High powered sealed sub + room eq.

[camplo]

I come asking for some wisdom, in the area of sub-woofer implication. I want to upgrade my subwoofers a pair of ported 12" Kevlar woofers... The bass is respectable from current setup, but with best practice in mind, I would like to invest in improving performance in this area. The subs complete a system with 2-ways that take over after 200hz or so. Think three way with low xover point to the woofer and high xover point to tweeter.
I've heard of people using overpowered sealed subs to create really accurate systems. Sealed advantages for subwoofer performance; better impulse response, less delay, etc, and then the short comings; less bass extension as opposed to ported systems, so with an over powered sealed sub, we use room correction eq to extend the range of the subwoofer, which is only possible with a luxury of amp headroom and sub xmax.....
This is for studio monitoring, so application is of concern, just wondering is this a good idea for what I'm looking to do. I'm not sure how powerful of sub system I would want, 500rms8ohms per sub (2 subs) is a good starting point I think. I know of xmax calculators to help determine what type of driver specs to look for...Not sure which starting f3 is too high to try and extend with room eq...I'm hoping for some insight, correction if needed. I could always just build some nicer ported subs....I did like the novelty of the over powered room corrected seal sub....what do you guys think?
I am also open to product suggestions if you know of one that would suite my need.

[billfitzmaurice]

. Sealed advantages for subwoofer performance; better impulse response, less delay,.

That's not true. In blind testing EQ'd for identical response and trimmed for identical output one cannot tell if a sub is sealed or ported. The main advantage to sealed is that in a maximally flat alignment the enclosure can be much smaller than ported, at the expense of how low it will go. That can be compensated for by EQ and power if the driver has sufficient Pe and Xmax, but by and large where sealed is most appropriate is in smaller rooms where low frequency response is aided by cabin gain. By the same token in a small room a ported sub can have too much low end due to cabin gain. In short, small rooms and sealed subs are a good match, large rooms and ported subs are a good match. Small rooms and ported subs, large rooms and sealed subs, not so much.

[fpitas]

What Bill said. Also, 200Hz is a bit high to cross to subs, unless the subs are co-located with the satellites.

[wogg]

I've always preferred ported... but mostly because I've lack the will to spend the $ required for that extra power and Xmax in the woofers. Something about trowing extra power away into heat bothers me when I could just increase box size a little and add a port.

+1 on the 200Hz, that's too close to localization territory. Cross at 100, preferably lower.

Room EQ is good, but room setup and sub placement is better. Combine the two approaches, treat the space with bass traps and use multiple subs asymmetrically placed, then you'll need much less EQ to flatten for the mix position.

[camplo]

Thanks for the quick responses! The subs are "co-located" with the satellites, btw, basically a 3 way with the woofer in separate enclosure, "satellites:" sitting above subs, all speakers pointed at listeners head, typical studio set up. I sort of want to play devils advocate regarding the articles I've read suggesting that sealed subs present tighter bass.....but I've grown to trust the experience of the board so I'll just sit quietly and be thankful for the accessible and respectable knowledge of the members hear XD
If sound quality is not affected by whether ported or sealed then that opens my options...I could build 2 more subs but ooommmgggg the work...:::sigh:::..because of room acoustics multiple subs is going to get me better sound quality than upgrading the quality of the current subs is what I'm gathering...but I'm sooo tired lol. Maybe I'll a buy a pair of built subs. Either way, thanks for the help.

[fpitas]

Thanks for the quick responses! The subs are "co-located" with the satellites, btw, basically a 3 way with the woofer in separate enclosure, "satellites:" sitting above subs, all speakers pointed at listeners head, typical studio set up. I sort of want to play devils advocate regarding the articles I've read suggesting that sealed subs present tighter bass.....but I've grown to trust the experience of the board so I'll just sit quietly and be thankful for the accessible and respectable knowledge of the members hear XD
If sound quality is not affected by whether ported or sealed then that opens my options...I could build 2 more subs but ooommmgggg the work...:::sigh:::..because of room acoustics multiple subs is going to get me better sound quality than upgrading the quality of the current subs is what I'm gathering...but I'm sooo tired lol. Maybe I'll a buy a pair of built subs. Either way, thanks for the help.

Consider that not all ported enclosures are created alike. There are a great number of ways to align the port tuning, box size etc., so generally the designer can get the sound they want.

[djg]

If you're not into a lot of work, PE has some new sub kits with flat packs, with or without passive radiators, with or without plate amps.

[camplo]

For those of you inclined to play along. Lets say that I'm inclined to build or buy a sealed sub, which I intend on, extending bass response, with room eq. How do I even begin the endeavor. Off the top of my head, a 12" woofer needs something like ~13mm of xmax to produce 30hz at a decentely loud volume.....though I dont intend on listening super loud, I want the sub to be able to play full volume, undistorted, unstrainded (flat down to ~30hz or better). Those assumptions are based off an online xmax calculator for sealed enclosures vs spl vs freq. vs driver diameter. Sounds too simple though.

[wogg]

The physics is really that simple: how much air displaced at what frequency = a particular SPL. But... there's a lot of assumptions like listening distance, whole, half or quarter air space, room gain and geometry. So basically in a theoretical space and known distance, that's all you need to know. Sent from my SM-G960U using Tapatalk

[camplo]

Interesting, reading that reminded me that it did included listening distance as a variable. I was frustrated that it didn't include an output for amplifier needs. They did adjust for speaker sensitivity, but my understanding is lacking, so I can't figure it out, from that info alone. If speaker has a sensitivity of say 98db.....and I give it 100 watts in 8ohms how much spl does that equate at 3 ft.....someone of you could answer that. I cannot.

[fbov]

Sensitivity of 98 dB (@2.83v, 1m assumed) and an 8 Ohm impedance, so 2.83v gives you 1W of power.

100W amp power is 20dB (10x power = +10dB)

3 ft. ~ 1m, so no inverse square law correction needed (distance reduces sound level by 1/distance^2, so at 6 ft./2 m, you have 1/4 the SPL, or -6dB.)

Then, speaker + amp + distance = output level
98 dB + 20 dB - 0 dB = 118 dB

Note that this "ideal" calculation becomes inaccurate as soon as a reflecting surface contributes to the output... it under estimates sound levels in real rooms, but real rooms are complicated.

Perhaps you can describe your room (dimensions, shape, major features, wall construction, etc.) and we can suggest something. Many of us use woofer response simulators to experiment on paper to understand the tradeoffs. You'd need to get comfortable running such simulations if you wanted to design things yourself. If not, we can help.

Have fun,
Frank

[camplo]

Awesome, ty for sharing that. If I were to go to the lengths of having you guys or myself run a simulator of my room, it would be misleading of the purchase I want to make. I can't focus on my room, because its subject to change until I buy my own house, I'm not going to waste your time. Wogg suggested increasing sub count, which would for me, means adding 2 more subs, to equate to 4...I am not ruling this out, the less eq needed the better, and following best practices has been very rewarding for me.....then I look at my man cave/home studio and think.....2 more subs? The two new subs, I propose to invest in don't have to be identical to the ones I have, so I'll focus on the two new ones...If I want to use all 4.....I'll have them...if I just run two, they'll be better than the ones I currently have. So theres that.

12"-15", Sealed enclosure 3.5ft3 or smaller, Power range ~200watts, rms, 8ohms.....
I want my system to play flat down to 30hz at sweet spot. I run corrective room eq, so if the subs does not normally go that low, whether speaker or room... it will be extended using eq and amp headroom, which 200 rms should be plenty...
This is intended for sound engineering so best sound quality would be desired.
You guys know subs well and probably have some that you consider favorites....I trust you.....what are they =D

Heres what I think might be good
LaVoce WAF154.00 15" Subwoofer 8 Ohm
The Tm and sens is pretty high on this guy

The f3 of this sub in a sealed enclosure is 109hz....and the enclosure size is less than half a cubic foot so you can't even fit the stupid thing inside the optimal size box but according to this deal about sealed subs, and xmax calculators.....no matter what the specs say....if the subs has the required xmax to produce a certain frequency at a certain spl at a certain distance, in a certain room....the box's f3 is irrelevant somehow.

[billfitzmaurice]

That's a pro-sound driver. It trades off low frequency extension for sensitivity, so if you're building a speaker for your band or DJ PA it's worth looking at, but not for anything else. The specs are unsuited for a sealed alignment, especially Qes and Fs. The optimal box with maximally flat response isn't sealed, it's 1.4 cu ft ported with 38Hz Fb. Even then F3 is only 70Hz. That would make it OK, though not great, for electric bass, unsuitable for PA. As for the notion of using it in a Linkwitz Transform, in a sealed box of 0.7 cu ft (that's the correct size for a .7Q) with a 100Hz F3 flat response to 30Hz would require 20dB of boost. That means it would take 1000W at 30Hz to equal 10W at 100Hz. The driver Pe and Xmax are adequate to handle that, if you've got an amp that will deliver it. But a driver that has specs suited to a sealed box, like the UMax 15, in a still not unmanageable 4 cu ft cab could do it with a quarter that power, with much lower THD and higher displacement limited maximum SPL.
The reason for crossing over at 80 to 100Hz is that by doing so the subs and mains don't have to share the same footprint, which allows ideal placement of both subs and mains. If they do share the same footprint Allison Effect dictates that you're going to have a response dip where the wall is 1/4 wavelength behind the speakers. BTW, 'co-located' is a computer term, referring to having a number of system components in the same room. It has no application where acoustical engineering is concerned.

[camplo]

I think I'm finally getting the picture, thanks for that.
I was going to, first suggest, the UMAX 12" but I thought I was wrong....Its just as loud as the 15 and requires a smaller box I wouldn't know why the umax 15 would be better, maybe you can clue me in. The more I think about it, I am pretty much locked into crossing over at 200hz so that is to be considered.

[billfitzmaurice]

The UMax 15 isn't necessarily better, I just chose it to compare to the LaVoce 15. A UMax 12 in 3 cu ft sealed has a 32Hz f3, so in a tight room with the longest dimension no more than 18 feet it would be comfortable well down into the twenties. The reason to go with a 15 is the added displacement, if you need it.