Ported 12.5ft^3 AV15-X project (pics)

**VERTIGGO** · **04-13-09, 10:43 PM**

Well I finally got through some of the initial trouble figuring out the BFD (I didn't realise that the IN/OUT button bypasses all of my filters!). And I threw together about 9 filters that flatten out the 20-60Hz area a bit, but I'm still wondering why it squeaks and rattles so much at the low (10-25Hz) end. According to my REW readings I'm only putting out around 80db, and my WinISD model looked like I would get 100db+ SPL. I will be using a reckhorn for subsonic, but from my measurements, I shouldn't even need it (with EP2500 cutoff at 30Hz there's a nice roll-off for safety's sake and the BFD pulls it back up at 20Hz). This is with my Xonar crossover at 60db and only measuring the mains and sub:

And one of just the NS-777s crossed at 50Hz now to see how much they can handle. Note, the SPL meter was placed closer for this one to get a better reading since it's late:

By the way, the readings from my mains are hideous in my opinion. Are these just bad speakers or is the room a felon? Should I get another BFD and try to flatten out the 777s from 60 to 200Hz?

I'm also hearing a lot of "exhaust pipe" noise at the very bottom of the measurement, I have to double check the exact freq range, but shouldn't this driver be able to handle sub 20Hz?

**VERTIGGO** · **04-14-09, 04:26 PM**

I decided to redo my entire filter bank manually (apparently REW is terrible at predicting my room's FR) and with 12 filters I came up with this:

BTW, the 12th filter is a 2.5k -30db with a bw of 60 and it eliminates (from listening area) the notorious BFD hum. I heard someone use 1k, but with my sine generator i found the center of my hum and decided on 2.5k. It's also farther from my useable freq range so it doesn't mess with my crossover as much.

Here is the same manual filter set combined with an NS-777 to show crossover. Unfortunately there's some cancellation or something at about 49Hz. It actually grew worse with a positive 49Hz filter. If I simply plug in the woofer backwards I can reverse the phase, can't I? I don't have any way (with my receiver to change the "SW distance":

**Ricci** · **04-15-09, 03:40 PM**

Not to nitpick you , but can you raise up the resolution scale on your graphs? You are using a 105db range so it's hard to tell what's going on when there's 15db range for each hash marker. Try 45db -105db instead of 0db-105db and cut the graph off at 200hz on the high end for the sub.

**VERTIGGO** · **04-15-09, 11:12 PM**

No thanks for the tip! Here is my sub in it's current state of BFDery:

And the NS-777 mains:

And mixed:

NOTE: Crossover is at 50Hz so the mains will get more LF than they usually want, and the BFD keeps the sub from rolling off too low.

I'm kind of annoyed that combining the mains and sub generates so many drop-outs, but I guess I have to live with it when my room isn't treated or anything. I did try adding more filters to fill the gaps, but REW is slightly off when it comes to showing the filters' effects, and i can't seem to get it much smoother than it is. Does it look terrible?

**Wayne A. Pflughaupt** · **04-24-09, 05:47 PM**

Quote:

And I threw together about 9 filters that flatten out the 20-60Hz area a bit...

I decided to redo my entire filter bank manually (apparently REW is terrible at predicting my room's FR) and with 12 filters I came up with this...

Here is the same manual filter set combined with an NS-777 to show crossover. Unfortunately there's some cancellation or something at about 49Hz. It actually grew worse with a positive 49Hz filter.

I'm kind of annoyed that combining the mains and sub generates so many drop-outs, but I guess I have to live with it when my room isn't treated or anything. I did try adding more filters to fill the gaps...

There seems to be some confusion here as to the purpose of the parametric equalizer. The goal isn’t to achieve a response graph that looks like a dead man’s EKG. The equalizer is merely supposed to smooth response and eliminate any substantial peaks and valleys (assuming the latter aren’t caused by nulls). There’s no way that should take more than 3-4 filters as low as your crossover is set - if that. You might want to take a look at the article in my signature on minimal EQ.

Re the peaks and dips that appear when you add the mains, you can’t “fill in gaps” in the 80-100 Hz range with the equalizer if your crossover is set at 60 Hz, especially since the mains are a contributing factor at that point.

I’m surprised that response with a sub that big and a driver that substantial is dead below 20 Hz. Do you have it in a good corner with no nearby openings in the walls?

Regards,
Wayne

**VERTIGGO** · **04-24-09, 11:34 PM**

I'm starting to understand that the valleys above 80Hz are not the issue. I also have the sub in a corner, though it's not driving into the corner and the room is decently large with some openings to the rear.

However, I think the discrepancy is that the measurements were taken with the 30Hz HPF in place and incidentally, it took very little to round out the curve into the 19Hz region, which is most likely the room gain. I need to run some more tests with the loop-back to see exactly what I'm sending the sub, since both methods produce decent response down to the tune freq, but I only see serious action below that when it sounds like it's bottoming. Should I turn the box around so the sub is pushing into the corner?

**Mike P.** · **04-25-09, 12:30 AM**

Do you have the Reckhorn B1?

**VERTIGGO** · **04-25-09, 01:35 AM**

yes im using the B1 now, but it seems to let a lot more LF through than the EP2500 30Hz filter, so im not sure what's better, since the room fills out the 19-30 anyway.

**VERTIGGO** · **04-27-09, 08:59 PM**

I just double checked my subwoofer tune with a resistor and DMM (it is 17.5Hz), Then set up a loopback just using the B1, and mapped how it affects the signal. Note: my Sony receiver has an inherent peak below 20Hz, so these aren't perfect. From left to right, 10Hz HPF, knob at about 1:00, and knob at about 3:00

I finally settled on roughly the middle one with a maximum boost at 20Hz which gives me a fairly level signal from 20Hz to 50Hz.

I was just surprised that the B1 subsonic filter is so gradual. However, it is a must when the safety of the driver is at stake.

**Fabricator** · **05-31-09, 04:13 PM**

so. how is it working out ?

**VERTIGGO** · **06-05-09, 02:13 PM**

Quote:

Fabricator wrote:

so. how is it working out ?

I have the driver out, and I'm finishing the box. I've concluded that I should focus on smooth power above 20Hz with this build, which it can produce easily, and I have my Reckhorn B1 cutting subsonic fairly high (something like the middle graph above), but with some EQ and room gain the response is still great above tune. I noticed while blasting some "No Leaf Clover" and Daft Punk stuff that the sub was getting into the danger zone at subsonic frequencies. With the subsonic filter at a higher starting point, I can still get major output in the audible range. Although it is more than enough for my small home theater, I would classify this build as "musical".

I'll try and get more pics and graphs once the finish is complete.

**SteveCallas** · **06-06-09, 01:07 PM**

Why such a low crossover (50hz?) I'd give the sub a little more room to play and up the crossover to 80hz. Let the 8" drivers in your speakers focus only on higher frequency bass.

**VERTIGGO** · **06-07-09, 02:22 AM**

I'm actually using 80Hz on all channels now that I have the Onkyo receiver. I was using 50Hz for the mains because they drop off sharply anyway, and the sub was still pushing up to 80, but I have it fixed now. The Audyssey wizard decided I should cross my NS-333s at 50Hz and the give the mains everything, but I'm overriding that with a THX crossover across the board. I have to say though, adding the large center and then upgrading to the same (NS-777) as the mains was like night and day. The soundstage is brilliant in movies as well as music. For the price these Yammies are going at (~$170), I'd recommend 3 to anyone.

Here I've laminated 23/32 maple ply around the box and am sanding the wood filler:

**Fabricator** · **06-07-09, 10:19 AM**

perhaps i missed it. but, what are you putting on them ? i am at the same point as you. i had wanted veneer. but changed over to just painting them semi-gloss black.

**VERTIGGO** · **06-07-09, 01:36 PM**

I have some black spray furniture lacquer, and with a water base grain filler underneath, it should make a nice finish.

**SteveCallas** · **06-07-09, 03:04 PM**

Nice to have another three tower LCR member around these parts

**Fabricator** · **06-07-09, 08:20 PM**

Quote:

VERTIGGO wrote:

I have some black spray furniture lacquer, and with a water base grain filler underneath, it should make a nice finish.

i am painting my subs right now. i used DAP wood filler. that stuff is sucking up my paint like a sponge. make SURE you prime first. i did prime, but some got sanded off. i WISH i had reprimed the spots. ymmv

**VERTIGGO** · **06-07-09, 11:38 PM**

the grain filler i have is actually a paint, and dries a little chalky, but when sanded is a perfect surface. I used a different filler for the screws and cracks previously.

Quote:

SteveCallas wrote:

Nice to have another three tower LCR member around these parts

YES! I think your thread was one of my inspirations. I will never go back. I'm actually looking into Center Stage XD from Seymore AV (acoustic transparent screen), which is a weave as opposed to punched vinyl. I got some samples, and it is slightly dimmer than my current screen, but I believe it will be worth it to have the three towers evenly spaced behind setup behind the picture.

**VERTIGGO** · **06-08-09, 05:07 PM**

2 coats of generic black for undercoat (plz excuse the dirty lens):

**Fabricator** · **06-08-09, 09:35 PM**

lookin good.

**VERTIGGO** · **06-10-09, 11:34 AM**

I'm actually having a real hard time getting the furniture lacquer to shine or even lay in an even coat... still looking at various finish recommendations.

EDIT: My problem was that I accidentally put a gloss enamel on one side and it didn't dry as fast as the lacquer, so I've had to let it cure for a few more days, sand, and go back to lacquer on top. I'm drying my last black layer now, and I'll soon rub it and begin clear coats.

**VERTIGGO** · **06-20-09, 01:29 AM**

I'm finally assembled again. The lacquer finish leaves something to be desired in my mind, but I'm at least going to let it cure for a long time before rubbing and maybe misting it some more with clear coat to get the right texture. Currently I can pick out hazy and glossy areas due to spraying too closely. It is my first paint job though. The most important thing to me is that it sort of blends into my HT system if not completely matching.

**Fabricator** · **06-20-09, 08:05 AM**

looks good. that is how i wanted mine to look (2 ports), but i was told to use a slot. if i ever do my 15" build, it will look just like yours (basicly).

my finish didn't turn out good at all, just good enough. but i have found, that with my setup and lighting, i don't much notice the flaws. so, its on to the next project.

do any testing of it ? what did it do at 20hz ?

**Fabricator** · **06-20-09, 08:08 AM**

oh. i have heard that if you use acoustical books, your speakers will sound better

**VERTIGGO** · **06-20-09, 07:59 PM**

I am currently using the Reckhorn with a slightly high subsonic cutoff and the signal looks like this (loop-back):

I have been using manual filters on the BFD adjusted by ear, so those and the room gain makes up for what looks like an overly shallow roll-off. However, it also reduces the subsonic signal at 15Hz and below more than without it which is really what made the sub bottom out most often.

Quote:

Fabricator wrote:

oh. i have heard that if you use acoustical books, your speakers will sound better

I can't afford acoustical books, but half of an encyclopedia helps a little with the annoying (but comfy) couch that blocks some sound

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