Specific SPL data

burdette
burdette Posts: 1,194
Spoiler alert:

If you aren't a bass head or interested in someone else's bass data, then this is most likely a boring-**** thread, so move on... nothing to see here. Check out www.classorsex.com

OK Doc, so, it's you, me, maybe Gonzo and a couple of others... I'm bettin' Hbomb is still with us.. Ron-P is probably here, too. Here is some data... I'm not exactly thrilled with it.. but the point is to test and improve, so here we go as a first run.

(Sidebar to Hbomb... my wife and kids may be gone much of the summer, my wife's sister is having double hip-joint replacement and my wife is going to help during the recovery (they have 4 kids).. perhaps we'll be able to get together this summer for some fine summer evening listening, if you're interested. I have eighty bucks for you, in exchange for a package of goodies that is up to you to organize.)

Facts:
My system consists of Monitor 7Cs for mains; Monitor 5jr+ for surrounds; an Advent center that I bought from a fellow Polk-forum guy; and my DIY sub. I am currently in possession of the materials to construct a "monitor" center... which I'll get to as soon as this sub is a done deal.

Doc, I followed your specific instructions to the letter... using 75dB as the goal, my results were: LF: +3; C: 0; RF: +4; RR: +5; RL: +5; sub: +10!!!. These are quite a bit different.. QUITE a bit different than the settings I was at, using the built-in test tones and my ears. The LF speaker is nearer a corner, so that may explain the difference in settings on mains, especially given that I'm measuring lower frequencies. By ear, I had the center at -2 and the mains at 0.. curious.

I really question the settings on the surrounds. The mic is focused towards the front, my ears are to the sides.. the surrounds sounded too loud to me at a reading of 75 dB - but I followed the meter.
I had to set the sub output higher than -3 because otherwise the PE amp was essentially turned all the way up. At these settings, with the receiver at 56, I got 75 dB on all channels. Listening to a movie after I took the readings (Saving Private Ryan), the sub was WAY too high. But I left it at the initial settings for my readings. I've learned that other people have had to set their receivers to like +8 to +10 in order to get the auto-on feature of this amp to work. At what I thought/think was a "good" sounding level for the sub, the auto-on feature doesn't kick in. Anyway, for the RS meter to measure 75 dB all around on my Sherwood built-in test tones, the sub was too high for movies.

Fact 2: the tube of my sub is NOT glued down at the bottom... I'm waiting for a couple of reasons. First, my toe spikes aren't here yet, and I wanted to be able to install them without having to deal with the entire unit tipped over; and 2, if there are *serious* modifications I need to make, it will be MUCH easier to do with the internals accessible. I realize that my readings could be influenced somewhat by the tube not being secured, and could be influenced by the buzzing of the Delta bench grinder perched on top of the unit... but I'm going to install those spikes before the tube gets glued down.

I took some quick readings last week, and they showed the same dip in the 50 Hz region. I have options on room placement, so we've room to play around. I do NOT have options on receiver crossover.. it is set at about 79-80Hz.

I'll try to attach the Excel spreadsheet before I enter raw data here.. so here we go....

Edit.. so the system won't take an excel file.. I'll try to convert the raw data to Word.. sorry for the inconvenience.

Damn these confounded machines.... some of the stuff I wrote didn't make it... anyway... the receiver's max volume is 70, I was at 56 for the readings. Sitting here watching a movie at a fine volume, the receiver is on 40. The receiver does NOT default to a specific volume on built-in test tones... I can choose whatever level I want.

I didn't differentiate much at less than 0.5 dB.

Here is the raw data, my corrections, and the data I graphed:

Hz Reading Correction SPL
10 0
11 0
12 0
13 0
14 56 56
15 57 11.5 68.5
16 64 11.5 75.5
17 71 10.54 81.54
18 73 9.5 82.5
19 79 8.5 87.5
20 80 7.5 87.5
21 83 7.1 90.1
22 84 6.7 90.7
23 86 6.3 92.3
24 87 5.9 92.9
25 87 5.5 92.5
26 87 5.1 92.1
27 87 4.7 91.7
28 86 4.3 90.3
29 86 3.9 89.9
30 86 3.5 89.5
31 86 3.375 89.375
32 86 3.25 89.25
33 86 3.125 89.125
34 86 3 89
35 86 2.875 88.875
36 86 2.75 88.75
37 86 2.625 88.625
38 86 2.5 88.5
39 86.5 2.5 89
40 87 2.4 89.4
41 87 2.3 89.3
42 87 2.2 89.2
43 86 2.1 88.1
44 84 2 86
45 80 1.9 81.9
46 76 1.8 77.8
47 74 1.75 75.75
48 70 1.65 71.65
49 69 1.6 70.6
50 69 1.5 70.5
51 71 1.5 72.5
52 71 1.5 72.5
53 71.5 1.5 73
54 73 1.5 74.5
55 75 1.5 76.5
56 78 1.5 79.5
57 80 1.5 81.5
58 80 1.5 81.5
59 80 1.5 81.5
60 79.5 1.5 81
61 79 1.5 80.5
62 78.5 1.5 80
63 78 1.5 79.5
64 78 1.5 79.5
65 77 1.5 78.5
66 77 1.5 78.5
67 76 1.5 77.5
68 76 1.5 77.5
69 75 1.5 76.5
70 76 1.5 77.5
71 76 1.5 77.5
72 77 1.5 78.5
73 78 1.5 79.5
74 78 1.5 79.5
75 79 1.5 80.5
76 79 1.5 80.5
77 80 1.5 81.5
78 80 1.5 81.5
79 81 1.5 82.5
80 82 1.5 83.5
81 82.5 1.5 84
82 83 1.5 84.5
83 83.5 1.5 85
84 83 1.5 84.5
85 83 1.5 84.5
86 83 1.5 84.5
87 83 1.5 84.5
88 82 1.5 83.5
89 82 1.5 83.5
90 82 1.5 83.5
91 82 1.5 83.5
92 81 1.5 82.5
93 81.5 1.5 83
94 81 1.5 82.5
95 81 1.5 82.5
96 81.5 1.5 83
97 81 1.5 82.5
98 81 1.5 82.5
99 81.5 1.5 83
100 82 1.5 83.5
101 82.5 1.5 84
102 82.5 1.5 84
103 82 1.5 83.5
104 81.5 1.5 83
105 81 1.5 82.5
106 80 1.5 81.5

I know I'm in a bit of a catch-22... solid readings require the sub to be finished.. but I don't want to "finish" it until I'm sure I've not major mods to make.

Finally, let me say... in terms of sitting here listening.. this thing sounds great. It is not booming... the bass sounds very 'real' and natural.... but of course I'm willing, able, and ready to play around with what I can to improve things. Bottom line is... I can reduce the internal volume; I can increase the volume a bit if I remove some of the lining; and if Doc forces me to do so, I can adjust the port length, although that will require me to rip things apart.... I've plenty of additional 4" pipe to work with. And, if worse comes to worse, I've 48" of sonotube in my shop, which I can cut down if I need to *really* adjust the volume.

I can happily live with this thing as it is, especially considering I've got about $300 in it so far.... but better is always better.

So.. have at it.. be kind.. remember, I'm on *very* limited funds, and I've small children.
Post edited by burdette on

Comments

  • burdette
    burdette Posts: 1,194
    edited March 2003
    edit.. no need to take the time to load this..
  • Dr. Spec
    Dr. Spec Posts: 3,780
    edited March 2003
    Ive got some quick suggestions - first impressions are that your center is very efficient, and redo your calibration off one of the the mains and run the center in the negatives. Also, turn the PE amp all the way up and try to get the sub calibration closer to 0 or in the neg region.

    I'll analyze the FR data later when I have a bit more time.

    Doc
    "What we do in life echoes in eternity"

    Ed Mullen ([email protected])
    Director - Technology and Customer Service
    SVS
  • HBombToo
    HBombToo Posts: 5,256
    edited March 2003
    Originally posted by burdette

    (Sidebar to Hbomb... my wife and kids may be gone much of the summer, my wife's sister is having double hip-joint replacement and my wife is going to help during the recovery (they have 4 kids).. perhaps we'll be able to get together this summer for some fine summer evening listening, if you're interested. I have eighty bucks for you, in exchange for a package of goodies that is up to you to organize.)

    I'm sorry to hear about your wifes sister... That has to be real tough! You are always welcome and we'll have a family secret Home Made Pasta Feast and some cold Brews to keep you Healthy while the wifes away. "Gotta Eat my MAN!!!" Like I said before the speakers are yours at your convenience and are safe and sound.

    I plotted your response then pasted into word for all to see.

    My first impression is WOW that is a damn good first run. You are putting out some Horse Power! It looks like you have a null similar to the one I have. My null is around 50 and yours looks like its occurring at 40 Hz. Doc's advice to me was playing with the phase a bit to dial it out. Your sub really starts kicking in after that and I'll bet the Doc has a good explanation for that.

    I just have not had time to breath lately and have not really tweaked my subs. I am hopeing to get some play time in this weekend plus my parts for the RT55 to 55i conversion came in so I'm going to do that as well. I want to biAmp my 55i's with 200 watts on the low and 75 on the high and see what kind of difference I get. Lots of fun ahead.

    HBomb
    ***WAREMTAE***
  • Dr. Spec
    Dr. Spec Posts: 3,780
    edited March 2003
    Henry - thank you for posting this FR. It's all I need to make a quick assessment. The AVR sub rumble test tone is centered at 40 Hz. That's the reason you "over calibrated" by trying to hit 75 dB on the meter.

    This is EXACTLY why the FR sweep is SO much better than the rumble tone.

    Until you figure out why you have that nasty null, calibrate off one of your test tones instead. Run a few test tones in the 90 to 106 Hz range and adjust the Master Volume to get around 75 dB. Then run a few test tones in the 20-30 Hz range with the sub level set to -3 and lower the plate amp until it comes into line at about 75 dB on average.

    Your FR is VERY flat from 35-15 Hz and from 52-100+ - most excellent. Re do all this and let's re graph again.

    Experiment with placement and phase and let's see if we can kill that null. Also, move the mic 2 feet in either direction laterally and see if the null still exists - some of them are small.

    Doc
    "What we do in life echoes in eternity"

    Ed Mullen ([email protected])
    Director - Technology and Customer Service
    SVS
  • burdette
    burdette Posts: 1,194
    edited March 2003
    Ya, that's pretty much the curve I got, using the interpolated correction factors..although I don't know if I should trust them. Did you use all my data, or only the raw data with your own corrections?

    I'd originally written in my post that the null was around 40Hz, as you said.. then for some reason last night I looked at the data again and thought it was around 50, and changed the post. Must've been the rum and cokes coursing through my veins, plus it was after 1am.

    The crossover on the receiver is at 80Hz, so the response above that would be my Monitor 7s.. unless I'm thinking about this wrong in some way (i.e. brain ****).

    The design allows me to leave the sub where it is, change out a 6" speaker wire for a longer one, and put the amp right in front of me for testing. I can do that and play around with the phase control.

    Thanks to all for any and all help and suggestions (thus far and as we finish this thing up). I don't understand where those spikes are.. PE emailed me that they'd shipped last week.
  • burdette
    burdette Posts: 1,194
    edited March 2003
    Thanks, Doc. I'll do that.. maybe not tonight but within a day or two. Question... having calibrated the sub with the built-in test, and that level being way too high for actual listening.. is that why the 15-35Hz range is up in the 90s and (ignoring the null) the upper frequencies are in the 80 range? I mean, flat is better than not, I just find it curious (worrisome?) that my one particular flat area is so far above the other flat area.
  • HBombToo
    HBombToo Posts: 5,256
    edited March 2003
    Originally posted by burdette
    Ya, that's pretty much the curve I got, using the interpolated correction factors..although I don't know if I should trust them. Did you use all my data, or only the raw data with your own corrections?


    I graphed your interpolated values.... I would say its good data and starts a good baseline. I'm much like you when it comes to data integrity but if we at least use the same method each run the validity will prove itself in. If ya catch my drift?

    HBomb
    ***WAREMTAE***
  • HBombToo
    HBombToo Posts: 5,256
    edited March 2003
    Originally posted by burdette
    I mean, flat is better than not, I just find it curious (worrisome?) that my one particular flat area is so far above the other flat area.

    Exactly what I'm curious about also? I'm really not sure why a gain would occur.

    HBomb
    ***WAREMTAE***
  • Dr. Spec
    Dr. Spec Posts: 3,780
    edited March 2003
    Originally posted by burdette
    Question... having calibrated the sub with the built-in test, and that level being way too high for actual listening.. is that why the 15-35Hz range is up in the 90s and (ignoring the null) the upper frequencies are in the 80 range? I mean, flat is better than not, I just find it curious (worrisome?) that my one particular flat area is so far above the other flat area.

    That is exactly why it is 10 dB higher - because you were trying to ramp up the volume into a null. Calibrate away from the null like I suggested and we'll take another look - it will be much closer I think.

    Doc
    "What we do in life echoes in eternity"

    Ed Mullen ([email protected])
    Director - Technology and Customer Service
    SVS
  • Dr. Spec
    Dr. Spec Posts: 3,780
    edited March 2003
    Remember when recalibrating using the test tones in the 90-106 Hz region (i.e., mostly from the mains and well above the null) and in the 20-30 Hz region (i.e., exclusively from the sub and also below the null), also make sure to include the RS CFs to prevent "over calibration" in the 20-30 Hz range.

    Remember, the meter will read low in that range so you might want to pick a single test tone in that region (you are very flat here, shouldn't matter), for example 30 Hz, and look up the known CF for that frequency and accomodate for the CF as you are reading the meter. In other words, the RS reads 3 dB low at 30 Hz, so if the meter is reading 75 dB, it is really 78 dB and you will already be running a bit hot. When you regraph, the curve should look much closer in overall volume.

    Also - talk about nailing the EBS curve - wow! Right on the bean. Rising room gain to subsonic perfectly offsets the bass shelf, and pow - flat to 15. Perfect. Nice job.

    Doc
    "What we do in life echoes in eternity"

    Ed Mullen ([email protected])
    Director - Technology and Customer Service
    SVS
  • burdette
    burdette Posts: 1,194
    edited March 2003
    Thanks for the information, Doc. I worked a little on this last night and was VERY frustrated. Taking the CFs into account while taking the readings makes sense, and I have not been doing that.

    I have at least one question.. there may be more by the time I finish this post.

    You said to set the mains to 0 on the receiver, use 90-106 test tones and set the master volume so I get 75dB. I do that with BOTH mains playing, or only one? Seems if you set with both using a tone then any specific sound from only one would be .. what.. 3dB down compared to the reference?

    Last night I discovered that my receiver allows you to set different levels for the mains and the sub in audio and video modes, and it remembers. Couldn't figure it out at first last night... the system is 90% HT use, so it almost always powers up in that mode. I set the sub to -3 right away (in video)... started testing (in audio)... and the sub was at 0 again... that may have happened the other night, too, and I wouldn't have known it. And if I set levels (including the PE amp) using the built-in test tones in video, then the sub would have been 3dB hotter when I switched to audio for the CD tones.

    It also just hit me sitting here that I may also be able to set large/small for each mode... I seemed to be having way too much of the below-80 tones coming from my mains last night - to the extent that I wondered if the receiver's crossover was even working. My test tones are on a CD, and I don't think I've ever changed large/small in audio mode. It obviously would affect the readings if the mains are set to large.

    My DVD player does NOT like this test tone CD... so I believe I'm going to have to do all this in audio. That means I'll have ONLY the built-in tone for the center and surrounds.

    With all this mess (different settings for a/v, mains maybe on large in audio, etc) ... I am not at all confident in any of the readings I've taken so far (at least not confident in the relative levels of say the 30Hz range to the 100Hz range). No teacher like experience, so I think I may actually be on track to get decent measurements.. so... do I set the initial 75dB master volume with only one main playing, or both?

    Last thing.. again, given the mess... I took readings last night from around 35Hz to maybe 60Hz with the phase control at 0, 90 and 180. Slightly different numbers in each, but the null appears to remain.

    Also, thanks for the positive words and proclamations on the design. Whatever else is or isn't going on, I do indeed go to 15Hz flat... I would agree that I appear to have nailed the EBS design.
  • Dr. Spec
    Dr. Spec Posts: 3,780
    edited March 2003
    Use one main, left or right. It's just that the center is so efficient, you end up running all the other speaks hot, which is not the best to minimize pre-out voltage distortion. The center will end up heavy into the negative, but that fine.

    Also be aware that in certain audio modes, the digital bass management is bypassed and it (can) send a full range signal to the mains - check on that.

    As far as the mains getting bass below 80 - well they should - to an extent. The high pass filter rate is probably 12 dB/octave, maybe 18 at the steepest. With the sub, the low pass filter rate is usually 24 dB/octave.

    You can check this by powering off the sub but leaving the speaks set to small and the sub set to yes and running the sweep and seeing just how far down the mains actually go. You can even plot your results for the mains only and see exactly what the high pass filter rate is.

    Ditto for the sub - you can unplug the mains and run the sweep up past 80 Hz and see how long the sub hangs in there. You will find it is much steeper of a cut-off rate for the sub to prevent localization.

    Your AVR test tone calibration method is probably FINE for the mains and surrounds. It was the null that was throwing you off. After you recalibrate off one of the mains using the normal AVR test tones, set the sub to -3 and just throw in the sweep CD and play just the 30 Hz tone and adjust the plate amp until the meter reads 75 dB. That will get you around 3 dB hot on the sub (at least in the 35-15 Hz range.

    I didn't think phase would fix the problem, but at least you tried. Placement is your better hope. All in all, this is a excellent looking house curve. That null WILL go away with placement experimentation. The sub might not end up where you thought it would go, but you will get this null to go away.

    Doc
    "What we do in life echoes in eternity"

    Ed Mullen ([email protected])
    Director - Technology and Customer Service
    SVS
  • burdette
    burdette Posts: 1,194
    edited March 2003
    Thanks, Doc. I may get to all this tonight. Sorry if I'm being Rainman on this - I appreciate your patience... I are a smart guy most of the time.. I have degrees and everything. I think I was being thrown by what the receiver was doing... or better said, thrown by my failure to know what the receiver was doing.

    All right.. makes sense that I use only one main.. that is actually what I did last night.

    My usual settings were to have the mains on 0 and the center down... somewhere in this sub testing process it changed, so I'm back where I started and thats where I'll stay.

    As for the crossover from sub to mains... I realize that there will be some overlap... even considering that, I was surprised by what I was hearing. On the bass management issues in audio.. so the receiver would continue to send a full-range signal to the stereo pair even when sub is set to Y?? Huh... seems odd that designers would do that. But, now armed with the meter and test tone CD, I can do all sorts of response checks. I've been curious what I'm getting out of these 7s on full range... and I may even take a swipe at the KLH rebuilds I made.

    Course, course, I definitely need to take measurements.. definitely. Need to go to Radio Shack... Radio Shack has meters. I'm an excellent driver.. Ut oh.. ****.. ****... yep, I farted... Of course, those are not my response curves, I don't have my response curves...
  • Dr. Spec
    Dr. Spec Posts: 3,780
    edited March 2003
    Originally posted by burdette On the bass management issues in audio.. so the receiver would continue to send a full-range signal to the stereo pair even when sub is set to Y?? Huh... seems odd that designers would do that.

    No, not always - I said it CAN be that way. Here's what I've seen in "audio" modes:

    full range only, no sub;
    full range mains, and sub also gets bass;
    mains stay high passed, only sub gets bass;

    Regardless, even with an 80 Hz high pass, your speaks will play far below that point, and that's why I continue to recommend 80 in most cases. I've tried 60 on mine and don't like it - loses impact and power.

    BTW, it was my fault on the center channel issue. I always pick the center by habit, but not if it's 5-6 dB more efficient that the other speaks.

    Yep, I've done all sorts of sweeps on my speaks - I have full range close mic
    graphs for every speaker I own. It helped convince me to stay with an 80 Hz filter point actually - the CS245i's can't take a 60 Hz filter point - just too low.

    After you recalibrate the plate amp/sub off the 30 Hz tone (should only take a minute), jam that sub in another part of the room and run another sweep.

    Also, do a close mic sweep on it to prove to yourself that null is room induced and not a fault of your design. Split the height of the sub with the mic and run it at 3 feet.

    Doc
    "What we do in life echoes in eternity"

    Ed Mullen ([email protected])
    Director - Technology and Customer Service
    SVS
  • burdette
    burdette Posts: 1,194
    edited March 2003
    Thanks. Didn't mean to imply that I thought that YOU thought that you were uttering a universal truth. I knew you had that 'can' in there... my comment was intended to express surprise that they'd design it that way in *any* case. Sort makes me wonder if audio designers are actually audio enthusiasts... sort of like getting marriage counseling from a priest.

    Also, thanks for the suggestion on the close-mic response. Yes, indeed, I've had a bit of a pit in my stomach wondering if there was a design issue with the null... who knows what.. volume off or lining wrong or wrong sized screws...


    Oh.. I have a question for you *unrelated to FR sweeps*.. whoo hoo..

    I got some emails from a guy wanting to build a sonosub (not a Polk forum member), and just in the course of the exchange I mentioned that I wasn't EXACTLY sure of the internal volume, that I'd accounted for the driver and port, but had changed the lining to the thicker egg-crate mattress pad. His response was that the average lining on the walls of a bass reflex system, poly batting or egg-crate foam or whatever (i.e. not some esoteric specialized stuff) is acoustically transparent to the driver. In other words, it does not subtract from the volume 'seen' by the driver. Is that correct? If the lining is acoustically transparent to the driver and does NOT reduce effective internal volume, how does it then accomplish ANYTHING in terms of standing waves or resonance or whatever you're trying to prevent by using it in the first place? I mean, even if there is a lot of air puffing it up, it has mass, it is a solid, it HAS to take up SOME physical space.

    Maybe I'm missing something, or don't understand some fundamental aspect involved... but I can't seem to get my mind around his assertion.

    Surprisingly, for the wealth of information out there on DIY subs, there is almost nothing on lining, materials to use, etc. It isn't even mentioned in most DIY write-ups, and in passing in a few others.
  • burdette
    burdette Posts: 1,194
    edited March 2003
    Hey Doc... I just spent more than an hour taking measurements. I'm not going to post a graph, but I do want to tell you what I found out.. see what you think. Well, maybe I'll post a graph.. take it with the grain of salt of the remainder of this post...

    First, I violated a basic law of testing.. I changed two variables at the same time. I moved the sub from right next to the right main, near the front wall, to the right side wall, a little forward of the right surround. I also moved my **** two feet left on the couch, which put me almost in line with the left main.

    This room is 14' across the front, and the HT is somewhat off-center to the left (the center of the TV is 5' from the left wall), and the surrounds are 14' back from the front wall... but after that the room opens up to a larger space.

    The null at 50Hz went away.. a null at 60 appeared when I recorded the numbers leaving the meter pointing straight forward. As I sat there, if I changed the lateral position of the meter by 12-18 inches, or the direction of the meter, I could vary the reading at some frequencies by as much as 8-10dB. I never extended my arm fully either left or right, and I tried to stay within about +/-22.5 degrees from straight front. Even with those limitations, I could pretty much produce any graph I wanted.

    I took readings using this 'swinging meter' method. The numbers I recorded weren't really "averages".. I just tried to be 'honest' - not pick the best reading, but neither did I take the worst.

    I also realized about 15 readings in that my sub amp volume was no longer valid for a reading of 75 dB (to match the mains) in the 90-100Hz range. That had been set with the sub up front, and I'd moved it and didn't recalibrate. However, I did disconnect both mains so I was reading ONLY the sub. It has been obvious from the first sweep in this room that that if the reference level isn't in the 75-80 range, I don't get any readings below maybe 19-20Hz.

    I hope to put the sub in the middle of the room and do a close-mic sweep this weekend. But I want to ask.. SHOULD it be in the center, away from all walls, or should it be in a position that is realistic for a final position?

    So, all that said.. and realizing that I could swing the meter a little at any frequency and change the reading.. here is *a* graph...
  • burdette
    burdette Posts: 1,194
    edited March 2003
    Strange.. not only did the attachment not show up in the original post, "Edit" didn't give me the opportunity to add one.. so.. try again...
  • Dr. Spec
    Dr. Spec Posts: 3,780
    edited March 2003
    Phew - this is fun, isn't it?

    I told ya it was the room :-). If you really want to see what your sub is doing from a design standpoint, ground plane close mic sweep is the only WTG. This may sound ****, but if you don't have an anechoic room, it is not uncommon at all for DIY'ers to place the sub outside away from the house to really evaluate it's true FR from a design standpoint. I'm not necessarily advocating that, but if you have that nagging "pit" in your stomach, it can help.

    And yes - as I suspected, moving the mic in either direction changes the FR considerably; even holding it differently causes changes. That's why I always plop it in the same spot (exactly where my head goes) the same way, every time I calibrate for any reason.

    I like the curve better in the first location. You can certainly try other locations, or put the sub on the couch and crawl around the room and listen for the best bass and then run a sweep at the spot that sounds the best.

    Finally, a BFD is a good investment for bad rooms. At $120-$140, it can do wonders for flattening peaks and it is very popular with the sub crowd. It won't help much for nulls, but then again nothing does.

    Finally, adding fiberglass or polyfill (believe it or not), actually fools a sealed sub into thinking it has a greater internal volume (up to 25-35%), despite the fact that the material itself clearly displaces physical volume inside the enclosure. For ported subs, they should not be stuffed per se, but rather just lined, as you have done. The lining will reduce the "hollow" sound inside the cabinet, and make it more acoustically inert. You don't wan't standing waves and resonances inside the enclosure making their way out the cone or the ports.

    Doc
    "What we do in life echoes in eternity"

    Ed Mullen ([email protected])
    Director - Technology and Customer Service
    SVS
  • HBombToo
    HBombToo Posts: 5,256
    edited March 2003
    This is so interesting because there are many similarities in this aspect of our hobby to my job. Imagine trying to measure wave propagation of 2GHz from a tower location over 360 degrees at a radius of ~7miles... talk about scratching your but! The room response measurements we are doing here are very similar and difficult. Wave mechanics are probably as difficult as the most difficult of engineering disciplines at what ever frequency we are discussing.

    back on topic.
    I was thinking the same thing when Doc provided the advice to take the sub outside if you really want to quantify the design parms. That said, I believe your gut feal within your room on placement will provide the exact information desired regardless of the number a variables changed. IMO the sub is what the sub is and at this point you should really just work with what you got. As time passes and familiarity with the subtelties become apparent you will know what direction to proceed. Brute force engineering is not always the way to go... art and magic in this case will really benefit you.

    Make sure you don't get all wrapped around the axel over this and just enjoy it for what its worth.

    IMO of course.

    HBomb
    ***WAREMTAE***
  • burdette
    burdette Posts: 1,194
    edited March 2003
    edit: duplicate post (for some reason), deleted.
  • burdette
    burdette Posts: 1,194
    edited March 2003
    Thanks, guys. Welcome to the weekend.

    Nah, I'm not fretting too much. I think I'll put it where it fits best in this room and just leave it. It sounds nice, regardless of nulls or peaks. Interesting to me that my wife and I could be watching a movie, she's next to me on the couch, and we are getting different frequency response curves delivered to our ears. I really don't think that I'm going to escape that completely in this room (any room?), even if I spend the next month calibrating and moving and phasing, etc. I wasn't even going to get a meter so I wouldn't have known any of this anyway. Heck, if I ever get the bug for a new sub (not likely), I'll just sit on a different part of the couch.

    Cost was a major factor here, so I won't be getting any outboard processor or anything. At this point in our lives, with monitors on during movies, no *very serious* music listening time, I think I'll take my "flat to 15 for around $300" and run. I will perform a close-mic sweep within a few days.. see what I get. I'll do it in the middle of this room.. I know I'm not hauling equipment outside.

    I believe it is a good design, executed properly... and the sonosub part of it was cheap cheap. Someday, I'll make a furniture-grade cabinet and upgrade the amp and test and move and everything to a greater degree... but this gets the job done and adds tremendously to our overall frequency response. It certainly fills in the space from around 40Hz down, which my 7s didn't carry. Based on what I've seen, I would have had to spend pushing 3-times the money on a commercial sub to get the performance I own.

    Thanks for all the help and input. I'll post the close-mic graph once I get it done.

    Have a great one.. we're freezing our collective asses off today.. and after it was like in the 70s earlier this week. Sheez. At least my 2 year old has stopped barfing... last two days, look at the kid cockeyed and he'd pop.

    Check out the 'oxymoron' thread.. best laugh I've had for awhile.

    Oh, Doc.. you didn't really answer my question.... I built a pair of sealed speakers this winter, using the KLH drivers I got from Russ for shipping only. I obtained a few of the T/S parameters from KLH, and designed a more-appropriate box than they'd used (I'm sure they made some compromises given that they sold these things for under $100). I wanted to keep the box size under 1ft3, the design called for larger, so it was fully stuffed. So, you're preaching to the choir on stuffing-theory in sealed enclosure.

    As simple as I can put it.. if you were building a sub.. or any bass reflex speaker... would you, or would you not, add volume to your box size to account for lining, as you surely would for the driver and port(s)?

    I'll attach a photo of the KLH rebuilds I made, just for kicks and giggles. They are serving VERY nicely as our upstairs speakers... filling a hole I created when I abducted our Monitor 5jr+ for surrounds. The photo is flipped.. they are on the wall upside down to keep the tweeters as low as possible, closer to ear level.
  • Dr. Spec
    Dr. Spec Posts: 3,780
    edited March 2003
    Originally posted by burdette
    Thanks, guys. Welcome to the weekend.

    but this gets the job done and adds tremendously to our overall frequency response. It certainly fills in the space from around 40Hz down, which my 7s didn't carry. Based on what I've seen, I would have had to spend pushing 3-times the money on a commercial sub to get the performance I own.

    Oh, Doc.. you didn't really answer my question.... As simple as I can put it.. if you were building a sub.. or any bass reflex speaker... would you, or would you not, add volume to your box size to account for lining, as you surely would for the driver and port(s)?

    Yep, most people don't know what they're missing below 40 Hz - good job.

    I wouldn't quite go "three times" - I'd say you have probably 100% of the FR and 85% of the max SPL capability of an SVS 16-46PCi for a bit less than half the cost. The 15% being allocated to the BASH amp which is decidedly more powerful than the PE amp, but also costs a bunch more.

    Regardless, DIY is the best bang for the buck going and you've proved it. Were all the hours of construction worth the $350 savings over the 16-46PCi? Only you can answer that and I suspect the answer for you is "yes".

    Anyway, to answer your question, if I used the more solid egg-crate foam, I would probably (pending confirmation from a 3rd party) include as least of fraction (maybe 50%) of it's actual volume as physical volume taken up inside the enclosure. For the more porous fiberglass and poly fill, probably not.

    Doc
    "What we do in life echoes in eternity"

    Ed Mullen ([email protected])
    Director - Technology and Customer Service
    SVS
  • VE6OHV
    VE6OHV Posts: 119
    edited March 2003
    This is a great thread guys. I am in the process of building a type of "tube" sub myself, using laser cut 1" thick interlocking MDF rings. This is the kind of stuff I am after as far as testing procedures and data collection.

    I am currently looking for a pair of 12" drivers, the information on drivers I am finding is difficult to undersand. What are some other drivers that you could reccomend? Is the Adire line all it is cracked up to be? Has anyone used "corian" as a reflector surface? Also other than a plate style amp what could I use?

    Lot's of questions -
    Keep it up - it makes for a great read......
  • burdette
    burdette Posts: 1,194
    edited March 2003
    Well, as for performance and cost.. I decided from the beginning that max SPL was not a concern nor a goal... ah.. whatever, it doesn't matter. I saved a shitload of dough and can look you in the eye and say "ya, I made that."

    The design and build process was as much a part of the enjoyment for me from this as actually having a good sub. In fact, I have to admit that I'm experiencing a little let-down that the whole thing is done. I'd do it again in a heartbeat for someone else if they wanted to buy the parts but not do the build. In fact, a guy I know saw me carrying that AV12 out to my car when it first arrived, and we've chatted about subs a little since then. He wants to add some bottom end to what he has.. and I found out what he has is a Bose Acoustimas 5.1 setup, without a point one (and why would I bet my left nut that he has a Sony receiver?). He balked at the money I spent, but I told him we could find a fine driver (Madisound, or used) for a lot less than a hundred bucks. I also was going to point him to the PE $100 sub that gets such consistent rave reviews in terms of dollars for performance.. but it is discontinued. Supposed to be a replacement later this year.

    I do have to correct one misstatement I made... A sonosub is not cheap cheap. It is certainly more expensive than going with a conventional box if you're happy with painted MDF. It is less expensive than a furniture-grade cabinet, however. I had "easy easy" on my mind, but typed cheap cheap, probably because I'm poor and a tight-**** and cost is *usually* the primary concern.

    What a sonosub IS is a much easier build, especially for someone who would have problems cutting large panels that needed to be VERY square. The speakers I posted above are 20" tall - as my shop sits right now that is about the largest box I'd attempt. A large dandy table saw was actually in the deal with my wife when we bought our house 7 years ago, but I don't have the room for it and other things came up and, it just didn't happen.

    Assuming you have the tools (primarily a router, and you need at least a DIY circle jig, and a small drill press will make things a lot easier and accurate), the only real chore/trick is to get your circles on the money. It was a very nice change from cutting six panels and building a box.
  • burdette
    burdette Posts: 1,194
    edited March 2003
    Originally posted by VE6OHV
    I am currently looking for a pair of 12" drivers, the information on drivers I am finding is difficult to undersand. What are some other drivers that you could reccomend? Is the Adire line all it is cracked up to be? Has anyone used "corian" as a reflector surface? Also other than a plate style amp what could I use?

    Lot's of questions -
    Keep it up - it makes for a great read......

    I'll take a stab at these, at least up to my level of knowledge.

    First, if you are in the price range of MORE than $125-$200 for a driver, I can't help you a bit. That is where I researched.

    I would say the Adire line is *the* standard by which other DIY drivers are measured, and I'd say they are probably in more DIY boxes than any other brand. MOST of the "what do you think of this driver" questions on forums say something about "is it better than the Shiva/Tempest?" Even yours references Adire.

    I, personally, never got comfortable with the foam surround and paper cone. Don't want to get into a heated debate about it.. just my personal warm-fuzzies. In my opinion, the basic Stryke models (AV12 and AV15) are at least one step up from the Shiva and Tempest. Build quality and materials for sure. But, people sure use and seem to like the Adires. Short of an Adire failing in some fundamental requirement you have (?), I don't think you'd go wrong. And there is a *wealth* of information out there on them. The Adire site itself gives three applications for each, for those people not wanting to get into design.

    The Dayton drivers also have an enthusiastic following. They are clones of other drivers on the market, the Shiva and the NHT1259, specifically, in 12" models. They hit the mark in some ways, not in others. One is considered MUCH closer to its intended target than the other.. don't remember which, though. Might be able to track it down if you're interested in Dayton. All in all, honestly, I would have gone Adire over Dayton had I not gone Stryke.

    I also saw a smattering of DIY subs using Peerless.

    If you don't want to design, Adire would be a strong consideration in my opinion. Tons of resources; internet page after page dedicated to DIY builds; the site itself gives you designs to copy if you want; customer service is supposedly first rate, plus.

    As for the amp, no reason at all that you have to use a plate amp. They are simply available, not too expensive, and work nicely for most DIY applications. You'll have to talk to other folks about using a separate amp, crossover, etc.