BL seal with passive radiator?

[linh811 0]

I know that Fi recommends ported for BL's, but for space reasons, I'm wondering if I could do a BL in a sealed box with one of TCSounds PRs (passive radiator). This will be running off an USAmps 4000DE (1600wrms).

For space reasons, my plan was to go with a 12" BL in a sealed 2.5cf box, with a TCSounds 15" PR (or VMP as they call it)

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=293-682

http://en.wikipedia.org/wiki/Passive_radiator_(speaker)

For those too lazy to click on the PR link "Passive radiators are used instead of a reflex port for much the same reasons—to tune the small volume and driver for better low frequency performance. Especially in situations in which a port would be inconveniently sized (usually too long for practical box configurations). They are also used to eliminate port turbulence and reduce motion compression caused by high velocity airflow in small ports (especially small diameter ones). Passive radiators are tuned by mass variations (Mmp), changing the way their compliance interacts with motion of the air in the box. The weight of the cone of the passive radiator should be approximately equivalent to the mass of the air that would have filled the port which might have been used for that design."

Or would I be better off with a Q in the exact same enclosure with the same PR?

Basically I'm trying to get the SPL of a BL in a ported box, but don't have room for a ported box, so I'm trying to get away with using a 15" passive radiator. Height is not the issue my in trunk, but depth is. Would a 18" PR work any better?

I listen to all sorts of music, but would like as flat a response as possible from about 25-75hz...

thanks in advance.

Linh

Edited July 30, 2010 by linh811

[Adrian_D 520]

Good idea to use a PR to save space. And the box won't be sealed, it will still be a ported box, you are just replacing the port with the radiator.

The main problem I see is forces in a car. Having a PR "fire" horizontal, you will have a lot of weight hanging off it's suspension. Hit a bump or a pothole and you can damage the PR. If it sits vertical you will get droop because of the weight.

[linh811 0]

Good idea to use a PR to save space. And the box won't be sealed, it will still be a ported box, you are just replacing the port with the radiator.

The main problem I see is forces in a car. Having a PR "fire" horizontal, you will have a lot of weight hanging off it's suspension. Hit a bump or a pothole and you can damage the PR. If it sits vertical you will get droop because of the weight.

Yeah that was the exact idea, to have the SPL of a ported box but the size of a sealed box. I'm assuming the weight of these PRs are much lighter than the BL with it's spiders, coils, and motor etc.... Can you please elaborate on why "forces in the car" would be any different for a PR versus a regular driver?

Also, do you see a problem with using a BL with a PR instead of a traditional port? Or am I still better off with a Q and a PR?

thanks again,

Linh

Edited July 30, 2010 by linh811

[Adrian_D 520]

To tune the PR you attach weight to the moving assembly and the spider could end up supporting 2-3 lbs of weight. What happens when you hit a bump and you have 2lbs of metal washers attached to the spider ?

[linh811 0]

To tune the PR you attach weight to the moving assembly and the spider could end up supporting 2-3 lbs of weight. What happens when you hit a bump and you have 2lbs of metal washers attached to the spider ?

would going with 2 15" PRs or a single 18" PR lessen the likelyhood of having to attach so much weight to the end of the spider for low tuning? Again, my size constraint is depth, not width or height, so I have room for multiple PRs....

I'm considering a 2.5cf box, a single 12" Bl on 1 side, and 2 15" PRs on the opposite side.... I'm trying to create a shallow of a box as possible...

thanks again for your thoughts

Linh

Edited July 30, 2010 by linh811

[linh811 0]

To tune the PR you attach weight to the moving assembly and the spider could end up supporting 2-3 lbs of weight. What happens when you hit a bump and you have 2lbs of metal washers attached to the spider ?

would going with 2 15" PRs or a single 18" PR lessen the likelyhood of having to attach so much weight to the end of the spider for low tuning? Again, my size constraint is depth, not width or height, so I have room for multiple PRs....

I'm considering a 2.5cf box, a single 12" Bl on 1 side, and 2 15" PRs on the opposite side.... I'm trying to create a shallow of a box as possible...

thanks again for your thoughts

Linh

[007 0]

To tune the PR you attach weight to the moving assembly and the spider could end up supporting 2-3 lbs of weight. What happens when you hit a bump and you have 2lbs of metal washers attached to the spider ?

would going with 2 15" PRs or a single 18" PR lessen the likelyhood of having to attach so much weight to the end of the spider for low tuning? Again, my size constraint is depth, not width or height, so I have room for multiple PRs....

I'm considering a 2.5cf box, a single 12" Bl on 1 side, and 2 15" PRs on the opposite side.... I'm trying to create a shallow of a box as possible...

thanks again for your thoughts

Linh

^ I wouldnt do that, dual 15" VMP with 1 12 is totally not necessary. one 12 to one 12 is a good fit for most applications, but a system model would be a good idea. And two pr's actually needs more mass individually that one to reach the same tune. The mass won't break it either, I'm not sure what experience Adrian has had with TC passives, but that is just not the case with these.

I can give you some further assistance with the design, check your PM.

Edited July 30, 2010 by 007

[NDMstang65 403]

You're going to turn that PR inside out before you break the sub. The rule of thumb is double the cone area of what you originally have.

Just a FYI.

If you ask..we can probably make you some PR's that would work..and not fall apart

[j-roadtatts 1,129]

You're going to turn that PR inside out before you break the sub. The rule of thumb is double the cone area of what you originally have.

Just a FYI.

If you ask..we can probably make you some PR's that would work..and not fall apart

You da' man Nick!! I love my FI!!

[linh811 0]

You're going to turn that PR inside out before you break the sub. The rule of thumb is double the cone area of what you originally have.

Just a FYI.

If you ask..we can probably make you some PR's that would work..and not fall apart

I spend most of my time in home theatre, relatively new to car audio, where the rule of thumb has always been at least double the cone area. Many guys on the home audio forums have as much as 3-4 PRs per active driver. But then again, for HT we're looking for flat responses down to 15hz....

You know what I'm trying to accomplish (ported SPL from a BL driver, but in a shallow as possible enclosure). I can dedicate about 2.5cf gross volume for the box, larger if absolutely necessary. Can you make me a pair of 15" PR's, and give me recommendations on which options to get with the 12" BL. I'll be running a USAmps 4000DE (1ohm, 1600wrms) I'd like to place the order ASAP (today if possible).

thanks,

Linh

[NDMstang65 403]

You're going to turn that PR inside out before you break the sub. The rule of thumb is double the cone area of what you originally have.

Just a FYI.

If you ask..we can probably make you some PR's that would work..and not fall apart

I spend most of my time in home theatre, relatively new to car audio, where the rule of thumb has always been at least double the cone area. Many guys on the home audio forums have as much as 3-4 PRs per active driver. But then again, for HT we're looking for flat responses down to 15hz....

You know what I'm trying to accomplish (ported SPL from a BL driver, but in a shallow as possible enclosure). I can dedicate about 2.5cf gross volume for the box, larger if absolutely necessary. Can you make me a pair of 15" PR's, and give me recommendations on which options to get with the 12" BL. I'll be running a USAmps 4000DE (1ohm, 1600wrms) I'd like to place the order ASAP (today if possible).

thanks,

Linh

Not a problem doing that.

Go ahead and order the sub off of the website how you want it. Immediately after ordering the sub shoot an email to orders@ficaraudio.com and sales@ficaraudio.com with your order number (It will be a I-1xxxx/00 number) stating that you were wanting the passive radiators. We'll do them for $85 a piece. Put your phone number and contact information in the email so we can get in touch with you to charge your credit card for the passive radiators as we do not have those coded in and available on the website.

Thanks,

Nick

[Basstamer 0]

"Now that is Customer Service at it's BEST"

[007 0]

You're going to turn that PR inside out before you break the sub. The rule of thumb is double the cone area of what you originally have.

Just a FYI.

If you ask..we can probably make you some PR's that would work..and not fall apart

^ I see the professional maturity has not diminished. I really hope i get to meet you one day.

1:1 ratio w/ TC Sounds designed woofers and passive

http://www.sunfire.com/productdetail.asp?id=8

cheers

Edited July 31, 2010 by 007

[NDMstang65 403]

You're going to turn that PR inside out before you break the sub. The rule of thumb is double the cone area of what you originally have.

Just a FYI.

If you ask..we can probably make you some PR's that would work..and not fall apart

^ I see the professional maturity has not diminished. I really hope i get to meet you one day.

1:1 ratio w/ TC Sounds designed woofers and passive

http://www.sunfire.com/productdetail.asp?id=8

cheers

Being professional, and being honest is two completely different things.

I'm just honest, don't believe in bending anybody over on products and ripping anybody off, give a man a fair shake and he will return the favor...and I don't believe in sugar coating anything to make it seem like something it isn't and in my professional opinion, due solely on track record and field observation, my comment is 100% accurate. The function of a high roll surround where it snaps and puckers works nothing short of horrible, and metallic cones snap. You yank the surround to the mechanical limitation and it tacos the cone like a fat chick in a lawn chair.

I don't come to your court and tell you how to play ball, so stay out of mine...you come here with a target on your head. I'm not a bit scared to pull the trigger.

[95Honda 486]

You are going to get a killer deal on those passives.... He is probably going to build you ones with the same quality parts as the normal drivers... These types of passives are usually almost twice that expensive....

[Warbleed 1]

I love passives. Be excessive. 2x Vd is the rule of thumb, as a MINIMUM. As Nick said, the end result of you underestimating how much PR displacement you need is you end up with an expensive new bowl/hat. The TC passives aren't terrible, but they are rather heavily overpriced. Also, overexcurting metal cone = bad. You don't want to do that. Wood pulp/paper flexes, metal bends, and stays bent.

[linh811 0]

I love passives. Be excessive. 2x Vd is the rule of thumb, as a MINIMUM. As Nick said, the end result of you underestimating how much PR displacement you need is you end up with an expensive new bowl/hat. The TC passives aren't terrible, but they are rather heavily overpriced. Also, overexcurting metal cone = bad. You don't want to do that. Wood pulp/paper flexes, metal bends, and stays bent.

I finally got around to ordering the BL, was too busy at work yesterday.... Nick should be getting my email shortly for the passives.... I've been in home theatre for a long time, and it's not uncommon at all for those guys to go with 4x Vd. That's why I'm going with a 12" BL and 2 15" passives....

[linh811 0]

You are going to get a killer deal on those passives.... He is probably going to build you ones with the same quality parts as the normal drivers... These types of passives are usually almost twice that expensive....

I would hope so.... The only passives I'm aware of that are 'twice as expensive' are the TCSounds and Bostons... Parts express carries quite a few passives for much less, actually..... and many on the home theatre forums have used the cheaper parts express passives very successfully. I want to go with Nick's 'custom' Fi passives for appearance's sake - the BL and the passives will hopefully look the same, with the same white Fi logo embossed on the front... I will have to contact him to confirm that the passives will 'look' just like a regular BL driver, even if it means paying 'twice as much.'

thanks everyone, again, for your input.

Nick, you will be receiving my email shortly.

Linh

[jazzy 0]

Any update on the BL/PR project? I looking to do a 15"BL with a 15/18 PR any pics?

[NDMstang65 403]

I never heard anything back from him again..

[jazzy 0]

Well i sent you a email to you today... Still waiting on the price for the 18" PR