[Bass&Trouble]

Originally Posted by clipto333

an expensive port that is. But why go for a PR when its just like using a port? ports are quite cheap.

Im sure there is some thing that cannot be achieved with using ports, otherwise why would anyone use a PR? There must be something. if you or anyone knows, i would appreciate a more detailed explanation. :-)

1. Its very easy to build. Just like building a sealed box. No tension that the carpenter buggered up the dimensions by a few mm on the slot etc. (I know its human to err, and Bhagwans are immune but still. ) As simple as building a sealed box to spec and popping in two drivers. (Dimensions of the enclosure for SQ purposes is provided by GZ)

2. Box tuning can be changed very easily, i.e. by adding additional mass.

3. Not prone to any of the drawbacks of a port, viz. chuffing/ turbulence.

4. His girlfriends think he's got two Ground Zero Uranium subwoofers. Major brownie points.

Originally Posted by BHAGWAN

Bhagwan Desai & Passive Radiators !!!

hahahahaha .. Bhagwan Desai.....hahahahahaha

[clipto333]

Originally Posted by BHAGWAN

I like my moniker a lot;

So if every one could call me 'Bhagwan' it would be nice.

Thanks,

Godji sounds too passe'
So avoid it.

I appreciate the efforts.

i missed this post of your. sorry for that. :-)

Originally Posted by BHAGWAN

Sir, I shall try and address the issue of PR's first;
My understanding and exposure in the matter is rather limited & hence if I make some mistake - please do forgive me & more important - correct me;
Guru's i.e.

Yes, Ports are much much cheaper to make. Cost is down. However they have problems. The biggest being 'tourbulance' & 'port noise'
All woofers have a specified volume enclosure that they play best in. The port size [diameter] length & material will have a great effect on the final result.

While with a PR, one onlt needs to get the volume of the box 'correct' rest is taken care of automatically. That is the biggest USP of a PR.

I will write about the drwbacks of PR's in a different post.

Besides, PR are very very difficult to make [correct i.e.]
The mass and surface area of the PR should be the same as that active woofer. The PR does not have a magent or coil etc.

p.s. Bhagwan is a name. I have a close friend whoose name is Bhagwan Desai. It has nothing to do with God. That is my moniker on many other forums too. Just like a name like Shiv or Ram or what ever have you.....

Bhagwan,

Thanks for the detailed explanation.

So PR's are much easier to get right as compared to Ports. So if im installing a PR, would i need the volume of a sealed enclosure? if thats the case, then i think it is a great solution if space is at a premium as a sealed enclosure is mostly smaller than a ported enclosure for the same sub.

I hope im clear enough.

Re your moniker, i really didn't mean to offend you and i apologize if i did. I would call you Bhagwan in future. :-)

cheers

Originally Posted by Bass&Trouble

1. Its very easy to build. Just like building a sealed box. No tension that the carpenter buggered up the dimensions by a few mm on the slot etc. (I know its human to err, and Bhagwans are immune but still. ) As simple as building a sealed box to spec and popping in two drivers. (Dimensions of the enclosure for SQ purposes is provided by GZ)

2. Box tuning can be changed very easily, i.e. by adding additional mass.

3. Not prone to any of the drawbacks of a port, viz. chuffing/ turbulence.

4. His girlfriends think he's got two Ground Zero Uranium subwoofers. Major brownie points.



hahahahaha .. Bhagwan Desai.....hahahahahaha

Thanks B&T. I think your point 4 is a good reason to get a PR lol.

I have a question. can one use a sub as a PR? If you remove the Motor assembly i.e. ? The surface area will be same but will the mass remain the same? If we just remove the magnet (and not the VC), then i think the mass will remain the same. what do you say?

cheers
clip

[Bass&Trouble]

Originally Posted by clipto333

So PR's are much easier to get right as compared to Ports. So if im installing a PR, would i need the volume of a sealed enclosure? if thats the case, then i think it is a great solution if space is at a premium as a sealed enclosure is mostly smaller than a ported enclosure for the same sub.

No, that would be too good to be true. The volume requirement is the same with the exception of the adjustment to be made of port displacement v/s passive radiator's air displacement.

Originally Posted by clipto333

I have a question. can one use a sub as a PR? If you remove the Motor assembly i.e. ? The surface area will be same but will the mass remain the same? If we just remove the magnet (and not the VC), then i think the mass will remain the same. what do you say?

You can, but you would need to have a woofer with a moving mass equal to that desired for the tuning frequency. But when Bhagwan has given a motor and voice coil, it is better to use it actively methinks.

[BHAGWAN]

Originally Posted by clipto333

[A]

So PR's are much easier to get right as compared to Ports. So if im installing a PR, would i need the volume of a sealed enclosure? if thats the case, then i think it is a great solution if space is at a premium as a sealed enclosure is mostly smaller than a ported enclosure for the same sub.

[b]

I have a question. can one use a sub as a PR? If you remove the Motor assembly i.e. ? The surface area will be same but will the mass remain the same? If we just remove the magnet (and not the VC), then i think the mass will remain the same. what do you say?

clip

I shall address both the points seperately;

A]
Yes, PR's are easier to get right as compared to ported enclosures.
Kind of Port ? Position of Port ? Material of Port ? Angle of Port ? Diameter of Port ? Depth of Port ? These are for circular ports, then there are Slot Ports & Band Pass Enclosured etc. etc.
However, all woofers have different TS Parameters [Thiel Small]. This Navin will explain......
Hence, woofers that go into sealed enclosures cannot be put into ported enclosures & ported woofers [i.e. woofers that are designed to go into ported enclosures] cannot be put into sealed boxes.

B]
No. This is not possible.
PR's and their corresponding woofers have to be designed together. Simple. One cannot cut from here and paste there........

[DerAlte]

Originally Posted by BHAGWAN

B]
No. This is not possible.
PR's and their corresponding woofers have to be designed together. Simple. One cannot cut from here and paste there........

Possible, but a waste of money (unless someone is fortunate enough to get a couple of subs for free). Even in that case, isobarik is the way to go - avoids the PR tuning overhead.

The PR need not be the same size and composition as the main sub. Navin has the linky for the article (patented method, Linkwitz I think) which describes the how-to. The moving mass needs to be tuned to the designed frequency.

You are right to the extent that most commonly available PRs are replicas of the same sub, minus the magnet, with a mass carrier in place of the VC and dust cap.

[low_bass_makker]

Also with the motor the linear travel of the diaphragm is increased. Like in the case of GZ case the sub is having 25mm Xmax and the PR is having of 50 mm.

[BHAGWAN]

The Picture !!

The left is a sub & the right is the PR

[navin]

Originally Posted by BHAGWAN

...However, all woofers have different TS Parameters [Thiel Small]. This Navin will explain.........PR's and their corresponding woofers have to be designed together. Simple. One cannot cut from here and paste there........

Originally Posted by DerAlte

...The PR need not be the same size and composition as the main sub. Navin has the linky for the article (patented method, Linkwitz I think) which describes the how-to. The moving mass needs to be tuned to the designed frequency....

Firstly I am NOT a Guru. I said it before.

A passive radiator system may be made up of one or more PRs. As long as the Cms and Mms of the combination of PRs is tuned well it will work. Speaker manufacturers prefer to use ports as they are chepaer to make and install. PRs however (like B&T said) allow a user to tune the bass response of a speaker. Tuning however is something that has it limits. I've seen systems where the PR flaps around (I suspect that B&T has seen similar systems too) in an uncontrolled fashion.

One can tune a port to and some unconventional tunings can be used (Google for EBS tuning of ported speakers and you will find atleast 1 such tuning). EBS (Exteneded Bass Shelf) like all things in life, has it's advantages (usually a few more hertz in freq response) and disadvantages (usually a poorer impulse response).

In short bass tuning whether by port or PR is the manufacturer's perogative. You either like it, lump it , or DIY.

[clipto333]

Originally Posted by DerAlte

Possible, but a waste of money (unless someone is fortunate enough to get a couple of subs for free). Even in that case, isobarik is the way to go - avoids the PR tuning overhead.

The PR need not be the same size and composition as the main sub. Navin has the linky for the article (patented method, Linkwitz I think) which describes the how-to. The moving mass needs to be tuned to the designed frequency.

You are right to the extent that most commonly available PRs are replicas of the same sub, minus the magnet, with a mass carrier in place of the VC and dust cap.

what if one has two subs and one of them is blown? i will try it whenever i have the opportunity. Not that i want my sub to conk :-)

cheers
clip

[navin]

Originally Posted by clipto333

what if one has two subs and one of them is blown? i will try it whenever i have the opportunity. Not that i want my sub to conk :-)

clip, dont worry about it. try it. you can tune the PR using silly putty or Blu tac. make 5gm ballz of blu tac and add these to the dust cap. my guess is 15gm or so should work.

[clipto333]

Originally Posted by navin

clip, dont worry about it. try it. you can tune the PR using silly putty or Blu tac. make 5gm ballz of blu tac and add these to the dust cap. my guess is 15gm or so should work.

This is exactly what i wanted to hear. :-) i will do it once a find a blown sub.

Navinji, have you used a PR? have you ever compared a PR with a ported enclosure for the same sub? im really curious as to what the difference would be.

[gunbir]

PR brings back memories...

I did a PR based sub when I was in class 11th. I did little to no math but it did work well. Of course, back then just the fact that it worked was enough for me. Whether it actually sounded good, or had any benefit was not important at that time nor do I remember.

[navin]

Originally Posted by clipto333

Navinji, have you used a PR? have you ever compared a PR with a ported enclosure for the same sub?

I built a few PR subs even one that used 3 PRs (one active driver). The drivers (woofer and PRs) I used were not great drivers (Madisound home brand). I did compare this sub to a subs using a sloted port (not round) and the sloted port souned tighter. But I believe it was just bad tuning on my part. I was expecting too much from the PR based sub.

After that my experiments with PR were in the 90s. We (a friend and I) tinkered with a few PRs that were constructed so that mass tuning could be done easily. The PRs were rear mounted. These designs were far more successful (they used better drivers built in Denmark) then my friend fell on hard times and further development stopped (I heard his accountant ran away with his wife, after bleeding his company or something insane thing like that).

B&T might know this 6' 3" "friend" (from Essen). :-)

Talking about the above Essen based experiments, Clip, one advantage we found was that when trying to couple the port to a wall (or floor) there was some ammount of non-linearities. flared ports I assume might have solved this. a PR however could be coupled to a wall/floor with fewer side effects. I dont know if these supposed effects are psychological or real as we did not ABX this.

[DerAlte]

Originally Posted by navin

... (I heard his accountant ran away with his wife, after bleeding his company or something insane thing like that).
B&T might know this 6' 3" "friend" (from Essen). :-)
...

Lesson learnt: "Concentrate on your wife instead of the woofer. Also, learn accounting so that wool is not pulled over your eyes".

Reminds us of @b&t and his unfinished DIY woofer.

Essen as in Essen Deinki?

[navin]

Originally Posted by DerAlte

Essen as in Essen Deinki?

no. this essen.
Startseite Essen.de
Essen - Wikipedia, the free encyclopedia