Subwoofer project using a 12" Peerless 835017 (or better)

[shmb]

Hi all,

I'm looking to possibly take on a subwoofer project. Nothing special, just a standard vented design.

I'm currently looking seriously at the Peerless 835017 12" driver.

There are 2 different datasheet links below on this driver which vary a little in T/S parameters for some reason.
http://www.tymphany.com/files/XXLS-P835017%20%20Rev%201_0.pdf
http://www.parts-express.com/pdf/264-1114s.pdf

Basically, I would like to build a sub that will go down flat to the low 20's (-3db point) and hopefully without any eq.

Using my old fashioned (possibly inaccurate) T/S formulas from 20 years ago, it seems that an enclosure of 115L tuned to 22Hz will theoretically achieve that, however these days with PC modeling, I would appreciate it if someone would be able to possibly recommend the correct enclosure and tuning and do a more accurate simulation to find out whether I can achieve my goal with this driver or if not, perhaps recommend me a different driver?

A large enclosure size is not much of an issue, ....however I'll eventually have to draw the line somewhere.

Any help appreciated.

 

[Inductor]

Hi shmb,
1st datasheet -2010
2nd datasheet - 2009 (preliminar?)
Very good driver for BR or TL enclosures.
BRs from 63-165 L.
ideal PEERLESS XXLS-P835017, VB = 107.0 L, FB = 18.1 Hz (F-3 dB/26 Hz)
PEERLESS XXLS-P835017, VB = 107.0 L, FB = 21.4 Hz (F-3 dB/23 Hz)
PEERLESS XXLS-P835017, VB = 125.0 L, FB = 21.0 Hz (F-3 dB/22 Hz)
PEERLESS XXLS-P835017, VB = 150.0 L, FB = 20/21.0 Hz (F-3 dB/20 Hz)

 

[shmb]

Ok, so seems like I wasn't too far off then.


A few more questions:

I must say 150L with an Fb: 21Hz, f3: 20Hz sounds impressive and tempting.
But can you go too large? (from a sound quality perspective only)

You also say a 107L with Fb: 18Hz, F3: 26Hz is ideal?
Why is this considered ideal?

On top of that, I guess whats most confusing is that some recommended enclosures for this woofer are around 75L vented.
Obviously F3 will then suffer even more but is there a 'sound quality' reason to use a 75L over these larger up to 150L enclosures? Or is it purely for practicality reasons?

Thanks.

 

[Inductor]

Obviously F3 will then suffer even more but is there a 'sound quality' reason to use a 75L over these larger up to 150L enclosures? Or is it purely for practicality reasons?

Thanks.

Yes, if you do the alignments (simulations) you know what I mean.
Let's just say that the ideal is the ideal alignment (not talking about bad subs or artificially equalized subs with DSPs and LTs). It means is not so abrupt with less low-end but the link room-gain/speaker is better achieved for "standard room dimensions". So I would never go 150L or 75L unless you put it inside your car.
A professional high-end monitor might have F3 close to 30-35Hz for your info.

 

[shmb]

Yes, if you do the alignments (simulations) you know what I mean.
Let's just say that the ideal is the ideal alignment (not talking about bad subs or artificially equalized subs with DSPs and LTs). It means is not so abrupt with less low-end but the link room-gain/speaker is better achieved for "standard room dimensions". So I would never go 150L or 75L unless you put it inside your car.
A professional high-end monitor might have F3 close to 30-35Hz for your info.

Ok thanks, I'm really gonna have to learn how to do this computer modeling.

Any simple effective design software I can download?

Thanks.

 

[publius]

win isd pro

LinearTeam

i believe that driver or similar is used in an svs 12" ported sub, nsd12 or something like that. also in the genelec quad driver subwoofer that costs something like $10k.

3.5 cubic feet tuned to 21hz has a nice smooth rolloff that would work well.

best,

 

[shmb]

Great thanks, seems to work a treat.

 

[Inductor]

Great. Post results and impressions.

 

[shmb]

Ok, so assuming I'll go 107-110L, I have a few more questions. Actually a lot.

I'll be using MDF, .....what sort of thickness do I need? I'd rather go overboard than the opposite.
Was thinking maybe 2x18mm MDF sheets glued together (36mm) with shelf bracing in 2 places. (ie approx every 25cm.) Maybe a cross brace from top to bottom too. Approximate external size will be 40cm x 55cm x 85cm (yes it is big)

A pic below is attached, ........after I did this rough drawing however, I realised the 300mm woofer has to mount somwhere so I guess the bracing will have to be spread differently to what's there. No top to bottom cross brace in the pic either.

Can the shelf braces be just 18mm thick? (not 36mm) Is that considered ok?
How many round holes in the shelf brace will do? Diameter of hole? Don't want to make it too weak but don't want to lose too much volume either.

Is it bad to mount the driver in the centre of the baffle? I'm thinking for a subwoofer it doesn't matter as they only work below 80Hz or so?

Regarding Ports and tuning, whats a tried and true method of reducing port noise? Obviously flared on both ends is a start, but is there an ideal diameter or is it just the bigger the better? Or is there maybe an ideal position on the baffle for it to be? I'm hoping to put it near the bottom with driver in the middle. I read somewhere it has something to do with air speed and velocity? Is it predictable at all?


Finally, (although I can worry about this later) where can I find a decent sub amp (or 2) with a continuously variable phase adjustment. Most just have a switch.

Once again any help on these matters will be appreciated.

BTW: I'm now actually thinking of building 2 of these. It should be enough for a 4.5m x 5.7m room.

 

[Inductor]

Question #6 (paragraph):
Ideal diameter first is related to the tunning frequency and is such that doesn't give air speed noise at the power/SPL you gonna use.
There is a maximum of air speed usually used for the ports that is theoretically acceptable. From there you have your min. diameter or cross area and then calculate the length. (I can help you with that, if you give me the tunning frequency) look in WinIsd.
mh-audio.nl - Home
http://www.diyaudio.com/forums/subwoofers/75899-minimum-port-diameter.html

 

[shmb]

Ok, thanks, so it looks like a single 4.5" diameter or more is required.

Looking at the simulations, the ideal tuning frequency would probably be anywhere between 19-22Hz??

Parts Express sells 4" and 6" dia dual flared ports, but 6" port lengths will be impractical. I would need an elbow. (if I can fine one for that size)
Is this an issue with regards to port noise etc?

Any ideas of who else sell these sorts of things?

Thanks.

 

[Inductor]

You can resource a PVC tube (construction, other) for loudspeaker ports locally. If using the 4" from PE you can use/test it's max. length of 17".
Precision Port 4" Flared Port Tube Kit 268-352
4" flared speaker ports - DIY Audio & Electronics - StereoNET Australia
Commercial Port Flares

 

[Inductor]

You can make also a rectangular flared port with the same wood you are using in one of the sides of the box.
If the port is not directed to you (to your face), you will have less noise problems, only at max SPL.
Only use bends if not enough space for straight ports.
RAM Designs: Step by Step Ported Subwoofer Box Design - YouTube

 

[Shadydave]

long round flared ports

I bought an extra PE 4" port kit and used the couplers along with the tube cut in half to make a pair of 24" long ports
It sounded a little boomy, or maybe had allot of group delay.
And there are L/D limits that supposedly should be followed and the quoted audiophile (Length / Diameter) limit that I have heard is something like 2 or 2-1/2 meaning that a 4" ID port should only be 10" long.
I do not know how much there is to this rule of thumb, but I think my 24" port was too long.
I finally took it out, sealed the boxes, made them into the main woofers and replaced them with proper subs with flared shelf ports.

Dave

 

[shmb]

Ok interesting, about the diameter vs length limit.
Maybe someone else could explain if that is or isn't the case???

I think I'd still prefer to stick with the round 'flared on both ends' ports.

Anyway I'm still investigating for now.

Thanks.

 

[chris661]

Ok interesting, about the diameter vs length limit.
Maybe someone else could explain if that is or isn't the case???

I think I'd still prefer to stick with the round 'flared on both ends' ports.

Anyway I'm still investigating for now.

Thanks.

The 2.5 rule is probably to do with port resonances: simulate a ported box in Hornresp and note the additional peaks and dips >100Hz.

If a port gets too long, you start to get resonances within the pass band of the subwoofer, which can prove interesting to integrate with other speakers

Chris

 

[Shadydave]

Flare shape

One problem with commercial flared ports is they have a spherical radius on their ends.
While this looks good, at higher flows there will be flow separation causing the port to flow less than the nominal (4") diameter.
It would be better to have a flare shaped more like a funnel. with straight sides rather than sides that exponentially curve more and more.
The spherical radius port does work better at lower SPL's, it is when you crank it up and get higher velocities that the flow separation and hence turbulence in the port exit occurs.

Dave

 

[bjorno]

Hi,FYI:
Here is another late suggestion for a Sub using the Peerless-835017 Driver:

b

 

[shmb]

That may be a little big.

Anyway, the size/volume is now finalised, I'll end up with about 118-119L with everything fitted except port(s)
The volume of those still need to be subtracted so it depends on what size ports I use.

Looking at all the compromises, it seems I should go for the 4" dual flared port. Precision Port 4" Flared Port Tube Kit 268-352
It would be approx 40cm long. That will reduce the effective volume to about 114-115L.

Now on WinISD from my simulations, it seems that at 175 watts (the drivers RMS rating), port air velocity is about 30-31m/s at around 20Hz with the 4" port. (worst case at 175w)

Is this reasonable and acceptable?

This calculator from earlier in this thread: mh-audio.nl - Home tells me at least 11.5 cm diameter is required.

So will the 4" flared be enough in practice?

Thanks.

 

[Inductor]

This calculator from earlier in this thread: mh-audio.nl - Home tells me at least 11.5 cm diameter is required.

So will the 4" flared be enough in practice?

Thanks.

You must be an engineer.
Read my post, you can't have max. power at Xmax. This was the suject of discussion in other threads (read SI 18"). You blow the woofer before you get max elongation...

Peerless 835017 XXLS 12"
Nominal Power RMS 120W
http://www.tymphany.com/files/XXLS-P835017 Rev 1_0.pdf
2 examples for this project:
a) 115L/21Hz (38.84cm = 15 19⁄64in)
To go to max elongation you would need double the power more close to 300W@3Ohms.
b) For VB = 110.0 L, FB = 20.5 Hz, length (43.34cm = 17 1⁄16in).
You would need Pmin. 308.0 W@3.1 Ohms@20.5 Hz for max elongation (12.3mm/V=31.13 V) so don't worry (be happy) about max power output before you will blow the sub.
note. dB for max. SPL is unachievable by all standards so you will have a relative power off less than half or about that at a percentage of time you have max. volume in your system.