First DIY: Peerless Push-Pull - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 20 Old 05-16-2009, 12:19 AM - Thread Starter
Member
 
Dark Regent's Avatar
 
Join Date: Mar 2009
Location: New Mexico
Posts: 53
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
This is a Peerless Push-Pull (Non-Isobaric) Project.

This is my first post on this forum and my first DIY speaker project. I have been reading these forums for a while but now I finally have a reason to post here. I currently own a Sony SA-WX700 dual 10" push-pull subwoofer and I've been looking at the M&K push-pull's for a while now but have no desire to spend thousands of dollars on one speaker, nor do I have the money to do so, so here I am. Still being in college, funds are limited. I have been impressed with my little Sony for the last 5 or so years, nice potent little speaker. I really like the sound that the push-pull design produce so I think I'd like to go for a bigger better version, so to speak.
I am fairly certain that I have settled on the push-pull (non-isobaric) design. It has served me well so far and seems to work well for M&K. The idea of good response for music and high output for movies looks promising. I figure I can always find a 15" and try making a ported enclosure sometime in the future. I'd be interested in seeing how a push-pull and a ported sub work together in the same application.

I watch a lot of movies but this subwoofer will also be used with a lot of music. I am planning on slowly upgrading my little home theater setup. I recently purchased a used Denon AVR-2808CI off of ebay and next I plan on up grading my speakers. I figured I'd start with the subwoofer as it's the easiest before getting into attempting to build tweeters. I believe I have the design chosen but I do have some questions.

My design idea:
I started by testing the design in BassBox Pro and once I figured out what volume I needed I used Unigraphics NX3 to model the enclosure.






I am planning on using 1/2" MDF on top of 3/4" MDF for the top, bottom, walls, and lower speaker brace. The other braces are modeled as 1/2" MDF. The dimensions are 16"x20"x33.6" (WxDxH). I'm planning to use T-nuts and bolts where I can and I'm looking at picking two of these up:
http://www.deepsurplus.com/Speaker-P...-218-Thickness

I have purchased two Peerless 830952 12" subwoofers on sale from Madisound ($159 each). My original plan was to use the Dayton HPSA1000 1000w amplifier connected to the two 4ohm speakers wired in series (reversed phase on the second one). However, I'm afraid that running the speakers with 500w (250w each) would damage them as they are only rated for 175w RMS, no idea what the peak wattage is rated at.

I only found one person using a similar setup driving two of these Peerless 830952 with the Dayton HPSA1000-R. However, he is having clipping issues now. I noticed he is operating under the assumption that the subwoofers are rated for 350w, not sure if he's assuming that for peak power handling but the only rating I've found actually issued from Tymphany in their catalog (through Madisound) is 175w.
http://www.madisound.com/catalog/PDF/830952.pdf

Post about clipping:
http://www.avsforum.com/avs-vb/showthread.php?t=1098736

The speakers max out their excursion when being powered with 500w. I'm not sure what the rules are when it comes to discussing xmax vs xmech, so I figured better to be safe than sorry. Also, I would like to be able to have the option to get down to 20hz if possible, even if it's not at max output.



That being the case I'm leaning towards the Oaudio 500w (325w into 8 ohm) amplifier. The modeling only indicates a 2dB drop consistently along the frequency line. I figure the easiest thing for me to do is just get a plate amp with the parametric EQ built in. The Reckhorn A-402 amplifier looked promising (400w into 2 ohm) but I don't feel like waiting 4 to 10 weeks for it to get here, nor did I find any reviews for it anywhere. I have no idea how to setup pro-audio amplifiers and EQ devices so I figure I'll save that for later.

On to the questions:
1) Am I correct in thinking that I don't need sound damping material for this application?
2) What can EQing (maybe some gain) do for me, if anything, in the low frequencies?
3) Is it a good enclosure design and is it strong enough to hold the speakers?

All thoughts, suggestions, and opinions are welcome.
Dark Regent is offline  
Sponsored Links
Advertisement
 
post #2 of 20 Old 05-17-2009, 01:52 AM
Advanced Member
 
Craigslue's Avatar
 
Join Date: Oct 2002
Location: Kansas
Posts: 738
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Go to the Tymphany site and look under some of the other XXLS 12" models and they say

100h RMS noise test IEC - 175W
Long term max power IEC 18.3 - 350W

I'm guessing that they are all the same since they seem to use the same motor.
As far as noise test and IEC 18.3 ?
Craigslue is offline  
post #3 of 20 Old 05-18-2009, 07:27 AM
AVS Special Member
 
michael hurd's Avatar
 
Join Date: Nov 2007
Location: 49th parallel
Posts: 2,119
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Liked: 27
On to the questions:
1) Am I correct in thinking that I don't need sound damping material for this application?
2) What can EQing (maybe some gain) do for me, if anything, in the low frequencies?
3) Is it a good enclosure design and is it strong enough to hold the speakers


1) A moderate amount of polyfill, foam, fiberglass or rockwool should be applied inside the enclosure. It does two things: provide attenuation of noises from the spider or pole vent on the rear of the driver being reflected and re-emitted through the driver cone and it also makes the 'effective' volume larger, this will lower your tuning point some, 1-2hz.

2) Eq can give you a bit more output above tuning, but be warned you shouldn't exceed xmax by much in your simulations with the boost you want to try.

3) Personally I would oppose the drivers horizontally and go for as much port area as you can get in the box.

*4) You will need a high pass filter built in to the amp to keep from breaking the driver with signals below the tuning point.

"You take the blue pill - the story ends, you wake up in your bed and believe whatever you want to believe. You take the red pill - you stay in Wonderland and I show you how deep the rabbit-hole goes."
michael hurd is offline  
post #4 of 20 Old 05-18-2009, 07:39 AM
AVS Special Member
 
mayhem13's Avatar
 
Join Date: Jan 2008
Location: nj
Posts: 3,951
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Liked: 13
Quote:
Originally Posted by michael hurd View Post

3) Personally I would oppose the drivers horizontally and go for as much port area as you can get in the box.

??? What port are you referring to?

Mike, i believe the Push-pull is a sealed design.
mayhem13 is offline  
post #5 of 20 Old 05-18-2009, 07:48 AM
AVS Addicted Member
 
penngray's Avatar
 
Join Date: Feb 2006
Location: Florida
Posts: 26,779
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 30
Quote:
Originally Posted by mayhem13 View Post

??? What port are you referring to?

Mike, i believe the Push-pull is a sealed design.

I see a port in the pics above

It is not "open-minded" to reject knowledge - Bob Lee
penngray is offline  
post #6 of 20 Old 05-18-2009, 07:50 AM
AVS Addicted Member
 
penngray's Avatar
 
Join Date: Feb 2006
Location: Florida
Posts: 26,779
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 30
Quote:


I only found one person using a similar setup driving two of these Peerless 830952 with the Dayton HPSA1000-R. However, he is having clipping issues now

The Dayton 1000W amps have been measured by Chuck in this forum....they measure HORRIBLE @ 20Hz.

I wouldn't use them for serious sub woofer projects.

It is not "open-minded" to reject knowledge - Bob Lee
penngray is offline  
post #7 of 20 Old 05-18-2009, 07:51 AM
AVS Special Member
 
michael hurd's Avatar
 
Join Date: Nov 2007
Location: 49th parallel
Posts: 2,119
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Liked: 27
You will get some high pass filtering off the bottom driver, as well as some radiation resistance from that quasi-hole in the box. I would make it larger than the cone area so you don't end up with some cavity resonances, maybe put some thin foam on one wall.

I just had a brief look at the picture before I posted that.

"You take the blue pill - the story ends, you wake up in your bed and believe whatever you want to believe. You take the red pill - you stay in Wonderland and I show you how deep the rabbit-hole goes."
michael hurd is offline  
post #8 of 20 Old 05-18-2009, 07:55 AM
AVS Special Member
 
mayhem13's Avatar
 
Join Date: Jan 2008
Location: nj
Posts: 3,951
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Liked: 13
Quote:
Originally Posted by penngray View Post

I see a port in the pics above

Not used in the conventional way.....merely a vent so to speak. The push driver could be mounted on the rear,top or front with the back of the driver in free space. MK chose to mount it this way to protect the driver and asthetics.
mayhem13 is offline  
post #9 of 20 Old 05-18-2009, 07:56 AM
AVS Addicted Member
 
penngray's Avatar
 
Join Date: Feb 2006
Location: Florida
Posts: 26,779
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 30
Quote:
Originally Posted by mayhem13 View Post

Not used in the conventional way.....merely a vent so to speak. The push driver could be mounted on the rear,top or front with the back of the driver in free space. MK chose to mount it this way to protect the driver and asthetics.


ah, I see that now...thanks for explaining!

I have 4 B&K 12" drivers from deepsurplus and I wanted to do a push/pull midbass solution myself.

It is not "open-minded" to reject knowledge - Bob Lee
penngray is offline  
post #10 of 20 Old 05-18-2009, 07:59 AM
AVS Special Member
 
mayhem13's Avatar
 
Join Date: Jan 2008
Location: nj
Posts: 3,951
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Liked: 13
Hey Mike, i've tossed around some push-pull designs and the apparent distortion cancellations ( some say even some say odd yet little measurements to prove either point) at the expense of a larger box. Other than a HiFi music setup, do you see any advantages for Deep LF extension? Mounting the two drivers on either side of a small sealed box seems just as effective considering the BL.
mayhem13 is offline  
post #11 of 20 Old 05-18-2009, 09:49 AM
Senior Member
 
tlag's Avatar
 
Join Date: Nov 2006
Posts: 401
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 12
Theoretically, push-pull definitely cancels even-order products. Do it numerically, do it graphically, it's always even that goes poof.

I'll try to describe it like this: unlike what intuition might picture, so-called even-order distortion is asymmetric in the sense that positive-half and negative-half waveforms are different. Like, tall/narrow positive half, and short/wide negative half, or vice-versa. So you take two of these, invert one, add them up, no more asymmetry: you're left with odd-order products, which "sharpen" or "dull" both halves equally. Weird, maybe, but true.

That's the theory. In practice, there are many more factors, and it all depends on the actual drivers and system.

Editorially, would have to say push-pull is not always the way to go, especially given aesthetic/safety concerns. For example, I'd argue that rather than the one-horizontal, one-vertical push-pull, dual-opposed push-push ala Seaton or bossobass would be superior. Far better aesthetics, and practically perfect force cancellation. For sure. Distortion? Well, what are the numbers?
tlag is offline  
post #12 of 20 Old 05-18-2009, 10:42 AM
AVS Special Member
 
Tack's Avatar
 
Join Date: Mar 2004
Location: Valencia, Ca
Posts: 3,412
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 230 Post(s)
Liked: 693
Hes got the "aesthetic/safety concerns" covered pretty well with the "outside" driver....inside. Pretty tough to service if it has a problem though.

Dark Regent, are you going to allow for removal of the enclosed driver?

Id like to hear it. At least its different.
Tack is offline  
post #13 of 20 Old 05-18-2009, 10:47 AM
AVS Special Member
 
mayhem13's Avatar
 
Join Date: Jan 2008
Location: nj
Posts: 3,951
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Liked: 13
Quote:
Originally Posted by tlag View Post

Theoretically, push-pull definitely cancels even-order products.

I'm not arguing with you as i mentioned earlier i believe a back to back driver alignment to be just as effective with a smaller box and higher power handling to boot.....i just found it odd to use theoretically and definitley in the same sentance. I've searched far and wide for definitive measured results that show these 'cancellations' The Isobarik alignment fell flat on it's face when tested i believe the Push Pull would fall the same as these were early designs that worked with the old school of drivers....Today's drivers don't need the pseudo quasi aligments IMO. Back to Back in phase is more than enough.
mayhem13 is offline  
post #14 of 20 Old 05-18-2009, 03:12 PM
Senior Member
 
tlag's Avatar
 
Join Date: Nov 2006
Posts: 401
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 12
Quote:
Originally Posted by mayhem13 View Post

Hey Mike, i've tossed around some push-pull designs and the apparent distortion cancellations ( some say even some say odd yet little measurements to prove either point) at the expense of a larger box.

Theoretically, it's definitely even-order that gets cancelled.

Quote:
Originally Posted by mayhem13 View Post

i just found it odd to use theoretically and definitley in the same sentance.

Just trying to clear up the apparent ambiguity definitively. Theoretically, there is no ambiguity. Theoretically, in push-pull or differential systems, odd-orders add, even-orders annihilate. Definitely. Trying to be precise, not colloquial. Not trying to make anyone's head "literally" explode.
tlag is offline  
post #15 of 20 Old 05-18-2009, 06:44 PM - Thread Starter
Member
 
Dark Regent's Avatar
 
Join Date: Mar 2009
Location: New Mexico
Posts: 53
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Craigslue - That is a good point, for some reason I hadn't thought to look at the other driver specs to look for the max power. Thanks.

michael - Yeah, I should have pointed out that it was indeed a sealed enclosure. As mayhem pointed out it is a "vent", since the second driver is supposed to be mounted with the driver sticking out of the enclosure for this design to work. That being the case do I still need polyfill? I was under the impression that damping was mostly used for the ported and possibly PRed enclosures. According to bassbox this design is best right around 88.5 liters, any increase or decrease in volume increases the tuning point. Adding damping material increases the tuning point even if I reduce the enclosure volume. So far the best results have been right around 88.5 liters with no fill so unless I need it I'd rather not have it, but that's why I'm asking more knowledgeable people. I may put some foam below the bottom driver as you've suggested. As far as the high pass filter, the Oaudio amp has an adjustable subsonic filter and I believe I read that the Dayton amp has a hard wired 18hz filter built in.

tlag - It was hard finding information on the push-pull (non-isobaric) design. I was originally thinking that the drivers in my Sony SA-WX700 were indeed moving in unison and working together. That was until I found a thread on these forums with this picture.


I also found this page which was very helpful in explaining the different types of subwoofer enclosures. Advantages and disadvantages.
http://www.danmarx.org/audioinnovation/theories.html

Quote:


Compound ~ Push/Pull Dual Drivers
Two drivers share an acoustic volume of air within a single enclosure. The best way to take advantage of this alignment is to mount one driver facing outwards with the other driver inverted and facing inwards. The drivers are then wired so that they are electrically out of phase while remaining mechanically still in phase with one another. Odd ordered harmonics are cancelled out by using this approach according to Vance Dickason. According to M&K who specialize in push/pull subwoofers claim that this approach cancels out even ordered harmonics. So take your pick. Either way, harmonic distortion is reduced in that any anomalies or variations in the two driver's spider, cone or suspension characteristics are canceled out by the other driver's inversely proportional anomalies and variations. The sound is as accurate and pure as it can possibly be with each driver "correcting" the other driver. Of course many times two drivers will share the same acoustic volume of air while maintaining the more traditional look of having both drivers fire forward into the listening environment. Though this does not have the same harmonic cancellation effect, all other characteristics between the two alignments is identical. Box volume must be twice that of a single driver. This can be easily modeled by taking the Vas of a single driver and multiplying it by two. The system has an increased efficiency of 3dB over a single driver. Power handling for the system is twice that of single driver. Frequency response is the same for a single driver in an enclosure excaly half the size.

The way I understand it is that it all has to do with the fact that subwoofers moving inward (towards the basket) behave differently than they do when firing outward, which I believe is what you're saying, causing the differences in the waveforms. The second driver firing outward into the enclosure makes up for the weakness of the first driver moving inwards. Correct me if I'm wrong.

penngray - I think the Dayton is good between 20-200Hz, still not the best though. It doesn't look like I need the extra power anyway.
http://www.avsforum.com/avs-vb/showt...9#post13714349
Currently though I'm leaning towards the Oaudio running at 325w which will insure that my speakers don't bottom out (according to the model in bassbox pro), looks to have better rolloffs, and the fact that it's over $100 cheaper doesn't hurt. I was also thinking that it would be fun to get some of those 12" M&K subs off of deepsurplus and experiment. Sadly I don't have the money right now. I would like to see how a push-pull sealed enclosure compares to just a dual driver sealed enclosure.

Tack - I'm currently trying to figure out how I should mount the bottom driver in case something goes wrong. I may mount it on the bottom of that lower brace (bottom of the sealed part of the enclosure) and make the bottom (base) of the subwoofer removable. Still working on that. As you pointed out though it is cool cause you can still see the workings of the second sub and at the same time protect it. I was thinking of something similar looking to the Blue Sky Sub 212 as seen here:
http://www.abluesky.com/user/images/news/hi-res/108.jpg

I have tried different arrangements with these drivers and enclosures in bassbox. So far the push-pull seems to work well, especially within my size constraints. I'm trying to keep the bass around 16" wide and 20" deep, depth can be bigger. According to Bassbox, using Oaudio 325w the driver should never bottom out, no matter how low the frequency goes, where when using the Dayton 500w the driver reaches Xmax at about 28hz and would have to be adjusted with fill which would increase the tuning point. If I went the 500w route it'd probably end up being 67 liters with typical fill with an F3 around 45hz instead of the 41hz I'm looking at with the 88 liter enclosure. I like my current Sony push-pull subwoofer and I'd like to keep the size down. I modeled a good ported enclosure but it was 194 liters or 2 97 liter enclosures tuned with an F3 around 25hz with minimal fill. I started this project with push-pull in mind, basically making my own M&K sub, and I'm trying to stick to that. I figure I'll wait til I can afford a better subwoofer (probably with a bigger Xmax, maybe a Maelstrom-X) and build a ported sub (or PRed), but that's a ways off.

Thank you all for your comments and suggestions.
Dark Regent is offline  
post #16 of 20 Old 05-18-2009, 08:06 PM
AVS Addicted Member
 
penngray's Avatar
 
Join Date: Feb 2006
Location: Florida
Posts: 26,779
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 30
Quote:


penngray - I think the Dayton is good between 20-200Hz, still not the best though

You didnt read it well enough, it only did 580W @ 4 ohms, it should be a 1000W @ 4 ohm amp. Also it has a SSF @ 18Hz so if you want lower then 20Hz, this isnt the amp for you.

Of course 8 ohms performance, f3 @ 40Hz.....maybe its a fine amp for your application

It is not "open-minded" to reject knowledge - Bob Lee
penngray is offline  
post #17 of 20 Old 05-18-2009, 08:10 PM
AVS Special Member
 
Erich H's Avatar
 
Join Date: Dec 2007
Location: Cincinnati OH
Posts: 5,352
Mentioned: 2 Post(s)
Tagged: 1 Thread(s)
Quoted: 283 Post(s)
Liked: 580
Doesn't Deepsurplus now sell the push/pull empty enclosures for around $125 each?


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


Twelve 10" NHT subwoofer build.
Cloning of a NHT VR-3.
2 ACI 15" subwoofers.

Erich H is offline  
post #18 of 20 Old 05-18-2009, 08:13 PM
AVS Addicted Member
 
penngray's Avatar
 
Join Date: Feb 2006
Location: Florida
Posts: 26,779
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 30
Quote:
Originally Posted by Erich H View Post

Doesn't Deepsurplus now sell the push/pull empty enclosures for around $125 each?

Yep, I might be return some enclosures to get the push/pull boxes.

It is not "open-minded" to reject knowledge - Bob Lee
penngray is offline  
post #19 of 20 Old 05-18-2009, 08:25 PM - Thread Starter
Member
 
Dark Regent's Avatar
 
Join Date: Mar 2009
Location: New Mexico
Posts: 53
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by penngray View Post

You didnt read it well enough, it only did 580W @ 4 ohms, it should be a 1000W @ 4 ohm amp. Also it has a SSF @ 18Hz so if you want lower then 20Hz, this isnt the amp for you.

Of course 8 ohms performance, f3 @ 40Hz.....maybe its a fine amp for your application

Nah, I saw the lack luster performance in the 4ohms department and Dayton's response saying they'd do their own tests and never reporting back. However, it did ok with the 8 ohm load between 20 and 200hz which is probably all I would need. I saw the 18hz SSF and mentioned it in my previous post. According to the models I tried I'm still hitting 100dB in the 20hz range, maybe more with room gain (small room), so I figure I'll let the sub run as low as it'll go. I'm not sure what should be considered useful volume, 80dB+ ?

Thanks for the input.
Dark Regent is offline  
post #20 of 20 Old 05-18-2009, 10:21 PM
Senior Member
 
tlag's Avatar
 
Join Date: Nov 2006
Posts: 401
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 12
Quote:
Originally Posted by Dark Regent View Post

tlag - It was hard finding information on the push-pull (non-isobaric) design. I was originally thinking that the drivers in my Sony SA-WX700 were indeed moving in unison and working together. That was until I found a thread on these forums with this picture.


I also found this page which was very helpful in explaining the different types of subwoofer enclosures. Advantages and disadvantages.
http://www.danmarx.org/audioinnovation/theories.html

The way I understand it is that it all has to do with the fact that subwoofers moving inward (towards the basket) behave differently than they do when firing outward, which I believe is what you're saying, causing the differences in the waveforms. The second driver firing outward into the enclosure makes up for the weakness of the first driver moving inwards. Correct me if I'm wrong.

If the Dickason quote is accurate, its content is wrong. M&K as quoted is accurate.

Your restatement is good. Each driver's outstroke adds with the other driver's instroke, and vice versa, so the compound outstroke looks just like the compound instroke. Problem is, the air in the box doesn't act that way, and still has nonlinearity related to the compliance difference between having both drivers in the box vs. both drivers out of box, causing second-order distortion. People argue about the air compliance nonlinearity, but it has to be there. It might well be complementary to some nonlinearity in a single driver's suspension, causing partial distortion cancellation, but then push-pull would get rid of that happy situation. If it existed.

However, that's just the even-order stuff. Odd-order problems caused by symmetric limiting such as BL falloff or suspension limits are not touched by push-pull. This is a case where intuition can mislead. Asymmetries cause even-order distortions, and symmetric factors cause odd-order.

Again, it's the particular numbers that really matter in all this...
tlag is offline  
Reply DIY Speakers and Subs

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off