Help interpret measurements - KEF Reference 5 vs. Revel Performa F228Be

[73hadd]

If you are in US, send me whichever you buy to measure.

For Revel, would you be able to get the data direct from them?

 

[Frank Dernie]

I agree with whom pointed out the big difference in msrp. KEF doubles Revel, and even if price is not always a solid indicator, I guess that comparison in unfair in this case.

All the discussions on value for money etc are completely dependant on where you live.
It is not only price but availability too. Some JBL stuff is available from UK dealers but their web site shows how little interest they have in UK customers.
Whenever I click on a link posted here by a US member to a JBL product it is greyed out with a big banner asking me if I want to go to the UK site or remain in the US site, but the "remain on the US site" is deactivated and if I click on the UK site button I just get the little plastic cheap speakers.
I have wanted to listen to and maybe buy JBL speakers ever since discovering them on a visit to the USA in 1970, several have interested me, particularly the S9800 and M2, but their attitude to this market finally pissed me off so much I am no longer interested.
Revel have recently been available but there is no local dealer.
I have always admired (since the 1960s) KEFs engineering and they would be a good choice in the UK.

 

[Trouble Maker]

Well, as much as what JBL does pisses me off too (I complained about it in another thread), KEFs site is worse. KEFs site just doesn't load if you are trying to access it from another country, just a blank page. At least with JBL it's clear what they are trying to do.

 

[Frank Dernie]

Well, as much as what JBL does pisses me off too (I complained about it in another thread), KEFs site is worse. KEFs site just doesn't load if you are trying to access it from another country, just a blank page. At least with JBL it's clear what they are trying to do.

Really? It just confirms how pointless it is making "international" recommendations of speakers then, both from a supply, service and value for money pov.
Particularly since over half of the (declared on the poll) ASR members are not in the USA and a lot of people don't fill in where they are posting from in their signature.

 

[Wombat]

Really? It just confirms how pointless it is making "international" recommendations of speakers then, both from a supply, service and value for money pov.
Particularly since over half of the (declared on the poll) ASR members are not in the USA and a lot of people don't fill in where they are posting from in their signature.

Noting location would be desirable. So would noting their areas of expertise and considered interest.

 

[Soniclife]

KEFs site just doesn't load if you are trying to access it from another country, just a blank page.

It works for me when I use a VPN to say I'm in the US, are you sure it's not at your end?

 

[massimo1974]

If you get a dem at a Kef dealer do listen to the R11, it might be more slightly different than better or worse.

Where can I find some objective data about R11?

 

[Soniclife]

Where can I find some objective data about R11?

https://www.soundstagenetwork.com/i...&catid=77:loudspeaker-measurements&Itemid=153

 

[massimo1974]

@Soniclife many thanks

 

[73hadd]

For Revel, would you be able to get the data direct from them?

My apologies, I see that 2034 data is out there, but it's not the same or nearly as comprehensive as having the work done here.

 

[73hadd]

For those interested, I did a demo of the KEF Reference 5. They were 32" from back wall, at least 10 feet from any side wall, 8ft apart and I was 8ft away, pointed at me so directly on axis.

Background: I switch between Magnepan MG-IIIa and LS50s as main speakers.

Just a few notes:
-The highlight was vocals. Tone/balance seemed right to me.
-Nice weight to the bass and midbass. Those 8 woofers do their job.
-Imaging was very precise side to side.
-After the listening session I realized I never "looked" at the speakers (although they are great to look at IMO.) I know it's an anecdote that's been used before but the image and sound were independent of the speaker locations, hidden projectors of sound, I liked that a lot.

You can tell that KEF was serious about this one. If you want that "next level" it is certainly all here.

Sorry that I was not able to compare anything side-by-side at the time to give A/B comparison.

 

[direstraitsfan98]

Yes, KEF Reference and Blades sound best when they have significant berth from the side walls. The manual suggests 3 meter distance from side walls

Most domestic environments dont have 30 foot wide spaces to play with with their speakers. I think in room you will find the Revel sounds better.

 

[richard12511]

Yes, KEF Reference and Blades sound best when they have significant berth from the side walls. The manual suggests 3 meter distance from side walls

Most domestic environments dont have 30 foot wide spaces to play with with their speakers. I think in room you will find the Revel sounds better.

That's kinda like my room. I dislike it, as it means I essentially have 0 first reflections, other than the ceiling.

 

[direstraitsfan98]

Seems like a good problem to have to me

 

[richard12511]

Seems like a good problem to have to me

I guess. I know some folks seem like to absorb the first reflections, which might be what it's like.

 

[73hadd]

Another comparison point is my rough estimate of woofer surface area, per one speaker:

Revel F228Be 100 sq. in.
KEF 132 sq. in.

ETA: not that it means anything that can't or hasn't been measured. 8" should need less excursion, but KEF made up for that with doubling the number of drivers. Without distortion measurements of both it's hard to guess. NRC measurement of KEF R11 distortion looked very low to me, compared to other speakers.

 

[skyfly]

I see a difference in impedance curve.

The Revel's port tuning frequency is 25Hz. Only a few manufacturers such as Spendor do that.

The KEF's port tuning is slightly above 40Hz.

 

[73hadd]

Two separate questions on this one:

1. What is this on axis "dip" here on all three speakers, from 6khz-8khz? It's a different shape on the KEF but still somewhat there.


I do see the listening window averages that dip out on all three but still curious.


2. One thing I'm looking for is a really detailed midbass. With this crossover info, would the Revel have a slight advantage, by carrying this in the dedicated midrange driver, instead of handing it off to bass drivers?

Revel F228Be - 260hz, 2.1khz
Reference 5 - 350hz, 2.8khz
R11 - 400hz, 2.9khz

 

[Ilkless]

Two separate questions on this one:

1. What is this on axis "dip" here on all three speakers, from 6khz-8khz? It's a different shape on the KEF but still somewhat there.

View attachment 62025View attachment 62026View attachment 62027
I do see the listening window averages that dip out on all three but still curious.


2. One thing I'm looking for is a really detailed midbass. With this crossover info, would the Revel have a slight advantage, by carrying this in the dedicated midrange driver, instead of handing it off to bass drivers?

Revel F228Be - 260hz, 2.1khz
Reference 5 - 350hz, 2.8khz
R11 - 400hz, 2.9khz

The dip is typically an effect of coherent, low-level diffraction by well-engineered waveguides. It is benign. See discussions here, for explanation as to why the listening window is more relevant:

https://www.audiosciencereview.com/...dence-based-speaker-designs.6441/#post-143362

https://www.audioholics.com/loudspeaker-design/measure-loudspeaker-performance

Listening window: a spatial average of the nine frequency responses in the +/-10 deg vertical and +/-30 deg horizontal angular range. This embraces those listeners who sit within a typical home theater audience, as well as those who disregard the normal rules when listening alone. Because it is a spatial average, this curve attenuates small fluctuations caused by acoustical interference, something far more offensive to the eye than to the ear, and reveals evidence of resonances, something the ear is very sensitive to: interference effects change with microphone position and are attenuated by the spatial averaging, whereas resonances tend to radiate similarly over large angular ranges and remain after averaging. Bumps in spatially averaged curves tend to be caused by resonances.

 

[ctrl]

The dip is typically an effect of coherent, low-level diffraction by well-engineered waveguides.

No, it's not. Gotta veto that

Opinions can be divided about the audibility of the dip in the frequency response, but presenting this dip as a positive feature is going way too far.

The 3dB dip between 6-8kHz in the axis frequency response of the Revel waveguide is definitely not state-of-the-art and certainly not part of well-engineered waveguides.
One could at most argue that Revel wants to suppress sibilants with this "sound adjustment".

The situation is different with coaxial chassis. There the design options for the transition from tweeter to waveguide/cone and for the waveguide profile are much more limited. This is why there are usually several dips.
Even with coaxial drivers, state-of-the-art products show practically no dips in the axis frequency response - see Genelec review measurement.

A few more broadly based examples to back up what has been said.

Seas DXT tweeter (manufacturer's measurement without crossover filter):


Large CD horn with Scan-Speak fabric dome tweeter (measurement without crossover filter):


DIY waveguide with Seas dome tweeter (prototype, measurement without crossover filter):


Don't get me wrong, state-of-the-art design does not automatically guarantee an excellent sounding end product. It's just that when using waveguides or horns, the axis frequency response doesn't have to show unavoidable strong interferences.