Dual drivers

MacLeod · October 2005

I was just pondering something. What is the difference in SQ between say a Monitor 30 and a Monitor 40? What difference would having dual driver make over a single driver.

I know the obvious reasons like more surface area so you get a little more volume and bass response but is that it?

VR3 · October 2005

MTM designs have alot of ups. One of the pluses are - as you mentioned more bass and a louder volume.

"The tweeter acts as though it were mounted, in effect, right in the center of one large driver. This symmetrically concentric (or D'Appolito) point source mounting results in more coherent wave propagation with further improvements in the areas of driver blending, depth retrieval, lateral imaging and dispersion. In addition, the early arrival soundfield is focused away from the floor and ceiling and directly at the listener for even greater clarity." - www.definitivetech.com

Not sure if Polk uses D'Appolito technology or if it is an array, but basically it is a MTM design.

I personally have grown to like 2-way designs, but I would take a good MTM design anyday of the week

MacLeod · October 2005

I never thought of the "single source" idea. That does make a lot of sense tho.

Those inwall speakers we got to hear at Polkfest were MTM design and had very tall and deep stage and I since have been wondering if it was the dual drivers that gave it that characteristic.

VR3 · October 2005

Eh...

Does it give it that characteristic? Well - I wouldnt go around ignoring 2-way designs (single mid, one tweet) just because there isnt a midbass mounted above it...

MacLeod · October 2005

Those arent necessarily midbass driver tho are they? I thought it was just dual midranges.

VR3 · October 2005

midbass is midrange and some bass.

Midranges are drivers that do like 250hz to 5khz or so....

Midbass drivers can go down low, 30hz low at times... all while doing the mids.

aaharvel · October 2005

The difference between dual mids and 1mid.
A wee bit more bass, a wee bit more volume, bigger cabinet, bigger price tag.

Unlike a horizonal speaker (off center positioning and Precedence Effect), I just don't see how 2woofers on a vertical plane can make much if any difference in sound quality- except of course for volume and bass response.

I've always been a fan of one midrange, 1 tweeter setups- 2way bookshelf speakers in general. The cabinet is smaller- therefore it's less prone to standing waves and acoustic resonances inside the cabinet. I just fail to see the benefits in a real life situation.

imo.

MacLeod · October 2005

Thats different than car audio. Midbass drivers rarely go above 200 Hz. They can go higher but they arent very good at it.

Its the opposite with midranges. They can hit down to 50 Hz but not very well.

So the drivers in the Monitor 40, one is a midrange and the other a midbass?

VR3 · October 2005

The M40 is a 2-way design with two midbasses. It has a 2.3 khz crossover point on both drivers...

Yall are probally talking about the same thing, you just call it something different. Midranges are small drivers, I have seen some in CA that were like 3"...

Midbass drivers are 4.5" to 7.5" - they usually playing between 30hz to 5khz (usually not THAT high)...

EDIT: Yes, there are larger midrange drivers - but they have very low excursion.

nadams · October 2005

As sid said, the m40's just have two midranges. Those new in-walls we heard @ polk had a tweeter, midrange, and midbass.

MacLeod · October 2005

Midranges in CA can be as small as 4" and as large as 7". 3 way component sets normally use a 4" mid and 6.5" midbass with the midbass running 50-200 Hz +/-.

2 way sets almost always use a 5.25 or 6.5" midrange which runs from 80-3500 Hz +/-. I dont know of any CA midbass drivers that can adequately play midrange frequencies. I guess thats because you need a lot more bass response in a car to overcome the noise floor so having one dedicated to 50-200 Hz response ensures itll have plenty of oomph.

Mike682 · October 2005

Ok...while on the topic, and on a side note, why does the r20 and r30 have different wattage ratings?? The r30 has a recommended wattage rating of 20-150w while the r20 has a range of 20-100w. It looks like they have the same drivers (I never took my drivers out)...Is it because of the crossover (if they are different)??

Also I was looking at the lower 3db freq resp and the difference between the two is only 5hz lower for the R30. So with having the same drivers with a bigger enclosure you can get a lower response. However, when looking at the size diff between both enclosures, it looks like it takes a lot of space to actually start seeing any huge gains in freq response with the same drivers. Am I right??

Now the dual drivers in the R50 will get you an extra db sensitivity and 5hz deeper response when compared to the R30....

Still learning..

Mike

Mazeroth · October 2005

MTMs are inferior to MTs in the fact that they have combing effects, which are cancellations of sound due to having two radiating points too far apart. The higher the frequency the drivers needs to play, the closer they need to be in an MTM for the cancellation to not take place.

For example..if you have a 5.25" woofer and place another 5.25" woofer on top of it with frames touching (in a cabinet) combing effects will start to begin around 2500hz, with the first cancellations occuring around 5000hz. If you use steep order crossover slopes the effects of this can be minimal. Now, when was the last time you saw and MTM with the frames touching? Exactly...it doesn't happen. They are usually separated by at least 3-4".

The only advantage an MTM has over an MT is the 3db efficiency gain and the ability to play 6db louder. You could also argue that less distortion is displayed at high volume levels due to having twice the radiating surface, which is true.

That be all, folks!

heiney9 · October 2005

Mazeroth wrote:

MTMs are inferior to MTs in the fact that they have combing effects, which are cancellations of sound due to having two radiating points too far apart. The higher the frequency the drivers needs to play, the closer they need to be in an MTM for the cancellation to not take place.

For example..if you have a 5.25" woofer and place another 5.25" woofer on top of it with frames touching (in a cabinet) combing effects will start to begin around 2500hz, with the first cancellations occuring around 5000hz. If you use steep order crossover slopes the effects of this can be minimal. Now, when was the last time you saw and MTM with the frames touching? Exactly...it doesn't happen. They are usually separated by at least 3-4".

The only advantage an MTM has over an MT is the 3db efficiency gain and the ability to play 6db louder. You could also argue that less distortion is displayed at high volume levels due to having twice the radiating surface, which is true.

That be all, folks!

Well it's just like anything else in audio....it's debatable. Your above statement is pretty strong and a true well designed MTM (D'Appolito) will not react this way. There are certainly advantages to both types of design (MTM MT) but to say the ONLY advantage is 3db more efficiency gain and ability to play 6db louder is simply not true. If it is such an inferior design why is it one of the most popular and used in many highly regarded and expensive speakers? I'm not saying it's the end all of speaker designs but it certainly has proven to be an excellent design that when done properly gives excellent results

D'Appolito
A loudspeaker configuration developed by and named for Joe D'Appolito, in which a high frequency driver, or tweeter, is positioned between two midrange or low frequency drivers that each cover the same frequency range. Depending on the exact implementation the speakers can be positioned with a vertical and/or horizontal orientation. In either case the two midrange drivers serve a couple of purposes: they combine to create a larger effective woofer or midrange driver size, and they also serve to control the dispersion of the tweeter. The tweeter's output is somewhat corralled or contained by the sound coming from the midrange drivers in a similar way to how two parallel surfaces control dispersion. There are some variations on the design where two same sized woofer/midrange drivers may cover slightly different frequency ranges, however those aren't considered true D'Appolito designs. (Input from an inSync Reader:) The D'Appolito design specifies a third order crossover network. �The tweeter is coordinated with the woofer so that at the selected crossover frequency, the drivers all have similar horizontal dispersion. �(This is not easily accomplished because many drivers behave badly at the extremes of their range.) The advantage of doing it all correctly is one of the most seamless blending of drivers possible. �The result is an absence of any sudden change in directivity with frequency. �This may not mean much for monitors where there is a limited listening area, but in a typical room where a large percentage of the sound is reflected by the room, the effect is dramatic.

VR3 · October 2005

Im going to stop reading this thread...

It only makes me want the BP30 MORE...

*drool*

Cool information Hieny

heiney9 · October 2005

Vr3MxStyler2k3 wrote:

Im going to stop reading this thread...

It only makes me want the BP30 MORE...

*drool*

Cool information Hieny

Sorry to make you drool Sid

. I'm not as schooled as you or some of the others her as far as my VAST knowledge of speaker design. But since my RTA-11s seem to have a D'Appolito config. I have done some research...so, glad it was helpful.

H9

Dual drivers

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