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My Tempest sub is complete! But it's not what I expected...HELP!! (1 Viewer)

Aaron_Smith

Stunt Coordinator
Joined
Jul 22, 2002
Messages
105
Adire has a very good tech paper on setting up subs at their website; I would encourage you to read it, get an SPL meter, and give it a try. It will allow you to properly set your crossover frequency, phase, and gain on the amp.
Be patient... I finished my sub (mid Q sealed tempest) about a month ago, and I'm still tweaking like mad to get the right amp settings. But I'm finally to the point where all I'm hearing is beautiful, clean bass and the sub is acoustically invisible. Because of the shallow x-over slope of the PE 250watt plate amp, I've found that I have to set the cutoff below 55 Hz, otherwise voices and instruments bleed through. I may mod the sub amp to add a second 12db/oct. filter for a steeper rolloff.
For those of you who have used the Radio Shack SPL meter for setting up- are you using any sort of correction to account for the reduced meter sensitivity at lower frequencies?
 

Ryan Schnacke

Supporting Actor
Joined
Feb 5, 2001
Messages
876
A large portion of your subwoofer calibration signals will be in the 50-80Hz range. Its only off by 2dB in that range. And there are some things you can do perfectly fine without any meter correction. For example:

In my phase calibration method you only need to set the speakers and subwoofer SPL levels equal at a single frequency. And when you play them at the same time you only care that the result is 6dB louder than either by themselves. You don't care about absolute SPL levels or levels across a frequency range, just relative levels at a single frequency. Now if you're thinking of EQ'ing your sub or you'd like to get the accurate frequency response then ... how much do you trust those correction tables?

Adire's tech paper has some good stuff. But it really seems more oriented towards the person who actually uses the sub's built in filters. Step one for most of us is to turn the "crossover" knob all the way up (or disable it completely if possible). And they should have included an initial level-matching step to make the phase adjustment easier and more accurate. But you'd still want to set the level again at the end.
 

Jonny K

Second Unit
Joined
Dec 18, 2002
Messages
375
Ok, I just took the sub apart and swapped the +/-. No effect. I also tested each voice coil, and both of them work fine.
Yet it's still the same situation - DVD rocks at a low volume (any higher and it pops/distorts like crazy), and to get bass in TV/CD/Radio I've gotta crank up the volume.
Now one thing that occured to me was how the driver and ports are sealed to the box. First of all, the box is sealed super tight. All connections have been hot glued to make an excellent seal. But when it comes to the driver, I'm using this foam tape (which seems to have squished down to nothing), and around the ports I have nothing. Could that little bit make such a big difference?
Anyway, tomorrow I'm going to seal those up. Is it safe to say that this "Rope Caulk" will not dry in such a manner that I can't remove the driver anymore?
Thanks.
Jonny K. :frowning:
 

Keith Martin

Auditioning
Joined
Nov 12, 2002
Messages
12
OMG, you've got no seal around the ports!!!
We may have a winner!
Anyone else every use HOT GLUE for a box seal? Doesn't seem like a good medium for sealant to me. Traditionally something like silicone or "Liquid Nails" is used. Use these substances around your ports too.
 

Patrick Sun

Senior HTF Member
Joined
Jun 30, 1999
Messages
39,660
Single sided closed cell foam tape is what you'd want to use if you want a clean seal, otherwise, rope caulk is another good option.
 

Jonny K

Second Unit
Joined
Dec 18, 2002
Messages
375
Oh goodie! I hope that's the problem!!! Today I'll finish the seal, and I hope it'll work good then! :)
As for the hot glue, I'm pretty confident this stuff is air tight. It comes in stick form, you push it through a gun which heats it, and it comes out on the other end as a hot goop. I then liberally covered all the corners/seams/connections with this stuff, and it dried to a thick white silicon-looking seal. My dad says this box could hold water it's so tight.
Jonny K. :)
 

Dustin B

Senior HTF Member
Joined
Mar 10, 2001
Messages
3,126
The issue with the hot glue will be the seal over time. Silcon and closed cell foam are flexible. They won't crack under the vibration of a sub while hot glue, which dries hard, likely will.
 

Bryan Michael

Supporting Actor
Joined
Mar 2, 2002
Messages
564
i onec used this black stuff to seal a box. you installed the driver than put the top on the box it was bandpass box. i used hot glew gun once to seal a box. i was 15 and started to buld my own car box. it took alot of glew and sucked now i use a pure sicilone cauck or a 80-90% siclon cauck next week i am getting my mdfb to buld my 700l sub
 

Jonny K

Second Unit
Joined
Dec 18, 2002
Messages
375
Hmmm...

Well I guess I'll just have to see how it turns out.

Anyway, I finished sealing the bottom of the box. Both the ports were sealed with silicone, and the driver sealed with this kinda tar-like tape stuff. Really sticky gooey stuff. I'm sure it's all air tight now.

Yet the sub performs the same. Since I've pretty much tried everything, maybe there's nothing wrong with it? It does sound great for both DVD and music, but if I turn it up too loud (especially for DVD), it starts making noise (popping/distorting). And to get good bass from a non-DVD source, I need to crank it.

For a comparison, when I get in my mom's mini-van with a factory Infinity sound system, I get a good deal of bass. To get the same bass from this sub, I need to crank the volume all the way up.


On a side note, this Home Theater Forum has been so slow lately that often it doesn't even respond!


Jonny K.
 

Brian Bunge

Senior HTF Member
Joined
Sep 11, 2000
Messages
3,716
Jonny,

For a comparison, when I get in my mom's mini-van with a factory Infinity sound system, I get a good deal of bass. To get the same bass from this sub, I need to crank the volume all the way up.
This pretty much says it all. You're not used to accurate, flat bass response. You're used to bloated, peaky bass in the 40-50Hz range.

You're getting popping noises because you have the sub wide open, getting a distorted signal to the driver.
 

Jonny K

Second Unit
Joined
Dec 18, 2002
Messages
375
AH. Ok then.
So car sound = boomy music type bass.
Home Theater sound = clean quiet bass.
And this being a Home Theater sub, I suppose I shouldn't expect it to boom like a car stereo then!
And that's why DVD sounds so great, but for music I crank it way up to get the bass I'm used to.
Phew. Ok, good. I'm happy to hear that my sub is operating normally.
Thanks.
Jonny K. :)
 

Brian Bunge

Senior HTF Member
Joined
Sep 11, 2000
Messages
3,716
Jonny,

Find some music with some super low bass and I think your sub will boom with music as well! IIRC, some of the Bass Mechanik CD's are great.
 

PaulDF

Second Unit
Joined
May 17, 2002
Messages
354
So then, if I bought an SVS type sub similar to my EBS Tempest, will it sound the same? If a person bought a high priced sub looking for punchy type bass but instead got flat, accurate deep response, they might be a bit disappointed. Yet disappointment hardly describes SVS owners...

Might the others have boosts installed?
 

Michael R Price

Screenwriter
Joined
Jul 22, 2001
Messages
1,591
You may be able to create midbass peaks by playing around with your room placement.

An accurate subwoofer is an accurate subwoofer... I would expect similar results from an SVS.
 

Peter Jessee

Stunt Coordinator
Joined
Sep 25, 2000
Messages
149
So then, if I bought an SVS type sub similar to my EBS Tempest, will it sound the same? If a person bought a high priced sub looking for punchy type bass but instead got flat, accurate deep response, they might be a bit disappointed. Yet disappointment hardly describes SVS owners...
SVS subs are tuned to be anechoically flat to low (25, 20 or 16 Hz) frequencies. However, placing them in a typical home gives a 6-12 dB/octave gain below a frequency of 30-60 hz, depending on room size, wall construction and door sealing. So a 16-46 owner could be looking at a +6 to 12 dB boost at 20 hz. For someone expecting a lot of bass from their purchase, this would be percieved as satisfactory bass. An EBS system, with it's drooping bass response at low frequencies, will give a more accurate installed bass response than the SVS.

My cousin, normally a golden-ear kind of guy (Vandersteen 2CE, Signature amps, SACD player, etc.) has a considerably distorted view of accurate bass. We built a 12" DVC/300-794 ported sub in a 3 cu ft box. He set it up by ear, then I came over with my meter and test discs. I had to turn it down 7 dB to get it close to accurate - and he thought I'd turned it off! We compromised by setting it +3 dB from flat, but I suspect he cranks it when he's alone.

Most people have never heard accurate bass, and many are disappointed when they do, especially those used to car audio. Many car amps have fixed +12 dB boosts at 50-60 hz, so that is perceived as "good" bass.

Peter
 

Brett Loomis

Stunt Coordinator
Joined
May 9, 2001
Messages
142
Brian is right on here......Try some Bass Mekanik CD's....These are the best bass demo material I have found. If this doesn't wake your Tempest THERE IS SOMETHING WRONG.

I have the Tempest 214L AA with a PE 250W amp with no mods and it is awesome in my basement HT which is approximately 1,000 square feet of floor space or about 7,500 cubic feet.

I can't imagine needing more bass. Tracks from U-571 or the Matrix, SPR etc. are all I need to confirm my tempest is working.

Best $400 I EVER spent!!!
 

Mike Strassburg

Second Unit
Joined
Nov 4, 2001
Messages
421
So car sound = boomy music type bass.
Home Theater sound = clean quiet bass.
Not exactly. Lower priced car stuff is usually tuned higher and can/will sound boomy, but better priced subs crossed-over properly can be very clean & loud.
As for HT subs my dual Tempest is very clean and loud as hell. I've measured 127+ dB at 31Hz and tested all the way down to 16Hz and was still well over 100dB.
It's also very accurate for music and will occassionally pop a filament on a light bulb when cranked up. Just ask all my neighbors on the block.....and the next block over, how loud it is :D
 

Jack Gilvey

Senior HTF Member
Joined
Mar 13, 1999
Messages
4,948
SVS subs are tuned to be anechoically flat to low (25, 20 or 16 Hz) frequencies.
My understanding was just the opposite. All the FR graphs I've seen show a shallow "Low-Q" rolloff...Tom has described it as resembling .577 or so if I recall correctly.
Howard Ferstler, in his Sensible Sound review of the 16-46 (I think, also a private communication to me), found the rolloff to be basically the same as an unequalized Hsu 1220HO, which is -6dB @ 17Hz, the Fb.
 

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