Need a very good amp for my Focal sub
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=35115
Printed Date: July 19, 2025 at 9:26 PM
Topic: Need a very good amp for my Focal sub
Posted By: markcars
Subject: Need a very good amp for my Focal sub
Date Posted: July 06, 2004 at 9:00 AM
During the last 2 days, I constructed a sealed box to exact specs from the Focal website. I put in my New Focal Utopia 27WX but the sound was not as great as I was expecting. I think my MRD-M500 needs to be replaced, so my question is, what is a very good subwoofer amp I need, to push this new sub for real good sound? I just have a few requirements.
1. I want very good SQ (as best as technology can)
2. My Focal sub is 3 ohm stable (as per specs), so amp needs to be able to handle this.
3. I am willing to drop extra $ for better Quality (even if it causes me to skip lunch a few days)
4. I need only between 100 to 600 watt max, I am not in search of a 2000 watt system to shatter my rear-windshield and go deaf meanwhile.
Thanks a lot in advance!
Replies:
Posted By: Steven Kephart
Date Posted: July 06, 2004 at 10:36 AM
I don't know if you are going to get a huge SQ difference by changing amps. My guess is that the problem either lies in the sub, or enclosure. What size enclosure did you use? Honestly, I think you might have made the mistake of thinking that the most expensive speaker will give you the best performance. And from looking at those specs, I am not too impressed. For one thing, the Fs is way too high. This may be causing you to not have enough low end extention. You can make the enclosure larger to get some of that back, but you sacrifice Qtc. From hearing you aren't happy with the driver, if you can I suggest returning the sub and choosing a better one suited for what you are doing. I recomend you checking out the W7, or equivilant for the best SQ. Steven Kephart Adire Audio -------------
Posted By: kfr01
Date Posted: July 06, 2004 at 10:53 AM
Have you tried moving it around in the trunk? Do you have a thick back seat the bass needs to get through? When I first hooked up my sub (not in the same league as your Focal, but still considered a decent sub) I was disappointed. I did three things and it made a HUGE difference in the volume, accuracy, and low frequency extension. 1) Took out the rear deck 6x9 speakers so the bass could get into the main cabin
2) Dynamatted the trunk
and last but not least: played around w/ the position. This made the largest improvement by far. I originally had the sub firing toward the rear of the trunk with the back of the box pressed against the seat. When I moved it forward a couple feet and angled the subwoofer slightly the sub came to life. Its kinda in the middle of one side of my trunk now, but it sounds awesome and I can move the box if I need to put crap in my trunk. ------------- New Project: 2003 Pathfinder
Posted By: Steven Kephart
Date Posted: July 06, 2004 at 10:55 AM
BTW if anyone is interested, Here's a link to the parameters on the driver: https://www.focal.tm.fr/gb/car/utopia/27wx.htm Steven Kephart Adire Audio -------------
Posted By: markcars
Date Posted: July 06, 2004 at 10:55 AM
Here are the spec sheets and recommended sizes for box dimentions:
Box shape and size 
Parameters:
I built a closed enclosure and used the 40L recommendation to build my box. When I tested this speaker on my home system, the sound was amazingy improved; I could hear the difference. In the car it is a different story(and different amp).
I am considering JL, JBL, Planet Audio, MB Quart etc but don't know which would be most accurate in bass reproduction.
Posted By: customsuburb
Date Posted: July 06, 2004 at 10:58 AM
The MRD-M500 is an excellent amp. If a different box dosn't work then I would try a 10" JL W7 or a 10" Brahama.
Posted By: markcars
Date Posted: July 06, 2004 at 11:06 AM
Could it be possible that my MRD-M500 has a defect? OR could it also be possible that my Alpine CDA-9811 HU has a problem on its sub-outputs. Is there an easy way to test/check which one is the culprit, the HU or Sub-AMp?
Posted By: kfr01
Date Posted: July 06, 2004 at 11:09 AM
Can you describe the sound you're hearing? What don't you like about it? ------------- New Project: 2003 Pathfinder
Posted By: markcars
Date Posted: July 06, 2004 at 11:19 AM
It is not smooth/clean such as hearing a very low note nice and pleasing, but too "heavy" and boomy, almost like distorted but not distorted. This same speaker sounded so good with my home stereo that I was definitely pleased with the sub. I could even see the cone excursion and hear absolutely no distortion but clean/smooth pleasing bass whether the volume was low or high. In the car, it does not do justice to its name. Even my Altec Lansing Computer speakers with a tiny sub of just 4 inches, sounds a lot(I said lot) better.
Posted By: DYohn
Date Posted: July 06, 2004 at 11:28 AM
I agree that the tuning frequency seems very high at around 40Hz. If the sound is boomy, I suggest your enclosure is too small. Did you use polyfill inside it? If not, add at least 1 lb per cu ft which will cause the woofer to perform as if the enclosure is 10% to 40% larger and will extend the low frequncy response. The Alpine amp you are using is a fine amplifier, by the way, as long as it is set up properly. There are always "better" ones, if you like, but I'd bet it's the enclosure or the placement in your vehicle, or both. What's the low-pass crossover frequency, and are you using a "subsonic" high-pass filter? ------------- Support the12volt.com
Posted By: kfr01
Date Posted: July 06, 2004 at 11:37 AM
Are you experiencing cabin gain 'boom'? https://www.diysubwoofers.org/caraudio.htm ------------- New Project: 2003 Pathfinder
Posted By: markcars
Date Posted: July 06, 2004 at 11:46 AM
Dyohn, the box I buit is a 40L volume (quite a large box). And I filled it first with 1 lb of Acoustastuff from parts express. Then I put in half a lb more, then another half lb during testing totalling to 2 lbs of acoustastuff.
I went to the back of my vehicle and changed volumes/tracks with my remote so I dont have to run back and forth during testing. I set the cutoff frequency (LPF) to 75hz now but tested it from 60 to 200 just to hear the difference. The best was between 70 to 80. Set the Q factor to 45. I listened from near the speaker to hear the direct sound without any reflections etc.
I also tried settings on my HPF on the second amp, but that did not affect anything on my sub but only on my 4 dooor speakers.
I also tried setting the subsonic filter on and off on the mRD-m500. I tried almost all possible settings on my subamp. The only thing that helped a bit I found was to reduce the gain to -3db. I read somehwere that -7db is the best for this amp. I have not tried that yet.
and kfr01, I did not notice any cabin boom. its the sound from the sub itself. I tried it with my windows rolled down and also by standing near the sub from outside the car, with my rear hatch opened.
As I was readign reviews on another site(corvetteforums) I read that the best amp for Focals are ARC amps. I dont know anything about ARC amps yet and would like to know if possible as well. Looking at an ARC2100 CXL.
Posted By: kfr01
Date Posted: July 06, 2004 at 1:58 PM
It sounded better when you reduced the gain? Step one in amplifier setup is to take time to set the gain correctly, have you done this? You could be hearing the amplifier clipping. I could be way off base here, but you might have done yourself a huge disservice by playing the sub in your home first. One, the noise level in your home is probably very low compared to the car. Two, you experience gain like auto cabin gain when in a home, causing the sub to sound deeper. I know my home sub sounds incredibly different depending on where in the room it is placed. The car environment is a different beast. First, I don't know that I've ever heard a sub sound great looking right at it outside with the trunk open. Close the trunk and tune your sound for the drivers seat position from the drivers seat. It takes longer, but who cares what the sub sounds like from outside the car with the trunk open? Sub bass produces very long waves. If my understanding is correct, by standing too close in an open environment, you won't hear much in the way of low bass. I don't have a strong physics background here, so someone correct me if I'm totally off base. The length of a single cycle of a 40hz wave is around 28 feet. You can hear this in a room, or in a car, standing much closer to the source than 28 feet because the bass wave can reflect off walls (fold) to get to you and complete the cycle. So, if you're listing to a sub with the trunk open, outside, standing closer than 10 feet away, you won't hear much in the way of low bass because the waves have nothing to fold off of. Similarly, if the same wave is bounced back a perfect 180 degrees from the source it can actually cancel the original wave, and you won't hear much of it either. This cancelation happens often if the sub bass waves cannot escape the trunk. Are your seats too thick, etc? My advice:
1) Make sure the gain is set correctly. Make sure the head unit is setup correctly (sub volume isn't maxed, bass boost off, eq flat, etc.).
2) Tune with the trunk closed from the drivers seat.
3) Play around with the subwoofer positioning in the trunk. Turn it around, angle it, face it up, move it forward, backward, etc. Get someone to help you w/ this and it goes a lot faster. Someone let me know if I'm off bass (heh). ------------- New Project: 2003 Pathfinder
Posted By: markcars
Date Posted: July 06, 2004 at 3:38 PM
kfr01, I agree to most of the things you mentionned. And yes, bass frequencies are very low and hence the wavelength is large. I have played around with the settings for months and changed boxes and subs several times but kept the same amps and HU. A few times I tried tuning with the trunk closed (its a suv, so I can go to the trunk area when the backseats are folded.
Someone just told me that if the mid-bass isnt right, the sub will sound "farty" and "tinny" since its difficult for mid-range amps to push 70 to 140 hz. About subwoofer positioning, Ive tried everything I could already. I am sure I am doing something wrong. I was thinking its the amp for the sub, but then I also heard its a good amp. My brains aren't working too well anymore.
Posted By: stevdart
Date Posted: July 06, 2004 at 8:08 PM
markcars wrote:
the sub will sound "farty"
heh heh I like that...I think I'll add that to my vocabulary...And forget what stuff sounds like in your home, you are in a car environment, kfr01 made some good points. If you can find someone with a CAR system you like the sound of, emulate that setup. If you keep testing out the car components in your house, you'll never find nirvana. ------------- Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: markcars
Date Posted: July 06, 2004 at 10:54 PM
Actually I have heard a car sound system and fell in love with it and that is why I went with "All ALpine". My friend has a Volvo where the sound is so amazing, I would not say my home system is better at all, that much I was pleased with its sound. I found out that it was an Alpine system (Premium Sound in a Volvo car a several yeras ago) I could not find the sub anywhere in that car. They must definitely have one and it must be hidden somewhere but was not in sight even in the trunk. I just did not want anyting else and of course started buying Alpine speakers, amp, sub-amp, sub, subbox, and head unit but to an utter dissapointment. That is when I started changing stuff. Now my 4 doors have Rockfords and but the HU and 2 amps are still Alpine (which will change in about a week). I can listen to that sound system in that Volvo for days without being tired of it and I can listen to any boring music and it would just sound superb. Well now I am in search of nirvana that I have not found yet. hopefully soon... I won't give up now that I have been pursuing it for so long.
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