• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). Come here to have fun, be ready to be teased and not take online life too seriously. We now measure and review equipment for free! Click here for details.

Polk Reserve R200: Spinorama and measurements (a really nice surprise!)

hardisj

Major Contributor
Reviewer
Joined
Jul 18, 2019
Messages
2,604
Likes
12,073
Location
North Alabama
6.5" equates to a wavelength of 2065Hz. Being that most are in the 5.25" cone diameter, that is a lot closer to 2571Hz. 8" woofers beam between 1500 to 1800 Hz in general.


You're using full wavelength. Beaming occurs before this. Pretty easy to see; just grab any spec sheet from Scan Speak, and look at where the beaming occurs. Ideally one should use 1/4-wave. But that's not feasible with standard designs. 1/2-wave is "close enough". Full wave is too high.

Here is an example:
https://www.madisoundspeakerstore.c...speak-revelator-18w/4531g-7-mid-woofer-4-ohm/

Effective Diameter = 138mm (5.4337 inches)

Using this equation:
Speed of sound / effective diameter (half-surround to half-surround) / 2 = ~ beaming

13500 in/s / 5.4337 inches / 2 = 1242Hz

Now, look at the below graphic and you'll see this frequency matches where the divergence is seen in the on/off-axis response:

18w-4531g-curve.jpg



If you use full wavelength as you suggest, then the beaming point would be at ~2480Hz. Which you can see clearly doesn't match the above and at that frequency the 60-degree off-axis response is already down about 13dB from the on-axis response. That's a big difference in directivity error if you were to place your crossover point that high.


For 8-inch woofers, you can guesstimate:
13500/8/2 = 843Hz. Throw some padding on there for effective diameter.
An example is:
https://www.madisoundspeakerstore.c...-ellipticor-21we/4542t-00-8-mid-woofer-4-ohm/

Effective Diameter ~ 6.77 inches (172mm)
13500/6.77/2 = 997Hz
21we-4-fr.jpg


Again, if you used the full wavelength calculation then you'd put your crossover at 2kHz where this speaker has become directional already.


You can use whatever formula you want but as I said: 1/4-wave is the most accurate. 1/2-wave is close enough for standard speakers. Full wave puts you well into the beaming point (especially when you are talking higher angles).

There's a thread somewhere in here where Tom Danley talks about using the 1/4-wave rule for his speakers.
 
Last edited:

Wolf

Active Member
Joined
Nov 21, 2020
Messages
195
Likes
225
Okay, I stand corrected. I never looked at it with relation to the FR, so that makes a lot more sense than it did before for me.
Thanks,
 

posvibes

Member
Joined
Jul 4, 2020
Messages
97
Likes
153
Could someone please be so kind to explain "beaming" and how that is manifested in the soundscape and what audible tell tale signs there are that it is happening and how to identify it.

I have a mental image of what it may be and that is colouring my expectation as to what how that could appear in sound terms.
 

5meohd

Member
Joined
Oct 5, 2020
Messages
5
Likes
0
Has anyone listened to the matching center? I'm looking to get into a scalable surround setup that I develop over the next year or so. I have an old Polk Monitor 5 channel setup.. since we are confined to a bedroom [yet still rocking an 85" screen with a BenQ Ht3550 projector] I've only been using the Monitor 30s, LR only. They are crap, but with a cheapo Dayton 10" sub it's serviceable... I guess. Anyway, financially, I like the idea of moving those 30s to the rears and maybe getting the 200s and matching center for LCR. Then later on either going all 200s [11 channel atmos] or moving the 200s to rears/height if some larger model proves valuable for LCR being an ATP screen.

But dang.. the Revels certainly look "sexier". Sadly I doubt I could ever afford 11 of them considering I also need an atmos AVR.
 

beaRA

Active Member
Joined
Apr 16, 2021
Messages
111
Likes
145
Has anyone listened to the matching center? I'm looking to get into a scalable surround setup that I develop over the next year or so. I have an old Polk Monitor 5 channel setup.. since we are confined to a bedroom [yet still rocking an 85" screen with a BenQ Ht3550 projector] I've only been using the Monitor 30s, LR only. They are crap, but with a cheapo Dayton 10" sub it's serviceable... I guess. Anyway, financially, I like the idea of moving those 30s to the rears and maybe getting the 200s and matching center for LCR. Then later on either going all 200s [11 channel atmos] or moving the 200s to rears/height if some larger model proves valuable for LCR being an ATP screen.

But dang.. the Revels certainly look "sexier". Sadly I doubt I could ever afford 11 of them considering I also need an atmos AVR.
None of the Reserve centers are 3-way designs so it might be better to grab an LSiM 706c on closeout sale.
 

5meohd

Member
Joined
Oct 5, 2020
Messages
5
Likes
0
None of the Reserve centers are 3-way designs so it might be better to grab an LSiM 706c on closeout sale.
Interesting point. I am certainly attracted by the initial msrp/big discount. But. What makes the older 3 way design better than the new 2 way? It would seem, reading this thread, that they've engineered a better system with this new line.

Having the 3 way leads to potential phase issues between drivers, no?
 

Transmaniacon

Member
Joined
Mar 25, 2020
Messages
91
Likes
66
Interesting point. I am certainly attracted by the initial msrp/big discount. But. What makes the older 3 way design better than the new 2 way? It would seem, reading this thread, that they've engineered a better system with this new line.

Having the 3 way leads to potential phase issues between drivers, no?

A 3-way design helps with the effects of lobing when listening off-axis. Usually this is more apparently with center channel speakers as they provide the bulk of your dialogue and detail content in a movie, and if multiple people are watching then there will be some who are sitting off-axis.
 

beaRA

Active Member
Joined
Apr 16, 2021
Messages
111
Likes
145
Interesting point. I am certainly attracted by the initial msrp/big discount. But. What makes the older 3 way design better than the new 2 way? It would seem, reading this thread, that they've engineered a better system with this new line.

Having the 3 way leads to potential phase issues between drivers, no?
A 3-way center like the 706c has the tweeter and midrange driver stacked in the middle for optimal horizontal dispersion. The flanking woofers are only allowed to play at low enough frequencies that they act as a single source. This avoids the horizontal lobing problems of the typical 2-way MTM center. Poor horizontal off-axis response defeats the purpose of a channel intended to keep the center image anchored for off-axis listeners.

As far as improvements over LSiM, they are real but minor IMO compared to the affect of the center driver configuration. The LSiM 703 already measured quite well. The updated ring radiator tweeter addressed a minor resonance and slightly increased sensitivity. You can see the 703 port resonance manifesting in a small on-axis bump at 500-600Hz. The new X-port seems to finally have eliminated the power port resonances.
 

Transmaniacon

Member
Joined
Mar 25, 2020
Messages
91
Likes
66
A 3-way center like the 706c has the tweeter and midrange driver stacked in the middle for optimal horizontal dispersion. The flanking woofers are only allowed to play at low enough frequencies that they act as a single source. This avoids the horizontal lobing problems of the typical 2-way MTM center. Poor horizontal off-axis response defeats the purpose of a channel intended to keep the center image anchored for off-axis listeners.

As far as improvements over LSiM, they are real but minor IMO compared to the affect of the center driver configuration. The LSiM 703 already measured quite well. The updated ring radiator tweeter addressed a minor resonance and slightly increased sensitivity. You can see the 703 port resonance manifesting in a small on-axis bump at 500-600Hz. The new X-port seems to finally have eliminated the power port resonances.

It would be nice to see Polk add a 3-way center to the Reserve series, we know they’ve got the drivers already since the Legend series has a 3-way design.
 
OP
N

napilopez

Major Contributor
Forum Donor
Joined
Oct 17, 2018
Messages
1,922
Likes
7,285
Location
NYC
Polk R200 is on sale at newegg for $750 with a $350 gift card.
Huh, weird. When I reviewed them the price was $700. And I just checked a few other reviews to make sure I hadn't made a mistake or misread the price. Did Polk increase the price at some point for $749 to be a sale? Maybe a COVID price increase, or maybe they realized the speakers were getting great reviews and though they could get away for selling it for more lol.
 

Erici

Active Member
Forum Donor
Joined
Jun 17, 2020
Messages
106
Likes
164
Location
Seattle Area
Huh, weird. When I reviewed them the price was $700. And I just checked a few other reviews to make sure I hadn't made a mistake or misread the price. Did Polk increase the price at some point for $749 to be a sale? Maybe a COVID price increase, or maybe they realized the speakers were getting great reviews and though they could get away for selling it for more lol.
Amazon has them listed at $750 also. But with no $350 gift card.
 

mhardy6647

Major Contributor
Joined
Dec 12, 2019
Messages
3,721
Likes
7,065
Polk's factory sales price right now is $749; the gift card's the kicker in the Newegg "sale" :) On the plus side, it looks like the deal is via Newegg itself and not some sleazoid third party using Newegg's sales portal.


I just decided not to opt in on Polk's half-price sale last month on the Legend series (I was going to buy a pair of L200s for essentially the same price) -- I think I just might spring for a pair of the R200s in walnut. My birthday is coming up... well... soon... ish. :)
 

Transmaniacon

Member
Joined
Mar 25, 2020
Messages
91
Likes
66
I got mine for $650 at Crutchfield last month, but I know a lot of audio stuff is going up in October across the board.
 

Matias

Major Contributor
Forum Donor
Joined
Jan 1, 2019
Messages
2,761
Likes
4,666
Location
São Paulo, Brazil
Huh, weird. When I reviewed them the price was $700. And I just checked a few other reviews to make sure I hadn't made a mistake or misread the price. Did Polk increase the price at some point for $749 to be a sale? Maybe a COVID price increase, or maybe they realized the speakers were getting great reviews and though they could get away for selling it for more lol.
Maybe your good review helped them to increase prices. :D
 
Top Bottom