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Polk S30 Center Speaker Review

DanTheMan

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Good review, I think this is the first time I've seen anything outside of Dr. Toole's book discussing the inherent issues with MTM centre speakers and reflections. Unfortunately, it seems most manufacturers offer this configuration and little else.
The Loudspeaker Design Cookbook mentioned it as well.
 

tecnogadget

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Good review, I think this is the first time I've seen anything outside of Dr. Toole's book discussing the inherent issues with MTM centre speakers and reflections. Unfortunately, it seems most manufacturers offer this configuration and little else.

I still recall how 1 decade ago I stumbled upon this excellent read about the effects of MTM designs on center channels. By that time I owned a “Nested” (raised tweeter) MTM center, and did my fair share of Horizontal vs Vertical mounting.
Nowadays I own a concentric-coaxial center channel, and I’m glad issues like lobbing and horizontal dispersion are a thing of the past.
(sadly many of the great .gif are down)

https://forum.blu-ray.com/showthread.php?t=89614#post1681507

What do you mean by “this centerspeaker”? It’s not just this center. Probably 80 to 90 % of centers available are MTM’s like this one. Very few of them employ a 2.5-way crossover that would mostly mitigate the problem. This travesty has been going on for decades and nobody seems to care..

Sadly thats true. Most manufacturers take advantage of their costumers lack of technical knowledge, and use all sorts of “fantasy” marketing on their brochures instead...
No one address this issue and informs you “hey, you get the best performance of this speaker by mounting it vertically”, hence by doing so you loose one of the advantages for a center channel: small footprint to fit a Screen.

Still, some manufacturers do care about this, the ones making coaxial centers, or variations of MTM design that lessen the issue.

For example, Boston Acoustic (RIP) used to put a rotating logo on the grilles of the CR series, so you could position the speaker either vertically or horizontally.
The VR12 was the industry’s very first three-way center channel speaker with its midrange and tweeter in a vertical line, to avoid the destructive picket-fencing horizontal radiation pattern that afflicted virtually every side-by-side M-T-M center speaker that existed at the time.
 

TNT

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Standing such a speaker up in the intended application would typically obscure the picture from the screen - no?

//
 

DSJR

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Euro 139 each is incredibly cheap for the basic performance on offer and as I'm not at all into home theatre, I reckon a pair of these stood on end and stand mounted and tilted if necessary to get the tweeter at ear level, placed fairly close to a rear wall with ports bunged, you'd get a really good cheap stereo pair! Oh, the very slightly hot tweeter is as nothing compared to high end speaker confections with 5+dB rises over 8kHz to 20kHz - it's been discussed elsewhere with proof how bad our male ears become over 50 years old (it's a steady decline from adulthood) so I doubt many of us oldies can hear reliably much over 10khz anyway (a speaker designer in his nearly mid 60's who to my knowledge has ever thrashed rock & roll loudly in his life, managed 13kHz where his eight year old granddaughter could reliably hear 21kHz apparently using a tweeter test rig - this an informal discovery)

P.S. I really wouldn't worry too much about the 900Hz peak. Most home theatre people out there wouldn't notice and if said 'centre speaker' is in a furniture unit, maybe the rear output won't be an issue?
 

KxDx

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I know HSU has a coaxial that can be used in either configuration but no one else does.
KEF used to... when I had 5.1 it was a set of Q-Series speakers, and the center was a concentric driver. Pretty sure it was this Q9c:

Q1_Q3_Q5_Q7_Q8s_Q9c_r.pdf (kef.com)

Looking at their product line now, it seems like they also use the horizontal woofer arrangement like almost everyone else.
 

voodooless

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KEF used to... when I had 5.1 it was a set of Q-Series speakers, and the center was a concentric driver. Pretty sure it was this Q9c:

Q1_Q3_Q5_Q7_Q8s_Q9c_r.pdf (kef.com)

Looking at their product line now, it seems like they also use the horizontal woofer arrangement like almost everyone else.

The woofer arrangement is not perse a problem. The concept is. For instance, the KEF R2C has a coax plus two woofers on either side. The crossover is at 400 Hz. By that frequency, the polar response is virtually Omni-directional already and it does not matter that much what the arrangement of the woofers is.

You can get roughly the same effect with a normal MTM by not letting one of the woofers play the midrange. That way you'll get a 2.5-way system with much better directivity for a center-speaker. But it's more difficult to design and more needs more filter components, so is more expensive.
 

sarumbear

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You can get roughly the same effect with a normal MTM by not letting one of the woofers play the midrange. That way you'll get a 2.5-way system with much better directivity for a center-speaker. But it's more difficult to design and more needs more filter components, so is more expensive.
That is how I solved the issue back in the 90s with SILVER 5L :)
 

testp

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Thanks as always for the review Amir!

Additionally, when the center drops to 3.4 ohms of resistance how does that affect an AVR or Integrated Amp that has a factory rating of 6 ohms as being the lowest certified rating. Would prolonged exposure to repeated dips to such a low resistance damage anything or can most equipment handle this dip in resistance with no long-term ills? After reading various opinions on this matter I need some clarification because there is a lot of conflicting information out there on the web.


testp:

dont shoot the messenger

this is how i use this 6 or 8 ohm switch behind the amplifier, i always use 8 ohm setting, no matter what speakers i use (only watch out that amplifier does not get extremely hot, and even then: protection would trigger if it really overheats, i've seen none of that happening, amplifier barely gets warm, but i have 2 ch. amp)

i read it somewhere that, that switch is only to meet regulations mostly and is not anything sophisticated,
lower 6 or 4 ohm setting will limit amplifier output wattage - by limiting the amplifier input power: probably amperege, so if you use world's most power hungriest speakers and max the vol. amp can only operate maybe ~75% of power and not overheat or something.

most speakers are not that demanding, so 8 ohm (or highest) setting would at least make the amplifier have its full power reserve.

More powerful amps do not have this switch, oh darn you had AVR so.. lots of channels., maybe that would be better reason to use this switch,

but still something to ponder about... :)
 

DanTheMan

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I've not had a chance to read that one yet
I’d personally skip it at this point. It does go through the fundamentals and all, but rolling your own isn’t all that economically sensible now. Sites like this one show you how to save time and money With commercial offerings. With what’s available in the cookbook, you won’t beat an Infinity Primus series let alone pricier options.
 

ezra_s

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wah, sexy looking center speaker, I wish someone sent the S35

s300.png
 
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ezra_s

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imagine how bad that is for horizontal sensitivity....

I use it for movies in my AVR setup at the living room. I havent analyzed it or anything but I have no complains (nor that I am a demanding or knowledgeable).
 

ezra_s

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abdo123

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I think the Polk S35 (bigger brother with 4 extra woofers) is particularly interesting, it is only 6.1" (15.49 cm) deep so it can pretty much go anywhere, especially vertically.

the Polk S30 can play pretty loud for their size, so the Polk S35 could be pretty impressive.
 
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