Help! driver replacement, DVC Impedence ??, and recommendations - Home Theater Forum and Systems - HomeTheaterShack.com

 
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post #1 of 7 Old 02-25-10, 11:57 AM Thread Starter
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Help! driver replacement, DVC Impedence ??, and recommendations

Help me, Obi-Wan Kenobi, you're my only hope.

I'm looking to replace a driver I damaged, I'm willing to downgrade somewhat (unemployment), but want to keep my existing sub cabinet since it has acceptable SAF. I've been running an old Stryke (now AESpeakers) AV-12 in a DIY 3.4 cubic ft box tuned to 20 hz in my home theater for many years and loved it. Unfortunately I damaged the driver due to a wiring malfunction, my own fault. My wife and I are both near 60 and normally don't play it terribly loud. Our hearing is still good and we intend to keep it that way. I'd never seen the amp clip until this incident, and then it clipped for 20 seconds before I could mute the volume, damaging the driver. The easiest solution would be to replace the AV12 with a new AV12-X, Shiva-x2, TRIO12 etc, but since I'm now unemployed I'm looking for something a lot less expensive.

The two questions below are related to RE Audio's SRX12 driver. I hope you can educate me and keep me from doing anything stupid. If this driver isn't suitable for HT use in my enclosure, just let me know.

Thanks,
Jon Carlson

*******

1. Anybody have experience with the 'RE Audio SRX12' driver, either good or bad? They're available for $120 including shipping, which makes them significantly cheaper than the other options. Its marketed as a car subwoofer but appears to model reasonably well with winisdpro in my existing 3.4 cuft/20hz ported cabinet. Chime in if you have any experiences/opinions to share on this driver or RE Audio as a company. I'm not much concerned with output below 20hz. I do have a subsonic filter.

T/S parameters from the REAUDIO site are:

SRX12 12" (available in d2 or d4 versions)
Electrical Q Value -Qes: 0.41
Mechanical Q Value -Qms: 4.99
Total Speaker Q Value -Qts: 0.38
Free Air Resonance -Fs: 23.6 Hz
Equivalent Compliance -Vas: 85 liters
One-Way, Linear Excursion -Xmax: 18 mm
Efficiency -SPL 1W/1m: 86.2 dB SPL
Effective Piston Area -Sd: 480 cm^2
DC Resistance -Re: 1.8 ohm
Nominal Impedance -Znom: Dual 2/4 ohm
Thermal Power Handling -Pe: 300 W
Force Factor -Bl: 14.35

*******

2. My blatant ignorance concerning DC Resistance and Nominal Impedance is showing and I need help. The SRX12 is available in Nominal Impedance (Znom) dual2/dual 4 ohm versions, yet the site shows DC Resistance as 1.8, period. Is this a misprint, or is nominal impedance (ZNOM) not directly related to DC resistance?

Originally I was thinking I should get the the dual 4ohm woofer, wire the voice coils in parallel (2 ohms), and use a single channel of my amp since power was well matched to the driver. But I don't want to fry my amp if its really 1.8 ohms per vc, which would be 0.9 ohms paralleled. Can a driver available as both dual-2 and dual-4 have a 'dc resistance' of 1.8 for both options, or is this much too low? All RE Audio subwoofers show a single 'dc resistance' figure anywhere from 1.8 to 4.2 ohms, even though many of their drivers are available as dual2 or dual4. I'm confused.

What I'm hoping is somebody can tell me "Don't worry about DC Resistance, that has nothing to do with Nominal Impedance ohms (znom)" and maybe post a link explaining it. I just don't want to damage my amp or a new driver by running too low of a load. Worst case (and its really not bad) is to just get the dual-2 ohm driver and wire it in series (4 ohms), the only downside is I'd get less power from a single channel of my amp (225w vs 350).

*******

Useless trivia about my environment:

My amp is a JBL MPC-200 (rebadged QSC CX4), modest by this forum's standards, which can output 150w/channel at 8ohms, 225w/channel at 4 ohms, or 350w/channel at 2 ohm, bridgable to 700w at 4 ohms. I've been running it bridged (700w) to my wired-for-4-ohm AV12, but that's probably too much power for an SRX12, which is only rated to 300w max. I understand excess power per se doesn't hurt, but I may have a use for the other amp channel.

I use a 20hz highpass FMOD subsonic filter and a BFD for tweaking. If I get the SRX12 I'll use a single channel of my amp, since its just a little over what the driver can take. (and I'd never drive it that hard, anyway).

I originally had two identical 3.4cuft DIY NHT1259 cabinets. Several years ago I put the AV12 in one of them, ported it, and hadn't used (or missed) the NHT since - until this incident. The NHT1259 was a fine driver in its day, still sounds good, but in no way does it have the authority of the AV12.

Troubleshooting: I'm sure the problem is the AV12 driver itself, which now makes a rattling/flapping sound at low volumes. I swapped my JBL amp for an old plate amp I had lying around and the rattling/flapping is still there with the AV12. I also tested the JBL amp on the recently-returned-to-service NHT1259 with no problems. So driver bad, amp OK. I also removed the AV12 from the cabinet to check for anything loose in the cabinet itself.
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post #2 of 7 Old 02-25-10, 12:11 PM
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Re: Help! driver replacement, DVC Impedence ??, and recommendations

The first driver that sprung to my mind is the Shiva-X...
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post #3 of 7 Old 02-25-10, 02:39 PM
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Re: Help! driver replacement, DVC Impedence ??, and recommendations

Can you get it repaired?
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post #4 of 7 Old 02-26-10, 09:27 AM Thread Starter
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Re: Help! driver replacement, DVC Impedence ??, and recommendations

I don't know if I can get it repaired or not - I may investigate that as a cost-effective solution. I guess nobody's using the REAudio driver, so I'll probably rule that out for now. Not that's its a bad driver, just that nobody is familiar with it and I don't want to be the first to take a chance on it.

Thanks,
Jon
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post #5 of 7 Old 02-26-10, 10:01 AM
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Re: Help! driver replacement, DVC Impedence ??, and recommendations

Quote:
Jon Carlson wrote: View Post
I don't know if I can get it repaired or not - I may investigate that as a cost-effective solution. I guess nobody's using the REAudio driver, so I'll probably rule that out for now. Not that's its a bad driver, just that nobody is familiar with it and I don't want to be the first to take a chance on it.

Thanks,
Jon
There's nothing wrong with Resonant Engineering subwoofers, I've used them many times in car audio. I have not ever built a system for the home with one, however. If you can get your existing woofer re-coned that would likely be the most cost-effective solution. Contact the manufacturer and see if they can help you.
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post #6 of 7 Old 02-26-10, 12:46 PM
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Re: Help! driver replacement, DVC Impedence ??, and recommendations

Many lesser quality car audio subs have been used for HT will excellent results. For 120 including shipping you won't find anything better. If it were me I wouldn't have a problem with this sub. In 3.4 cu. ft. tuned to 20 hz it would be a decent performer. Shown wired for 4 ohms with 300 watts and a HPF at 20 hz.

Help! driver replacement, DVC Impedence ??, and recommendations-srx12.jpg




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post #7 of 7 Old 02-26-10, 03:14 PM Thread Starter
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Re: Help! driver replacement, DVC Impedence ??, and recommendations

Dyohn, Isiberian and Mike P,

I'll contact AESpeakers to see if they can repair my AV12 - that would be my first choice since its been such a workhorse over the years.

If that doesn't work out I'll probably get an REAudio driver and try it. There's no urgency since I've taken my sealed NHT1259 out of retirement. Although the NHT once seemed like a mighty little woofer, its not even close to the AV12, and I'm sure newer drivers are even better.

Thanks for all your advice and keep up the great work on this forum.

Jon
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