Infinite Baffle R500X1D with ID15D2 V.3 - Not Flexing? Power/Gain Questions

[danwogan]

Hi everyone,

New guy here. I've had an infinite baffle setup in my bagged FBO BMW 335xi for years and have only recently really been trying to get the most out of it and understand where the limitations are. Here are some photos and the specs on my setup before I get to my questions:

Rockford Fosgate R500X1D Prime 1-Channel Class D Amplifier
ID15D2 V.3 - Image Dynamics 15" Dual 2-Ohm Subwoofer
Wired from the amp as a 4-ohm load (sub is 2-ohm dual voice coil) like the image below:

Thus, according to the specs of the amp, it's outputting 300w RMS x 1 at 4ohm to my sub which is rated at 100-700w (with a suggested RMS rating of 350w). So the power ratings match quite well.

Additionally, I have the included remote gain adjustment knob that came with the RF amp. I confirmed via customer service chat with RF that the knob, despite being advertised as a punch EQ, actually functions as a remote gain or attenuator of the amp's gain setting (on 'Prime' amps only vs their 'Punch' or 'Power' amps where it acts as a punch). Meaning, setting the gain on the amp and having the knob turned all the way up is the exact gain setting as indicated on the amp, and then can only be turned down or attenuated with the knob.

My questions mainly revolve around what the best settings on my amp and knob are to get the most out of my setup, and if changing them really make any difference at all. At the present moment, I have the gain setting on the actual amp at around 5 out of 11, where the knob is almost completely turned all the way down. If I click the knob up from 0% until about 5%, the sub volume increases nicely but drastically, until I can tell the signal starts to clip. The overall volume of the bass from the sub is quite high at this point, but what really concerns me, is that the cone of the sub is BARELY moving/flexing at all, even at its supposed maximum clean power. If I look closely, I can see the IMAGE DYNAMICS logo vibrating, and if I were to gently hold my finger near the cone, I can clearly tell it's vibrating, but I'm wondering why it's not "flexing" like any other sub I've ever seen. Is that just how free-air IB subs operate without a baffle/enclosure to modulate the air?

So, I'm wondering if there's a "right way" to use the knob and gain setting on the amp in conjunction to optimize the sub's performance. I feel like the sub can output significantly more power, but just needs the right combination of gain/knob tuning. Maybe instead of having the gain on the amp so high, I can turn it down to maybe 2 or 3 out of 11, allowing me to turn my knob up higher to get to that sweet spot. Though, I'm not sure how that would make a difference, since again the knob should only be turning down the amp's gain setting.

TL;DR - Why is my sub not "flexing," and begins to clip at such a low power/gain setting.

Thanks very much in advance for your help. Here's a couple photos of my car just because.

Click to read more...

 

[hispls 5,000+ posts]

Cone movement becomes exponential as you halve the frequency. If you're playing normal music played on instruments the cone shouldn't be pumping all that far peak to peak.

You may try to download or buy a "bass mechanic" CD or similar and throw some test tones at it. I'd wager once you dip down to and below 30hz you may start getting closer to physical limits of your woofer.

Really you probably could get away with a bigger amp if you find you're not near mechanical limits and the coil isn't getting overly hot.

In the meantime you should probably dial your gain down if only a small percentage of the remote knob is enough to hit maximum unclipped power from your amp. I try to aim for 50% of the dial with loud/modern recorded music, that leaves you some flexibility and room for boost when you play older or low record quality tracks.

If you're just looking to get louder you could go to greater lengths to completely seal off the trunk from the cabin. That's a tedious job though and it will be hard to pull off and keep things looking as clean as they do after.

 

[danwogan]

Cone movement becomes exponential as you halve the frequency. If you're playing normal music played on instruments the cone shouldn't be pumping all that far peak to peak.

You may try to download or buy a "bass mechanic" CD or similar and throw some test tones at it. I'd wager once you dip down to and below 30hz you may start getting closer to physical limits of your woofer.

Really you probably could get away with a bigger amp if you find you're not near mechanical limits and the coil isn't getting overly hot.

In the meantime you should probably dial your gain down if only a small percentage of the remote knob is enough to hit maximum unclipped power from your amp. I try to aim for 50% of the dial with loud/modern recorded music, that leaves you some flexibility and room for boost when you play older or low record quality tracks.

If you're just looking to get louder you could go to greater lengths to completely seal off the trunk from the cabin. That's a tedious job though and it will be hard to pull off and keep things looking as clean as they do after.

Thanks for your reply and insight.

I suppose I should've clarified in my original post, but the lack of flexing of the cone is specifically on frequencies that I know the subwoofer is producing. I have my crossover set to about 60hz, and the test music I'm playing are tracks like this one, where each bass note is represented by a known frequency value (usually between 25 and 50hz). These tracks are basically just "bass tone tests" like the CDs you mention. And again, the sub is producing significant db when near its pre-clipping level, but the cone is BARELY moving. I've never seen a system powered equally to mine where the peak of cone doesn't travel a good 3-4 inches.

This just makes me think I've set something wrong and the sub can actually put out so much more power. I'll try turning down the gain setting on the amp so that I can put my knob value at more like 50% before it starts clipping as a test, but I'm not overly confident that will give me more usable power before it clips at the same overall db/output.

I guess I should ask an obvious question: how exactly does that amp's gain setting correlate to its overall wattage/power output? If my amp is indeed outputting 300w RMS at 4-ohm like I've wired it, at what gain setting is this RMS wattage being achieved? At the minimum gain setting? At the maximum gain setting? Or is it always outputting 300w RMS no matter the gain setting, but then only goes up from there the more you turn it up?

Thanks again in advance.

 

[hispls 5,000+ posts]

Or is it always outputting 300w RMS no matter the gain setting, but then only goes up from there the more you turn it up?

Gain is just to match sensitivity of the amp to the input signal from your head unit. Maximum unclipped output of that amp is hard capped by the design of and components on the amp. What you use it for is so that the amp is putting out it's maximum output somewhere towards the top end of your volume knob, this should allow you the most flexibility in between.

In other words, if you turn down the gain pot on your amp you'll have more room to dial in on the remote gain knob. In situations where finding an extra 10th of a dB is critical you would probably want to test higher gain and low input signal and vice versa. From my testing I got just slightly louder with Sundown class D mono amps from going lower on the amp gain and hotter on the input signal from the source. This may not be true with every amp and the difference would be inaudible though so don't get hung up. Again, you're just trying to blend in the subs to the mids and highs and have a consistent change in output through the whole sweep of your volume knob as you roll up and down.

If you're playing 25hz and not over exerting your subs mechanically you will very likely benefit from a larger amp.

 

[danwogan]

Gain is just to match sensitivity of the amp to the input signal from your head unit. Maximum unclipped output of that amp is hard capped by the design of and components on the amp. What you use it for is so that the amp is putting out it's maximum output somewhere towards the top end of your volume knob, this should allow you the most flexibility in between.

In other words, if you turn down the gain pot on your amp you'll have more room to dial in on the remote gain knob. In situations where finding an extra 10th of a dB is critical you would probably want to test higher gain and low input signal and vice versa. From my testing I got just slightly louder with Sundown class D mono amps from going lower on the amp gain and hotter on the input signal from the source. This may not be true with every amp and the difference would be inaudible though so don't get hung up. Again, you're just trying to blend in the subs to the mids and highs and have a consistent change in output through the whole sweep of your volume knob as you roll up and down.

If you're playing 25hz and not over exerting your subs mechanically you will very likely benefit from a larger amp.

Thanks again for the reply and for the info on amp gain. I may look into more powerful amps then to see if it can drive that woofer more to its full potential. I've been looking at RF's higher-power Prime amps (so my knob will work the same way with it) and found this Rockford Fosgate R2-1200X1 which can do 400w RMS at 4ohm, which is an extra 100w over my current amp. My only concern, however, is that my sub is rated for 100w-700w with a "suggested" RMS rating of 350w. If this new amp puts out 400w continuous power, is that not technically overdriving the sub?

On that note, if I ever want a more powerful sub to match the amp, what would be a good Infinite Baffle sub to pair with the Rockford Fosgate R2-1200X1? In addition to putting out 400w RMS at 4ohm, it can also do 800w at 2ohm and 1200w at 1ohm. I've been looking around and can't really seem to find any DVC subs that operate at 1ohm or even 2ohm. Would I need a single voice coil sub to take advantage of being able to wire it at those lower impedances?

 

[Firewalker]

You have to remember to count in rise and all that. I would have no issues putting a 800 watt amplifier on a 350-600 watt RMS subwoofer. Just set everything accordingly. Also 99% of the mono-block amplifiers come with bass knobs these days so don't let that box you into just one brand. Most of them use the same kind of cable you just switch out the knob at your seat is all. I did that when I went from PPI to my Cab-22 as they are 2 completely different manufactures. 350 dollars is a lot for 1,200 watts but the RF mono-blocks like that are solid. I just think you can do better with a 1K SFB from Sundown and for much cheaper. Image Dynamics are really decent subwoofers & many people use them in IB setups from what I have seen on DIYMA and other places I think the problem is just the amplifier you have isn't enough power. I bet going up to that 1K would be a huge improvement.

Sundown Audio SFB- 1000D (SFB Series) Car Amplifier Monoblock 1000 Watts RMS

Features Digital Class-D Mono Block Amplifier Dual MOS-FET PWM Power Supply 1 Ohm Stable Load 12 dB/Octave – Variable Low Pass Filter 12 dB/Octave – Variable High Pass Filter 9 dB/Octave – Variable Bass Boost 4 Way Protection Circuit (Thermal, Voltage, Speaker Short, DC Offset) Wired Remote...

caraudiobargain.com

 

[hispls 5,000+ posts]

Thanks again for the reply and for the info on amp gain. I may look into more powerful amps then to see if it can drive that woofer more to its full potential. I've been looking at RF's higher-power Prime amps (so my knob will work the same way with it) and found this Rockford Fosgate R2-1200X1 which can do 400w RMS at 4ohm, which is an extra 100w over my current amp. My only concern, however, is that my sub is rated for 100w-700w with a "suggested" RMS rating of 350w. If this new amp puts out 400w continuous power, is that not technically overdriving the sub?

Entry level RF amps have been pretty poor since the original Series 1 back in the late 80s. I would avoid their lower lines. If you don't want to spend to get up into their flagship models it's best to avoid JL, Rockford, Zapco, etc. You're paying high for the name either way but when you're not buying their higher ends you're not getting anything but the name for your money. At least with their high end stuff you get the name + good/proprietary designs and solid build quality. Anyway on entry level RF budget you can get more value out of Audioque or similar cookie cutter Korean class D.

Power handling is rather a complicated topic but sufficed to say if you're not near mechanical limits and you don't smell anything strange when you're getting on it you can add more power. If/when you buy a bigger amp you'll just need to be mindful of excursion and thermal troubles as you start feeding that sub more power.

There used to be a few 1000W infinite baffle type subs around on the market but I can't think of anything off the top of my head. For 1000W IB you're looking for 3" coil, FS in the mid to high 20hz neighborhood and Qts of around .70 give or take 10-15%

 

[2RZ-FE 10+ year member]

JL JD and RD are still good amps. I wouldn’t pay for their flagship for the power they provide. Adding a 10x and slope switch somehow doubles the price.