Where do I start?

[twowheeled]

Hi everyone, this is my first post on diyaudio. A few years ago I dabbled in DIY, built a pair of book shelf speakers as well as a very crude cabinet for some subwoofer drivers I was given for free. I'm interested in building a real subwoofer this time but I don't know where to start. This forum contains a huge amount of information but it all seems very disorganized, where would I brush up on recommended reading as well as some of the popular choices out there people are building? What would be great is if I could find some sort of listing outlining cost/complexity and performance of the popular DIY subwoofers.

In any case, here are some general goals I have set.
-use for home theater and stereo listening
-powering an 18x30 foot room enclosed by 3 walls
-cabinet size can be reasonably large but would perfer a box design rather than tubular
-performance down to 20hz, I will also be adding bass shakers to the couch for low freq's.
-build cost $500-800 drivers and amp

 

[nunayafb]

Yes it is disorganized, it is a forum. I don't recommend starting here, get a book, Vance Dickasons loudspeaker cookbook for example, and learn all of the fundamentals, learn the glossary of words used in audio (there are actually websites dedicated to this) and then come back with specific questions and search for the answers first. I can almost guarantee any questions you might have have been asked and answered at least 3 times on this site alone.

-use for home theater and stereo listening
Same requirement as far as I am concerned, although the HT sub needs to go down ~20Hz whereas the music sub rarely needs to, and f3 of 30-40Hz should do for most music. But my opinion, if you are willing to sacrifice space, get a big woofer and get music quality bass that extends down to where you want it to.

-powering an 18x30 foot room enclosed by 3 walls
Could you elaborate on this, is the missing fourth wall behind you or behind the speakers, what are the dimensions of this space? (dining room/kitchen/halfwall?)

-cabinet size can be reasonably large but would perfer a box design rather than tubular
I haven't built it yet but I've modeled a subwoofer using two Dayton 18" Classics in an isobaric configuration, see pics and winisd plots.

-performance down to 20hz, I will also be adding bass shakers to the couch for low freq's.
If you want the smaller box, I would recommend the 2.5ft^3, with either a LT (Linkwitz Transform) or an Eq, I have the Behringer DEQ2496 and a 15" IB woofer in a U-frame dipole and the bass rolloff is quite similar to the 2.5 ft^3 model, it eq's +- 0.5dB on 1/3 octave resolution.


-build cost $500-800 drivers and amp
Dayton 18" x2 ~$200
An amp like the Behringer EP1500 or 2500 $300- $350 respectively (never owned one but plan on buying them based on user reviews)
Behringer DEQ2496 $300

All available from parts express

 

[nunayafb]

The CAD model:

 

[twowheeled]

Yes it is disorganized, it is a forum. I don't recommend starting here, get a book, Vance Dickasons loudspeaker cookbook for example, and learn all of the fundamentals, learn the glossary of words used in audio (there are actually websites dedicated to this) and then come back with specific questions and search for the answers first. I can almost guarantee any questions you might have have been asked and answered at least 3 times on this site alone.

-use for home theater and stereo listening
Same requirement as far as I am concerned, although the HT sub needs to go down ~20Hz whereas the music sub rarely needs to, and f3 of 30-40Hz should do for most music. But my opinion, if you are willing to sacrifice space, get a big woofer and get music quality bass that extends down to where you want it to.

-powering an 18x30 foot room enclosed by 3 walls
Could you elaborate on this, is the missing fourth wall behind you or behind the speakers, what are the dimensions of this space? (dining room/kitchen/halfwall?)

-cabinet size can be reasonably large but would perfer a box design rather than tubular
I haven't built it yet but I've modeled a subwoofer using two Dayton 18" Classics in an isobaric configuration, see pics and winisd plots.

-performance down to 20hz, I will also be adding bass shakers to the couch for low freq's.
If you want the smaller box, I would recommend the 2.5ft^3, with either a LT (Linkwitz Transform) or an Eq, I have the Behringer DEQ2496 and a 15" IB woofer in a U-frame dipole and the bass rolloff is quite similar to the 2.5 ft^3 model, it eq's +- 0.5dB on 1/3 octave resolution.


-build cost $500-800 drivers and amp
Dayton 18" x2 ~$200
An amp like the Behringer EP1500 or 2500 $300- $350 respectively (never owned one but plan on buying them based on user reviews)
Behringer DEQ2496 $300

All available from parts express

I have read up on loudspeaker design and do have a book on it. However I am not looking to reinvent the wheel or so to speak, I would perfer to copy a well known and proven design rather than build it from the ground up. What looks good on paper doesn't always sound good when built, which is why I don't want to take my chances selecting a driver and designing my own enclosure for it.

The missing wall is a side wall to the right of the listener, it opens up to the rest of the the basement. Opening would be about 18 length by 10 foot ceiling. Box size is a non-issue I don't mind having a large cabinet.

Is there no sort of listing for catagorized common builds? Sorted by driver size, enclosure design or cost?

 

[2100]

Since you are not aiming to reinvent the wheel (eg try horns, pro audio drivers etc) and home theatre is the equation, my best solution to offer is try the SVS PB12+/2 and PB12+. Very competitively priced that you don't really save much by DIY. Premium veneers too. It has loads of SPL for home theatre, and since you are trying out DIY, the multiple tuning options by vent plugging would please your fingers.

http://www.svsound.com/products-sub-box-plus1.cfm

http://www.svsound.com/products-sub-box-plus2.cfm

I guess you are in Canada, so shipping is low.

 

[owdi]

What are your woodworking skills? If you are just looking for a good value, it's hard to beat the kits at Parts Express.

Dayton T1503 15" Titanic Mk III Subwoofer Kit
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=300-764

The parametric eq should let you tune the low end to taste. With a 15" woofer and 20mm of one way throw, you don't need a ported box.

Don't know if they ship to Canada though.

Dan

 

[twowheeled]

What are your woodworking skills? If you are just looking for a good value, it's hard to beat the kits at Parts Express.

Dayton T1503 15" Titanic Mk III Subwoofer Kit
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=300-764

The parametric eq should let you tune the low end to taste. With a 15" woofer and 20mm of one way throw, you don't need a ported box.

Don't know if they ship to Canada though.

Dan

I consider myself pretty good at woodworking, so complexity of the enclosure doesn't really concern me.

 

[simon5]

First you need to know the parts suppliers for subwoofers...

In canada :
http://www.creativesound.ca/

In USA :
http://www.partsexpress.com/
http://www.acoustic-visions.com/
http://www.aespeakers.com/

There are many others but those are my favorites.

Then you need to read this WHOLE website... DIY Subwoofer page :
http://www.diysubwoofers.org/

After that, you'll have alot of knowledge and you will know better what do you want and we will be able to help you better.

Here is some software that can help you design better subwoofers :

WinISD Pro :
http://www.linearteam.dk/default.aspx?pageid=winisdpro

UniBox : (need Microsoft Excel since it's a Excel program)
http://home20.inet.tele.dk/kou/ubmodel.html

HornResp : (primary for bass horns and horns in general but can be used for everything, very powerful)
http://mywebsite.bigpond.com/dmcbean/

SubSim :
http://www.geocities.com/f4ier/newsubsim.htm

My personal recommandation for a first serious subwoofer since you are good at woodworking and you already built one would be a big box with passive radiators since your budget is high enough.

Cost would be : (from creativesound.ca in $CDN)
SDX 15" subwoofer driver for 239$
LT1300 ED 1300 watts plate amplifier for 389$
2x PR1821 18" passive radiator at 139$ each so 278$
Total : 925$ (Yeah I exaggerate, like always!)

Then a 4' x 8' sheet of 3/4" baltic birch plywood ~75$
Glue ~10$
Wires ~5$
Paint ~20$
Weatherstripping double sided tape
Etc.

Anyway, that's my personal opinion, but that subwoofer would be awesome.

Good luck !

 

[simon5]

I also saw that you don't want to reinvent the wheel...

Then you could use whatever Creative Sound Solutions, or Acoustic Elegance, or PartsExpress, or Acoustic Visions recommends for the drivers they are selling.

Some of them will even give you plans. My first subwoofer was made following a Adire Audio plan, it was very well done. I guess you could use it with another driver since they don't sell subwoofers anymore but it's their plans so maybe there would be a copyright issue.

 

[owdi]

simon5 - nothing personal, but I really don't like your recommendation to use passive radiators. You could get superior performance by dropping the PRs, buying two drivers, and going sealed. Arrange the drivers in a push-pull configuration, keep the box the same size, and use the bass boost built into the amp to fill in the low end.

This gets you lower distortion, group delay and price. You loose some efficiency around the tuning frequency, but gain it everywhere else. Overall power handling goes up too.

Dan

 

[simon5]

Hi owdi

It's nice to have opposite opinions

I'm against bass boost to fill low end, you lose amplifier headroom.

Also you run much more power than needed to achieve the same SPL at the same frequency with a ported and/or passive box so I'm not sure that you will achieve lower distortion when playing loud, especially when you run into the bass boosted frequencies.

I agree with you about the group delay, sealed is better. But then, if you tune under 20 Hz, group delay isn't that problematic.

I agree with you also on the push-pull configuration, lower distortion on small level signals, but when you push all the power needed to achieve high SPL, I'm not sure that you will achieve lower distortion since push-pull is power hungry if we talk about the same thing.

Lower price, I agree with you also. But again, he has alot of money to spend, it seems. I tend to suggest a project to use all the money or to exaggerate.

I agree that you get high power handling also, but do you get higher SPL ? Do you get lower distortion at high SPLs ?

Your suggestion is very good, to me it would be an excellent sounding subwoofer for moderate volume listening, with very low distortion.

I think my idea is better for high volume listening, with low distortion.

What do you think ?

 

[ScottG]

Re: Re: Where do I start?

Box size is a non-issue I don't mind having a large cabinet.

THAT really should have gotten the attention of others.

Consider an "IB" design (aka infinite baffle).

The cheapest driver is the Dayton IB at parts express.

Then there is the new IB driver from aespeakers.

Finally, Rythmik audio should have an IB servo driver solution soon.

 

[owdi]

Hi owdi

It's nice to have opposite opinions

I'm against bass boost to fill low end, you lose amplifier headroom.

Also you run much more power than needed to achieve the same SPL at the same frequency with a ported and/or passive box so I'm not sure that you will achieve lower distortion when playing loud, especially when you run into the bass boosted frequencies.

I agree with you about the group delay, sealed is better. But then, if you tune under 20 Hz, group delay isn't that problematic.

I agree with you also on the push-pull configuration, lower distortion on small level signals, but when you push all the power needed to achieve high SPL, I'm not sure that you will achieve lower distortion since push-pull is power hungry if we talk about the same thing.

Lower price, I agree with you also. But again, he has alot of money to spend, it seems. I tend to suggest a project to use all the money or to exaggerate.

I agree that you get high power handling also, but do you get higher SPL ? Do you get lower distortion at high SPLs ?

Your suggestion is very good, to me it would be an excellent sounding subwoofer for moderate volume listening, with very low distortion.

I think my idea is better for high volume listening, with low distortion.

What do you think ?

Even with bass boost, I don't think the dual sealed subwoofer would require a larger amp than the PR subwoofer.

This is a chart comparing a vented*** vs. dual sealed alignment. 4 cu ft. using the Dayton 12" HF, @ 1 watt.

[IMGDEAD]http://www.michnicki.com/diy/ventedvsdualsealed.jpg[/IMGDEAD]

The vented alignment is more efficient between 14hz and 40hz, while the sealed alignment is more efficient above 40hz.

An interesting thing to ask is what happens when you EQ these two subwoofers so they have equivalent FR (using that bass boost). Below 40hz the vented sub will have the advantage, with less power required for a given SPL, and lower excursion. Above 40hz the dual sealed setup will have the advantage.

Things get murky when you feed the sub music instead of test tones. Music, even synthetic, is filled with harmonics. These can be just as loud as the fundamental. At 30hz the vented alignment has the advantage, but when you factor in the 60hz and 90hz harmonic the sealed could be more efficient. I haven't taken the measurements or done the math, but my guess is power requirements between these two subwoofers would be pretty even when it comes to playing music.

If the power requirements are equivalent, then you should base your decision on other factors, such as distortion and price. The dual sealed push-pull wins in both categories, which is why I recommend it over a PR. It should also be easier to construct, and easier to tune.

***I used vented because I'm lazy. It's easier than modeling a PR and results are very close, with PR being slightly less efficient

Dan

 

[simon5]

Nice discussion, you have a point with harmonics. I guess it depends on the kind of music we listen to, then.

I did your same experiment with WinISD Pro alpha.

I entered 2nd order peaking highpass 6 dB bass boost filter centered at 20 Hz. Now your design is equal with vented from 30 Hz and under. Over 30 Hz your design is louder from a 1 W imput.

Problem is excursion. Your design will go in overexcursion at 20 Hz when the amplifier is outputting 125 watts because of the bass boost, the real power usage at 20 Hz will be near 310 W according to apparent amplifier power load in VA in WinISD.

Vented enclosure OTOH will take 330 W before going in overexcursion at 30 Hz and under 18 Hz.

We now have very similar power handling and significantly higher output for the vented enclosure, except if the signal doesn't contain low frequency, then sealed wins.

Maybe we should use a better filter like Linkwitz transform or param EQ. Since we get lower SPL from sealed, maybe we would get lower distortion from vented at same SPL.

I agree with you on price like always, my idea is expensive. I also agree about ease of construction and ease of tuning.

Here's the results with similar "apparent" power imput 310 W for sealed and 330 W for vented before overexcursion.

 

[owdi]

I think we pretty much agree on everything, but have different tastes

I don't think an LT is required for the sealed enclosure. With room gain, about 4db boost at 20hz should flatten things out and satisfy the OPs requirements.

While you're already modeling things in WinISD, try a dual vented Dayton RS 12" HF in 4 cu ft, with two round 4" x 36" ports. If you could fit the ports, and align the drivers push-pull, could be an awesome sub.

Dan

 

[judtoff]

I would recomend passive radiators as well. A tapped horn would be great too. Oh and would nt only 1 18" radiator be needed

 

[simon5]

owdi yeah your idea ain't bad, but to better match room gain, I would prefer 8 cu.ft with those 2 ports but 28 inches long.

Would be easier to fit also! We also get a low end bonus...

That's because IMHO room gain is more like 3 dB/octave in a "typical" (if we could say that...) drywall room. I tend to design subwoofers around that room gain curve.

You seem to be well versed into push pull subwoofers, can you show one of your creations ? I would like to see one, thanks !

 

[Andersonix]

Re: Re: Re: Where do I start?

Consider an "IB" design (aka infinite baffle).

The cheapest driver is the Dayton IB at parts express.

Then there is the new IB driver from aespeakers.

Finally, Rythmik audio should have an IB servo driver solution soon.

It's strange how many boxes people try building before they come around to just cutting a hole in a wall or ceiling and sticking in an IB woofer (or 4). IB should always be the first thought before resorting to boxes...

What do people think of Parts Express Dayton HPSA1000-R 1000W Rackmount Subwoofer Amplifier (pn 300-810) for $400? It has a proper adjustable phase control knob, parametric EQ, and plenty of power.

 

[planet10]

I don't know why a push-pull woofer of any sort would take more power.

With a lot of the more linear woofers today push-pull doesn't give you all that much.

Some more seni-random thots....

When i am looking at doing a woofer i prefer to make a push-posh woofer as it takes a lot of the box out of the coloration equation.

I'm not a big fan of BRs, boxes with PRs are like BRs with an extra resonance to deal with.

If you are going to go sealed, the box should be big enuff to be low Q (0.5-0.58)... tie it in with room gain and it will go low. A little judicial boost if needed isn't a bad thing. A really big box turns into an IB ... if you have a large space adjacent to your listening room, i'd consider that the way to go.

My real preference is for quarter-wave or aperiodic boxes. A QW that goes low will almost rival an IB in terms of size... i have designs for a CSS SD12 BIB (see attached) & a TL, and some data for a monster or 2 with a pair of SDX15s

To my mind the best way to move alot of air is to use a big woofer, but you have to trade that off against the smaller woofers better top end, which help with integration to the mains.

At the moment i am working with the SDX7 -- only good to 25 Hz or so thou.

dave

 

[SoundRight]

Little box vs big box!

Power is cheap. A small cabinet, tuned to a very low frequency will provide 12dB/octave roll off, low group delay when compared to a larger sealed box...and reduced cone excursion to very low frequencies around 20Hz. The benefits of a small box when compared with the problems of a large box with inherent rigidity issues and greater distances between panels totally outweigh needing a bigger amp imo, particularly with Class D readily available?