Revel F35 Speaker Review

[amirm]

Perhaps measure a ported subwoofer.

My other sub is also sealed and servo controlled. I do have a couple of transmission line subs in my theater but they are quite large and not feasible to try to test them this way.

 

[HammerSandwich]

Could it be you who is making a mistake conflating port directionality in an anechoic chamber with port directionality in a real room? That guy is a fairly well respected speaker designer.

If I understood the link correctly, measuring bass in an anechoic chamber still isn't about the speaker's directivity. Rather, off-axis energy is significantly attenuated before reflecting to the mic. At higher frequencies, this makes the room anechoic. In the bass, the chamber doesn't function correctly, so there are reflections. Compared to a normal room's, however, these bass reflections are lower level, meaning you measure less bass energy. But that doesn't imply the speaker's actually directional that low.

 

[BYRTT]

.....The sound power is higher than on axis at low frequency.
A slight effect is seen with Amir's measurements of the klipsch RP-600M(rear ported) and the Kef R3(rear ported) but not with the F35.

Try think about anything happening at backside of transducers is inverted 180deg and a self destruction interference in open enviroment down at those frequencies, that point coupled below post by HammerSandwish thanks coupled the advanced technical curve stuff for F35 seen below what HammerSandwish said and also coupled Klippel scanner looks resolute domain of low end reach quite fantastic, then think there's a chance Klippel scanner have it right that summing the anechoic response down there without any nearby boundary is kind of self destructing interference as can be seen in directivity curve @20Hz-@40Hz, now in real world scenario in its a floorstander and most users probably would place it on a normal floor then one 2 feet away floor boundary would probably fill many of that missing response compared to manufacture curve but that floor boundary regain doesn't change that the real scenario down there is complicated and probably have a audioable signature for some discerning or skilled listeners.

Fully trusting the chart might be a mistake.

I'm not sure about Harman's recent test methodology, so let's consider a different example. Toole has posted that the NRC's results are corrected below 80Hz to match a sealed-box calibration speaker's, because the chamber's not big enough to be accurate that low. This correction introduces errors for non-sealed speakers.

ASR's recent Rythmik test gave really exciting results, which clearly show that the NFS does remove reflections at these frequencies, working better than (many, most, all?) chambers.

 

[Bear123]

Ah nice, Revel! I had the F36 for a couple weeks and then swapped them out for the F206, mainly as I wanted a front-firing port since I needed to position them close to a wall and they sounded a hair better to me. After Room EQ I was able to get a pretty flat bass response in my room (on a Yamaha receiver). Verified response with REW:

View attachment 54726

View attachment 54727

Revel makes excellent speakers!

Question; why do you feel like having a rear port close to the wall is an issue? I'm asking because AFAIK, the potential issue this can cause is a boosted response around port tune, which, without eq could cause a sound quality issue. However, since anyone with an interest for sound quality will be eq'ing down low anyways, eq will flatten this out(just as in your above example), simply resulting in greater efficiency and higher SPL capability down low with less distortion. Is there some other issue I'm not aware of as long as you have a couple of inches of spacing so that the port isn't literally plugged?

If anything, my understanding is that a rear firing port does a better job of masking noise and/or distortion coming out of the port, reducing the possibility of any audible issues the port could cause.

 

[HammerSandwich]

kind of self destructing interference as can be seen in directivity curve @20Hz-@40Hz

You got it, @BYRTT. Plotting SPL with the impedance curve helps!

We can see that the F35 is tuned to 50Hz. Below 40Hz or so, the port's just a leak. Combined with the distance from front woofer to rear port, this should behave somewhat like a passive cardioid, canceling some of the bass behind the speaker. But only below port tuning.

 

[Bear123]

I think there must surely be something wrong with how the Klippel derived the low frequency response of the F35. Here's why I think that. The F35 as measured is nearly -20 dB at 40 Hz. Room and boundary gain will not add anywhere remotely close to 20 dB back in at 40 Hz in room, yet the F35 has been measured to be flat to below 30 Hz in room, not just 40 Hz. My Revel F36 also measures flat to below 30 Hz in room(only has one rear port, so different than the F35). Am I thinking wrong here?

I understand the Rythmik sub measurements look correct, but I really don't see how you can be 20 dB down at 40 Hz and flat to 30 in room. Both can't be true.

 

[A800]

I think there must surely be something wrong with how the Klippel derived the low frequency response of the F35. Here's why I think that. The F35 as measured is nearly -20 dB at 40 Hz. Room and boundary gain will not add anywhere remotely close to 20 dB back in at 40 Hz in room, yet the F35 has been measured to be flat to below 30 Hz in room, not just 40 Hz. My Revel F36 also measures flat to below 30 Hz in room(only has one rear port, so different than the F35). Am I thinking wrong here?

I understand the Rythmik sub measurements look correct, but I really don't see how you can be 20 dB down at 40 Hz and flat to 30 in room. Both can't be true.

Looks more like around -7 dB to me.

 

[Bear123]

Looks more like around -7 dB to me.

Really? How so? On a 90 dB measurement sweep, 40 Hz output on the Klippel is around 71-72 dB. 90-71 = 19 dB.

 

[A800]

Really? How so? On a 90 dB measurement sweep, 40 Hz output on the Klippel is around 71-72 dB. 90-71 = 19 dB.

Klippel doesn't measure the port gain afaik.
I was looking at the diagram below.

 

[BYRTT]

I think there must surely be something wrong with how the Klippel derived the low frequency response of the F35. Here's why I think that. The F35 as measured is nearly -20 dB at 40 Hz. Room and boundary gain will not add anywhere remotely close to 20 dB back in at 40 Hz in room, yet the F35 has been measured to be flat to below 30 Hz in room, not just 40 Hz. My Revel F36 also measures flat to below 30 Hz in room(only has one rear port, so different than the F35). Am I thinking wrong here?

I understand the Rythmik sub measurements look correct, but I really don't see how you can be 20 dB down at 40 Hz and flat to 30 in room. Both can't be true.

Its difficult frequencyes down there and can't really know your room dimensions plus measurement protocol etc and how many of that in room response is false summing from waves that belong to a previous cycle to claim a real world in room low end reach or so, in software models room gain can sometimes be huge so why not, for fun below curve is axial room gain response simulated for the small cavity inside head phones ...

 

[HammerSandwich]

I'll guess that @amirm's F35 isn't providing full bass, because the damping material moved, per post 383. NFS results have been close enough in enough reviews now for me to believe that they're accurate, and the F35's bass is the only place I recall a major difference from Revel's claims. So far, they seem to publish legitimate specs.

 

[amirm]

FYI I have been going through detailed analysis with Klippel. So far, no issues are found with low frequency response but work continues.

However, a bug was found in the Klippel software that was causing a few spikes before 1 kHz which I attributed to resonances:

They were numerical error, not actual response of the speaker. The cause was asking for too much accuracy from the system! It has guards against this but the limits were not enough to find this problem.

Ultimately we are hamstrung by lack of the same speaker measured different ways. My friend at Harman promised me one but never came through.

 

[Bear123]

FYI I have been going through detailed analysis with Klippel. So far, no issues are found with low frequency response but work continues.

However, a bug was found in the Klippel software that was causing a few spikes before 1 kHz which I attributed to resonances:

They were numerical error, not actual response of the speaker. The cause was asking for too much accuracy from the system! It has guards against this but the limits were not enough to find this problem.

Ultimately we are hamstrung by lack of the same speaker measured different ways. My friend at Harman promised me one but never came through.

Is everyone aware that Harman has now apparently also purchased a Klippel? Is this something new or have they always had them?

 

[HammerSandwich]

My friend at Harman promised me one but never came through.

Why not reach out to Kevin Voecks directly? He's on AVSForum, and I bet he'd be interested to hear you have the NFS.

 

[Bear123]

Why not reach out to Kevin Voecks directly? He's on AVSForum, and I bet he'd be interested to hear you have the NFS.

I would say the chance of Revel/Harman not being aware that a Klippel is being used on ASR to measure Revel and competitors speakers is exactly zero.

 

[amirm]

Why not reach out to Kevin Voecks directly? He's on AVSForum, and I bet he'd be interested to hear you have the NFS.

He is the one I was talking to about this. Sadly he has gone quiet on me after years of friendship and professional relationship....

 

[amirm]

Is everyone aware that Harman has now apparently also purchased a Klippel? Is this something new or have they always had them?

Since some of their released spinorama measurements have Klippel on them, hopefully people had figured that out. They have had one before I purchased mine.

 

[vavan]

According to Rex Anderson in revel thread on AVS Mark Glazer told that "there is a lot more to loudspeaker performance than just the spin. A less expensive pair of loudspeakers could have a similar spin, but could not produce the dynamics and clarity of the F328 or F226" and there's upcoming White Paper on the F328Be

 

[Geert]

I'm still seeing the mistake of thinking that ports are directional.

I once read sound emitting from the port is directional, but the sound field expands rapidly due to the high wave lengths. If this is correct some directivity might be observed when measuring at very close distance.

 

[QMuse]

I once read sound emitting from the port is directional, but the sound field expands rapidly due to the high wave lengths. If this is correct some directivity might be observed when measuring at very close distance.

Term directivity doesn't apply in that scenario. Eveything flowing through the tube can be considered "directional" but the term directivity applies for free space wave spreading.