tunable radiators phorum question?

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kg1961
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tunable radiators phorum question?

Post by kg1961 »

i seen these along time ago but do they really work?
if so why don't other company do this?
http://www.ebay.com/itm/BOSTON-ACOUSTIC ... 2eb74895d7

i remember my dad had a old set of home speaker with them(not the same brand or look) sounded great but?


also do they only work with there speaker or could you do that with other brands?
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stipud
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Re: tunable radiators phorum question?

Post by stipud »

My home theater sub (Peerless XLS) uses a passive radiator. It basically functions just like a port (slightly less efficient, so not QUITE as much gain), but with no chuffing noises. I guess the reason it hasn't taken off as much in car audio is simply because porting is cheaper.
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Re: tunable radiators phorum question?

Post by ttocs »

I have seen passive radiators in home audio but they still take up alot of space, you would be better just adding another woofer imo...
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Re: tunable radiators phorum question?

Post by stipud »

ttocs wrote:I have seen passive radiators in home audio but they still take up alot of space, you would be better just adding another woofer imo...
The box size is almost the same as an equivalent ported enclosure would need to be, so that basically breaks down to "why run one ported when you can run two sealed". Quite a few obvious differences if you look at it that way.
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shawn k
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Re: tunable radiators phorum question?

Post by shawn k »

Ports (with VERY few exceptions) are resonators. Technically they're a "Helmholtz" resonator. A good analogy is to think of blowing across the opening of an empy bottle causing it to create sound. The vents for an enclosure have this same effect causing what it known as "group delay". This is typically 3rd-5th order harmonic distortion. Often people describe a vented enclosure as being "slow" or "doesn't keep up with the midbass". The group delay is what's responsible for these impressions.

So basically, the passive radiator provides you with the benefits of venting (although more costly) but will NOT cause 3rd, 4th, 5th order harmonic distortion from group delay.
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kg1961
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Re: tunable radiators phorum question?

Post by kg1961 »

so they need more space than other sealed but the same or less than ported? boston make a loaded box small with it on the other side?
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Re: tunable radiators phorum question?

Post by shawn k »

kg1961 wrote:so they need more space than other sealed but the same or less than ported? boston make a loaded box small with it on the other side?
Sort of ... similar to a vented enclosure, you can "tune" the system (box, driver and radiator). This is done by adding or subtracting mass to the radiator. With this respect, it is possible to tune high, which will essentially allow you to have good output with a small enclosure. The downside to this however, is (again similar to vented) that you lose considerable output in lower freqencies. It all really depends on how you design the overall system. But realistically, the only significant benefite (that I'm aware of) to passive radiators is to eliminate group delay.

kg... I'm not sure which Boston enclosure you are referring to as I believe they made a couple different variants, but I do have quite a bit of experience with the Boston "Competitor" 10" box that utilizes a passive radiator. This enclosure was pretty small, approximately .5 cu ft and it had pretty good output for such a small box (more than the "average" 10" sealed box) but it definitely lacked low end extension. This was done intentionally by Boston however!!! They very well could have designed it to be a low end hitter, which would have been a much larger box, but their goal was to obviously go with the "small box" needs of the consumer at the time.
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Re: tunable radiators phorum question?

Post by kg1961 »

shawn i was just asking it was a 12" round sub in a smaller say 1.25 cub box
i have always wanted the oval sub 13" but the new one have a higher rms
i would like to find a older one to try they look cool hope they sound good
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Re: tunable radiators phorum question?

Post by Eric D »

shawn k wrote: But realistically, the only significant benefite (that I'm aware of) to passive radiators is to eliminate group delay.
Wrong.

Passive radiators don't eliminate group delay, they actually have more group delay than a vented box. :roll:

Some of the biggest benefits to passive radiators are less noise (chuffing as stipud pointed out), than a port, and the ability to use them when the design requirements for a port become unrealistic, like being 60" long for example does not work well for a lot of setups.
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Re: tunable radiators phorum question?

Post by ttocs »

ding ding ding round 3!!!!! :)(imagine I have a nice rack and you care about my smile)

I have always been a little confused by them but thought it was just an older thing since you rarely see them used in modern designs. Last pair I saw that had them was outta the 70's and didn't sound bad for a single ten but certainly doesn't sound as good as my modern towers with dual powered/ported 10s..........
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Eric D
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Re: tunable radiators phorum question?

Post by Eric D »

Hell, I am beyond not in the mood to fight this battle...

Might as well let some random guy named Vance Dickason do the explaining for me...

http://caraudiomag.com/articles/what-be ... -enclosure

Last line of the section on passive radiators, "Group delay for a passive radiator box is greater than vented boxes or sealed boxes."
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Re: tunable radiators phorum question?

Post by chicago-regal »

Im really interested in this topic, but I thought kg was talking about car auidio not home audio...
So can passive radiators be used in car audio? And what would be the benefits?
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Re: tunable radiators phorum question?

Post by Eric D »

chicago-regal wrote:Im really interested in this topic, but I thought kg was talking about car auidio not home audio...
So can passive radiators be used in car audio? And what would be the benefits?
Some of the biggest benefits to passive radiators are less noise (chuffing as stipud pointed out), than a port, and the ability to use them when the design requirements for a port become unrealistic, like being 60" long for example does not work well for a lot of setups.

My line above applies to both home and car audio.

A lot of companies consider passive radiators, but they don't always make it to market.

Rockford tried multiple times to launch passive radiators with their Punch and Power HX2 models of speakers back near the year 2000. Each time marketing shot them down claiming customers would not be willing to pay the prices for them ($100-$150 is a lot more then a chunk of PVC pipe).

I ran a prototype 15in RF passive radiator on a Punch HX2 12in sub for a short while and was very pleased with the results. To bad they died after the prototype stage.
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shawn k
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Re: tunable radiators phorum question?

Post by shawn k »

No argument here!

I WAS INDEED WRONG ABOUT THE GROUP DELAY! My bad, I appologize for the incorrect info and I'm GLAD it was corrected!!! :mrgreen:

That being said, it IS true about the vent causes 3rd, 4th, and even 5th order harmonic distortion due to resonating effects. The passive radiator does not suffer from this 8)
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Re: tunable radiators phorum question?

Post by shawn k »

shawn k wrote:No argument here!

I WAS INDEED WRONG ABOUT THE GROUP DELAY! My bad, I appologize for the incorrect info and I'm GLAD it was corrected!!! :mrgreen:

That being said, it IS true about the vent causes 3rd, 4th, and even 5th order harmonic distortion due to resonating effects. The passive radiator does not suffer from this 8)


Moral of this post...... man up when you're wrong! :mrgreen:
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Re: tunable radiators phorum question?

Post by Bchester6 »

So I actually have a couple of these Boston radiators...10's in a .5 sealed enclosure from Boston Acoustics with a 10" G5 mounted on the other side (G510RS). Ran them for about a year and can say the increased output was noticeable compared to other similar woofers without. Very efficient set up with little space requirements and I think a smaller enclosure promotes more output because of it's close proximity to the actual driver. It essentially turned my 10 into a 12 is what I'm trying to say. I did steer away to something else only because I demand a little more accuracy out of my subs these days but I would never part with them because they were so good to me. :D I highly recommend for SPL but still prefer good old fashioned sealed for SQ. What's $70 anyways when it comes to this stuff...especially if you like it.
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