Today I noticed amp gain wasn't at 100% and....

**Exocer** · **07-23-07, 11:50 PM**

I didn't notice this for at least a few weeks. The gain was about at about 75% (ep1500) so I turned it back up to max...and BAM (as willy said) things fell back into place...as if I completely re-calibrated my system and bought a new amp.

So for those of you out there with pro-amps in DIY sub duty make sure to check your gain setting every now and then. It has such a major impact on the sound that you hear

Learn from my silly mistakes..

Happy DIYing everyone

**Scott S** · **07-24-07, 01:24 AM**

Cool! Something to take into consideration being that I own a EP2500. So far I just have it bridged running my center channel...once I finish the dual 18's it will be ready for some sub action.

**Blaser** · **07-24-07, 01:56 AM**

It is not always necessary to have the amp gain at max... I have mine at 1/3 and my receiver subwoofer setting at min (-10 db). It depends on your input signal and amp sensitivity. If you're doing much BFD cuts...so yes you will propably need to increase your gain...

**Exocer** · **07-24-07, 07:54 AM**

blaser, you're right that it isn't "necessary" to have gain at max nor was I even implying that gain must always be set to max...but if it was initially setup to be at 100% gain (or even at 50% gain, wherever it works in your system)and it sounded good there but suddenly you notice a decrease in performance (a rather large decrease) maybe someone walking by accidentally turned down your gain. I am pretty sure I am the dummy who turned down the gain while cleaning up

so before you wonder if your sub is damaged or before boosting the LFE channel in your AVR to +5db it'd make more sense to check the gain on your amp first for any changes

good day everyone!

**Blaser** · **07-24-07, 09:13 AM**

Gotcha Friend! I understood your post

Why do you have such a high gain....can you remind me about your sub setup? Sorry, I don't remember quite well...

Have a nice day!

**Exocer** · **07-24-07, 09:18 AM**

My guess is the BFD cuts across the board in an attempt to flatten out the FR of the TC-3k, as you stated.

The sub in question:
TC-3k sealed, 3.9ft^3 enclosure
Ep1500 bridged @8ohms
BFD
HK AVR 235 (lfe for 2.1 music @ -2, -6 for DTS movie playback)

**Blaser** · **07-24-07, 09:44 AM**

Quote:

Scott S wrote:

Cool! Something to take into consideration being that I own a EP2500. So far I just have it bridged running my center channel...once I finish the dual 18's it will be ready for some sub action.

Bridged EP 2500 running a center channel

Where are you Steve to see what I'm seeing

(pun Intended!

)

**Exocer** · **07-24-07, 02:25 PM**

I do agree that it may be overkill to use an ep2500 for a center but its better to use that than an AVR's amp section

**SteveCallas** · **07-24-07, 09:20 PM**

Quote:

blaser wrote:

Where are you Steve to see what I'm seeing

Actually....uhhh....after the discussion I had with Ilkka about power and some facts he shared with me afterwards regarding the TC 2k LLT, I decided to set my own amp to bridged mono. Seems amp limiting may not be needed at all with a LLT, yet strangely some sealed alignments won't hesitate to bottom. And just for the record, no, I absolutely didn't notice any difference in sound quality, but I guess I have a couple more dbs headroom on tap.

**Scott S** · **07-25-07, 02:10 AM**

Quote:

Bridged EP 2500 running a center channel

Yup!

I wanted to give it (EP2500) something to do while I was waiting to finish the dual 18's...

First I had it running the front stereo pair of Adire kit 281's. Now I have it running bridged on the "original" Adire LCC. I dont have it turned up that loud to actually put out more the 100-200w. If even close to that.

**Blaser** · **07-25-07, 08:17 AM**

Quote:

SteveCallas wrote:

Actually....uhhh....after the discussion I had with Ilkka about power and some facts he shared with me afterwards regarding the TC 2k LLT, I decided to set my own amp to bridged mono. Seems amp limiting may not be needed at all with a LLT, yet strangely some sealed alignments won't hesitate to bottom. And just for the record, no, I absolutely didn't notice any difference in sound quality, but I guess I have a couple more dbs headroom on tap.

How much power were you using, and how much now?

**SteveCallas** · **07-25-07, 11:36 PM**

Was running one channel at a claimed 600 watts, now with it bridged it's a claimed 1800 watts.

**Blaser** · **07-26-07, 01:22 AM**

That's a pretty "aggressive" change.... I am sure you have a simulation of cone excursion. Can you pls post it?

Thanks!

**Blaser** · **07-26-07, 06:56 AM**

**Blaser** · **07-26-07, 07:00 AM**

Quote:

yet strangely some sealed alignments won't hesitate to bottom

Why Strangely??

"the excursion limiting factor" used in the LLT is removed, and appearantly on program material, it will require less power for a sealed alignement to bottom compared to an LLT

.....Nevertheless (IMO) it will still not bottom out (on program material) as per similation

... but ok faster than LLT.

By the way, I don't think "amp limiting factor is not necessary in LLT at all". I think it is, and what you have done is great, the amp limiting factor is still very important, but it is not as soon as the simulations (based on single frequency) will show... maybe twice, or three times this value, this is what is to be experimented (of course that would be impossible to determine theoretically). The other thing is that from what people are posting, amps will not deliver what they are rated by the manufacturers, and so this might be another factor.

Nevertheless enjoy your new configuration and let us know how mean you are with the driver!!...

**Blaser** · **07-26-07, 07:04 AM**

Quote:

SteveCallas wrote:

Actually....uhhh....after the discussion I had with Ilkka about power and some facts he shared with me afterwards regarding the TC 2k LLT, I decided to set my own amp to bridged mono. Seems amp limiting may not be needed at all with a LLT, yet strangely some sealed alignments won't hesitate to bottom. And just for the record, no, I absolutely didn't notice any difference in sound quality, but I guess I have a couple more dbs headroom on tap.

This type of behaviour from a so knowledgable person like you are.... is something that only makes me feel more and more respect for you

**SteveCallas** · **07-26-07, 09:19 PM**

Well I get back to Ilkka's comments about his testing - he ran his amp to clipping on the TC2k LLT, and it is supposed to be able to pump out ~2000 watts. He mentioned that he was unsure whether the driver bottomed in the 20-30hz range or if it was just the amp clipping, but either way we can say that 2000 watts was basically the point at which nothing beneficial could any longer be extracted from the driver. So I ask myself how did this happen (a lot of it we discussed in that previous thread)? Logical ideas mentioned were that the xmech on these type of high excursion drivers is quite a bit higher than the xmax, and that is true. Also, the suspension itself will begin to resist excursion a little bit beyond some unknown point.

I have never really been concened with bottoming a LLT below tuning due to a combination of electronics rolloff and the output levels demanded by movie scenes at such low frequencies, but I have worried about the range just above tuning. This is where the driver is still behaving almost identically to a sealed sub and excursion use can get quite high, and this is where I based amp limiting on. But I guess the combo of high xmech and suspension resistance beyond some point are enough protection in that range, making a LLT pretty bulletproof altogether. Ilkka also mentioned that you should be able to hear the driver in distress when it begins nearing xmech.

Then yes, there is the claimed vs actual amp output specs. While I really appreciate and admire the amp testing work Chuck has been doing at some other forum, I don't find it to be all that useful for actual subwoofer material usage. We don't sit and listen to 30 sine waves, music and movies are short burts of various frequencies. The amps he is testing can pump out a lot more clean power over shorter periods of time, so for real world usage, I'd say they can do even more than what they are rated for. His testing is more to see if the amps meet the claims of the spec sheets.

**Blaser** · **07-27-07, 05:37 AM**

Very well said Steve....as usual. I also have to mention that Ilkka's tests (if I am not mistaken) are based on single frequencies, so even on program material (unless listening to sin waves as you said) it will be even harder to bottom out the driver.

**Exocer** · **07-27-07, 06:32 PM**

thy,
thanks a lot for you words of wisdom

**SteveCallas** · **07-27-07, 08:39 PM**

But again, those types of tests don't reflect the playback of real material. In reading Chuck's methodology, it is basically a torture test.

Also, brucek just brought up an interesting point in another thread, about setting the excursion in WinISD Pro to rms as opposed to peak. Excursion usage decreases significantly and is probably a better representation of usage with actual material as opposed to sine waves or continuous tones. Basically the same thing with how the amps are tested.

**Exocer** · **07-27-07, 09:34 PM**

Quote:

thylantyr wrote:

Do you design a sound system to accommodate the worse case or do you just settle for
'easy listening' playback?

Designing for both situations seems to have its place in the market...depending on budget and listening habits etc, IMO

I'd much rather have a system ready to tackle the worse case scenario since I like high SPL's. With only 1350ft^3 of sealed space to fill things can easily get overwhelming with an ep1500, and a500 barely working at their peak

**brucek** · **07-27-07, 10:02 PM**

Quote:

I'm sure if you look hard you can find tons of playback that has continuous playback, but those are
occurrences are not 100% of the time. It just so happens when it does occur, the woofer
and amp starts to barf and you notice that something is happening. hehe

Yeah, I suppose there's lots of synthesized continuous low frequency information that occurs in movies just to create mood. So often, when I'm watching a movie, the room just starts to shake with some low frequency sound that the movie soundtrack is producing just to create a creepy feeling. I guess if it occurs around max excursion frequency, you should be ready.....

brucek

**SteveCallas** · **07-28-07, 12:02 AM**

Ehhh, I gotta disagree. Aside from the movies Crank and possibly I Robot, I haven't seen much resembling a continuous, solid tone or a sine wave in a movie. Thy or bruce, feel free to post some Spectrum Lab measurements if you believe there are more....I just haven't seen or heard very many scenarios like that.

I did chart a lot of music a while back and the closest I saw resembling a continuous tone was a Boston Acoustics "woofer cooker" bass demo song, see attached. Sub and amp handle it with ease though.

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