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


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#1 of 39 OFFLINE   Jonny K

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Posted December 31 2002 - 08:38 PM

My Tempest sub is complete:

Adire Alignment (214 Liters)
15" Tempest Driver
250W AVA250 Amp

Wired in Parallel

My old sub:
8" Aabstract Acoustics


The box is painted all black, and is truly huge and beautiful. I expected it to be just outstanding. But it's not performing as expected. What follows is mish-mash of tests and what I found:

When playing DVDs, I must keep the volume on the sub turned down to about 20%, or it starts popping like crazy during bassy scenes. Bassy scenes sound great at this volume though, rumbling appropriatly. Bassy scenes:

Helicopter explision in the Matrix
Helicopter mini-gun in the Matrix
Spanish dancing in Mission Impossible 2 (foot stomping)

But for less bassy scenes (99% of the movie), very very little bass is heard!


For other media (TV, Radio, CD), I find that to get this sub to equal the SAME volume as my old 8" sub, I've got to crank the volume on the box all the way to the top. At this volume, it sounds great, and almost all frequencies play very clean (whereas the old sub would distort). Yet, I can't turn it up any higher, because it's already cranked to the top!!!


My Receiver has a test tone for the subwoofer (and other speakers). When I play this test tone, I hear a low rumbling from the sub. With the old 8", at 50% volume it would rumble quite loud. With the new sub, It's very quiet, and I need to crank the volume all the way up to get the same rumble!!!


So basically, this new sub hits all the notes clean (when the old sub distorted), but I've got to crank the volume all the way to the top to get even 50% of the old sub's volume!!! DVD is the exception. On DVD, this sub must be turned way down, or it distorts like crazy!

I've been going nuts trying to fix this, and I have no idea what is wrong. Is this actually how it's supposed to work? I wired this sub in parallel (both positive connectors on either side of the sub wired together, and then to the amp, same for negative). Is this correct? This thing is definatly air tight, I'm sure of that. I don't feel much air moving through the two ports on the bottom, should I? In fact, the only time it really moves lot's of air is when it's popping.


You guys always praise the Tempest for being so great. Either my standards are way too high, or something isn't quite right here.


Please help!


Thanks.


Jonny K.

#2 of 39 OFFLINE   Wendell

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Posted December 31 2002 - 10:16 PM

jOHNNY

I don't know what to tell you, but I hear no popping sound on my AA 214L. In fact, I get alot of bass and its just an awesome sub. Maybe there is something wrong with the sub? How is the sub connected to the receiver?

#3 of 39 OFFLINE   Rory Buszka

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Posted January 01 2003 - 01:05 AM

This isn't about the AA sub. It is about the Tempest.

First of all, try disconnecting one of the subs. They could be out of phase.

That's my suggestion. Most likely more people will stop in here and help.
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#4 of 39 OFFLINE   Brian Bunge

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Posted January 01 2003 - 01:41 AM

Rory,

AA refers to the Adire Alignment.

Jonny,

What you are experiencing is a sub this is not boomy, unlike your old sub. This is how a low tuned, low group delay ported sub sounds. I doubt there is anything wrong whatsoever.

Your old sub probably is tuned around 35-40Hz and has a huge peak in that range. That is why it sounds "impressive" but it won't have anywhere near the extension of the Tempest.

Also, if you're using the dual flared ports that Adire and PE sell, then you won't feel much air coming from the port. The wide flares are what causes this. It's really strange when you first experience it, but that's how the flared ports work. There was an article in AudioXpress this past year comparing flared and non-flared ports and mentioned this phenomenon as well.

So I think you're just experiencing a subwoofer that's tuned low for the first time.
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#5 of 39 OFFLINE   Pete Mazz

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Posted January 01 2003 - 01:45 AM

Brian's got the answer. Give it some time and you'll get used to accurate bass and cringe when you hear another "boom box".

Pete

#6 of 39 OFFLINE   Robin Smith

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Posted January 01 2003 - 03:15 AM

Jonny,

I went through the same feelings when I finished my sub.

In fact, at first I was driving it with an unmodded plate amp that had an artificial bass boost (at around 27-30 Hz) and a rumble filter at 21 Hz. It was an awesome "punch in the stomach" sound, but it wasn't accurate.

I modded the amp to remove the boost and felt a little deflated as that impressiveness went away.

The decision to make is do you want it to be accurate or not.

I ended up striving for accurate reproduction of sound and left the bass boost disabled. I have even picked up a BFD to try and flatten it out as much as possible. Now that I am used to it, I like it better than I remembered. Its not obvious that the sub is there through the wqhole movie (which means it blends in well) but it is impressive when it is needed for some of those kickass low-end moments.

Live with it for a little while and you will start to appreciate it more.

ALternately, if you like the boomyness, see if you can mod your amp to add a bass boost around 30Hz. Ultimately, you have to like what you hear, accurate or not.

Good luck


Robin

#7 of 39 OFFLINE   Patrick Sun

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Posted January 01 2003 - 03:30 AM

You'll need to calibrate the subwoofer to integrate its output into the rest of your HT or music system. You need to use a SPL meter, and adjust the subwoofer output using the receiver's subwoofer level control to raise or lower the signal level for the sub that is sent to the plate amp.

Also, you need to check for nulls (you may be sitting in one).

The 250W plate amp volume knob doesn't need to be turned up past the 10 o'clock position.
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#8 of 39 OFFLINE   Javier_Huerta

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Posted January 01 2003 - 05:09 AM

I was very curious... what do you think about the popping sounds? Is it a normal thing for Tempests? Can it be alleviated by using a bigger amplifier?

I'm in the process of builing an Adire EBS, so I might go with 2 plate amps if it helps with this problem.

Javier.

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#9 of 39 OFFLINE   Brett DiMichele

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Posted January 01 2003 - 05:34 AM

If anything the popping sounds would be the driver passing
it's linear excursion and mechanical suspension travel limits.

And that would indicate too much power.. But this combo has
been proven time and time again so somewhere along the line
something has to be amiss.
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#10 of 39 OFFLINE   ChristopherD

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Posted January 01 2003 - 05:55 AM

The other guys may be right, but I had problems with my driver, detailed here:
http://www.hometheat....hreadid=115131

Try some troubleshooting.

#11 of 39 OFFLINE   Brian Bunge

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Posted January 01 2003 - 06:34 AM

Javier,

It's probably from having the plate amp running wide open (not a good idea).
Brian Bunge
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#12 of 39 Guest_Anthony_Gomez_*

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Posted January 01 2003 - 06:41 AM

Also check to make sure that the phase is matched properly between the mains/sub transition. The Null mentioned by Pat is VERY possible.


I also agree with Brian completely with the old sub having a "designed" big boom nature that you are now used to.

you can try and model the room responce (nulls and modes) using a free ware program like the RRC

The best way you can get things worked out for little $ is to invest in a RadioShack SPL meter and run some test tones and see what is going on.

#13 of 39 OFFLINE   Dan Pawlowski

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Posted January 01 2003 - 07:22 AM

The "popping sounds" IMO exist due to the fact that the AVA250 clips when driving the Tempest too hard. I have a tempest with a AVA250 Amp sealed box 214L and its not hard to drive the amp to clipping using a 15 or 20Hz tone. As for the lack of bass response, I would suggest reversing the phase at the input of the AVA250 amp and have a listen.


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#14 of 39 OFFLINE   Jonny K

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Posted January 01 2003 - 08:14 AM

Wow, thanks for all the help. I'll let you know what I find...

On a side note, are there any places on the web which have sound samples of "popping", or "distorting", etc? I want to make sure I know what I'm talking about.


Jonny K.

#15 of 39 OFFLINE   Jonny K

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Posted January 01 2003 - 02:15 PM

I think all I needed was some tweaking.

After playing with it for a while, I've found that for DVD I set the sub volume to about 20% and it plays beautiful. When the bass comes on, it hits hard and fills the room, but non-bassy scenes don't hum or anything.

As for TV/Radio, I crank the volume on the sub all the way up. That way it booms loud for music and such, and I can controll the volume of it using the receiver bass adjustment. It's a good mix.

In the end, I'm happy. Mom and dad, on the other hand, seem pretty annyed. :-)

I've even named it: "My Precious"

:-D

Thanks for the help.


Jonny K.

#16 of 39 OFFLINE   Ryan Schnacke

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Posted January 01 2003 - 02:20 PM

I agree with Anthony. It sounds like you're running it out-of-phase with the main speakers. That would explain why the deep bass stuff in movies sounds fine but for music its muted. The sub and mains are playing equally at 80Hz so if they're close to exactly out of phase you would get very little output at all at 80Hz. At lower frequencies the crossover will cut down the signal to the mains and increase the signal to the subs. So you'll have less and less cancellation the lower you go.

Try plugging the wires in backwards (but be sure to keep the voice coils in-phase with each other) or just turn the phase setting to 180 degrees (assuming you had it at 0). I expect this will solve your problem.

To get your phase exactly correct do this. Use a free online waveform generator to create a CD with pure sinewaves. Then play that CD in your stereo. Turn your subwoofer amplifier off and play the 80Hz tone. Use an SPL meter to record the SPL at your listening position. Now disconnect your mains and turn the sub amp on. Play the tone again - this time only through the sub - and adjust the subwoofer level until it is the same as what you recorded for the mains. Now connect the mains up again and play the 80Hz tone. By adjusting the phase and switching the wiring polarity if necessary you should be able to find the phase setting where the SPL is 6dB louder than what you got with either the mains alone or the subwoofer alone. This will also be the phase setting that gives you maximum SPL at the listening position. This is the exact phase setting you should use. This method worked great for me and immediately identified the out-of-phase problem I was having with one of my subs.

In any event, you shouldn't have to change the setting from 20% to 100% when you go from movies to music.

#17 of 39 OFFLINE   Jonny K

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Posted January 01 2003 - 05:44 PM

Interesting...

Regarding being out of phase, today I ran the THX optimizer on the Episode 2 DVD, and discovered that several of my speakers where out of phase. But as for the sub, I haven't been able to fix that. I don't yet have an SPL meter...

Is there a way to fix this without an SPL meter?


Thanks.


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#18 of 39 OFFLINE   Javier_Huerta

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Posted January 01 2003 - 11:12 PM

Interesting thread! Brian, I think I know what you mean. I turned the volume all the way up on my commercial subs and couldn't hear any popping. The reason, though, is that they have built-in power limiters, so instead of going louder and louder, the sound grew more congested over time (but the speakers never bottom out). I'd suppose plate amps don't have this kind of circuitry (for the better, since bass sounds terrible when it approaches the amp limit.

Jonny, you coulde try running a test signal at your crossover frequency to the subwoofer and your mains, and then play with the phase controls until you hear the most amount of bass on your listening location. It'll be a pain, though. I'd recommend you run out and buy the Radio Shack SPL meter for this, since it'll make this part of the procedure quite easy (plus you can use it later to calibrate your surrounds / center channel).

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#19 of 39 OFFLINE   Ryan Schnacke

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Posted January 02 2003 - 12:30 AM

An SPL meter is an indispensable tool for any HT junkie. I don't know how well you could calibrate it by ear. Without the meter you won't be able to level-match beforehand. The worse the level-matching is, the harder it will be to determine the correct phase since one side (the mains or the sub) will tend to overpower the other.

But your problem sounds so bad that I think you may just be completely out of phase. Try switching the + and - connection from the plate amp to the sub and see if it sounds better. You should be able to watch movies and listen to music at the same gain setting with decent response.

#20 of 39 OFFLINE   Kerry Hackney

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Posted January 02 2003 - 01:37 AM

One other thought that hasn't been mentioned is that the "popping" sound could also be the driver bottoming because of air leaks in the cabinet. These in effect change the tuning and allow the driver to unload prematurely. Carefully check all of your joints and cutouts. You can use incense smoke for this with the sub playing in a closed room. Use rope caulk to seal the driver to the cabinet as well as any terminal cups and the port tubes. Caulk all internal joints with tube latex if you have any doubts about the tightness of your box.

It should be pretty hard to bottom a healthy Tempest/Adire Alignment. I have never heard a click from mine in any movie. Also, don't feel bad if you find a leak. It happens to all of us sooner or later. Posted Image