My DIY sonotube sub is done. Pic and impressions inside.

[Nichol1997]

Which fan did you use in the fan mod?
Please.

thanks
mike

There are two ways to reduce the fan noise:
a) install a resistor to slow the fan speed down which shown in this thread https://www.htguide.com/forum/showth...ht=panaflo+fan

b) install a different fan that is designed to be quiet which is also shown in the same thread as above (see post #26 from Dennis H).

I chose b and replaced the fan with
Panaflo FBA08A24L1A, 24V, 80x25.5, 21dB
Digikey P/N P9739-ND, $8.25

---k---
They might look small in the picture but believe me they are huge. They dominate the room visually and acoustically. They sound awesome and definitely worth the work. My wife always freaks out when I turn them up because you can hear the walls buckling and feel the floors vibrating.

[---k---]

---k---
They might look small in the picture but believe me they are huge. They dominate the room visually and acoustically. They sound awesome and definitely worth the work. My wife always freaks out when I turn them up because you can hear the walls buckling and feel the floors vibrating.

hehehehe
Why don't women understand how fun that is?

[chasw98]

For the same reason that they don't buy muscle cars!

[ssabripo]

I'm still not totally committed to the tuning point of these towers, as I'm still debating if the drop in headroom (albeit slight) in the 20-30hz region is worth the gain between 8-12hz. Given my listening habits, and the fact that I will have two of them, I'm leaning towards a 11.4hz tune, although 12.4 is also in the running.

here are the theoretical numbers, with the 800W/ch of the Crown K2:

Fb------(10hz)------(20hz)------(30hz)
13.4--- 107.3 ----- 117.1 ------ 118.0 dB
12.4--- 108.9 ----- 116.4 ------ 117.7 dB
11.4--- 110.0 ----- 115.8 ------ 117.4 dB

the cross over point is around 12.3 hz, which comes in at around 113.2 dB. Above 30hz, they are pretty much a wash.

another point of consideration is that the lower tune pushes the cone Displacement further down as it approaches Xmax. The only real negative I see with going lower and lower, is that I will be closer to Xmax before tuning freq. Example, with an 11.4hz tuning point, we will approach 24.2mm at 16.6hz, whereas with a 12.4hz we will approach 23.2mm at 18.5hz.

Image not available

thus, safety first tells me to lean towards 12.4 to get some of the headroom back (compared to 13.4) for the 20-30hz region, but there are a lot of pros in going lower to 11.4hz, specially with 2 of them! I mean, we are talking 116.4 dB at 20hz for one, so a nice +3dB on the second one, and this ain't too shabby!

[ThomasW]

These are anechoic sims not in-room response. So don't get all fixated splitting hairs between 11.4Hz and 12.4Hz. Without test instruments you won't know which tuning is which once these are placed in a room.

[ssabripo]

tis true Thomas, but they give you a slight look into what you "give up" and what you "gain" generally, no?

I agree, this is splitting hairs at this point...my room is pretty acoustically challenged though, and there is very little room gain, so I wanna make sure I get the most out of it.

[ThomasW]

It takes substancial differences in tuning for there to be audible differences in performance with EBS designs.

Unfortunately 'whitepapers' and posts splitting hairs regarding relatively small differences in subsonic port tuning, have misinformed as to the performance of these tunings.

The characteristics of the room and room placment will have far more impact on the performance than a difference in tuning of ~5Hz when we're talking about subsonic tunings.

[SteveCallas]

The characteristics of the room and room placement will have more of an effect than a LOT of things, not just changes in subsonic tuning. That said, the tuning difference between 20hz and 16hz on a commercial sub was picked up on and preferred by everyone in a blind test a while back. If I'm not mistaken, Sherv himself reached the same conclusion with the same sub, and measurements point to likely reasons. I'll agree to disagree that a 5hz shift will make a difference, but in Sherv's case, debating 11hz or 12hz isn't gonna matter.

As you touched upon Sherv, and as can be seen from the measurements of your previous subs, your room gain isn't the most potent, so I'd go with the 13.4hz tune. Better to be flat or slightly rising in the low teens than rolling off.

[ssabripo]

Yes, good point Thomas.

Steve, if you recall with the current AV15 sub, placing the sub at the right of the room (current position) gave poor room gain, but flatter response....pretty perplexing, but it is what it is. Moving it to the opposite side (where the SVS used to be) gave more room gain, but it was audibly worst.... we can check my build thread for details.

since there is some rolloff at 11hz, and 12.4 is still flat, i'll probably stick with that. Plus, 30" is more manageable than 38" ports...heheheh.

[ThomasW]

That said, the tuning difference between 20hz and 16hz on a commercial sub was picked up on and preferred by everyone in a blind test a while back.

We're talking about ~5Hz variances in true subsonic tunings. As a result anecdotal information regarding tunings in the audible range is irrelevant to the discussion.

[SteveCallas]

Sherv, your graphs don't show up anymore - at least for me. If we were to hypothetically assume no gain below 25hz, I'd actually shoot for a 15-16hz tune. The lower tuned designs assume there will be gain, roughly 4-6db/octave below ~25hz. If I recall your measurements correctly, and I'm not sure I do, I think you had a slight rolloff from ~25hz on down, no?

[ssabripo]

We're talking about ~5Hz variances in true subsonic tunings. As a result anecdotal information regarding tunings in the audible range is irrelevant to the discussion.

indeed....i agree wholeheartedly.

Sherv, your graphs don't show up anymore - at least for me. If we were to hypothetically assume no gain below 25hz, I'd actually shoot for a 15-16hz tune. The lower tuned designs assume there will be gain, roughly 4-6db/octave below ~25hz. If I recall your measurements correctly, and I'm not sure I do, I think you had a slight rolloff from ~25hz on down, no?

hmmm....not sure what happened...looks like the pichost site crapped my pics ...I gotta get that fixed.

as mentioned, the left side provides more gain, and there is rolloff starting at around 14hz. The right side has rolloff at around 18hz.

[SteveCallas]

as mentioned, the left side provides more gain, and there is rolloff starting at around 14hz. The right side has rolloff at around 18hz

Where will these new subs be placed?

[ssabripo]

Where will these new subs be placed?

on the left side....the right side is where the only windows into that room are, and I can't block them. One will be corner placed, the other to the left of the coach against the wall.

[WillyD]

Sherv, I'll echo what I said on AVS since it is down right now: headroom in the 20-30hz region with these two badboys in your room should be the last thing you worry about.

Don't fret so much about choosing an Fb. I'd probably go for the lower one though.

[chasw98]

Where will these new subs be placed?

Eventually at my house when his wife kicks him and his subs out the door!

[SteveCallas]

Eventually at my house when his wife kicks him and his subs out the door!

Might as well, you're building them anyway :B Just kidding, just kidding. Hmm, I wonder if in the end Sherv will have taken more abuse from his wife or from us......ehh, who am I kidding, when talking about her expected reaction, he said:

keep the wife from cutting my nutsack off

To followup, I have to echo what Jon said:

I'm really enjoying this

[ssabripo]

another couple of hours of work done.....routed the outer edges, and glued the four pieces together! Tomorrow hopefully we cut the driver and port holes, and then we can start sanding and preparing the pieces for painting.

routing the pieces:

Image not available

As Chuckster would say, Man was made to work with electricity... Sawdust? What sawdust???! router spits it out, vacuum sucks it in. College pays
dividends, LMAO!

Image not available

Two of the pieces done....all four completed however:

Image not available

anyways....more to come tomorrow.

[---k---]

How come I only see Chuck doing work in your pictures. I sure hope you're paing him well.

[ThomasW]

How come I only see Chuck doing work in your pictures. I sure hope you're paying him well.

I was wondering the same thing..... :B

[chasw98]

Ummmm, me too!

PS - Thomas, how do you like my version of the "woodpecker"?

[ThomasW]

Does it share the table with the radial arm saw?

[ssabripo]

How come I only see Chuck doing work in your pictures. I sure hope you're paing him well.

someone's gotta take the pics you tool! :W

dont' worry...I do some work. Chuck's a bit touchy with his equipment so he does a most of the actual cutting/routing/etc...I just do the brute force stuff :lol: He doesn't want some honduran al-qaeda looking dude chopping off a finger in his garage :rofl:

[chasw98]

Does it share the table with the radial arm saw?

Sure does! Just swing the radial out of the way unless needed. A table saw does most of the work but the radial is real handy for some cuts.

[chasw98]

someone's gotta take the pics you tool! :W

dont' worry...I do some work. Chuck's a bit touchy with his equipment so he does a most of the actual cutting/routing/etc...I just do the brute force stuff :lol: He doesn't want some honduran al-qaeda looking dude chopping off a finger in his garage :rofl:

I let him sand & paint. :T :B

[steve nn]

I let him sand & paint. :T :B

There's certain things a guy needs to get down before he's ready to move on you know. :P

I'll agree to disagree that a 5hz shift will make a difference, but in Sherv's case, debating 11hz or 12hz isn't gonna matter.

I think something most to all of us LLT'ers have found, is that whatever tune we're shooting for, we seem to come in a little lower when it's all said and done. Not a bad thing and maybe not even worth considering, but still something to possibly consider?

[Nichol1997]

ssabripo,

How many router bits did you go through? Was it a 1/2" bit or a 1/4" bit that you used? I tried using the 1/4" Porter Cable bit but must have broke at least 4 of them before I was done; I made several passes but that didn't help. So near the end of all the cutting I was using a 1/2" bit but man did that ever create a lot of dust.

[---k---]

There's certain things a guy needs to get down before he's ready to move on you know. :P

I think something most to all of us LLT'ers have found, is that whatever tune we're shooting for, we seem to come in a little lower when it's all said and done. Not a bad thing and maybe not even worth considering, but still something to possibly consider?

I think it is because Steve normally ignores the extra length of the port flare. I think Thomas once said port length is from out to out.

[ssabripo]

ssabripo,

How many router bits did you go through? Was it a 1/2" bit or a 1/4" bit that you used? I tried using the 1/4" Porter Cable bit but must have broke at least 4 of them before I was done; I made several passes but that didn't help. So near the end of all the cutting I was using a 1/2" bit but man did that ever create a lot of dust.

I've gone through two bits to cutout the circles out of the mdf sheets...they were the #5146 spiral upcut router bit from MLCSwoodworking.com

[chasw98]

I've gone through two bits to cutout the circles out of the mdf sheets...they were the #5146 spiral upcut router bit from MLCSwoodworking.com

In reality, "we" have not gone through 2 bits. I asked sherv to buy 3 1/4" upcut spiral bits. I used one for a lot of cuts until I felt it getting dull. MDF will do that to a cutting edge. I then changed to a brand new bit and could run the material through it a lot faster. If I wanted to, I could probably do the whole project on one bit. But you have to remember we are building 2 at a time so that is twice the material and these are not your usual sonotubes. They are very large so the amount of cutting to be done is much greater. The time we have to spend building these is also limited and if we purchased one bit and it broke, that would set the project back for 2 weeks. Besides I was spending his money, so I told him to get three! :T

PS - I have run large CNC machines before and know my feeds and speeds so I break very few bits anymore.

Chuck

[---k---]

I bought a spiral upcut from MCLS and it never seemed to really cut well, and I ended up breaking it. (I was typically doing three 1/4" passes in 3/4" BB ply.) I went to Lowes, and based on my experience, bought 2 Bosch upcut bits. It cut 10x better then the MLCS bit. I cut 2x as much with the Bosch and the second one I bought is still in the box.

It was probably me, because I've been happy with the MLCS 30-peice router bit set, and the 3/4 and 1 1/4" round over bits I've purchased. And if I need any more shaping bits, I'll probably go back to MLCS.

So, try the Bosch from Lowes or HD. ~$18/ea.

[chasw98]

So, try the Bosch from Lowes or HD. ~$18/ea.

Personally, I like the Freud bits.

[ssabripo]

Yes, I agree...."we" went thru the first bit rather quickly I suppose ops: But Chuckster got more experience with this than I, so he prolly has a good idea on what is good for the price.

I've always used Bosch when dicking with routers when I did the car subs, so they were good enough for sure.

[Nichol1997]

I took some measurements at the listening position today with a digital Radio Shack meter and some other digital meter that my brother had (CEM brand). I don't think that the CEM was a professional meter or anything. The response looks good besides a dip at 45 Hertz. My test cd had 1 Hertz increments from 10 to 98 Hertz. It looks like I might need an equalizer. Although, has anyone heard of other ported enclosures having an effect on the frequency response? What I mean is, I have a pair of ported 15" woofers in the same room that were turned off, do you think these could be adversely affecting my response?

[Nichol1997]

I took some measurements at the listening position today with a digital Radio Shack meter and some other digital meter that my brother had (CEM brand). I don't think that the CEM was a professional meter or anything. The response looks good besides a dip at 45 Hertz. My test cd had 1 Hertz increments from 10 to 98 Hertz. It looks like I might need an equalizer. Although, has anyone heard of other ported enclosures having an effect on the frequency response? What I mean is, I have a pair of ported 15" woofers in the same room that were turned off, do you think these could be adversely affecting my response?

By the way, I have not added any correction factors to the measurements.

[warnerwh]

If you short the two subs and stuff the ports that will probably help. Be sure to disconnect any amp connected to them. Your frequency response doesn't look too bad at all.

An equalizer like the Behringer DEQ 2496 is a wonderful tool. Well worth every penny in sound quality improvement. There are two equalizers, one is a stereo 31 band equalizer and the other a stereo 10 band parametric equalizer. This thing has alot of other functions. Check it out at their website.

If you buy one get the ECM 8000 microphone and you will also have an accurate way to measure, easier too. You can get these with the mike for about 300 online at places like Musican's Friend or possibly locally at a pro audio shop. In my opinion everyone with walls should have an equalizer.

[ThomasW]

Although, has anyone heard of other ported enclosures having an effect on the frequency response? What I mean is, I have a pair of ported 15" woofers in the same room that were turned off, do you think these could be adversely affecting my response?

The drivers could move inward if the room was sufficently pressurized. Wouldn't have much impact on the in-room performance even if it did occur.

[ssabripo]

ok fellas...today was very fruitful day for us. Despite a bad neck, no sleep last nite due to my son's food poison, and general delays, i managed to make it at chuck's house today and we knocked out a lot of work, in addition to seeing ol' chuck's new addition to the family (we will get to that shortly)

anyways, here are some updated info for you guys:


Finished cutting the port holes, the ports themselves (30" for a tune of 12.5 hz), and put it in place:

Image not available

Routed the Driver holes, and dry-fitted the driver itself...Snug fit let me tell you!! Oh, and for those who have never worked with MDF, make sure you have extra router bits...you will go thru them like hot cakes:

Images not available

proud Poppa kissing his newborn twin...heheheh:

Image not available

I took a short break and got my neck medicine and such, and ol' Chuck went to attend to his new family addition, and then, I went back to putting the internal acoustic foam on the tubes. Christ, there is a LOT of square footage in a 6' x 28" sonotube!!!

Image not available

Left about 2" or so from each end to accommodate for the top/bottom plates:

Image not available

Day's work complete....the two towers are soon to be "running". So after a day of routing 2 times: port holes and and attachment of port with epoxy, round out the port flares, driver cutout and dry fitting, and acoustic foam, we were done before sunset:

Image not available

Here is what the port flares and dry fit looks like from the top:

Image not available

Work resumes Tuesday, as the grunt work of sanding, painting, repeat......etc. etc. continues. I hope in a week or so, we will be done with the painting and we can start to see this thing come together.

[JonW]

Excellent photos! :T Nice progress and looks like fun. Brings a smile to my face.