you don't have any "concept" of testing a high power amp @12V ?
start with understanding the specs of this amp if any< example> DC input range =?
understanding batteries and charging
understanding class G/H
bridging amplifiers
IR drop on cables with regards to high current
when you designed a system to its limits like you've done here , you have to expect troubles and dig a lil deeper.
either that or back it way off, or maybe realizing why this isn't a 2500W amp for normal setups.
start with understanding the specs of this amp if any< example> DC input range =?
understanding batteries and charging
understanding class G/H
bridging amplifiers
IR drop on cables with regards to high current
when you designed a system to its limits like you've done here , you have to expect troubles and dig a lil deeper.
either that or back it way off, or maybe realizing why this isn't a 2500W amp for normal setups.
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This is exactly why you cannot communicate a simple concept to me. There is not a single complete sentence uttered in your post. Half the things you mention are irrelevant. For example, this amplifier is a monoblock yet you are trying to ridicule me for not understanding bridging amplifiers.
Perhaps you are here to explain a concept, or perhaps you are here for an onslaught of personal attacks. I can't tell which is which and that is a problem. I think it's best we bury this discussion. Thank you for your input but trying to make sense of your posts and dealing with the attitude is just not worthwhile.
I'm sorry I don't see one personal attack maybe you can point to it?
I'm trying to explain why you cant get 2500W and maybe to check your amp out for poor loading.
It doesn't concern you that the birthing report tested it only to 14.4V @ >200 amps meaning that it accounts for zero cable length in any real setup ?
is that a concept you having trouble with?
There are no bridged amps inside a monster monoblock/ who knew? thanks for that.
I'm trying to explain why you cant get 2500W and maybe to check your amp out for poor loading.
It doesn't concern you that the birthing report tested it only to 14.4V @ >200 amps meaning that it accounts for zero cable length in any real setup ?
is that a concept you having trouble with?
There are no bridged amps inside a monster monoblock/ who knew? thanks for that.
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You obviously do not understand what's going on here or understand what an LT does.
I cannot point you towards a source that shows you the optimal LT for your car. You design the LT to suit your design goals. There is no off the shelf solution.
The LT makes perfect sense in a car, it makes perfect sense in a lot of locations, it's a very flexible circuit, you can use on tweeters to subwoofers if you know how to use it.
Nope. The LT was first born as an analogue active circuit designed by Linkwitz himself. You could simply build one and place it in line with the inputs to your subwoofer amplifier.
It doesn't have an LT because an LT is a fairly non standard filter, not that it has no place in a car. It has as much place in a car as it does anywhere else.
Nope. Not really. They do require a certain set of T/S parameters to work well in small boxes though.
Suspension stiffness has nothing to do with this. And you need to clarify what you mean by suspension too. There are two parts to a loudspeakers suspension system, one is the spider, the other is the surround. Suspension stiffness is a combination of the two, you could have an extremely flexible and soft rubber used in the typical rubber surround and a very stiff spider, or you could have this the other way around.
Like I said though, suspension stiffness is not an important criteria for small box subwoofers. What's important is the overall resulting T/S parameters. The only thing that could be necessary is using surrounds that have a high resistance to deformation or expansion under pressure. This doesn't mean they need to be stiff mind you, just that they don't like to be stretched. Cotton fabric, for example, is very flexible, but resists expansion.
Yes Linkwitz is talking about midrange frequencies here not bass.
This is marketing hype there are no waves created inside small box subwoofers. The wavelengths for low frequencies are ridiculously large and the inside of the box very small, there is simply no place for a wave to exist inside such an enclosure and therefore no way for it to be reflected.
No the only thing you're getting at low frequencies are pressure changes within the box. Re-radiation is not occurring in the typical sense. If Rythmik are referring to anything it would be the non linear effects of air compression in small box subs. Rhythmik use motion feedback right? Something this would help correct for, which is why they are probably mentioning it.
The bottom line is that I don't think you realise how a Linkwitz Transform circuit works.
In your case, with your small box and many drivers, you have a high Q, peaky alignment. This has several effects. The first is that it severely limits how much low bass the box is going to produce, the second is that it creates a peaky response around the box tuning and the third is that it messes up the transient response of the system, creating an under-damped system that rings.
First and foremost the Linktwitz Transform circuit will correct the peaky response but it will also correct for the under-damped ringing of the high Q system. This is via the first set of input parameters into the equalisation network, which requires you entire the Q and tuning frequency of your actual loudspeaker.
Secondly, via the second set of input parameters, it will allow you to optimise the equalised response around any new desired system Q and new desired tuning frequency.
In other words it corrects for the troublesome alignment that the Vifas have inside the small box whilst also allowing you to equalise the frequency response of the sub to match the characteristics of your car for a flat frequency response.
As infinia says, we're only trying to help you here but you seem reluctant to accept what we're telling you.
I'm willing to accept any fix as long as I understand it and it is a good solution. Really look at what Odyssey room correction does and tell what is it that it can't do and the LT can.
you know they are completely tapped out (out of their element) when they start to complain about your grammar and punctuation and not the content.
The OP reminds me of a newbee who brought his new Corvette car and proceeded to show everyone his tire burn-out. He went full down on the accelerator and watched the smoke cloud in his rear view for about a full 2 minutes. Stopping only when the smoke started to pour out from under the hood, by which time all he had been doing was completely wiping out his clutch.
The OP reminds me of a newbee who brought his new Corvette car and proceeded to show everyone his tire burn-out. He went full down on the accelerator and watched the smoke cloud in his rear view for about a full 2 minutes. Stopping only when the smoke started to pour out from under the hood, by which time all he had been doing was completely wiping out his clutch.
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This is what I meant by personal attacks. Until you are able to a) be an adult, and b) form complete sentences you are not really welcome here. Go ruin someone else's thread.
Lol and you're saying that infinia is ruining this thread... Riiiiight. Cvjoint I'm pretty much done here I've explained to you the things that you can do to help solve your problems. It isn't my fault if you don't understand what I've said and therefore think it's bunk, not my problem. You obviously don't get the LT either.
I'm more than open to discuss the LT some more. As I understand it, and much of it resonates with what you've been describing it as, it is an equalizer that corrects frequency response with a functional form set by a couple of parameters. I just don't see where it fits in. You would do the same.
There is a certain belief in car audio in general that you can buy your way into the perfect setup. Also, there is a massive amount of hype instilled in benchtop parameters as selling points for equipment. A customer is coached into buying this and that, has it installed, and the car comes out the other end sounding impeccable.
The difference in this thread is that the OP is trying to be his own "install bay magician". In 99% of all cases, the customer is not going to want to change anything they have just been sold, they just want it all to do the job like the sales staff detailed. Sometimes this is extremely difficult to accomplish.There is a "gray area" that must be filled in by the installers and their skill sets.
I would encourage the OP to reread the advice given by the professionals trying to help. There are always tradeoffs in any system, AND many paths to pursue. Without the requisite mountain of experience and lessons learned from past mistakes, it is extremely difficult to pinpoint weak links or contributing factors. It is nearly impossible to devise a realistic solution by reading spec sheets and case studies.Trial and error is not your friend in this area; reality bites.
There seems to be a discontinuity between ideal and real parameters in this discussion. At the power and volume levels being applied here, everything in the system deviates wildly from published data. A zero gauge welding cable has measurable resistance and inductance when passing 200 amps through it, nevermind an 8 or 12 gauge cable.. Much more so a subwoofer dissipating 200 watts on peaks. At higher power levels, the individual speakers tend to show off the fact that they are not identical to each other. These factors are independent of the actual amplifier and small signal path, which add even more complexity to the system.
A decent amount of solutions and avenues of approach have already been mentioned. This is the stuff that separates the men from the boys in this realm. Many of these suggestions have been dismissed as "tricks and gimmicks" by the OP. I argue that in reality, they work well if applied correctly. People have won some pretty big trophies using these "gimmicks". The key is knowing which "trick" will work on your ears (and bowels in this situation).
The difference in this thread is that the OP is trying to be his own "install bay magician". In 99% of all cases, the customer is not going to want to change anything they have just been sold, they just want it all to do the job like the sales staff detailed. Sometimes this is extremely difficult to accomplish.There is a "gray area" that must be filled in by the installers and their skill sets.
I would encourage the OP to reread the advice given by the professionals trying to help. There are always tradeoffs in any system, AND many paths to pursue. Without the requisite mountain of experience and lessons learned from past mistakes, it is extremely difficult to pinpoint weak links or contributing factors. It is nearly impossible to devise a realistic solution by reading spec sheets and case studies.Trial and error is not your friend in this area; reality bites.
There seems to be a discontinuity between ideal and real parameters in this discussion. At the power and volume levels being applied here, everything in the system deviates wildly from published data. A zero gauge welding cable has measurable resistance and inductance when passing 200 amps through it, nevermind an 8 or 12 gauge cable.. Much more so a subwoofer dissipating 200 watts on peaks. At higher power levels, the individual speakers tend to show off the fact that they are not identical to each other. These factors are independent of the actual amplifier and small signal path, which add even more complexity to the system.
A decent amount of solutions and avenues of approach have already been mentioned. This is the stuff that separates the men from the boys in this realm. Many of these suggestions have been dismissed as "tricks and gimmicks" by the OP. I argue that in reality, they work well if applied correctly. People have won some pretty big trophies using these "gimmicks". The key is knowing which "trick" will work on your ears (and bowels in this situation).
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Cool build...
This is probably the most informative post other than the frequency response that you posted.
I would like to examine your descriptions of what is wrong with the sound a bit more. Please elaborate.
Does the system get loud? In a car as small as a vette this should be able to produce quite a bit of volume. I don't mean knocking the mirrors off axis loud but is it in line with what you would expect? If it does I suspect this problem has very little to do with the amplifier or power supply. Seems like an issue with the sound signature not the loudness.
You mention that the sound is "boxey". Have you confirmed that the box is not having an issue with the length resonance? Can you run it outside of the car with the same tracks that sound boxey and determine whether you perhaps have a nasty panel resonance that shows up at higher volume? Are you sure there aren't body panel resonances or internal trim or the hatch that are resonating and smearing the sound? I have run some very small box / high F3 designs such as this in vehicles and the sound signature can be quite different. The upper bass range is very efficient and loud and it can start to modulate the sound at your ears and sound sort of like a buzzing.
When the sound changes at high volume have you confirmed that the drivers are not being overdriven mechanically? It's hard to know what type of output levels you are talking about. Generally with car audio I default to assuming it's loud as hell. Have you properly setup the gains so that you are not clipping either the line out from the HU or the amplifier itself? You mention 31 band EQ and this makes me wonder whether there are some gain structure issues and/or clipping problems. Is there any EQ being used in that response graph you posted? I am doubtful the issue has anything to do with harmonic distortion from the drivers at all unless they are being beat on very hard. If the drivers do not seem to be being asked for that much then there may be a wiring issue. Anytime you have 8 or more voice coils it is easy to make a mistake on the wiring and just one can muck up the whole system. Have you went back through and absolutely checked your wiring to ensure that it is correct? 9v battery test on all the drivers to ensure polarity? Your comments about the high frequency sounding blurred and muddy almost sounds like a blown driver or a severely clipped signal somewhere.
Your response plot shows relatively clean and flat response from 20-100Hz. It may be that this simply sounds more top end heavy and less bassy than you expect. Have you ever had a flat bass system in a vehicle? A typical bass response in a vehicle is really bass heavy and a massive hump between 30-70Hz. My experience with small sealed systems with rising natural response in vehicle is that they sound lean on the low end even when a microphone says they are flat to very low frequencies.
Sorry for you for having already bought a lot of speakers, but a pair of 12 "pro drivers (same as 12P80Nd beyma / V2) or three of them and a good wooden tray, would give better results.
high sensitivity (close to 99dB each) massive B / L product,. and more importantly, less stress to the amplifier and the electrical system of the car (more volts to the others amps.
HiFIi loudspeakers are for domestics environment .....
too little dynamic, high distortion, no way to have a good sound.
Only my opinion
Regards.
( PS beatifull car you have......)
high sensitivity (close to 99dB each) massive B / L product,. and more importantly, less stress to the amplifier and the electrical system of the car (more volts to the others amps.
HiFIi loudspeakers are for domestics environment .....
too little dynamic, high distortion, no way to have a good sound.
Only my opinion
Regards.
( PS beatifull car you have......)
Amen brother
reality bites indeed
there are many skill sets that need to be mastered for 'successful' 12V high power mobile sound SYSTEMS. Some ppl can come up to speed quickly others not so much. Add a little bit of theory, lots of experience, and some magic. Also knowing when to throw in the towel, realizing when some gear is just applied (or designed) wrongly maybe with awesome bench numbers )
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This is true, I have always DIYed entirely for my car. Some ideas have been failures and some have been unique solutions. All my cars have been test beds for my ideas and I've learned much from them and I have much to learn. In car audio I don't believe you can buy your way into a good sound systems. Car shops (except 2 that I know on the West Coast) are not up to date on all the technology and typically just install crap speakers with huge margins doing nothing more than adding an MDF spacer. I do believe in home audio once can just spend the money on a good system without having to DIY. DIY in car audio is progress, DIY in home audio is more for the hobby aspect and saving money. I buy most home audio because it's better than what I can build, or I do slight tweaks.
I don't respond well to some of the "professionalism." First, because some of the behavior is not at all professional. Professionals do not insult their clients. Professionals understand that their specialized knowledge is only useful if it can be taught. Explaining technical aspects in lay terms is what a good professional does. Second, professionalism often is nothing more than celebrity marketing. I've never been a fan of blind faith.
I'll restate that I'm open to ideas and further discussion. Ultimately this is my project and the end goal is for it to be successful. This may result in some ideal experiments and it may not. I did not sign up to implement everyone's idea. If the best idea is sidelined it is my mistake as much as it is that of the one who proposed it. I have to understand the solution and I have to prefer it over others. If you cannot teach it, it just won't make it. No other way.
Audyssey correction and the LT are both "tricks." If you have the ideal system from the get-go it will not require any tricks. I don't mean to say such a system exists, just that I didn't mean anything disparaging by using the word trick. Linkwitz will forever be my hero. I agree with his teachings more than any other teacher's out there. However, I have not been convinced the LT is a good fit for my application, and I've tried to communicate in terms I understand, such as comparisons to other FR and phase correction algos, like the Audyssey.
With respect to amplifier loads I have expressed that I had the ideal classic experiment. The same amplifier, on the same speaker, with a different woofer design and I had no similar problems. Absent someone explaining the implications of wire resistance at low ohm loads (basically the theory part) I am relying on my empirical work to believe otherwise.
Yes, the system does get loud. What I'm missing is the "airy" bass, as Linkwitz describes it, from my previous infinite baffle systems. At low output the subwoofer box sounds generic, and it only gets worse with higher amplitude. I have a set of Scan Speak Classic 25W/8567-SE in my doors. If I use them to cover down to 20hz and shut off the sub I like their sound a lot better. But my doors are massive, at ~ 1.5 cubic feet per speaker, and the resulting Q is .701. I do agree that this is more about signature and not loudness. There is no problem with the SPL produced at any frequency.
No doubt the car has some panel resonance and rattles, but there are three reasons why I think this is a separate issue. First, the doors are more rattle prone yet I enjoy them more covering the same range. Second, my initial impression of the box was pretty bad playing music on it without filters outside the car. Third, even at low output before buzzing it just fills in the low end but does not have the clarity I've come to expect from IB setups. You are correct however, that car panel resonance is always going to be a problem. My next goal for the car is to apply lots and lots of closed cell foam and hydrophobic melamine to reduce rattles with little weight penalty.
I am relying on WinIsd to determine that the drivers are not overdriven mechanically. In WinISD the woofers cannot exceed 7mm one way excursion (16.9 mm is max one way) at 2,500 w in this size box. That is before applying subsonic filters which I cannot defeat. From the testing with the Omnimic and other SPL meters I haven't seen output go over 110db yet. With cabin gain that should be well under 1,000 w input, so clipping is not likely to occur. Look at the FR below, this is what I typically listen at. 3db higher for what I consider moderately high. At most 10db over for really cranking it (but not more than one song). The most EQ I've applied is +3db for the sub box. The processor controller displays volume in DB steps. I'm never lower than -15db. Lots of headroom left. I also keep my source player at under 90% volume. I have not done the 9 V test yet but have generated very low HZ test tones and eyeballed the drivers to make sure they are in sync. I totally forgot about the 9v test! Good point. I did double check the wiring.
I tried a reference flat FR in the car. It sounds great with the engine off. But on the go, there is far too much road noise to enjoy a reference FR. You can see the kind of FR I go for bellow. I do back off about 5db 20hz-63hz from what you see if the original recording has good bottom octave material.
Testing each driver separately in WT2 doesn't show it. But I believe it may have to do something with the WT2 algorithm and therefore it is not precise enough to show the wiggle.
Thanks!
I did a faceoff between the B&C 10NDL64 and the Scan Speak 25W/8567-SE in the doors. As you can see the Hi Fi driver is far more sensitive in the bottom octaves than the pro-audio driver. I can only fit 10" woofers, and this to me looks like a total victory for the Hi Fi driver:
In-door tests
I had a few questions I wanted to answer:
1. At what frequency does the B&C surpass the Scan in sensitivity?
2. Is it true that the B&C is 8.5db more sensitive at 1 watt?
3. Can the Scan go flat to 20hz in-door?
Here are both the Scan and B&C tested on the same volume level on the Alpine H800 with all filters defeated, basically full range.
Driver side, B&C in red, Scan Speak in black
Passenger side, B&C in red, Scan Speak in black
Question 1
First we have to account for the fact that the B&C is 4 ohm whereas the Scan is 8 ohm. Therefore, add 3db to the Scan Speak scale. The B&C has more output above 200hz. The Scan has more output below 200hz. That means the Scan has a considerable output advantage in the midbass. Even if I wanted more output and chose the B&C I'd have to live with less midbass output, aka a funky FR with midbass downplayed by many DB just to not bottom out the driver. So in effect, while the B&C is a higher output design in reality you can't make use of it vs. a hi fi driver because midbass output is the limiting factor for both. You have to choose a higher than 63hz crossover or choose an FR that has low midbass output to make use of the B&C's higher output. In fact, below 80hz the output is lower with the B&C even if you use EQ because you run out of Power or the coil melts down before beating out the Scan Speak. This is important because it shows you can't make use of the B&Cs higher output in the top octaves without sacrificing the low crossover or a nice frequency response!
Question 2
Based on these plots I can see that at 1 watt, the B&C is about 8db more sensitive above 300hz. So you can see here that if you plan to use the 10" in door from 300hz to 1000hz that the sensitivity advantage is real. However, I don't plan on using the 10" as midrange! So this is sensitivity advantage is not really an advantage since as I shown earlier the output is limited by the distortion in the region 63hz-125hz. Basically, the B&C will bottom out first when tuned to have decent output down to 63hz before it gets to use it's sensitivity advantage. Your results may be different if your Car does not have a huge drop in SPL in the midbass on the driver's side, or if your Car does not have a null at 120hz, or if you desire an FR that is cut heavily in the midbass area.
Question 3
Yes, the Scan Speak has the same output at 20hz as it does at 1,000hz. Scan Speak recommends to use this driver 20hz to 1,000hz. So yes, I could run subless and still have extension down to 20hz. However... the Scans only have 12mm of throw one way. That is hardly enough to get serious SPL at 20hz!
Note also that Scan Speaks break up is very mild starting at 2,5khz or so. A 1,000hz LPF works great with this woofer. No hint of breakup. It also blends very very well with the AMT tweeters.
Those 10's in the doors look super superb for in situ response. No doubt the 30 Hz notch is part of the transfer function of the vehicle. If it were mine, I wouldn't run them too far into that notch. Doing so just makes the doors flex, bend and rattle, in direct proportion to the power you pour into the notch. Listening testing required.
Another thing to consider here is interference. With 10's in the doors that can faithfully perform into sub territory, you are going to run into phase shift and comb filtering between the box and the door speakers if they overlap very much. Even if you don't, the harmonic content of the subs is going to mess with the low end of the doors. Whether or not you can detect this effect is another story, but if it bothers you, it is difficult to correct. More listening testing required.
For your apparent goals, to get into that earth-shaking bottom octave at 125+ dB SPL, in a corvette, may not be feasible with as many subs as you have. The general rule with sealed enclosures is that for a certain sub, a smaller box is going to roll off higher, with a higher Q, and (maybe) be more efficient than the same sub in a larger airspace. Sort of the same effect as the two door speakers you compared. Trying to add more power and color to subs that cannot breathe looks ok on a chart, but you can absolutely hear the subs huffing, puffing and choking in their tiny airspace.
Another thing to consider here is interference. With 10's in the doors that can faithfully perform into sub territory, you are going to run into phase shift and comb filtering between the box and the door speakers if they overlap very much. Even if you don't, the harmonic content of the subs is going to mess with the low end of the doors. Whether or not you can detect this effect is another story, but if it bothers you, it is difficult to correct. More listening testing required.
For your apparent goals, to get into that earth-shaking bottom octave at 125+ dB SPL, in a corvette, may not be feasible with as many subs as you have. The general rule with sealed enclosures is that for a certain sub, a smaller box is going to roll off higher, with a higher Q, and (maybe) be more efficient than the same sub in a larger airspace. Sort of the same effect as the two door speakers you compared. Trying to add more power and color to subs that cannot breathe looks ok on a chart, but you can absolutely hear the subs huffing, puffing and choking in their tiny airspace.
Yes, even the stock Bose 10" had substantial output down to 30hz. However, it is hard to judge the driver per se since the OEM system may have equalization built in.
The worst notch in this car is around 120hz. There appears to be boundary interference with the center tunnel of the car. The tunnel is elbow high to stiffen the car chassis but presents a real acoustic problem for door mounted bass drivers. I was able to smooth the FR with ~4db of boost but that brought the harmonic distortion up at 120hz similar to what it is at 63hz, where the subwoofer and door woofers cross with 24db slopes. I'm not boosting more than 4db, that is the sweet spot tradeoff between linear and nonlinear distortion. Another dip appears at 450hz or so. That one only needs ~2.5db boost but the nonlinear distortion resulting from the EQ boost that high in the frequency range is even more readily audible.
I won't run subless, it's just temporary until I modify the box to fit only 4 subs. Crossover points of 63hz or 71hz seem to work really nice. I use steep filters. There is a little bit of phase shift between the driver woofer and the subwoofer. I'm going to try Alpine's phase correction EQ soon.
"Huffing, puffing and choking in their tiny airspace" indeed. But is this always a phenomena of small sealed boxes or is there a woofer design that can cope with the box pressures better? That is the question. 😀 I'm a bit stuck with a box design in this car because it's a liftback. Infinite baffle may be possible but it would be very difficult. I would have to build a partitioning wall between the trunk and the cabin before the hatch latch. The top part would have to be see through to get rear visibility. We're talking about a plexiglass/wood hybrid baffle. A little to crazy even for my builds and I was hoping not to chop up too many panels in this car.
In today's state of the art, 2+ cubic feet is way enough to get solid bass response down into the teens. In your situation, I believe you are overturned in the details. Reading the other discussion, I picked up some details not mentioned in this thread. One was the fact that the fs of your subs has raised to above 60 Hz in situ. This single fact would be enough to tell me not to put it in a SQ car. No amount of power, eq or dsp is ever going to lower that rolloff. Not bad for a rapper, very bad for a purist. There's your problem.
If you are considering blocking off half of your speaker holes, I would definitely do A/B comparisons of both straight sealed and isobaric loadings. There will be a definite and drastic difference between the two in listening testing.
With the straight sealed loading, it all depends on how much better the subs can breathe with twice the air. If your fs drops into or below the 40 Hz mark, you may be able to eq your way to heaven. Then again, maybe not.
With the isobaric loading, you should pick up a substantial amount of bottom octave and the cone control that you now lack. With the amount of power you are feeding the subs, you will most likely end up with the subsonic content you are pursuing. With each woofer effectively seeing half the box volume, this is the way to simulate a 10 cubic foot box in your car. You will get that extra 6 or more dB in the 20's you are trying to compensate for not having now, with much tighter transient response.
Once you have lowered the fs and f3 of your subs, everything will look better on charts. Either alternate loading will get you less output in a dB drag race near your crossover point, but with your preference towards low frequency output, this is a fundamental tradeoff you will have to address, given your maximum box volume. In reality, such massive amounts of subsonic character tends to suck the life out of everything else making music. Plus, it can make you queasy or dizzy while driving, as well as rattle your whole car loose from itself. Beware.
If you are considering blocking off half of your speaker holes, I would definitely do A/B comparisons of both straight sealed and isobaric loadings. There will be a definite and drastic difference between the two in listening testing.
With the straight sealed loading, it all depends on how much better the subs can breathe with twice the air. If your fs drops into or below the 40 Hz mark, you may be able to eq your way to heaven. Then again, maybe not.
With the isobaric loading, you should pick up a substantial amount of bottom octave and the cone control that you now lack. With the amount of power you are feeding the subs, you will most likely end up with the subsonic content you are pursuing. With each woofer effectively seeing half the box volume, this is the way to simulate a 10 cubic foot box in your car. You will get that extra 6 or more dB in the 20's you are trying to compensate for not having now, with much tighter transient response.
Once you have lowered the fs and f3 of your subs, everything will look better on charts. Either alternate loading will get you less output in a dB drag race near your crossover point, but with your preference towards low frequency output, this is a fundamental tradeoff you will have to address, given your maximum box volume. In reality, such massive amounts of subsonic character tends to suck the life out of everything else making music. Plus, it can make you queasy or dizzy while driving, as well as rattle your whole car loose from itself. Beware.
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