Building a BFM Omni 15TB

Count Bassie · #1 05-27-2011, 07:03 AM

I have a few questions regarding this build, what drivers to use, etc with mu Trace Elliot AH250SMX to power it. It's essentially going to be a low-mid-powered section running it at 8 ohms.

Here's the thread over at the BFM forum... any thoughts?

will33 · #2 05-27-2011, 07:54 AM

Off the cuff, I don't think you'd be gaining any SPL using the HO over the LF. The only portion of the chart to look at is up to where it crosses to the mid, the HO's advantages are above that. I haven't seen the charts for the bp102 mod. With the price of neo lately, what's best for you is a choice only you can make. I'd add that depending on the spl of the woofer you choose, you might want to pad back the mid a little, that thing is loud.

Count Bassie · #3 05-27-2011, 08:02 AM

Quote:

Originally Posted by will33

The only portion of the chart to look at is up to where it crosses to the mid, the HO's advantages are above that.

Pretty good note here. I'll probably just do the 15TB and with the LF. If I were to do the 212, I'd want the LFs also, and that'll be nearly twice the bread... so if the 8 ohm cab will be enough heft with my little AH250, I'm done I guess.

Thanks Will33.

will33 · #4 05-27-2011, 08:03 AM

The 3015lf still has high output with less than 300 watts. It gets advised against for people using smaller amps because of it's price. Your basically buying output you'll never hear until you get more power. With hornloading advantages and just having a louder cab, you may not need more power to do what you need to do.

Count Bassie · #5 05-27-2011, 08:09 AM

Quote:

Originally Posted by will33

The 3015lf still has high output with less than 300 watts. It gets advised against for people using smaller amps because of it's price. Your basically buying output you'll never hear until you get more power. With hornloading advantages and just having a louder cab, you may not need more power to do what you need to do.

I take this as a recommendation to get the Deltalite-II 2515. Alright, that's helpful.

will33 · #6 05-27-2011, 08:16 AM

I think the deltalite would be fine with your current setup, the 3015lf would leave the option open for a larger amp in the future but again, you might not need it.

My .02, I'd run it by Bill before pulling the trigger. There may be some other factors to take into account. Other ts parameters affect things differently when you stick the driver in a horn even though the low section on that cab isn't a full on horn.

Count Bassie · #7 05-27-2011, 08:19 AM

Quote:

Originally Posted by will33

I think the deltalite would be fine with your current setup, the 3015lf would leave the option open for a larger amp in the future but again, you might not need it.

My .02, I'd run it by Bill before pulling the trigger.

Right, I'll do so... part of my plan is to have a simple, efficient working amp with a one-trip load-in. It might actually become an 'air-head' mod, even if it adds weight. The tall-ness of it will bring the center of gravity up, and that's not a bad lift. No stooping!

Thanks again, will33.

Count Bassie · #8 05-27-2011, 09:14 AM

And now the hard part. I can get two of the Basslite S2012s and run at 4 ohms. Slightly heavier I guess, but still acceptable. I like the idea of the 3dB increase in sensitivity, but I do worry about my Trace head, which allegedly compares to amps rated at +twice the rated wattage, blowing the thing up.

Got an opinion on this? I'm splitting hairs now I think, as I can make any of this mess work! But it does come to mind.

will33 · #9 05-27-2011, 10:35 AM

It'd be a 300 watt, high output 4ihm cab and the weight gain could be measured in ounces. Haven't seen the chart on it but there has to be some benefit there.

will33 · #10 05-27-2011, 10:55 AM

Power handling shouldn't be an issue with you amp. The 2 basslites shouldn't need more than 100 watts to reach 120db no? Mids/highs louder than that. I wouldn't think you'd be running your amp to full output. Just know there's a limit there on the off chance you really have to goose it, big place/no PA or something but even then, those cabs are a good deal louder than "regular" cabs. Definately a one cab solution unless you're playing stadiums.

Count Bassie · #11 05-27-2011, 12:06 PM

Quote:

Originally Posted by will33

Power handling shouldn't be an issue with you amp. The 2 basslites shouldn't need more than 100 watts to reach 120db no? Mids/highs louder than that. I wouldn't think you'd be running your amp to full output. Just know there's a limit there on the off chance you really have to goose it, big place/no PA or something but even then, those cabs are a good deal louder than "regular" cabs. Definately a one cab solution unless you're playing stadiums.

Pushing it past "4" on the output gain has never really happened. Yeah, I should just dive in here. Here we go...

dhomer · #12 05-27-2011, 12:17 PM

Be VERY careful using non-recommended drivers.. Horn-loaded cabs are a much different animal, and xmax/displacement is something you need to keep into account. There won't be any audible warning before drivers destroy themselves. If you want to go 4ohm, go 2-12 w/Delta 12LF's, you'll thank me later...lol...

Count Bassie · #13 05-27-2011, 12:33 PM

Quote:

Originally Posted by dhomer

Be VERY careful using non-recommended drivers.. Horn-loaded cabs are a much different animal, and xmax/displacement is something you need to keep into account. There won't be any audible warning before drivers destroy themselves. If you want to go 4ohm, go 2-12 w/Delta 12LF's, you'll thank me later...lol...

They are listed as what you can use for a lower-powered amp, along with the 3012LFs for higher wattage. The key word is "x-max", over the power rating. I understand I won't need a lot of the volume knob here. However, this is the reason I was concerned about the Trace Elliot's conservative wattage rating! So your point isn't lost on me. But, my backup head is likely to be a GK 400RB...

Otherwise maybe the 8 ohm cab with the 3015LF is the way to go.

will33 · #14 05-27-2011, 01:47 PM

I'm sure BFM could point out a couple things not thought of here, he did design the cab afterall but the 4ohm, higher spl basslites seem to fit the bill for one cab, smaller amp combo, at least from this end if the internet.

1n3 · #15 05-27-2011, 02:00 PM

Looking at the Eminence charts, at the area under 200hz, which is where most of the power demand falls. Compared to the 3015...

The 3015LF is about 1dB less sensitive, presumably the price of greater excursion. I doubt you could take advantage of that excursion with less than 200 watts.

The DeltaLite 2515 is about 2dB less sensitive.

The BassLite 2012 is about 3db less sensitive.

The Delta 12LF is about 5dB less sensitive.

For both of the 12" speakers, you add 6dB (3 for doubling speakers, and 3 for going to 4ohms).

If you're always going to use a 250w head, any of these should work. From the prices I've seen, the S2012 looks like your best value, followed by the DL2515 if your budget is tight. Obviously, Bill is best qualified to render an opinion here. Looks like I'm echoing will33.

As for the airhead mod, I don't see much benefit there, and potential drawbacks. I'd try to get some more opinions over on the BFM forum, from guys who have actually built and gigged them.

billfitzmaurice · #16 05-27-2011, 02:42 PM

Quote:

Originally Posted by 1n3

Looking at the Eminence charts, at the area under 200hz, which is where most of the power demand falls.

Comparing those is a waste of time, as response below 200Hz is as much the result of the cab as it is the driver, and those charts are not in cab charts, they're standard baffle charts. They're useful for comparing results above 200Hz, where the cab is a relative non-factor. Below 200Hz response modeling software is the only accurate method of comparison.

Which driver to use is well explained in the plans, the best choice being based on your available power. And since a watt is a watt is a watt is a watt don't concern yourself over what brand the amp is.

will33 · #17 05-27-2011, 02:46 PM

I've gone back and forth about the airhead thing. These cabs are tall enough it might make an easy rear handle tilt back and roll which would free up the hand that would be carrying the amp.

That would add weight to the dead lift and I don't know if they're tall enough to tilt back and slide in a vehicle. With any tilt back configuration I'd advise doing a slip covet or carrying a little tarp/plastic sheet in your gig bag in case you have to load out in the rain. The cones point skyward when moving it and even with this design, the mid and tweet will get wet and that bottom horn may scoop some water in as well.

1n3 · #18 05-27-2011, 03:10 PM

Quote:

Originally Posted by billfitzmaurice

... those charts are not in cab charts, they're standard baffle charts... Below 200Hz response modeling software is the only accurate method of comparison.

Right, and I have no way to model the response of an Omni 15. So baffle charts are not even useful as a rough, baseline indicator of performance?

Quote:

Originally Posted by will33

I've gone back and forth about the airhead thing. These cabs are tall enough it might make an easy rear handle tilt back and roll which would free up the hand that would be carrying the amp.

That would add weight to the dead lift and I don't know if they're tall enough to tilt back and slide in a vehicle. With any tilt back configuration I'd advise doing a slip covet or carrying a little tarp/plastic sheet in your gig bag in case you have to load out in the rain. The cones point skyward when moving it and even with this design, the mid and tweet will get wet and that bottom horn may scoop some water in as well.

I'm also fond of the tilt-back idea. It seems the cab is tall enough to do even without the airhead. Don't recall seeing one done that way, though.

Interesting points, particularly about rain on a tilt-back. I've not considered that.

billfitzmaurice · #19 05-27-2011, 03:14 PM

Quote:

Originally Posted by 1n3

Right, and I have no way to model the response of an Omni 15. So baffle charts are not even useful as a rough, baseline indicator of performance?

Not useful at all. As the 015 is a hybrid horn loaded front wave/tapered duct bass reflex rear wave cab the only way to accurately model it is in AkAbak, which is probably the most difficult program to master.

1n3 · #20 05-27-2011, 03:21 PM

Quote:

Originally Posted by billfitzmaurice

Not useful at all. As the 015 is a hybrid horn loaded front wave/tapered duct bass reflex rear wave cab the only way to accurately model it is in AkAbak, which is probably the most difficult program to master.

Yup... as I said - I have no way to model. The sensitivity numbers I posted are generally valid from 200-1000hz as well. (Yes, I know where the crossover is.) But I got it - not helpful. I'll steer clear from now on. Thanks.