Push Pull Subwoofer Build?

[Primare Knob]

Hi,

 

I am looking into building two subwoofers for HT use, and I am thinking about the following parts.

4 x (2x2) Dayton RSS390HO-4   https://www.parts-express.com/dayton-audio-rss390ho-4-15-reference-ho-subwoofer-4-ohm--295-469

1x Behringer EP4000 Amplifier https://djcity.com.au/product/behringer-ep4000-power-amp/

 

The reason for thinking about a push pull configuration is that I like the box to stay small. That is also the thinking about using 2x15" drivers instead of using an 18" driver.

The other thing that I would like to have is a fast subwoofer (what ever that might mean) that can compliment my ESL speakers and can go down to 20Hz and produce a clean and undistorted output.

I am not necessarily looking for max output, but something that can produce 100-105dB of SPL and make it sound easy.

 

If I use the the recommended sealed box volume (+ volume 2nd driver) would that be OK ?

This woofer has an F3 of 50Hz in a sealed box, does that mean that it might not be the right driver for me, even if I use two of them?

[Nada]

Hard to give useful info without knowing your needs and background.

 

What ESL do you have?

Why do you want to go down to 20Hz?

What do you want to cross over to the ESL at?

What crossover will you use.

[Primare Knob]

Hard to give useful info without knowing your needs and background.
 
What ESL do you have?
Why do you want to go down to 20Hz?
What do you want to cross over to the ESL at?
What crossover will you use.

Fair points.

Due to the position of my Martin Logan's Montis I have to cross over at 100Hz, as they produces a rather large dip between 70 - 90Hz.

I am using JRiver to create the cross-overs in DSP using parametric Equalizer.

Why 20Hz? Basically because that is how low some movie soundtracks go, sometimes even lower. At the moment my subs physically don't seems to be able to do that and heavily really on room boundaries, and that doesn't make it a very pleasant exercise.

Obviously there are also room nodes at play (35Hz), and for some reason excess energy at 20Hz that I can't explain yet.

[davewantsmoore]

9 hours ago, Primare Knob said:

This woofer has an F3 of 50Hz in a sealed box, does that mean that it might not be the right driver for me

No, it just means you need to factor that into calculating the filter for them, so the resulting response is flat.

 

 

4x 15" woofers would almost certainly be sufficient for your stated SPL.

[joz]

I know I should know this after all these years, but what exactly does it mean by F3@50hz?

[Nada]

1 hour ago, Primare Knob said:

......Due to the position of my Martin Logan's Montis I have to cross over at 100Hz, as they produces a rather large dip between 70 - 90Hz.

 

Cool project.

 

You can model your project online.eg https://speakerboxlite.com

 

That site allow you to model one or dual drivers in different size boxes and set the front dimensions as small as possible for a minimal look.

 

Why did you choose the Dayton 15" HO over the HF? The Dayton Audio RSS390HF-4 has lower inductance.

 

Using front and back drivers in a sealed box and having JR for crossover is just asking for a cardioid set up.  You would need an amp with four channels and use DSP to delay the rear output.  ML are doing that now in the 11a model that replaced your Montis but dual 15" should be much more impressive

[Primare Knob]

 
Cool project.
 
You can model your project online.eg https://speakerboxlite.com
 
That site allow you to model one or dual drivers in different size boxes and set the front dimensions as small as possible for a minimal look.
 
Why did you choose the Dayton 15" HO over the HF? The Dayton Audio RSS390HF-4 has lower inductance.
 
Using front and back drivers in a sealed box and having JR for crossover is just asking for a cardioid set up.  You would need an amp with four channels and use DSP to delay the rear output.  ML are doing that now in the 11a model that replaced your Montis but dual 15" should be much more impressive

I don't know really, why I picked it. I was comparing the 2ohm version which has a lower efficiency.

What is the importance of the lower induction?

The HF has 2mm more excursion and an F3 of 37Hz in a sealed box. You reckon this would be a better choice? I don't really understand why they have 2 versions and what the implementation differences are.

I can google cardioid, and find some heart shape plane/curves. I have seen it before regarding speakers, but I have no idea what this actually means.

[Primare Knob]

I know I should know this after all these years, but what exactly does it mean by F3@50hz?

The natural point where a driver starts to roll off at a -3dB slope. (I think)

[Nada]

3 hours ago, Primare Knob said:

I don't know really, why I picked it. I was comparing the 2ohm version which has a lower efficiency.

What is the importance of the lower induction?

The HF has 2mm more excursion and an F3 of 37Hz in a sealed box. You reckon this would be a better choice? I don't really understand why they have 2 versions and what the implementation differences are.

I can google cardioid, and find some heart shape plane/curves. I have seen it before regarding speakers, but I have no idea what this actually means.

Cardioid can theoretically create more directional bass with less energy bouncing off the back. I dont know if it makes any difference but if the maker of your speakers has replaced your model with one that does cardioid bass, maybe its a good match for ESL's in general and a great match for your ML's?  Cardioid subs need to be really deep to separate the woofers front to back. That makes for a small front panel and low visual impact too as you wanted. 

 

Low impedance woofers seems to go with better woofer extension into the midrange with less distortion in the Dayton 15" range. Acoustic Elegance seem to have the same quality. That may be important for you in future. You might make such a great ESL sub that you decide to run it up to 300Hz and turn of the sub in your Montis. Then the DIY illness could see you making your own ESL panel to fit the subs .....

 

As your looking at making twin dual subs anyway it seems your ideally placed to do that with a cardioid build with Dayton drivers that can match the ML panel. 

 

 

 

 

[Sub Sonic]

9 hours ago, joz said:

I know I should know this after all these years, but what exactly does it mean by F3@50hz?

It’s the frequency at which a speaker is 3db down in response from the nominal “flat” level, as it gradually rolls off on the low end.

 

Cheers,

 

SS

[davewantsmoore]

8 hours ago, Nada said:

Why did you choose the Dayton 15" HO over the HF?

HO has higher force and which lets it drive a smaller enclosure better - the compromise being it won't play as nicely at higher frequencies than the HF....   otherwise they are ~ equal  (power, excursion).

 

8 hours ago, Nada said:

Using front and back drivers in a sealed box and having JR for crossover is just asking for a cardioid set up.  You would need an amp with four channels and use DSP to delay the rear output.

Not sure if I understand.   Cardioid is formed from a dipole summed with a monopole....  how are you suggesting to do it?

 

8 hours ago, Primare Knob said:

What is the importance of the lower induction?

Lower is generally better.    It's not super-particularly relevant for a subwoofer.

 

8 hours ago, Primare Knob said:

The HF has 2mm more excursion

2mm more "linear" excursion.   This is a fairly small difference... and with the amount of cone area you are dedicating to your modest-ish SPL goals, it will not really worry you.

 

8 hours ago, Primare Knob said:

and an F3 of 37Hz in a sealed box

The "F3" of the driver is completely irrelevant, as you will be changing the response of the driver using EQ.

 

8 hours ago, Primare Knob said:

I can google cardioid, and find some heart shape plane/curves. I have seen it before regarding speakers, but I have no idea what this actually means.

As mentioned, you will get a better result from building something "normal and good" (ie. a well documented, well reviewed design) than a less than perfect "fancy thing". 

 

9 hours ago, joz said:

I know I should know this after all these years, but what exactly does it mean by F3@50hz?

It's the frequency where the driver output has reduced by 3dB over it's nominal output.     ie.  it's "3dB down frequency

 

4 hours ago, Nada said:

I dont know if it makes any difference

It does, but below a certain frequency bass in a room no longer has directivity, and so dipoles, and cardioids, etc. etc. start to have little meaning/relevance.

 

https://en.wikipedia.org/wiki/Room_acoustics#Zones

 

4 hours ago, Nada said:

As your looking at making twin dual subs anyway it seems your ideally placed to do that with a cardioid build with Dayton drivers that can match the ML panel. 

A cardioid is extremely difficult to design, and offers no benefit for a subwoofer in a small room.     Maybe if he were to play it up to ~300Hz .... but a well designed "normal box" will run circles around something not designed great 

[Sub Sonic]

4 hours ago, Nada said:

Low impedance woofers seems to go with better woofer extension into the midrange with less distortion in the Dayton 15" range. Acoustic Elegance seem to have the same quality

 

 

Hi Nada,

 

Was it meant to be “low impedance” or “low inductance”?

 

Cheers,

 

SS

[Primare Knob]

Simple would be a good start, as my experience is rather small. I am crafty with timbers, but not with electronics.

 

Besides I need my subwoofers to stay subwoofers, so that I can move them freely for better in room responses. Upgrading the woofers for the Montis would be for the future when I have a bit more experience under my belt. It has potential, as the woofer cabinet isn't very rigid either.

 

Am I correct in saying that a push pull setup, are two driver in sync where one driver has the opposite polarity of the other? They would be wired in parallel and not in series?

 

And to come back to another question, is there such a thing as a fast or slow subwoofer?

 

 

[davewantsmoore]

5 hours ago, Primare Knob said:

And to come back to another question, is there such a thing as a fast or slow subwoofer?

No.

 

 

 

Longer answer....    People get very confused between two things.

 

This subwoofer sounds fast  (or "not fast" ie. slow)

AND

This subwoofer is moving fast  (or has less inertia, or more acceleration... or....)

 

 

These are not the same things....   but what people do is that the assume the second thing is true when they experience the first sensation .... and then they try to match a "cause" to the "effect".

 

Once they assume that "the subwoofer is moving fast" .... they guess that things like lower mass, or higher force, or higher efficiency .... all contribute to a subwoofer "sounding fast".    This seems intuative cos we know that a sports car follows the race track much more easily than a truck, and that is what we want our subwoofer to do (follow the signal better).

 

.... but they have missed the reality that "the subwoofer wasn't able to move nimbly enough", wasn't actually the cause of what they heard in the first place.

 

 

The reality is much much simpler.    If you want your subwoofer to "sound fast", you need to have a flat frequency response, and not problematically high harmonic distortion.      That. is. all.    

 

 

[davewantsmoore]

6 hours ago, Primare Knob said:

Am I correct in saying that a push pull setup, are two driver in sync where one driver has the opposite polarity of the other?

That depends on how the drivers are physically arranged.

6 hours ago, Primare Knob said:

They would be wired in parallel and not in series?

Could be either.

[andyr]

On 26/10/2018 at 11:25 PM, Primare Knob said:

Hi,

 

I am looking into building two subwoofers for HT use, and I am thinking about the following parts.

4 x (2x2) Dayton RSS390HO-4   https://www.parts-express.com/dayton-audio-rss390ho-4-15-reference-ho-subwoofer-4-ohm--295-469

1x Behringer EP4000 Amplifier https://djcity.com.au/product/behringer-ep4000-power-amp/

 

The reason for thinking about a push pull configuration is that I like the box to stay small. That is also the thinking about using 2x15" drivers instead of using an 18" driver.

The other thing that I would like to have is a fast subwoofer (what ever that might mean) that can compliment my ESL speakers and can go down to 20Hz and produce a clean and undistorted output.

I am not necessarily looking for max output, but something that can produce 100-105dB of SPL and make it sound easy.

 

If I use the the recommended sealed box volume (+ volume 2nd driver) would that be OK ?

This woofer has an F3 of 50Hz in a sealed box, does that mean that it might not be the right driver for me, even if I use two of them?

 

You seem to have a similar requirement to what I specified to Paul Spencer - though my subs are for music ... not HT.

 

I wanted 20Hz reproduction (vs. the 35Hz that my Maggies could deliver) to improve my enjoyment of Bach organ music.

 

What Paul supplied is a pair of sealed subs (in ~7 cu ft enclosures) having:

• a 15" Dayton Ultimax driver, and
• an 800w Hypex plate amp.

These do deliver below 20Hz - on an organ LP, I have a couple of test tracks with 16Hz, 12Hz & 8Hz organ tones (the latter produced by a 64' organ pipe! )

 

Before I had the subs ... I couldn't hear any of these tones; with the subs, I can clearly hear the 16Hz tone!

 

Andy

 

[davewantsmoore]

14 hours ago, andyr said:

my subs are for music ... not HT.

What's the difference?   Some music has gunfire .... some action movies have music   

 

The parameters for designing a subwoofer are :

 

How loud

How low

How big

 

I don't really think these lend themselves one way or another to music or HT.   It depends on where you want to focus.

 

The myth that music only goes down to "the lowest note on X instrument"  (eg. bass guitar = ~40Hz) is a fairly prominent myth.....   Although there is a circle of confusion in some genres where people can't reproduce bass, so artists don't include bass, etc.

 

[andyr]

3 hours ago, davewantsmoore said:

What's the difference?   Some music has gunfire .... some action movies have music   

 

IIRC, the OP wrote that he wanted subs for HT.

 

And, yes, I suggest there can be a difference in sub technology.  Subs used for music need to be able to stop quickly - whereas no-one cares if the T-Rex footfall overshoots slightly.

 

Andy

 

[Primare Knob]

Just doing some more reading on the subject.

Putting two woofers in the same cabinet seems to produce a +6dB increase in SPL, but also requires double the output of an amplifier.

Adding a second sub is a bit more random and could add +3dB increase of SPL in general.

Looking at the specs of these subwoofer drivers,they all seem to have a massive impedance over a large portion of the LFE range. Won't that make them very hard to drive, or underpowered when their impedance is really high?

[Primare Knob]

I can't really figure out that if I use 2 opposite drivers wired out of polarity, if I can calculate the box volume based upon a single driver. It seems to be different from an Isobaric setup.

 

 

There seem to be some relatively small differences between a "large" or smaller box, and that a flat graph down to 20HZ needs to come from amplifier output. At least to my untrained and uneducated guess.

 

Edit: Or do all subwoofers rely on the in room response for help?

 

And what the real benefits are of using 2 X 15" drivers vs 1 x 18". Am I overdoing it again as usual?

 

Edit: From memory, if you let your subwoofers do all the sub bass work (bass management) from all your speakers, it would need an extra 6dB of output to manage that.

 

 

 

[Primare Knob]

 
IIRC, the OP wrote that he wanted subs for HT.
 
And, yes, I suggest there can be a difference in sub technology.  Subs used for music need to be able to stop quickly - whereas no-one cares if the T-Rex footfall overshoots slightly.
 
Andy
 

What would the trade off be between the two? If I sacrifice overshoot, what is the gain?

Is this an effect created by building a sub with a low Qtc value?

[Red Spade Audio]

Europower amps are good workhorses but especially on EP4000 the fan is REALLY loud! Even with a fan mod, if willing to void warranty, all fans are still a bit noisy to be in the room. What's the plan? Putting them in a garage and running some cable is a good way to go.

 

If you want a small box, you picked the right version (HO), apparently by accident. These are car audio versions - don't be put off by that. It mostly means they are designed for small boxes.

Quote

And what the real benefits are of using 2 X 15" drivers vs 1 x 18". Am I overdoing it again as usual?

 

 

The advantage with dual driver subs is that you can reduce vibration of the enclosure by having them on opposite faces of the box - one on front, the other on the back. You can use this to either create a really inert box, or simplify bracing.

 

2x15 is likely to deliver more midbass headroom. Much of the action in films lies here. A single 18 is likely with more excursion to deliver more deep bass output and often budget will favour this option.

 

Impedance is also a factor, depending on what you are aiming for. With Europower amps, you want to end up with 4 ohms into each channel. 8 is limiting the power, 2 ohms is pushing your luck.

7 hours ago, davewantsmoore said:

What's the difference?   Some music has gunfire .... some action movies have music 

 

Expectations. I find that for home theatre, people expect more output and are more likely to use it. Films are mixed for large commercial systems with more dynamic range. In a music system, people are often more critical of quality. Partly because a movie engages our attention differently.

[Primare Knob]

 
Cool project.
 
You can model your project online.eg https://speakerboxlite.com
 
That site allow you to model one or dual drivers in different size boxes and set the front dimensions as small as possible for a minimal look.
 
Why did you choose the Dayton 15" HO over the HF? The Dayton Audio RSS390HF-4 has lower inductance.
 
Using front and back drivers in a sealed box and having JR for crossover is just asking for a cardioid set up.  You would need an amp with four channels and use DSP to delay the rear output.  ML are doing that now in the 11a model that replaced your Montis but dual 15" should be much more impressive

What does the Cone displacement (mm) graph mean? Is this related to Xmax?

[almikel]

What does the Cone displacement (mm) graph mean? Is this related to Xmax?

You want the excursion to never exceed Xmax

[VanArn]

Cone displacement is the working area of the cone ( SD ) multiplied by Xmax. It is the volume swept by the cone in one direction.