High Eff. Low Budget Sub - Ideas Wanted

[AdamThorne]

We've got one of Jack Hidley's 80w 8r / 115w 4r sub amps coming, so now we need to start thinking about what we're going to hook it up to... Anyone care to dream up some stuff with us?

I, and the friend I'm assisting in the build, have become enamored of the big dynamics sound. So while we probably don't need unusually high sound levels (for home listening), high efficiency would be good.

Electronic music is on the menu, but to keep our requirements somewhat modest a solid 30 hz should be sufficient on the low end. The sub is to be partnered with a pair of B20 Changs. Extended low frequency performance would be a plus, but this is intended as a music sub.

Largish (less than 8 cuft) is probably acceptable, and if it can be made thin enough (I dunno, < 8 in.?) to hide behind a sofa then Really Big might be ok.

To keep in line with the inexpensive amp from Jack, a cheap driver is what we're looking for. Just to pick a number, sub-$80. Cheaper is better.

Any ideas? Is the MCM 55-2421 (the $35 8-inch) still showing up regularly? It looks like it's on backorder currently (oh, look, I guess they expect it back in soon). What are some other community favorite bargains? And while I can stick a driver in a ported or sealed box, any proponents of tapped horns and other special boxes are encouraged to speak up...

Thanks for your input!

 

[picowallspeaker]

efficiency ?!?

You guys need a big and expensive 15" woofer to do that ,in a very big cab
(double reflex bandpass enclosure)
Otherwise , pick your favorite between Peerless XLS / XXLS 8 or 10" ,or Tang Bang . A cube with 10" sides ,sealed ,is Ok . Two cubes are better ,placed near the main speakers ,and parallel connected to the same amp .

 

[GM]

Four MCM 55-2421 in ~172 L = ~120 dB/80 W/2 pi from ~30-300 Hz:

GM

 

[AdamThorne]

Thanks for the input!

I was considering the Peerless xls 10" that PE has for $55.

And while 2 of the 55-2421 is do-able (and I would be pretty happy with, except they're 4 ohms each and I don't expect the plate amp wants to see a 2 ohm load), 4 is moving outside of our price range. I'll certainly take the idea to my friend, though. Bill Fitzmaurice's Table Tuba sounds like a pretty good idea for this driver, anyone have experience with it? If you're familiar with the TT, what other drivers have been used successfully? I'll have to research that one some more, if it delivers what it says it sounds like a goodie.

I was also considering MCM Audio Select 12'' Dual Voice Coil Woofer | 55-1465 (551465) | MCM Audio Select. Fs = 25 hz, Vas = 203 L, Sensitivity = 94 db, Xmax = 5.0 mm. So it'd be nice if the Vas was a little smaller, though I haven't actually drawn up a design for it so maybe I can get away with squeezing it a bit. The 94 dB sensitivity is nice. While the Xmax could be greater, it doesn't really need to be able to blare out crazy amounts of dB. I just want it to have a dynamic quality to it, and have it work well with the modest plate amp we've got. Anyone aware of previous successes with this driver?

Any other thoughts?

 

[chris661]

Hi,

I used a pair of the 8" version of that driver. They work well enough, cope with some abuse, and the bass they put out is more than just a one-note thump (though they can do that if you like).

Good luck!

 

[AdamThorne]

Thanks, Chris. Is that this driver? - MCM Audio Select 8'' Dual Voice Coil Woofer | 55-1455 (551455) | MCM Audio Select

That 3.0 mm xmax looks a little thin, do you feel like this driver exceeds it's xmax smoothly, or does it bottom out right away? Do you know if the parameters they list are accurate?

 

[GM]

Thanks for the input!

..........except they're 4 ohms each and I don't expect the plate amp wants to see a 2 ohm load)...........

If you're familiar with the TT, what other drivers have been used successfully?

While the Xmax could be greater, it doesn't really need to be able to blare out crazy amounts of dB. I just want it to have a dynamic quality to it, and have it work well with the modest plate amp we've got. Anyone aware of previous successes with this driver?

You're welcome!

This is what series wiring is for.

Not beyond reading about other folk's 'adventures' with them, including the occasional wienie roast. Plenty has been written about them on various forums, so Google is your friend.

Anyway, like so many folks who drop in here, you want more performance than you can afford in one or more ways, so I gave you the closest match I could think of.

GM

 

[chris661]

Thanks, Chris. Is that this driver? - MCM Audio Select 8'' Dual Voice Coil Woofer | 55-1455 (551455) | MCM Audio Select

That 3.0 mm xmax looks a little thin, do you feel like this driver exceeds it's xmax smoothly, or does it bottom out right away? Do you know if the parameters they list are accurate?

Yeah, that's the one.

I used them in a sealed cabinet, so accuracy of the parameters weren't paramount. They do match the sims closely, however.

When it comes to excursion, they pass Xmax it quite smoothly. They will do 16mm p/p when bottoming out, but they seem happy enough to around 8-10mm p/p. After that, you get harmonics and it becomes easy to locate the sub. Still, 3mm one way is 6mm p/p and it's still linear. Not bad for the price etc etc. Expect 2-3 times the Xmax (p/p) before bottoming out... So that sets the 12" at 20-30mm... Should be sufficient.

Chris

 

[BL21DE3]

Yeah, that's the one.

I used them in a sealed cabinet, so accuracy of the parameters weren't paramount. They do match the sims closely, however.

When it comes to excursion, they pass Xmax it quite smoothly. They will do 16mm p/p when bottoming out, but they seem happy enough to around 8-10mm p/p. After that, you get harmonics and it becomes easy to locate the sub. Still, 3mm one way is 6mm p/p and it's still linear. Not bad for the price etc etc. Expect 2-3 times the Xmax (p/p) before bottoming out... So that sets the 12" at 20-30mm... Should be sufficient.

Chris

Hi Chris,

If you don't mind me asking, where did you source the drivers from? I'm looking at building one of the Bill Fitzmaurice subs (Tuba 18) using these drivers and didn't have any luck sourcing a UK/European distributor.

Regards,
Ewan

 

[chris661]

Hi Ewan,

No problem at all: I used CPC.
--|55-1455|DUAL COIL WOOFER 8" | CPC
They have free shipping over a certain price, so it might be an idea to order some other bits you'll (undoubtedly) need.

I can supply a full T/S PDF if you like.

Chris

Edit - http://www.youtube.com/watch?v=DK7WuH8iIuU - the tape is 10mm along the shortest dimension. At this point, harmonics begin to become prominent. It's fine for levels lower than that. Sorry about the camera's mic quality, it was just to give people an idea of cone travel.

 

[djn]

Hi Adam, I have had many many subs in my room over the years. 97 percent of them sounded great, the rest sucked. However, the best I have ever heard is the Eminence Alpha 15a in an "H" frame with a baffle of 16x16" and 7.5" on eigher side. So for 60 bucks per driver and not even a sheet of plywood, you can have some great subs.

Below are links to Martin Kings paper on these subs and the drivers at PE. Good luck.

http://www.quarter-wave.com/OBs/U_and_H_Frames.pdf

Eminence Alpha-15A 15" Driver | Parts-Express.com

 

[BL21DE3]

Hi Ewan,

No problem at all: I used CPC.
--|55-1455|DUAL COIL WOOFER 8" | CPC
They have free shipping over a certain price, so it might be an idea to order some other bits you'll (undoubtedly) need.

I can supply a full T/S PDF if you like.

Chris

Edit - YouTube - 8" DVC subwoofer excursion - the tape is 10mm along the shortest dimension. At this point, harmonics begin to become prominent. It's fine for levels lower than that. Sorry about the camera's mic quality, it was just to give people an idea of cone travel.

Hi Chris,

Thanks for the reply/link. Turns out I got myself confused and it's actullay the MCM part 55-2421 that I need to source. Looks like I'll need to consider one of the alternative drivers that Bill suggests. Thanks again for the help though.

Regards,
Ewan

 

[AdamThorne]

Hi Adam, I have had many many subs in my room over the years. 97 percent of them sounded great, the rest sucked. However, the best I have ever heard is the Eminence Alpha 15a in an "H" frame with a baffle of 16x16" and 7.5" on eigher side. So for 60 bucks per driver and not even a sheet of plywood, you can have some great subs.

djn - thanks! I frequently wonder about the Alpha 15 in the OB, I've heard good things about them. Since you've some experience with it, here are a couple of questions:

1) Would you call it dynamic? With no cone control and sacrificing output in the bass region to the OB I would expect it to be limited in output quantity, both per-watt and in total. I know it's a robust driver, but I would expect putting it in an OB would start with 2 strikes against it, dynamics-wise.

2) How did you place it in your room? Does it need a lot of space behind it?

Other than that, I like your success percentage! GM has me concerned... I didn't think 30 hz in-room would be too tough, especially since we can go kinda large on the box. I figured I'd just try to find the highest db/watt setup I could and call it good. But now I have to ask myself if I really do need 120 db capacity to make it sound dynamic. If GM thinks so there's probably something to it...

I've been on vacation recently, but hope to do a little more serious work on this project soon. King's Canyon / Sequoia Nat'l Park has been very nice though!

 

[djn]

djn - thanks! I frequently wonder about the Alpha 15 in the OB, I've heard good things about them. Since you've some experience with it, here are a couple of questions:

1) Would you call it dynamic? With no cone control and sacrificing output in the bass region to the OB I would expect it to be limited in output quantity, both per-watt and in total. I know it's a robust driver, but I would expect putting it in an OB would start with 2 strikes against it, dynamics-wise.

2) How did you place it in your room? Does it need a lot of space behind it?

Other than that, I like your success percentage! GM has me concerned... I didn't think 30 hz in-room would be too tough, especially since we can go kinda large on the box. I figured I'd just try to find the highest db/watt setup I could and call it good. But now I have to ask myself if I really do need 120 db capacity to make it sound dynamic. If GM thinks so there's probably something to it...

I've been on vacation recently, but hope to do a little more serious work on this project soon. King's Canyon / Sequoia Nat'l Park has been very nice though!

I would call it very dynamic. The cone control comes from the high Qts so it never sounds like it is flopping around. It is tight, fast, detailed. Will it make the hair on my head fly back like the Pioneer ad from the 70? Only if I turn it up.

My room is fairly large and the guy who built the house was the chief audio engineer for Ford motor back in the 60s. He built this addition to Paul Klipschs "perfect room" specs. So I am starting with a great room that hides no flaws. It is also JUST AND ONLY a listening room so I have alot of room for placement arrangements.

The center of the "H" frames are 32" from the back wall and 77" from the side walls. When I had the "H" frames a foot from the back wall, they where solid down to 30hz with a bump at 60hz, now that they are pull away from the back wall, they are a bit rolled off (maybe 2 or 3db) at 30hz but are dead flat up to 200hz where they are crossed to the horns.

Get a SPL meter from Ratshack and start playing your music as loud as you can tolorate it, the turn on the SPL meter. You may be surprized at how low the SPL really is. I know that I can't listen for very long at 100db....just can't.

To be fair about all this, maybe I am overly hyped about these as in my mind, there was NO WAY a woof in an OB could ever sound good. I am still amazed at how good they sound.

The real kicker is that for the price of 2 drivers and a sheet of plywood, you will get such great value. Your expectations of what a good sub should sound like maybe totally different from mine or GMs or anyone else, so these have been my impressions only.

I would think that if you found someone in your area that uses these, it would be to give them a listen first. Here is the yahoo groups site for MJK

quarter-wave : Quarter Wavelength Loudspeaker Design