I've been given a pair of eminence alpha 15a's. Is there a good way to get these configured as a Subwoofer? I've modelled it in Hornresp and come out with a possible dual sealed in series about 80ltrs apprx, but the required power and crossover are pretty insane to get low frequencies. 24db roll off+ and lots of power.
I know the driver isn't designed for this, but I have them sitting around and I need a subwoofer... and I'm on a tight budget.
Would it be a lost cause or is it just a case of finding the right amp to drive them?
Any thoughts?
I know the driver isn't designed for this, but I have them sitting around and I need a subwoofer... and I'm on a tight budget.
Would it be a lost cause or is it just a case of finding the right amp to drive them?
Any thoughts?
If SPL isn't a huge requirement, I'd use them as an isobaric pair, mounted in the biggest sealed box you can manage.
Grab an old-iron PA amp, fit a silent fan, and EQ the result.
Chris
Grab an old-iron PA amp, fit a silent fan, and EQ the result.
Chris
If you can place it behind the couch at ear height:
Neighbor friendly dipole sub | www.audiocircle.com
I would suggest one alteration: do not omit the side walls and build a regular W frame.
Neighbor friendly dipole sub | www.audiocircle.com
I would suggest one alteration: do not omit the side walls and build a regular W frame.
Big SPL not at all important. Just a medium sized english lounge for normal listening. Isobaric is interesting as I don't think I can get anything behind the couch. I'll model it.
Those are not subwoofers, with a really weak motor and almost no xmax(3.8mm) they might only be good for a low power guitar rig.
Not the best in the World but still usable, just don´t try to go TOO low, respect their capabilities.
They can move some air, and the average UK livingroom is:
1 - Not huge
2 - Acoustically quite helpful, in terms of room gain. Brick construction helps here.
To give you an idea about (2), my (sealed) speakers are -3dB at 50Hz anechoically. In-room, they peak at +15dB at 40Hz, and are back down to nominal level at 10Hz.
Danb11, would a pair of open baffle speakers be of interest? The Alpha 15A is pretty good at getting some LF on an OB, because of that high Qts.
Chris
I know they're not subwoofers, as I already said. But they are free! It's a hack.
I'm getting the best results on hornresp as dual series 80l eq'd to a solid 30hz can get just under 100db before running out of xmax. Not modelling well isobaric.
Never built subs, so how's that gonna sound in a real world small-medium room supporting mains capable to 50hz? Not trying to shake the walls, but would like to get some low end air.
Chris, as I have sealed mains that do 40hz at a push, I probably don't need open baffle atm, although it would be MUCH easier.
Worth the cost in wood and ebay amp? Or should I just save up?
I'm getting the best results on hornresp as dual series 80l eq'd to a solid 30hz can get just under 100db before running out of xmax. Not modelling well isobaric.
Never built subs, so how's that gonna sound in a real world small-medium room supporting mains capable to 50hz? Not trying to shake the walls, but would like to get some low end air.
Chris, as I have sealed mains that do 40hz at a push, I probably don't need open baffle atm, although it would be MUCH easier.
Worth the cost in wood and ebay amp? Or should I just save up?
In theory, isobaric will just halve the cabinet volume for one driver. ie, if one driver "wants" 80L, an isobaric pair will "want" 40L. NB - you'll need to either change your simulated cabinet volume, EQ, or both to get the response curve to look nice again.
You'll need a lot of EQ (or a steep low-pass filter) to get these to run below 40Hz. What do you have in the way of crossovers/EQ?
I'd say they're worth the cost of a cheap pre-made car sub box. Throw them in (I'd still recommend isobaric) and see what you get. Minimum effort, probably cheaper than you can build yourself.
With regards to amplification, a smaller box will need more power to hit Xmax than a larger box. Given a big box, you could probably get away with 50w/ch. In a small box, you might need 500w per driver to reach the same excursion. Of course, the voice coil will be less happy with 500w peaks. ie, bigger box = lower distortion.
Chris
You'll need a lot of EQ (or a steep low-pass filter) to get these to run below 40Hz. What do you have in the way of crossovers/EQ?
I'd say they're worth the cost of a cheap pre-made car sub box. Throw them in (I'd still recommend isobaric) and see what you get. Minimum effort, probably cheaper than you can build yourself.
With regards to amplification, a smaller box will need more power to hit Xmax than a larger box. Given a big box, you could probably get away with 50w/ch. In a small box, you might need 500w per driver to reach the same excursion. Of course, the voice coil will be less happy with 500w peaks. ie, bigger box = lower distortion.
Chris
Hmmm... thanks Chris. Appreciate that. Thinking I might leave them be and use them one day for OB. Sounds like square peg, round hole problem. I kind of guessed.
So, I might be able to source two Seas 25f-ew drivers for a good price. I've modelled them as an isobaric pair in a kind of 90l TL tube with small port. Aiming for 25hz low-mid spl.
Anything that I've missed here? Or could these ancient and tatty drivers going to find a new life?
Anything that I've missed here? Or could these ancient and tatty drivers going to find a new life?
Attachments
To be honest, simulating as an IB in HR looks like it's everything you need. There is a large difference between 40 Hz from your mains or from a dedicated sub. Plus if you give them just a few Watts a piece, you'll probably get away with letting them do 30 Hz as well.
Are you referring to the alphas as open baffle? I agree that a good 30hz is better than a pushed 30!
I think ob/ib is going to end up too big physically for our living room.
Folding them together takes less floor space, so am now getting into the w frame idea. need to do some more reading to work out if a more directional use is possible with these drivers.
Certainly do-able to have a one seat sweet spot.
If you consider having a low frequency cutoff of about 30Hz low enough then I can recommend used them in an M-frame subwoofer. I built such a thing using two Alpha 15A woofers per side a couple of years ago and it was great. It will need a bunch of EQ to remove the resonance peak around 250Hz and flatten the response, but with two of those drivers in parallel it can work well and produces some satisfying SPL. I still have them in my basement.
Pictured here, the white things on the floor:
https://techtalk.parts-express.com/filedata/fetch?id=1421209&d=1568144365
Awesome! Thats great to hear its possible. Do you have a thread about that build? It looks fairly obvious.
As my room has a small listening area, the idea of focusing the sweet spot and lowering fs sounds good. Ripole open backed.
I think this is the best idea. These are OB woofers at heart (If you have an empty room or garage behind the listening space they can work IB). Just respect the Xmech.
Another possible variation is to do what amounts to a slot loaded OB where the drivers face into a single slot plenum (back to front for best distortion) firing forward.
Would have to consider slot depth in crossover frequency.
Yes mashaffer, I totally agree, I like your slot loaded idea the best, for space ergonomics.
Would modelling this on hornresp would be a case of adding the surface area together as an OB? Including the sides?
Would I add a base and top to this creating an open box frame?
And finally, how would I determine the width and depth of the slot?
I'll happily take a link to another article that answers these questions!
Would modelling this on hornresp would be a case of adding the surface area together as an OB? Including the sides?
Would I add a base and top to this creating an open box frame?
And finally, how would I determine the width and depth of the slot?
I'll happily take a link to another article that answers these questions!
