Fearless/full build question

[Matthijs]

Or follow coolhandji's advise and build one from Greenboy's endless list. That's by far the option with the best chance of a good endresult

 

[Follydude]

I hate to be a heretic but greenboy designs incorporate various trade offs in their design. The first question one should ask before re-engineering a design is why. Exactly what is the intended use and how and when does the existing design deviate from the desired goals. Therefore, before spending a bunch of time making a "better mousetrap" you need to decide how you are going to use the speaker. Is it a stage monitor, a PA speaker, a High-fi speaker? Where exactly are the ears positioned? What problem does changing the driver config / form factor solve? What do you lose?
At first glance, one thing to consider is that even if the changes are transparent (or possibly even an improvement), it may making stacking them highly undesirable because of both the form factor as well as how the drivers align.
Yet, if you are really interested in speaker design, it could be a good exercise to take a known design and making a modification to see how it changes outcome.

 

[Passinwind]

-The narrower cab will result in a shift of the small mid peak ( baffle step) to a higher frequency, and if you make the cab almost as narrow as the 15" there will be less of a peak. But the tradeoff here is that you'll have to take in account the stronger internal reflections from the side.

Yep, and if you go really narrow it becomes impossible to go with an asymmetric baffle alignment of the woofer in the lateral plane, which is yet another possible optimization of tradeoffs.

 

[Worldeeeter]

I've played a friends Fear type 115 3way a few times and really dig it but I'm not crazy about the form factor. So, just brainstorming here I thought about the possibility of reworking the size/shape but keeping the same internal volume and porting size making it more of a tower shape. So here's my question. Is there any technical reason that the cab couldn't be made much taller, narrower and possibly less deep. IF the internal volume and port size remains the same per the spec. This makes sense to me for a couple of reasons. Narrower makes it less bulky, shallower transfers to hight which gets the hi/mid speakers closer to ear level. And the porting would be the same physical size just reshaped. This makes sense to me on a practical level. Now tell me why it's not a good idea from a technical point of view. Or if it's a feasible possibility.

Thoughts?

This is how all new technology happens. Evolution!
You could be the next innovator in bass speaker cabs.

 

[HaphAsSard]

The narrower cab will result in a shift of the small mid peak ( baffle step) to a higher frequency, and if you make the cab almost as narrow as the 15" there will be less of a peak.

I took this passage from an old post by @Mark Reccord, quoted below, to mean something I'd already suspected, namely that a taller cab effectively moves the step down for a listener/player standing (with his/her ears) directly above the cab/stack, as opposed to a listener positioned to the side, for whom a narrower baffle (than a given one) results in a higher baffle step. Am I totally off? Casual googling didn't yield answers to this specific point, I guess because for audiophiliacs (), who normally sit in one place to enjoy their system on-axis, it's only the surface of the baffle that counts*, and establishes the position of the step in the passband, to be corrected with a notch filter or other means in the design phase.

stacking them vertically won't change anything in the horizontal plane (with respect to the baffle step) because the baffle size doesn't change in that direction anyway.

*(EDIT: yeah, right... - see below)

 

[Passinwind]

I took this passage from an old post by @Mark Reccord, quoted below, to mean something I'd already suspected, namely that a taller cab effectively moves the step down for a listener/player standing (with his/her ears) directly above the cab/stack, as opposed to a listener positioned to the side, for whom a narrower baffle (than a given one) results in a higher baffle step. Am I totally off? Casual googling didn't yield answers to this specific point, I guess because for audiophiliacs (), who normally sit in one place to enjoy their system on-axis, it's only the surface of the baffle that counts, and establishes the position of the step in the passband, to be corrected with a notch filter or other means in the design phase.

It's complicated: Invalid Link Removed

 

[HaphAsSard]

It's complicated: Invalid Link Removed

No kidding! Trying to make heads and tails of it now. Thanks for this and the True Audio link.

 

[Passinwind]

No kidding! Trying to make heads and tails of it now. Thanks for this and the True Audio link.

Have you ever looked at Duke's hi-fi cabs? He pays a lot of attention to this stuff, and has a much deeper understanding of it than I do,

 

[HaphAsSard]

Have you ever looked at Duke's hi-fi cabs? He pays a lot of attention to this stuff, and has a much deeper understanding of it than I do,

Eh, I guess it's not just solitary fellas alone in a room on a carefully positioned armchair after all... You do wanna invite friends sometimes!

 

[Bill Whitehurst]

If your main objective is getting the mid and horn
above a certain point, maybe all you really need is
a chair to sit the cab on.

 

[HaphAsSard]

It's complicated: Invalid Link Removed

I've given it a read. I do think I've - uh, intuitively - grasped how the shape of the baffle determines the shape of the phenomenon for an on-axis listener. Off-axis listening is mentioned in passing but not treated in any detail, unfortunately. (Probably because it would take a site-ful of writing.)

 

[Follydude]

I think the diffraction reaction is a bit over blown.The baffle is 19.5 inches wide for a 15 inch driver. We aren't talking a huge amount of ability to change the width without 'Tardis' like construction technology. Additionally, the crossover is likely to be well within the ballpark unless he dramatically changes the internal volume, port tuning, or driver selection. Maybe not perfect, but I doubt it would be audible. Yet, any significant change in cabinet dimensions, even keeping volume constant, will force a change in the port dimensions. Failure here would definitely change the speaker, and can be a challenging design element even for someone with experience.

 

[Passinwind]

I think the diffraction reaction is a bit over blown.The baffle is 19.5 inches wide for a 15 inch driver. We aren't talking a huge amount of ability to change the width without 'Tardis' like construction technology. Additionally, the crossover is likely to be well within the ballpark unless he dramatically changes the internal volume, port tuning, or driver selection. Maybe not perfect, but I doubt it would be audible. Yet, any significant change in cabinet dimensions, even keeping volume constant, will force a change in the port dimensions. Failure here would definitely change the speaker, and can be a challenging design element even for someone with experience.

Agreed for the most part, although the mind and eyes have a funny way of making things "audible." And at least some of us use (or used, in my case) these cabs for a lot more than just bass. Personally, I don't think there's enough to be gained by changing the plans to be all that worthwhile in any case. Hence my "white sheet" recommendation near the top of the thread. But since Kirk asked for specifics on the ramifications of a re-shape, and some guidelines on how far that could be stretched gracefully, I at least wanted to air out some of the minutiae. Dave spent a whole lot of hours sweating that stuff, believe me. But Dave's not here, so...

 

[Follydude]

Agreed for the most part, although the mind and eyes have a funny way of making things "audible." And at least some of us use (or used, in my case) these cabs for a lot more than just bass. Personally, I don't think there's enough to be gained by changing the plans to be all that worthwhile in any case. Hence my "white sheet" recommendation near the top of the thread. But since Kirk asked for specifics on the ramifications of a re-shape, and some guidelines on how far that could be stretched gracefully, I at least wanted to air out some of the minutiae. Dave spent a whole lot of hours sweating that stuff, believe me.

It's a really thoughtful, clever design. I agree that it doesn't seem worth the effort to redesign it just to stack the mid and tweeter but HaphasSard may feel otherwise. Again, I think the intended use/application should be the driving factor when designing anything. Why fix what isn't broken, "perfect is the enemy of good enough".

 

[HaphAsSard]

It's a really thoughtful, clever design. I agree that it doesn't seem worth the effort to redesign it just to stack the mid and tweeter but HaphasSard may feel otherwise.

Uh, I'm too much of a knucklehead to even have an opinion for or against! - re baffle-step and everything else. I've simply no idea of the full implications of such a redesign, whether keeping the crossover an invariant or attempting a tweak thereof. I do feel the OP as far as finding a slimmer cab desirable. In his shoes I'd probably feel up to the task or not depending on prior experience, disposition to research and time for trial and error.
It's being a fun thread anyway.

"perfect is the enemy of good enough".

And vice versa! J/K

 

[Follydude]

Uh, I'm too much of a knucklehead to even have an opinion for or against! - re baffle-step and everything else. I've simply no idea of the full implications of such a redesign, whether keeping the crossover an invariant or attempting a tweak thereof. I do feel the OP as far as finding a slimmer cab desirable. In his shoes I'd probably feel up to the task or not depending on prior experience, disposition to research and time for trial and error.
It's being a fun thread anyway.
And vice versa! J/K

Sorry, got you confused for the OP.

 

[Passinwind]

Uh, I'm too much of a knucklehead to even have an opinion for or against! - re baffle-step and everything else. I've simply no idea of the full implications of such a redesign, whether keeping the crossover an invariant or attempting a tweak thereof. I do feel the OP as far as finding a slimmer cab desirable. In his shoes I'd probably feel up to the task or not depending on prior experience, disposition to research and time for trial and error.
It's being a fun thread anyway.
And vice versa! J/K

I just so happen to have a couple of way overly heavy 115 cabs loaded with nice neo drivers and no less than five different top boxes kicking around here. I would still kind of like to be able to stack rack gear on my cabs without overhang though, so Kirk's wants and needs don't quite dovetail with mine. But I'm always up for kicking around DIY ideas and seeing what shakes out.

 

[CL400Peavey]

I've played a friends Fear type 115 3way a few times and really dig it but I'm not crazy about the form factor. So, just brainstorming here I thought about the possibility of reworking the size/shape but keeping the same internal volume and porting size making it more of a tower shape. So here's my question. Is there any technical reason that the cab couldn't be made much taller, narrower and possibly less deep. IF the internal volume and port size remains the same per the spec. This makes sense to me for a couple of reasons. Narrower makes it less bulky, shallower transfers to hight which gets the hi/mid speakers closer to ear level. And the porting would be the same physical size just reshaped. This makes sense to me on a practical level. Now tell me why it's not a good idea from a technical point of view. Or if it's a feasible possibility.

Thoughts?

I think this is kind of like going to a car dealership and wondering why you cant mix and match power trains, interiors, exterior styling points. Some things are possible to swap, some are not. Those that are, tend to already be laid out for the consumer. Other things, even if possible would drastically price themselves out of availability.

If you want a mid driver closer to your ear, there are several options.

• The best way is to stack two cabs together. This gets mids closer to your ear, and gives your volume over all
• You could alternatively raise a cab off the floor
• Dual woofer designs inherently have mid drivers elevated.

Take a look at the F215 wide and slim. What you are purposing is possible, but I dont think you will see as much change as you thing you will. One cab is taller and narrower, but both have similar depths. This is partly due to the fact that to accommodate the porting of both cabs, you can not shrink them too much front to back with out diminishing performance. The F215slim has the mid driver centered somewhere around 45" from the floor. The 1515/66 has a pair a little higher up even.

 

[MrLenny1]

Get 2 and stack them.

 

[Kirk Bryant]

A few things. Don't want a two cab solution, defeats the one cab deal, Don't want a two woofer solution, too heavy. Don't want a stand or chair solution. One more thing to haul or source on site. Not worried about stability if it's at least roughly 15"+ per side. Do not use racks anymore small Dclass head only. I don't schlepp through a house or over dogs etc. don't have house or dog, cab stays in truck 99% of the time except when it's on the gig. Don't care about vertical mid/tweet in particular it was just a thought. Was thinking the width of the shelf port that's on the side could be moved to the bottom increased in hight to compensate for change in width thereby increasing the overall hight. And possibly move the crossover which tend to by heavy down there to shift weight lower in the box. I'm not going to build a bunch of cabs to try out ideas. I'd also like to thank all the people who said just build a GB cab for playing the part of "Captain Obvious" I'd also like to thank Charlie "Passinwind" for being the voice of reason and an educator instead of just a commentator or common tater as it were. Also thanks to those who simply state the science without hyperbole. And thanks CL400Peavey but I'd never use a 215 and probably would not even need a 212. Which is why I've also been looking at the MAS112's as a possibility. I just want to explore this idea too. Thanks to all for your patience.