Sloped baffle

Here's a simple un-tweak that may have helped just a little tweak (pun)... dunno.

For the longest time, I lifted the back of my speakers so they tilted forward. Here the old thought process:

My listening position is below the level of the tweeters. The speakers are about 44 inches high and my listening position is about 10 feet back. But my couch sits very low. I thought that by tilting the speakers forward, the tweeters would beam directly at me and treble would be improved.

Here's my current thinking, courtesy of this thread:

Lifting the back of the speakers as described may have augmented treble response, but the tweeter voice coils are even more forward of the mid and woofer driver voice coils than before the tilt forward. So ... to the extent there was time incoherence before, I'm just augmenting it.

So, at the expense of maybe losing a little treble, I attenuated an already non-optimal time incoherent situation just a tad.

Bottom line: it's probably in my head, but I think the speakers sound a little better. Little less bassey, a tad more coherent and invisible.

Btw, a couple of weeks ago, I switched back to the 4 ohm taps on my amp. There's definitely a noticeable change in coloration because the output impedance off the 4 ohm taps is lower -- and output voltage regulation is tighter. Bass is tighter and more extended. Upper mids/low treble are less bright.

But I also think the amp is "happier" with the load presentation because a good part of the speaker's power delivery demands are in the bass/low midrange region which specs at 4 ohms (70 Hz to 700 Hz). IOW, better impedance matching with the amp where it counts the most.

Still want to check out the DEQX.

Cheers,

BIF

You are quite welcome.
I know what I write doesn't pose questions to you all. Instead, I've mostly laid out the facts and some science. It's up to you to use those to develop your own questions. This is how I proceeded back in the early 1970's, by reading all of the AES papers and many others on speaker design in old and current magazines, on acoustics, studied basic physics, calculus, and psychoacoustics. Later, I returned to university to master all the math, and to learn more about how materials behave when vibrations exist and when electromagnetic fields pass by/pass through.

Sometimes I would find an error in the logic or math of someone's research paper. Usually, I used a paper as a springboard, expanding upon the author's thoughts and test methods, to better look at 'something' in detail.

To choose that 'something' to examine, to fix, or even to ignore, I first had to understand the very basics of WHY and HOW that 'something' would be important to what we hear, and then learn WHY and HOW 'it' occurs. This included how and why cabinets vibrate, cones break up, critical damping is achieved, a tweeter can fail to move on very tiny sounds, the air itself distorts... countless questions.

The most important ones are addressed in the Audio Engineering Society's Audio Anthology 3-book set.
Also, one should get The Audio Cyclopedia, even a twenty-year old copy. It is full of important info on acoustics, speaker design and recording methods, found nowhere else. Make sure you get one that's not falling apart in its binding.
Another book, out of print, is Elements of Acoustics by Temkin. You need to know calculus to get the most from it, but it's readable without that.
Finally, the Theory of Sound by Rayleigh, from Dover Press, is exactly like reading Isaac Newton's original papers. Get both volumes one and two, first published in the 1880's.

If you are interested in design but will never build your own speakers, these books are full of the very best information found nowhere else, and are written well enough to make for good, casual reading.

In these books, you get to see how others approached issues and usually find out WHY they did, along with what had been tried before then and WHY.

Knowing WHY is the most important factor in making better speakers. I can tell you most current speaker designs say to me that their designers know no more than what was mastered by 1979. If you read over the topics presented in those AES books, you'd see this for yourself, darn it.

At this point, I see nowhere on the internet any guidelines on how to select the proper woofer, etc. While I cannot help you directly with that, I can point out the principle differences in the drivers you selected, and leave you to have a good weekend!

- The Classic Scanspeak woofer has ALL of the right numbers for a sealed box. I wish it were more efficient.
- The more expensive Scanspeak woofer will not go as low in its proper sealed box. And unless you are stroking the heck out of it (not likely), it has no less bass distortion than the less expensive Scanspeak. However, it would be very slightly clearer in the lower-voice, high bass range. But then it goes nuts above 1kHz, all from its harder cone. Its first resonance at 1kHz is from its heavier rubber surround bouncing back, like a ripple in a flag, and then vibrating the cone running around its rim, like a church bell's 'first mode' of ringing `round-the-mouth vibration. The big spike above 1khz is its harder cone ringing like crazy.
- The Accuton woofer is a lot of $$, has high bass distortion, and will not go as low as the Classic Scanspeak.

- The Accuton mid driver has many wrong numbers and is not quite efficient enough.
- The Scan mid has the right numbers, its cone breakup is under control, and it has a vented suspension like the Scan woofer. Cross it over at ~300Hz. Read my Continuum 3 and Calypso speaker design papers for more info on using a mid.

- The only ribbons worth using, for sonic quality and which will not break for our purposes, are from RAAL. Excellent products, the best by far. You will need to create a Zobel to offset its inductance. Cross it over at 3kHz. Use their smallest model, for the best highs.

- I advise you fade in the subwoofer(s) below 40Hz, leaving the main three-way to run 'full range'.

So now you face a zillion other questions. Get the AES books above and the Audio Cyclopedia at the minimum for both guidance and answers, compared to the Loudspeaker Design Cookbook.

The Acourate approach is not right. I advise anyone hopefully learn what 'the numbers mean' for any driver, then use the parts I like above to fine-tune your own passive crossovers, with woofer mid and tweeter in their own boxes so you can move each one back and forth.

- You only need to build one speaker, as I posted before.
- You need a $100 voltmeter, a $200 fairly-low-distortion sinewave generator, a decent measuring mic with preamp, to run into some kind of third-octave spectrum analyzer for looking at pink noise.
- And a pocket calculator (scientific), especially to calculate real "L-Pads" for mid and tweeter using the best wire-wound resistors.
That's about it for tools, IF you go through the AES books.

When 'designers' do not understand in depth the extensive research from the past, they rely upon digital test gear. And then get many wrong answers since they do not understand 'the basics'. They have purchased an expensive tool that does not help solve the real problems. But they don't know-- they just stick a mic up in the air and tweak their crossovers to 'get the right curve' for each driver, which is soooo wrong.

And then they hear something 'not quite right', to then tweak the circuits by ear, so their favored recordings sound 'right'. And of course then brag about how carefully their gifted designer listened, how much money they (Revel/Harman) spent on a robotic speaker-comparison room or anechoic chamber (Paradigm/Canadian government). Hey, this isn't the space program where people get killed. This is an unsupervised field of endeavor, with no university program for it, requiring money more so than any real technical education. They always claim, "Well, we all just hear differently." Pooh.

And do get rid of/prevent any cabinet reflections for your mid and tweeter (get the mid's box away from the woofer's and tweeter's boxes, vertically). Put wool felt near the tweeter's dome.

Hope this gives you food for thought!

Best,
Roy

Roy, do you think my "un-tweak" re tipping my speakers back could have attenuated my speakers' time incoherency as I described above? Or is it just wishful hearing?

You are looking to reduce your time incoherence, is how I would say it. And yes, moving the tweeter closer may have increased your Paradigm's incoherence. But the only way to tell is to have a friend help you swing, quite literally, an arc between where your ear is and the location of where each driver's cone or dome meets its voice coil. Those should lie along the same arc.

Because you must keep the string or tape measure pulled tight, you would find you cannot just hold that string against your ear. I recommend you tape a dowel rod to a camera tripod, to mark your ear's location.

Also, get out your calculator to find out how far you are off axis. However, do not listen for tone balance, but for 'depth', for each instrument and voice to appear more and more whole, right there in front of you. The opposite is the tweeter and woofer becoming audible on their own, audibly separated away from the mid. The mid's tone range must be our reference point for someone's location, because that's the main tone range we hear every day.

It has been proven to very many people's satisfaction that the ear is not as sensitive to variations in frequency response as we would like to believe- not to say a flat response is unimportant. However, this must be true, as we never get to hear 'the best frequency response' from any source in real life, because we are never in 'the perfect spot'.

However, when you do get the Paradigm speakers into the right tape measure position/arc, the sound may be worse, because that is not 'the position' they intended. So again, always trust your ears.

In that case, have your friend tilt your left speaker back and forth while listening to Diana Krall's voice on just that left speaker. But not in mono. Her well-recorded voice is already in mono, because she and her piano were panned to the center, which means she and the piano are equal in left and right channels. You do not want the distractions of left-right information, but only the depth info and to hear a sharper focus on her voice, which one speaker can deliver.

Best,
Roy

Hey Roy.

Surely enough, I have a gazillion questions, but I won't keep asking! Well...not the gazillion anyway :-)

Thanks for the names of the publications worth reading. I am in the process of getting the first AES papers to get started. Being in Argentina doesn't help in sourcing!!

I do want to ask back about two specific comments you made:

1) why do you advise to cross over the subwoofers at 40Hz? Wouldn't the Classic Scanspeak driver listed above, for example, have an easier time if it had to reproduce down to 60 or 80Hz instead of 40?

2) you state "the Acourate approach is not right". But WHY? I'm following you other advise: to understand why? ;-)
Seriously, I realize it is not "completely" right, like with your passive network. But doesn't it get me closer to "right" than a middle of the road, non-time coherent passive XO?

I carefully re-read your paper on the Calypso HD development. I would say I studied it more that just reading. Lots of fantastic info there. I can see myself following your guidelines to build my DIY cabinets (plus what I hope to learn from the books, of course), and to get it mostly right in choosing drivers. But it would be just too arrogant on my part to assume I will be that good with XO design, and if that's the only path then it might become a deal-breaker for me. That would be a pitty!