Room Response for Dual SV 20-39CS+

HBombToo

Doc, I don't have my files at home so here is the output from the room response disc uncorrected. I did a run crossed at 100 also but there was very little difference. I saw a 58 dB on Track 9 but I'm not confident about that reading.... The h/h sub is now at -5 and the SV101 is at ~ +3 with a phase of 0 and 20Hz falloff

XOver @ 80 Hz and set to 85 dB for Track 41

Track dB
1 81
2 -
3 -
4 -
5 -
6 -
7 -
8 -
9 -
10 59
11 59
12 71
13 77
14 82
15 84
16 84
17 84
18 83
19 80
20 82
21 82
22 82
23 83
24 84
25 87
26 89
27 89
28 88
29 86
30 82
31 77
32 66
33 72
34 72
35 79
36 81
37 81
38 76
39 78
40 84
41 85


What do ya think???
Thanks
Henry

goingganzo

31-34 might be around 80hz you might want to change the phase. but looks very great. happy booming

Dr. Spec

Henry - I'll plot this tomorrow - saw it too late tonight.

Your 80 Hz filter point is at 37-39 and looks OK, but you might try 180 and see if that little dip at 38 (79.4 Hz) comes back up.

You have a room null at 56-63 Hz; try experimenting with placement of both the subs and the mic (move it to either side 2 feet first before you move the subs and run the sweep again).

You have a mild peak around 40 Hz that looks like it might sound a bit boomy. Again - placement experimentation.

You must have the SS filter set to 20 Hz - the subs start coming on-line strong at 19 Hz.

Overall this is an EXCELLENT house curve and I have not added any correction factors yet, which may alter my initial impressions and statements. Let's get it graphed tomorrow with the CFs and have another look see.

Doc

Dr. Spec

Henry:

Here is your graph. The null at 56 Hz is quite ugly - worse than I thought, and the FR is a bit ragged from 65-100.

I always set tone #1 (100 Hz) as my reference and work from there - I noticed you used tone #41 (94.4 Hz) as your reference. I like to get up well into the mains as the reference to really evaluate the transition from the subs to the mains.

First you need to dial in the phase with the other sub as I previously discussed in my PM. You'll need someone to turn the phase control as you watch the meter.

That null could be phase related, or it could be room induced. Only way to tell is deal with the phase first and run another sweep. If it stays, then it's the room and start experimenting with placement to the extent you can.

You cannot equalize a room null with EQ. It's like dumping water into a bottomless pit. The only way to eliminate it is with phase or placement.

From 47 Hz down to 20 Hz you are quite flat and it looks nice. As advertised by SVS, the 20-39 enclosure checks in flat to exactly 20 Hz. The sharp drop-off thereafter is due to the SS filter. You should actually be -3dB at around 17 Hz if you set the SS filter to 15 Hz for the next sweep.

You may also want to try a 60 Hz filter point on the h/k and see if that smooths the FR in the 60-100 range.

60 Hz will tax the mains and surrounds a bit more but will be nothing compared to running them on large. What is the highest F3 of any of your surround speakers? That will pretty much tell you if you can run them at 60 without experiencing a drop out in the FR.

Doc

HBombToo

My bust on the start track... The way it was acting I thought it was the 100 Hz... this should not throw much error in our start.

I was shocked by the dip also and I hope its a phase issue and not something else. I have this nagging thought that there is something wrong with the h/k crossover or processors. I wan't to do a comparison between 100, 80 and 60 on Dolby then do a stereo only between 40 and 60 and map the differences with mains and without. This should ensure the h/k and fronts are eliminated as a failure mechanism. Reason being, I have noticed some strange occurrances with the Logic 7 or Dolby processors when running analog in and then matrix processing for surround. Every now and then it seems as though the processor loses its bolts and goes from surround to 5 channel with only the left channel driving the speakers... This does not happen that frequently but it does happen.

I was however astonished at the really low gain setting required on the SV101. I used the minimum 1/4 setting that the owners manual suggested for the h/k. It is amazing what an additional gain stage brings to the bass. This added gain will really help increase the base for some 2 channel thumping.

Thanks for your help Doc and Gonzo and I have some work to do...

Henry

Dr. Spec

Henry:

I just took another look at your sig and you can easily run a 60 Hz filter point.

Yes the SVS01 can offer up to 18 dB of clean gain to the sub pre-out. Normally it is usually needed when the AVR pre-out is too weak to drive the Samson to its full power. That is not the case with you so you've got room to spare for clean gain with 2 channel music.

HOPE you can fix that null with just the variable phase control. I've seen this many times and I actually suspect it is a room induced null.

Before you do anything else, disconnect one sub and run a close mic sweep on one sub at 3 feet with the mic at the midpoint height of the sub. Then do the same for the other sub. That will give you an approximate ground plane FR for each sub and tell you what that sub is actually doing before the room and the other sub has a chance to affect it.

Also, before moving the subs for placement experimentation, move the mic two feet left and two feet right and try it again to see how large that null is. Some nulls are tiny - only a few feet wide. Other ones are much larger.

The test tones are incredibly useful for evaluating the effect of different filter points, phase settings, and sub placement. You can even use them to determine the true F3 of your 800/400/55 speakers - just set them to large with no sub and run a close mic sweep on each one. You can run on Logic 7 with the others disconnected, or you can simply run them each off the mains output in 2 channel stereo.

Since I have banana plugs all around, I do the Logic 7 route and just pull the plug on the other speaks. I have run close mic FR sweeps on the RT800i, the CS400i, the f/x1000, and the CS245i so I can select my high pass filter point with confidence.

Doc

BeginnersLuck

Hey guys-

Just out of curiosity, what tracks are you using? What CD are they from? I want to sweep my sub but I want to use the same test tone material. Please advise.

Thanks,
-BL

HBombToo

Originally posted by BeginnersLuck
Hey guys-

Just out of curiosity, what tracks are you using? What CD are they from? I want to sweep my sub but I want to use the same test tone material. Please advise.

Thanks,
-BL

send me your addy and I'll burn a copy of the cd Doc sent to me and mail it out tomorrow. hnavaroli@alamosapcs.com

Its fun and a great learning experience.

Thanks Doc! more to come.

Henry

Dr. Spec

BL:

This is a custom 1/12 octave sweep from 10-100 Hz. Each tone is 10 seconds long and they are .mp3 files.

There is a website for downloading, but it is down occasionally.

http://beyond_gomer.tripod.com/

Go here for the Radio Shack SPL meter correction factors.

http://www.hometheaterhifi.com/utilities-download-page.html

Doc

BeginnersLuck

Where do I position the Radio Shack SPL meter to take the readings?

Thanks
-BL

tryrrthg

this is a good site for tones also. The gomer site never seems to be working.

http://www.snapbug.ws/sinewaves/

burdette

I don't want to start a new thread for this news... but it is pretty interesting.

I am in the middle of a pretty substantial rebuild of my sub. I told you about the buzzing amp board.. I cut it off. At louder volumes, I still noticed a very severe buzzing that I thought was due to the base board vibrating (it was 3/4" plywood with 3/4" ply criss-cross braces.) So (and I'll post a pic of this sometime) I created a one-and-a-half inch thick concrete bottom for my base board and went from 4 spikes to 3 on the floor. Coincidentally, I happened to have a piece of 16" round concrete former that I put on the bottom of the base as a mold.

Still buzzing.. which didn't make ANY sense given how solid the base is. SO.. a little more analysis.. and guess what...

My design had long screws coming from inside the tube, out the baffle, and into 4 hardwood, 4" legs, that sat on the base board. They were secured to the base board with 4 more long screws. All of the screws were *parallel* with the force of the driver. Well... the power of this driver essentially took the sub apart. The screw-hole in the top of at least two of the legs is stripped out.. the sub was trying to blow the bottom off of itself. THAT is where the buzzing is coming from. So, I'm going to use my cool concrete-laden base, but I'm going to replace the 4 legs with 3 oak boards, double-thick, with the screws going in horizontally, perpendicular to the force of the driver. These boards will hold the tube/driver up 4" off the base.

Although I'm still working on this sub, and feeling just a *little* frustrated that it didn't come out perfectly the first time, ALL of the modifications I'm having to make are due to my underestimating the power of the driver. The other night, the sub was sitting there NOT attached to the heavy base, and with no weight on top.. sitting on the 4 wooden legs... I think we were watching U-571.. anyway, it pretty much lifted itself off the ground.. not all four legs, but I know 2 of them were up.

So, given the need for a stronger build, I am not putting too much into the readings (especially trouble spots) I've already taken. I should be finished with this this weekend and will then see what I've got when it is ONLY the driver making sound, and not some part of the enclosure.

TonyPTX

Not sure if I understand your configuration, but as a suggestion, can you replace the screws with a nut and bolt configuration using nylon nuts so that they're self locking?

Tony

burdette

The only way to do what you suggest is to remove the driver, redrill holes, and run bolts through the baffle, through the legs, through the base, and then put a nut on. That would have to be one long bolt (8" at least).... and I'm *really* not wanting to remove the driver at this point. That sounds like a good idea for next time, however.

I believe the new legs/supports I'm going to use should work fine this time. I'm viewing this sub as a prototype.. the one where I make mistakes and learn. I'll rebuild some other time.

Actually.. you've got me thinking... I am going to at least consider putting a larger, single screw.. or lag bolt.. up through the bottom, through each leg, into the baffle.

TonyPTX

Originally posted by burdette
That would have to be one long bolt (8" at least)....

Home Depot and Lowes sell all threaded shafts in sections in 2', 3', and 4' sections. If it's not a nut and bolt combo, then it's a 2 nut and a long shaft combo....

No this is not a porno....:p

dorokusai

What about an F1NUT? Sorry I had to say it, apologies for bad humor go out to forum member F1NUT.

Dr. Spec

Burdette:

That's why Ron-P went with full length threaded rods with big washers and nuts compressing and anchoring his end caps to the enclosure. I mentioned and recommended his design more than once and I still feel it merits serious consideration with a DIY sono-tube subwoofer.

The sonotube is so thin, there isn't much to attach to, but it is extraordinarily strong in compression and can take a huge amount of force without buckling or collapsing.

Doc

burdette

I know, Doc. I read about or got advice on quite a few different designs. And I've appreciated all of it. I've learned lessons at every step of this build, and also have confirmed that I should indeed trust my gut. I usually do... and usually regret it if I don't. I have another piece of tube in my shop just waiting for me to learn all the lessons and formulate my final plan, and I'll build an entirely new sub this summer.

Also.. any of the 'problems' I've had appear only at volumes which well surpass our usual level. I would *maybe* listen to a movie or music that loud if I were in the house alone - but not for an extended period of time. So.. it's all good.