Push - Pull improvement question ?

[goldyrathore]

Hi,

What is the difference between a single driver and a push pull arrangement. I know that a push pull (drivers facing each other's front) arrangement will reduce Vas (so require half volume and double the power). But is there any other improvement in sound quality. I am talking of fairly decent drivers here.

Thanks in advance.

[busterno1]

I can only speak from personal experince I have a push pull sub .

I used a single driver first off but the wife said the box is to big so I went to iso-barik .

it offers a much lower distortion & a much cleaner sound

I have peerless drivers in my sub

[sreten]

Arranging ther drivers in push-pull cancels any assymetry
in the drivers magnetic motor and the suspension.

The result is lower 2nd harmonic distortion.
(also known as 'doubling'.)

sreten.

[Vikash]

Am I correct in assuming that such a configuration is only valuable/applicable with low frequency drivers due to basket obstruction?

[goldyrathore]

What about the driver param dfferences. Both the drivers should have the same TS params which will not be the case with any two drivers. Will drivers have to be matched in such a case?

Thanks and Regards,
Goldy

[BAM]

They must have relatively similar parameters, yes. I don't know how much difference matched drivers would make if the drivers used are fairly consistent in their quality.

[hunter audio]

hi

1) both drivers need to be identical

2) they need to be wired out of phase to the same channel

that is 4 drivers for sterio

considering a mono set - 2 drivers in two seperate
mini - enclosure

3) the port tunings have to be identical for each enclosure / so that the port s dont cancel each other out and is in phase trough the bass range - upto 200 hz

there fore for sterio each mini - enclosure cannot be combined easily and - should have a seperation baffle if you intend constructing 1 enclosure to house all 4 drivers in which there are 4 - seperate mini enclosures all with the same port tuning - other wise major cancellation

one classic and damn good speaker i have checked out in - depth is the JBL control 5 subwoofer

its a very good design - with 4 - 6 inch drivers in - 3 mini sub enlosures , (as opposed to the 4 sub enclosures i am suggesting here)

you will have to study a JBL to understand their tuning concept , 3 - mini enclosures , its their patent

when you reduce the enclosure size in a band pass design - which is not a dual chamber reflex bandpass - as is the bose

mids creep in immensly

from studying the jbl control 5 sub which is extremely compact -

the drivers are totally different - to their normal drivers

they are like the sub woofers i have mentioned else where

when fed a full - range signal and - boosting and cutting - mid and hi frequencies through a graphis eq or an 24 db active tone control had no effect and only bass was produced by the drivers

this is the - tru sub tech i refer to

plus the control 5 sub had heavy inductors in the low pass - c/o

push pull will remove all disrortion amazingly - but your enclosure needs to be rock solid and any air leak other than from the ports will result in a spl drop (phase cancellation)

suranjan

[audioPT]

Check my sub

It's hosted in my old page in geocities. Hope it works... (i've attached it)

Also my other page here (sorry, still in portuguese)

[kspv]

An excellent and detailed account of a push-pull subwoofer, and also the other types of subwoofer designs is given at

http://www.danmarx.org/audioinnovation/theories.html

For your benefit, I am reproducing the "push-pull" part of it below.

"...Two drivers share an acoustic volume of air within a single enclosure._ The best way to take advantage of this alignment is to mount one driver facing outwards with the other driver inverted and facing inwards._ The drivers are then wired so that they are electrically out of phase while remaining mechanically still in phase with one another.

Odd ordered harmonics are cancelled out by using this approach according to Vance Dickason._ According to M&K who specialize is push/pull subwoofers claim that this approach cancels out even ordered harmonics._ So take your pick._ Either way, harmonic distortion is reduced in that any anomalies or variations in the two driver's spider, cone or suspension characteristics are canceled out by the other driver's inversely proportional anomalies and variations.

The sound is as accurate and pure as it can possibly be with each driver "correcting" the other driver.__ Of course many times two drivers will share the same acoustic volume of air while maintaining the more traditional look of having both drivers fire forward into the listening environment.__ Though this does not have the same harmonic cancellation effect, all other characteristics between the two alignments is identical._ Box volume must be twice that of a single driver._ This can be easily modeled by taking the Vas of a single driver and multiplying it by two._ The system has an increased efficiency of 6dB over a single driver._ Power handling for the system is twice that of single driver._ Frequency response is the same for a single driver in an enclosure excaly half the size.

Advantages

Increased output and power handling._ Very high SPL capability.

Disadvantages

One single huge speaker enclosure that may be both unattractive and hard to move._ Response it essentially identical to building two smaller enclosures of exactly half the size but without the versatility of placement of two separate subs._ If one of the drivers blows due to too much power, the whole speaker will no longer perform because the blown driver will begin to act like a passive radiator._ If your enclosure is already ported, then this will only cause more problems._ If it is sealed, then bass response will be reduced dramatically._ There are no real disadvantages to building this kind of enclosure as the speakers will behave just as they would in enclosures by themselves._ It's very common to make MMT style speakers and use the two drivers in the same enclosure.

Best Applications

Where one sub just isn't enough._ High power high output applications._ If you choose to do the push/pull configuration, the sonic advantage may make this sub more suitable for audiophile music and critical listening experiences..."

[dezzz]

So would it be possible to do something along the lines of this:



That would give us a push/pull that was usable on drivers that handles higher frequencies, and therefore need to stay clear of a basket. Also I was looking for something dipole... But you could also implement this into a normal cabinet.

Is it possible?