Multiple full range drivers....

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Ultralight

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Multiple full range drivers....
« on: 27 Oct 2017, 09:09 pm »
Seeking understanding.

Lets say one has a 4" and an 8" full rang driver.  The 8" is four times the area of the 4" driver.  Not only that, the 8" also generally goes lower in the frequency response when built as a speaker  and plays with more authority.

What if one stack FOUR 4" driver in a vertical line just about touching each other.

At that point:  Does the four 4" driver in a properly designed cabinet play lower and with more authority, or does the frequency response still look like a single 4" driver, but they simply play louder?

And any disadvantage to that type of design of multiples full ranger driver in a vertical array?

Thanks.




FullRangeMan

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Re: Multiple full range drivers....
« Reply #1 on: 27 Oct 2017, 09:25 pm »
Some prob are:
Comb filter in low treble freq(maybe not a big prob in a 4''FR but a concern in 8'')
Impedance too low in parallel
Impedance too hi in serie

Instead I would suggest these 2 FR in parallel yet a usable 4 ohms and 96dB spl and none xover or inductor.
Hemisphere FR 8 $128
Hemisphere MW 8 $115
http://www.hempcone.com/hemptone.com_new/hemptone%20website_003.htm
« Last Edit: 27 Oct 2017, 11:51 pm by FullRangeMan »

wushuliu

Re: Multiple full range drivers....
« Reply #2 on: 27 Oct 2017, 11:52 pm »
Seeking understanding.

Lets say one has a 4" and an 8" full rang driver.  The 8" is four times the area of the 4" driver.  Not only that, the 8" also generally goes lower in the frequency response when built as a speaker  and plays with more authority.

What if one stack FOUR 4" driver in a vertical line just about touching each other.

At that point:  Does the four 4" driver in a properly designed cabinet play lower and with more authority, or does the frequency response still look like a single 4" driver, but they simply play louder?

And any disadvantage to that type of design of multiples full ranger driver in a vertical array?

Thanks.

Your big issue will be comb filtering, making any such attempts doomed from the start.

Ultralight

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Re: Multiple full range drivers....
« Reply #3 on: 28 Oct 2017, 02:05 am »
Ah....just read on comb filtering.  I see.  Some debate about its impact it seems...?

As to impedence, it is not a problem. Wire two speakers in parallel.  And then run the two separate pairs in series.  So we are back to original impedance.

Anyways to my question - would four 4" in a larger cabinet then play lower or just louder than a single 4"?

Thanks.

FullRangeMan

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Re: Multiple full range drivers....
« Reply #4 on: 28 Oct 2017, 02:23 am »
Ah....just read on comb filtering.  I see.  Some debate about its impact it seems...?

As to impedence, it is not a problem. Wire two speakers in parallel.  And then run the two separate pairs in series.  So we are back to original impedance.

Anyways to my question - would four 4" in a larger cabinet then play lower or just louder than a single 4"?

Thanks.
Parallel increase spl in 3dB when the amount of drivers doubles.

Serial no increase at all, keep same spl level.

If possible avoid serial connection, in this the music signal came and go alternately.

EDITED

FullRangeMan

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Re: Multiple full range drivers....
« Reply #5 on: 28 Oct 2017, 02:51 am »

JLM

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Re: Multiple full range drivers....
« Reply #6 on: 28 Oct 2017, 10:39 am »
Multiple drivers can't go lower, just louder.  The Unity driver is one such beast (a large horn with drivers mounted in each interior face), but haven't seen it around for a few years.

Vertical arrays increase efficiency by projecting sound in a 2 dimensional pattern vs. 3 dimensional as from a single source, but to be effective the array must span from floor to ceiling.  Which means buying 18 drivers (8 foot ceiling) and lots of wire, thus driving costs up or quality of drivers/wire down (which beyond DIY becomes a horrendous issue as drivers normally amount to 10% of speaker MSRP and the quality of cheap drivers used in such applications is strikingly poor).

And of course there's the dreaded comb effect.  That's why most vertical arrays are 2-way, adding either ribbons or even more tweeters and more wire (more cost or even cheaper drivers). 

Worse of all you lose vertical imaging as everything sounds 8 feet tall.

Ultralight

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Re: Multiple full range drivers....
« Reply #7 on: 28 Oct 2017, 10:18 pm »
THANK YOU EVERYONE for the information.   Saves me from trying some hair brained ideas and wasting $$$. :)

FullRangeMan

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Re: Multiple full range drivers....
« Reply #8 on: 28 Oct 2017, 10:42 pm »
The IDS25 is everything that JLM said, but I would want to listen this tower some say>
http://www.ids25.com/

Folsom

Re: Multiple full range drivers....
« Reply #9 on: 28 Oct 2017, 11:00 pm »
Multiple drivers can't go lower, just louder. 

Not true. You can design the crossover to sacrifice efficiency for playing lower with more volume. The reason it can work as you multiply drivers is because it you divide up the Xmax needed to get there, that otherwise would never be sufficient.

S Clark

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Re: Multiple full range drivers....
« Reply #10 on: 28 Oct 2017, 11:37 pm »
Yep, this is a common misconception. Say a midwoofer is down 8 db at 30hz. Normally you would never hear that 30hz note, but drop the rest of the signal by 8, and it's right on line with every thing else.  Do it 12 times, and you've got a lot of output at 25-30 hz with a mid driver...and it's a helluva lot faster than a couple of sluggish 12" woofers.  This is something that I actually know a bit about.  And comb effect is related to frequency and spacing.  If the designer knows what he's doing, he can avoid it. 



S Clark

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Re: Multiple full range drivers....
« Reply #11 on: 28 Oct 2017, 11:59 pm »
Seeking understanding.

Lets say one has a 4" and an 8" full rang driver.  The 8" is four times the area of the 4" driver.  Not only that, the 8" also generally goes lower in the frequency response when built as a speaker  and plays with more authority.

What if one stack FOUR 4" driver in a vertical line just about touching each other.

At that point:  Does the four 4" driver in a properly designed cabinet play lower and with more authority, or does the frequency response still look like a single 4" driver, but they simply play louder?

And any disadvantage to that type of design of multiples full ranger driver in a vertical array?

Thanks.
The multiple 4" driver plays faster, and with more detail.  Recovery time is less, inertia is less.  Lower??? Depends on the driver.  The only system I've heard that can rival the accuracy and output of a big line source bass are the servo subs. 

DaveC113

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Re: Multiple full range drivers....
« Reply #12 on: 29 Oct 2017, 12:54 am »
It will work, but I don't think it's a great idea... others disagree and if you google "line array full range driver" you'll find them.

The comb filtering effect looks ugly but it's effect is debatable. Obviously, it doesn't bother some, ymmv... I don't have enough experience w single driver line arrays to give you any good opinions on this, I heard one briefly at a show and didn't like it. If you want a line array I'd look into a GR LS9/LS6.

On the design, I think it's technically flawed to some degree but had advantages in large spaces as SPL doesn't drop off as fast. It adds complexity with all sorts of things, you'd need to research and learn about them...  If you're a single driver fan and want more frequency extension and SPL ability, rather than deal with that complexity I'd go with an augmented single driver, add a woofer and maybe a tweeter while using the single driver in the frequency range it can maintain a fairly flat response in, which will differ a bit by design and surface area of the cone. If you want to fill an auditorium or something a line array is worth considering but otherwise adding a woofer is a far better ideal imo. 


Ultralight

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Re: Multiple full range drivers....
« Reply #13 on: 29 Oct 2017, 01:22 am »
Thanks for all the additional conversations.

Looking at 'comb filtering', it seems that they occur at higher frequencies.  So for those who run 1.5 type system where the 2nd full range is low passed, then comb filtering does not exist?  Or am I not understanding what comb filtering does?

The line array does look very fascinating - would love to hear one of full range drivers without augmentation from tweeters but unfortunately these are not common at dealers I don't think.  My challenge is always wanting to play in a small room and yet have the speakers sound huge, which to me means a small driver with wide dispersion and even bipoles and speakers pulled out at least 4 feet away from the wall. But the problem with full ranger is the lack of bottom octaves.


FullRangeMan

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Re: Multiple full range drivers....
« Reply #14 on: 29 Oct 2017, 01:26 am »
Usually manufactured 1.5 way speakers use a xover or inductor, cap etc to cut the woofer under 500Hz.

FullRangeMan

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Re: Multiple full range drivers....
« Reply #15 on: 29 Oct 2017, 01:29 am »
But the problem with full ranger is the lack of bottom octaves.
Who have to made a big bass is the enclosure not the driver, but DIYers dont know how to stufffing the enclosure, they put Sonex 20mm layer and want hear a big bass so when it dont happen they blame the FR driver.
>:
http://www.audiocircle.com/index.php?topic=100689.0

JLM

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Re: Multiple full range drivers....
« Reply #16 on: 29 Oct 2017, 11:23 am »
But the problem with full ranger is the lack of bottom octaves.



My Fostex F200A drivers are rated 30-20,000 Hz, 89 dB/w/m, 8 ohms, 27 watts continuous/80 watts peak but sadly no longer in production. 

8 inches, huge AlNiCo magnet, no whizzer (mechanical crossover) so they beam like crazy at higher frequencies, $575 each when last available.


I know of no other comparable drivers, but some exotic field coils from Europe might go as low.

JohnR

Re: Multiple full range drivers....
« Reply #17 on: 29 Oct 2017, 01:25 pm »
But 2mm Xmax.

This is just a question of personal preference, there's no point in arguing about it. Either the bass from a particular implementation is good enough for you in a particular listening situation, or it's not.

FullRangeMan

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Re: Multiple full range drivers....
« Reply #18 on: 29 Oct 2017, 04:34 pm »


My Fostex F200A drivers are rated 30-20,000 Hz, 89 dB/w/m, 8 ohms, 27 watts continuous/80 watts peak but sadly no longer in production. 

8 inches, huge AlNiCo magnet, no whizzer (mechanical crossover) so they beam like crazy at higher frequencies, $575 each when last available.


I know of no other comparable drivers, but some exotic field coils from Europe might go as low.
I dont said it, I quoted an other post.
FullRangeMan on Today at 01:29 am
    But the problem with full ranger is the lack of bottom octaves.

Its flat knoiw that whizzer cones collateral efect is made the mid range wild uprise over 2kHz and increase the MMS.
Do you think filed coils dont beaming?

richidoo

Re: Multiple full range drivers....
« Reply #19 on: 29 Oct 2017, 09:40 pm »
Acoustic impedance is what you're asking about. Impedance is the scientific name for the driver's grip on the air. The higher the acoustic impedance, the better grip the driver cone has on the air, the better it can control the air and the more efficiently energy (and information) is transformed from kinetic to acoustic.

In general, impedance decreases with wavelength, and increases with cone area and velocity.

In practical terms, reduced impedance means the cone cannot pressurize the air molecules efficiently. Air escapes pressurization because the cone is too small and/or moving too slowly to contain it. Increasing the cone size or velocity pressurizes air before it can escape the cone.

Adjacent small drivers can cooperate to contain the air for more efficient pressurization. A rectangular array is better at this than a line array which only cooperates in the vertical. Line arrays of full range drivers need EQ to boost the bass, but a rectangular array would need less because it's simulating a single large cone.

Treble in line array is attenuated by comb filtering and requires some EQ for flat response, but the comb filtering itself is not audible once you get some distance away from the arrays. The treble tone of FR line array is different than a single tweeter, or line array tweeters, but the combing is not noticeable unless you are close to the array. Some people love the treble quality of well engineered FR line array. It is not inherently "bad" as some have suggested. ymmv :)