Passive Sub? -- Renovating an audio system just out of storage

[T Moon]

I am in need of any advice on acquiring a passive sub that will be driven by a 360W dedicated amp. At this point, I <think> I am leaning toward 10" - 12" driver.

Room is a very hard surface 14' x 14'. One wall is primarily glass, one wall is open to another space, the other 2 walls and ceiling is painted sheet rock, floor is bamboo. Working space is approximately 7' (between speakers) and 8' (from the speakers to seating). Seating and speakers are placed on the 2 painted sheet rock walls. I am not interested in high volume.

I have been advised that I should be looking for a subwoofer that is capable of 500W peak power handling. My preference is used.

 

[j_garcia]

Not many prebuilt passive subs these days, unless you are able to go DIY. When you say "open to another space" you need to factor that in space wise. Is that total space a lot larger than the 14x14? The additional space may benefit you a bit, because 14'x14' enclosed would be a bad scenario; square rooms are your enemy for bass and require different considerations.

Most of the ones I see are In-wall variants, and the others are either super cheap or very expensive. Peak power handling isn't something you can figure until you know what the sub is, because that won't be as much a factor in determining the sub really.

 

[lovinthehd]

Budget? Why was it advised to seek a peak power handling of 500W? What amp particularly, is it 360W at 8 ohm or 4 ohm? What extension (lowest frequency response) are you thinking about?

Just took a look at an ebay search, was some pro-style Behringer and JBL subs....as was said commercial home audio passive subs are kinda rare (most seem to be in-wall models). Willing to DIY it?

 

[TLS Guy]

I am in need of any advice on acquiring a passive sub that will be driven by a 360W dedicated amp. At this point, I <think> I am leaning toward 10" - 12" driver.

Room is a very hard surface 14' x 14'. One wall is primarily glass, one wall is open to another space, the other 2 walls and ceiling is painted sheet rock, floor is bamboo. Working space is approximately 7' (between speakers) and 8' (from the speakers to seating). Seating and speakers are placed on the 2 painted sheet rock walls. I am not interested in high volume.

I have been advised that I should be looking for a subwoofer that is capable of 500W peak power handling. My preference is used.

You will have to build that yourself. I have just done a sub design for another member.

 

[T Moon]

Not many prebuilt passive subs these days, unless you are able to go DIY. When you say "open to another space" you need to factor that in space wise. Is that total space a lot larger than the 14x14? The additional space may benefit you a bit, because 14'x14' enclosed would be a bad scenario; square rooms are your enemy for bass and require different considerations.

Most of the ones I see are In-wall variants, and the others are either super cheap or very expensive. Peak power handling isn't something you can figure until you know what the sub is, because that won't be as much a factor in determining the sub really.

I knew someone was going to ask me that...

First of all; my thanks for your quick response!

RE: what size is the room?
So you need to picture a rectangle that is 14' x 26'. At the end of the long wall is the glass. At the opposite end of that rectangle is the back side of a utility closet. That closet intrudes into the seating wall such that it takes a 3' x 12' rectangle away from the larger (14' x 26') rectangle.

RE: Square bad
I work with what I have.

RE: Who made the reccomendation on total peak power?
When I unpacked the audio pieces, some of them where not working correctly. I went through of phone numbers getting responses along 'that nobody works on audio stuff anymore' until I found someone who did board level repairs on audio stuff. So, he has 30+ years of experience and he went through my stuff finding one of the preamps was not with us any more and not worth repairing. Another thought from him was 'maybe look at car subs'. He seems competent from my pespective and has not done anything that I disagree with.

RE: DIY
This is the sort of project that I haven't done in decades. At this point I have neither the space nor the tools.

Hope this helps and that it is not TMI.

 

[T Moon]

I knew someone was going to ask me that...

First of all; my thanks for your quick response!

RE: what size is the room?
So you need to picture a rectangle that is 14' x 26'. At the end of the long wall is the glass. At the opposite end of that rectangle is the back side of a utility closet. That closet intrudes into the seating wall such that it takes a 3' x 12' rectangle away from the larger (14' x 26') rectangle.

RE: Square bad
I work with what I have.

RE: Who made the reccomendation on total peak power?
When I unpacked the audio pieces, some of them where not working correctly. I went through of phone numbers getting responses along 'that nobody works on audio stuff anymore' until I found someone who did board level repairs on audio stuff. So, he has 30+ years of experience and he went through my stuff finding one of the preamps was not with us any more and not worth repairing. Another thought from him was 'maybe look at car subs'. He seems competent from my pespective and has not done anything that I disagree with.

RE: DIY
This is the sort of project that I haven't done in decades. At this point I have neither the space nor the tools.

Hope this helps and that it is not TMI.

 

[TLS Guy]

I knew someone was going to ask me that...

First of all; my thanks for your quick response!

RE: what size is the room?
So you need to picture a rectangle that is 14' x 26'. At the end of the long wall is the glass. At the opposite end of that rectangle is the back side of a utility closet. That closet intrudes into the seating wall such that it takes a 3' x 12' rectangle away from the larger (14' x 26') rectangle.

RE: Square bad
I work with what I have.

RE: Who made the reccomendation on total peak power?
When I unpacked the audio pieces, some of them where not working correctly. I went through of phone numbers getting responses along 'that nobody works on audio stuff anymore' until I found someone who did board level repairs on audio stuff. So, he has 30+ years of experience and he went through my stuff finding one of the preamps was not with us any more and not worth repairing. Another thought from him was 'maybe look at car subs'. He seems competent from my pespective and has not done anything that I disagree with.

RE: DIY
This is the sort of project that I haven't done in decades. At this point I have neither the space nor the tools.

Hope this helps and that it is not TMI.

Let me tell you the facts of sub life and design. You can't just take a box and put a driver in it. That is why there are no sub boxes.

What you do is pick out likely drivers, that have reliable Thiel/Small specifications. Then you model the driver to get the optimal cabinet, and see if the driver needs to be ported or sealed for optimal loading.

Now a sealed sub needs equalization and a boost of 12db/octave below F3 and then high passing at the free air resonance of the driver. A ported sub needs to have the driver in the correct size of box, with very little wiggle room. It needs a port, or ports, of the correct dimensions. The ports also need to be correctly sized so that there is no air turbulence creating 'chuffing'. You can see all that in the design I posted. If you just pick a driver and throw it in any old box, it will not work, and it will NOT be a sub.

So your plan is dead on arrival at the outset. So you either build it, or have a cabinet shop build it, or you buy a working properly designed sub, with an amp that also has any required equalizations. There are no exceptions. NONE!

 

[j_garcia]

Car subs are often 4 Ohm, not necessarily geared toward home theater gear which is typically 8 Ohm. Car subs are also intended for small volume applications, not a large rooms. I have taken drivers and adapted them into a box for use in the home, but if given a choice, stick with one made for a house.

14'x26' is good. You'll likely want a 12" for that size of space. Approximate budget? Maybe you can buy a kit and either get a box built or get a "flat pack" box for it?

 

[T Moon]

Budget? Why was it advised to seek a peak power handling of 500W? What amp particularly, is it 360W at 8 ohm or 4 ohm? What extension (lowest frequency response) are you thinking about?

Just took a look at an ebay search, was some pro-style Behringer and JBL subs....as was said commercial home audio passive subs are kinda rare (most seem to be in-wall models). Willing to DIY it?

RE: why 500W?
I don't know the answer to that.

RE: 360W
This Amp is Rotel RB890. I am unable say at what resistance. Interesting that in this conversation with the repair guy he did ask me if this amp was stable a 2 ohm.

I just left a query with Rotel (rotel.com). Hopefully, they get back to me.

RE: DIY / ebay

Have not done this sort of work (wood working and/or electonics for decades. I have neither the space nor the tools at this point.

I have had no luck with ebay previously but the current search turned up NHT SW2P and Yamaha SW-P3600 at <$100.

Sorry to have to ask but that's why I came here. What am I looking for (in terms) of specs?

Amazon shows JBL Pro stuff at mose bleed levels.

RE: Budget

$200 or less (?)

RE: What extension

Blue sky? 40Hz - 900 Hz

I have a soft spot in my hearing between 800 - 900 and I never was able to get it from multiway primary speakers. This system will most likely have an EQ between its Amp and the sub.

If I find a prospective model new than I should be able to look for somebody that wants to sell something that they were tired of looking at.

RE: Behringer

I don't know this name. What sort of specs does it have and/or why do you bring it up?

Thanks for your response.

 

[T Moon]

Let me tell you the facts of sub life and design. You can't just take a box and put a driver in it. That is why there are no sub boxes.

What you do is pick out likely drivers, that have reliable Thiel/Small specifications. Then you model the driver to get the optimal cabinet, and see if the driver needs to be ported or sealed for optimal loading.

Now a sealed sub needs equalization and a boost of 12db/octave below F3 and then high passing at the free air resonance of the driver. A ported sub needs to have the driver in the correct size of box, with very little wiggle room. It needs a port, or ports, of the correct dimensions. The ports also need to be correctly sized so that there is no air turbulence creating 'chuffing'. You can see all that in the design I posted. If you just pick a driver and throw it in any old box, it will not work, and it will NOT be a sub.

So your plan is dead on arrival at the outset. So you either build it, or have a cabinet shop build it, or you buy a working properly designed sub, with an amp that also has any required equalizations. There are no exceptions. NONE!

Please correct as necessary.

RE: DYI vs buy

I think I was clear. It's buy it from my perspective.

The question I am trying to place is what model(s) fit 'acceptable' for the application I am trying to describe?

I am unclear if you are saying that:

1. I am likely not going to buy another amp. However, if you can reccomend an amp with integrated EQ, I will look for it on the market.

2. Obviously, I am leaning toward a discreet EQ but I'm not sufficiently conversant with EQ specs. Is it your opinion that such an EQ is not sufficient for the described application?

 

[T Moon]

Car subs are often 4 Ohm, not necessarily geared toward home theater gear which is typically 8 Ohm. Car subs are also intended for small volume applications, not a large rooms. I have taken drivers and adapted them into a box for use in the home, but if given a choice, stick with one made for a house.

14'x26' is good. You'll likely want a 12" for that size of space. Approximate budget? Maybe you can buy a kit and either get a box built or get a "flat pack" box for it?

RE: DIY / having something built

No on DIY. Unlikely on get it built. I don't have the knowledge and probably the budget on getting it built. The 'flat pack' box seems to skirt the issues involving electronics and drivers. And, I would have to see a good number of opinions favoring a subwoofer 'kit'.

I'm entirely unconvinced that I would be able to find someone who wants to sell me their DYI 2nd hand sub that is going to line up the stars and present itself to me.

RE: 14' x 26'

You are making me think that the seating and speakers should be placed on the 14' walls. If so, I had not considered that. At this point, that would probably mean that the speakers would be on the glass wall and the seating would be ~ 14' from the center point of the speakers facing the glass wall. That would maybe mean that the speaks would be ~10' feet apart and that they would have ~24' before their broacasts would see a wall.

Some smaller considerations might have to include:
- what are the physical placements of the furniture behind the seating such as the dining table and chairs.
- the speakers would not be placed in or near (relatively) the corners of the glass wall.
- certainly (?) the speakers would not have the table and chairs between then on/near the glass wall.
- if previous point above, then the table is ~4' from the glass wall and 3' from the long wall with the the speakers woud be ~ 8' from the glass wall and the seating could be pushed to the short wall facing the glass wall.

Sorry, babbling, I will have to draw this up and see what it looks like.

I had a physics teacher whose background was acoustics (especially music acoustics). The majoriy of the class was mechanical engineers and they went up in arms and presented a complaint to the dean with me refusing to help them or sign their complaint.

They won (from the perspective of the class material) and I never got the acoustics stuff (which was the attraction to me).

Any case, what are some of the points I need to consider as it applies to population of the objects and their affect on the audio waves?

 

[lovinthehd]

RE: why 500W?
I don't know the answer to that.

RE: 360W
This Amp is Rotel RB890. I am unable say at what resistance. Interesting that in this conversation with the repair guy he did ask me if this amp was stable a 2 ohm.

I just left a query with Rotel (rotel.com). Hopefully, they get back to me.

RE: DIY / ebay

Have not done this sort of work (wood working and/or electonics for decades. I have neither the space nor the tools at this point.

I have had no luck with ebay previously but the current search turned up NHT SW2P and Yamaha SW-P3600 at <$100.

Sorry to have to ask but that's why I came here. What am I looking for (in terms) of specs?

Amazon shows JBL Pro stuff at mose bleed levels.

RE: Budget

$200 or less (?)

RE: What extension

Blue sky? 40Hz - 900 Hz

I have a soft spot in my hearing between 800 - 900 and I never was able to get it from multiway primary speakers. This system will most likely have an EQ between its Amp and the sub.

If I find a prospective model new than I should be able to look for somebody that wants to sell something that they were tired of looking at.

RE: Behringer

I don't know this name. What sort of specs does it have and/or why do you bring it up?

Thanks for your response.

That's a very low budget. Even DIY with free labor and little finishing, that's a low budget.

40hz for lower extension (and assuming that would be an f3 rather than f6 or f10) is fairly high for a home theater sub, for pro type applications or just music playback, could be sufficient. 900hz from a sub would be unusual, usual limits/cutoffs would be more like 200hz. What gear is the rest of the system?

The RB890 in bridged mode looks to be 360w at 8 ohm per it's spec. Most subwoofers are more likely 4 ohm, and bridging an amp for lower impedance is limited, as it stresses the amp more.

You might check your local craigslist, facebook marketplace etc for used home subs. What about the two you found? Behringer is a budget brand of pro-type gear. This one came up