Hi Chris,
Does the subwoofer have to be OB? The lowest Altec in a vented box is the 411-8A but it requires a HUGE 15+ c.f. cabinet - see attached. I have a pair I need to try sometime.
I like the Eminence Alpha 15A in an H-Frame per MJK for OB. Some don't like the small magnet and opt for the Beta 15.
Does the subwoofer have to be OB? The lowest Altec in a vented box is the 411-8A but it requires a HUGE 15+ c.f. cabinet - see attached. I have a pair I need to try sometime.
I like the Eminence Alpha 15A in an H-Frame per MJK for OB. Some don't like the small magnet and opt for the Beta 15.
Attachments
OK, I'll chime in. I've done a fair bit of OB and don't think the standard 416 is a good fit for bass. Midrange on OB? Sure. Now that said, I have owned at least four 416s that had a Qts of about 0.7, making them fairly ideal for OB. I also used to run a pair of Selenium 15" that had a Qts of 0.7 and loved them on OB.
You can certainly use lower Q woofers on OB, but you'll have to trade away a lot of top end to get a proper tonal balance. That can work OK with certain drivers. A healthy X-max helps. The trick to OB is that you need to flatten the woofer's rising response. With a low Q woofer, that can be quite a rise. You might have a woofer that is 96dB/W on infinite baffle, but you'll end up at 85dB on OB once you flatten it. That's the laws of physics.
If you can find a cheap 18" with a Q of 0.8 or higher, you could still use your 416s as low mids. I have a pair of MCM 21" woofer that are high Q and are rather amazing on a large open baffle. Play right down to 22Hz with no EQ needed.
You can certainly use lower Q woofers on OB, but you'll have to trade away a lot of top end to get a proper tonal balance. That can work OK with certain drivers. A healthy X-max helps. The trick to OB is that you need to flatten the woofer's rising response. With a low Q woofer, that can be quite a rise. You might have a woofer that is 96dB/W on infinite baffle, but you'll end up at 85dB on OB once you flatten it. That's the laws of physics.
If you can find a cheap 18" with a Q of 0.8 or higher, you could still use your 416s as low mids. I have a pair of MCM 21" woofer that are high Q and are rather amazing on a large open baffle. Play right down to 22Hz with no EQ needed.
'Sub' woofer is a much abused term in that below the average person's ability to hear down low [20 Hz], anything lower is in the infra-bass [AKA infrasonic, infra-sound] range [ultra, etc., for > 20 kHz], so originally where sub-bass began.
Fast forward many decades to Dolby Digital/THX, which requires a separate low frequency effects [LFE] channel from 20-120 Hz for cinema apps and 20-80 Hz for HT allowed anyone to [mis] claim making an LFE rated [mid] woofer a 'sub' woofer even though it might only go down to 35-40 Hz and never go down to a true sub's BW at any usable output!
In short, for OB/IB recommend using the 80-120 Hz range or even higher depending on the desired lower mids driver's baffle mounted ~flat response lower limit, though as a general rule try to limit it to the driver's upper mass corner [Fhm] for max SQ, best integration.
Fhm = 2*Fs/Qts'
Qts' = Qts + any added series resistance [Rs]: HiFi Loudspeaker Design
GM
Why 15"? At the time the 18" 3182 arrived it was as bad as it gets AFAIK WRT eff., power handling, low Fs: Altec Thiele-Small Parameters
The downside is doubt you'll find any as they tended to stay in service till couldn't be rebuilt anymore.
GM
When I had the GPA 604s, i thought they were great in the cabs they came in. The cabinets were similar to these.
https://www.stereo.net.au/forums/up...bk8g.jpg.f0c4df61f402b2fc2cbdf61571e02728.jpg
If i kept them I would stick 416 woofers in the same cabinet with the 604 on top in open baffle.
I think you will never get the weight you miss in open baffle as it is partly cabinet ringing along with some delay. This is a good compromise between wanting bass punch/weight and depth along with open mids.
https://www.stereo.net.au/forums/up...bk8g.jpg.f0c4df61f402b2fc2cbdf61571e02728.jpg
If i kept them I would stick 416 woofers in the same cabinet with the 604 on top in open baffle.
I think you will never get the weight you miss in open baffle as it is partly cabinet ringing along with some delay. This is a good compromise between wanting bass punch/weight and depth along with open mids.
OK, thanks guys, some great info there, but I am missing an actual answer to my question. I am stuck at 15" as this is the largest my panels can accommodate.
So lets try re-phrasing the question "Is the vintage Altec alnico 15" the best 15" driver to deliver bass below 100Hz in an open baffle with good SQ?
If the answer is no then what are your recommendations?
So lets try re-phrasing the question "Is the vintage Altec alnico 15" the best 15" driver to deliver bass below 100Hz in an open baffle with good SQ?
If the answer is no then what are your recommendations?
Thanks Pano, I do now know all this stuff. What I need are brands names or more specifically model numbers of 15" drivers that people have heard and would recommend in this situation.
Well at least you're funny. Thanks!
I get this hilarious vision of John Cleese standing on the London Bridge yelling "Where's my fish? I want my bloody fish!" after being handed a fishing rod with baited hook.
Good Stuff!
Nice one EarlK. My question is really "I know how to catch fish, but which ones are the tastiest"
So far on my growing list of one I have:
1. Acoustic Elegance Dipole15 woofer for Open Baffle Applications
The Eminence Alpha 15 is a popular choice. I liked my Selenium better, but it's been discontinued.
What are your sources? Where will you be shopping?
I like the Alpha too but prefer it in an H-frame. You can use it on a straight baffle - MJK states the low end is around 40Hz depending on the baffle width.
Pano, what model is the Selenium? or, are you keeping it a secret
Since Q is the drivers inability to return to rest, it's a primary focus in selecting a driver for OB. It's also the reason you won't have slam. Slam requires quick transient response and that requires a very power motor. Look for smaller motors like the Alpha as Pano has mentioned. Nice thing is they will be the least expensive in the model line.
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