • #10
                    Re: 8'' two-way any reason why not?

                    Originally posted by Jed K. View Post
                    One reason to not use an 8" driver in a 2 way is the beaming at higher frequencies, but folks like Mark K, Linkwitz, Jon Marsh have had good results with tweeters that can cross low enough to eliminate most of the beaming problems associated with larger diameter midranges.

                    I've had my eye on the Seas Excel 8" nextel woofer for something like this. Looks like it is very extended in the lower treble.
                    I'd say that MOST DIY beginners, without too much to compare to, will find an 8" 2-way (like the Noah 8 in the Showcase) very easy to enjoy. I built something like them 8 years ago, and still enjoy listening to them 8 years (and about 16 speaker projects) later.

                    Chris

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                    • #11
                      Re: 8'' two-way any reason why not?

                      Gowa, there are a lot of 8" drivers that extend to 2k, that isn't the problem. It is what starts to happen before that point with an 8" driver that causes the problems.
                      Don't listen to me - I have not sold any $150,000 speakers.

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                      • #12
                        Re: 8'' two-way any reason why not?

                        Originally posted by gowa View Post
                        So if we're lucky enough to find an 8'' woofer that can extend to about 2K, that would be good?
                        It will work but I'd look for something more extended than that even if crossing around 1.5-1.7k. It'll help you hit your acoustic slope targets and give you more room to shape the FR- along with a better off axis response.

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                        • #13
                          Re: 8'' two-way any reason why not?

                          I did a very nice sounding 2-way with the 27tdfc tweeter and the peerless 8" nomex, but the executive series would be even better: http://www.madisound.com/catalog/pro...oducts_id=1605

                          likes a big box though, I went with about 1.7cf ported for the nomex. Crossed 1500hz with a 4th order electrical gaussian filter (likely 6th order acoustic).

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                          • #14
                            Re: 8'' two-way any reason why not?

                            Originally posted by Jed K. View Post
                            It will work but I'd look for something more extended than that even if crossing around 1.5-1.7k. It'll help you hit your acoustic slope targets and give you more room to shape the FR- along with a better off axis response.
                            This was my idea with the drivers listed in my post; cross the thing over around 1.6kHz.

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                            • #15
                              Re: 8'' two-way any reason why not?

                              Somehow, I have a particular fondness of 8" drivers. There is something just "right" about them. My first speaker design used a generic 8" driver and a Philips tweeter. Crossover was at 2.7kHz. Although this is nowhere near where one "should" cross them over, it turned out to be a success. Had I known then what I know now, I probably would not have attempted to do it, and that speaker would not exist.

                              As previous posters have indicated, there are tweeters commonly available that can cross low. IIRC, the LDSG suggests that a 1200Hz crossover is right for an 8". A more modern approach is to use a waveguide on the tweeter. I don't claim any significant knowledge of waveguides but, if I understand correctly, it helps to match the radiating area more closely to that of the woofer. It also has the advantage of bringing the acoustic centres of the two drivers into closer alignment, as the tweeter will be displaced rearwards by the waveguide.
                              Last edited by Shonver; 11-28-2008, 08:12 AM. Reason: Gra' ma

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