@cvjoint I may have missed it if you did, but have you tried removing 4 of the 10's and experimenting with that?
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I have not. The hard part about using only 4 is to block the other 4 holes properly. Because of that I might as well buy 4 subs built to withstand small box pressures while I'm at it. I am trying to find a solution that doesn't forgo the SPL I can produce now.
So I bought the Seas L26RO4Y, four of them. They arrive Friday and I should have them powered next week.
Yes, this is my best guess as well. Oddly, there are very few good sealed box woofers. Most seem to be designed as a compromise between vented and sealed alignments.
Take Peerless for example. They used to make an XLS driver with .1 CMS and high BL. It was one of many XLS designs at that time. Now that woofer is not made anymore and you have to settle with only one XLS choice, and the CMS is .39. I'm weary this will sound anywhere near as good as the older model. It does not have the purpose made stiff surround composition. So you only get the high motor force for small boxes but not the suspension. Furthermore, they have made the XXLS design to keep up with the excursion demands of modern drivers, but the XXLS doesn't have the coil, the suspension, or the motor to work well in small sealed boxes.
So instead I bought the Seas 4 layer sub. It seems to have the suspension, motor, coil mass, stiff cone, and the linear/xmech excurison required for small boxes. The only other company that makes a small box specific sub is Dayton with their HO models. I've always preferred Seas drivers over the budget Dayton. It's a little better in every way.
I've also looked at car audio subwoofers. Not only do they not have shorting rings, the BL is not as high as it is for the Seas, and their QTS and FS values are absurdly high. What they do have going for them is stiff suspensions and high xmech. So while there is some optimization for small box, car subs seem to be mostly optimized for SPL. The baskets are also unusually grotesque and I'm sure some of that translated to noise as loads of air rush through the little cavities left open.
I wish Vifa had a NE series optimized for sealed boxes. All they have to do is stiffen up the suspension. The motor is all there. I hate lugging around 100 lbs of ferrite motors in a car.
I owe you a snapshot of the amp birthsheet. I'll try to find it again tonight. If I am to try a higher ohm load I will do it with the Seas subs so I can at least get a 4 ohm load and 850 watts.
Order of operations:
1. Install Seas subwoofers
2. Try 4 ohm load
3. Try bass traps
4. Try isobaric
The install for the Seas subs starts tonight. 😀
Thanks for all the input so far folks! 😎
The trouble with your order of operations is you will never know where the problem lies, which is never satisfying.
1) Will the SEAS woofers alone solve the problem due to their correct alignment in the small box? If so then it stands to reason that a properly designed Linkwitz Transform circuit would solve the problem too. LTs work. I've used them numerous times with woofers installed into tiny boxes and the bass has always been excellent.
2) You should really try the 4 ohm wiring with the Vifa units first otherwise you're going to be changing two things at once (SEAS drivers and impedance) so won't know what's responsible for the change in sound.
3) Bass traps in a car? Bass traps are designed to alter the rooms modal region and thus smooth out peaky/dippy bass. In a car you don't have any of these, at least not down in the region that your subs will be covering, so are completely irrelevant.
4) Is quite pointless when all you'd need to do is add in a LT to tune the system however you want.
Regardless of that the SEAS drivers are actual subs, the Vifa's aren't, so whichever way you look at it they are the better choice period. I just think that you would be able to get the Vifa's sounding the way you want if implemented correctly.
1) Will the SEAS woofers alone solve the problem due to their correct alignment in the small box? If so then it stands to reason that a properly designed Linkwitz Transform circuit would solve the problem too. LTs work. I've used them numerous times with woofers installed into tiny boxes and the bass has always been excellent.
2) You should really try the 4 ohm wiring with the Vifa units first otherwise you're going to be changing two things at once (SEAS drivers and impedance) so won't know what's responsible for the change in sound.
3) Bass traps in a car? Bass traps are designed to alter the rooms modal region and thus smooth out peaky/dippy bass. In a car you don't have any of these, at least not down in the region that your subs will be covering, so are completely irrelevant.
4) Is quite pointless when all you'd need to do is add in a LT to tune the system however you want.
Regardless of that the SEAS drivers are actual subs, the Vifa's aren't, so whichever way you look at it they are the better choice period. I just think that you would be able to get the Vifa's sounding the way you want if implemented correctly.
Some responses inline.
I think I could get the Vifas working right using only two in this box. With the Seas I'm hoping I can kill two birds with one stone and keep my SPL high.
FWIW, if I was looking at different drivers, I'd start over and go with three of these - Dayton Audio UM12-22 12" Ultimax DVC Subwoofer 2 ohms Per Coil and wire them for a 3 ohm load. I'd also undersize the box a bit and aim for a ~40 Hz F3 and/or a Qtc of 0.8 or so and then stuff it. Alternatively, wire them all as 1 ohm loads and power them with three amps, one per sub.
And yes, these drivers have shorting rings 🙂.
And yes, these drivers have shorting rings 🙂.
Yes, these look good for the application. I've modeled 4 Ultimax 10" in the box and both the Peerless XLS and Seas 4 layer subs model considerably better. We're talking about .56 Q vs. .67 for the Ultimax and lower output in general in the first two octaves. But what really pushed me away from the Ultimax is that several users reported suspension noise. The sub box sits only 3 feet from my drums. Unlike a trunk box, there is no seat cushioning to absorb noise of that sort n a lift back car like the 'Vette.
+1
another plan is to remove a single row of Vifas and install a cover panel over the holes. Then wire for either 2 ohms and 8 ohms, either way allows the amp to come up for a bit of air (amps internal voltage rails), so to speak. .will the box sounds change much because of change in box tuning I don't thinks so
I just don't understand the shootout for max watts possible, is this some SPL contest, no one is gonna sit in the car right?
I didn't know they still did that stuff .I hope you have seat covers when the brown note hits.
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That would imply no force canceling push-pull. No matter what, I'm keeping the push-pull.
The idea for using many drivers was to lower THD.
The idea for having a lot of wattage is to reduce clipping for short bursts and lower THD.
There is nothing unusual about the SPL I'm generating here. If you figure in compression, I'm looking at mid to high 120s. Any club can do that.
*I really never understood people who design elaborate sound systems with no real SPL capability. Live performances are often ferocious. If you are trying to recreate the real thing you need a high output design. To me there is no high end speaker system that is not also a high amplitude design. Anyone understands high SPL, and no audiophile grade high end system should disappoint with puny output.
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I don't know where your term "short burst of power" comes from, this is an internal switch mode power supply operating at 50KHz there is zero energy storage for a half cycle of any bass frequency. infact its probably has poor response to an instantaneous burst given class G/H , A topology driven to meet max loads.
IMO push pull is over rated too, it only reduces several even order harmonics the higher orders tend to climb, experience and theory IDK you decide http://www.diyaudio.com/forums/subwoofers/191833-push-pull-vs-normal-distortion-compared.html
IMO push pull is over rated too, it only reduces several even order harmonics the higher orders tend to climb, experience and theory IDK you decide http://www.diyaudio.com/forums/subwoofers/191833-push-pull-vs-normal-distortion-compared.html
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Peaks as in what is in the recording. Songs with high dynamic range require a system with high output to reproduce the peaks.
Push-pull as in the force cancelling one. Yes, with properly designed drivers there is little second order reduction. I'm thinking of installing both sets of Seas with the magnet in the box this time around to get the force-cancelling push-pull only.
http://www.diyaudio.com/forums/multi-way/174616-what-dual-force-canceling-speaker.html
Force cancelling is also called dual opposed or push-pull. It is different than the push-pull designed to offset speaker nonlinearities. It has nothing to do with THD.
Push-pull as in the force cancelling one. Yes, with properly designed drivers there is little second order reduction. I'm thinking of installing both sets of Seas with the magnet in the box this time around to get the force-cancelling push-pull only.
http://www.diyaudio.com/forums/multi-way/174616-what-dual-force-canceling-speaker.html
Force cancelling is also called dual opposed or push-pull. It is different than the push-pull designed to offset speaker nonlinearities. It has nothing to do with THD.
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Is this a special capability supported from dynamic tests on the birth report? I wouldnt count on anything special infact it may be crippled by class G/H esp with the wide range of loading of real speakers operating about resonance.
The whole rational for Class G/H is the max power rating which says at low ohms "keep internal voltage low expect high current". But your actual speakers say hey "I'm really high impedance give me more voltage" and they proceed to fight/conflict each other. Meanwhile the amp guys are just manually swapping out resistors and rerunning the test, the amp is very happy to do that.
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Dynamically the class G/H amp cant cope with wide ranges of sounds into a variable load, but may try its best to swing the internal voltage with some slow bass aka "box sounds". In a normal amp in "high ohms mode" then there would be no conflict and the amp would deliver all it could until someone attached a very low impedance blowing up the amp.
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You don't need to tweak anything all you need to do is rewire the internals of the sub for different load impedances to see if that helps. And try a properly implemented and configured Linkwitz Transform circuit.
There are two issues that could be causing issues here, one is the amplifier isn't comfortable with the load and two the box alignment needs correcting. You have ways of solving this yet don't seem interested in trying either.
As do the Vifas. I don't know where you're getting the idea from that they don't.
It's not a trick many commercial subwoofers go the direction of placing a large driver into a tiny box and using LTs to sort them out from a high Q peaking alignment, with very little real bass, to something floor shaking.
And what is this re-radiation that you're talking about? At low frequencies there are no waves bouncing around inside the box just changes in pressure. There is no sound being reflected back through the cone.
Why do you keep thinking that you need some kind of special suspension? There is nothing particularly demanding about placing a speaker into a small box. If anything the air pressure would deform and crumple the cone.
Why not? Wire two drivers in series for 16 ohms. Do this for all 8 subs. You will have 4, 16 ohm loads. Wire all 4 pairs in parallel for a 4 ohm load.
Alternatively parallel 4 drivers for a 2 ohm load. Parallel the other 4 for another 2 ohm load and wire them series for a 4 ohm.
Again there is no wave at these frequencies just pressure variations. The suspension is acoustically transparent, if you're talking about the spider, and wont react to pressure changes anyway, it sees no real forces from pressure changes within the box.
Isobaric loading halves the effective VAS of the drivers, it doesn't alter the motor strength otherwise the isobaric loading would change the other T/S parameters too. The halving of the effective VAS means that you only need a box of half the size for an effective alignment to work, but isobaric loading also eats up box space for mounting the 'helper' driver inside too. Not only this but you also lose efficiency, there is no magic in isobaric loading, you lose 3dB of overall output for the configuration - which means you're losing half of your precious amplifier power.
Using a Linkwitz Transform circuit would correctly compensate for the high Q enclosure. It would reduce power requirements around the peaking box tuning and, if designed to do so, would give you the roll off and extension needed to match your cabin gain (more extension requires more power though). My thinking here is that you don't have the required hardware to easily try implementing this otherwise you would have, so you keep shunning it instead.
You could get them working with all 8 if you'd do what's required to make them work properly.
You simply loose the ability to troubleshoot your Vifas by introducing a completely new variable, you are starting your experiment over. Regardless if you get what you need then you'll have what you want, but getting to the bottom of the Vifas would be very interesting.
Plugging off 4 Vifas should be very simple, just make some screw down baffles with the same bolt pattern as the Vifas.
Here is the birthsheet:
I'm using this same amplifier topology for full range drivers. I have it wired down at 2 ohms to drive my air motion transformers, had it running a set of Scan Speaks at 4 ohms, a set of B&Cs at 2 ohms, a set of Satori woofers at 4 ohms in this car alone, and dozens of other speakers throughout the years. This is the only amplifer type I've used in the last half decade from the same company. No issues.
Ok. I'll try 4 at a time. This will also raise the impedance to 2 ohms which is what some believe is driving the problem.
Give me one source which shows the optimal LT for my car. There is none. I have the in-car response, that is the gold standard. A LT does not make sense in a car. Furthermore a LT likely requires analog to digital and digital to analog conversions in addition to the one digital to analog conversion I already have. My processor can actually create an inverse map to correct phase distortion and linear distortion with 512 taps. It will give me a few curves to choose from and I can also manipulate the FR post tuning. This process is nearly identical to the Audyssey except improved in a few important ways, with higher resolution and post-processing tuning available. It doesn't have a LT built in because it makes no sense in a car. Lt is a basic rule of thumb equalisation that is blind with respect to the room it is implemented in.
I based my belief that speakers designed specifically for small boxes need specially designed stiffer suspensions based on what the most successful small box subs have in terms of construction. For example see http://www.madisound.com/pdf/peerless/830514.pdf
Peerless says: "The 10" XLS Car subwoofer driver has been designed with a specially compounded strong rubber surround that has the strength to withstand the high pressures inside a small sealed box." The Peerless in question has a suspension that is 5 times!! stiffer than that of the Vifas.
As for re-radiation I will direct you to Linkwitz:
"Typical box speakers have a generic sound due to their polar response, panel resonances, re-radiation through the cone and vented bass." Conclusions
I will also redirect you to Rhythmic audio:
Rythmik Audio • Bass Re-radiation
"Sealed subwoofers seek to eliminate the rear wave. The problem in the case of sealed subwoofers is that the rear wave is re-radiated through the cone. Many focus on the impact of this rear wave on causing the box itself to flex and vibrate, but a greater concern is the driver itself which is designed to radiate sound! The rear wave can cause the cone to move and re-radiate with a small phase shift."
I thought low frequency sound waves are still sound waves not just pressure.
Ok. I'll try 4 at a time. This will also raise the impedance to 2 ohms which is what some believe is driving the problem.
Give me one source which shows the optimal LT for my car. There is none. I have the in-car response, that is the gold standard. A LT does not make sense in a car. Furthermore a LT likely requires analog to digital and digital to analog conversions in addition to the one digital to analog conversion I already have. My processor can actually create an inverse map to correct phase distortion and linear distortion with 512 taps. It will give me a few curves to choose from and I can also manipulate the FR post tuning. This process is nearly identical to the Audyssey except improved in a few important ways, with higher resolution and post-processing tuning available. It doesn't have a LT built in because it makes no sense in a car. Lt is a basic rule of thumb equalisation that is blind with respect to the room it is implemented in.
I based my belief that speakers designed specifically for small boxes need specially designed stiffer suspensions based on what the most successful small box subs have in terms of construction. For example see http://www.madisound.com/pdf/peerless/830514.pdf
Peerless says: "The 10" XLS Car subwoofer driver has been designed with a specially compounded strong rubber surround that has the strength to withstand the high pressures inside a small sealed box." The Peerless in question has a suspension that is 5 times!! stiffer than that of the Vifas.
As for re-radiation I will direct you to Linkwitz:
"Typical box speakers have a generic sound due to their polar response, panel resonances, re-radiation through the cone and vented bass." Conclusions
I will also redirect you to Rhythmic audio:
Rythmik Audio • Bass Re-radiation
"Sealed subwoofers seek to eliminate the rear wave. The problem in the case of sealed subwoofers is that the rear wave is re-radiated through the cone. Many focus on the impact of this rear wave on causing the box itself to flex and vibrate, but a greater concern is the driver itself which is designed to radiate sound! The rear wave can cause the cone to move and re-radiate with a small phase shift."
I thought low frequency sound waves are still sound waves not just pressure.
OK
Notice something. The test voltage in on top left says 14.4V. according to my math that allows for zero cable drop at over 200A! So it can only work on their bench not in ANY practical situation that I can see. Yet you have designed for that 2500W. It's for show only, a boast. AND I keep telling you car amps don't support 'power bursts' in fact bursts may come out sounding like farts with your load and filtering. Pls apply some high pass and no low pass. You need to do some trouble shooting to find out what's the problem. Please describe the power cabling you have in detail and we can see how much power you can safely design for.
I doubt your other use cases are as extreme, and
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Can you point me to someone else explaining the same concept you are trying to get across? This may be a worthwhile pursuit, I just can't wrap my head around what the concept is. I think we're just having a communication difficulty.
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