Hello there! Long time listener, first time caller. 
I have a monstrous subwoofer that I call Subzilla. I built it using the EBS Alignment plans in the Adire Vented Maelstrom Applications white paper. Recently, however, the subwoofer has been "misbehaving".
By misbehaving, I mean that it's been making a soft thumping noise. For months, I actually thought it was my fiancee' being inconsiderate by stomping around upstairs while I was watching a movie. In actuality, it was my sub and I was just maligning the poor dear. (Please don't tell her I thought that! )
Anyway, I had a spare amp laying about, so I tried replacing the amp. As you may have guessed, it didn't work. My boss at work is a former audio engineer and he thinks the sound I'm hearing means that the driver is damaged and can't be repaired.
I don't want to get rid of the custom 4' tall enclosure I built. I'm hoping to find a replacement driver that I can use in the same enclosure. I'm not a speaker expert by any meanings, but I've been trying to muddle through using Box-Port Design. I enter the characteristics of my enclosure and then one-by-one I have been entering other 18" drivers that I can find until I found one that I think may be a good match.
Here is where I'd like some expert opinions.
Here is a prospective driver: Dayton Audio RSS460HO-4 18" Reference HO Subwoofer 4 ohm
The mapped out curve looks something like this:
Since this sub is primarily an LFE sub, I really don't care much above 50 hz, but I want very deep, very accurate bass from about 40 hz down. With the exception of a peak at 20hz, this graph looks good to my untrained eye.
What do you guys think? Am I barking mad? Will this work? (The two are not mutually exclusive.)
Jeff
P.S. I know this will probably be an exact fit. However, I am reasonably skilled at woodworking even though I'm not very skilled at loudspeaker design. I'm confident I can work something out to get it to fit snugly.
I have a monstrous subwoofer that I call Subzilla. I built it using the EBS Alignment plans in the Adire Vented Maelstrom Applications white paper. Recently, however, the subwoofer has been "misbehaving".
By misbehaving, I mean that it's been making a soft thumping noise. For months, I actually thought it was my fiancee' being inconsiderate by stomping around upstairs while I was watching a movie. In actuality, it was my sub and I was just maligning the poor dear. (Please don't tell her I thought that!
)Anyway, I had a spare amp laying about, so I tried replacing the amp. As you may have guessed, it didn't work. My boss at work is a former audio engineer and he thinks the sound I'm hearing means that the driver is damaged and can't be repaired.
I don't want to get rid of the custom 4' tall enclosure I built. I'm hoping to find a replacement driver that I can use in the same enclosure. I'm not a speaker expert by any meanings, but I've been trying to muddle through using Box-Port Design. I enter the characteristics of my enclosure and then one-by-one I have been entering other 18" drivers that I can find until I found one that I think may be a good match.
Here is where I'd like some expert opinions.
Here is a prospective driver: Dayton Audio RSS460HO-4 18" Reference HO Subwoofer 4 ohm
The mapped out curve looks something like this:
Since this sub is primarily an LFE sub, I really don't care much above 50 hz, but I want very deep, very accurate bass from about 40 hz down. With the exception of a peak at 20hz, this graph looks good to my untrained eye.
What do you guys think? Am I barking mad? Will this work? (The two are not mutually exclusive.)
Jeff
P.S. I know this will probably be an exact fit. However, I am reasonably skilled at woodworking even though I'm not very skilled at loudspeaker design. I'm confident I can work something out to get it to fit snugly.
not modeling, and simply looking at your graph... that predicted result is exactly the type of result that cause people to say ported boxes are "boomy"
that 6db+ hump immediately followed by that -3db low, and factor typical room gain is a recipe for "one note" disaster. i would continue your search...
that 6db+ hump immediately followed by that -3db low, and factor typical room gain is a recipe for "one note" disaster. i would continue your search...
I didn't even know that was a thing.
Will reconing it preserve the T/S parameters, etc.?
Jeff
looked at your sim a little closer, might want to change that in^3 to ft^3
the sim will look a whole lot better.
this is a very good idea for that driver, it sounds cliche', but they just dont make them like that anymore.
looked at your sim a little closer, might want to change that in^3 to ft^3
the sim will look a whole lot better.
Um .... I knew that. Yeah, sure ....
How much would such cost me, and where would I find someone or someones who can do that?
Jeff
Actually, oddly enough, the simulation doesn't change when I check the dual ports. The only thing that happens is that the alignment profile changes the port length from 4.10" to 11.60". If memory serves, the ports in the plan are 17" long. I don't know enough about speaker mechanics to know how big a difference that will have on the total response.
Jeff
Jeff
The discrepancy in the port length that the sim is calculating compared to the Adire plans could be that Adire included total losses in their design. The only way to know for sure is to mount the driver in the enclosure and check what the tuning really is. Hope this makes sense. I am not good with words. But it makes sense in my head.
Matt
Matt
Losses mean less bass and a necessitate a bigger box and/or higher tuning, which would mean shorter, not longer, ports. Measuring actual Fb is a good idea.
Attached is an image showing how your options look at 2.83V input: SPL1 is your Maelstrom, SPL2 is the Dayton, and SPL3 is the (imo foolish) suggestion of the ultimax18. The ultimax is about 8dB less sensitive than the Maelstrom at 100Hz.
Both of these replacement options are more akin to car woofers - VERY HEAVY cones, as are the others recommended by the same user that recommended the ultimax....
To the original poster, that Dayton is not a terrible match other than a fair drop in sensitivity, but I think you would be better off trying to get the woofer repaired - it may not even need a recone. It may just need some glue in the right places if all you are hearing is a thump every now and then. T/S will generally be unaffected by a repair, but for a recone it depends on what is done and how close the new cone/suspension are to the original. Vas will be harder to match, but if mass is similar, response won't change much.
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Ok, so repair is the best option --- if available, and failing that, the Dayton 'twill serve, though it may need more power to get as loud? I think I have some bridgeable Marantz monoblocks laying about, so maybe they'll do the trick.
Thanks very much for running the simulation for me. What application did you use?
Jeff
Self-written spreadsheet. Done using published parameters and your 320liter box - tuning adjusted to 17.5 Hz as a guesstimate.
Try running your own sims using something like Unibox if you want a comparison.
I poked around a bit looking for a comparable woofer and it is difficult to find an 18" with much more than 8mm excursion. If you can settle for that, there are a few more options. This one ( Dayton Audio DCS450-4 18" Classic Subwoofer 4 Ohm ) models quite similar, but I haven't used it so I can't say it will suit your purpose. I don't know how much power you are using, etc...
I would get the one you fancy, seems you have plenty of ampage lying around.
The room and sub placement is an equally important box to concider.
I think your simulated graph looks fine, and can always play around with port length and box stuffings abit. Supprisingly many woofers in that box placed in the same location would not sound massively different. Yes the driver matching the box well improves things..
Guess my point here mainly being how much rooms effect. Wish there was a program to calculate both boxes... Room and sub
. But then would have to factor in various losses and factors of different wall floor ceiling atributes at different frequencys..
Would be a awsome program though. Factering box within box placement, showing peeks n nulls in room, could even get it to calculate rugs n objects into its equazion.
The room and sub placement is an equally important box to concider.
I think your simulated graph looks fine, and can always play around with port length and box stuffings abit. Supprisingly many woofers in that box placed in the same location would not sound massively different. Yes the driver matching the box well improves things..
Guess my point here mainly being how much rooms effect. Wish there was a program to calculate both boxes... Room and sub
. But then would have to factor in various losses and factors of different wall floor ceiling atributes at different frequencys..
Would be a awsome program though. Factering box within box placement, showing peeks n nulls in room, could even get it to calculate rugs n objects into its equazion.
Hi Ron
I figured out where I got mixed up. The sims and equations that are used to calculate box volume and tuning use small signals. As power increases the f3 also increases so it is possible that Adire factored this in for a flatter response at higher power levels. As you wrote the box is probably tuned to about 17hz or so not 20hz as the plans indicated.
Regards
Matt
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