12-inch drivers for sub

Deadbeat, I think everyone who consideres the science behind speakers is also thinking about the subjective effect. In the thread you link to, like so many others, the commentors are trying to correlate the scientific measurements (like 18Hz vs 28Hz -3dB point) with the subjective experience (how the bass "sounds").

People who understand science think like this:

Physical design <=> scientific measurements/specs
Scientific measurements/specs <=> percieved sound

People who don't understand science can't think that way and are restricted to:

Physical design <=> perceived sound

I think it could be genetic. The scientific way of thinking deals with intangibles, and requires the ability to layer abstract ideas. Maybe some people simply can't do it. But if they can make a box, stick a driver in it and make a noise why stop them?

I'm sure AJW doesn't wander into university labs saying "I've got nothing against your research but it's a gold-plated turd and I subjectively know you're all wrong even though I haven't got a clue what you're doing and could never do it myself." But people are less inhibited on the 'net.

Edit: AJW's last comment is a perfect example of "physical design <=> perceived sound" thinking. And his gross oversimplification shows the limitations of this way of thinking.

Edited by: jsg

I'm spooked. Outta here, I've got some work to do [img]smileys/smiley17.gif[/img]
Edited by: Deadbeat

jsg, You have made considerable sweeping statements in your post above that to be honest YOU are not entitled to make. You do not know me, you do not know my technical abilities.

Listen I will say this only once, I have done the design's, I have built the boxes, I have modified the boxes, I have tried different drivers, I have measured the results, and most important of all I have listened to the results.
I do not like the outcome, do I personally feel the need to go back over my designs and spend more time from my life on a design that I feel is fundamentally flawed, no.
As I have stated before I accept that when used on sub only they do have their uses.

A little bit of humility and certainly a sense of humor injection would not do you any harm my friend.












Edited by: AJW

This thread has raised some interesting points, but it is starting to get personal which to me is bad.


The discussion is turning into what the academics call controversial dialectic. Controversial dialectic is the art of disputing in such a way as to hold one's own, whether one is in the right or the wrong. In an ideal world we would aim in every debate for the discovery of truth; we would not care whether the truth proved to be in favour of our own opinion or of the opinion of our adversary. Unfortunately our innate vanity, which is particularly sensitive in reference to our intellectual powers, prevents us from admitting that our own proposition was wrong and our adversary's right.

I just re-read this. Just to make it clear I'm not having a go at anyone and include myself as falling prey to this.

Step away from this particular debate and read this thread on Harmony Central.

acapella.harmony-central.com/forums/showthread.php?t=1408416


So much time and energy spent (not by me) on trying to say that a SM58 must be better than some other mic. [img]smileys/smiley5.gif[/img] Talk about being like a dog with a bone.

Discussion boards seem to develop their own social dynamic. Cliques form and newcomers or seemingly outsiders get mobbed by regulars. Frequency of posting gets misinterpreted as usefulness and accuracy of what is contained in the post. Just because someone is a newbie to a forum doesn't necessarily mean they a newcomer to the subject being discussed.

I used to post fairly regularly on Harmony Central but eventually stopped because it went from a fairly friendly place to being largely adversarial (see the link above). Maybe it is a cultural thing, and as a sensitive Brit I couldn't cope with the mainly Yank brash attitude.

Coming back to the topic of subs, we used to call them bass bins, as well as the subjectivity of listening tests and objectivity (supposedly) of theory and measurement, you also have to factor in fashion. Forty years ago the average system would have probably been two way crossing over at 500Hz. When I first started in the business the company we had our cross-overs made to measure. I couldn't figure why one PA system I designed sounded so bad. It turned out that the electronics company that built the cross-over thought that the 250Hz cross between bass and low-mid was a mistake and raised it to 450Hz. Even to my correct specifications, how many would choose 250Hz, 1200Hz and 5KHz for their cross-over frequencies today? A W-horn up to 250Hz? It was fairly common 30 years ago.

In the pre-digital era, phase response was some esoteric subject that theoreticians talked about. Now that it is easy to measure, it is suddenly as important if not more so than the amplitude response. If Heyser was correct the two are interminably linked anyway; and as group delay is a derivative of phase it to is linked.

I recently posted on a thread about planar horns. I remain sceptical about them. In the sub 100Hz frequency range how much different are they to the JBL 4560? Swap the four corner ports for a single rectangular port and you are back to the Altec Voice of the Theatre design. Yo the old guys got it right all along 40 years ago.

Have a look at some of the tapped horn designs. Straighten out the folds and is it really a horn or a tuned pipe? The mouth area is far to small to be a classic horn. How many tuned quarter wave pipes have been used in sound reinforcement? Horns get a lot better press even though theoretically they are just a highly damped pipe.

Unfortunately on internet discussion forum simply sating that “I've built some and the sounded Sh*te” doesn't help determine why. Details of design and drive units would help the group to analyse whether there was anything common to the bad designs that could be eliminated in future designs. Yes we are re-inventing the wheel, but many on this forum don't know what that wheel is, but if sufficiently motivated and with the help of good discussions they might eventually build a better wheel.

Mmmm... where to start on the perception of sound. Try here:

deutsch.ucsd.edu Calm down chaps. They're only wooden boxes.

p.s. I guess this is not a good time to mention the 8th order bandpass design [img]smileys/smiley2.gif[/img] [img]smileys/smiley4.gif[/img]





Edited by: Steve_B

I guess.

What I've concluded about the tapped horn. Yes, it's not something revolutionary - but it is a nice way to make a small box play loud and low. And it's a bit of a funny name - horn does sound better but who on earth calls pipes or horns quarter wave resonators in marketing lit? But I think some credit is due - I've perused a lot of patents and figured that the idea is new, but the physical implementation isn't. There was a patent that looked like one but actually had a bunch of holes in the back of the pipe for some reason, and the infamous Jensen Transflex and JBL Air coupler which one could call tapped pipes due to the nonexistant expansion.

I still call them bins a lot [img]smileys/smiley36.gif[/img]

8th order BP has been mentioned and ignored in this thread...

But in the end, they are as on my signature in SP 'bits of ply around a driver'

And it is which way you stick them around that matters...

Apologies to anyone who took my comments seriously.
Edited by: Deadbeat

Anyone wanna discuss bandpass group delay in a new thread? Orvia PM, perhaps?
Edited by: jsg

What about the 8th order bandpass concept? You seem to have been convinced by your implementation of it as indeed have others who have heard one of yours (as opposed to some truly nasty car audio bps i've heard - but then again most car audio bps I've heard are nasty - no offence to anyone who makes good ones). I'm interested.

I dont think there's anything special about 8th order from a SQ pov. The same group delay issues apply to 6th and 8th.

8th just goes further down the road in terms of efficiency breaks etc.

jsg wrote: Anyone wanna discuss bandpass group delay in a new thread? Or via PM, perhaps?
 

If we are discussing designs it might as well be kept open to everyone. 

It strikes me that the proof of the pudding is in the eating.

JSG seems to have done plenty of research into the mysterious 8th order technology, and Tony seems to be adamant that his ears tell him any bandpass up that high wont sound great. As an outsider to this thread it seems like the answer is in the GD.

For Tony it seems like the only way he could be convinced is to build one of JSGs designs or meet up for a proper listen if that is possible.

Stu