With such little excursion available, an alignment using a second order HP filter on the drivers will reduce Xmax to zero (eventually) below the tuning frequency. Otherwise, if Fb=80Hz there will be too much bass energy below tuning and the drivers will probably bottom out very easily. The same problem will happen with a sealed alignment unless you really limit the power input or use a highpass filter on the driver.
Possibly. On the other hand, the late Roger Russell's IDS25 array, running 25 x Vifa TG9 drivers per channel (2.55mm rated Xmax) in a sealed alignment nominally lurking around 1.1 or thereabouts, is equalised flat to roughly 30Hz, and I haven't heard of anybody bottoming out the drivers on it or any of the many clones (granted, I haven't been looking). I'm sure it will see rising LF distortion, but I haven't seen any complaints about that either, and since Roger himself (not exactly lacking experience with big speakers) preferred it over any of his McIntosh creations & there are measurements here of clones with the TD9 unit, it seems this isn't automatically an issue & presumably is going to depend on driver selection & usage. YMMV as always of course.
I have 24 TC9 sealed line arrays, a liter or so per driver, same 2.55mm xmax.
IME, the line needs to be high-passed around 100Hz, crossed over to a sub.
I can't imagine trying to use them to 30Hz.....that would only give about 95dB at xmax per pistoncalc.
And I do know the TC9's started talking back when I was playing around to see if the line was useable without a sub.
(Maybe I just play louder and am more demanding about uncompressed headroom than most...???)
IME, the line needs to be high-passed around 100Hz, crossed over to a sub.
I can't imagine trying to use them to 30Hz.....that would only give about 95dB at xmax per pistoncalc.
And I do know the TC9's started talking back when I was playing around to see if the line was useable without a sub.
(Maybe I just play louder and am more demanding about uncompressed headroom than most...???)
Here is one of @wesayso's 2 x 25 tc9 line array distorsion measurenents, equalized to 30 Hz.
Distortion rises, but not much more than any other speaker.
Not sure if the level (sligthly more than 80 dB) is normalized to 1m, however.
Also, I think these speakers are near the room corners, which helps for bass.
Wesayso in Post #849:
Another quote from wesayso's audio web site:
https://www.vandermill-audio.nl/do-it-yourself-sub-woofers/
Seriously: Roger replaced his XR290 (count me a fan too) with his IDS-25s -initially the prototypes & later the production model. http://www.roger-russell.com/columns/columns.htm#living
I'd usually take something like that with a grain of salt 😉 & assume commercial interest or similar. But a/ it was Roger, who didn't have much time for that sort of thing, and b/ he didn't create it as a commercial speaker -it was part of a two-article DIY project writeup for AudioXpress & only afterwards got snapped up for productionisation. I guess it simply gave him more of what he particularly valued.
Well, like any line array it's mostly a matter of how far away @ 'x'/'y' polar response and now we have tiny enough and near enough 'FR' drivers that combined with powerful enough digital correction at a reasonable price for it to work in relatively small rooms it seems reasonable that they could be quite good, but in a larger room that the 290 sounded best in, short of an MEH array it's as close to a live orchestra as I've experienced.
I’d certainly high pass them……the issue is where that needs to occur…….the LAST thing I want is a parallel line of woofers next to this….or behind it. BUT…..I’d be perfectly happy with a base module of two 12 or 15” woofers in a side to side coupled enclosure
Probably because you didn't take the food out of the refrigerator first!
Try them in a box of 1.5x Vas tuned to 60-70Hz.
Conventional wisdom would have you put them in a box of 3x VAS and tune to 58Hz, but you would have very low power handling.
Conventional wisdom would have you put them in a box of 3x VAS and tune to 58Hz, but you would have very low power handling.
Since your Vd is about 100cm3 max, I think you are right about that 100-ish Hz. But the ‘closely located’ part isn’t necessarily true. First, our ears aren’t very sensitive (I understate) for sound direction under 200Hz, second, under 200Hz you’re listening to the room, not to the speaker. Meaning that the sound field itself hardly is directional.
Only caveat is that your subs don’t do anything above 200Hz. No chuffing, no (harmonic) distortion and no driver noises. And that caveat can be tough.
If you look at the alignment I mentioned in post 39, it's a vented box with Fb=80 Hz for this driver. This frequency is perfect for crossing over to a sub and the HP is already built into the woofer section from the alignment's HP filter. Because the alignment is "quasi 5th order" the rolloff will be around 5th order, or 30dB/oct. You just add a sub with a matching 80Hz 5ht order crossover or use 4th order LR or Butterworth.
The whole concept behind that series of alignments is to design a reflex that has a bit of a peaking response and then use a filter to being the response near Fb back to flat. This reduces the required driver excursion at and especially below Fb, which is perfect for your drivers since Xmax is very low.
Personally, I would seal them and not look back. And then cross to the sub wherever is audibly proven to be needed, given desired SPL.
Although that said, you did say that the application needed response to 80Hz.
What's the application? Wondering since you have to use a sub anyway, for either 80Hz or 100Hz?
I get excited when I see someone willing to make lines with both planar tweeters and small mids.
I've always wanted to redo my 24 TC9 lines, adding a full length line of very small domes or planars/ribbons, next to the small mids.
Cost of the additional VHF line, and being head over heels into MEHs, has held me back so far.
What planar are you thinking about? Where would you cross it?
I resemble that remark!
Hi GM, Glad to hear that !! 😀
I've come to rank unclipped/uncompressed SPL throughout the entire spectrum, that includes room for say +18dB peaks over average SPL,
right below smooth frequency response.
I rank that at least even with if not above, polars, once the have no glaring errors.
Funny how it's both ends of the spectrum, lows and highs, where it's hardest to maintain linear headroom.
I’m torn between the GRS slim 8 planars and 32 Dayton ND20fb-4 3/4” domes……the domes have an incredibly flat response and off axis response that rivals a true ribbon…….i’d love to use true ribbons but too rich for my blood
Yeah, the GRS 8" slim has my eye too.
But not the 3/4" domes. They are going to be 1.5" c2c best, which I think is just too much distance for a good VHF line.