Learning about subwoofer specs

[ryanosaur]

Hi All!

I've read the sticky Subwoofer Terminology post and feel mostly cool with the terminology and meanings... As well as the Bassaholic Protocols, and feel comfortable, in a novice way, with what's going on.

What I haven't found is an explanation for interpreting the common specs seen when researching subs: what they represent in terms of performance, how to compare/contrast different data, and which are truly useful vs. which are obscure points that don't really have much real-world bearing.

For example, I asked about sub SPL the other day. I get Sound Pressure Level, but as it applies to a sub spec: is this a maximum? Is it an average? if one sub is rated at 120dB, how does it surpass Bassaholic threshold of 123dB? (And I do get that some key parameters might surpass, but...) Hell, how do I interpret the CEA charts? (An example using SVS PC 4000: don't recall where I saw the chart, but best I understood, it only rated around 115dB.)
Xmax and Excursion refer to the movement of the driver with Xmax being the forward range and Excursion/Xmech being total movement range... but how does that apply to real world potential for "massaging my spleen?" Or does it? (And if I'm getting those wrong, pls let me know!)

In other words, when I'm researching subs, other than just rolling the dice and ordering two up that I might have to ship back... how do you start to make an educated guess about potential performance?

Pedantry is accepted. Patient guidance is appreciated. A free four-pack of PB16 Ultras is welcome.

Thanks in advance for helping me on my path!

Best,
R

 

[WaynePflughaupt]

I would say that SPL ratings are maximum. When you think about it, an “average” rating doesn’t make any sense.

I don’t know what CEA charts are.

As far as Xmax and excursion, that’s mostly relevant to people building a sub, not the end user. A bigger Xmax generally is considered better but pro audio subs have limited Xmax, but nevertheless can seriously slam you in the chest.

Regards,
Wayne A. Pflughaupt

 

[Verdinut]

I would say that SPL ratings are maximum. When you think about it, an “average” rating doesn’t make any sense.

I don’t know what CEA charts are.

As far as Xmax and excursion, that’s mostly relevant to people building a sub, not the end user. A bigger Xmax generally is considered better but pro audio subs have limited Xmax, but nevertheless can seriously slam you in the chest.

Regards,
Wayne A. Pflughaupt

Most Pro audio subs have limited xmax as they are not required to reach frequencies below 30-35 Hz. They have a higher fs than audiophile subs and have stiffer suspensions than their hi-fi counterpart.

IMO, a good pro audio driver will handle up to 4 times its published power rating for a fraction of a second, provided that the moving mass is well loaded by the enclosure design within its frequency range. However, that is not the situation with audiophile speakers.

 

[lovinthehd]

Hi All!

I've read the sticky Subwoofer Terminology post and feel mostly cool with the terminology and meanings... As well as the Bassaholic Protocols, and feel comfortable, in a novice way, with what's going on.

What I haven't found is an explanation for interpreting the common specs seen when researching subs: what they represent in terms of performance, how to compare/contrast different data, and which are truly useful vs. which are obscure points that don't really have much real-world bearing.

For example, I asked about sub SPL the other day. I get Sound Pressure Level, but as it applies to a sub spec: is this a maximum? Is it an average? if one sub is rated at 120dB, how does it surpass Bassaholic threshold of 123dB? (And I do get that some key parameters might surpass, but...) Hell, how do I interpret the CEA charts? (An example using SVS PC 4000: don't recall where I saw the chart, but best I understood, it only rated around 115dB.)
Xmax and Excursion refer to the movement of the driver with Xmax being the forward range and Excursion/Xmech being total movement range... but how does that apply to real world potential for "massaging my spleen?" Or does it? (And if I'm getting those wrong, pls let me know!)

In other words, when I'm researching subs, other than just rolling the dice and ordering two up that I might have to ship back... how do you start to make an educated guess about potential performance?

Pedantry is accepted. Patient guidance is appreciated. A free four-pack of PB16 Ultras is welcome.

Thanks in advance for helping me on my path!

Best,
R

How do you do with speaker specs and measurements?

 

[Verdinut]

Hi All!

I've read the sticky Subwoofer Terminology post and feel mostly cool with the terminology and meanings... As well as the Bassaholic Protocols, and feel comfortable, in a novice way, with what's going on.

What I haven't found is an explanation for interpreting the common specs seen when researching subs: what they represent in terms of performance, how to compare/contrast different data, and which are truly useful vs. which are obscure points that don't really have much real-world bearing.

For example, I asked about sub SPL the other day. I get Sound Pressure Level, but as it applies to a sub spec: is this a maximum? Is it an average? if one sub is rated at 120dB, how does it surpass Bassaholic threshold of 123dB? (And I do get that some key parameters might surpass, but...) Hell, how do I interpret the CEA charts? (An example using SVS PC 4000: don't recall where I saw the chart, but best I understood, it only rated around 115dB.)
Xmax and Excursion refer to the movement of the driver with Xmax being the forward range and Excursion/Xmech being total movement range... but how does that apply to real world potential for "massaging my spleen?" Or does it? (And if I'm getting those wrong, pls let me know!)

In other words, when I'm researching subs, other than just rolling the dice and ordering two up that I might have to ship back... how do you start to make an educated guess about potential performance?

Pedantry is accepted. Patient guidance is appreciated. A free four-pack of PB16 Ultras is welcome.

Thanks in advance for helping me on my path!

Best,
R

If you want to know more about loudspeakers and their specs, I would suggest Vance Dickason's "Loudspeaker Design Cookbook" a comprehensive and well detailed book that explains speaker driver construction, specs and also contains plans to help you complete a DIY Home Theater Speaker System:

https://www.amazon.com/Loudspeaker-Design-Cookbook-Vance-Dickason/dp/1882580338/ref=sr_1_1?ie=UTF8&qid=1539740909&sr=8-1&keywords=loudspeaker+design+cookbook&dpID=514AaEuy%2B4L&preST=_SX218_BO1,204,203,200_QL40_&dpSrc=srch

 

[ryanosaur]

How do you do with speaker specs and measurements?

I've spent more time looking at speakers than subs.
Sensitivity for speakers... but I don't think I've seen it on a sub spec. Some speakers i've seen max SPL listed, but for subs, just the ambiguous SPL spec (but not always). (Always a possibility i've missed something, too. )
Don't really hear about the movement of a tower's woofer, but as I said before, I understand what Xmax and Xmech means... and can infer that the greater range of motion implies the movement of more air (i.e. more pressurization?).
Frequency response... um. oh ya. shouldn't be posting if I don't get that.
With speakers you get the RMS and maybe recommended amplification. With Subs you get the Amp rating for whats installed.
I'm sure subs come in different impedance, but as all active subs have their own amp, I can see why I haven't seen that listed.

I feel like I can look at a speaker spec sheet and know in theory how it should fit into a given system. Obviously, not how it sounds, but... With subs, I'm still working out how to identify the important characteristics that will say to me: "look closer," or "move along."

Does that make sense, Lovin?

 

[Steve81]

What I haven't found is an explanation for interpreting the common specs seen when researching subs: what they represent in terms of performance, how to compare/contrast different data, and which are truly useful vs. which are obscure points that don't really have much real-world bearing.

First its worth differentiating between manufacturer specifications and 3rd party measurements as done here and at data-bass among other places. Manufacturer specs by and large have limited value. For example, some manufacturers list a frequency response spec without being bounded by the usual +/-3dB tolerance. Total garbage. Even with that tolerance listed, another question arises: can the subwoofer maintain it's rated response as the volume goes up? In most cases, particularly with small sealed subs that are EQed flat down to 20Hz or so, the answer is a resounding no. Manufacturer rated output also tends to be sketchy at best. It's easy to just throw out a number without any qualifiers, and bigger numbers are generally better for marketing purposes.

Hell, how do I interpret the CEA charts?

CEA charts are (in theory) supposed to represent the maximum clean burst (i.e. not continuous) output of a subwoofer by frequency, in 1/3rd octave steps. Higher numbers are generally better, but there are some qualifiers.

1. How the output number is reported, i.e. peak vs RMS, output scaled to 1 meter or 2 meters. The CEA standard calls for 1 meter, peak; however, 2 meters, RMS is also commonly used, which reduces the output number by 9dB (3dB for peak to RMS, 6dB for 1 meter to 2 meters). IOW, 114dB @ 2m, RMS = 123dB @ 1m, peak. At AH and data-bass, 2m, RMS is usually what's reported, but the bassaholic ratings and manufacturers like Hsu and PSA utilize 1m, peak.

2. Different testers, with different rigs, under different measuring conditions can and do yield different results.

3. With respect to that "in theory" part, CEA tests are bounded by distortion. However, a subwoofer may be misbehaving before it reaches that threshold, i.e. mechanical noises, port chuffing, etc.

Xmax and Excursion refer to the movement of the driver with Xmax being the forward range and Excursion/Xmech being total movement range... but how does that apply to real world potential for "massaging my spleen?" Or does it? (And if I'm getting those wrong, pls let me know!)

Xmax is ostensibly the maximum linear excursion of the driver, and supposed to be reported as center to peak, vs peak to peak. It and Xmech (max excursion before physical damage) are useful information if you're looking to DIY, but not something I'd get wrapped up in if you're looking at finished products ala the PB16U. The end results are all that matter there.

In other words, when I'm researching subs, other than just rolling the dice and ordering two up that I might have to ship back... how do you start to make an educated guess about potential performance?

As with most things, you start off with the basics (room size, performance goals),and work from there. In that respect, the Bassaholic ratings are a fair starting point for respectable (albeit not spleen massaging) performance. Still, it's complicated because we only have meaningful control over one side of the equation: the subwoofer. The room is a huge X-factor as it can affect subwoofer performance in unpredictable ways. Of course, there are other issues as well, i.e. integration between the subs and other speakers.

 

[ryanosaur]

If you want to know more about loudspekers and their specs, I would suggest Vance Dickason's "Loudspeaker Design Cookbook" a comprehensive and well detailed book that explains speaker driver construction, specs and also contains plans to help you complete a DIY Home Theater Speaker System:

https://www.amazon.com/Loudspeaker-Design-Cookbook-Vance-Dickason/dp/1882580338/ref=sr_1_1?ie=UTF8&qid=1539740909&sr=8-1&keywords=loudspeaker+design+cookbook&dpID=514AaEuy%2B4L&preST=_SX218_BO1,204,203,200_QL40_&dpSrc=srch

That could be fun. Reading the Harley book right now, FWIW. The big one. Dunno that I'm gonna ever DIY it for speakers, though my dad did, but he was also an EE for McDonnell Douglas after he graduated. But again, I love digging into this and want the details to make more sense. Sure I can always just order up, plug it in and see how it does. But... I wonder what the carbon footprint is for sending two X-13s back to Outlaw from Norcal?

I was also thinkin' my next book should be a refresher course on basic electricity! Been way too long.

Thanks Verdinut!

 

[lovinthehd]

I've spent more time looking at speakers than subs.
Sensitivity for speakers... but I don't think I've seen it on a sub spec. Some speakers i've seen max SPL listed, but for subs, just the ambiguous SPL spec (but not always). (Always a possibility i've missed something, too. )
Don't really hear about the movement of a tower's woofer, but as I said before, I understand what Xmax and Xmech means... and can infer that the greater range of motion implies the movement of more air (i.e. more pressurization?).
Frequency response... um. oh ya. shouldn't be posting if I don't get that.
With speakers you get the RMS and maybe recommended amplification. With Subs you get the Amp rating for whats installed.
I'm sure subs come in different impedance, but as all active subs have their own amp, I can see why I haven't seen that listed.

I feel like I can look at a speaker spec sheet and know in theory how it should fit into a given system. Obviously, not how it sounds, but... With subs, I'm still working out how to identify the important characteristics that will say to me: "look closer," or "move along."

Does that make sense, Lovin?

It's a start. Sensitivity for complete systems (i.e. an active sub) is often not mentioned, more a diy thing for matching amp. Same for impedance to an extent, as in an active system it's already taken care of with the supplied amp. Typical sub is 4 ohm, tho. DIY subs you can vary how you wire dual voice coil impedance combos for different amp applications.

The more displacement the more air a sub can move, simplest way to do this is diameter/cone area but excursion certainly can play a factor, again more a thing when designing sub rather than buying one.

Subs as far as amp power is mostly about trying to impress you with a bigger number, as without other information the wattage alone is not meaningful (is it at 4 ohm? 2 ohm? what raange with what distortion? what's the sensitivity of the system?)

Have you looked around in detail at data-bass for information and measurements? Better than manufacturer information, just not a complete listing as Josh only has so much time and subs donated for testing....

 

[ryanosaur]

Have you looked around in detail at data-bass for information and measurements? Better than manufacturer information, just not a complete listing as Josh only has so much time and subs donated for testing....

Ya, you turned me on to them... not the best of friends, yet, but I'm checking in when I can to read more as I can.

But Damnit Man! More Subs! More Third Party Testing! HA!

Just like when we were talking amps before, I get that most of what I've settled on will work great. "Settled" is a bad word: I know I would be happy with Outlaw, Hsu, SVS, I'm getting to know Rythmik and ya, they'd be solid too. And the monolith 15" would rock. (I think I just need to see a change in their image and service first.) (But I buy their wires, banana plugs, etc.)

 

[lovinthehd]

Ya, you turned me on to them... not the best of friends, yet, but I'm checking in when I can to read more as I can.

But Damnit Man! More Subs! More Third Party Testing! HA!

Just like when we were talking amps before, I get that most of what I've settled on will work great. "Settled" is a bad word: I know I would be happy with Outlaw, Hsu, SVS, I'm getting to know Rythmik and ya, they'd be solid too. And the monolith 15" would rock. (I think I just need to see a change in their image and service first.) (But I buy their wires, banana plugs, etc.)

I think once you're in the general performance area for your space, spl and extension goals, the subs are going to be more similar than different and it becomes more a matter of picking what's available at a good price for ya! I'd just say gather as much information and compare measurements (keeping in mind they may not be on the same basis as mentioned earlier) to get comfortable with the finalists in your search.

 

[ryanosaur]

Steve81,
Thank you! I know experience will make a world of difference. I think its a little silly that so many things are treated differently in the audio world. Marketing schemes aside, I know I don't need an 1800w amp in a subwoofer, and admittedly, when I see that, I want to know why. Of course, it also makes me take a little longer look.
Truth be told, I'm not looking for an internal audio massage, or in quest of the mythical brown note... (though i did stumble on a conversation somewhere about some rare pipe organs with 64'ers, and one person saying he did feel a little queasy during the recital.)
Lovin may recall... I'm dealing with 8312.5'3 room. So I do need extreme rated subs per the Bassaholic specs. And I do want 16Hz extension for pipe organ reproduction. So as I do my due diligence, I want to make certain I 'get' what I'm seeing, before wasting excessive time, or worse, money, on something a more experienced tech-head might see as obvious.

Cheers!

 

[KEW]

But... I wonder what the carbon footprint is for sending two X-13s back to Outlaw from Norcal?

IMHO, this is not really an issue. Any of the subs recommended on this forum such as Rythmik, Outlaw, Hsu, PSA, SVS, etc. is going to be capable as long as you are considering your room size. Also the CS from ID sub companies is great. They will be honest with you about sizing for your needs. And, of course, the guys here will also.
After room size/SPL capability, comes the question of how flexible is the sub? I bought a pair of JL Audio e112's expecting them to be excellent sealed subs for use with music. However, JL Audio tuned them to be flat to ~20Hz in an anechoic chamber and once I put them in a standard sized LR and close to a wall, room gain turned them into a boomy, muddy mess. Audyssey could not do enough to correct them! I suspect I could have got them right with miniDSP, but I hate the idea of paying a ton for the low frequency capability them having to buy additional gear to reverse that capability. The e112's had no built-in ability to tune them.
I may be a bit more sensitive to that problem than many, but as long as the subs you are considering can be tuned (they all have different names, but variable port tuning and adjustable EQ curve options, damping levels, room compensation, frequency extension, Q values, etc. provide this function) you should be able to get them in a range that Audyssey can work with. If not, it is probably more your room's fault than the sub and you will need to look to sub placement and perhaps a mini-DSP because I would not expect switching from Outlaw to Hsu (for example) to solve the issue. At the low frequencies, your room is often what you hear more than the sub and you need to tune the sub to the room.

Regarding refreshing electronic theory, that's great, but if your objective is to get to the best Sound Quality, getting a microphone and learning to use REW to measure your system is a more direct path to your destination (you can always back-fill the electronic theory later if you like).

 

[ryanosaur]

Regarding refreshing electronic theory, that's great, but if your objective is to get to the best Sound Quality, getting a microphone and learning to use REW to measure your system is a more direct path to your destination (you can always back-fill the electronic theory later if you like).

I had a newbie post where I was asking exactly that question: What tools I need to start playing at that level!

That said, I hear you and agree whole-heartedly re: these companies like Outlaw, Hsu et al. Even Monoprice would probably just require more patience to deal with what I guess to be a more bureaucratic culture. (Patience, a righteous attitude, and perhaps a bulldozer if necessary.)

 

[KEW]

I had a newbie post where I was asking exactly that question: What tools I need to start playing at that level!

Ha! I missed that thread, but they gave you the same answer plus a mini-DSP (which is a good addition)!

 

[ryanosaur]

Ha! I missed that thread, but they gave you the same answer plus a mini-DSP (which is a good addition)!

Anything else I should consider? Tool-wise, that is?

 

[KEW]

Anything else I should consider? Tool-wise, that is?

No, the mini-DSP is one hell of a flexible tool for tuning your system.
The USB mic and REW will allow you to measure your setup and mini-DSP will allow you to tune it. The other tool is Audioholics to help you interpret your measurements and make sure you don't try to aggressively EQ/boost a null (room mode)!

 

[shadyJ]

Steve81 gave very good answers to these questions. To reiterate what has already been said, "max SPL" as a spec means nothing. Unless the manufacturer specifies exactly what they mean, with exact conditions for that specification, it is totally useless.

One other thing to add on to Steve's answer about CEA-2010 is the base 20 logarithmic scale of decibels. Most people don't have a clear idea about how these numbers relate. If you want to compare CEA-2010 numbers, consider that a 6 dB increase is a doubling of output. So if you had one subwoofer, and put an identical sub next to it with the same volume level, you would get a 6 dB gain. A 3 dB increase is nearly a 50% increase in output. A 9 dB increase would be roughly a tripling of output, and a 12 dB increase would be a quadrupling. So if subwoofer A had a 12 dB advantage over subwoofer B in a CEA-2010 measurement, that means that it would take four subwoofer Bs to equal the output of subwoofer A, at least for that frequency in the CEA-2010 measurement.

 

[ryanosaur]

No, the mini-DSP is one hell of a flexible tool for tuning your system.
The USB mic and REW will allow you to measure your setup and mini-DSP will allow you to tune it. The other tool is Audioholics to help you interpret your measurements and make sure you don't try to aggressively EQ/boost a null (room mode)!

You, Sir Kew, earn some horns. Rock On!

Thank you!

 

[ryanosaur]

Steve81 gave very good answers to these questions. To reiterate what has already been said, "max SPL" as a spec means nothing. Unless the manufacturer specifies exactly what they mean, with exact conditions for that specification, it is totally useless.

One other thing to add on to Steve's answer about CEA-2010 is the base 20 logarithmic scale of decibels. Most people don't have a clear idea about how these numbers relate. If you want to compare CEA-2010 numbers, consider that a 6 dB increase is a doubling of output. So if you had one subwoofer, and put an identical sub next to it with the same volume level, you would get a 6 dB gain. A 3 dB increase is nearly a 50% increase in output. A 9 dB increase would be roughly a tripling of output, and a 12 dB increase would be a quadrupling. So if subwoofer A had a 12 dB advantage over subwoofer B in a CEA-2010 measurement, that means that it would take four subwoofer Bs to equal the output of subwoofer A, at least for that frequency in the CEA-2010 measurement.

Hi Shady! It was your comment before that spurred me on to ask this. How do I sift the chaff, or better yet, How do I recognize there is chaff to sift?