10hz nearfield, possible? Impractical? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 10 Old 07-18-2019, 07:37 PM - Thread Starter
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My system right now plays to 18hz and I am surrounded by concrete and I know the <20hz thing gets to be expensive which makes me wonder if making some really low tune nearfields worth it or not. My first thought is trying 8 of the sealed $30 12” but it sounded like you still need a ton of eq. I’ve also read that some are porting down to 15hz with luck. I do like the though of sealed better but what would it take to accomplish a 10hz (or around 10hz) nearfield setup? I would think that its not that hard being nearfield you shouldn’t need a lot of power for a sealed setup, I mean the speaker is right next to you, right? My dual 20hz VBSS’s are on a cheap 500w plate amp and the gain is hardly over half, I’m not complaining about them and actually they play really well but I thought if I do replace/upgrade them I’m wondering what it would take? Or if it’s even worth the hassle just for nearfields. BOSS and buttkickers are out of the question until I upgrade my seating. I thought 10hz firing into my back would be fun, so here lies the question, what would you do?

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post #2 of 10 Old 07-18-2019, 09:29 PM
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I've been rocking flat to 5hz NF for 8 years now (although I run a +20dB house curve lol). It's freaking tons of fun!!!! I used 21's at first and now am running 24's (honestly, the 21's were more than enough!) Get some sealed drivers, give them some power and thats about it really. Just have to get something capable of actually going that low with authority.
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post #3 of 10 Old 07-18-2019, 09:37 PM
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Sealed drivers rolloff too much nearfield so you need enough excursion and a boost down low, or as mentioned, a house curve boosting under 20hz and lower. I had two dual ported 18s tuned to 7hz NF at one time.

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post #4 of 10 Old 07-19-2019, 03:58 AM
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If it were me, I'd choose a more capable driver.
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post #5 of 10 Old 07-19-2019, 01:37 PM
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While for the most part I agree with johnson636 it still comes down to displacement, $, and space. I didn't care about $ but space I did. So I couldn't do anything more than a 15" driver behind me and most 15's aren't worth what they charge compared to the 18's out there today and their depth is usually close. So I got 16 of those JBL's in a 12" deep cab and they fire into my couch from no more than 2" away and there's nothing like it. Yes 10hz and below is pretty awesome even near-field with pretty much no room gain.

The drivers cost me $480 and I bought a clone for $800. IIRC they can do around 108db at 10hz. 8 would be 102db at 10hz. That's roughly 26 liters of air, or 13 for 8. So give or take 2-4 UM 18's or 1-2 24's would equal or better that but still cost a good bit more. Though the wiring would be much easier. Just depends on your limits and budget. I will say another 6db down at I'd say 25hz and below makes a huge difference compared to the higher frequencies so IF you can do more than 8 I would, and if not, like johnson636 said go with a more capable driver.
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post #6 of 10 Old 07-19-2019, 01:52 PM
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8 of the JBL's won't be enough, although you'll like it. I'd do 16, wire as a 4 ohm load, make the enclosure as large as you can stand but at least 1.5 cuft per driver, and be ready for a lot of signal shaping. You're going to get a TON of tactile response and the drivers will definitely do it. I have a dozen nearfield and they'll get 'er done.

Compared to an ultimax, it takes between 3-4 JBL's to match, depending on at what freq. 4 JBL's beat an ultimax anywhere. 16 of them distributes the electrical load across a lot of voice coils, you gain quite a bit with that much cone area. My nearfield experiment caused me to abandon my large diameter sub drivers and just go with a zillion 12's.

BTW JBL's sound fantastic. One of my favs, especially in large droves. I choose them because I like them, not for budget reasons.
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post #7 of 10 Old 07-19-2019, 01:55 PM
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your digging a rabbit hole. just cause somethings can measure well doesnt mean they will sound well....no matter what the gods say.

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post #8 of 10 Old 07-19-2019, 01:58 PM
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Response of DIY forum when somebody asks if something is "impractical".

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post #9 of 10 Old 07-19-2019, 03:12 PM
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The boss is so cheap you could toss it when the new seating comes. The wobble is more important at that point than trying to spl. Or spend the money and get Crowsons
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post #10 of 10 Old 07-19-2019, 06:19 PM
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Quote:
Originally Posted by torii View Post
your digging a rabbit hole. just cause somethings can measure well doesnt mean they will sound well....no matter what the gods say.
Huh?
99% of the time if something measures well, it will sound good...
and if it measures poorly, it will sound horrible.
(and by "good" I mean: low THD with/at extended bandwidth and higher-ish SPL.)

Being flat to 1-10hz is one thing. Having enough horses to feel it or make it audible without gross distortion is a whole 'nother level...
The act of measuring is merely another tool, numbers on a page, explicitly nothing more per-se...

Subjectives will always be subjective, hard to validate or invalidate with scientific rigor; hence why they are formally avoided like the plague. (Example: Until we have a "ghost detector" that actually WORKS with 90's confidence, we can't tilt in either direction on the topic, maybe they exist and maybe not. etc etc...)

We HAVE sound detectors though, they are called measurement mics, and they work VERY WELL. Often better than human hearing, and a LOT BETTER than guesswork and opinions.
If the room has a null, or if the box is made of cardboard or if the driver is an 8 vs a 24, it will show differences in the measurements. It will tell you exactly what frequencies, THD and SPL (for a sub in a given spot, for a mic in a given spot...) It will show how close the box-model match reality, especially when measured anechoically or GP outside.

Quote:
Originally Posted by Audiophile75 View Post
My dual 20hz VBSS’s are on a cheap 500w plate amp and the gain is hardly over half. what would you do?
PA-460's don't like to be ported below ~22hz, the box gets too big and the mid-bass suffers greatly from energy distribution.
Given your budget, I'm not sure what the answer to your question is. My gut says it might be time to add sealed UM-18's if THAT is your true goal (or SI-24's if you really want to burn through the money quicker).

But as was pointed out already, nearfield doesn't get the free room-gain at low frequencies. The reflections need the space/time to actually reflect, for it to add the free db's. So this will make your task more-difficult.

FYI: thought has a t at the end...
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Last edited by BassThatHz; 07-19-2019 at 06:23 PM.
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