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ISO Boston Acoustics SPG-TR

2K views 24 replies 7 participants last post by  Aaron D 
#1 ·
Product Brand & Model:

Boston Acoustics SPG-TR Passive Radiator

Condition of all items:

New/Used

Total Price: :

Willing to pay what it takes

Shipping Terms: :

I pay

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Additional info:

I know I made another thread with this already but it didn't have to proper model name and was also asking for the sub. Well I already have the sub and now am in desperate need of the Passive Radiator. Thus if someone has one and doesn't really want to sell it lets talk maybe I can convince you otherwise.








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#3 ·
Damn when did you do that? I actually called them like 10 days ago before I went out of town and the guy said they had them, I didn't have the cash so I said id call back in a week. When I did they said they didn't have any, it was devastating. I have even call them two different times since then hoping someone else would find it but to no avail. If you ever switch setups please let me know ill buy it off you if I haven't found one yet
 
#6 ·
Does the PR have to match? Are you willing to use another PR? Namely a round one?
 
#7 ·
Actually I already own the Boston GTR 10 that I used with my 10 inch G5 but I heard that its not ideal to use it with a sub that doesn't match so unfortunately I do need the SPG Passive Radiator. I wish this wasn't the case though as I am having an extremely difficult time finding one...
 
#9 ·
The passive does not have to match. And yes I would not run the 10" passive with the larger speaker. But a 12" or 15" would work and be much easier to find. Just make sure the one you would get has enough excursion

Now if its aesthetics you are trying to match, then obviously keep attempting to find the SPG.

With my TC3000, while I would have loved to run TC passives, they were half the cost of my sub. So I went with a set of APR15's. I loved the front loading design for adding mass. And they were half the price of the TC's.
 
#10 ·
Hmmm very interesting, I had only seen the Boston and one Focal passive radiator, didn't even know there were others. This is very good to know, I have heard that it is ideal to have twice the amount if passive radiator as the sub, so for a 12 inch sub you have 2 12" PRs. This makes me want to lean towards the 15" one you listed. Do you know what frequencies the weights tune to? For instance for the Boston ones they varied from like 45 hz to 30 hz depending on the weights.
 
#11 ·
A passive radiator is like a port. The sd of the pr is like the port area. The weight/mass is the like the length the port. The tuning is based on those two parameters along with enclosure volume.

So to figure out tuning and weight, we need to know the PR and quantity and the desired tuning frequency.

The 2x sd for a PR is not always necessary. Sometimes you can get away with less especially lower power or higher tuning instances.
 
#15 ·
I actually appreciate that honest feedback, what sized box do you have? What do you find its lacking? Right now I have it in a terrible setup while I wait for a new box. But I bought this instead of the JBL MKII specifically because i didn't want to go ported and thought the PR would do the job.
Add/remove weight to adjust tuning. adding weight lowers the tuning frequency and removing weight raises tuning frequency.

The beauty of PR's is that you can adjust tuning easily. the box requirements are less as you are not having to account for the volume of the port. There is no pipe resonance, port compression, port noise, port distortion if inadequately sized.

If you inadequately account for your PR size, you run out of PR stroke. Much less telling on the ears.

I suggest playing with test tones and weights when tuning your PR/s. then you will get some idea of actual tuning and integration with your system. Plus you can then tune to taste.
 
#14 ·
I actually appreciate that honest feedback, what sized box do you have? What do you find its lacking? Right now I have it in a terrible setup while I wait for a new box. But I bought this instead of the JBL MKII specifically because i didn't want to go ported and thought the PR would do the job.
 
#16 ·
I have about 7 woofers, 13w7AE, Boston 555 with PR, JBL MK GTI 15"(heavnt used), Polk SR 12, blaupunkt vw1000 (haven't used), 2 alpine type X 12s, and a polk C4. The 13w7 and type x got really low, the 15" I havent had the pleasure of using, but if I dont like how the type Xs sound I'll probably test it out. I have all the facotry weight added to my PR, I went with 1.6ft net and it doesnt sound bad, but it just doesnt get as low as I would like. Im just saying, I wouldnt spend gobs of money on a port and a box, I would debate a different woofer personally or porting and trying that first.
 
#17 ·
add more weight to see if that helps.

The quick and dirty way to determine tuning is play tones starting at say 40 hertz and watch to see at what frequency tone the woofer hardly moves and the passive radiator is doing all the work. Below that frequency, the sub should start to flap pretty hard as it unloads below tuning (like a ported enclosure).
 
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