BFD Input Level?

**allredp** · **03-21-07, 05:42 PM**

Hey Shacksters,

Just getting my BFD 1124 set up and ran into my first snag!

I'm following the BFD guide about setting the input level by getting the in/out blinking green and then playing U-571 at loud level (-30 on my RX1200 Yamaha AVR). Then I adjust the LFE level in the AVR, right?

The problem is that I'm all the way backed off the input level (-20 on my AVR, which has a range of -20 - 0) and the BFD is clipping heavily! The red is pretty much on continously when the depth charges are going off.

I've got the BFD chained between my AVR (sub out to the BFD #1) and the sub (BFD #1 output to the SVS PB12+/2).

Any help would be much appreciated! I'm anxious to fire up my freshly downloaded REW and start cranking out charts and graphs like the rest of you.

Thanks in advance,
Phil

**brucek** · **03-21-07, 06:40 PM**

Your receiver may have an unusually high output level. The solution is to switch the operating range of the BFD from -10dBV to +4dBu setting. The switches are on the rear of the BFD. One for each channel.
See if you can now turn up the trim level of the LFE and use as much of the input range as possible.

brucek

**allredp** · **03-21-07, 07:06 PM**

Hey Bruce!

Much obliged on that help--I'll kick the kids off the xbox and try the +4 setting tonight. With only one sub I only need to do that for channel #1 and then gain it as much as possible without clipping as I set the input level, right?

BTW, are there problems with using the +4 setting? Since the BFD Guide is pretty pointed about using the -10 setting, I'm assuming there are some negatives...

To be painfully clear for a low-tech such as myself, I only have one sub--so am I using just one channel on the BFD, right? It doesn't matter whether I use #1 or #2, right? If this is so, then there will only be one set of LEDs jumping, right?

This is deep tech for a history professor!

Thanks for the help, Bruce.

Phil

**blue_max** · **03-21-07, 07:11 PM**

I hope the previous suggestion helped you. I would just say that a volume level of -30 does not seem particularly loud. I live in a ground floor flat, so obviously have to be neighbourly, but my maximum level is -18. Admittedly, that is pretty loud though. My thought was whether you have some settings active on your dvd player which may boost the LFE channel. Sometimes there are settings on amps for bass boost too, which are often buried in the settings.

Graham

**allredp** · **03-21-07, 07:23 PM**

Hey Graham--I hear you on that volume level, but I think that my Yamaha (nearly 6 years old now) is just goofy on the numbers. I noticed that the next year's version volume went into the + regions, whereas mine just stops at 0.

There are a few DVDs, like Star Wars II that I can boost to -26 or so without feeling fear about blowing things, but for the most part -30 is plenty.

I should get my RS SPL out and check the decibles to see what the SPLs are. In fact, I'll do that tonight and report back. Maybe I'm just a wanny...

Cheers,
Phil

**brucek** · **03-21-07, 07:45 PM**

Quote:

With only one sub I only need to do that for channel #1 and then gain it as much as possible without clipping as I set the input level, right?

Yep...

Quote:

BTW, are there problems with using the +4 setting?

Well, any consumer (non-PRO) piece of equipment usually doesn't have the level required to operate in the +4dBu range that a PRO system would. The +4dBu selection will realize a slightly higher noise floor, that you can establish as a problem or not by simply pushing the switch and listening at the sub to see if it is objectionable.
Then you would like to establish if your LFE out can produce enough level to use that range. If you could get a yellow LED on once in a while that would be optimum, but if not, at least be sure it is reasonable.
The -10dBv setting allows a maximum input level of +2dBV, which is ~1.26vRMS. The +4dBu setting allows a maximum input level of +16dBu, which is ~4.9vRMS. Quite a bit higher range.

Quote:

I only have one sub--so am I using just one channel on the BFD, right?

Yep..

Quote:

If this is so, then there will only be one set of LEDs jumping, right?

Yep...

brucek

**allredp** · **03-21-07, 11:38 PM**

Sweet--I'm listening/feeling WOW when the Pods emerge! Holy Cow, the storage door next to my PB12+/2 is making horrific noises! I thought I'd done irreparable harm to the sub by ramping up the LFE level!!! Turns out I just have to get some special weather-stripping or something...

Anyway, with the BFD set to +4 and my AVR LFE set to full gain (which is 0), I am getting some yellow on the peaks, with the extreme stuff getting a touch of red. I've used WOW, XMenIII, and U-571 to get the hottest LFE. BTW, the most LFE is in WOW--where the lasers are getting some slightly sustained red on the hottest parts.

Should I back my LFE down a notch or two? Or is having some red for a second ok?

Also, Bruce, you mentioned that the noise floor will increase with the +4 BFD setting, how do I test that? I'm not noticing any noise coming from the sub, but how would I test it? Would I put on a deliberately soft passage from a DVD and try to hear something from the sub? Sorry if this is a stupid question--I just want to understand.

Graham: I've tried to use the RS SPL for getting decible readings, but I'm a newb and don't know how to use the **** thing. When I set it at 80 (C fast) it tops out at 90, when I turn the range up to 100, then I get 109 at my seating position (about 15' away from the sub). What am I doing wrong? Anything?

Now, on to the next steps to get REW running and filters loaded...

Thanks so much for the help!
Phil

**blue_max** · **03-22-07, 02:43 AM**

Here's what I have learnt...

Firstly - remember this principle. You have now got the maximum signal from the LFE port of your amp into the bfd. The only things that will affect this now are the amps volume (which you have decided is as high as it's ever likely to go) and the actual volume on the sub's amp itself. The sub could be on zero volume or max and the bfd won't care. You need to balance the subs volume to match the other speakers.

The amp should have a test tone and either manually or automatically sweep to each speaker. This has a set volume of 75db (I think this is universal to all amps). Sit at your usual position and ideally use a tripod to mount the meter vertically (microphone at the top). Set it to the 70 range, c-weighted and slow. When the sound plays, you need to adjust the speaker volume via the amps channel adjustment. The needle needs to sweep past the middle and settle at +5 to reach 75db. When it comes to the sub, you need to adjust the sub's amp volume - it is not easy to measure, but see if you can it's sweep at the middle of +5. You then have your speakers balanced.

When you use REW, it's best to use the 80 scale as it gives more headroom.

Hope that helps.
Graham

**brucek** · **03-22-07, 07:55 AM**

Quote:

Turns out I just have to get some special weather-stripping or something...

Everyone with a capable sub has this problem. Picture frames on walls are bad too. They rattle like crazy until you put a small piece of something behind the bottom part of the frame where it touches the wall. My fireplace doors are also bad.

Quote:

Should I back my LFE down a notch or two? Or is having some red for a second ok?

Your OK. Leave it.

Quote:

you mentioned that the noise floor will increase with the +4 BFD setting, how do I test that?

This setting raises the entire input/output operating level of the BFD. Internally there's no real change. So if I feed a 1volt signal into the BFD, it will be 1volt (with no filtering) at the output, irregardless of the operating level switch.
But the -10dBV setting which has an operating input/ouput range of 0volts-1.25volts, would obviously be more sensitive to a very weak signal. If you have a strong output voltage swing from your receiver that clips this input, then you need to move to the next operating range. The test is whether you can make those LED's move in this higher range. You have satisfied this requirement.

There will be a small increase in the noise floor at the +4dBu setting, but it likely isn't noticeable. Simply turn your receivers volume down to zero. With the BFD and sub on, switch between the low and high operating range. Notice any noise floor change? If it's not objectionable, you're good. Either way, you simply have too much signal for the -10dBV range....

Quote:

I've tried to use the RS SPL for getting decible readings, but I'm a newb and don't know how to use the **** thing

You'll have to learn. Only use slow setting and C-weight.
Re-read what blue-max said below. You need to use the Radio Shack SPL meter initially (before REW) to set up your speaker levels. It's more important that they're matched at the same level, than what that level is. You do this with the receivers internal test tones. You adjust the speaker trims to match the levels of all the speakers except for the LFE sub trim that you've already set and shouldn't now touch). Its level is set with the sub amplifier volume. (I run my sub hot, as do many others and prefer the sub level higher than the rest. This is up to your ears)

brucek

**allredp** · **03-22-07, 11:48 AM**

You guys are good!

So, I'll get my 6 main/center/surrounds all matched tonight--I've done it before, but with the other tweaking I've done I should be sure. I won't mess with the LFE trim, as per Bruce's instruction.

In line with Bruce's comment about meter reading, I'm assuming that with a digital RS meter I am just getting them all to have the same number--whatever it be. E.g. if my normal listening level on the AVR is -36 and I turn on the RS SPL to 70 range, C weight and slow, as the test tone sweeps through each of the channels (sans sub), I adjust their individual trims to all equal the same number (it might be 68 or 69 if I recall in my case). That makes sense.

Graham's comment about the "needle" refers to an analog RS meter, right?

I can't wait to continue this tonight!

One more question for now: how does one calculate spl for extreme LFE? I hear people talk about getting 115db on a certain scene, or 112db on another, etc. Does the RS meter do that for you? If you could explain, I'd love to see what kind of numbers my PB12+/2 is cranking out for comparison!

Thanks again!
Phil

**lovingdvd** · **03-22-07, 02:56 PM**

Sounds like you have a Yamaha receiver?

At any rate as may have been covered I don't think you want to use the LFE -20 to 0 adjustment for LFE. Instead just use the general SUB level output.

Also as a side note - I use the opening scene in Start Wars III for the input level test. Right after the opening theme song and just before the first space ships are on screne there is very powerful bass that starts pounding in the sub.

Another scene I use to spot check the level is King Kong HD DVD I think around chapter 31-33 (somewhere in there). There are scenes when Kong is letting how huge grunts most of which is LFE. Nice!

**allredp** · **03-22-07, 04:10 PM**

Yes, I have a Yamaha RX1200 AVR--which is great, but I don't like being stuck with only a 90hz x-over for the LFE! I'm also suspect of the 80 wpc when driving all channels--my Dahlquists are rated up to 250wpc and I don't think I'm giving them enough stuff to sing like they should.

So, I guess I spaced/didn't know there was an LFE trim in the Speaker setup menu with all the other channel stuff. I just worked through the menu and found the #10 menu (if I recall correctly) that is called LFE level.

I'll look more closely at the earlier menus to see what you mean. Maybe that's the difference with my needing to use the +4 on the BFD instead of the usual/preferred -10.

I appreciate the demo insights also--I'll check those out soon.

Thanks for that help!

-- Phil

PS I'll also check out the noise floor as per Bruce's directions--I think I missed that in his earlier post.

Much obliged...

**allredp** · **03-23-07, 11:28 AM**

Quote:

lovingdvd wrote:

Sounds like you have a Yamaha receiver?

At any rate as may have been covered I don't think you want to use the LFE -20 to 0 adjustment for LFE. Instead just use the general SUB level output.

So, last night I went back through my Yamaha menus and can't find any "sub out" other than the #10 menu option (-20 - 0). Am I missing something?

**lovingdvd** · **03-23-07, 11:37 AM**

Quote:

allredp wrote:

So, last night I went back through my Yamaha menus and can't find any "sub out" other than the #10 menu option (-20 - 0). Am I missing something?

Yes you are missing something. In one of the set up menus you'll find input level controls. As you cycle through them you'll see options to add or subtract gain for the left front, center, right front, each surround, and finally the sub (which is the one you want to adjust for this).

Let me know if you still cannot find it and I'll go through my Yamaha menus to let you know where it is (although my model is different its likely in the same menu org).

**allredp** · **03-23-07, 11:45 AM**

I thought that's where it would be also, but when I cycled through all the other speaker's -/+ it comes to "sub" but only allows me to select between "sub", "main", or "both". There's no -/+ option there!

This is the 1200 (Yamaha is out with the 1700 now) and so it might just be too old to have the LFE trim with the other speaker sets.

As I mentioned earlier, this model also doesn't have a variable x-over point for LFE--it is stuck at 90hz only. Which really stinks, I think, because my mains are capable down to 30hz!

I'll have to upgrade at some point, of course...

**Wayne A. Pflughaupt** · **03-23-07, 12:32 PM**

Quote:

lovingdvd wrote:

Yes you are missing something. In one of the set up menus you'll find input level controls. As you cycle through them you'll see options to add or subtract gain for the left front, center, right front, each surround, and finally the sub.

According to pg. 24 in the on-line RX-V1200 manual, the sub isn’t included in the rotation – just the main speakers. That leaves the LFE option in the menu as the only alternative. It’s supposed to only work with Dolby Digital, which makes you wonder what's going to happen to your sub level when you switch to music or Pro-Logic for TV shows.

Regards,
Wayne

**lovingdvd** · **03-23-07, 12:33 PM**

Quote:

allredp wrote:

I thought that's where it would be also, but when I cycled through all the other speaker's -/+ it comes to "sub" but only allows me to select between "sub", "main", or "both". There's no -/+ option there!

This is the 1200 (Yamaha is out with the 1700 now) and so it might just be too old to have the LFE trim with the other speaker sets.

As I mentioned earlier, this model also doesn't have a variable x-over point for LFE--it is stuck at 90hz only. Which really stinks, I think, because my mains are capable down to 30hz!

I'll have to upgrade at some point, of course...

You are in the wrong menu. There's a sub menu somewhere called Levels. Forget LFE trim that is not what you are looking for. If you need further help finding it let me know I'm sure it is in your menus.

**lovingdvd** · **03-23-07, 01:23 PM**

allredp - here is exactly where these controls are in my menu (Yamaha HTR-6090 which is basically a clone of the RX-V1700).

MANUAL - > 1. BASIC - > B. SP LEVEL

Within SP Level you should have all individual speakers in there. If not make sure your speaker set is configured to show that you have a subwoofer in the system. Let me know if this helps.

**allredp** · **03-23-07, 06:26 PM**

ok, I've found the "level" button on my Yamaha 1200 remote. Here I can adjust the trim of all the peripheral speakers--center, sr/sl, rear center, and sub.

Turns out this is the same trim as the #10 in my "menu" options. It was at 0, and backs down to -20, just like the #10.

So, mystery solved!

However, like Wayne pointed out, there may be a serious issue when not in Dolby mode--though I haven't found this to be the case in listening to TV source material through my HTPC.

Thanks again for all the help!

**lovingdvd** · **03-24-07, 02:06 PM**

I made an interesting discovery today by accident. When I initially set things up I was sure to push the +4/-10dB switch IN so that it was set to -10dB.

HOWEVER, I didn't realize that there are actually TWO switched - one for input and one for output.

So I just realized that this whole time I've had the INPUT set to +4 db. The output was set to -10dB as expected.

This brings up the question - does this really matter? I'm assuming the answer is a resounding YES. If not, please let me know!

So my next step is to push the switch in for -10dB, and then bring my sub woofer output level in the receiver down accordingly.

My two main questions about this are:

1) Does it even matter (already asked above) if I was to just leave it the way it is?

2) Will it be necessary for me to fire up REW again once I change the levels and recheck for peaks and the filters (basically recheck the calibration)? If changing the levels would not really affect that, that would be good news as it is a bit of a pain to drag out the PC and set up all my equipment to use REW.

Thanks!

**brucek** · **03-24-07, 08:41 PM**

Quote:

HOWEVER, I didn't realize that there are actually TWO switched - one for input and one for output.

No. One for left channel, and one for right channel.

Quote:

Does it even matter (already asked above) if I was to just leave it the way it is?

Set it to -10dBV for each channel if you have a receiver where that matches the input level that feeds the BFD.

Quote:

Will it be necessary for me to fire up REW again

No, but be sure the RED LED(s) don't come on when playing loud levels. Just the Yellow LED(s) should come on when very loud passages are played. Adjust sub LFE output trim for this..

brucek

**lovingdvd** · **03-24-07, 10:38 PM**

Quote:

brucek wrote:

Set it to -10dBV for each channel if you have a receiver where that matches the input level that feeds the BFD.

How do I know if my receiver matches the input level that feeds the BFD?

Quote:

Adjust sub LFE output trim for this..

brucek

But isn't it more than just the LFE trim? Adjusting LFE trim would not reduce the bass that is redirected to the sub for all other channels set to SMALL, correct?

In this case rather than adjusting the LFE trim I should use the general sub woofer line level output control (just like is available for all of the 5.1 channels, no?

Lastly, is there really any difference here? For example if I have the receiver sub woofer output set to +6dB for the sub when the switch is at +4dB, does it make a difference if I set the switch to -10dB but then raise the sub output 14dB to 20dB?

Come to think of it, the sub outout is already around 7dB with the switch at +4db. If I move the switch to -10dB I will have to basically pin the output control for the sub output at 20d

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