Steve, I'm following you about the 10hz response *in room*.
I agree that for loud sound at standard musical ranges, the 15 and 18" give the best results.
For Infra base, way below bass guitars and such, I'm still not sure. Also, I think this is changing frequently.
Do you agree with what I'm saying that below fs, you really are just working the motor against the suspension. That has to be hard on voice coil heat. That must be much lower than rated impedance. Also, in such cases where air loading is minimal, all the more cone area you can get the better.
I also think there should be some kind of special driver here for these apps. Something with a real real big cone. Maybe use double spiders like a Cerwin Vega stroker, and then let the cone suspension be real soft?
What do you think of my idea for a current source amp.
Rather than approximate zero ohms, it approximates infinite ohms. Output current tracks input voltage.
Please tell us about your new designs too!
This diyaudio forum has the most knowledgeable people I have met anywhere, online or RL!
I agree that for loud sound at standard musical ranges, the 15 and 18" give the best results.
For Infra base, way below bass guitars and such, I'm still not sure. Also, I think this is changing frequently.
Do you agree with what I'm saying that below fs, you really are just working the motor against the suspension. That has to be hard on voice coil heat. That must be much lower than rated impedance. Also, in such cases where air loading is minimal, all the more cone area you can get the better.
I also think there should be some kind of special driver here for these apps. Something with a real real big cone. Maybe use double spiders like a Cerwin Vega stroker, and then let the cone suspension be real soft?
What do you think of my idea for a current source amp.
Rather than approximate zero ohms, it approximates infinite ohms. Output current tracks input voltage.
Please tell us about your new designs too!
This diyaudio forum has the most knowledgeable people I have met anywhere, online or RL!
just a guy,
Thank you for all of that.
I am interested in exploring the software.
Of course and audio room does need to be constructed differently. And even then, some things will not be containable.
I believe this is an area that is changing rapidly. These new giant drivers are relatively new. Likewise the interest in Low Freq for motion pictures, going that low, is new.
Generally more drivers gives more SPL, but not lower freq. Now, maybe when we are far under fs, then more drivers is the way. Hard to say at this point.
I believe that not all drivers would stand up well in the way Steve is using it. The lower voice coil impedance, must make it tough.
I am attracted to the idea of a current forcing amp.
I am familiar with computer simulation programs. Have written enough myself. Understanding starts with the mathematical relations.
Thank you for all of that.
I am interested in exploring the software.
Of course and audio room does need to be constructed differently. And even then, some things will not be containable.
I believe this is an area that is changing rapidly. These new giant drivers are relatively new. Likewise the interest in Low Freq for motion pictures, going that low, is new.
Generally more drivers gives more SPL, but not lower freq. Now, maybe when we are far under fs, then more drivers is the way. Hard to say at this point.
I believe that not all drivers would stand up well in the way Steve is using it. The lower voice coil impedance, must make it tough.
I am attracted to the idea of a current forcing amp.
I am familiar with computer simulation programs. Have written enough myself. Understanding starts with the mathematical relations.
None of this stuff is particularly new. I mentioned the Jensen Transflex, published in 1952. Usable output to 16 hz.
Bigger boxes tune the box lower and reduce the air spring the driver needs to work against. That means voice coil heat is going to be less of a problem, not more of a problem.
Steve may be using a good driver but it isn't magic. Any driver that fits in the hole will make sound down to the tuning frequency as well as it can.
You still seem to be under the impression that all of this stuff is uncharted territory and technology is changing by the minute.
This stuff is all well documented, you don't need special amps or huge drivers. For about $200 and up you can make a decent low tuned sub (unpowered).
Bigger boxes tune the box lower and reduce the air spring the driver needs to work against. That means voice coil heat is going to be less of a problem, not more of a problem.
Steve may be using a good driver but it isn't magic. Any driver that fits in the hole will make sound down to the tuning frequency as well as it can.
You still seem to be under the impression that all of this stuff is uncharted territory and technology is changing by the minute.
This stuff is all well documented, you don't need special amps or huge drivers. For about $200 and up you can make a decent low tuned sub (unpowered).
Drivers are not put on the market to be run below fs.
Even moving with only a finite baffle, it is stressful and heat generating to work the motor against the suspension. Certainly it is real real low efficiency.
I think there are some drivers more suited to it than others.
I think a special amp design for such cases would be highly desireable.
On the efficiency issue alone, big cone area would certainly help, more than high xd.
Even moving with only a finite baffle, it is stressful and heat generating to work the motor against the suspension. Certainly it is real real low efficiency.
I think there are some drivers more suited to it than others.
I think a special amp design for such cases would be highly desireable.
On the efficiency issue alone, big cone area would certainly help, more than high xd.
Lol, ok. You're looking at a FR flat to 10hz, possibly lower, and you're still not sure. I've helped numerous people at AVS and htguide build large and low tuned sonosubs, most of them using "only" a 15" driver, and they are solid down to 15hz. There's a guy about to build dual 535 liter subs with two SS RLp15 drivers in each, tuned to ~13hz with two 8" diameter ports and 3000 watts. He should be flat to ~10hz in room just like me, and he will have MONSTER output. His four 15" drivers will end up giving him nearly the same output and extension of three of my 18" drivers.
Not really. My impedance is lower above 50hz then it is at any point below that.
If we're talking ported, using multiples of drivers will allow you to increase the enclosure volume and lower the tune enough that you actually will get solid low frequency response, up to a point. You lose headroom, but since you are using multiple drivers, it doesn't really matter. For instance, given enough TC2+ 12" drivers, I could still create a sub that will be realtively solid to 10hz without significant EQ.
If we're talking sealed, to reach a given output level with multiple drivers as compared to a single, you're using far less excursion with each. This allows you to use EQ (usually in the form on a Linkwitz transformer) to boost the low end response by requesting more from the amp down low, keeping output flat to low frequencies. I think this is an inefficient way of doing things, as I prefer large and low tuned ported, but to each his own.
Correct, most wouldn't stand up very well, as I'm using a beefy, low distortion 18" driver with high xmax. But that's not to say that multiples of smaller drivers couldn't stand up just as well if not better.
I agree that you are making this way too hard.
Zenmaster - even if you are successful in reinventing the wheel, no one is going to care. By the time you are done you will end up spending a fortune on special made drivers and amps and ultimately you will get blown out of the water by a system that cost a tiny fraction of what you have invested. One which uses current technology and current materials. You can make a whole system with what you are going to pay for one raw driver.
Good luck. You will really need it if you refuse to update your reference research material. Even if you only use this forum as research you would be better off. But you have to read more of the threads pertaining to low tuned subs.
Good luck. You will really need it if you refuse to update your reference research material. Even if you only use this forum as research you would be better off. But you have to read more of the threads pertaining to low tuned subs.
Planar Sub
Did you ever think of trying a planar sub. I tried one when I was in high school simalar to a carver ribbon but 36 x 48 inches. It wont punch you in the chest with air but it was the cleanest flatest base I have ever heard from a loudspeaker. If you augment that with some good paper cone 12" woofers you might really like it.
I am just getting involved in DIY stuff again after about 15 years. Looks like alot more science & theory in here. I understood most of the basic principles but have found nothing beats just trying it.
I always wanted to try those 60" subs & put them in a box the size of a home theatre. The truth is you can get overwhelming clean and dramatic base with a couple of 10 or 12" woofers in the right box design. Try mounting the woofers in your box facing each other and reverse the polarity on one of them. This will reduce the required box size in half.
Did you ever think of trying a planar sub. I tried one when I was in high school simalar to a carver ribbon but 36 x 48 inches. It wont punch you in the chest with air but it was the cleanest flatest base I have ever heard from a loudspeaker. If you augment that with some good paper cone 12" woofers you might really like it.
I am just getting involved in DIY stuff again after about 15 years. Looks like alot more science & theory in here. I understood most of the basic principles but have found nothing beats just trying it.
I always wanted to try those 60" subs & put them in a box the size of a home theatre. The truth is you can get overwhelming clean and dramatic base with a couple of 10 or 12" woofers in the right box design. Try mounting the woofers in your box facing each other and reverse the polarity on one of them. This will reduce the required box size in half.
jeritz, Planar sub? please elaborate
SteveCallas, I understand the importance of the enclosure volume and tuning, and how that would seem to make most driver considerations diminish.
Lets see if there are other people who have looked at any of these issues.
Also, I've added a new thread in this topic, "Current Source Amp", to address that possible dimension to this.
I'm also going to add one to address active crossover topologies.
SteveCallas, I understand the importance of the enclosure volume and tuning, and how that would seem to make most driver considerations diminish.
Lets see if there are other people who have looked at any of these issues.
Also, I've added a new thread in this topic, "Current Source Amp", to address that possible dimension to this.
I'm also going to add one to address active crossover topologies.
Steve Callas
I keep thinking about this. I am intriged by your design.
700 lts, thats over 175 gallons!
How did you decide to go cyliner, instead of big big box?
How much does that weigh?
It must be very difficult to even get that into a full sized van?
It must not go thru some doorways too.
Did I understand you use several subs together?
How tall is this big one, why not even taller?
The port is in the center, right? How large in diameter? How long a tube?
Do you have something on top to keep stuff from falling in?
Does this have a base plate, resting on the floor?
What is on the outside? Black paint? Or is it carpet?
Women don't seem to like big stuff like that.
Ever think, you could make a couple of bass absorbers that match it. Probably not that big. They would go in the room corners.
I keep thinking about this. I am intriged by your design.
700 lts, thats over 175 gallons!
How did you decide to go cyliner, instead of big big box?
How much does that weigh?
It must be very difficult to even get that into a full sized van?
It must not go thru some doorways too.
Did I understand you use several subs together?
How tall is this big one, why not even taller?
The port is in the center, right? How large in diameter? How long a tube?
Do you have something on top to keep stuff from falling in?
Does this have a base plate, resting on the floor?
What is on the outside? Black paint? Or is it carpet?
Women don't seem to like big stuff like that.
Ever think, you could make a couple of bass absorbers that match it. Probably not that big. They would go in the room corners.
About downward firing?
I've always been attracted to such. Just seems neat. Less likely to damage driver. Could even put drip rail for further protection.
20 years ago, when subwoofer systems started to become popular, most were downward firing.
But today, most are side firing. Why?
I've never understood the design issues in downward firing. Specifically the loading issues pertaining to how long the legs are, and how big the face plate is.
Most commerical subs are just speakers. To me it seems better if they can be stools to sit on, or coffee tables, or something else.
Steve, did you consider built in, instead of a moveable 700 ltrs?
How did you get your concrete form tube, it is clever.
I've always been attracted to such. Just seems neat. Less likely to damage driver. Could even put drip rail for further protection.
20 years ago, when subwoofer systems started to become popular, most were downward firing.
But today, most are side firing. Why?
I've never understood the design issues in downward firing. Specifically the loading issues pertaining to how long the legs are, and how big the face plate is.
Most commerical subs are just speakers. To me it seems better if they can be stools to sit on, or coffee tables, or something else.
Steve, did you consider built in, instead of a moveable 700 ltrs?
How did you get your concrete form tube, it is clever.
Planar Sub
Zenbrian
Sorry....I forgot I was not on the planar/Electromagnetic forum
A Planar Sub is like a "ribbon" subwoover. Not a true ribbon but a planar magnetic woofer with no box. A planar speaker can reproduce sound much more accuratly than a cone or non line source speaker, according to some. As an experiment I built a planar woofer & it reproduced incredible bass at very low frequencies, but it lacks the "punch" of a traditional coned woofer.
If my brother still has it in his basement I will try to post some pics if anyone is interested.
Zenbrian
Sorry....I forgot I was not on the planar/Electromagnetic forum
A Planar Sub is like a "ribbon" subwoover. Not a true ribbon but a planar magnetic woofer with no box. A planar speaker can reproduce sound much more accuratly than a cone or non line source speaker, according to some. As an experiment I built a planar woofer & it reproduced incredible bass at very low frequencies, but it lacks the "punch" of a traditional coned woofer.
If my brother still has it in his basement I will try to post some pics if anyone is interested.
With such a large enclosure, weight, structural integrity, and aesthetics of the shape are pretty big factors. The amount of MDF or baltic birch needed to make a 700 liter enclosure, as well as the insane amount of bracing that would be needed to keep it inert, would probably add up to well over 600lbs. Since the sonotube is so strong and won't flex, I can get away with just one piece of lightweight material with no ill effects. And as far as aesthetics, I think it looks pretty cool as opposed to a box - though a box enclosure could have probably served double duty as a tv stand or something useful.
I'd estimate around 150lbs - ~50 for the driver, ~50 for the tube, and ~50 for the MDF.
Should fit into most trucks if you take the legs and baseplate off.
If you take the baseplate off, shouldn't be a problem.
Well I have two more of these drivers and the materials for two more identical subs ready to go, but since I'm in an apartment, I'm not going to assemble them yet. I can't come anywhere close to maxing output on this thing unless I wanted to get kicked out (104db subwoofer peaks is the highest I've tempted fate with my neighbors so far), and I don't really have a good place to put another one in my living room. When I get a house, then all hell will break loose
7'. At some point, you stop gaining advantages with more volume in a ported sub, and instead, you start hurting performance. I spent a lot of time in the design stage - 700 liters looked to be the best balance for me.
Yes, 8" diameter, ~22" in length.
Yeah, one of these. At 7' tall, nothing is going to "fall" in it
, but I didn't want spiders building webs in it or anything. Yeah, the baseplate is visible in the picture. I like the look of an oversized baseplate, so I went 36" in diameter.
Paint on the end caps and baseplate, a fabric "sock" over the tube itself. The fabric is like a thin neoprene material, flat black, no sheen, won't allow any light through, and stretchy.
Lol, no, most don't. I have no plans to get married anytime soon though, so they don't have to live with it. And even if I do get married, I'm uncompromising in my bass
When you get into mid-upper level commercial subs, I find that most are still down-firing. While there are no doubt still good front firing subs, most cheaper subs use that orientation because you have to take cone sag into account. Drivers without much xmax can't spare even 1mm of sag, so they aren't suitable for down-firing applications.
What do you mean by "built in", do you mean infinite baffle?
Called several concrete and construction contracting places. Suprisingly, here in St. Louis, large diameter tubes are WIDELY available. I literally had my pick between about five or six places. Funny story is that I almost ended up working for Sonoco - they were one of my job offers last year when I graduated.
Steve, I didn't realize you were in an apartment. I cannot imagine how you can use even one of those there.
When I said "built-in", I meant something of similar volume, but made as a permanent addition to the room.
If you make two more, what does that get you? More SPL? I guess more works better for the room geometry too. Isn't one enough?
Your unit is very light weight for its size and strength.
Your design is Bass Reflex, so I am surprised you need a tube for the port. Since it is so so big, I'd have thought just a hole would do that.
As I know, when BR gets to be full sized, you don't need pipes. Decades ago, big big BR was more common. No pipe, just a large hole.
Thanks for the insights about cone sag. Never thought of that before.
What are the design considerations for downward firing, like the length of the legs and the size of the sound board, etc. Never understood how that close proximity to the floor effects the rest of the design.
How can you tell if cone sag going to be a problem?
I used to always have to watch my woofer cones for evidence of phonograph record warping comming through in subsonics.
But I do like downward firing for many reasons.
When I said "built-in", I meant something of similar volume, but made as a permanent addition to the room.
If you make two more, what does that get you? More SPL? I guess more works better for the room geometry too. Isn't one enough?
Your unit is very light weight for its size and strength.
Your design is Bass Reflex, so I am surprised you need a tube for the port. Since it is so so big, I'd have thought just a hole would do that.
As I know, when BR gets to be full sized, you don't need pipes. Decades ago, big big BR was more common. No pipe, just a large hole.
Thanks for the insights about cone sag. Never thought of that before.
What are the design considerations for downward firing, like the length of the legs and the size of the sound board, etc. Never understood how that close proximity to the floor effects the rest of the design.
How can you tell if cone sag going to be a problem?
I used to always have to watch my woofer cones for evidence of phonograph record warping comming through in subsonics.
But I do like downward firing for many reasons.
It raises my absolute max spl by ~9.5db, and for a given output level compared to my single sub, any distortion is greatly reduced, as less power and less excursion are needed by each woofer. Realistically, with all three going, under everything but the most extreme circumstances, distortion levels will probably be close to nothing.
That's probably because they were tuned significantly higher and used a smaller diameter port. Back then, there was no need to have solid extension into the teens or single digits, so ported subs were probably tuned ~30-35hz.
If the legs are short enough, that region of air between the driver and baseplate can help load the driver to effectively lower the Fs a bit if I'm not mistaken. I don't know the equation or relationships for that though. I used 8" long legs because I have found with previous subs that the bass detail improves slightly when the driver is a little higher off the ground.
Use this equation: Percentage of Sag = 24,849 / ( Xmax * Fs²)
You don't want the sag to be more than 5% of the total xmax.
SteveCallas said:
There is one more thing to it.
The sag is not always constant over a long time, you won't have the same sag day one to lets say two years after. It all depends on materials used in spider and cone edge suspension.
In case of isobaric configuration it is easy to turn the whole package of drivers around after a period of time to offset long term sag.
It's like old Tannoy woofers witch are prone to sag, common rekommendation is to turn them around yearly or so to prevent voice coil rubbing. Of course this is in the other direction but the laws of nature the same.
I have some woofers in storage resting on magnet or other way oround and after 5 years they have been totally useless as they have totally bottoned out. However other have been much less affected.
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