Thank you for your support.
Unfortunately I already own the 12"s. So no way.
But honestly I don't like the sound of 15", a bit too slow. I would prefer having more motors spread over the same cone surface amount.
The idea is to have 2 towers, one for each channel (stereo). I own 2 dayton SA1000.
Sealed box is my preferred solution as a rule of the thumb, but I faced a not positive experience with a couple dual opposite peerless xxls 12" 835017 in 3.2 stuffed volume. (please see attached picture) Below 35 Hz there was not much output. Even if I boosted at 25Hz +8db, I can't here much difference. I assume it depends on lower Qt (0.39). But fs was ok on free air 21.5 Hz. So in the end they will cover the 40-180Hz range only.
I think that 30-35 hz tuning is not ideal for my application. Too high. I need reinforcement below 35 Hz. I was in doubt if make a ported in downsize 8.5cf^3 tuned at 22Hz (removing the 40-50Hz bump by the internal eq) or give thrust again to sealed option, hoping that using more speaker numbers with higher qt could help. Maybe I should make 2 mokups and check
Unfortunately I already own the 12"s. So no way.
But honestly I don't like the sound of 15", a bit too slow. I would prefer having more motors spread over the same cone surface amount.
The idea is to have 2 towers, one for each channel (stereo). I own 2 dayton SA1000.
Sealed box is my preferred solution as a rule of the thumb, but I faced a not positive experience with a couple dual opposite peerless xxls 12" 835017 in 3.2 stuffed volume. (please see attached picture) Below 35 Hz there was not much output. Even if I boosted at 25Hz +8db, I can't here much difference. I assume it depends on lower Qt (0.39). But fs was ok on free air 21.5 Hz. So in the end they will cover the 40-180Hz range only.
I think that 30-35 hz tuning is not ideal for my application. Too high. I need reinforcement below 35 Hz. I was in doubt if make a ported in downsize 8.5cf^3 tuned at 22Hz (removing the 40-50Hz bump by the internal eq) or give thrust again to sealed option, hoping that using more speaker numbers with higher qt could help. Maybe I should make 2 mokups and check
Attachments
If you can't hear under 35hz, it's because the SPL was low, or you were sitting in a null. You don't hear 35hz or 25hz the way you hear 100hz of course. It takes a lot more SPL to hear the true tone of 30~35hz or lower. Much harder lower. And if you're sitting far from them, you lose a lot of SPL just to distance. So unless you're hitting 115db at 30hz at your listening position, you probably just don't have enough SPL to satisfy if you're not liking the output you're currently getting with boosting. You can check this by examining your excursion or measuring SPL. And it may be your signal pathway or gain structure limiting things.
Based on your comments though it sounds like bass reflex isn't for you. Sealed will do better. And having 8 drivers sealed will simply do better in general for your needs and ideas of more motors. You can shape it however you want without altering the cabinet later on which is a huge appeal to sealed for music to me.
Here's what a tower of 4 x GRS12 drivers in dual opposed, sealed, looks like at 1000w:
GRS 12SW4HE x 4
8.5 ft^3 sealed
1000w at 4ohm
1 meter
But, let's look at bass reflex again just for fun:
You wouldn't need 8 drivers for bass reflex. You could do 2 drivers dual opposed bass reflex and tune to 20hz no problem. Two towers with 2 drivers each.
For example (just one tower):
GRS 12SW4HE x 2 in Dual Opposed
Bass Reflex 8 ft^3 net internal volume
Port 20hz
500w power
1 meter
The 2nd tower adds +6db to this bandwidth.
Excursion is good to 17hz. High pass filter needed under 17hz unless you have no content happening under 17hz then you could get away with not using one. Or if your amp has one built in, that will already do it. Though with less finesse on control.
Air velocity looks good less than 18m/s at 20hz with a 7.7" diameter port at 33.4" length. Lets convert to a slot port.
Converting to a slot port:
So maintain 7.7" diameter area = 46.6 square inches area as any size slot dimension and the length of 55.95cm (56cm) which is 22" length and you have that 20hz tuning in that volume.
Very best,
Based on your comments though it sounds like bass reflex isn't for you. Sealed will do better. And having 8 drivers sealed will simply do better in general for your needs and ideas of more motors. You can shape it however you want without altering the cabinet later on which is a huge appeal to sealed for music to me.
Here's what a tower of 4 x GRS12 drivers in dual opposed, sealed, looks like at 1000w:
GRS 12SW4HE x 4
8.5 ft^3 sealed
1000w at 4ohm
1 meter
But, let's look at bass reflex again just for fun:
You wouldn't need 8 drivers for bass reflex. You could do 2 drivers dual opposed bass reflex and tune to 20hz no problem. Two towers with 2 drivers each.
For example (just one tower):
GRS 12SW4HE x 2 in Dual Opposed
Bass Reflex 8 ft^3 net internal volume
Port 20hz
500w power
1 meter
The 2nd tower adds +6db to this bandwidth.
Excursion is good to 17hz. High pass filter needed under 17hz unless you have no content happening under 17hz then you could get away with not using one. Or if your amp has one built in, that will already do it. Though with less finesse on control.
Air velocity looks good less than 18m/s at 20hz with a 7.7" diameter port at 33.4" length. Lets convert to a slot port.
Converting to a slot port:
So maintain 7.7" diameter area = 46.6 square inches area as any size slot dimension and the length of 55.95cm (56cm) which is 22" length and you have that 20hz tuning in that volume.
Very best,
You perfectly get the point. According to measurements the listening position is quite close to null....damn it!
Furthermore in general the SPL was not enough. That's why I thought to use more speakers. As far as I know you better manage the room modes , getting a more diffuse fields of sound. In particular if you stuck the sub one above the other you get the additional benefit of having different height of the sound source.
You reflex simulation gave me food for thought. Probably I could check if 2 isobaric dual opposite could be a valid solution. For sure I don't like the idea to give up emitting surface area, but on the other hand it halves the volume. Also the second harmonic is lower on isobaric. And it could be a trick for cheap speaker. But honestly I really make some effort to figure out a decent box design (aesthetically pleasing) with an dual opposite isobaric
Furthermore in general the SPL was not enough. That's why I thought to use more speakers. As far as I know you better manage the room modes , getting a more diffuse fields of sound. In particular if you stuck the sub one above the other you get the additional benefit of having different height of the sound source.
You reflex simulation gave me food for thought. Probably I could check if 2 isobaric dual opposite could be a valid solution. For sure I don't like the idea to give up emitting surface area, but on the other hand it halves the volume. Also the second harmonic is lower on isobaric. And it could be a trick for cheap speaker. But honestly I really make some effort to figure out a decent box design (aesthetically pleasing) with an dual opposite isobaric
Last edited:
Does this comparison use the published TS parameters for both drivers? Considering your experience with the 12s, how much confidence do you have in its validity?
That said, I realize that lots of Vd in a large, sealed box is rather adjustable with EQ.
Yes, that's with just published T&S. I don't have a GRS 15SW4HE to measure, but I would if someone sent me one. These are very budget drivers, all of these here, so I wouldn't expect the T&S to be close. I find sample variation with every driver from the same series even, sometimes significant. But for $34~96 per driver, I expect nothing frankly. They're truly budget level drivers. But they happen to work well in practical outcome for cost as subwoofers, at least, since we can't really hear these frequencies with the same scrutiny as mids or treble nor can we really hear minor distortion at these low frequencies, etc. So there's a lot of wiggle room in that way with going cheap on these drivers in this context.
I imagine the Qts is larger than they suggest and the motor isn't strong. They will basically always do better in more volume than T&S predicts. I do find the xmax and power handling to be pretty close. I've taken all my GRS drivers to xmech (ie, I took it to the point of it clapping and slapping just to see where that was) and they recover and handled it fine. So the 12mm~13mm xmax ratings are good and they will get there without a problem. I took both my GRS12SW4HE's in this build out past 12mm each (one way) by taping a card to it with a 1" measurement side and played 30hz and increased levels until I could see the 1" marker edge as a blur beyond the marker, so it was doing a good 25mm peak to peak for that to happen and it was sounding fine. These can probably go a bit farther, maybe 2~3mm more. The GRS 12SW4, I have several of them, they're about 8mm xmax, but I routinely take them closer to 11~12mm xmax and then limit them there just under xmech limits where I found by pushing them until they clapped. I use compressors to keep them from hitting that limit. They've working great. So while the T&S values measure differently, the drivers behave fine up to their intended xmax limits for the power expected, and they all do better in more volume (and even do fine in free air).
Very best,
If you made a break in, did you also measured before and after in order to check what is changed?
Fun thread
Amazing sub for the money.
2x12 sub was more than enough
over the years in various entertainment rooms.
Heck 1x12 got me in enough trouble more than once.
As with any thread with budget drivers.
they love saying all the " errors" found
but i liked the minimal approach.
to see if audible
Having run countless generic sealed 12" subs.
All being different of course.
Over time you just realize
1 cubic feet for a 10" 2 cubic feet for 12" per driver.
Sealed being incredible forgiving regardless.
With high pass, crossover and EQ
nitpicking subs isnt much.
They hit regardless, but if you can actually get .7 Qtc
if Qts isnt out the roof. It is a better driver, not bloomy.
With this specific driver 2x12 does very well in 4 cubic feet.
So agree the box could be little larger.
For movies = dont matter.
For certain music= does make a difference.
For rock and jazz= no
usually relax on the EQ for that stuff
Amazing sub for the money.
2x12 sub was more than enough
over the years in various entertainment rooms.
Heck 1x12 got me in enough trouble more than once.
As with any thread with budget drivers.
they love saying all the " errors" found
but i liked the minimal approach.
to see if audible
Having run countless generic sealed 12" subs.
All being different of course.
Over time you just realize
1 cubic feet for a 10" 2 cubic feet for 12" per driver.
Sealed being incredible forgiving regardless.
With high pass, crossover and EQ
nitpicking subs isnt much.
They hit regardless, but if you can actually get .7 Qtc
if Qts isnt out the roof. It is a better driver, not bloomy.
With this specific driver 2x12 does very well in 4 cubic feet.
So agree the box could be little larger.
For movies = dont matter.
For certain music= does make a difference.
For rock and jazz= no
usually relax on the EQ for that stuff
I have a few of these drivers, I've measured them cold from the box and after many hours (over a year) of use. The measurements are not crazy different unless its measured hot, as in, directly after it was running non-stop for a good hour.
Very best,
It's been fun. I've taken it to full excursion and it behaves pretty well. If I did anything different, I would do the finish different (one tone, shellac instead of stain), I would do a larger box I think (closer to 4 ft^3, based on post-measurements I did), and I would probably do the internal bracing differently, such as just some cross-studs instead of a window, just because it was extra effort without any real gain. Lastly, I would use different drivers. I like the GRS drivers, I have many of them, but in this case, I would probably switch to an 8ohm driver so that I could wire them in parallel instead at 4ohm. I could wire these in 2ohm parallel and I have amps that can do that, but I don't like all the extra heat (Florida). It would cost more for the drivers, but it would be cheaper to power them. Of course, I'd go bigger if I could, but I didn't want to use big drivers for this, as the space it was meant for was smaller and I wanted it to tuck away, near field. It's more than enough for 30hz and up music purposes. I don't stretch its legs close at all, other than when measuring or pushing it just to study its behavior.
Very best,
Hi .
Would it be possible for you to measure vibrations of the box in another situation : one speaker active , the other passive but vertically , with passive radiator facing floor and active speaker facing ceiling ? for reasons of space i am considering this configuration .
thanks
Would it be possible for you to measure vibrations of the box in another situation : one speaker active , the other passive but vertically , with passive radiator facing floor and active speaker facing ceiling ? for reasons of space i am considering this configuration .
thanks
I would add some comments about vibration measurements. I am a vibration engineer that deal with vibration measurements and makes daily FEM calculations.
Usually the best is to plot velocity (mm/s). Acceleration plot is mostly used at higher frequency (above about 500Hz and used to check the limit for the electronic device, typically 5g limit). My suggestion is to drive the speaker with White noise up to 1kHz, to record the time signal and then to make the FFT of it in order to check the spectra. If you drive the system with a single tone (30 Hz) is not the best in my opinion. The reason is that basically it cut out all the box resonance that are located above 200 Hz roughly for a standard box . Please check below the a model of a dual opposite sub box a made time ago, the same of the picture a insert in my previous post. Half model shown (symmetrical). Speaker modelled by mean of rigid links + lumped mass, for who is familiar with FEA nomenclature. In that case the first resonance was at 339Hz. What happens below the first mode is just a forced response, but is a good idea to check what happen when the system is in resonance ( exciting frequency = natural frequencies of the model)
Usually the best is to plot velocity (mm/s). Acceleration plot is mostly used at higher frequency (above about 500Hz and used to check the limit for the electronic device, typically 5g limit). My suggestion is to drive the speaker with White noise up to 1kHz, to record the time signal and then to make the FFT of it in order to check the spectra. If you drive the system with a single tone (30 Hz) is not the best in my opinion. The reason is that basically it cut out all the box resonance that are located above 200 Hz roughly for a standard box . Please check below the a model of a dual opposite sub box a made time ago, the same of the picture a insert in my previous post. Half model shown (symmetrical). Speaker modelled by mean of rigid links + lumped mass, for who is familiar with FEA nomenclature. In that case the first resonance was at 339Hz. What happens below the first mode is just a forced response, but is a good idea to check what happen when the system is in resonance ( exciting frequency = natural frequencies of the model)
Attachments
Last edited:
I'll see if I can prop it up. It's not hard to do that. It will be the same though. A passive radiator does not cancel out the forces and reduce box vibrations. Both active drivers is what does that as they have equal opposed forces. So there's no benefit to the vibration measurement of an active driver and passive driver, you no longer are getting the vibration canceling. So building that is not for vibration reduction.
Very best,
It would be great to have your experience and equipment for sure!
Do you think that matters in a system that has a limited bandwidth that doesn't ever have output at 200hz, nor 1khz? This particular system is being limited to 10hz~100hz bandwidth via DSP. I would think it would make sense to measure vibration such as velocity and acceleration in its working bandwidth?
Very best,
If the bandwidth is limited up to 200 hz it is ok to stop the input signal at the same frequency, but......because of Nyquist quote "The Nyquist theorem defines the minimum sample rate for the highest frequency that you want to measure. The Nyquist rate is 2x the given frequency to be measured accurately". So please sample rates highest frequency at minimum 400Hz. Also the blue tac you are using for attaching the accelerometer has a powerful filtering effect, so everything above about 500hz is cutted out. For professional business is used wax for fast fastening, otherwise is screwed.
By the way, is better to use white noise excitation, (standard is 20-20khz, constant power over the frequency range) and then limit the post processing analysis (FFT) to 200hz than simply use a single tone at 30hz. In this way the vibration output is an rms value that takes in account everything in the operating range. The value is more significant than a single frequency
By the way, is better to use white noise excitation, (standard is 20-20khz, constant power over the frequency range) and then limit the post processing analysis (FFT) to 200hz than simply use a single tone at 30hz. In this way the vibration output is an rms value that takes in account everything in the operating range. The value is more significant than a single frequency
Many years ago i observed an anomaly on a nearfield measurement of a bass speaker in ported enclosure . I finally understood it was due to the box "dancing" on the floor . It was movement and no vibration . I just want to know if arranging the speakers that way does any improvement .
Thanks
Ok, well, if you plan on doing this with a passive radiator, then no it will not improve the vibration of the box and it will still be able to dance/wander on the floor if its not high enough mass to stay put under load. Active + Passive = no opposed forces to cancel = full vibration on the box still.
If you are however considering two active drivers in opposition with the same polarity, then yes, it will cancel out the box vibrations and it will not dance at all and will not wander around. It doesn't matter if the drivers are horizontal or vertical. All that matters is that they are opposed and active with the same polarity. Do that and the opposed forces cancel = no vibration on the box = no dancing or wandering on the floor.
Very best,
I agree completely with you ; but does your accelerometer only mesure vibrations and not tiny movements of the box . These movements could be avoided by mass or fixing to the floor or simply by the switch of the box ?
It measures a few things, I mainly focused on looking at acceleration and angular velocity changes. So if it moves, it's noted in one or the other and in which axis.
The sub moves because its mass being low. If you put some weight on it, like some books, or a heavy stone block, it will no longer walk around the room. How much weight you need to add depends uniquely on the individual sub.
Fixing it to the floor will couple it and then the vibration is transferred to what its couples to. This could be fine if its concrete, but if it's subfloor you will not like the results probably as then the whole floor will vibrate.
Or, if you want it to completely not vibrate, simply have pairs of drivers in opposition in same polarity and they'll cancel each other out in any orientation (vertical is fine) as long as they're aligned opposed physically. The only issue with what you're describing is the passive driver. If you go with two active drivers you can do what I did here and eliminate box vibrations. The extra driver lets you get more SPL and more excursion as a system so you can house curve it to be similar to what a passive radiator build would do.
Very best,