My Dual 12" Sub Project

[jinjuku]

Alright, I needed something to keep me busy so I decided on sub project:

Dual Dayton Quatro 12". This will be a down firing, rear ported setup.

Behringer A500 Amp. This amp is servo based, so it will be a servo subwoofer. I figured a $199, 26 lbs servo based amp was a better deal than a $240 17 lbs plate amp. If i need to switch the phase, I can flip the speaker wires. The built in X-over of the receiver makes the one on the plate amp a moot point.

It is a ported design with a tuning of 25Hz. This calls for 2 ports of 4" diameter and 16.83 inches in length. The ones from PE are 17 inches. It's all good.

I am running 2 terminal cups and will feed each side of the amp via RCA cinch connector off of a y cable from the subwoofer out. So I am not wiring the speakers in series. Basically running two mono-amps.

5 lbs of acousti-stuff, they say about 1/2 lb per cubic foot. The cabinet is just shy of 6.

A set of speaker spikes in chrome will tie it to the floor.

The entire component cost is $530 and that includes the $38 router jig. So less than $500 for a dual 12". Tack on 1" MDF and laminate cost...

 

[Sheep]

This probably goes in the DIY section.... no wait, it does.

Congrats on building your very own PB-12SND/2!

Any pictures as of yet?

SheepStar

 

[jinjuku]

This probably goes in the DIY section.... no wait, it does.

Congrats on building your very own PB-12SND/2!

Any pictures as of yet?

SheepStar

I pretty much view it as a toss up as to which forum. So it would be ok if I built it, finished it and then posted something here about it? Is this the finished subwoofer forum?

DIY section could be for DIY AMP, Sound Baffles, Speakers, Subs etc... I am just doing a sub so I decided to dump it in the subwoofer forum. What's the matter with that?

I will post pic's as I progress.

 

[annunaki]

Both subs are going into one enclosure?

Make sure to level match the amp outputs to the subs if they have independent amp channels.

I do not believe the stuffing is necessary if the enclosure is the proper size. It sounds like it is. You can line a couple walls with the stuffing but it is not necessary to fill the enclosure with it.

 

[jinjuku]

Both subs are going into one enclosure?

Make sure to level match the amp outputs to the subs if they have independent amp channels.

I do not believe the stuffing is necessary if the enclosure is the proper size. It sounds like it is. You can line a couple walls with the stuffing but it is not necessary to fill the enclosure with it.

Any particular approach to level matching? I could wire the woofers in series and monoblock the entire setup. That would be simpler.

The enclosure dimensions come from WinISD and are 24X37X15 inches. Port length for a 25Hz tuning is actually 15 1/3 inches and 22Hz is almost 19 inches. If I just use the 17" PE flared port, tunning will be slightly below 24Hz. I don't know how much or how little to stuff the box. I just know I want to kill any wonky internal reflections.

On reading the PE section on the sub:

However, since most home theatre subwoofers are crossed at 80 Hz or below, the reference level is reduced drastically whereby the F3 will typically be below 30 Hz even for the 10" model. The tuning frequencies will typically be in the mid-to-high 20's, which will minimize cone excursion at critical home theatre frequencies.

I take that to mean that a tuning of around 25Hz will keep the drivers from getting out of control. Do I need a dedicated sub crossover like I have seen on the PE website? I thought the vented enclosure will have a natural roll off. What am missing by not going w/ a plate amp that has x-over, 12db roll-off and all that jazz. I thought it doesn't come into play if you use the Receivers X-over and turn the X-over on the plate amp all the way up. Am I missing anything?

 

[annunaki]

What they are saying is that you should use a subsonic high pass filter. It is usually a high order (3rd or 4th) slope at 5hz or so below the tuning frequency. This helps to ensure the enclosure does not "unload". If a woofer plays below the tuning frequency the air inside the enclosure stops acting like a spring and the woofer is essentially moving to its mechanical limits. The power handling of the driver will be lowered by as much as two thirds and mechanical damage may occur easily. With the LFE present on some modern movies, a subsonic/infrasonic filter is recommended with nearly all vented enclosures.

As for the amplifier and level matching, this can be done easily with a digital multi meter. Run a 40hz sine wave through the amplifier and measure the output voltage (AC) of the amplifier (while hooked to one of the subs) at a low level. Note the level on the A500 for that channel. Note the volume level on the receiver. Note the voltage on the DMM. Adjust the other channel of the A500 to the same level and check the voltage with the DMM. If they are the same, your project will be very simple. If not, you will need to adjust the channel up or down to ensure the drivers are operating in unison.

 

[jinjuku]

Ok, I have since changed the tuning of the enclosure to 18Hz to deal with the possibility of loud/sudden sub-18Hz transients coming through and allowing the woofer to unload. I understand that with the lower tuning of the enclosure that I am sacrificing output. That is ok by me since this sub is overkill with two 12" subs, I am not that concerned.

I am going to look at either a Behringer or Aelesis crossover to see what kind of functions I can perform. Either one can be had for less than $100.

I take it the lower tuning will also decrease the drivers ability to stay as accurate vs a higher tuning. That is with a lower tuning, a driver can tend to flail around a bit more, correct? The lower the tuning the looser the 'spring'?

Thanks, you have been a great help.

 

[WmAx]

I am going to look at either a Behringer or Aelesis crossover to see what kind of functions I can perform. Either one can be had for less than $100.

From past inspection of a CX3400 $130 3 way Behringer, I expect it will be better made as compared to virtually any competitor of the same product at even 2x the price. It used high quality parts / switches / potentiometers that I would expect in much more expensive equipment only. But it did have a slight turn on/off thump.

I take it the lower tuning will also decrease the drivers ability to stay as accurate vs a higher tuning. That is with a lower tuning, a driver can tend to flail around a bit more, correct? The lower the tuning the looser the 'spring'?

Thanks, you have been a great help.

Within the narrow set of variables you are discussing here, technically, the accuracy of the driver will increase as you lower the tuning frequency as you specify in a practical application. As you lower the frequency of the cut off slope, you push the inherent phase shift/group delay associated with that slope down in frequency as well, moving it farther from the majority of the common LF bandwidth in music, thus improving the impulse response(transient response) in the practical band. As for the audibility of this; that is another matter. I speak only of physical/measurable behaviour.

-Chris

 

[jinjuku]

Thanks Chris. I understand. The reason for a crossover was hopefully the ability to introduce a Subsonic Highpass Filter so the sub wasn't trying to play material that could be significantly loud below the boxes tuning and damaging the drivers. I have read enough anecdotal evidence that I should be ok without since the box is tuned to 18Hz.

 

[jinjuku]

I can only find 3/4 inch mdf board. I guess it will work. I may double up for the speaker baffle and add a little extra bracing.

 

[annunaki]

Ok, I have since changed the tuning of the enclosure to 18Hz to deal with the possibility of loud/sudden sub-18Hz transients coming through and allowing the woofer to unload. I understand that with the lower tuning of the enclosure that I am sacrificing output. That is ok by me since this sub is overkill with two 12" subs, I am not that concerned.

I am going to look at either a Behringer or Aelesis crossover to see what kind of functions I can perform. Either one can be had for less than $100.

I take it the lower tuning will also decrease the drivers ability to stay as accurate vs a higher tuning. That is with a lower tuning, a driver can tend to flail around a bit more, correct? The lower the tuning the looser the 'spring'?

Thanks, you have been a great help.

Not really correct. The lower the tuning the deeper the response. The lower tuning frequency should actually aid in accuracy as Chis has indicated. Some woofers may drop off a bit in response towards the top end (if they are ot designed well or do not align well in ported applications. A really well designed subwoofer will have even response from it's tuning frequency up to the crossover point.

What does the response curve look like now that you have lowered the tuning frequency? Always ensure that the response curve stays flat and linear when making changes to the enclosure design.

Accuracy, typically, is inherent in the woofer itself. The more linear the motor and suspension the more true to the source the sub will be (lower distortion, less additives to the sound from the woofer). Coupling the woofer to proper well designed enclosure and avoiding peaks and dips in response will be your responsibility.

Proper enclosure design can make a mediocre sub sound quite good. Poor enclosure design can make even the best woofers sound terrible. Couple the proper enclosure with the best woofer, the proper enclosure with a mediocre woofer and the differences in the woofer's themselves will become apparent. The accuracy diffences should make themselves known.

 

[jinjuku]

What does the response curve look like now that you have lowered the tuning frequency? Always ensure that the response curve stays flat and linear when making changes to the enclosure design.

Am I looking at a 1 watt, 1 meter to measure the response curve?

The drop is 12 db from 80Hz to 20 Hz. I know enough about sub building to be dangerous. One heck of an education that I am getting

Repsonse Curve Pic

 

[annunaki]

Are you sure that is a vented enclosure? Have you also entered in the low pass crossover at 80hz in the tabs across the top?

If that is the vented reponse you may want to rethink your driver choice. You can also input the correct power amount you will be running in the "input" tab of the project.

There are many better drivers out there in terms of reponse. It depends on your budget though.

Have you purchased these subs yet?

 

[jinjuku]

The driver was a budget consideration in view of the comments I have found about it's ability to be a good driver.

I am using WinISD beta 0.44. The tabs are Driver/Box/Vents/Plot/Project.

I see no facility for input of cross over value.

 

[annunaki]

The driver was a budget consideration in view of the comments I have found about it's ability to be a good driver.

I am using WinISD beta 0.44. The tabs are Driver/Box/Vents/Plot/Project.

I see no facility for input of cross over value.

Check into plot. It may have a value for input power.

 

[jinjuku]

It does have a setting for input power and measuring distance. I cant adjust the High/Low Hz setting in options though to limit the graph. It's ghosted out... Driving me nuts.

 

[annunaki]

Perhaps go back to the WinIsd site and download the Pro Alpha version. That is what I use and it works very well.

 

[jinjuku]

I have WinISD Pro Alpha loaded. But the spec sheet for the Quatro doesn't provide enough information. The driver editor won't let me save w/o some more values accounted for.

 

[annunaki]

I have WinISD Pro Alpha loaded. But the spec sheet for the Quatro doesn't provide enough information. The driver editor won't let me save w/o some more values accounted for.

Are you sure you did not put too many values in? If the auto calculate feature is turned on, you only need about 3-4 parameters in each section, sometimes less. I have never had it let me not save because of too few parameters. Perhaps you may need to turn on the "auto calculate unknowns" feature at the bottom.

 

[jinjuku]

Are you sure you did not put too many values in? If the auto calculate feature is turned on, you only need about 3-4 parameters in each section, sometimes less. I have never had it let me not save because of too few parameters. Perhaps you may need to turn on the "auto calculate unknowns" feature at the bottom.

I did read the help

Important note for 0.50a7 and above:
The driver editor won't accept erraneous entries anymore. Your data must be perfect (i.e. not over-defined by entering "too much" parameters), for you to be able to save it. If you try to enter too many of them, editor will display an error dialog when you try to save the data.

Ok, so how many is 'too many of them'? I think they require the speaker dimensions also. This is starting to piss me off actually

What really gets me is there doesn't seem to be a single PE driver in the database. Come on, they aren't exactly a no name...