Revel F35 Speaker Review

[waynel]

LF has a natural tendency to emit in a non-beam fashion (can't remember the right english word for that effect at the moment), so no wonder there. LF naturally tends to go around the corner, unlike a laser beam.

Yes but look at the spin from the F328Be (rear ported) here
https://www.avsforum.com/forum/89-speakers/710918-revel-owners-thread-585.html#post59387840

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.

 

[q3cpma]

I'm wondering why we are not seeing a difference between the on axis and sound power at low frequency for a rear ported speaker. Looking at the spin for the Revel F226BE posted here: https://www.avsforum.com/forum/89-speakers/710918-revel-owners-thread-585.html#post59388274

There is very little difference between the on axis and sound power responses at low frequency as this is a front ported speaker.

Looking at the F328Be (rear ported) here:
https://www.avsforum.com/forum/89-speakers/710918-revel-owners-thread-585.html#post59387840

We can see a clear difference between the on axis and sound power at low frequency as this is a rear ported speaker.

This raises 2 questions:

1) Was something wrong with Amir's Klippel measurement as far as capturing the low frequency sound power form the rear port?
2) Should the speaker numerical score algorithm use sound power rather than on -axis at low frequencies as to not handicap rear ported speakers (forgive me if this is already accounted for)?


Wayne

It's a beginner's mistake to think that ports radiate forward; you can see a lot of people saying that front ports make the speakers more boundary friendly, for example. As HammerSandwich said, it's easy to see that frequencies that low correspond to wavelengths way too big to be contained by the enclosure, thus making them omnidirectional.

 

[QMuse]

Yes but look at the spin from the F328Be (rear ported) here
https://www.avsforum.com/forum/89-speakers/710918-revel-owners-thread-585.html#post59387840

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.

I see what you mean but to be honest I was ignoring that part of spinorama so far.

 

[waynel]

It's a beginner's mistake to think that ports radiate forward; you can see a lot of people saying that front ports make the speakers more boundary friendly, for example. As HammerSandwich said, it's easy to see that frequencies that low are way too big for the enclosure to contain it, thus making them omnidirectional.

I'm making a beginners mistake in pointing to the spins? The effect looks pretty clear to me.

 

[q3cpma]

I'm making a beginners mistake in pointing to the spins? The effect looks pretty clear to me.

Correlation is not causation. Could be standing wave port leakage (doubt it at that frequency, though).

 

[waynel]

Correlation is not causation. Could be standing wave port leakage (doubt it at that frequency, though).

Check out this link
https://www.ecoustics.com/electronics/forum/home-audio/382724.html#POST1251197

Correlation is not causation. Could be standing wave port leakage (doubt it at that frequency, though).

 

[HammerSandwich]

I'm making a beginners mistake in pointing to the spins? The effect looks pretty clear to me.

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.

 

[QMuse]

Check out this link
https://www.ecoustics.com/electronics/forum/home-audio/382724.html#POST1251197

EDIT: Unless you're speculating that Klippel is somehow missing to record rear port response?

 

[waynel]

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.

I agree that the Rythmik sub test shows that the low frequency behavior is measure properly but that sub is not ported (or rear ported)

 

[waynel]

EDIT: Unless you're speculating that Klippel is somehow missing to record rear port response?

I'm not. It should show up more in the sound power than in the on-axis. You see this with some of Amir's other measurements . If I were to speculate
1) the very low frequency looks funky in the F35 measurement, something I have not seen before
2) could it be the port was plugged?

 

[amirm]

Sure, what lonewolf said, but to my understanding test "conclusion" & recommendation should refer to objective data and not listening impressions.

No. Recommendation is based on my personal judgement of whether I would buy it or not. It includes looks, design, objective measurements, industrial design, price, etc. Subjective listening is also part of it when it is in the review. Conclusion is my quick summary for someone skipping the review.

I didn't used to make recommendations when I started and folks kept asking for it. So we have it now and is a fixture of what I do.

Please don't argue with me on this. It is what I do and been doing across some 300 reviews now. If what you care about is the measurements, it is there. Just skip the rest.

 

[q3cpma]

Check out this link
https://www.ecoustics.com/electronics/forum/home-audio/382724.html#POST1251197

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

 

[waynel]

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

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.

 

[amirm]

I'm wondering why we are not seeing a difference between the on axis and sound power at low frequency for a rear ported speaker. Looking at the spin for the Revel F226BE posted here: https://www.avsforum.com/forum/89-speakers/710918-revel-owners-thread-585.html#post59388274

There is very little difference between the on axis and sound power responses at low frequency as this is a front ported speaker.

Looking at the F328Be (rear ported) here:
https://www.avsforum.com/forum/89-speakers/710918-revel-owners-thread-585.html#post59387840

We can see a clear difference between the on axis and sound power at low frequency as this is a rear ported speaker.

There is waviness in both of those measurements but especially the F326BE. That indicates the anechoic chamber has room modes there that affects measurements. Anechoic chambers are also not large enough to proper show far-field data. Port impact is a problem in all of this.

 

[waynel]

There is waviness in both of those measurements but especially the F326BE. That indicates the anechoic chamber has room modes there that affects measurements. Anechoic chambers are also not large enough to proper show far-field data. Port impact is a problem in all of this.

Thanks Amir,

I assume the Klippel system is not effected this way? Do you expect to see low frequency sound power to be greater than on axis for rear ported speakers using Klippel measurements?

Wayne

 

[q3cpma]

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.

There's absolutely no relation between the room and how directional a speaker is. How the waves react with boundaries is another thing, but bass frequencies way under the baffle step and without using controlled cancellation (i.e. building a cardioid dispersion) are always omni.

 

[amirm]

2) could it be the port was plugged?

Good suggestion. Just looked and the two ports are open. But looking inside, the padding on the right side is not glued and had come loose and moved an inch toward the bottom port. The top port is more open however, there is padding horizontally separating the top of the box and its port, and the bottom. The woofer is in front of the top port so I am assuming just the padding is there rather than a hard barrier. Any ideas if either one of these impacts bass response?

 

[waynel]

Good suggestion. Just looked and the two ports are open. But looking inside, the padding on the right side is not glued and had come loose and moved an inch toward the bottom port. The top port is more open however, there is padding horizontally separating the top of the box and its port, and the bottom. The woofer is in front of the top port so I am assuming just the padding is there rather than a hard barrier. Any ideas if either one of these impacts bass response?

perhaps measure the other speaker?

 

[amirm]

perhaps measure the other speaker?

There is no other speaker. I only bought one.

 

[HammerSandwich]

Perhaps measure a ported subwoofer.