[brett]

i'll be starting my 4th set of pillars in the spring and i've got some ideas just a/b'ing some drivers lately, but wanted some expert advice.

regardless of what driver, i'm curious what happens as each additional driver in the array not only gets higher, but, especially on the driver side, what happens as each additional driver gets closer to the driver. the pillars in my malibu have a decent angle and i'm concerned about the proximity of the last driver to my ears.

one of the drivers i'm testing is this...

https://www.parts-express.com/dayton-audio-bmt25-4-balanced-mode-2-transducer-20w-4-ohm--295-236

they're not efficient at all, but they have a pretty decent sound to them on the bench and was wondering about putting 4 of them in each pillar s/p. i do plan on using a tweeter, so these will be only doing mid duty. i'd likely cross these at 250-300 as they seem to have excursion limits.

thoughts?

 

[Justin Zazzi]

If the array is slanted towards your ears significantly, like in an a-pillar, you won't be getting any of the benefits of a line array.

Why did you want to build a line array in your car? What problem are you trying to solve?

 

[brett]

well, i always like to try different things, even if they're considered taboo. but, more than anything i'm just trying to get louder than with one mid. i'm also considering putting a 5" in the corners, but that presents obvious problems. the 4"s that i've tried so far weren't getting as loud as i hoped, but granted i'll have at least twice the power going to them before.

also, i know it would require multiples, but my pockets aren't that deep.

 

[thehatedguy]

You'll have to delay each driver separately if you wanted to get the benefits of an array in your pillars so that each array "stands up" vertically.

 

[Patrick Bateman]

i'll be starting my 4th set of pillars in the spring and i've got some ideas just a/b'ing some drivers lately, but wanted some expert advice.

regardless of what driver, i'm curious what happens as each additional driver in the array not only gets higher, but, especially on the driver side, what happens as each additional driver gets closer to the driver. the pillars in my malibu have a decent angle and i'm concerned about the proximity of the last driver to my ears.

one of the drivers i'm testing is this...

https://www.parts-express.com/dayton-audio-bmt25-4-balanced-mode-2-transducer-20w-4-ohm--295-236

they're not efficient at all, but they have a pretty decent sound to them on the bench and was wondering about putting 4 of them in each pillar s/p. i do plan on using a tweeter, so these will be only doing mid duty. i'd likely cross these at 250-300 as they seem to have excursion limits.

thoughts?

I've been kinda obsessive about getting the mids and the tweets close together in my designs. Generally my designs feature setups where 60% of the sound in the car is radiation from a point in space that's the size of a golfball.

And one of the 'neat' things that I discovered was that differences of just an inch make a difference. IE, once you have everything radiating from such a small space, if you move one of the elements a single inch, the soundstage loses focus.

Due to that, the answer to your question is really going to depend on the frequencies involved. Are you trying to run your drivers to 20khz? If so, then YES, absolutely, you want the pathlengths to be EXACTLY the same. Even a difference of a single inch will make the soundstage lose focus.

OTOH, if you're only trying to cover one or two octaves, then the difference in pathlengths won't be an issue.

As Jason noted, if you're prepared to digitally delay each driver, and sit there with a mic and line up their impulse response, and you have amplification for each driver, then you can fix this with DSP. That might sound like a tough job, but with DSP selling for $20 a channel, and Parts Express selling amps that are $15 a channel, you could very well fix this electronically without breaking the bank.

 

[brett]

thanks, that's the type of response i was hoping for. essentially, they'll be playing from 250 to 2500, give or take. and, just from eye-balling it, the difference in pathlength (if i run 4 drivers, center to center) is appx 6". if i run tweets in the sail panels, do you think i could get away with that?

 

[Patrick Bateman]

thanks, that's the type of response i was hoping for. essentially, they'll be playing from 250 to 2500, give or take. and, just from eye-balling it, the difference in pathlength (if i run 4 drivers, center to center) is appx 6". if i run tweets in the sail panels, do you think i could get away with that?

Really depends on what your goals are. Guys like Gary Summers have a drop-dead soundstage, but their mids and tweets are within four inches of each other, *and* each channel is individually driven with DSP delay added into the mix to 'snap' the soundstage into focus.

Basically, if you have five sources and each one has a different pathlength, the sound from each is going to arrive at a different time*. And soundstaging and articulation depends on getting every source in sync; arrays can't do that.* Here's an example of what I mean: My father in-law has a set of line arrays in his home theater. And whenever we're watching a movie, we're always struggling to understand what the actors are saying. (This is because line arrays fail at articulation.*) But every once in a while we're blown out of our chairs by the dynamics, which is something that line arrays are very good at, due to lots of voice coils, high power handling, high efficiency, etc. Line arrays can blow you out of your chair.

Personally, I have a thing for articulation and soundstaging, which is why I go to these crazy extremes to get everything close to each other.

The main advantage of a line array is that it narrows the vertical directivity and increases power handling. But line arrays fall down on many other criteria, which is why I personally don't use them.

Different strokes, different folks, etc



* If you're clever with the DSP, you can make a line array behave like one big driver. This is the future, and not ALL line arrays are terrible. Just most of them The new L'Acoustic arrays are about as good as anything I've ever heard, and it will be real interesting to see where arrays are going. You can do things with arrays that can't be done with conventional loudspeakers.

 

[thehatedguy]

You are really going to need separate processing for each speaker to really pull it off right.

 

[ErinH]

I really don't understand why you want to use four of THOSE drivers? Much less four of any driver. If it's to make up for sensitivity then I'd focus on getting something that has higher sensitivity to begin with and using a pair. Then you can better align your CTC spacing of the tweeter which is most important.

Speaking of that... Did you look at the response of those drivers? There's nearly a 10dB bump above 2khz making it much, much harder to mate them to a tweeter.

So, what exactly is the reason for wanting that driver and four of them?

 

[Orion525iT]

I really don't understand why you want to use four of THOSE drivers? Much less four of any driver. If it's to make up for sensitivity then I'd focus on getting something that has higher sensitivity to begin with and using a pair. Then you can better align your CTC spacing of the tweeter which is most important.

This is a good question.

If I was considering something like this I think the OP should look at the TC series Tymphany drivers at PE. Sensitivity is better out of the box, inductance is super low, price is low. Willing to bet there is no better bang for the buck.

Another thing I am exploring, and it is something Patrick utilizes in a lot of his experiments, is a way to make a larger driver "appear" smaller. So you get the output and dynamics of a larger driver, but with the polar response of a much smaller one.

 

[Patrick Bateman]

This is a good question.

If I was considering something like this I think the OP should look at the TC series Tymphany drivers at PE. Sensitivity is better out of the box, inductance is super low, price is low. Willing to bet there is no better bang for the buck.

Another thing I am exploring, and it is something Patrick utilizes in a lot of his experiments, is a way to make a larger driver "appear" smaller. So you get the output and dynamics of a larger driver, but with the polar response of a much smaller one.

Yeah that's a good point. When I array four midranges, the efficiency and power handling is so high, my subwoofer becomes the weakest link.

 

[Patrick Bateman]

This is a good question.

If I was considering something like this I think the OP should look at the TC series Tymphany drivers at PE. Sensitivity is better out of the box, inductance is super low, price is low. Willing to bet there is no better bang for the buck.

Another thing I am exploring, and it is something Patrick utilizes in a lot of his experiments, is a way to make a larger driver "appear" smaller. So you get the output and dynamics of a larger driver, but with the polar response of a much smaller one.

I've heard some of the big BMRs, and there's something special about them.

I have no idea if all of them are as good, but some of them are really nice.

I haven't measured them, but I'm wondering if it has something to do with the cone shape. TangBand sells a driver with a flat diaphragm, and it sounds a lot like the BMRs. So there might be something to that flat shape.

There's a user over at diyaudio who likes them a lot too. But barely anyone seems to use them, because they DO have some weird looking specs and response.

 

[ErinH]

OP, what is your size limit (width and height)? Where is your planned location for tweeter (distance from planned midrange placement)? What is your budget for the whole shebang?

Another round of questions:
Why did you choose those mids?
Why do you want (4)?


I can think of a lot of options off the top that would probably do what you need and none involve the driver you are looking at. The FR is just not good. Too much work to mate a tweeter to it; and that bump above 2khz is going to cause you headaches, as I mentioned earlier.


As for your plans, let's just assume the driver # and selection was sufficient... as others have asked, the bandpass is key. Lobing starts as low as 1/4 wave, CTC (center to center) spacing between two drivers. So, if you wanted the (4) drivers to behave as one, let's say the distance between the top and bottom is a vertical 6" (I'm avoiding pythagorean theorum for the time being because 6" is enough to prove the point), lobing will cause you issues above 562 using 1/4 wave. Above 1100hz using 1/2 wave. So, as you can see, even in the best case scenario, you have lobing issues at 1100hz with quad 2" drivers. This is well before most any tweeter will come in to play. So, beyond the concern of using DSP to line everything up in time and amplitude, the physical geometry doesn't really support using a vertically stacked array of (4) 2" drivers in an ideal case. Not unless you have a really, really good tweeter. It just seems like a bad idea to me, TBH. I think you're wasting your time and efforts going down this road when other, simpler options work better.

If you knock that down to a pair of 2" drivers and can get ctc down to 4" (not likely to happen given most driver flanges) you are good to about 3300hz [(13500in/s)/(2in)/2]. And that's again a best case. But, that's enough to bring in a good tweeter in terms of mechanical capability (not including the potential concern with the distance from the mids to the tweeter). There are some really nice 3" mid options with relatively high efficiency, such as the Faital Pro 3fe22 8ohm that could be wired in parallel, giving you a total SPL of 97dB @ 1w/1m. With their reduced flange size you can get half-wave lobing down to 2.1khz, which is enough wiggle room to cross a touch higher with a good tweeter to cover 2.5khz-3khz and above (depending on the final acoustic crossover).

If you need a 2" driver, then something *like* this would probably do the job well:
Vifa TC6FC00-04 2" Full Range Paper Cone Woofer 4 Ohm

There are a lot of options in the 2-3" range, though, that will meet your needs of a simple, mid-to-high efficiency MIDRANGE. MIDRANGE is key; if you get caught up looking at fullrange drivers or the like you'll wind up trading excursion for sensitivity in most cases which is not what you need. I'd be targeting 500-3khz in the 2" variety because obviously excursion is going to be limited and lobing is going to mitigate any need to go above the ~ 3khz crossover region.

I don't know if you chose those Vifa's due to size limitations, 4-2" mids is at least 8" tall... so I'd assume width is the problem with anything wider? Still, I think if you looked around you'll find a single driver that provides the efficiency you need in the bandpass you need. While you may get a higher beaming point with a smaller driver, you have to worry about CTC spacing and by the time you account for that, you're often no better off than where you were with a good single driver.

 

[Ultimateherts]

If you need a 2" driver, then something *like* this would probably do the job well:
Vifa TC6FC00-04 2" Full Range Paper Cone Woofer 4 Ohm

The sensitivity on that driver is low considering what he is wanting to accomplish. Though in multiples it would be fine.

 

[ErinH]

The sensitivity on that driver is low considering what he is wanting to accomplish. Though in multiples it would be fine.

I realize that. Even still, that's about 86dB at 2.83v/1m. Two of them would put him at a typical sensitivity, though, and still fall in the 2" category. As I also said, there are many other options. That was just the first one I came across that would do the job as part of a dual 2" mid setup.

Anyway, the point of my reply wasn't to suggest a particular driver. Just to discuss the impact of his design idea and provide alternatives.

 

[2010hummerguy]

Buy a vehicle with vertical A-pillars. Hummer, Jeep Commander, VW Vanagon, etc. Profit!

 

[Orion525iT]

Buy a vehicle with vertical A-pillars. Hummer, Jeep Commander, VW Vanagon, etc. Profit!

Cheater!

Really, just because your pillars slope a certain way does not mean you have to build the array to match. However, most modern cars have an acute A-pillar angle in any case; just a side effect of better aerodynamics and increased cabin rigidity over the years.

And I have mentioned this before in other threads, but if you limit yourself to 2 driver arrays, the issues with arrays become much easier to solve. You can position the arrays so that the peak reaches your ear at the listening position. Combing is still present, of course, but you are at the position of summation. Once you go beyond 2 drivers, things get tricky.

Also, keep in mind that there is all sorts of combing, summing and interference patterns going on simply due to the environment. That is not going to be dealt with easily, and the problems compound with dash and pillar installs.

So I see combing as less of an issue if only two drivers are utilized, but installation and position is key. And you have to be certain that you can't get to the same place with a single driver.

 

[brett]

again, i want to thank you guys for the help/input. but, as i have to admit that combing/lobing are things i haven't quite grasped yet, so i apologize.

well, regarding why i chose those drivers.... like you guys, i tend to buy things just because, and these were part of that addiction. well, my current pillars housed these...

FaitalPRO 4FE35 4" Professional Full-Range Woofer 4 Ohm

after some trimming of the tabs, i got these fitted and playing full range. i had/have every intention of running tweets. i had been running the vifa xt25, but found it to be a little harsh in the 8-10k region for my ears, so i have a pair of seas 27 ready to go, fairly on axis, in my sail panels. the faitals were actually really good running full range, but just didn't quite completely satisfy; felt forced. also, and i feel this is a huge culprit, my power source was likely anemic. i had a massive nx4 bridged to each one crossed at 200, but ran into excursion issues, so ended up raising that to about 400 and it actually blended much better to my midbass (morel h8.1). but it lacked volume. no matter how i tuned it, i just couldn't get it to play as loud as i needed.

well, fast forward to now, and i've sold all my amps and replaced them with kenwood xr series. my intention is to run a xr-4s bridged to mid/tweet, using a passive crossover in between. so, that should get me something close to 300w per channel. now that i've upgraded the power, i feel a need to change the mids. understand that i was %90 satisfied with the system before the amp change and the eventual tweeter addition, so if i keep the faitals, i'm willing to bet it will suffice.

so i've been playing around with a bunch of ideas, including a pair vifa tc9fd in each pillar. i was thinking of using 4 of the daytons because they are really shallow, i can wire series/parallel retaining a 4 ohm load, and darnit....nobody else is really doing it and i just like to try things.

my initial idea was to run them up the pillar, kinda like an overlapping staircase. and then run those tweets in the air pillars. one of the reasons i posted this idea is to hear why it might possibly be a bad idea, so i'm stoke about the responses i've gotten so far.

now, would i just be better off going with a 4-5" mid/woofer that can handle a lot of power, like morels? i could do this, but it stretches my budget quite a bit.

oh, just so you know, it gets better..... i plan on having a center channel and rears!

 

[ErinH]

To be straight to the point, I think you're going to be taking a step back with your proposed solution based on what you have. If all that you feel is legitimately lacking is the right tweeter for the job then just buy a new tweeter. Don't waste your time plopping down money and time in to a multi-midrange setup when you already have a midrange driver that performs better. Get a good tweeter for your needs, then focus on the tune or learning how to tune (if you don't yet have a good grasp on that).

 

[SPLEclipse]

I'm not sure how you aren't getting desired output from the Faitals. Mine are "makes you flinch" loud from two channels of a PPI BK520.4. I will note that from playing around with them for a while, I prefer a shallow slope, low crossover point to a tweeter as opposed to a sharp slope, high crossover point. Seems to make things more "full" and less "shouty", even though overall FR didn't change much between my tunes.