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John has graciously agreed to share. John has been active on line and many of you may know him. Everyone, give one of my favorite teamRocs members a warm welcome.
------------------ Alma Gates
Posts: 3130 | From: phoenix, arizona - usa | Registered: Aug 1999
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WOO HOO! Welcome aboard, Mr. Durbin. I've got a nice little teaser question for you to get things going. I notice that the basket is made of die cast aluminum as opposed to the injection molded fiberglass reinforced material used in some of the componant sets. Why the departure in using this material for the more conventional (and perhaps less sexy) aluminum basket?
------------------ -- Lizard
Posts: 106 | From: Mesa, AZ | Registered: Jun 2000
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Trust me Alma, first sign of trouble and I'm ducking for cover - they're all yours. Liz, we actually considered a composite basket for the larger drivers, especially the inverted Studio neo 8's. It's technically feasible, the challenges are in making the back of the basket strong enough to support a larger motor structure and controlling the molding and curing of the frame accurately enough to maintain alignment between the front gasket flange, spider flange, and back so that the motor/cone are able to stay in good centered alignment without yaw. At the larger excursions required by a sub, that's harder to pull off than it is in a 6.5" mid. Also, the weight of the motor can distort the frame if it isn't very carefully engineered. Neo motors address the weight issue, but there are power handling and stroke limitations that get increasingly difficult to solve in a neo motor (at least at any kind of reasonable price) as the driver size and required Xmax go up. But the reason we ultimately decided not to invest in that engineering approach is that the advantages of saving weight or reducing back clearance seem meaningless in a driver with a huge heavy motor, plus we had no confidence that the market would embrace that big a departure from the "heavy metal" school of thought that seems to govern consumer perceptions of subs. We have tested that water a bit with the injection-molded neo components, but in that application at least there are space and weight saving issues that seem to justify it. From an application/design point of view, I agree with you that the composite basket in the smaller components is sexy, but a lot of consumers perceive it as cheaper where die-cast is looked at as more of a high end approach. In the final analysis it doesn't always pay to be too far ahead of your customers in technology, you risk losing them in the process.
John Durbin, Directed Audio aka JD
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Posts: 752 | From: San Diego | Registered: Jan 2000
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WIll the DEI 1100d run alright with 16.8 volts or will they go into protection? I am considering using 4 of them in an spl vehicle on 2 18's. So far every amp ive tested shuts down at that voltage.
thank you...
------------------ Crutchfield is the enemy!
Posts: 7399 | From: Lake Havasu AZ | Registered: Aug 1999
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The current product does not have any overvoltage protection, but I would guess you'll have a good chance of making it hiccup in and out of over-current protection if you're burping it at that kind of supply voltage and into 1 ohm or below loads. We're going to be adding over and under voltage protection to the 600d and 1100d in the very near future which will shut the amp off below 9.5 volts or over 16.5. The effects of being that far outside the normal supply voltage can be catastrophic for an amp, and we believe that it is better to have it shut down than burn up. Over voltage in particular is very hard on caps and output drivers - that 2 or 3 volt increase from normal battery supply gets multiplied by the power supply and turns into a much greater voltage increase to the rails. Unless you build with really high parts tolerances (using 200V caps for 50V rails for instance) you're going to grenade parts. We like most amp manufacturers build in a lot of peak parts capacity but it makes the product cost go up drastically when you go from say 50% above rated voltage or current to 100%. I'm also skeptical of the impact on system output (versus the greatly increased risk of breaking) when you increase the supply voltage that way, so I'm having one of our techs run some numbers on an 1100d today and will let you know how much the output increases when you go from 14.4V to 17V so you can calculate whether that's going to give you enough dB gain to make it worth pursuing. Myself, I'd use a voltage that I know won't break the amps and then make sure I have enough total power to drive whatever woofer system I'm using all the way out of the gap and into its mechanical limits, without clipping. I think if you go beyond that, your SPL isn't going to significantly improve, but you'll spend a lot more time and money fixing broken parts of your system.
John Durbin, Directed Audio
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Posts: 752 | From: San Diego | Registered: Jan 2000
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Hm, I must be talking too much, everyone else stopped :-)
Ok, here's some real world type numbers for you to consider. I had Neil run a Directed 1100d at various input voltages, using a fixed distortion limit of 0.75% THD+N, and record the output wattage into a 1 ohm load. I graphed that and found that the amp increased from about 1180 watts at 14.5V to 1310 watts at 17V. Here's the numbers from the test:
That's about an 11% increase in power from a 17% increase in supply voltage. Current usage dropped from about 105 amps at 14.4 to 95 amps or so at 17 volts, which indicates an efficiency of about 81%, compared to the 73% or so we typically see at 14.4 volts. So far, so good. Using a theoretical model of two 1100d's in external bridge mode driving a 2 ohm load, I assumed a system SPL of 150 dB at 2200 watts, our nominal output for the 1100d. We know that if everything else is the same (we should be so lucky) doubling that power to 4400 watts would yield a 3 dB increase in SPL. That means that each increase of 73 watts yields a 0.1 dB increase. So our increase in SPL from increasing the supply voltage (again, this is best-case, any losses would result in a lower number) look something like this:
Voltage Watts dB SPL 13.5 2200 150.00 14.5 2360 150.22 15.5 2398 150.27 16.5 2500 150.41 17.0 2620 150.58 ---- 2800 150.82 ---- 3000 151.10 ---- 3200 151.37 ---- 3400 151.64 ---- 3600 151.92 ---- 3800 152.19 ---- 4000 152.47 ---- 4200 152.74 ---- 4400 153.01 You can see the measured actual maximum gain in SPL obtained by boosting the supply voltage from 14.5 volts to 17 volts is 0.58 dB. Now, you might say that a 1/2 dB is a worthy accomplishment, but is it worth risking damage to your equipment? The same argument applies to driving the amps into clipping. You can drive the sub out of the gap more forcefully with a moderately clipped signal, but it places a lot more demand on the driver to dissipate heat, and hold together mechanically. At least the decision to clip the driver is one you control relatively easily at a competition. Using a 17 volt power source isn't as easy to change and you risk breaking something possibly when you didn't even need that extra 1/2 dB. That's why I said I'd personally set the system up to run at a known safe voltage, and use enough power to consistently drive the subs into their mechanical limits. In this model, that would only be 400 more watts to match the increase you got from raising the voltage. This is particularly important if you're competing in an Enduro type event where the output needs to be sustained and breakage is more likely to occur. In any event, that's my take on things, hopefully I answered your question about operating these amps at 17 volts.
John Durbin, Directed Audio sorry for all the editing, my table didn't format too well
[This message has been edited by JD (edited 06-22-2000).]
Posts: 752 | From: San Diego | Registered: Jan 2000
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Now to be perfectly honest, I have always been under the impression that when an engineer designs an electronic device, certain factors are assumed to be limited. In the case of automotive electronics, it is save to assume that the voltage will be between, for instance, 11 to 15 volts. Now I'll assume that the individual componants are all rated to well in excess of 16 volts, but in terms of how those componants are intended to work together, what kind of effects will running an amplifier at a higher voltage have. Can we expect to see
1. Increased noise (not really an issue with SPL) 2. Increased failure rate 3. Bandwidth limitations 4. Response skewing (outside of the 20 Hz to 20 Khz, +/- 3 db rating).
Basically, what I'm asking is what's going to screw up when you juice an amp like this?
------------------ -- Lizard
Posts: 106 | From: Mesa, AZ | Registered: Jun 2000
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#2 is the only one I see as likely, although they might be fine initially. In the long run though, you'll probably have a lot of cap failures (higher voltage means higher core temps than the parts were intended to see, and a shortened service life as a result) and possibly FET failures when you exceed the part's internal breakdown voltage limit.
JD
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Posts: 752 | From: San Diego | Registered: Jan 2000
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I wonder if I could discuss a possible sponsorship with you. I am in the street class and have the knowledge to do well, just not the cash flow. I have no problem using as much DEI equipment as I can, or putting logos on my truck. You can see what I am capable of from my signature, 141 with 1 12 inch sub and 150 rated watts of power. Please email me so that we can discuss this, mathman5@hotmail.com
------------------ Overcoming by out-thinking
"Forget about subsonic, I'm trying for supersonic, and I don't mean a high note."
Street 1-2 Current SPL, 141 dB with 1 RF DVC 12 and 1 RF 75.2
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Thanks, Haksr1 (and thank Alma for giving me the opportunity) I'm glad of the chance to share some info and hear from you guys about car audio and dB Drag. Shedluv, we don't currently have a sponsorship program although I know of several competitors that have switched over to our big class D model amps on their own. Check back with me later this year after our next series of subs is out - I think we'll have more to talk about.
JD
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Posts: 752 | From: San Diego | Registered: Jan 2000
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The Number One dB Drag Competitor in Arizona, teamROCS very own Kevin Smith (#010) is using DEI's awesome 1100d's to push some DEI subs in his white BMW. Lemme tell you, Kevin burped the system while I was sitting in it, and my eyeballs felt like they had spun around in my head.
quote:Originally posted by thelizman: Shameless Dual Plug:
The Number One dB Drag Competitor in Arizona, teamROCS very own Kevin Smith (#010) is using DEI's awesome 1100d's to push some DEI subs in his white BMW. Lemme tell you, Kevin burped the system while I was sitting in it, and my eyeballs felt like they had spun around in my head.
Sighhhhhh - If Kevin wasn't a very good friend, my feelings might have been hurt - (alma - tR #172)LOL - since it's Liz typing - I just consider the source! Good luck Kevin - will see you this weekend. Kiss that baby for me.
------------------ Alma Gates
Posts: 3130 | From: phoenix, arizona - usa | Registered: Aug 1999
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Liz, actually we're only using two 600d's currently. So we've still got more potential damage to be done! hehe
Alma, he only meant #1 for my class. I'm nowhere in the league of the Extreme yet. (notice I said yet). So I guess you are coming down Friday night then? Great! I look forward to seeing you again.
JD, yeah, that's it. I'm just holding her spot while she rebuilds. Can't wait to see the Bronco back in the game!!
------------------ Kevin Smith SS 1-2 teamROCS #010 - www.teamrocs.com
Posts: 1168 | From: Tucson, AZ, U.S.A. | Registered: Jun 2000
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