BFM T48 vs. SP.com 186

[djtecthreat]

Let me premise with a picture (thats my father with it) of my newly finished T48 and also say that we have the wood to get started on another 3 in the coming week. Just need some more hardware and I need to refill my propane tank to heat the shop.





My T48 is @ the 24.5" size (like the plans) and is loaded with a 3015LF (like the plans). & without the optional chamber reducer panel.

My 186's are @ all the correct sizes, and have been loaded with all of the recommended drivers, but for sake of this review, the one I compared the T48 to is loaded with a RCF L18 P300, which is a good driver, just a bit expensive if one were building a block of 8 subs (my plans for the next year).

I spent a little less than $300 to build the T48, this includes paint. I got my drivers from a local guy that was planning to build T48's and gave up. So I ended up getting 4x 3015LF for half price in their boxes, otherwise I would have ordered them from Leland.

I spent about $600ea to build the 186's with recommended drivers made with 3/4" BB, not including handles and paint. Mine are unpainted and have no handles because I decided not to even run them.

The T48 is a one man lift when built from 1/2" Arauco. I have 4 handles at the top and bottom reflectors, plus 2 in the mouth (like the plans). I can grab them from the back the long way (one hand at the top and one at the bottom) and put them right in my truck. I didn't put wheels on them, I will make small wheel boards to move them with.


Ok, so what do they sound like?

The weather here sucks, so I haven't been able to let the T48 rip outside, but I set them up in my basement which has a 7-1/2' ceiling with a poured cement floor, and its a big room, its about 50'x60' I didn't RTA them because I don't have a measurement mic here and I didn't have time to get involved with that, plus its a wash indoors anyway, so spring time I will RTA a single and a stack of 4, I also need to RTA the OTop12's i'm building.

I powered both cabs off each side off one of my PLX1802 set at them same output voltage and I just switched between the 2 cabs. Used a DCX2496 I set them with a HPF@ 29hz, and a LPF@ 90hz. Put them both side by side up against the far wall of my basement (which has some things in it, but for the most part is pretty empty.

I used a tone gen on my laptop to sweep them from 30 to 100 or so. The T48 was audible through the entire range, with peaks in the 50-60hz range. The 186 was very quiet and then became very audible at 70hz.

I then played some tunes through them, it's worth mentioning a have JBL Eon's laying around, So i stuck one of these on a stand at the back wall so I can compare each sub with a top.

I played a wide range of music, even some live stuff. The T48's did awesome in the kick and electric bass, as well as the dance and techno. It lacked in the sub bass region (I didn't intend to get much below 35hz out of it anyway).

The 186 only produces the kick (from my extensive testing with this horrible design) from techno/dance well. It produces the other frequencies, but it seems to be a huge spike in the upper 70's to lower 90's causing it to produce a lot of kick.

The T48 still isn't what I expected, but at least 100 times better than the 186 in regards to output and frequency reproduction. I still have to fill the bottom of the chamber in the T48 to increase the sensitivity.

(Side note: Who has done this and can comment on the results, The T48 wasn't giving me as much volume as I thought it would for the power I was dishing into it. Or do these really open up in pairs of two+ (I know, I know, horns & heards). I like the bass to be heavy and I'd MUCH rather have to back the lows down, to match the tops, than the other way around and my JBL Eon 15 was keeping up with the T48, and passing it on some songs.

[Zack Brock]

(Side note: Who has done this and can comment on the results, The T48 wasn't giving me as much volume as I thought it would for the power I was dishing into it. Or do these really open up in pairs of two+ (I know, I know, horns & heards). I like the bass to be heavy and I'd MUCH rather have to back the lows down, to match the tops, than the other way around and my JBL Eon 15 was keeping up with the T48, and passing it on some songs.

I can't speak about the T48, but I can say with my experience wtith my Tuba24 cabs that it took a bit for the woofer surround to loosen up. Once the surrounds loosened up - WHOA. So perhaps you just need to break your drivers in a little bit first?

[wallywally]

Did you break the driver in? Check for leaks?

[djtecthreat]

What's break in procedure for the 3015LF? I gave it like 9 volts I think @ 25hz and let the cone dance for about 8 hours.


I couldn't find any leaks.

[Bill Fitzmaurice]

Your 186 performs as one would expect with a horn that short. I would reserve final judgment on the T48 until you have at least two of them on line, and you've tried them in a room with a high enough ceiling to allow them to work, at least 10 feet. Since you plan on running four I would not reduce the rear chamber size.

[djtecthreat]

Your 186 performs as one would expect with a horn that short. I would reserve final judgment on the T48 until you have at least two of them on line, and you've tried them in a room with a high enough ceiling to allow them to work, at least 10 feet. Since you plan on running four I would not reduce the rear chamber size.

I'm reserving judgement on the T48, which is why my build of 3 more is still in full swing and will be underway shortly.

I plan to occasionally run 2 in smaller places and situations where less bass is acceptable. What are the effects over a stack of 4 if I run the larger chamber? I know that the smaller chamber doesn't make a considerable difference because the overall sensitivity is high anyway, but doesn't coupling the 4 together bring the response down as well?

[Bill Fitzmaurice]

doesn't coupling the 4 together bring the response down as well?

It does, but that's not the point. Once you get to four cabs the smaller chamber just doesn't offer as much benefit as the larger.

[Chris_Allen]

What's break in procedure for the 3015LF? I gave it like 9 volts I think @ 25hz and let the cone dance for about 8 hours.

That has been ok for my other drivers but I think the 3015LF takes a little more 'warming'. I broke mine in for a number of hours but they still got loader in use. I think they may need a few more Volts than the smaller drivers. It's such a difficult thing to measure.

[thijs666]

I did a party last weekend (still have to find the time to edit and post the pics) with 2 T48's and 4 DR200's. They were a good match. Placing the subs for the best sound was a pain in the ass, though . I didn't manage to get a uniform sound throughout the whole 'cave' (pics of the site see http://www.grotten-van-kanne.be/nl/gallerij.php), but the T48's still performed very well. Even frequencies below 40 Hz were VERY audible, or should I say tangible .

What's 'tricky' with Bill's designs is that they don't distort as much as a direct radiator. As a result the sound you get when you turn up is a bit different than 'normal': it stays clean right up to the max . Your ears don't tell you that the speakers are working hard because the sound stays very clean. When I set up I turned it up to the max and it was still a pleasure to listen to, but when I turned it down, I already had a little ringing in my ears , from only 1 or 2 minutes of sound. (Needless to say I wore earplugs the rest of the night). So it definately IS loud, but doesn't sound like it like you might be used to...

I'm sure you'll be happy with 4 of them when you're finished, but setting them up so you get the best out of them will probably take some time. I still liked the sound of my set best when I set up outside. Although you can't use boundary loading, the openness of the sound and the absence of room resonances does a lot for your quality! Maybe you have some nasty room modes that are playing up. For that matter: sub 40Hz didn't seem to come alive within 6 meters or so. If I moved further away, the sub end seemed to gain a lot on the higher bass frequencies.

The 3015 LF's do indeed need a lot of time to loosen up, but 8 hours @ 25Hz/9V would seem a nice 'warming up' for them. But they tighten up again if you leave them unemployed...

Although my 2 T48's perform fine, I do still have plans to build two 30" T48's eventually though, but that's because I'm insane

[djtecthreat]

I filled the chamber with "Greatstuff" on Thursday night, I finally had a chance to fire it up today, and it was perceptually twice as loud. And caused several things to fall down upstairs.

If you're planning to run a single one of these, definitely fill the bottom of the woofer chamber.

I stripped a T-Nut when I first installed the woofer, so taking it out was a nightmere, it came down to putting a cut off disc on my Dremel and chewing up the back side of the woofer frame to cut the screw head off. Had no choice.


Any tips for getting a woofer out of the bolt is seized in the T-Nut/Hurricane Nut? The nut was spinning freely in the wood.

[Tim A]

I filled the chamber with "Greatstuff" on Thursday night, I finally had a chance to fire it up today, and it was perceptually twice as loud. And caused several things to fall down upstairs.

Sounds like more than going to a smaller chamber, it sounds like you sealed a leak or two with the foam.

[djtecthreat]

I had bleed out on all joints. Although I guess it's possible, I highly doubt there were any leaks.

[Tim A]

I had bleed out on all joints. Although I guess it's possible, I highly doubt there were any leaks.

Did you test? Bleed out tells you nothing. I had a T-24 one time with full bleed out everywhere, and a leak that sounded like a pressure cooker. If the cabinet isn't tested, the cabinet isn't done.

[djtecthreat]

Yes, I tested. But I can't think of any way to truly test for leaks on the INSIDE of the cabinet.

[Sydney]

An impedance sweep will tell you if you have one...
It won't tell you where it is however.