Single 12" vs dual 10" subwoofers

[watchnerd]

You mean to tell me a 6 foot dresser (for example) doesn't influence room modes??? It basically changes the room shape and I'm pretty sure there's been studies on room shape and room modes.

I think you're confusing standing waves (room nodes) in the resonant bass frequencies with other phenomena.

Your hypothetical 6 foot dresser would match the wavelength of a signal of about 190 Hz.

Above Schroeder, you're dealing with other phenomena in the deflector/diffusor range.

 

[Koeitje]

In regards to two 10" vs one 12" subwoofer.
As long as the 10" subs holds high quality, two of those will general give you higher output and lower distortion compared to one 12". Obviously this can change if the quality differs.

King of subwoofer is horn by the way. But a true horn loaded subwoofer takes a lot of space.

I remember some website that showed of how some guy built a horn-loaded subwoofer underneath his floor .

 

[watchnerd]

King of subwoofer is horn by the way. But a true horn loaded subwoofer takes a lot of space.

I've seen pictures of people who built floor-mounted transmission line subwoofers, with the horn throat going into the basement.

 

[Wes]

furniture reflects what bass frequencies at what levels??

I'm with you on absorption for a big soft sofa as a qualitative factor, but haven't seen any quantification.

I'm with you in Rockland, as Allen Ginsburg once said on the "I'm pretty sure there's been studies" part too.

 

[Wes]

I've seen pictures of people who built floor-mounted transmission line subwoofers, with the horn throat going into the basement.

this would be a most excellent pictorial contribution to the photos of listening rooms thread

 

[Bjorn]

I remember some website that showed of how some guy built a horn-loaded subwoofer underneath his floor .

Something like this?

Doesn't have to be that big, but it's easily become fridge size.

 

[Koeitje]

Something like this?
View attachment 65389


Doesn't have to be that big, but it's easily become fridge size.
View attachment 65391

No, this is amateur work compared to what I am talking about. I'm going to try and find it.

Here it is:
https://news.softpedia.com/news/Mee...-and-Ultimately-Biggest-Subwoofer-90193.shtml

Too bad the link to the actual article is dead (links to some Jesus loving site), but there are still 3 pictures.

 

[Peas]

The SB1000 has a very steep roll-off, so it has a boost and a subsonic at the lower end as pre-EQ.

This looks good on paper, but may interfere with your plans. A flat or "natural" roll-off is easier to handle (CB = 12 dB/oct. slope). One wants that green curve in his room, not in an anechoic measurement. Especially, when you place the subwoofers directly next to a wall, which is not the worst idea to avoid SBIR, a slow roll-off only needs little EQ and will then go really deep down as the room adds up to 12 dB/oct. below the lowest room mode. It's less in practice, but just to give an idea what the in-room response may be.

 

[georgeT]

I swear people in this thread have "listened" more to theoretic studies than they have listened to speakers in their own room.

 

[Peas]

No, this is amateur work compared to what I am talking about. I'm going to try and find it.

Here, it is too:

https://gizmodo.com/horn-subwoofer-takes-up-crazy-mans-entire-basement-5025867

 

[watchnerd]

Here, it is too:

https://gizmodo.com/horn-subwoofer-takes-up-crazy-mans-entire-basement-5025867

That's the one I was thinking of, too.

 

[amirm]

I think you are mistaken. For non-rectangular rooms, the process gets much more complicated. Here is a link to an article by Dr Toole in Audioholics on sound field management.

Why go there when you can read my article:

https://www.audiosciencereview.com/forum/index.php?threads/subwoofer-low-frequency-optimization.15/

And more in-depth:

https://www.audiosciencereview.com/...s/computer-optimization-of-room-acoustics.12/

 

[Koeitje]

For room correction for the subs, would a Minidsp 2x4 be enough or do I need the 2x4 HD?

 

[Frank Dernie]

For instance, you could get 12" driven/12" passive radiator sealed subwoofer(s), with an equivalent area to a 17" woofer

Excuse me for being pedantic but a 12" driven unit in a box with a passive radiator is equivalent to a 12" bass reflex, since the passive resonates in the same way as a port to extend bass, so it is neither "sealed" nor equivalent to a 17" driver.

Here, it is too:

https://gizmodo.com/horn-subwoofer-takes-up-crazy-mans-entire-basement-5025867

Around 30 to 40 years ago there was an article about a guy who had done something like that in a UK HiFi magazine.
He had made the shuttering the correct shape for making a poured concrete pair of bass horns under the floor (and offered readers who wanted to do the same a loan for free!).
There were tannoy dual concentrics built into the corners of his room and were back loaded by the horn which folded down, away then back and up again with the two huge horn mouth openings between the drivers.
It was very similar to this one in shape under the floor.

 

[Jukka]

Excuse me for being pedantic but a 12" driven unit in a box with a passive radiator is equivalent to a 12" bass reflex, since the passive resonates in the same way as a port to extend bass, so it is neither "sealed" nor equivalent to a 17" driver.

That is true. How theoretical must one get to think that 12" active + 12" passive equals 2x 12" active drivers. Actually, is not true even theoretically!

 

[detlev24]

For room correction for the subs, would a Minidsp 2x4 be enough or do I need the 2x4 HD?

It seems the main differences are: much more processing power + native USB audio-streaming, on the '2x4 HD' version. The '2x4' would work; but has a biquad limit of 5 [with the "2x4 Advanced" plug-in / choice for one free plug-in] vs. 10 on the '2x4 HD'; see "Appendix A. Notes on using an external 2x4 for the subs". The latter would allow for more flexibility and might give better results, under some circumstances.

Generally, for DSP, there is never enough processing power available.

Excuse me for being pedantic but a 12" driven unit in a box with a passive radiator is equivalent to a 12" bass reflex, since the passive resonates in the same way as a port to extend bass, so it is neither "sealed" nor equivalent to a 17" driver. [...]

You are right that a passive radiator works similarly to a tuned port. However, due to absence of a port opening, there is no air turbulence which would become audible at higher SPL. Furthermore, the passive radiator must have the same excursion limits as the driven unit, to avoid distortion.

Pardon me! This "sloppy" statement was not with regards to the working mechanisms of subwoofers; but simply regarding the combined cone area, which is equivalent to the area of a 17" driver's cone. Yet, the enclosure is physically sealed, due to absence of an opening for exchange of inner and outer air masses.

That is true. How theoretical must one get to think that 12" active + 12" passive equals 2x 12" active drivers. Actually, is not true even theoretically!

2x 12" driven drivers do also not follow the exact same physical properties, neither theoretically, as 1x 17" driven driver.

 

[Koeitje]

It seems the main differences are: much more processing power + native USB audio-streaming, on the '2x4 HD' version. The '2x4' would work; but has a biquad limit of 5 [with the "2x4 Advanced" plug-in / choice for one free plug-in] vs. 10 on the '2x4 HD'; see "Appendix A. Notes on using an external 2x4 for the subs". The latter would allow for more flexibility and might give better results, under some circumstances.

Generally, for DSP, there is never enough processing power available.

The plan is to use a IOTAVX 7.1 4K processor which has one sub out and its own room correction (which I don't expect to be good). So I will be connecting the minidsp to the sub out and use it from there. Best is to probably use REW first to get the subs right then use the build in correction to fix the rest. But maybe that's a bad plan, who knows .

 

[jhaider]

For room correction for the subs, would a Minidsp 2x4 be enough or do I need the 2x4 HD?

I would not use the unbalanced 2x4. The preout voltage is too low. I have successfully used balanced 2x4. 2x4HD allows longer delays and has standard voltage on the RCA preouts. It is also marginally easier to use if your processor or subs only have RCA inputs. No need to cut cables and make sure they’re wired correctly into the terminal.

Multisub for room modes doesn't have much benefit unless you want to seat 5+ other audiophiles in a theater and have heavy bass trapping in the room.

Quite a feat of rhetoric there: internally inconsistent, yet on its own neither piece makes sense!

a 12" driven/12" passive radiator sealed subwoofer(s), with an equivalent area to a 17" woofer - or double 10" driven sealed subwoofer(s), with an equivalent area to a 14" woofer. Cabinet vibrations should be lower as well, as the subwoofer(s) simply have more weight.

Careful there.

First, as others have explained PR is the functional equivalent of a port. It does not increase volume displacement. It does increase efficiency over a narrow bandwidth, and decreases efficiency below that bandwidth. As discussed, the advantage of PR over port is no pipe resonances.

Also, all else equal a PR sub cabinet will vibrate more than a closed or vented box. The reason is the movement of the heavily mass loaded PR cone.

King of subwoofer is horn by the way. But a true horn loaded subwoofer takes a lot of space.

I would say the opposite. Horns (inasmuch as any device that fits into a small room and outputs these long wavelengths can accurately be named “horn”) are the absolute worst for deep bass. The bandwidth limitations are crippling, and resonances above that tiny bandwidth are staggeringly bad. There is also limited ability to pressurize the room below cutoff. Theoretically the best solution is the common, humdrum one: multiple closed boxes. Smoothest frequency response (in passband and above), strongest deep bass (can excite modes below nominal cutoff), sufficient efficiency. While your big black eyesore above may be cheaper to make (fewer drive units to buy) and lighter, I suspect there is no way it will outperform multiple closed box woofers in the same volume, even if collocated. From a marketing perspective there is no gobbledegook one can craft about such a basic subwoofer design though.

Build your own subwoofer(s) and you'll have premium parts compared to most retail subs, and save a fortune.

That only holds by ignoring the price of your time and capital (tools, workspace), and are either an accomplished woodworker or willing to accept sub-professional appearance. If you subcontract the build to a commercial artisan you will invariably pay much more for equivalent performance. However, you will also get subs that are designed for your space. Politically that can be helpful because all relevant actors can have a say in the shape and finish, thus giving some measure of buy-in. Practically that can be the difference between subs in the room and no subs.

 

[Frank Dernie]

You are right that a passive radiator works similarly to a tuned port. However, due to absence of a port opening, there is no air turbulence which would become audible at higher SPL. Furthermore, the passive radiator must have the same excursion limits as the driven unit, to avoid distortion.

Pardon me! This "sloppy" statement was not with regards to the working mechanisms of subwoofers; jet simply regarding the combined cone area, which is equivalent to the area of a 17" driver's cone. Yet, the enclosure is physically sealed, due to absence of an opening for exchange of inner and outer air masses.

It isn't sloppy, it is wrong.
The air displaced by the passive radiator and the air moving in and out of the port do exactly the same. There is indeed a possibility of air turbulence from the port, but also around the periphery of the passive radiator and bass driver, whether it is audible or not tends to depend on the design.
If both units had identical movement it would be equivalent to a 17" driver, but they do not. The passive radiator only moves during its tuned resonance band it is in no way similar to an extra cone and in every way equivalent to a port. It is never equivalent to a 17" driver because when the passive radiator is at its maximum excursion the main driver is stationary.
It is also not similar acoustically to a sealed box type of speaker since the passive radiator behaves like an opening.
It is just another type of a 12" reflex sub.

 

[Senior NEET Engineer]

Quite a feat of rhetoric there: internally inconsistent, yet on its own neither piece makes sense!

What do you mean? Please explain what you disagree with...