what's the ultimate sub build? :)

[Paducah Home Theater]

You doing open baffle mains?

 

Nope, just plain jane sealed or ported, haven't decided yet.  Was going to have sealed everywhere but people keep saying they're awesome ported so I dunno.  Going to try to squeeze them in behind my screen partially inset into the wall.  Been modeling them, you can get away with a smaller box than you'd think, like 1.5 cubic feet and it's still not looking too awful stupid on the graph for use as mains.  

 

He's working on some open baffle kits with a compression driver and horn, I might try that.  I don't fully understand the open baffle concept so I'm not going there without a proven kit.  Just seems like magic to me, the front and back waves should cancel each other out, no?    

[CECAA850]

front and back waves should cancel each other out, no?

 

Not with the baffle

[derrickdj1]

I would not use an open baffle speaker for any HT application.  It may be OK in a 2 ch system.  No resonance from the box but, is that really a big advantage.

[Paducah Home Theater]

To me, It does not look like a null or a problem.

 

We ain't got no stinking nulls.  

 

[derrickdj1]

I can't tell your smoothing.  Carry the graph out to 200 Hz.  Also use a higher spl.  It looks like above 80 Hz the average is 62 or 63 db on the no EQ graph.  Where is the XO and what type.  Is this subs or subs and mains?  What you are calling a null registers at around 56 or 57 db.  The high point of the graph is 70 db at around 50 Hz.  Knock down the  peak at 50 Hz, Q or 6 or 7 gain -10.   How many filters are you using on the EQ graph? Give us as much info as possible.  I have had graphs that have this so called null and it was easily raised with PEQ.  Then it was not a null.

 

If 80 Hz XO is being used and the portion of the graph above it averages 62 or 63 db, that should be what you are shooting for.  But, all of this is irrelevant without more info.  Smooth the graph to 1/6 and carry it out to 200Hz.  This way we can see what is really going on better.

Edited January 13, 2016 by derrickdj1

[CECAA850]

We ain't got no stinking nulls.

 

What's that at 82 Hz then?

[muel]

...  I have had graphs that have this so called null and it was easily raised with PEQ.  Then it was not a null.

 

Do I understand correctly that if it is a null then raising the EQ would not have solved the problem (and probably made it sound worse)?  If the frequency is made louder it is only going to cancel out that much more?

[CECAA850]

Do I understand correctly that if it is a null then raising the EQ would not have solved the problem

 

That's correct.  You can bring down peaks with EQ but you can't raise a null.

[Paducah Home Theater]

 

We ain't got no stinking nulls.

 

What's that at 82 Hz then?

 

 

I just meant I was able to EQ it out.  I changed the microphone position slightly by pulling it away from the back rest, placing it straight up and down, and using the 90 degree calibration file, plus stretching the graph out more and ignoring 5 hz.  Afterwards it started looking like a valley rather than falling off a cliff.  I was able to pull down the 38 and 53 hz room peaks, as well as that 91 hz one that I wasn’t expecting.  82 just need a little bump at that point. 

 

HOWEVER, the problem I found in doing this is that MiniDSP only has negative gain, not positive.  I thought I’d pull them down to the baseline around 20 hz then bump the overall output back up.  Ha, no.  You start at zero then can pull it down from there.  My levels are too low and I cannot make it back up with the receiver’s sub level and amplifier gain.  Maybe there’s something that I’m missing but otherwise I get to start over with a different strategy with the MiniDSP’s gain, or lack thereof, in mind. 

 

Also curious about if the stuffing is affecting anything.  Seaton told me to use R-19 fiberglass and “stuff it good”, but hell that’s pretty subjective.  How much is that?  Is too much or not enough going to give erratic response?  Hate to come back and ask for details, he’d basically be giving away secrets of the F18.  

 

Still really happy with the sound from 15-20 hz, just need to figure out how to tame the peaks without screwing up other stuff.  

Edited January 13, 2016 by MetropolisLakeOutfitters

[CECAA850]

Also curious about if the stuffing is affecting anything.

 

It just makes the drivers react as if they're in a larger box.

[Paducah Home Theater]

 

Also curious about if the stuffing is affecting anything.

 

It just makes the drivers react as if they're in a larger box.

 

 

Yeah but I've always used poly-fill.  Unsure as to how tight to stuff it with fiberglass.  It seems denser than poly, not sure if stuffing too much would have the opposite effect.  He claims that's the reason the F18's are successful, that he found the perfect combination of box size vs. stuffing for the ultimax's.  

[CECAA850]

Everything I've read says poly doesn't do much and fiberglass works really well.  You just can't use fiberglass in ported applications as you'd be pumping glass particles into the air.

 

I wish I kept the link, I'd share it with you.  A car sub builder measured boxes using poly and glass.  There was no change in the poly box but a measurable change in the glass filled box.  I'll see if I can find it.

[Paducah Home Theater]

I wish I kept the link, I'd share it with you.  A car sub builder measured boxes using poly and glass.  There was no change in the poly box but a measurable change in the glass filled box.  I'll see if I can find it.

 

That's exactly what Seaton said, that everybody uses poly because they say which stuffing material you use doesn't matter, but its actually measurable.  I just don't have the time to try 10 different stuffing densities.  I have an entire 40' roll of R-19 loosely stuffed in the boxes, it takes up most of the volume.  

 

All I know is that this box has much more all-encapsulating pure bass down low rather than concussive or jackhammer'ish sounds, even at low volumes, it just sounds better.  Don't know if that's due to more drivers, or the stuffing, or box material, or that they're working as an array, or what.  If I can figure out the EQ and gain I'll be good.  

Edited January 13, 2016 by MetropolisLakeOutfitters

[Scrappydue]

Should have kept the inuke

[CECAA850]

I have an entire 40' roll of R-19 loosely stuffed in the boxes, it takes up most of the volume.

 

A rule of thumb is about a pound per cubic ft of box volume.  Never use more than a pound and a half.

[CECAA850]

Don't know if that's due to more drivers,

 

More drivers moving less makes for better sound with less distortion.  Same principle as an IB.

[Paducah Home Theater]

Should have kept the inuke

 

Probably so but I don't think its affecting anything except below 10 hz.  With single digit frequencies my limiters come on too easily, otherwise I don't miss it.  

 

What I don't understand is how REW with a calibrated UMIK-1 showed such different response than OmniMic.  With the iNuke all we did was cut 40 hz and called it good.  I doubt it's the amp, it's the same room, same location, same subs.  

Edited January 13, 2016 by MetropolisLakeOutfitters

[derrickdj1]

I just got in tonight Metro.  Tomorrow I will post a link or REW guide that one one our Chicago guys put together after our last gtg.  He works with Mark Seaton and is pretty knowledgeable on sub EQ.  I use Omnimic.

[Paducah Home Theater]

At this point I kind of think my amp is blown, maybe I screwed it up playing around too hard.  If so that may explain some of the erratic response before EQ.  It really shook the house down low at least at first, enough to get in trouble with my wife when it was a total non-issue before, but now that I'm playing rock music, it doesn't sound so hot.

 

It is distorting badly on any type of peaks, even without the clipping lights coming on, even at levels that aren't exactly full blast.  Kick drums for example sounds like my sub enclosure is made out of sheet metal.  There is this weird concussive pop rather than a low dull thud.  I have made every effort to isolate the issue.  I am running it in stereo, it happens when each side is running into one sub as well as wiring in parallel with two.  Happens with my receiver running straight into the amp as well as running through MiniDSP.  Happens at several different volume levels including pretty low.  Happens even with the sub out of the enclosure so I know its not the box or stuffing.  Happens on all four of my subs including two brand new ones and two identical ones that I've had for a year, on both of the amp channels.  Perhaps something is badly misconfigured and I'm overdriving the input, but if that were the case, seems like the clip lights should be coming on, which is exactly what Crown tech support said.  I can make it happen with only one light on the input indicator lighting up, two lights and its awful.  Plus, I ran Audessey last night and it made it worse than ever even with Audessey setting the sub out back almost -10.  It did this even at -25 on the receiver.  

 

So, I guess its getting sent back.  Don't know what else to do, spent 7 hours on it last night due to thinking it was this MiniDSP and that's the best conclusion I can come up with as it is doing this even when bypassing the dsp.  Enough is enough.  Will be swapping out to a Speakerpower ASAP.  Hopefully I'll get a new replacement amp and can immediately sell it.  

Edited January 14, 2016 by MetropolisLakeOutfitters

[CECAA850]

Did you check resistance of the speaker wires that run to the amp the make sure you're not giving it a .5 Ohm load by accident?