Dual T18 vs Dual T39 (aka bass on the cheap)

[Dave Non-Zero]

+1 if its a dual driver cab, one driver could be out of phase. seems exactly the symptoms. you push it and push it and you wonder why its not getting much louder....

[jbell]

Thanks for the out of phase reminder. After Wi's phase issue, yea I hear you.

However I brought both sets of driver wires out of the cabinet, and they are right. BTW -- funny thing, with drivers out of phase I get a real funny sound, but still get 102db@12volts, but (wall loaded, outdoors) I get 113db@12volts in phase.

I would have assumed I would have gotten a lot less, out of phase???

[Sydney]

I get a real funny sound, but still get 102db@12volts, but (wall loaded, outdoors)

Evenly 102db across the bandpass?
or
Unevenly, with some frequencies higher/lower db than others?

[jbell]

I was only passing 60hz sine wave, and the fundamental was gone when out of phase, but the harmonics(I'm assuming) an octave higher or some kind of mush were still there. I didn't drag out my testing equipment to know for sure. It's just easier to gut check things with a 60hz and a spl meter.

really weird...

[Bill Fitzmaurice]

I would have assumed I would have gotten a lot less, out of phase???

Out of phase you should get next to nothing, so something in there is AFU.

[Dave Non-Zero]

Curiouser and Curiouser.

[davygrvy]

I'm surprised you didn't throw an AT into this battle!

jbell, I'm loading the truck now with my ATs.. I'll be there mid day tomorrow..

In all seriousness, great test. I really like your power amp! I would have never thought of that.

[Haysus]

I find this topic interesting. But I have a question or two. I am a newbie and I just finished my first BFM cab.
Skeptical at first but WOW. I am seriously looking to build 2 t-39's to replace my 18" subs for my band and pack space is always an issue. Should I build 4 T-18's for the price and space of 2 T-39's and accomplish more volume and feel while offering total P.A. flexability (i.e. small venue 2 t-18 vs. larger venue 4 T-18).

[klocwerk]

I find this topic interesting. But I have a question or two. I am a newbie and I just finished my first BFM cab.
Skeptical at first but WOW. I am seriously looking to build 2 t-39's to replace my 18" subs for my band and pack space is always an issue. Should I build 4 T-18's for the price and space of 2 T-39's and accomplish more volume and feel while offering total P.A. flexability (i.e. small venue 2 t-18 vs. larger venue 4 T-18).

I think JBell and his dualie T18s are long gone from the BF forums, and to my knowledge no one else has built this particular configuration.
I've been wanting to throw one together and do a decent measurement sweep but I just bought a house this summer and my project list is longer than my arm already.
If you go ahead with it, let us know how you fare!

[Mikey]

Should I build 4 T-18's for the price and space of 2 T-39's

Bear in mind that the MCM and TB 8s are hifi drivers, not pro drivers. I don't think anyone has yet tried using either of them for Pro PA, with a full band, probably for that very reason. If you want to be the tester, that's up to you, but hundreds of BP102-loaded T39s have been built with great success, so it's performance and limitations are well-known. Most people prefer a safe, sure thing.

[RubiconProSound]

Bear in mind that the MCM and TB 8s are hifi drivers, not pro drivers. I don't think anyone has yet tried using either of them for Pro PA, with a full band, probably for that very reason. If you want to be the tester, that's up to you, but hundreds of BP102-loaded T39s have been built with great success, so it's performance and limitations are well-known. Most people prefer a safe, sure thing.

I've been running my MCM loaded T18's exclusively for weddings and general events in the 100~150 people range with no issues yet. I certainly wouldn't use them for anything bigger but so far so good. I don't know how they would hold up to live sound but I've been running bass heavy dance music through them at high levels for months.

[bgavin]

The disadvantage to the MCM 8" is the low input power rating and its too-low Fs. This is a great HT driver to produce VLF content. Not necessary with live work. A driver with a higher Fs (3015LF) is better suited, and with a horn to match.

My T39 rolls off quickly below 40 Hz. I don't miss it at all, even with 5-string basses. I get a great live sound from T39 above 40 Hz, and that includes supporting DJ music in between live acts.

[Mikey]

The disadvantage to the MCM 8" is the low input power rating and its too-low Fs. This is a great HT driver to produce VLF content. Not necessary with live work. A driver with a higher Fs (3015LF) is better suited, and with a horn to match.

My T39 rolls off quickly below 40 Hz. I don't miss it at all, even with 5-string basses. I get a great live sound from T39 above 40 Hz, and that includes supporting DJ music in between live acts.

My garage is almost ready for me to start making with the sawdust, and a pair of W8-740C-loaded Nid ATs are #4 & 5 on my build list. I'm anxious to see how they do for bass guitar. The TBs have higher Vd than BP102s (264 vs 207), so I anticipate that those little cabs will belt some major sound.

[RubiconProSound]

The disadvantage to the MCM 8" is the low input power rating and its too-low Fs. This is a great HT driver to produce VLF content. Not necessary with live work. A driver with a higher Fs (3015LF) is better suited, and with a horn to match.

I agree...I 'll take T39's over the T18's any day. My T18's were an experiment that became my "small event" subs mainly because of the small pack space. I was purely commenting on how the MCM 8's have held up.

Bruce, what driver and size did you go with on your T39's?
I'm getting ready to build 4 and I was thinking if you ever needed 4 more in a pinch I could bring mine down the hill for you to use... I'm also building OT12's...

[Sydney]

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