cdwitmer said:
Hi Chris, Very nice boxes , Teramoto got there... Mr O's cabinet will be narrower and deep due to WAF, will check with him if he wants to revert back to the orginal dimension.
Will source out some of those switches and connectors... the switch to change the power supply polarity is very cool...
The pdf. would be useful so we've got the vent dimensions & it's location & that of the driver. FWIW, at first glance, I'd expect a peak at cut-off (with the D9nf at any rate).
The difference between a BR and an MLTL? Simple: a bass reflex enclosure assumes a uniform air-particle density within the cabinet and no standing waves of any kind. A specific air-volume is utilised as a spring connecting the rear of the diaphram to a mass of air in a port.
Converely, a Mass Loaded Transmission Line (more accurately described as a Mass Loaded Quarter Wave Resonator) deliberately generates quarter-wavelength standing waves, which are then resistively loaded via the air-mass in the restricted terminus area.
The transition from one form of loading to the other is often thought of as a grey area but it's not really. The transition occurs at the point where the standing waves generated by the cabinet start to affect the response in a manner which requires the box to be re-tuned to account for this loading. Some people get confused, because both are boxes with ports 'so they must be reflex cabinets' but it's easy to illustrating the difference: here's the FR of an MLTL for the Fostex FE167E, tuned, as you can see, to 40Hz.
The difference between a BR and an MLTL? Simple: a bass reflex enclosure assumes a uniform air-particle density within the cabinet and no standing waves of any kind. A specific air-volume is utilised as a spring connecting the rear of the diaphram to a mass of air in a port.
Converely, a Mass Loaded Transmission Line (more accurately described as a Mass Loaded Quarter Wave Resonator) deliberately generates quarter-wavelength standing waves, which are then resistively loaded via the air-mass in the restricted terminus area.
The transition from one form of loading to the other is often thought of as a grey area but it's not really. The transition occurs at the point where the standing waves generated by the cabinet start to affect the response in a manner which requires the box to be re-tuned to account for this loading. Some people get confused, because both are boxes with ports 'so they must be reflex cabinets' but it's easy to illustrating the difference: here's the FR of an MLTL for the Fostex FE167E, tuned, as you can see, to 40Hz.
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I'm assuming from that drawing that the panels are 18mm, with the front baffle doubled? It's certainly more akin to an MLTL than a BR. In fact, given the slight taper, it's technically an ML TQWT.
If my dimension assumptions are correct, then This is the anechoic FR of that cabinet, without any damping, using the D9nf, which is pretty much what I expected.
If my dimension assumptions are correct, then This is the anechoic FR of that cabinet, without any damping, using the D9nf, which is pretty much what I expected.
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Adding 0.35 lbs ft^3 of damping to the top 23in of the line does this:
Frankly, it's not a balance I would recommend. Especially when room-gain is factored in, things can very easily go pear-shaped with this sort of alignment, even with very careful amplifier-matching & positioning. Like a lot of people, I find speakers with a peak at cut-off entertaining in the short term, but rather tiring to listen to over an extended period.
Suggestion: a) make sure the box is either lined, or has some stuffing added. As-is, it's underdamped. And b) staple a thin layer of felt over the inside of the port & adjust the thickness to taste. You'll get a smoother response & it will take down that peak at Fp. Immediate reaction will probably be something in the nature of 'it doesn't sound as "free" ' or similar, but it'll be a whole lot more balanced & easy to listen to in the long term.
Frankly, it's not a balance I would recommend. Especially when room-gain is factored in, things can very easily go pear-shaped with this sort of alignment, even with very careful amplifier-matching & positioning. Like a lot of people, I find speakers with a peak at cut-off entertaining in the short term, but rather tiring to listen to over an extended period.
Suggestion: a) make sure the box is either lined, or has some stuffing added. As-is, it's underdamped. And b) staple a thin layer of felt over the inside of the port & adjust the thickness to taste. You'll get a smoother response & it will take down that peak at Fp. Immediate reaction will probably be something in the nature of 'it doesn't sound as "free" ' or similar, but it'll be a whole lot more balanced & easy to listen to in the long term.
Attachments
Like a BIB the sim looks like it is screaming out for a helpful room factor ... but with little to load it probably won't get it.
On the face of it, this box gives one to think that the speaker is excelling because it is just that good, and in spite of an unhelpful enclosure. The one thing going for it is that any walls are fairly far off from the driver, reducing reflection. It would be interesting -- and a good source for some valuable data -- to see what would happen if one made the port aperiodic.
dave
On the face of it, this box gives one to think that the speaker is excelling because it is just that good, and in spite of an unhelpful enclosure. The one thing going for it is that any walls are fairly far off from the driver, reducing reflection. It would be interesting -- and a good source for some valuable data -- to see what would happen if one made the port aperiodic.
dave
I think the various comments about the new enclosures likely have a lot of merit, but a few clarifications to keep in mind --
1) Mr. Teramoto has not actually tried these enclosures yet with the D9nf, but only with the D9e field coil driver which is likely more highly damped than the D9nf. (My apologies about referring to it as an enclosure for all types of 9-inch Feastrex drivers -- that was my assumption.) He also uses some insulation devices inside the cabinet made of washi paper.
2) Even the measurement data on the D9nf is suspect in that the measurement device (Woofer Tester II) may or may not have been set up properly . . . so there are a lot of "ifs" involved.
I guess I need to apologize for being less than precise with the content of some of my posts here, possibly sending people down some rabbit trails.
That said, I think Joe's (Talawalla's) comment above is correct. It is a testimony to something extraordinary about these drivers that they have the power to reach out and grab you regardless of what enclosure they're used with . . .
-- Chris
1) Mr. Teramoto has not actually tried these enclosures yet with the D9nf, but only with the D9e field coil driver which is likely more highly damped than the D9nf. (My apologies about referring to it as an enclosure for all types of 9-inch Feastrex drivers -- that was my assumption.) He also uses some insulation devices inside the cabinet made of washi paper.
2) Even the measurement data on the D9nf is suspect in that the measurement device (Woofer Tester II) may or may not have been set up properly . . . so there are a lot of "ifs" involved.
I guess I need to apologize for being less than precise with the content of some of my posts here, possibly sending people down some rabbit trails.
That said, I think Joe's (Talawalla's) comment above is correct. It is a testimony to something extraordinary about these drivers that they have the power to reach out and grab you regardless of what enclosure they're used with . . .
-- Chris
D9nf cabinet
This thread has off and on addressed the idea of a cabinet design for the D9nf. I wonder if I could get feedback from any of the design heavies on this board for this admittedly simple idea for that driver.
Thinking wider and shallower here, I have in mind a straightforward BR cabinet that measures in inches 27 x 14 x 10.5 hwd. Using 18mm BBirch, the interior volume would come in at around 47 liters, a mid-point of sorts between the ShadowBox Scottmoose offered very early in this thread and the recently posted Teramoto floorstander.
The driver's center would measure 8 inches down from cabinet top.
For the port, a 2-inch dia. x 5-inch (?) tube mounted 4 inches on center from bottom rear of cabinet. I'm really winging it here. There's undoubtedly an optimal spec, but I'm not sure how to derive it. I tried working with some formulas in Dickason's design book, but couldn't find all the values called for.
My overall idea is a KISS design that gets some room reinforcement in the bass with the rear porting and placement near the room boundaries. The wide baffle should also help with the mid-bass and midrange wavefronts. Of course the cabinets would be stand-mounted to bring the driver to an appropriate level for listening while seated. Mass-loading of the stands will help solidify the musical foundation as well.
Any opinions out there as to whether this looks like (the beginning of) a workable design?
This thread has off and on addressed the idea of a cabinet design for the D9nf. I wonder if I could get feedback from any of the design heavies on this board for this admittedly simple idea for that driver.
Thinking wider and shallower here, I have in mind a straightforward BR cabinet that measures in inches 27 x 14 x 10.5 hwd. Using 18mm BBirch, the interior volume would come in at around 47 liters, a mid-point of sorts between the ShadowBox Scottmoose offered very early in this thread and the recently posted Teramoto floorstander.
The driver's center would measure 8 inches down from cabinet top.
For the port, a 2-inch dia. x 5-inch (?) tube mounted 4 inches on center from bottom rear of cabinet. I'm really winging it here. There's undoubtedly an optimal spec, but I'm not sure how to derive it. I tried working with some formulas in Dickason's design book, but couldn't find all the values called for.
My overall idea is a KISS design that gets some room reinforcement in the bass with the rear porting and placement near the room boundaries. The wide baffle should also help with the mid-bass and midrange wavefronts. Of course the cabinets would be stand-mounted to bring the driver to an appropriate level for listening while seated. Mass-loading of the stands will help solidify the musical foundation as well.
Any opinions out there as to whether this looks like (the beginning of) a workable design?
I agree with Scott. At the same time, I have repeatedly confirmed that it is really hard to make the Feastrex drivers sound bad. In fact, that is part of the problem, because they sound so good in whatever you put them in that you think the enclosure must be correct. Well, yes it is certainly correct insofar as you can listen to it day in and day out very happily. But chances are good that it could be better. I may have mentioned this before but I actually attended a demonstration in Japan where a VAR put Feastrex D5nf drivers in some rearloaded horn enclosures that I thought were really a horrid match for the drivers. I was familiar with the drivers sounding much better in Feastrex's original triple-ported enclosure of about 30 liters volume. Yet that VAR got two orders for the D5nf drivers at that demonstration. I wasn't sure whether to be happy or sad . . . I think the day is not far off when a consensus will emerge that certain enclosures are [close to] ideal for particular Feastrex drivers. That will follow upon cut-and-try experiments starting from solid, established theories of enclosure design using proper measurements of the drivers.
I *suspect* that in the case of the 5-inch drivers, the various manifestations of the current Feastrex 47 liter enclosure are homing in on one ideal, but that is simply because they have been around for a few months and have been so well received by so many people.
It's quite obvious to me that there are still very many outstanding enclosure concepts for Feastrex drivers waiting for someone to conceive and realize them. 2008 will be an exciting year for Feastrex fans.
Many thanks to Scott, Dave, Greg, Martin and others for their truly heroic efforts on behalf of Feastrex fans, and to the intrepid DIYers who have been willing to be early adopters (read: guinea pigs for science). Thanks to you all 2007 has been a great year and 2008 stands to be even better!
-- Chris
I *suspect* that in the case of the 5-inch drivers, the various manifestations of the current Feastrex 47 liter enclosure are homing in on one ideal, but that is simply because they have been around for a few months and have been so well received by so many people.
It's quite obvious to me that there are still very many outstanding enclosure concepts for Feastrex drivers waiting for someone to conceive and realize them. 2008 will be an exciting year for Feastrex fans.
Many thanks to Scott, Dave, Greg, Martin and others for their truly heroic efforts on behalf of Feastrex fans, and to the intrepid DIYers who have been willing to be early adopters (read: guinea pigs for science). Thanks to you all 2007 has been a great year and 2008 stands to be even better!
-- Chris
If I could afford these drivers I'd never put them in a BR box, and I'd try to use the best enclosure possible worthy of their design and cost. BR cabs are everywhere just walk into the local big box store..How about utilizing them with the Feastrex Passive or some other method of loading...
Anyhow I'm not a speaker cab designer and only know basic math but I know I've never been really impressed with anything BR..
Wishing Feastrex a very successful 2008 and much prosperity.. Dave
Anyhow I'm not a speaker cab designer and only know basic math but I know I've never been really impressed with anything BR..
Wishing Feastrex a very successful 2008 and much prosperity.. Dave
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