Here's one for Weapon and the others experienced with Earthquake 200DHC/PowerHouse DH2 amp's.

I blew the 20A fuse on the speaker outputs yesterday (finally did some decent testing). I've never felt my amp so hot, and that was before I rewired it into all-parallel!


Running 3 DVC (3ohm/coil) Magma12's - ALL in parallel

First I did testing in street mode - coils from one sub in series, then all subs in parallel to get 1.5ohms to amp. All in parallel worked out to be like 0.0975 ohms or something

I also have 10A fuse (external) for each sub (whether coils in parallel or series).


Ok so I wanna know two things:

1. How safe is it to put in a 30A fuse inside the amp (as indicated on the PCB in the amp)? I know Weapon's done something like this, but I can't afford to repair the amp in time for FB if I blow it up. Fuses are cheap and quick & easy to replace.

2. Can I actually calculate impedance?? I know there is software out there, but I wondered if it was possible without a cro and do it all on paper/calculator... I forgot that you need a tong-ammeter to be able to measure AC current (me being an electrician and all ) and just had my trusty DMM. I measured the speaker-output voltage of the amp and I didn't get to measure too high when all coils were in parallel I found the real reason my amp seems like it's "reducing power" - a problem I've noticed over the last year or so during SPL comps and testing days... It actually is due to less volts. Almost flattened the dual Odyssey's while testing - twice - and in under half an hour, to the point where I decided to leave the engine running. Engine-off testing I was getting 2v voltage drop (coils series/parallel connected) before amp started to complain

My handheld SPL meter must be way out of calibration - I could only manage a best of 106db(A). Went off the scale in db© though (understandibly).


I will try and borrow a cro from work but I wont have any chance to pick it up before the end of next week.

Third question: Is anyone able to lend me their's and bugger I'm going to need somewhere to do the testing as I wont want to do it at my place!!! I usually drive to a remote area to do my full-volume testing.

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Rich.
CarAudioAustralia NSW Representative.
2nd: Street 1-2 @ Sydney Auto Salon - June 2001, 1st: Street 1-2 @ Supernats - Sept 2001, 1st: Street 1-2 @ Auto Salon Final Battle - Nov 2001, 3rd: Street 3-4 @ Sydney Auto Salon - May 2002. 145.2dB @ 39Hz on DORAN's SPL meter!

-99 Pulsar SSS with dual Odyssey1000's, Lightning Audio Monitor cap, Alpine TDA-7572R & CHA-S624 & PXA-H600 & MRV-F505, Orion XTR5.2 & XTR8MB. Weapons of choice: Earthquake 200-DHC now running THREE!!! Magma12s in ported common enclosure currently tuned to 45Hz for SPL. DailyDriver: ported JL12W0 running off a Schneider amp in a Hiace-
"Standing by the stereo I'm feeling so alone, My back against the speaker and I'm moving on my own, Surrounded by so many and they're staring at my face, They're picking up my problem - I'm totally addicted to bass!" Image is Nothing. Imaging is Everything. click [email="basshead@blue-lagoon.com.au"]THIS[/email] to email me directly!

[Edited 1 time by basshead on 08 October 2002 at 23:55]

magmas are 4+4 dvc subs (~3.2 ohm is the DCR)

series coils, subs in parallel will give you a 2.66 ohm nominal load

so all in parallel will give you a 0.66 ohm nominal load

you can roughly calculate the impedance with a box program
(although I don't recommend winisd for that purpose)

- but the box programs don't take everything into account, so its safer to actually measure the voltage and the current, in the same conditons as at a comp (ie don't measure when the voice coils are hot, if they are likely to be cold at the comp)

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- A proud member of Team Gates - A proud supporter of the CAA SPL project

[Edited 1 time by Bassaholic on 09 October 2002 at 12:18]

and you have to use "c" on those handheld meters. "a" is for high frequencies, so now wondering your 3 12's are only hitting 106db!

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2002 Holden Astra
HU: Blaupunkt Miami Beach
Front Stage: Orion XTR 6.2
Front Amp: PPI 2360 2x90
Subs: 2 x Audiobahn 1200Q
Sub Amp: JBL 1200.1
Dead Last at Drag Combat 2-3 Woofer class
Winner at BAS 161-260sq inch.

quote:

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Originally posted by Bassaholic:
magmas are 4+4 dvc subs (~3.2 ohm is the DCR)

series coils, subs in parallel will give you a 2.66 ohm nominal load

so all in parallel will give you a 1.33 ohm nominal load

---

6 x 4ohm coils in parallel would be 0.66ohm wouldn't it?



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Car: '90 Nissan Pintara (sedan)
Headunit: JVC KD-SX750
Fronts: TotalRecoil Carsplit.6
Frontamp: Alpine MRV-T301
Sub: 2x Alpine SWR-1240D
Subamp: Lanzar VPro 2000D
SPL: 145.4db (Doran Test Day - 29/09/02)
"If its not quick, may aswell make it slower"

quote:

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Originally posted by Andu:

6 x 4ohm coils in parallel would be 0.66ohm wouldn't it?

---

yes

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2002 Holden Astra
HU: Blaupunkt Miami Beach
Front Stage: Orion XTR 6.2
Front Amp: PPI 2360 2x90
Subs: 2 x Audiobahn 1200Q
Sub Amp: JBL 1200.1
Dead Last at Drag Combat 2-3 Woofer class
Winner at BAS 161-260sq inch.

quote:

---

Originally posted by Andu:

6 x 4ohm coils in parallel would be 0.66ohm wouldn't it?

---

note to self - don't post anything late at night



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- A proud member of Team Gates - A proud supporter of the CAA SPL project

Basshead,

Nice to see you stepping up!,

Seriously though Mate be VERY careful dropping the impedance of the DHC200 down to 1 ohm and below,

dropping the DHC200 down below 2 ohms is comparable to dropping the PHD2 down below 1 ohm (due to the different amount of output Fets in each model - 8 for the DHC, 12 for the D2),

when the DHC200 first came out in the States almost everyone was burping them at 1 ohm and below at SPL comps and a heap of them were blowing, so Earthquake brought out the D2 with more output Fets as an answer to more low impedance stability (this should tell you something about the DHC, she really isnt comfortable with one ohm and below).

some Amps can take it (burping on the edge) for sixty Burps, some for seven (like Purps's) and some will fry first Burp, even with box "impedance rise" at burp frequency, it really is a bit like Russian Roullette I reckon, so if you arent prepared for a blown Amp I wouldnt run it that low, but the choice is up to you.

I ran my DHC200 as low as 1.8 Re for ages with no probs, and my D2's seemed happy enough at 1.3 ohms Re, I also seem to remember a guy in QLD (Matty Tremble) with two DHC 200's and he was burping at 1 ohm as I recall, Me and Purps blew one of his (my old one) at 0.625 ohms on like the seventh Burp at that frequency.

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TEAM DD "In the Lanes, takin names"
Project "Full Effect" coming soon - Street SPL!!
SPL King Wagga 2002/SAS 2002
Broken window/hurt hand Wagga 2002
Best 158.4db from 2x DD9515's on TERMPRO (SAS 2002)