Revel reintroduces their $10,000 sealed 18" sub

[monkish54]

But if the driver was designed for the larger box, wouldn't it be capable of higher output than a driver in smaller box?

Both the Revel and Velodyne were designed for use in their specific enclosure size.

Are you asking if a driver designed for and used in a large box will be able to play louder than a different driver designed for and used in a small box?

It would depend on the T/S parameters of the drivers. For example: the Revel and Velodyne might have the same diameter voice coil, but how long is the magnetic gap? How long is the coil? Is the coil underhung or overhung? What is the sensitivity of each driver? How do the non linear distortions of the two drivers compare? What is the actual SD of each driver? You'd be surprised of the variation among "same" size drivers!

For the sake of argument, lets play with WinISD! Let's use two drivers that require different box sizes and have similar specs. (Specs meaning both what Revel and Velodyne have released about their subwoofers. The T/S parameters will differ..just as the Revel and Velodyne no doubt differ.)

Revel says their driver can handle 2,000 watts RMS and Velodyne says their driver can handle 1,250 watts RMS. Neither company gives SD or sensitivity so the power handling is almost completely useless for comparing! If the Velodyne is 3db more sensitive than the Revel, the Revel will need 2,000 watts to play at the same SPL as the Velodyne at 1,000 watts! Likewise, if the Velodyne is 4 ohm and rated as 90db/ 1 watt and the Revel is 8 ohm and rated as 90db/ 1 watt the Revel will need 2.83 volts to play at the same db level as the Velodyne using only 2 volts.

Revel and Velodyne both give VC size. Both come in at 3".

With a bit of searching I found 2 comparable drivers, the Dayton TIT400C-4 and the Dayton RSS390HF-4. Both are 15" drivers rated as 4 ohm, both have similar power handling, and they both have the same size voice coil. As far as the Revel vs Velodyne comparison goes, this gives the large box driver a "leg up" (if the big box theory is correct) as we now know both drivers have the same impedance whereas before it was a mystery!

The RSS390HF-4 extends lower (30hz) in a sealed box than the TIT400C-4 (40hz), but that is irrelevant as both the Revel and Velodyne claim to play down to 20hz, and this demonstration is about loudness not whether ported or sealed is better for any given driver. I limited the frequency range to 100hz as I wouldn't use a sub much higher. The TIT400C-4 has a pretty narrow response in a sealed box. It rolls off 3db at ~200hz, but this is, again, irrelevant. The RSS390HF-4 extends much further than 200hz.
The RSS390HF-4 is in a 252.00 liter enclosure.

The TIT400C-4 is in a 149.5 liter enclosure.

Frequency Response from 30-100hz

Xmax @ 800 watts
TIT400C-4 xmax 20.5.
RSS390HF-4 xmax 14.0

Max SPL

As can be see from the graphs, the TIT400C-4 has a greater maximum SPL than the RSS390HF-4. At 800 watts the RSS390HF-4's xmax is reached at about 42-43hz, 12-13hz higher than its -3db point, while the TIT400C-4's xmax is reached at 30hz, 10hz lower than its -3db point. At the TIT400C-4's -3db point, 40hz, xmax is far from being reached. You could easily use a high pass filter so as to increase power handling, but you limit frequency extension further.

While the response of the TIT400C-4 could be smoother in a large vented box, for demonstration purposes I put it in a small sealed enclosure. Both drivers were put in their respective PE recommended enclosures.

 

[MidnightSensi2]

You're kidding, right? There were no curved cabinets in the 70s, there were no 18" aluminum cone drivers, there were no neo drivers, there were no Class D amps, there was no DSP, there was no graphics interface for a computer. So tell me again how this is like something from the 70s?

I'm talking about the exterior design.

 

[Irvrobinson]

For the sake of argument, lets play with WinISD! Let's use two drivers that require different box sizes and have similar specs. (Specs meaning both what Revel and Velodyne have released about their subwoofers. The T/S parameters will differ..just as the Revel and Velodyne no doubt differ.)

I'll be honest with you, I'm not following this analysis, and the conclusion makes no sense to me. From a business perspective, a large box is a disadvantage. It costs more to build, more to ship, and I would guess there is a reduction in market size for every additional liter of cabinet volume. So the first question that comes to my mind is why Velodyne, for example, would build a new generation of product that has a substantially larger volume than the previous generation of product, if a smaller sealed cabinet volume is better for a similarly sized driver? What am I missing? By your analysis Revel and Velodyne are stupid.

 

[Irvrobinson]

I was thinking about it, and one of the comments I remember reading in Gene's review of the DD15 Plus reinforced my belief that increasing cabinet size was a good thing, and made me think that he thought a larger cabinet (and, of course, a driver with a greater xmax to take advantage of it) produced higher output:

Velodyne claims their DD+ line of subs have between 4-5dB more output for each comparable model to the original DD series of subs. Based on the driver differences between the two products (and the fact that the new DD-15+ box volume has increased nearly 25%) we have little reason to doubt this claim, but of course we measured to confirm the results as you will read later in this review.

Can someone with the appropriate technical expertise explain in prose how the relationship between cabinet volume in sealed enclosures and output really works? I ask because now I feel confused by what I thought was the case, while I may have been clearly mistaken.

(Perhaps I should stop being so damned lazy and finally just study speaker design.)

 

[monkish54]

I'll be honest with you, I'm not following this analysis, and the conclusion makes no sense to me. From a business perspective, a large box is a disadvantage. It costs more to build, more to ship, and I would guess there is a reduction in market size for every additional liter of cabinet volume.

I don't disagree with the above.

You originally said the Revel should do better because the subwoofers have similar specs but the Revel is in a larger box. I asked if you had seen the T/S parameters because using a larger box wasn't relative to response or volume unless Velodyne used the wrong sized box for their driver.

You then asked me this:

But if the driver was designed for the larger box, wouldn't it be capable of higher output than a driver in smaller box?

I was a little confused as to exactly what you were asking. I assumed you were asking if a driver designed for a large box will play louder than a driver designed for a small box.

The whole point of the analysis was to show that even though the drivers i chose have similar specs (as harman and velodyne released. IE, vc size, RMS power, etc) their T/S parameters vary and the small box driver is capable of higher output.

I was pretty much saying, yes the Revel and Velodyne have similar specs, but we don't know the T/S parameters and therefore, unless they are the same, a larger box doesn't mean anything. A driver in a small box can best the driver in a large box.

I apologize for the confusion.

 

[monkish54]

I was thinking about it, and one of the comments I remember reading in Gene's review of the DD15 Plus reinforced my belief that increasing cabinet size was a good thing, and made me think that he thought a larger cabinet (and, of course, a driver with a greater xmax to take advantage of it) produced higher output:

It appears he does. His comment below is a bit confusing.

Velodyne claims their DD+ line of subs have between 4-5dB more output for each comparable model to the original DD series of subs. Based on the driver differences between the two products (and the fact that the new DD-15+ box volume has increased nearly 25%) we have little reason to doubt this claim, but of course we measured to confirm the results as you will read later in this review.

If the driver differences are any on this list, the max output would be higher: Xmax, sensitivity, SD (surface area), power handling.

Can someone with the appropriate technical expertise explain in prose how the relationship between cabinet volume in sealed enclosures and output really works?

To my knowledge, and all my WinISD musings, cabinet volume and output don't have much relation.

Enclosure volume for a sealed box simply determines the QTC..the system's overall Q (damping factor). A QTC of 0.707 gives the most extended response:

Shaping the Low-Frequency Response
Enclosing the back side of an open-back driver in a box does more than just prevent the rear low-frequency sound waves from mixing with and canceling the front. The box also has a strong influence on the quality of the sound. Let’s look at three examples. The graph below shows the amplitude response of three different boxes, each with the same model driver.


<center style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 11px; line-height: 14px;">

</center>
The green curve is considered by many speaker designers to be ideal. This is because the response is "maximally flat", meaning that the response stays level for as long as it can before dropping off. The reason why a "flat" response is considered the best is because it allows the speaker to produce sound waves that more closely match those of the original audio signal. This is what "high fidelity" is all about. Of course, there are times when you do not want a flat response. For example, an electric guitar speaker is used to create sound—not reproduce sound—so a non-flat response may be desired in order to give the guitar a desired sound quality.The red curve was created by putting the same driver in a box that was over 100 times bigger than the maximally flat box. In fact, the box was so big that it makes the driver behave as if it were mounted in a really huge wall. Speaker designers call this an "infinite baffle" design. While the use of such a large box extends the low-frequency response, it does so at the expense of loudness [At those frequencies, not overall maximum loudness] because the level begins to decrease much earlier than the maximally flat box. Plus, it will force the driver's diaphragm to move farther which will reduce the maximum power it can handle.
The blue curve was created by putting the same driver in a box that was about 25 times smaller than the maximally flat box. Such a small box has a very dramatic effect. It created a 9 dB response peak and caused the response to drop off very early. The large peak indicates that the speaker will have a large resonance. This means that the box will "ring" like a bell at frequencies within the peak. This will make the speaker sound louder at those frequencies but it will do so at the expense of transient response because any sudden sounds (like the beat of a drum) will no longer sound as distinct as they originally did.

If I took the same driver (as they did above) and stick it in different boxes, the knee of the response would change, but overall maximum output does not. When I say maximum output, I mean over the range of the sub, not at any specific frequency. Each box changed the -3db point of the system, but it did not change how loudly the sub can play from its -3db point up until its roll off.

Both the Revel and Velodyne had the same -3db point, but which has a greater max output from the -3db point up until, say 500hz when they begin to roll off? (The roll off point is just an example..who knows what it really is?) The greater maximum output is determined by some of the T/S parameters, not the box size. Most likely they both shot for a QTC of 0.707. That is the most sought for QTC.

If I want to increase max SPL for a given sub, as a designer there are a few things that can be done: greater xmax, higher sensitivity, more power handling, larger surface area of cone. All of these will increase my total SPL.

DId that help at all?

speaker basics

 

[Irvrobinson]

Revel has just published more specs on this thing. It's actually very interesting.

xmax: >44mm (Wow. That's much more than even the LMS5400. 44mm smells fishy, I wonder if there's a difference in how they're measured.)

Weight: 177lbs, with neodymium magnets. What the hell is in that box, lead lining?

It uses a separate 1KW amp for each voice coil.

They take a crack at Velodyne by calling out in the brochure that they don't need no stinking servos.

Maybe this thing really is the Salon2 of subwoofers.

 

[gene]

I was thinking about it, and one of the comments I remember reading in Gene's review of the DD15 Plus reinforced my belief that increasing cabinet size was a good thing, and made me think that he thought a larger cabinet (and, of course, a driver with a greater xmax to take advantage of it) produced higher output:

Can someone with the appropriate technical expertise explain in prose how the relationship between cabinet volume in sealed enclosures and output really works? I ask because now I feel confused by what I thought was the case, while I may have been clearly mistaken.

(Perhaps I should stop being so damned lazy and finally just study speaker design.)

The bigger box volume increases the natural HPF of the system so at lower F the system requires less power to hit the same SPL levels. So below the corner frequency is where you'll see the big change in efficiency and a reduction in required power to achieve the same SPL level. Hope that helps.

 

[Irvrobinson]

The bigger box volume increases the natural HPF of the system so at lower F the system requires less power to hit the same SPL levels. So below the corner frequency is where you'll see the big change in efficiency and a reduction in required power to achieve the same SPL level. Hope that helps.

That's what I thought, but monkish54 seems less convinced. Or based on a PM he sent me, maybe he is now.

Once my Revel dealer gets one of these in his showroom perhaps I'll take a first-hand look. He's also a Velodyne dealer so seeing this thing side-by-side with the DD18 Plus might be interesting.

 

[monkish54]

xmax: >44mm (Wow. That's much more than even the LMS5400. 44mm smells fishy, I wonder if there's a difference in how they're measured.)

There are two ways to measure xmax. I assume one is FAR more popular than the other:

1. (VC length - gap length)/ 2
2. Measure how far the driver can be displaced before distortion starts to occur. (Generally the point used is 70% of the BL figure.)

Anyway, i wouldn't say it's fishy. The LMS certainly doesn't have the most Xmax of any sub...it's very balanced.

RE Audio XXX15D2 (XXX15-D2) 15" Dual 2 ohm Car Subwoofer

Also, beware when you see P-P on a specification sheet. Xmax is one-way travel of the coil, hence dividing by 2, not peak-peak.

Maybe this thing really is the Salon2 of subwoofers.

Could be. Harman has a really sweet DVC motor design. I wouldn't put too much stock into xmax, though. Xmax is most important in a sealed enclosure (is the Revel sealed or ported?), and I will always give up a little bit of xmax and good chunk of power handling for increased sensitivity. Power compression can be DEADLY for a sub. More power goes into a subwoofer than any other type of driver, and they are also played the loudest among users. You can lose a large chunk of SPL to VC heat! How can i control compression? Put less power into the driver. Sure the XXX 15 has a billion mm of xmax, but its also very insensitive for a sub. I'm going to have to use a lot of power, and i'm going to lose SPL because of it.

To be fair, power handling is vastly important. If i could look and say this VC and former will take this much power before compression occurs, i would seldom trade power handling. Unfortunately, power handling specs are usually: your **** will melt if you give it any more power --it's just too hot for the coil.

 

[Irvrobinson]

The Revel is sealed.

They specifically call it xmax, so I assume they're not doing the peak-to-peak cheat.

 

[monkish54]

That's what I thought, but monkish54 seems less convinced.

I completely agree with Gene. It would be silly not to, as what he is saying is easy to test and even demonstrated in that little graph I posted.

We're talking about two different things. I'm not talking about the system playing lower frequencies, but its entire range from -3db (F3) up to frequency X. If I tune the system to a QTC of 0.2 it'll play lower frequencies louder with less power. If you look at the graph I posted, you’ll see the 0.2 system is playing 5hz-70hz louder than the other systems. This can be used to one’s advantage. I was talking about overall maximum volume at all frequencies in the sub's range, not what the Knee of the response looks like.

The box size changed the F3, changing how loudly certain frequencies played. I was talking about how loudly one sub will play vs another, when the F3 is the same. i.e. Revel vs Velodyne.

Crossover's have total Q as well. A LR filter has a Q of about 0.5

 

[Hocky]

Revel has just published more specs on this thing. It's actually very interesting.

xmax: >44mm (Wow. That's much more than even the LMS5400. 44mm smells fishy, I wonder if there's a difference in how they're measured.)

Weight: 177lbs, with neodymium magnets. What the hell is in that box, lead lining?

It uses a separate 1KW amp for each voice coil.

They take a crack at Velodyne by calling out in the brochure that they don't need no stinking servos.

Maybe this thing really is the Salon2 of subwoofers.

That is the ballpark xmax and significantly under the weight of the JL F212. I am interested to see its performance. It looks better than a 212 for sure.

 

[monkish54]

BTW, here is the DD tech that Harman uses. They use it in quite a few drivers.

http://www.jblpro.com/BackOffice/ProductAttachments/technote_v1_n33.pdf

 

[Irvrobinson]

I completely agree with Gene. It would be silly not to, as what he is saying is easy to test and even demonstrated in that little graph I posted.

We're talking about two different things. I'm not talking about the system playing lower frequencies, but its entire range from -3db (F3) up to frequency X. If I tune the system to a QTC of 0.2 it'll play lower frequencies louder with less power. If you look at the graph I posted, you’ll see the 0.2 system is playing 5hz-70hz louder than the other systems. This can be used to one’s advantage. I was talking about overall maximum volume at all frequencies in the sub's range, not what the Knee of the response looks like.

The box size changed the F3, changing how loudly certain frequencies played. I was talking about how loudly one sub will play vs another, when the F3 is the same. i.e. Revel vs Velodyne.

Crossover's have total Q as well. A LR filter has a Q of about 0.5

Frankly, I don't know what you're talking about anymore.

 

[jinjuku]

Revel has just published more specs on this thing. It's actually very interesting.

xmax: >44mm (Wow. That's much more than even the LMS5400. 44mm smells fishy, I wonder if there's a difference in how they're measured.)

Peak to Peak?

 

[Irvrobinson]

Peak to Peak?

They call it xmax, and Harman is usually pretty good about definitions, but I wondered if there were differences in how xmax could be measured. Like perhaps where the driver is near linear and where it isn't. Not that I'm any sort of expert here, but I don't ever think I've seen a driver spec'd with an xmax that large. Watch, monkish will now produce a list of eight of them.

 

[monkish54]

You first said this.

I think even the Revel has a good chance of beating the Velodyne, because it has a very similar driver and amplifier specs, but a larger cabinet volume.

Then I asked this:

Have you seen the T/S parameters?

I asked about the T/S parameters, because unless they were the same, the boxes would have​ to be different sizes to reach a certain desired QTC.


I went on to say this:

In fact, unless Revel is stupid (which they are not) a larger box will hurt performance and give a wonky response.

I said this because both systems have the same F3, and most likely a QTC of ~.707. The larger cabinet volume was needed to reach the QTC of ~.707, the QTC didn't change. Because the QTC didn't change, neither did the knee of the response.

To be fair, we don't know for certain that they went with .707, but the odds are very, very good.

But if the driver was designed for the larger box, wouldn't it be capable of higher output than a driver in smaller box?

I replied to this question with my WinISD analysis.

The driver was designed to reach a certain QTC in a certain size box. Look up any sealed box calculator, it will ask you for the desired QTC.

To rephrase your question a little:

If the driver was designed to reach a QTC of .707 in a larger box, wouldn't it be capable of higher output than a driver [designed for] a smaller box? The answer would be "no".

To clarify now, if I were to lower the QTC of my system, say, 0.2 from 0.707, the lower frequencies after Fs (resonant frequency) will be higher in level. BUT the subwoofer system would not be capable of higher output over it's range (-3db to rolloff) just because it's in a large box.

To sum up, box changes F3, but does not change the maximum output of the subwoofer system over the entire range. Again, range meaning F3 to rolloff.

Frankly, I don't know what you're talking about anymore.

Better?

 

[jinjuku]

They call it xmax, and Harman is usually pretty good about definitions, but I wondered if there were differences in how xmax could be measured. Like perhaps where the driver is near linear and where it isn't. Not that I'm any sort of expert here, but I don't ever think I've seen a driver spec'd with an xmax that large. Watch, monkish will now produce a list of eight of them.

With it being new just wondered if it's a typo of sorts.

 

[monkish54]

Watch, monkish will now produce a list of eight of them.

Haha! I only have 7 left to go!

http://forums.audioholics.com/forums/subwoofers/83794-revel-reintroduces-their-$10-000-sealed-18-sub-3.html#post944353