AESpeakers TD Series group buy!!! - Page 13

Oops, I guess that was me. I should go back and edit it.

I would say the 10w amp would be fine on horn top's running ~105-110db sensitivity.

I guess you guys listen more loudly than I do if your mains are hitting 110db peaks. I generally listen a few ticks below reference at most and try to spec out to reference at the LP.

For music that is extremely dynamic like well recorded classical music, most people listen at a lower average volume and get a similar peak SPL to other more compressed content.

The bottom line is YOUR system should be designed to reach YOUR maximum spl. Anything more than that is, as you pointed out, a paper weight.

But, I admit, it still bothers my sensibilities(or perhaps my insensibilities) to hinder the capabilities of a speaker with inadequate amplification .

The problem is that Scott has truly inadequate amplification now....NONE! It doesn't get much more hindered than that. I was trying to give him a super cheap stop gap option before he can secure the amps he wants to run.

I did overstate the 10w. I also underestimated how crazy loud some people listen.

most people here are dealing with some sort of hearing loss, due to years of abuse. though they might not realize it.

Then you are listening a good 5+db OVER reference level, because "zero" on a disc equates to a max transient SPL of 105db.

As I said, I totally agree. There's nothing wrong with compromise, so long as the limitations are understood.

Well, that isn't very encouraging news! Is this the same design that John Sheerin posted on DIYaudio? I should probably just go sealed as originally planned anyway; perfect match for the 4 2-driver IB manifolds.

Funny reading the excuses about lack of progress on the HT projects. I can whole-heartedly identify! My biggest excuse for lack of progress is I really wish my room was larger than the 12x24 that it is. But everytime I ponder the possibility of an addition or consider selling the house and rebuilding, the reality is the cost-to-benefit ratio is really ****** for the added square feet.

As for the amp debate, I'm sure cheap low power amplification would provide quite a few dB and sound just fine doing it in Scott's system. Not what he would probably want for a long-term solution, but how much power is really 'needed'? Totally subjective, but obviously DIY guys tend to lean towards the overkill side of things.

Over a period of years I've aquired 8 QSC DCA-series amps -- (5) 1622, (1) 2422, (1) 3022, and a 1644 -- for power in my theater, but why in the hell do I 'need' to have 15k watts on tap to power compression drivers, hugely efficient 15" midbass, and 15"/18" IB drivers in a 300 square foot room? Kinda boggles the mind. So in a concession to practicality, there are 2 Emotiva LPA-1's slated to do the job instead. Hopefully the noise floor issues Doug had won't be as bad in my room...this option seems much more sensible than a huge cool looking rack full of 8 highly respected QSC pro amps with unlimited power reserves on tap...(er, um, wait a second here...)

Well, its an Audyssey Pro calibration with confirmation of its accuracy with Omnimic. Mixes are calibrated using weighted SPL measurements and brief, transient peaks are there but are not captured due to averaging. It is a misconception that there are no peaks above 105 dB in reference mixes. Omnimic measures peak SPL as well and that measurement is different, and higher, than the weighted measurements.

Quote:
Originally Posted by noah katz View Post
You don't think 30 W is enough for a 100 dB/1W CD (assuming active XO)?


With 100 dB/W (includes CD compensation BTW) gives the same headroom as a 90 dB/W speaker and a 300 W amp.

Not enough for subs, but that's for only the top 5 octaves; when people say they hit 120 dB peaks most of that is from the lower octaves.

Also active XO greatly increases clipping headroom because the voltage waveforms of low and mid/high freq are not adding.

I'm curious how you took the measurement. Were you able to eliminate all LFE content? The LFE track is mixed with an extra 10db of headroom. That might have caused the higher than 105db reading. Simply turning off the LFE channel might not cut out all LFE content because your processor may redirect the LFE track to your mains.

I'm far from an expert on movie mixing standards. Your assertion could be true, I don't know. It was my understanding that higher than 105db was not possible from the non-LFE tracks.

You are "calibrating" the 100dB/W audio system to offer the same crummy
SPL levels of the system that operates on 300 watts of ampification with
90dB/W speaker.

Lets use the same approach but backwards.

If I had a 90dB /W speaker system, I would be designing it to have about
10,000 watts of amplification to get the large clipping headroom that I desired.
(roughly 300v headroom @ 8 ohms), which in turn about 1000 watts of
amplification on the 100dB/W system to get the same SPL levels.

Why stop there? if you horn tweeter is 110dB /W rated, why not use a 3000 watt bridged pro amp ? It's not like the cost is going to break the bank.

You have these new class D amplifiers in the $400 - $600 range, why not use it?

Granted, go back 20-30 years this option may have not existed or it was too expensive, but not today.

go big!

Here are the results of SPL measurements using Omnimic from the opening salvo on the Master & Commander: Far Side of the World Bluray. Reference level Audyssey Pro calibrated system, C-weighted and slow at my MLP:

5.2 (All channels)
Peak - 121.9 dB
Max - 108.6 dB
Min - 54.4 dB


Sides only + subs
Peak - 118.8 dB
Max - 109 dB
Min - 51.8 dB


5 Channels, No Subs
Peak - 115.4 dB
Max - 100.8 dB
Min - 51.4 dB


Sides only, No Subs
Peak - 111.8 dB
Max - 97.4 dB
Min - 53.2 dB


The sub amps were simply turned off for the "No Subs" measurements.

No, I'd use the above with 120 W driving 97 dB/W mid/woofers and 3 kW driving relatively efficient subs (Danley DTS-10 and a pair of Mael-X18's).


Why not stop at something even remotely approaching rational?

When there's a known finite maximum signal that can be recorded on CD/DVD/BD, how is a large amount of clipping headroom on an amp better than a few dB?

This can't be a serious statement...is it?

You have to enter my world of audio to get it.

Stick around here, no progress is made

I don't stop at stop signs.


You are talking about the end of the road. I'm talking about the difference
between the starting and ending of the road. Relative, not absolute. If I move the starting point further, then add the same delta, the end of the road is extended. That my riddle for now.

You can't extend the road w/o redefining the max signal available.

Going far beyond the end is just a waste, except for bragging rights.

I'm curious if you had any of L/C/R or sides set as large and if your LFE channel crossover was below 120hz. If so, some portion of the 115db max content from the LFE track (not .1 sub channel, but .1 content on the Bluray) would be redirected to those speakers. This could cause your higher reading.

You did notice some people here are also having success with higher powered amplification driving the tops. Either I'm crazy and people are catching my disease or others are getting it too ?

Specifically, Scott's setup will be >100db sensitive for both the woofer and horn.

Let's set it up for THX reference which is 85db with 20db transients. This is loud by most sane standards.

@15ft with his 103db LF section he would need ~.17w to reach 85db. For the 20db transient he would need ~17w. Mind you, this is with only one speaker playing.

[Agreed, but this is also with a single tone signal, not a multi-tone excitation which requires more power, are we talking about pink noise here, or actual music or movie content? Also keep in mind that voltage and current limits in small amps can also cause weird behavior when pushed close to their limits. ]

Rod Elliot ( ESP ) has an explanation on bi-amping and other topics here: http://sound.westhost.com/bi-amp.htm#power_dist

I don't know how sensitive your speaker is or what levels you listen at, but I highly doubt Scott would need the 425w you are using on your HF section. That would give him ~120db at the LP.

[The woofers are 100 db/1m each, boxes have not been built yet, although most of the parts are in house. In the above paper, extrapolating from the chart, with a crossover in the 700-800 hz region, about 62% of the power is in the bass region, around 38% above that.

With 1675 watts on tap, that would work out to around 74.6% of the total power available for the bass region, below the 700-800 hz region, with 25.4% of the power allotted for the MID / HF. Close enough for gov't work.... . ]

Scott is free to make up his own mind, on what he wants to use, I never said that small amps wouldn't work adequately for most people and situations. It sounds like he wanted to go with big LG clones, however, some amps are better than no amps.

Also, keep in mind what Rod mentioned, I quote " The average SPL at the listening position cannot be determined without complete analysis of the room's acoustics (for a typical room you will lose another 6 to 10dB), so for simplicity we will use the 1 metre SPL as a reference value.


Are you listening at an average of 90db with 30db peaks? Even with compensation, the BMS coax CDs are at least 103db sensitive right? Are you listening at 100ft?

My requirements are a bit different than most, but let's say I desire more than 130db@1m out of one speaker. No, I am not listening at 100 feet. Yes, the BMS drivers are quite sensitive, BMS rates them at 118 db/w/m on a 40x20 deg horn, my horns are 50x60 deg, so a bit less DI, maybe 116-117 db/w/m without any compensation. No, I have not measured the sensitivity on those horns.

Of course, there is nothing wrong with that extra power and I would want around 3-6db of headroom, but I don't see any use for 15db of headroom. I'm not recommending the DTA-100's as a final or ultimate solution, just a stop gap.[

Sounds like we mostly agree, but again, I desire a bit more headroom than most people.

Why shoot low and build a system for THX reference when you can do more ?

All speakers small and LFE at 120 Hz. As to content being redirected from the LFE track to the speakers, I've never heard of that. The LFE channel setting is not a crossover, so there should be no redirection anywhere.

The misunderstanding in regards to "reference" level stems from a misunderstanding as to how the 105 dB number is measured. The measurements used to set the 105 dB digital "ceiling" by the sound engineer is both frequency weighted AND time weighted. The time weighting is the "fast" and "slow" on the SPL meter. AFAIK, the standards are C-weighted Slow using a bandwidth limited pink noise (500-2000 Hz I believe). This is where the confusion occurs.

Peak SPL is an instantaneous measurement with no time constraint applied, whereas Slow or Fast are time averaged and better represents the overall power of the signal as it relates to hearing damage. As well, bandwidth limited Pink Noise does not replicate the energy distribution of many signal frequency distributions which causes the Peak SPL to often not align with the time averaged SPL.

So bottom line is that the 105 dB reference level is NOT a ceiling on instantaneous SPL, or brief transient peaks, but a ceiling on time averaged SPL. So instantaneous peaks can and do exceed 105 dB and the amount of dB those peaks exceed that number is dependent on the signal being reproduced.

hmm...ahhh....

can we get some models going for a TD12M?

i need an active design for TD12M, DE250, and SEO 12 that's going to rock my room.