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PostPosted: Tue Aug 01, 2017 9:22 pm 
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Hi,

I'm looking for suggestions please for a subwoofer (or 2) for a church hall. Use is likely to be for an electronic organ and for recorded music, but not at rock concert levels.

I am definitely on a budget, as the unit is likely to be built by myself and a mate and donated. I'm after the least expensive option that will do the job adequately, but on the plus side, size is not really a problem as there is a large space under the platform that can be utilised (24" high max), with the mouth facing out to the audience. Corner mounting is not an option unfortunately.

Frequency response to 30Hz would be nice but 40Hz would probably be OK. I will add a MiniDSP for some careful EQ if needed, as well as for a high pass to help protect the driver.

The hall is approximately 40" wide x 70' long by approx. 14-15' high, mainly sheetrock over brick construction, and the basic shape is rectangular. 100-150 people would be normal numbers in the hall although it could accommodate more on some occasions.

I do have several drivers already which it would definitely be preferable to utilize, but I understand that the specs for horns are there for a reason. If needed, I will purchase the correct driver.

Drivers that I currently have access to are:

JBL2225H (2 off): http://www.jblpro.com/pub/obsolete/2225hj.pdf

Audax PR330T0 (1 off): http://www.audax.com/archives/pr330t0.jpg

Audax PR330T4 (1 off) http://www.audax.com/archives/pr330t4.jpg

Thanks for any suggestions!

SS


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PostPosted: Tue Aug 01, 2017 11:30 pm 
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Location: Sarnia, Ont. Canada
Hi, and welcome to the forum!

The drivers that you have are outside the 10% variance for the Qts spec. They will work but not to the same degree as the prescribed drivers. Xmax and Fs are within specs.
T39 takes 10" or 12" drivers (45 hz cutoff)
T48 takes 12" or 15" drivers (40 hz cutoff)
T30 takes 10" or 12" drivers (30 hz cutoff)

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TomS


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PostPosted: Wed Aug 02, 2017 12:32 am 
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Joined: Sun Jul 30, 2017 7:13 pm
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Thanks for the welcome and for the info Tom :-)

Where would I find the spec range for the above cabinets? I'm more than willing to purchase the plans (purchased plans /built the TT Long several years ago) but wouldn't mind knowing the spec range for cabinets that would do the job. Once I know an appropriate cabinet and specs I can start looking for drivers. Most drivers aren't as readily available at reasonable cost here in Australia unfortunately :(

Cheers,

Matt

Edit: are the JBLs remotely useable, or am I best off looking elsewhere?


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PostPosted: Wed Aug 02, 2017 3:00 am 
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Location: Ilfracombe Queensland Australia
Check out the Aussie suppliers thread here:
viewtopic.php?f=14&t=17627

There's a couple of drivers in there that are way below Eminence prices here in Australia (from JD Sound in Vic IIRC) with similar voltage limits, that have been given the nod by Bill.

Tell us more about this platform/stage area...

_________________
Built:
2 x DR 250 (melded array) with March 2012 plans.
4 x 20" BP102 T39's, 2 x 28" 3012lf loaded underway.
3 x WH8 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...


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PostPosted: Wed Aug 02, 2017 4:20 am 
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Thanks for the reply Grant.

I read through the thread you suggested, I could find a couple of the SB Acoustics drivers at WES Components but unfortunately most of the driver links are now old and broken or redirected.

The stage/platform area is pretty basic. It is attached to the front wall, and finishes about 10' shy of the two side walls. Height is around 30-32", and the useful height for putting a sub underneath is 24". Construction of the platform is strong steel framework, and it is timber clad. Effective depth of the platform is around 10'. There is a large hole on the front section of the platform (facing the rest of the hall) covered with a curtain, for storage. My idea was to store a decent sub in there...

The JBL 2225h's will probably be removed from the current 2 way organ speakers, hence my interest in using them for subs if possible. If not, then I'll look into other options. The organ will then be fed into the rest of the PA system.

Regards,

Matt


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PostPosted: Wed Aug 02, 2017 7:01 am 
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Posts: 219
Location: Tilburg, Netherlands
The 2225-h drivers are very useable in horns. Though they have a short VC overhang they have a very strong motor and would perform admirrably in a T48. Thermal and mechanical limit are similar in a T48 you could feed them 40 volts which is pretty much their thermal limit. X-damage is far enough beyond that so that you could feed them that all day every day without worrying about driver damage (provided you brickwall limit them there and high pass at 40Hz.

On a sidenote I don't think putting subs under the stage is a very good idea especially If it's an open space. Resonances and reflections could kill off a lot of output. I would really try to put them somewhere else.


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PostPosted: Wed Aug 02, 2017 4:17 pm 
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Posts: 5647
Location: Ilfracombe Queensland Australia
Matt,
Fixed the links for JDsound (page 2 on the Aussie suppliers thread)
The Ande LB1560 is tried and tested by a number of builders in Australia with good success.
It's selling for $200 at the moment:
https://www.jdsound.com.au/ande-lb1560- ... frame.html

It's voltage limit is 60V. That's probably way more than you'll ever need, but the specs are within acceptable limits.

The same thing can be said about the Ande LB15 spec wise. It has a 48V voltage limit and is selling for $150 now.

https://www.jdsound.com.au/ande-lb15-1- ... frame.html

With a 10 feet deep stage you would need to ensure the mouth is right up to the front of the stage (you will get boundary cancellation with the cabs being anywhere between 2 and 8 feet from the rear)...

_________________
Built:
2 x DR 250 (melded array) with March 2012 plans.
4 x 20" BP102 T39's, 2 x 28" 3012lf loaded underway.
3 x WH8 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...


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PostPosted: Thu Aug 03, 2017 12:47 am 
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Joined: Sun Jul 30, 2017 7:13 pm
Posts: 8
Thanks for that Grant.

The sub mouth would be at the edge of the platform, not buried inside.

Regarding the links to the two drivers, which models of BFM subs would they suit? I'd be looking at an end firing model for this installation.

Regards,

Matt.


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PostPosted: Thu Aug 03, 2017 3:09 pm 
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Joined: Mon Nov 28, 2011 11:12 am
Posts: 5647
Location: Ilfracombe Queensland Australia
T48, which is not end firing.
Could you place the cabs sideways under the stage?

_________________
Built:
2 x DR 250 (melded array) with March 2012 plans.
4 x 20" BP102 T39's, 2 x 28" 3012lf loaded underway.
3 x WH8 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...


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PostPosted: Thu Aug 03, 2017 6:58 pm 
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Joined: Sun Jul 30, 2017 7:13 pm
Posts: 8
That could be a problem, I have more depth than width to play with... the space is also used for atorage, so while depth is not a problem, the width will stop people being able to store stuff under there. Will look at it further.

Cheers,

Matt


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PostPosted: Thu Aug 03, 2017 9:48 pm 
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Posts: 5372
Location: Warren, MI
Sub Sonic, first off, welcome to the forum!

Give us a better picture of your church. Pictures are very helpful, but measurements rule. You can post them in metric or imperial, we can handle both! :lol:

Centered, at the front of the stage, is not likely to be a good spot for a subwoofer. See the placement sticky. If your floor measurements are close, you have 2800 square feet of floor-space, and the stage only takes up about 100 sq/ft. Does the church have tall, cathedral or domed ceilings? Are there any treatments on the walls or ceiling? What mains will be used? how low can the mains be safely crossed over to? How will you power, cross-over, EQ and limit? How heavy is the organist' left hand? You mention 10' spaces to the sides of the stage, can they be used? Can a pair of subs and a V-plate be used as an "extension wing of the stage platform? Horns really prefer to be run in herds of 2 or more.

The T45 meets your end-firing requirement. Do you have access to any proper subs to do some testing? Putting any sub of substance will let you know where to place it for the best coverage.

_________________
I know money often seals the deal, but seriously, quality is an investment, not an expense... Grant Bunter
Accept the fact that airtight and well-braced are more important than pretty on the inside. Bill Fitzmaurice


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PostPosted: Fri Aug 04, 2017 12:05 am 
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Posts: 8
Thanks DJPhatman!

I actually posted the hall size in the first post, I must admit I was mentally converting to imperial for those in North America :D The hall has a regular shape and has no arches etc. One thing I forgot to mention is that it has a suspended ceiling (sheetrock 2' x 4' ceiling tiles) and a pitched tin roof about 10' above that at its highest point.

There are no treatments apart from basic carpet over a concrete slab floor. I am replacing the mains due to some previous issues there, I will be using the existing positions flush mounted in the walls, except for the two rear speakers, mounted in the ceiling. There are 8 off main speakers mounted in this manner, equally distributed through the hall. Not ideal but I didn't design it :wink: Mid bass drivers will be 8" , with twin tweeters per bass driver to help with power handling on the top end. Passive XO is to be used for the mains, but MiniDSP will be used to high pass/limit excursion at the bottom end, as well as for general EQ. I'm hoping for 50-60hz from the mains but that will depend on how excursion tests go. Power for the mains is a pro amp, unsure of power output but it will be one channel driving into a total of 16 ohms... I know, I know, but I didn't design it :-) We also don't use high SPLs.

Organist - we only have one organist, the rest play the piano. I can limit the low frequency extension with the MiniDSP but currently I have no way of limiting voltage. The sub amp is to TBA although I do have a DSP based amp available which I could have a mate program to have dynamic compression/limiting.

The 10" spaces either side of the platform are access/exit ways unfortunately, and so cannot be used, which sadly also excludes V plating. If the sub is under the platform, it will be to the right hand side of the front edge of the platform rather than in the centre, maybe 1/3 of the way across the hall. The platform is probably closer to 200 sq ft.

I do have a couple of 12" Rythmik subs at home I could use (carefully) to experiment with placement, and I also have a Dayton Omnimic & DATS for objective measurements.

Hope this helps, and thanks for your comments!

Regards,

Matt


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PostPosted: Fri Aug 04, 2017 12:44 pm 
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Location: Warren, MI
Sub Sonic wrote:
I actually posted the hall size in the first post, I must admit I was mentally converting to imperial for those in North America :D The hall has a regular shape and has no arches etc. One thing I forgot to mention is that it has a suspended ceiling (sheetrock 2' x 4' ceiling tiles) and a pitched tin roof about 10' above that at its highest point. There are no treatments apart from basic carpet over a concrete slab floor.


I know you did, hence the 2800 square foot dimension. Ask the congregation mums if they would be willing to make some fabric "flags", as hanging them from the ceiling will help, a lot. Bass is omni-directional, and the size of the waves are large enough to penetrate building walls.

Sub Sonic wrote:
There are 8 off main speakers mounted in this manner, equally distributed through the hall. Not ideal but I didn't design it :wink: Mid bass drivers will be 8" , with twin tweeters per bass driver to help with power handling on the top end.


Might I suggest you build either a pair of TLAH Pro or replace the 8 distributed system with 8 half-size SLA Pro? The TLAH would be the best, in this long narrow room, and with its excellent pattern control, only 2 up front would be needed to cover the entire room. As the picture below shows, they can easily be "hidden" in plain sight. Just food for thought...

Image

Sub Sonic wrote:
I'm hoping for 50-60hz from the mains...


If this were a Home Theater system, this would be OK. This is Public Address system. You should have your cross-over from subs to mains around 80Hz to 150Hz, depending on the mains capabilities. The subs on this site all have a rising response rate, meaning you can cross higher without it sounding "wonky" or muddy. Once you build and place, experiment with the cross-over point, type and slope until it sounds pleasing to the ear.

Sub Sonic wrote:
I can limit the low frequency extension with the MiniDSP but currently I have no way of limiting voltage.


Then you ABSOLUTELY need a more adequate piece than a mini-DSP. I know you are on a tight budget and all, but if you do it right the first time, you won't be doing it again, which means no wasted money. For the subs, a proper hard-knee limiter is a MUST, as in not optional. Almost all modern amps, even the cheap junk, have a sizable crest factor. This means something as silly as a dropped mic could send a burst of 10X the power, such as a normally 400W amp would output a burst of 4000W, which will do massive damage to the drivers.

Sub Sonic wrote:
The 10" spaces either side of the platform are access/exit ways unfortunately, and so cannot be used, which sadly also excludes V plating. If the sub is under the platform, it will be to the right hand side of the front edge of the platform rather than in the centre, maybe 1/3 of the way across the hall. The platform is probably closer to 200 sq ft.


Understood, that's why I asked. So this stage platform is about 6 meters wide? Will you be allowed to use any more of it other than the small opening? If the people that make such decisions would allow you to, you could build a pair of T39 to fit under the stage. This would require 2 meters of stage/platform frontage area, with an opening for the mouths. Trying to get any single, budget subwoofer design to work in a hall that large is asking for troubles.

BTW, who controls the mix? Is this done from the stage, or is there a "sound booth"? Just curious.

_________________
I know money often seals the deal, but seriously, quality is an investment, not an expense... Grant Bunter
Accept the fact that airtight and well-braced are more important than pretty on the inside. Bill Fitzmaurice


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