Wow, I never knew sag was such an issue. Maybe I've worked with stiffer sprung old fashioned type drivers.
Steve, you are a wealth of info. Thank you. I can see, you want the very best in base. Do you listen to music with that? What sort?
I'm still uncertain about all the dynamics of leg length for downward firing. I've never seen a book that adequately addresses this.
Steve, you are a wealth of info. Thank you. I can see, you want the very best in base. Do you listen to music with that? What sort?
I'm still uncertain about all the dynamics of leg length for downward firing. I've never seen a book that adequately addresses this.
Yep, just about everything except for rap or country - I stay within the extremes
At first I was worried the sub would have a rolled off top end (top end for subwoofers meaning >50hz to me), so I thought I was going to have to cross it over at 40hz or 60hz, but that's definitely not the case, it's strong up pretty high, and my 80hz crossover works great.
I thought the Carver ribbons used cone drivers for bass.
An externally hosted image should be here but it was not working when we last tested it.
Heres the patent for the above speaker
Carver Patent EP0267650
Regards
James
Please continue. I want to hear anyone else who wants to talk about Giant Subwoofers, or issues about operating below fs.
Steve Callas, what kind of amp drives you beautiful cylinder? What will you do when you have 3 of them?
What impedance does it see at 10hz?
I have also started a new thread in this topic, Active Crossovers.
I want to look at the related issue of crossovers for multiamping, as it applies to subwoofers, but also to multiamping in general.
Steve Callas, what kind of amp drives you beautiful cylinder? What will you do when you have 3 of them?
What impedance does it see at 10hz?
I have also started a new thread in this topic, Active Crossovers.
I want to look at the related issue of crossovers for multiamping, as it applies to subwoofers, but also to multiamping in general.
tvi said:
This looks like the system used by my speakers and sub.
a Infinite Baffle is to big for subwoofer use, you can use a baffle tuned at the max frequency.
I my case a 1st order role off at 400 Hz for the ESL unit.
The woofers also have a 1st order role off at 400 Hz.
But after a total 1st order lo pass filter at 50hz the woofer gets a flat response between 50 an 400hz creating.
This also gives a very good phase response between the ESL and Woofer.
With my Clarion 32” sub I created the same.
The open baffle has a 1st order role off at 90Hz.
I created a 1st order lo pass filter at 18 HZ (FS = 17 hz) creating a flat response up to 90Hz.
A second hi pass filter at 50 Hz to match the main speakers. (Mainly used for SACD and DVD audio)
At Home theatre mode I disable this filter and use a 80 Hz filter in my surround amp.
This technique is used by Celestion, Infinity. Main disadvantage is a lower SPL and lower output efficiency. But if the frequenty range used is not to big almost Infinite Baffle sound.
One method to go below FS is motional feedback.
I know people use a the ACH - 01 - XX accelerometer for woofer feedback. (Better than a piezo postcard buzzer)
I found a forum post (Dutch) where someone is claming 5Hz - 300 hz + - 0,5 dB.
http://forum.mfbfreaks.nl/viewtopic.php?t=1680
I still like to try this on my speaker(s) when I have time.
Is there anyone who already has schematics for this and is willing to share them?
I have some old Elektuur (Dutch electronics magazine) schematics but I am looking for newer designs.
I know people use a the ACH - 01 - XX accelerometer for woofer feedback. (Better than a piezo postcard buzzer)
I found a forum post (Dutch) where someone is claming 5Hz - 300 hz + - 0,5 dB.
http://forum.mfbfreaks.nl/viewtopic.php?t=1680
I still like to try this on my speaker(s) when I have time.
Is there anyone who already has schematics for this and is willing to share them?
I have some old Elektuur (Dutch electronics magazine) schematics but I am looking for newer designs.
BenVos, Thanks. I'm aware of that approach. Basically it does work. Velodyne does it that way.
I'll read your link.
The general concensus here is that its fine to go below fs without such feedback.
I've come to accept the logic behind this.
I've made another topic, Current Source Amp, because I wonder if that might be a better way to drive when you go that low. I don't know.
I'll read your link.
The general concensus here is that its fine to go below fs without such feedback.
I've come to accept the logic behind this.
I've made another topic, Current Source Amp, because I wonder if that might be a better way to drive when you go that low. I don't know.
zenmasterbrian said:
First point it is Dutch (the Netherlands capital city Amsterdam)
A Dutch electronics company (Philips) created Motional Feedback speakers many years ago. The forum I linked to is a Philips Motional Feedback forum.
With Motional Feedback a (piezo) sensor in the speaker is used to record the actual speaker movement. This signal is returned to the amplifier as feedback. In this way most speaker linearity problems are corrected.
I cannot give you the schematics (copyrights)
I think the Current Source Amp will also improve the total performance of a Motional Feedback system. (Less correction needed)
I was also thinking about a current amp. (Current amps are also good voor ESL's) But the same time problem.
I'm using a Carvin HD1800 - 600 watts into 4ohms per channel. The design is amp limited so there is no chance of exceeding excursion until below ~11.7hz at full 600 watts power. Due to the 4th order rolloff and the bottomless of design of the Avalanche 18 driver, there really is no chance of ever bottoming this sub unless I did something stupid like play <10hz sine waves at crazy levels. Because of this, there is no need for any type of high pass filter.
I've got 3 of these amps, one for my mains, one for 2 of the subs, and one for the 3rd sub and my center channel. The stock fan noise on these amps is much better than other pro amp alternatives, measuring 53db at 1" from the front faceplate, but I went ahead and modded them using a 39ohm resistor in line of the fan signal to slow them down. Now the fan noise is unregisterable.
13.2ohm.
Planar Sub
Brian,
jeritz, I am interested. Tell me how it works. Does current go thru a ribbon? It is a magnetic motor, right? Is it an 8ohm impedance?
Works just like a planar magnetic ribbon, but it is wider. current from the amplifier output goes trough a foil conductor that is attached by adhesive to a mylar membrane that is in a strong magnetic field. No motors are required. I dont remember the impedance, but a typical mid/tweeter planar magnetic is 1-3 Ohms. You can adjust the impedance by adding resistors with a loss of volume.
Brian,
jeritz, I am interested. Tell me how it works. Does current go thru a ribbon? It is a magnetic motor, right? Is it an 8ohm impedance?
Works just like a planar magnetic ribbon, but it is wider. current from the amplifier output goes trough a foil conductor that is attached by adhesive to a mylar membrane that is in a strong magnetic field. No motors are required. I dont remember the impedance, but a typical mid/tweeter planar magnetic is 1-3 Ohms. You can adjust the impedance by adding resistors with a loss of volume.
SteveCallas, you can get great bass at high SPL down to 10hz.
But most music only goes down to the open string E note on the bass guitar. This is around 41.5hz. Most music has nothing lower. The kick drum is higher.
So your system, especially with 3 cylinders, must have an awsome bass power at 41.5 hz and above.
Do you really play your music loud, like loud in the midrange and treble too?
Or do you listen to your music with a huge bass boost?
I can't imagine how one could really take advantage of a system like yours, except when you have program material that goes way way below most recorded music.
But most music only goes down to the open string E note on the bass guitar. This is around 41.5hz. Most music has nothing lower. The kick drum is higher.
So your system, especially with 3 cylinders, must have an awsome bass power at 41.5 hz and above.
Do you really play your music loud, like loud in the midrange and treble too?
Or do you listen to your music with a huge bass boost?
I can't imagine how one could really take advantage of a system like yours, except when you have program material that goes way way below most recorded music.
Ahhh, but the science of the design is so much sweeter than just tuning low to get deep extension. Typical commercial ported subwoofers usually don't have the greatest of sound quality - why is that? Aside from the driver being used, they use a tune in the 20-35hz area. This high (high in my opinion) tune means port output will play a somewhat significant role in the musical range, and the "bad" side effects associated with port use have the potential of being audible. Ideally, you'd want only the driver to be responsible for all output in the music range....but sealed subwoofers have too many drawbacks in my opinion. The solution is to tune a ported subwoofer low enough that the port output doesn't come into play until very low frequencies, leaving the driver almost 100% responsible for all output in the musical range.
Now how can you tune a sub so low while still maintaining a somewhat flat FR to take advantage of the benefits of a port and not have massive port noise? You gotta go big! A large enclosure provides the needed low end sensitivity to keep things relatively flat very low, and it also provides ampl space to use a large diameter port that will not only keep port velocity in check, but eliminate it as a concern altogether. As for the other "bad" effects, well they are occuring at such low frequencies, where bass is tactile and not audible, that it simply doesn't matter. The only thing that really counts in such low frequencies is how much clean headroom you have, and the ported design easily beats sealed in this regard.
So to wrap it up, a large and low tuned ported design that uses a capable driver is about as good a design as I know how to create, not just for one or two reasons, but a variety. And that <20hz output won't be used much if at all for music, but it makes a HUGE difference for movies.
SteveCallas said:
Steve, most home audio stuff is built small. It makes it cost less. It saves on shipping and handling. Most buyers like that. Most women don't like big stuff. Most people don't understand that the box is part of it.
Sealed boxes start to roll off earlier, but more gently.
I would say that all the sound is coming from the driver always, its just which side of the driver. Being way above the box tuning, I guess the back side cancels out in the box.
As far as port side effects, I've heard of this high velocity rush. But I've never heard it
You imply that most use poor drivers? How so?
Bass distortion should not be that big a deal. There is usually only one bass note at a time. So the distortion will be harmonic and musical.
But, so am I understanding, that you don't play you music at extraordinarily high levels, or with a large bass boost?
Why did you pick BR over TL?
Would you rather have a giant built in enclosure. It could be bigger, tuned even lower, more heavily constructed.
Your info is great! Thanks, Brian
P. S. Sounds like you crossover at 40hz. So you must have full range speakers for the left and the right. How about the center? Do you have a 5.1 reciever that can shunt the low base from the center into the left and the right, inseat of to the subwoofer.
You use it for movies and for music.
Does speaker placement become an issue? Usually the 5.1 systems want the left and right close to the TV sceen. Musical applications want them to be much further appart?
Do you use you center or surround speakers for anything in musical listening? Brian
Have you ever opened any up? Most aren't that impressive.
I definitely don't use any bass boost, as I already have an ideal FR response naturally. And I don't listen at extrordinarily loud levels (yet), as I'm living in an apartment. When I get a home, that will change
What would I possibly gain by using a transmission line?
I already explained, there is a limit at which benefits stop and disadvantages begin to occur. After spending much time in the design phase, 700 liters gave me the best balance and performance.
I don't know if you were asking me or Brian, but I cross over at 80hz on all channels.
What would I possibly gain by using a transmission line?
The answer is sensitivity. The difference is sometimes negliglible but with the right driver and tuning the difference can be huge.
I've never tuned anything as low as your sub, but I have seen that in the 15 - 25 hz tuning range you can easily pick up 6 db with a tl over br with some drivers.
The answer is sensitivity. The difference is sometimes negliglible but with the right driver and tuning the difference can be huge.
I've never tuned anything as low as your sub, but I have seen that in the 15 - 25 hz tuning range you can easily pick up 6 db with a tl over br with some drivers.
Steve, If you had your own home, would you rather have a built in giant subwoofer enclosure?
You say if I took apart some of the commercial subs, I'd find unimpressive drivers. How so? What would I see?
If I am considering a down firing sub, how would I know what driver would have a sag problem? Even worse, and inelastic sag problem? How would I know?
10hz? Why? Did you consider going even lower? Does that reduce sensitivity?
Decades ago, big box BR was really common. Basically you just make sure the box is big enough or bigger to tune at fs. Then you provide a hole, not a port. The hole can be the same area as a driver.
Altec Lansing made theater speakers like this, 15' woofer plus 300 hz horn.
I've made stuff like this too.
Now days, most subs are little boxes, often minimal sized cubes. They have tubes, not holes.
One disadvantage of big box is resonances. Going to these small boxes, you can often eliminate them before the cross over freq.
Martin Colloms shows an example of this.
Your giant enclosure will have a resonance at 29 hz. That is when it is 1/4 of a wavelength. This is how stopped tube organ pipes work.
Do you have any stuffings, dampenings, interior baffles, or such.
TL speakers have always been a special taste. Also, there is the infinte baffle design with a damped aperture. Both these are strange to me.
TL seems like a long BR, but with lots of damping. At the lowest freq this damping might not do much of anything.
Both these two alternate designs do seem curious. I'm not convinced either way.
You say if I took apart some of the commercial subs, I'd find unimpressive drivers. How so? What would I see?
If I am considering a down firing sub, how would I know what driver would have a sag problem? Even worse, and inelastic sag problem? How would I know?
10hz? Why? Did you consider going even lower? Does that reduce sensitivity?
Decades ago, big box BR was really common. Basically you just make sure the box is big enough or bigger to tune at fs. Then you provide a hole, not a port. The hole can be the same area as a driver.
Altec Lansing made theater speakers like this, 15' woofer plus 300 hz horn.
I've made stuff like this too.
Now days, most subs are little boxes, often minimal sized cubes. They have tubes, not holes.
One disadvantage of big box is resonances. Going to these small boxes, you can often eliminate them before the cross over freq.
Martin Colloms shows an example of this.
Your giant enclosure will have a resonance at 29 hz. That is when it is 1/4 of a wavelength. This is how stopped tube organ pipes work.
Do you have any stuffings, dampenings, interior baffles, or such.
TL speakers have always been a special taste. Also, there is the infinte baffle design with a damped aperture. Both these are strange to me.
TL seems like a long BR, but with lots of damping. At the lowest freq this damping might not do much of anything.
Both these two alternate designs do seem curious. I'm not convinced either way.
You've asked this question using different wording a few times now, and I'm still not sure what you mean. My subwoofer already does use a giant enclosure - are you referring to IB or what?
Low quality drivers. Small motor, small magnets, small voice coil, small cone area, small surround, and light weight. Aside from what you can see, the T/S parameters are probably unimpressive as well. High Fs, high Le, low Xmax, low thermal handling, low Vas.
I listed the equation to use earlier in this thread.
Aside from greatly reducing sensitivity, ported designs just won't be able to provide too much below 10hz. If you want to chase single digit frequencies, you have to go sealed and use several drivers and lots and lots of power and EQ. Getting the needed capability below 10hz to actually make it useful requires a LOT of resources, yet the percentage of time you'll see frequencies that low is very small.
As for any resonances, my sub's walls are lined with 2" of poly batting and the port is lined with about 4". My length to diameter ratio is 2.5. My FR does not show any such resonance being an issue.
By a built in enclosure, I mean what ever design you like. It could be IB. But it could be BR or TL also. It could be BR at 10hz, but with a bigger and shorter tube, because the volume is greater. It could have ticker walls. It could be less obtrusive too. It could even use concrete or stucco.
As far a cone sag for downwards firing and a formula. I assume you are mainly talking about the T/S parameters, and mostly xd.
But this doesn't predict sag, well, not directly. I guess compliance sort of does. And fs with that sort of tells you the mass of the moving parts.
Certainly, none of this predicts the inelastic and destructive sag.
Why don't they make more drivers bigger than 18"? Lots of PA speakers use multiple 12's, multiple 15's. I've seen a big JBL cabinet that uses multiple 18's. Cerwin Vega sells e-horns that get used in multiples.
If you have 2 x 18" drivers, you have a beaming problem at a lower frequency than you would have with a single 25"
Why not more giant drivers on the market?
Know of any books that specifically address operation below fs?
Books for downward firing sag issue? Downward firing design as far as leg lenght and size of cabinet bottom?
As far a cone sag for downwards firing and a formula. I assume you are mainly talking about the T/S parameters, and mostly xd.
But this doesn't predict sag, well, not directly. I guess compliance sort of does. And fs with that sort of tells you the mass of the moving parts.
Certainly, none of this predicts the inelastic and destructive sag.
Why don't they make more drivers bigger than 18"? Lots of PA speakers use multiple 12's, multiple 15's. I've seen a big JBL cabinet that uses multiple 18's. Cerwin Vega sells e-horns that get used in multiples.
If you have 2 x 18" drivers, you have a beaming problem at a lower frequency than you would have with a single 25"
Why not more giant drivers on the market?
Know of any books that specifically address operation below fs?
Books for downward firing sag issue? Downward firing design as far as leg lenght and size of cabinet bottom?
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