[mayhem13]

Ok, a quick synapse of the system performance and design results.


$750 per pair including drivers and crossover components

Bass extension to 60hz +/-10hz -3db

Stand Mountable

Maximum enclosure width 12"

Sealed bass alignment

3way design

117 db peak output capable per pair.


So the next logical question is efficiency. Those voting really need to read the above recap before spitting out obscene numbers as they might be outisde of reality given the recap data. If you choose a very high efficiency, please post your reasons and how we shoudl go about reaching those numbers. Those that choose to argue the point that efficiency should have been chosen earlier i pose the age old question...Which came first, the chicken or the egg. If you can answer that then i'll conceed your point. If Not...zip it!

SPL units are 2.83 Vrms at 1M

 

[LTD02]

the egg came first.


some reptiles evolved into birds.


reptiles laid eggs long before birds existed.


ergo, the egg came first.


efficiency generally declines with frequency, so you really should qualify your post with at what frequency you want to measure efficiency.


at 60hz, ae td15m's (sealed) are around 92db efficient, at 120hz, they are pushing 98db efficient.


so, if i think ae td15m's (sealed) are good enough, should i vote 92 or 98? ???

 

[penngray]

lmao

Does this poll really matter? This isnt a Chicken or Egg question for me.....All the other polls kind of dictate what drivers we are going to be buying already, no?


Who is going to vote for 85-88dB anyways??? or even under 90dB

Then again, the polls have shown little continuity in the past

Lol, someone already voted under 90dB

That wasn't too shocking

Now someone is going to argue they have a specific driver in mind and its 89dB or that sub 90dB drivers are better

 

[LTD02]

hey penn, i'll argue a point for the other side, even though i prefer max efficiency.


low efficiency often arises from lots of physical damping of the driver. this can help provide for a flat frequency response. some may even find the "crushed" dynamics of such drivers pleasing.


this would be an interesting area for research, sean olive, are you listening? ;-)

 

[Looneybomber]

I don't know if I can vote. I think we have enough parameters to dictate an efficiency.


I think we should just come up with speaker designs given our picked criteria. Maybe pick out a set tweeter or pick out the woofers? From there, match the other drivers around that, but that which falls within our already established criteria. Once it's all done, we will then know what our sensitivity is.


F=MA. If I have MA, I can't also pick my F can I?


Ahh, well, I'll pick something realistic.

 

[cc00541]

This is a good point. IMO, if the choices are for system sensitivity, then it should be the average over the speakers intended pass band of 60 Hz to 20K. Keep in mind that the woofers ultimately chosen will have to overcome baffle step compensation and provide the expected f3 at a reasonable impedance. Consequently Hoffman's iron law becomes an issue, and the woofer choices will ultimately drive the system sensitivity.


If you want 98 dB system sensitivity, and you assume 4 dB of baffle step, then a single woofer would need to be 102 dB USPL or a pair of woofers in parallel would have to be 96 dB USPL each. Set your sights too high, and finding a woofer to meet the design constraints will be improbable at best. Set them too low, and the power requirements to obtain the max SPL will be in the kilowatt range. -It might be time to explore some potential woofer candidates that meet the other design criteria.


C

 

[zero the hero]



Quote:
Originally Posted by LTD02 /forum/post/16851970


hey penn, i'll argue a point for the other side, even though i prefer max efficiency.


low efficiency often arises from lots of physical damping of the driver. this can help provide for a flat frequency response. some may even find the "crushed" dynamics of such drivers pleasing.


this would be an interesting area for research, sean olive, are you listening? ;-)

Is there proof that lower efficiency drivers have "crushed dynamics" as opposed to higher efficiency drivers? Or is it just a question of needing more power to provide equivalent dynamics?

 

[penngray]



Quote:
Originally Posted by LTD02 /forum/post/16851970


hey penn, i'll argue a point for the other side, even though i prefer max efficiency.


low efficiency often arises from lots of physical damping of the driver. this can help provide for a flat frequency response. some may even find the "crushed" dynamics of such drivers pleasing.


this would be an interesting area for research, sean olive, are you listening? ;-)

alone this topic would be a good one but there is nothing to be gained from this poll. Only more restrictions that will further hamper your project. Considering all the other restrictions I would want the full set of drivers to be available to choose from.


You are seriously painting yourself into a corner.

 

[LTD02]



Quote:
Originally Posted by zero the hero /forum/post/16852223


Is there proof that lower efficiency drivers have "crushed dynamics" as opposed to higher efficiency drivers? Or is it just a question of needing more power to provide equivalent dynamics?

good question.


if, *all* other things are equal, the lower efficiency driver will have greater power compression at every spl.


example: assume 1 db power compression per 10 watts, 2 db per 10 watts, and 3db per 100 watts, for both speakers.


for an 88db speaker:

that would mean 1 db compression at 98db, 2 db at 108db, and 3 db at 118 db.


while a 98db speaker:

that would mean 1 db compression at 108db, 2 db at 118 db and 3 db at 128 db.


assuming, of course, each speaker could handle such high power and not be limited in other respects.


the other respects are important as well. there are boatloads of folks who swear by high efficiency designs and there are even boards dedicated to the topic. while i am not sure how to measure it, it seems that much more 'detail' comes through in high efficiency designs. as a result, high efficiency designs are often described as being more live, more open, or more realistic, even if their frequency response is not quite as flat as their low efficiency counterparts.


my guess is that this effect arises from the fact that we are far more sensitive to spl levels than many people think and that very minute changes in spl can make a subjectively large difference in subjective listening preferences. however, my own experiments don't back this up. listening to the same music with an increasing level of compression doesn't result in widely varying subjective results. so, maybe there is something else at work.


sorry, but that is the best answer that i can offer.

 

[LTD02]

on additional thought, another theory may be amp clipping.


if the more efficient driver clips less, that could have many benefits.


maybe we are very sensitive to square wave distortion. highly sensitive speakers minimize the probability of square waving the signal and so subjectively sound much better.


like i said, i don't know.

 

[zero the hero]

interesting replies. Certainly better explained theories than I've heard in the past, but there are still some assumptions there, right?

 

[mayhem13]

I guess i should have been more clear on the topic, but the poll assumes the woofer section and BSC. As many of the discussion threads talked about the inefficiency of hifi woofers. It's all kinda moot now as the 92-95db efficiency choice is the clear favorite early on, i expect it will remain throughout. It's an easy target to hit IMO. If over 95db becomes the favorite, i'll start figuring a way to get out of the corner or as some of you expect.....wave the white flag of defeat.

 

[LTD02]

may i suggest that any vote without a frequency qualification be excluded because such voters clearly don't understand efficiency?


;-)

 

[mayhem13]



Quote:
Originally Posted by penngray /forum/post/16852269


alone this topic would be a good one but there is nothing to be gained from this poll. Only more restrictions that will further hamper your project. Considering all the other restrictions I would want the full set of drivers to be available to choose from.


You are seriously painting yourself into a corner.

Any design is going to have limitations from the driver selection pool, so i don't understand your logic here. There's definitely something to be gained from the information gathered here and it's fundamental. To reach the target output goals we arrived at, a system with 87db efficiency would need gobs of power to reach those levels, and for some would mean a major expense for amplifiers/AVR upgrades.


So much negativity for one thread, makes me want to read a self-help book or something.

 

[mayhem13]



Quote:
Originally Posted by zero the hero /forum/post/16852791


interesting replies. Certainly better explained theories than I've heard in the past, but there are still some assumptions there, right?

Nice for a change, isn't it?

 

[mayhem13]



Quote:
Originally Posted by LTD02 /forum/post/16851933


the egg came first.


some reptiles evolved into birds.


reptiles laid eggs long before birds existed.


ergo, the egg came first.

The question pertained to chickens, with no mention of reptiles, ERGO you have failed to quantitatively analyze the question, therefore your answer is incorrect. No soup for you!

Not exactly a soup question though, and not apples and oranges either. Evolution has little to do with these discussions so i'll move on now.

 

[zero the hero]



Quote:
Originally Posted by LTD02 /forum/post/16852826


may i suggest that any vote without a frequency qualification be excluded because such voters clearly don't understand efficiency?


;-)

Unless I'm way off base here, isn't efficiency normally specified after BSC? What's the point of claiming a speaker is 97db/2.83 when 6db is going behind the speaker?

I realize full BSC is usually too much for the average room; that was just an example. I can't imagine people not realizing that though. In fact, isn't there like an unwritten rule to use 1khz?

 

[cc00541]



Quote:
Originally Posted by LTD02 /forum/post/16852327


if, *all* other things are equal, the lower efficiency driver will have greater power compression at every spl.

True as far as it goes, but one certainly cannot assume all high efficiency drivers have lower compression than their less sensitive counterparts.


As the amount of current passing through the voice coil increases, its temperature rises, and with its positive temperature coefficient, so does its resistance. This is a slow process where the voice coil is heated up to the average power dissipated, not from transient peaks, although there will be thermal cycles with some source material. I have seen studies that suggest Re might increase by 10% for a typical driver. I build some 'thermal fudge factor' into my designs, but much also depends on the motor design. Aluminum formers, voice coil material, and venting under the spider or pole piece can significantly improve the voice coil heat dissipation. The statement that a more efficient speaker suffers from less thermal compression cannot be truthfully made without considering several other aspects of the motor design.


IMO, of much more significance is the compression caused by part of the voice coil leaving the gap, or the non-linear effects of the spider and surround compliance. These are instantaneous and affect the cone movement every time it reaches the limits of its excursion. These compression effects are thermally and efficiency invariant, and can cause much greater distortion than the more easily controlled thermal effects.


C

 

[penngray]



Quote:
Originally Posted by mayhem13 /forum/post/16852848


Any design is going to have limitations from the driver selection pool, so i don't understand your logic here. There's definitely something to be gained from the information gathered here and it's fundamental. To reach the target output goals we arrived at, a system with 87db efficiency would need gobs of power to reach those levels, and for some would mean a major expense for amplifiers/AVR upgrades.


So much negativity for one thread, makes me want to read a self-help book or something.

so if the poll said use a 87dB driver, you would ignore many of the 90 or 95 dB drivers that would fit the needs of all the other polls??


That is what I call painting yourself into a corner and even though the poll results look okay now what does 92 to 95dB really mean either? What if there is a 90dB driver that works perfectly if you are using 2 of them? You can not seriously say you will only pick drivers that are 92 to 95dB

I just think this poll is meaningless towards a successful design. That is not being negative that is just being honest, sorry.

 

[mayhem13]



Quote:
Originally Posted by penngray /forum/post/16853109


so if the poll said use a 87dB driver, you would ignore many of the 90 or 95 dB drivers that would fit the needs of all the other polls??


That is what I call painting yourself into a corner and even though the poll results look okay now what does 92 to 95dB really mean either? What if there is a 90dB driver that works perfectly if you are using 2 of them? You can not seriously say you will only pick drivers that are 92 to 95dB

I just think this poll is meaningless towards a successful design. That is not being negative that is just being honest, sorry.

If two woofers in a parallel circuit yield 93db with BSC, then yes, single 89db efficiency rated woofer would be offered in pairs. I think you're reading way to deep here. One possible config for a three way would be a WMTW (get it

) with two midwoofers, a single mid driver and a 1" dome. Easy 92-93db target efficiency reached.


92-95db means just what it says. If driver a has a an efficiency it the pass band of the design of 90db, we'd need two of em. That's why your VT-3's have two woofers.