The reflex part of the box is a Helmholtz resonator, so cab tuning [Fb] for a given net volume [Vb], vent area [Av] and length [Lv] should be the same regardless of the driver's specs.
11 ft^3 net with a 60"^2 x 0.625" vent = ~41 Hz
GM
- - - Updated - - -
This is to critically damp the vent, i.e. remove any 'ringing', so if any damping of consequence is required such as packing with straws, stuffing or similar, then box tuning [Fb] will go down in both frequency and amplitude, sometimes enough to require enlarging the port and starting over, though to date this hasn't happened with the MLTL alignments I recommend.Originally Posted by LowOhms
Efficiency only drops in the driver's acceleration passband below its ~2*Fs/Qts' mass corner, so with these compound alignment cabs the lower end of the horn's output can be rolled off too, particularly when the cab is tuned down to the driver's Fs.
Qts' = Qts + any added series resistance: mh-audio.nl - Home
From this we see that to keep overall efficiency up and/or ~tonally flat depending on what the added resistance consists of, then a high Qts' is desirable to lower the mass corner below ~150 Hz for the 825/828 series.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
This is why they make narrow directivity [long] horns......... Some folks extend, angle forward baffle 'wings' to accomplish it and I and a few others 'cheated' a bit by adding [trail pad] foam horn extenders to damp off axis response in both planes. Beyond ugly, but effective, and one reason why I corner loaded with a ~floor/ceiling grill to hide it all.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
I always enjoy your posts. We are not talking about lengthening horns, adding wings, or corner loading in Uncle Stu's Pool Table tweak. Rather, GM, we are addressing the interactions between ANY two speakers, Left-Right, when sound waves collide between them. This causes an aural confusion, which Uncle Stu addressed 20 plus years ago, with his deflectors idea.
If you a carefully read his entire thread from AA ( Audio Asylum, Tweakers Forum) which I referenced to in my initial post in this thread, you will be able to wrap your mind around what he is accomplishing, or trying to accomplish....even if we may not fully concur with his proposed reasoning.
I liked DryGinger's implementation in that thread.
One thing I know is, I TRYED it with cardboard boxes, stacked high ( 8 feet ) pointed as a " Vee" into my listening area, blocking the line of sight between the drivers and horns, and it SURPRISED me as to the effect. It was better to hear, less audible confusion, more coherency. It benefited the midrange IMHO, where we are so perceptive in our hearing as we age.
Check out that AA thread GM.
Jeff Medwin....Low Ohms
It's exactly the same in practice to a greater or lesser degree depending on whether one uses narrow directivity horns or just foam ones. If you're going to 'talk down' to someone at least know what you're talking about.
As for dividers, there were folks playing with room dividers that bisected rooms right up to the center of the listener's face when I got serious about learning this stuff in the early '60s, it was just one of a host of 'crazy' tweaks folks were trying to get the new fangled stereo to sound at least as good as their mono systems.
Anyway, to each his own, I prefer discrete three channel high directivity horn systems for 'best' overall 'stereo' same as the pioneers conceived it.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
So the idea behind this is to attempt to turn your speakers into a big ass set of headphones?
My setup presents a very nice center image.
I honestly don't hear speakers. I hear a sound stage that has width and depth.
Not sure why I would want to mess with that.
I honestly think you would do better by controlling room reflections and finding the best sweet spot to sit in.
At any rate, my equipment sits where your proposed divider would go and I'm not interested in moving it. There is a certain visual appeal that goes along with our hobby as well.
BTW, deadening the wall behind the center of the speakers works. See my avatar.
My thoughts
Ron
Enjoying Altec Speakers since 1972
LOL, my thoughts are, you need to stack boxes, about 8 feet high between the speakers, and actually TRY it on a temporary basis. Why ?? -- because the sound waves are colliding still in the middle with your rig, adding CONFUSION and a lack of focus, The rear of DryGinger's panel is absorptive, for rear wall reflections, but the front of the panels deflect, and, unlike your rear absorption material alone - STOP the negative interaction.
My comment : Its impossible to comment / judge what you THINK Uncle Stu's Pool Table Tweak will accurately do, until you try it, hear it, experience it. I was pleasantly surprised. If equipment is in the middle, as it is on mine, the permanent solution becomes a defector panel on either side of the equipment rack. Absorptive rear, reflective front, blocking line of sight between the horns and drivers. DryGinger's implementation.
Don't mentally dismiss things new, without trying it with your ears. I most-respectfully say !!
Jeff Medwin ... Low Ohms
The way I understand it, folks were trying to create a binaural playback from a stereo recording as opposed to starting with a binaural recording for headphones, which I was told at the time would sound horrible through a stereo system without more EQ than amp tone controls of day could offset. Today, with near infinite EQ control and cheap high power systems it may be the core programming for how they process multi-channel, Atmos movie playback for all I know.
Yeah, if you're hearing individual speakers, then you've got room acoustics problems, so greater directivity is one way to ameliorate a great deal of it as we ideally want zero room reflections between the speaker and listening position [LP] and anywhere in the room for surround sound.
For stereo, a diffuse soundfield behind the LP to decay away all the late arriving reflections adds spaciousness.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
Bookmarks