Hey Scott-
Was wondering do you think the vifa would have enough max spl in this application? Obviously if HPF'd it buys it some extra headroom, but that only goes so far. I'd like everything to be able to get up close to 120dB/1m for the sake of overhead.
Playing with a 7ft x 32" baffle in "the edge" does show there should be a pretty significant boost in that range, 6-10dB...if that is the case maybe a ~85dB woofer could get up there (x4). EDIT: the open baffle box was ticked, and now I realize the +6dB line is where the standard IEC baffle would be, so only a couple dB of gain there...
Tang Band W4-1337SDF as well as the faital 4fe32 also look pretty good as far as having higher sensitivity goes.
Was also eyeballing the dayton RS100-t and RS225's, they seem to have good value, would allow me to test this out without too much expense and seem to be rated well across the board. Visually that combo would be nice.
Thanks-
Was wondering do you think the vifa would have enough max spl in this application? Obviously if HPF'd it buys it some extra headroom, but that only goes so far. I'd like everything to be able to get up close to 120dB/1m for the sake of overhead.
Playing with a 7ft x 32" baffle in "the edge" does show there should be a pretty significant boost in that range, 6-10dB...if that is the case maybe a ~85dB woofer could get up there (x4). EDIT: the open baffle box was ticked, and now I realize the +6dB line is where the standard IEC baffle would be, so only a couple dB of gain there...
Tang Band W4-1337SDF as well as the faital 4fe32 also look pretty good as far as having higher sensitivity goes.
Was also eyeballing the dayton RS100-t and RS225's, they seem to have good value, would allow me to test this out without too much expense and seem to be rated well across the board. Visually that combo would be nice.
Thanks-
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You'll have to do the power modeling.
..excursion would be the real limitation.I can say though that the xmax is relatively comparable at 3mm for the Vifa when compared to most other offerings with similar a similar surface area.
The Vifa's HD is (at least above 370 Hz), as good or better than most.
The Vifa's CSD is actually better than most.. and it has a low mms.
It's also gotten good subjective reviews + it's inexpensive.
The RS100(varient) is better with distortion for everything except 2nd order in the mid.s.. so if you don't mind a bit more 2nd order distortion (and consequently higher THD), then it's a good option with a bit more excursion. It is however more than 3 times the price of the Vifa.
Really, so long as you only run the mid. line down to the 300-400 Hz range (before baffle loss) with a good steep high-pass, my guess is that this driver grouping (4 in a line) should at least work to 110 db in a linear fashion at your listening position. It's really only if you want to push the line even lower that you might have problems.
IF you want to run the mid. line lower in freq., then you should look at different drivers and/or adjust your spl needs. The next "bump" in Sd would be with 5-5.25" drivers.
The Tangband and the Faital Pro drivers have less xmax.. but a bit more Sd. Their added efficiency isn't really going to provide you with much (considering the lower eff. mid-bass grouping).
As for the Dayton 8".. it's a bit less efficient and the Qts is a bit lower (meaning less output as freq.s decrease near the average in a sealed enclosure).
..much closer to the quality of the compression driver while still retaining enough surface area for low excursion and resulting low distortion.
It's particularly beneficial in the context of monitoring (being closer to the loudspeaker) - with better lateral tracking from a narrow line of speakers (centered relative to the compression driver) rather than a single large diameter mid-bass, especially on a large baffle. In this context it would actually be preferable to have the line extend as low as 100 Hz.. but distortion would go way up (for the little 3.5"-4" drivers) with higher spl's. (..this is something I've personally experimented with, both "in-wall" and with larger baffles.)
As you move out from the loudspeakers, and as the loudspeaker's baffle narrows, it increasingly makes less difference.
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Why? Are you saying sound quality is proportional to the smallness of a driver's radiating area, all else equal?
Please explain this point - I am not sure what "lateral tracking" refers to.
Yes, with respect to radiation (polar intensity) over distance - particularly as you move closer to the diaphragm. As much or more though, it necessarily encompasses Mms - which is usually lower as driver size decreases. Lower mass = more detail (all else equal).
Lateral tracking: the ability to better locate images horizontally across the "sound stage".
Or you could just go with a single TD15M per side in a cardioid enclosure for simplicity's sake.
It won't be as "detailed" as my first suggestion.
About mms and detail, or the pressure gradient? (..or both?) ..and what led you to a different conclusion?
Both.
I'm hearing about this pressure gradient thing for the first time, so I can't believe it without further data, but a lot of people believe in the "less mass = more detail" relationship. So far, there have been no peer-reviewed studies that conclusively prove this, so I won't believe it either.
That's not disagreeing.
I also wouldn't advise *believing* it either.. rather use it as a point of examination through experimentation to make your own determination. (..hmm, lot's of "ation"s there.
) As a point of reference I should note that the mass/detail thing is relational to surface area - it's not strictly about Mms per se. (..Ex. you can tape pennies to a dust cap to increase Mms and it won't decrease detail unless the dust-cap is a substantial contributor to the bandwidth you are listening to.)I think Ryan's first experiment should be trying-out the midbass drivers he already has in a vertical line above the SEOS to see what it does or does not do for him.
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You'll have to do the power modeling.
I can say though that the xmax is relatively comparable at 3mm for the Vifa when compared to most other offerings with similar a similar surface area.
The Vifa's HD is (at least above 370 Hz), as good or better than most.
The Vifa's CSD is actually better than most.. and it has a low mms.
Right well the SEOS/951 combo really is excellent down to ~500, it seems kinda goofy to me to go to all the hassle of adding a 4th way to the system for it to only extend the directivity matching by 1/2 an octave or so.
Playing with modeling this a bit more, and the rs125t is looking like a good contender, 4 of them stacked vertically is actually a tad shorter than 2 8"s, and bringing my SPL requirement down to a more realistic ~114 in that range would allow them to play down to 150hz with a 8th order filter and be within safe excursion limits. I would like to be relatively free of driver compression with ~85dB playback and ~30dB crest factor, so this should do it.
Is there a way to model driver diameter vs baffle size vs off axis response? Also you mention this is all geared for closer listening, I do have other people in the room and would like the response to be good for them out to ~3m. Part of the goal of the big speakers is to create a reasonably good listening experience for more than just one person. Thanks-
Don't forget the pressure loss of about 4db below the baffle-step depending on distance. Still, you can carefully integrate that into the crossover design (..using that pressure loss in conjunction with the filter for your net slope). Of course enclosure volume will also dictate it's high-pass behavior. In this respect it's still very much an art, particularly in the lower midrange and factoring-in listener distance.
The better loudspeaker modeling programs can provide off-axis plots. I've not used it, but freeware Boxsim from Visaton mentions "Frequency response along the axis and in over 20 other directions". Axidriver should be able to provide a polar.
With what I previously described, listening further away isn't a problem. However, even though you've got a listening distance of almost 2 meters, you will likely want a little bit of control over gain of the midbass grouping to "dial-in" for distance. People listening further away may need a bit more gain for baffle-step loss than you need. (..It's another reason why it's easier to stick the filter a little higher around the region of baffle step loss.)
Note: with this design you should also try high shallower slopes on the SEOS to see if it does something you like. Not a lot higher mind you, but perhaps in the range of your 500 Hz (high order filter) and up to 850 Hz (lower order filter). Also look to different types of filters ie. LR is -6db vs Bessel with -3db.
A 15" driver with 14 mm one-way Xmax can give you 137 dB @ 1m full-space with a 150 Hz sine wave. I expect many 18" pro drivers to go up to 500 Hz without a hitch so there is even more headroom there.
A 4th order LR actually protects the driver more than an 8th order because the 4th order rolls off faster up to the crossover frequency. The 8th order has a steeper slope afterwards, but 24 dB/octave is more than enough to protect against the increasing excursion requirements.
Linkwitz-Riley Crossovers: A Primer
Baffle size affects the frequency at which full-space radiation transitions to half-space, and little else. http://www.trueaudio.com/st_diff1.htm Do the math. For the most part, driver diameter affects its off-axis response.
What is your actual dispersion requirement?
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I often have clients in the room, so thats part of the idea of having the constant directivity speaker. The more consistent it can sound say ~40 degrees out from center the better. The speakers are toed in @45 in the corners.
Where you say "Do the math. For the most part, driver diameter affects its off-axis response."-
Scott has an interesting point here in that this really isn't true for a 15 or an 18 under a 24" WG @500hz...at least not what I'm modeling 45 degrees in Jeff Bagby's baffle diffraction and boundary simulator; the woofer diameter would have to be much larger for this to matter/match at 500hz...It looks like a 24" driver would start to roll off @45 degrees about the same as the SEOS24 that they measured on AVS.
My understanding is this is why a pair of 12"s would match better (effectively a 24"er on the horizontal axis dispersion wise)?
In any case the SEOSR polar Scott posted does seem to bear this out in practice. You can clearly see a shelf at ~350, where the directivity does't match as well as it could.
Then again I'm also unable to model Scotts idea with the small vertical line array, but this program won't model more than one driver. Does anyone know how to do this in PCD? I feel like I read someplace that it is possible.
Or you could just go with a single TD15M per side in a cardioid enclosure for simplicity's sake.
I think it's a really good idea, except my speakers really need to be in the corners or very near them (not that much space), or actually built into the corner like they are now. I'm not sure how to provide good rear port access in that scenario, and the depth of the box with the ports would be relatively shallow.
Vertical array won't make a difference (within our context). Horizontal it can and will as freq.s increase - as a function of the driver, combing, and baffle.
To be fair.. +/-45 is generally where you start to see some pressure loss, though not a lot. +/-60 is usually close to the "starting point", and even in the 500-600 Hz range of the SEOSR it is (..maybe 55 Hz).
As a point of interest, try looking through polars of Earl's designs here:
Loudspeakers
There you have models with varying baffle widths, and driver sizes.
Then consider modeling the woofer portion and baffle within the modeling programs to see if there are differences.
Trying to find a smaller source driver 6.5" in this case on a baffle somewhat similar in width to what you want.. Sonus Faber Stradavari:
Sonus Faber Stradivari Homage loudspeaker Measurements | Stereophile.com
Even in the highest "support" region of about 600 Hz (fig. 5), it's still down about 6db at 90 degrees.
Again though, the best place to start is with what you already have: trying those midbass drivers in a vertical line (..and a quick mock-up with cardboard is usually cheap).
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