Hi everyone I am thinking of building some MLTL cabinets using 2 drivers in each cabinet.
I have seen the post where 3 different height designs are shown with different cut offs for single driver cabinets. I note that for a single driver the CSA is 56 sq. ins and that it should be 112 sq ins for a dual design.
This seems somewhat large as I have seen a commercial design with 2 Eikona drivers which had a smaller CSA but was taller and still had -3db at 29db.
Any suggetions.
I have seen the post where 3 different height designs are shown with different cut offs for single driver cabinets. I note that for a single driver the CSA is 56 sq. ins and that it should be 112 sq ins for a dual design.
This seems somewhat large as I have seen a commercial design with 2 Eikona drivers which had a smaller CSA but was taller and still had -3db at 29db.
Any suggetions.
AFAIK, doubling the CSA - and Vb by extension - as well as adjusting the vent dimension to keep Fb constant, should indeed be your main concern with regards to LF performance.
That manufacturer's claim for a smaller Vb might be true, but we don't know everything about the design to call BS or not. If true, something else was traded-off to achieve this, likely mid/upper-band sensitivity.
That manufacturer's claim for a smaller Vb might be true, but we don't know everything about the design to call BS or not. If true, something else was traded-off to achieve this, likely mid/upper-band sensitivity.
Always as close together as possible. Usually vertical positioning has fewer problems. We're less suseptible to lobing in the vertical axis than the horizontal. Unless we're lying down. In mid air. Or you're one of the few people with ears on the top & bottom of your head rather than on the sides. 
Yeah, IME, Altec pushed horizontal driver layouts to the limit with its 9844 studio monitor's 800 Hz/2nd order XO, so not really viable with 'FR' drivers unless vertical space is at a premium and one will be rolled off to create an acoustic baffle step loss filter: https://c1.staticflickr.com/3/2699/4402289233_3b8615fcb2.jpg
GM
GM
Ok understand but as I now have one driver below the other if I stuff the box the same as the original design by Jim Griffin my stuffing goes further down and therefore I will have a lot more stuffing.
Will that cause a problem.
Don't forget the internal height is the same as the original design but I have doubled the csa and 2 drivers go lower down the front.
Will that cause a problem.
Don't forget the internal height is the same as the original design but I have doubled the csa and 2 drivers go lower down the front.
More than double as one driver is below the other.
Instead of csa 56 ins and stuffing down to 10 ins from the top it is 112 ins csa and stuffing down to about 15 ins which is half way.Will this overdamp or should I reduce the density to compensate.
I am assuming that it is best to have one driver below the other.
You're damping the pipe & its modes. The nominal Zd becomes the centreline point between the closely spaced driver pair. The volume quantity & position of the stuffing remains unaltered: it's relative to the pipe, not the drivers.
There are certain caveats to that, but those are primarily related to internal reflections, which are a separate matter to the longitudinal standing wave & its harmonics. For 'normal' QW pipes, where Vb is relatively modest for a given tuning I think GM & I both tend to favour lagging the internal surfaces with 1in acoustic fiberglass, SAE F10 felt or similar, rather than stuffing it. How many surfaces depends on how acoustically efficient the box is. A good starting point for boxes like this would be top, back & one sidewall. Possibly you might get a few more harmonics coming through, but you can always add more, & as a rule although people claim they want absolute accuracy, a bit of euphonic distortion tends to be preferred in practice.
No, it's not. Example: if a 1 ft^3 box needs 1 lb^3 of polyfil, then it needs 1 lb, ergo if the box is 2 ft^3 it takes 2 lbs.
If this box instead requires lining with [4] pcs of 1" thick OC 703 [my preference] 12" x 12", then use the equivalent area of [8] pcs for 2 ft^3, though of course they will need to be cut to fit the new wall sizes.
For 'FR' drivers, yes.
GM
There are certain caveats to that, but those are primarily related to internal reflections, which are a separate matter to the longitudinal standing wave & its harmonics.
For 'normal' QW pipes, where Vb is relatively modest for a given tuning I think GM & I both tend to favour lagging the internal surfaces with 1in acoustic fiberglass, SAE F10 felt or similar, rather than stuffing it.
How many surfaces depends on how acoustically efficient the box is. A good starting point for boxes like this would be top, back & one sidewall.
Possibly you might get a few more harmonics coming through, but you can always add more, & as a rule although people claim they want absolute accuracy, a bit of euphonic distortion tends to be preferred in practice.
Yeah, the larger dims lowers the cab's internal eigenmodes, but the damping required to quell its 1/4 W pipe resonances does a sufficient job on even the huge Altec cabs folks have built when using ~19 mm no void plywood and plenty of bracing to the point where one Italian gentleman not only didn't like the relatively light damping MJK's model predicted, but ultimately none at all.
Indeed, just about all the designs using his software that I got feedback on said they wound up pulling half or more out, so switched to only recommending "damp to 'taste'".
Right, the pioneers did little damping and only starting using more as marketing forced ever smaller cabs, cheaper made components, cabs.
I asked one of the Altec distributor's in-house system designers why the newer [late '70s] A7 VoTT were so flimsy, 'loose' to the point of kind of 'wheezing', which he referred to as 'breathing'; he of course said cost, but it was also a way of dealing with the then rapid increase in amp power, EQ folks were hooking up to these once high power, but now 'low' power speakers and since then as now, SPL levels are often set based on audible distortion, the cab leaks away acoustic efficiency when over driven plus raises the cab's tuning to help offset the mid-bass loss due to thermal power compression. 'Dumb like foxes', these pros of yesteryear didn't miss a trick!
GM
I would love to hear a pair of Eikona 2’s to see what Jordan drivers are all about but at $475/pair not including shipping and duties is just prohibitive. Seriously, for 4in class drivers? Aluminum cone - I am wondering if a Fountek FR135EX might be something to consider for a lot less?
https://www.parts-express.com/pedocs/specs/296-723-fountek-fr135ex-specifications.PDF
https://www.parts-express.com/pedocs/specs/296-723-fountek-fr135ex-specifications.PDF
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How are you handling the +7.5dB 10kHz peak? I think an impulse response would show a clear ringing response with a 10kHz (100usec period) oscillation. A tizzy sound perhaps? But maybe that’s why they are angled 90deg with a deflector plate as shown on website.
I have about 40 pairs of full range drivers. The most expensive ones are the ScanSpeak 10F, Visaton B80, and PRV 5MR450NDY. All in the $100 range. The others are $15 to $50 range but I have many. So maybe one only has to buy 1 set, but hard to justify for a cheapskate like me.
I have about 40 pairs of full range drivers. The most expensive ones are the ScanSpeak 10F, Visaton B80, and PRV 5MR450NDY. All in the $100 range. The others are $15 to $50 range but I have many. So maybe one only has to buy 1 set, but hard to justify for a cheapskate like me.
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You are looking at the aurora, no idea what that's all about. I listen off axis, I did a lot of experimenting, they are definitely best that way, have heard it said they are designed specifically to be listened to that way. Eikona Order Info — Ars Harmonia
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