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Discussion Starter #1
I've been reading and reading and modeling and modeling now for the past couple of weeks and have things narrowed down greatly. Mike has suggested a pair of Mach5 IXL 18 2.2s when they are back in stock and I've been figuring out WinISD as best as I can (still lots to learn but fairly confident now).

My question at the moment should be fairly easy: do I need a SSF for these subs for a tuning of 15Hz when my amp has a built in SSF of 10 Hz? That leaves me with the 10-15 Hz frequencies putting me over x-max. Is there enough soundtrack audio out there to warrant the hundred bucks or so? FYI they'll be receiving 750W each.

Thanks for your help in advance,

John Glowa
 

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I am not an experienced pro here, but I don't think so.

I did need one, but my amp does not filter at 10 hz and I am pushing 2500 watts into a single MJ18m tuned to 18 Hz or so. :dumbcrazy:
 

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The IXL-18 in 12.5 cu ft. tuned to 15 hz with 750 watts input will exceed Xmax at 13 hz. The question is how often will you push the sub to that limit. If you find that the sub is bottoming out frequently, you can add a out board SSF unit. If it's not bottoming out, no need to get one. Build the subs and try them out first. No sense buying anything until it's determined that you need to.
 

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Discussion Starter #4
2,500W into one MJ18M??? Correct me if I'm wrong but isn't that roughly 3-1/2 times RMS on one of those? It's only been hooked up for a day right...

SSF question. I was hoping folks would say so and that I wouldn't (a majority of them at least). I'm the type of person that has to plan everything out before I start dumping cash into it. I just checked again and xmax really isn't over until 14 Hz or so so I'm talking a range of 4Hz here..
 

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Discussion Starter #5
Mike,

What size and length port are you modeling on the 12.5 cubic box at 15Hz? I seem to get a better result with port length and air velocity at 13 cubic feet?
There must be a good set of plans for this popular build out there is someone is willing to share!
BTW Mike - Decided to just build 2 seperate boxes with the idea that someday I might want to remove them. The riser idea is a "destroy it or leave it" type of item.
 

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Discussion Starter #7
Hmmm... I think I was looking at ft/s now that I think about it. Whoops.
Would 24 m/s make it a decent candidate for flares or donuts? Or would you really bother with either one at that velocity?
Thanks!
John
 

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2,500W into one MJ18M??? Correct me if I'm wrong but isn't that roughly 3-1/2 times RMS on one of those? It's only been hooked up for a day right...
Let's just say I am very impressed with the power handling capabilities of the MJ18m. I have been up for a month or so now. I am waiting for it to show signs of 'breaking in" or "loosening up" and I will turn it down a bit. I have a Tapco J2500, connected bridged mono into 4 ohms. The filter and clip limiter are off. The volume knob is set at 3 oclock, approximately 3/4's power. Everything is set to bass boost, the receiver tone controls and the Reckhorn B1 bass control. I have the subsonic frequency slope set at 16 or 18.

So I have exaggerated my power feed by 25% or so? I do believe I am supplying way over the published rating and have tried to describe the safety factors I am using so far. I would love to be playing with a pair of IXL 18 subs like you are talking about. :hsd:
 

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Discussion Starter #10
Those are very impressive numbers then just the same! Do you think that you've sent a signal for long enough at those power ratings to fully "test" it? You're making me rethink the extra couple of hundred on the IXLs...
 

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Do you think that you've sent a signal for long enough at those power ratings to fully "test" it? You're making me rethink the extra couple of hundred on the IXLs...
Well those are home theater numbers. Sometimes the lows peak for only a short time. I did watch all of the Star Trek movies recently. The early ones have a lot of LFE. I was right beside the volume knob to cut it down, if need be. I watched War of the Worlds at one notch below 3/4's. I watched Serenity, Master and Commander, Sky Captain, and lots more. I am still nervous in case it "loosens up", and gets physically easier to drive to Xmax. In a way, that is what I have been expecting.

If I was not on a tight budget I would have ordered the IXL's. They have a cast aluminum frame like all the top offerings, have a greater Xmax, and a higher power rating. I am just very happy the MJ18 "can approach" that performance. I don't have anything to compare them to, subwoofer wise.

I am sure Mark at Mach 5 audio would be able to guide you with that question. Sonny, Mike P, and lots of other guys have the IXL's for a reason, they must be better.

Please note: I have no idea how much real power I am putting out. It is hard to get an input signal high enough to drive these pro sound amps. My input signal is adequate to run it in the sweet spot, but is by no means near the max, which is where they get their published power numbers. Hope this helps.
 

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I'm kind of in a similar boat. I'm looking at building a IB sub using a Dayton RSS390HF-4. It's XMAX is little limited but with a payoff in accuracy. The IB enclosure wont provide any limiting for the excursion either. I'm kind of balancing that the Driver is $159 bucks and do I really need a $100 SSF to save it?

So here is my poor mans SSF:

So what I'm was really doing was I was shopping for a 12" sub. Decided to go with th 15" variant which has the same XMAX but adds 100W power handling. This was only $20 more than the 12". Because the Sd is 829 cm squared for the 15" compared to 515 cm squared for the 12", for the same
SBL output I can be farther away from XMAX.

So then I'm just going to drive it using the BASH AMP that I was planning to use with the 12". The output clipping limiter will keep me from sending distorted signals to it and I'll be under driving a little. If I want to upgrade later I can replace the amp and add the SSF, but for $20 I thought this was a good approach.

Kyle
 

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Discussion Starter #13
Bluejay,

That's kinda what I was figuring - not getting a terribly strong signal combined with moderated levels at the amp controls. I have a pretty decent amp, similar to that tapcon although in 4ohm stereo I can only get 750 to each driver. With the "teeny" sub I have now to test the amp, I really think that my signal isn't the strongest. It's a 10 inch JBL and although I can thrash it pretty hard (and I frankly don't care if it spits out its guts all over the floor!) I thought that it would do it at a lower control level. I am seriously considering the SSF right now, one: to eliminate any concerns about ss freqs, and two: to perhaps give me some signal gain (?).
Anyone know of a rack mount SSF that won't break the bank? Perhaps I should ask that in a new thread...
 

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Discussion Starter #14
Kyle,

I'm not quite sure how your approach addresses a SSF? I think what you're doing is extending xmax by going with a larger driver but that doesn't neccesarily aleviate the excursion issue does it? I could do, I suppose most anyone could, by building a box with a low enough tuning point (10Hz in my case) to match the signal that my amp will pass. I think that would solve that problem but my output would be hindered pretty drastically.
I'll see what the rack type SSFs will run me - and although I probably won't "need" one, I'd like to have one to play with now and in the future.
John
 

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Discussion Starter #15
Bluejay,

I checked out that 12 cf box you posted. Do find that there is a bit of box flex or vibration in that design? Did you add more bracing inside? How do you like the plywood?
Just curious.
John
 

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Kyle,

I'm not quite sure how your approach addresses a SSF? I think what you're doing is extending xmax by going with a larger driver but that doesn't neccesarily aleviate the excursion issue does it? I could do, I suppose most anyone could, by building a box with a low enough tuning point (10Hz in my case) to match the signal that my amp will pass. I think that would solve that problem but my output would be hindered pretty drastically.
I'll see what the rack type SSFs will run me - and although I probably won't "need" one, I'd like to have one to play with now and in the future.
John
It doesn't address it directly. But I get protection due to that fact that I theoretically am farthur from driving to xmax. So the underlying assumption here is that I equalize my system for a balance between bass and the higher frequencies. IF the 12" design does that AND has a small risk of over extending, then the risk is reduced by increasing the size of the woofer.

Here's an example. If I am running at 300W on a specific piece of music or HT and the excursion is at XMAX on the 12" sub. Let's say that this sounds balanced with the other speakers and it is as loud as I would ever listen to it. If I were to swap out the 12" sub with the 15" sub and replay that sequence, then since the efficiency of both subs is pretty much the same, then I will generate the same amount of SBL's with that wattage. But the important point here is I wont be at XMAX on the 15" sub.

It's basic physics. Since the surface area of the 15" is much larger than the 12" (actually 38% bigger) then for the same SBL, the cone by definition will be excurding less. That gives me extra padding for those instances where the sound piece has more umph than I had planned.

It is not a guaranteed method of never exceeding XMAX, it does reduce the risk though. And it only cost $20 more.

Kyle
 

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Kyle,

I'm not quite sure how your approach addresses a SSF? I think what you're doing is extending xmax by going with a larger driver but that doesn't neccesarily aleviate the excursion issue does it? I could do, I suppose most anyone could, by building a box with a low enough tuning point (10Hz in my case) to match the signal that my amp will pass. I think that would solve that problem but my output would be hindered pretty drastically.
I'll see what the rack type SSFs will run me - and although I probably won't "need" one, I'd like to have one to play with now and in the future.
John

Oops :whistling: one more thing. I enforce the 300W RMS max listening volume by using a 300W RMS BASH amp with the 500W RMS 15" SUB. That ensures there's more room on the 15" that I'm not tapping. That is my SSF safety padding.

Kyle
 

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I checked out that 12 cf box you posted. Do find that there is a bit of box flex or vibration in that design? Did you add more bracing inside? How do you like the plywood?
Just curious.
I really like the plywood, it is tough. I did not add any more bracing yet. I have noticed some box flex. I am getting some flex at high SPL's, at levels that have you worrying about the driver too. I braced the front panel to the back, this was absolutely necessary.

Down the road, when I get a bit of time and I am not using it, I should brace the sides together and probably the top and bottom. The work will probably end up as 2 or 4 more braces. I will also get a chance to inspect the box and see if anything has come loose. I do not hear any rattles. The only way to consistently get the side panels flexing is to play some rap or hip hop music really loud. Then I don't really know if the sound would change, but I presume it would.

I'll see what the rack type SSFs will run me - and although I probably won't "need" one, I'd like to have one to play with now and in the future.
John
I will be interested to see what you do come up with. I bought the Reckhorn B1, which is a small metal box, not rack mount. I justified the $100 cost as $50 for sub sonic filtering plus equalization, and $50 for "connection management". It raises the input levels and takes care of some of the impedance mis match issues between sub outputs and pro sound amps. There are a few other ways, but I did not investigate them all.

I have a pretty decent amp, similar to that tapcon although in 4ohm stereo I can only get 750 to each driver.
Don't worry about that. I expect to be hooked up that way next year. My daughter wants me to build another sub so we will have 2 as well. :1eye:
 

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Kyle said:

I enforce the 300W RMS max listening volume by using a 300W RMS BASH amp with the 500W RMS 15" SUB. That ensures there's more room on the 15" that I'm not tapping. That is my SSF safety padding.
Your "theory" doesn't work. A Dayton RSS390HF-4 in an IB + 300 watts = a blown sub. A single RSS390HF-4 will exceed Xmax at 18 hz with 100 watts. 4 subs would exceed Xmax at 15 hz with 300 watts.
 

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Kyle said:



Your "theory" doesn't work. A Dayton RSS390HF-4 in an IB + 300 watts = a blown sub. A single RSS390HF-4 will exceed Xmax at 18 hz with 100 watts. 4 subs would exceed Xmax at 15 hz with 300 watts.
Thanks for running the numbers. You do you generate these? I did not understand what you meant by 4 subs. Did you mean 300 watts to 4 subs wired in parallel and series (meaning 75 Watts a piece)?


Kyle
 
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