DIY Subwoofers - General Discussion

**canaris** · **03-18-07, 07:08 PM**

After I upgraded my IB from 2 tempest to 4... all was fine.... then I started playing around with the BFD... it was going good.... then as as yesterday....the subs feel like thier running on 7 cylinders..

Things I have done so far to see what the problem is...

- I bypassed the BFD.... no improvement

- I completely removed BFD... nothing...
- I rechecked speakons on amp and tried regular binding posts hookup.... nothing...( I did this cause I added the speakons recently)

- I checked all settings on my AVR for sub out... nothing...

- I disconnected my main speakers and played only my IB...and it can't hit more than 92 DB on my digital RS meter... the cones are moving a lot... but it's completely void of any visceral feeling....I know definitely something wrong...but can't figure it out...

I checked all connections on subs.....

What else can I do?

**Otto** · **03-18-07, 08:24 PM**

Hi canaris,

Quote:

After I upgraded my IB from 2 tempest to 4... all was fine....

So does that mean that everything was working at 100% at some point? And then it got worse? Or did you just get it set up and it seemed to work until you looked closer?

Quote:

I checked all connections on subs.....

So everything is 100% in phase?

Quote:

What else can I do?

Go back to the original set up and make sure it still works properly -- create a baseline. Then start adding the other stuff. Once you add something that causes the failure, swap out the relevant components (driver, amp channel, etc.) until you figure out what the cause of the problem is.

Good luck!

**brucek** · **03-19-07, 08:53 AM**

Quote:

So everything is 100% in phase?

Be sure that a positive voltage on the positive terminal of each driver moves the cone out. There may be a wiring mistake on the drivers..... Use a 1.5volt battery for this test. Only touch the battery to the terminal long enough to get a visual reading. Don't leave it hooked up.

Also use the battery test to check all your series parallel wiring to the drivers. they should all move out with a positive on the positive wire......

brucek

**Wayne A. Pflughaupt** · **03-19-07, 01:47 PM**

Probably a polarity problem. Try disconnecting all speakers but one from the amp, then add the other three one at a time. Use pink noise or a sine wave tone in say, the 40-50 Hz range. With each added speaker, SPL should increase. If the added speaker causes SPL to drop, there’s your polarity problem.

Regards,
Wayne

**collo** · **03-19-07, 05:06 PM**

Have you ended up with a higher impedence load? That would result in less power being delivered..

**canaris** · **03-19-07, 08:27 PM**

I checked the polarity it all alright... I checked each subs VC's they are all 7 ohms ..

I powered each sub separatley... same thing... no punch and weak...

What would I be looking for if I were to check my amp.... ?

**Otto** · **03-19-07, 08:46 PM**

So the original setup doesn't work like it used to?

Initially, you said that the cones are moving a lot, but there's not a lot of sound. Could there be an air leak from the front to the back of the baffle? Something loose? I think you'd hear a lot of rattling if something were loose...

Can you do an REW sweep? What frequencies are moving the cones? Could there be some weird crossover problem?

If checking an amp problem, I'd definitely try to swap it out with another, known-good amp (even if it's not exactly the same model or power level). Perhaps put your IB amp on your mains and see if they sound weak. Does the amp have a bunch of configuration DIP switched like my EP2500? Could one of those switches be half-way in between a setting? Try swapping that amp around and see if it follows the amp...

**Wayne A. Pflughaupt** · **03-19-07, 08:52 PM**

Quote:

canaris wrote:

I checked the polarity it all alright... I checked each subs VC's they are all 7 ohms ..

I powered each sub separatley... same thing... no punch and weak…

That isn’t really what I suggested. Checking the nominal impedance is not the same as verifying polarity. Powering each driver separately will not tell you if there is a polarity issue. You have to run at least a pair of them to show swapped polarity.

Regards,
Wayne

**Sonnie** · **03-19-07, 09:17 PM**

I know you have a lot of questions being thrown at you, but answering them all will help us to help you.

7 ohms seems quite high, generally I think we see most IB subs final load at 4 ohms, sometimes 2, for the most power. If your first pair of Tempest were at 4 ohms and you added another 4 ohms in series then you now have an 8 ohm load (or 7 as you have measured, previously you actually had 3.5 ohms). That would definitely be the culprit. For instance, if your amp is 600 wpc into 4 ohms (300 wpc into 8 ohms), you previously had 600 watts going to each sub. With that 8 ohm load you now only have 150 watts going to each sub. That will make a huge difference. Are you sure everything was fine after adding the other pair of Tempest?

**canaris** · **03-19-07, 09:19 PM**

I feel like a moron..or I am getting dyslexic now in my late forties.... I can't believe after so many times verifying the polarity on the speakers and the total ohms and looking at the back of the my amp I never seen this...

The problem started last week... when I discovered 2 of the subs were reversed polarity ...but before I got to that I swapped the speakon connectors thinking they were the cause... thats when I needed help fast....so this dummy after replacing the speakons, I created the same problem I solved...by not paying full attention to the banana connectors.

I thank all of you for telling me to keep checking polarity..

Sonnie, my amp is a Crest CPX 2600 ....each pair of subs gets 550 watts at 8 ohms... which I think is adeqaute for an IB.... you think it would be risky if I bridged it to a single 4 ,which would give 2000 watts ..or 500 a piece... since IB 's could be easy overdriven?

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