[Early B.]

Well, this just threw a monkey wrench into my thought process.

Don't be swayed by false information.

[Vince in TX]

Don't be swayed by false information.

Unfortunately I am not knowledgeable enough yet to know what not to believe.   

So you think OB would be fine?

[Early B.]

So you think OB would be fine?

You absolutely can't go wrong with using the best bass on the planet for HT and/or 2-channel audio, and that's OB servo subs. Personally, I use OB servo subs for 2-channel only, and a single 15-inch sealed sub for HT. However, HT is a very low priority for my family. If HT is a prominent form of entertainment in your household, then get the best tools for the job.

 

[mlundy57]

There's a big difference between normal dipole bass performance an servo controlled dipole bass performance. The standard opinion is that OB/dipole can't do low bass.  Folks with this opinion have never heard Danny/Rythmik's direct servo controlled OB bass. Check out show reports from the Lone Star Audio Fest and Rocky Mountain Audio Fest when GR-Research speakers were shown for more info on this type of bass.

[Captainhemo]

Unfortunately I am not knowledgeable enough yet to know what not to believe.   

So you think OB would be fine?

Give Danny  a call and talk to him directly about  your plans
940 592 3400


jay

[Vince in TX]

Give Danny  a call and talk to him directly about  your plans
940 592 3400

jay

Sounds good.   I'll wait until I get closer to pulling the trigger on the kits.  Thanks!

[mijostyn]

This topic comes up now and again in spite of the science being quite old.

First off whether or not a subwoofer system is being used for home theater or music should not make a bit of difference. There is accurate and there is not. If you want a little more explosiveness out of your Hi Fi subs just turn up the volume.

I am only interested in accurate bass in a normal residential setting. The best way to do this under any circumstance is to use two or more (I use 4) sealed subwoofers with copious power ( I use 2000 Watt AB amps damping factor 500) and room control with time and phase alignment. This also requires a crossover with a high pass filter. Ported subs are a problem because they roll off steeply below their cutoff point and the idea of a sub is to go as low as possible using as little power as you can get away with. Open baffle subwoofers are terrible. If you have the opportunity to measure them in a normally sized room you would scratch your head wondering why anyone would ever consider it. The wavelength of 100 hz is about 10 feet, 20 Hz about 32 feet. Any two drivers operating closer than 1/2 the reproduced wavelength are acting as one driver. With an open baffle design you have two drivers, one in front and one in the rear separated by say two feet. So, they are easily acting as one driver below 100 Hz except they are 180 degrees out of phase with each other. The driver cancels itself. I hear you! So, why can these subwoofers make a lot of bass? They can but only at certain frequencies depending on how far away from walls they are, the size of the room and the size of the baffle, etc.  But, if you measure the in room response you can easily go + or - 20 dB. Trying to correct this with room control will require an extremely large amplifier and correction would be incomplete at best. The only benefit I can see in OB subs is that they are cheap and easy to build. A good sealed enclosure is not an easy thing to do. I apologize now if I have upset anyone.

Another note, always put your subs against a wall or in a corner. You will get less nodal behavior in the room. Use 4 subs and you will get almost no nodal behavior. Digital bass management is the best way to fly.

[mlundy57]

This topic comes up now and again in spite of the science being quite old.

First off whether or not a subwoofer system is being used for home theater or music should not make a bit of difference. There is accurate and there is not. If you want a little more explosiveness out of your Hi Fi subs just turn up the volume.

I am only interested in accurate bass in a normal residential setting. The best way to do this under any circumstance is to use two or more (I use 4) sealed subwoofers with copious power ( I use 2000 Watt AB amps damping factor 500) and room control with time and phase alignment. This also requires a crossover with a high pass filter. Ported subs are a problem because they roll off steeply below their cutoff point and the idea of a sub is to go as low as possible using as little power as you can get away with. Open baffle subwoofers are terrible. If you have the opportunity to measure them in a normally sized room you would scratch your head wondering why anyone would ever consider it. The wavelength of 100 hz is about 10 feet, 20 Hz about 32 feet. Any two drivers operating closer than 1/2 the reproduced wavelength are acting as one driver. With an open baffle design you have two drivers, one in front and one in the rear separated by say two feet. So, they are easily acting as one driver below 100 Hz except they are 180 degrees out of phase with each other. The driver cancels itself. I hear you! So, why can these subwoofers make a lot of bass? They can but only at certain frequencies depending on how far away from walls they are, the size of the room and the size of the baffle, etc.  But, if you measure the in room response you can easily go + or - 20 dB. Trying to correct this with room control will require an extremely large amplifier and correction would be incomplete at best. The only benefit I can see in OB subs is that they are cheap and easy to build. A good sealed enclosure is not an easy thing to do. I apologize now if I have upset anyone.

Another note, always put your subs against a wall or in a corner. You will get less nodal behavior in the room. Use 4 subs and you will get almost no nodal behavior. Digital bass management is the best way to fly.

I too am only interested in accurate, well defined bass.

You are arguing theory with limited or no experience with well designed and executed open baffle bass. Done properly, OB bass is exceptional. My system, with Dual 12” driver GR-Research stereo OB Subs, has an in-room response of -4dB at 16Hz in a 12’x14’x8’ room. I use REW for measurment and have had my system in rooms from 12’x14’x8’ to 20’x25’x14’ with the same results.

The one thing my sealed servo sub does better than the OB subs is shake the couch at 10Hz. So, while I would agree that sealed subs are better than OB subs for infrasonic frequencies below 20Hz, OB subs can be better at frequencies from 20Hz and above.

[Early B.]

This topic comes up now and again in spite of the science being quite old.
Open baffle subwoofers are terrible.  ..... The only benefit I can see in OB subs is that they are cheap and easy to build.

OK, sounds like you answered your own question as to why you believe most OB subs suck -- because they're cheap and the DIY crowd building these things aren't operating on the basis of any real science. So yeah, a typical OB sub with a $100 driver usually doesn't go very low. You get what you pay for.

When we speak of OB subs on the GR Research circle, we're talking about a completely different approach to OB design. Just look at 'em -- they're not drivers that someone screws onto a piece of MDF. There's a complex servo technology around them that will make your head spin. They go as low as any sealed sub and do so far more cleanly. We can't describe it in words -- you have to hear it for yourself. And when you do, there's a 99% chance you'll change your attitude about what an OB sub can do.

[mlundy57]

Early B touched on a point I didn’t address. A pair of these dual 12” driver OB subs is going to set you back around $2,000 not counting the cabinets.

[Early B.]

One more thing -- the "sub" in subwoofer means that it goes below 20Hz. If a so-called subwoofer doesn't go under 20hz, it's just a woofer -- it barks, but it doesn't roar. Thus, the majority of cheap OB "subwoofers" are misclassified and shouldn't be compared to true subwoofers. 

[emailtim]

... if you measure the in room response you can easily go + or - 20 dB. Trying to correct this with room control will require an extremely large amplifier and correction would be incomplete at best. ...

FWIW, I just made some new filters.  6dB low shelf and 6dB high shelf to get the raw OB/Dipole subs relatively flat (red plot) from [14 - 250]Hz.  Nowhere near 40dB of correction required and still get triple digit SPL.

[hawkeyejw]

FWIW, I just made some new filters.  6dB low shelf and 6dB high shelf to get the raw OB/Dipole subs relatively flat (red plot) from [14 - 250]Hz.  Nowhere near 40dB of correction required and still get triple digit SPL.

That looks really impressive. Do you listen to music exclusively or do you also use this system for watching TV/movies?

[emailtim]

That looks really impressive. Do you listen to music exclusively or do you also use this system for watching TV/movies?

That system is in the 2-channel music room, but there is no reason why it couldn't be used for HT.

[hawkeyejw]

That system is in the 2-channel music room, but there is no reason why it couldn't be used for HT.

Thanks, I was just curious to hear your impressions for HT if you'd tried it. Looks like an enjoyable room either way.

[emailtim]

Thanks, I was just curious to hear your impressions for HT if you'd tried it. Looks like an enjoyable room either way.

I have shifted away from sealed subs and towards OB/Dipole subs over time because I think they blend better for music.  If you are looking for crash/boom/bang, a sealed sub will pressurize the room more, but shotgun blasts and anti-matter explosions on space stations in a vacuum don't occur much in music. 

When I was young, I was all about the crash/boom/bang, but that has waned over the years.  I realized I listened to my HT more with the sealed subs turned off and never turn off the OB/Dipole subs.  I think it comes down to what floats YOUR boat.

[Tyson]

Looking at your measurements - that's the other thing about OB subs, MUCH easier to get flat in-room response than with box subs.  With box subs you really are stuck with using a swarm approach, either that or MASSIVE amounts of EQ.  OB subs sidestep that problem rather neatly.