Teaser photos - New project

[brianpowers27]

To be revealed at InDIYana 2009

[Face]

Have you been peeking in my window? :P

[brianpowers27]

More hints

--16L
--F3 40hz
--Cabinet by Nik Brewer

[AJINFLA]

Hi Brian,

Hard to tell exactly, but I would be concerned (alarmed? : ) with diffraction from what I do see. Are you planning any absorption or is this mainly a styling exercise?
The woofer would have to have substantial displacement capability to produce much spl at 40hz from that size enclosure, unless you place them very close to room boundaries. Otherwise, looks good :W .

cheers,

AJ

[brianpowers27]

Hi Brian,

Hard to tell exactly, but I would be concerned (alarmed? : ) with diffraction from what I do see. Are you planning any absorption or is this mainly a styling exercise?
The woofer would have to have substantial displacement capability to produce much spl at 40hz from that size enclosure, unless you place them very close to room boundaries. Otherwise, looks good :W .

cheers,

AJ

As always, I am aligning on the z-axis. Next time I may try the alternate approach which involes pointing the drivers at the ceiling, by slanting the baffle. I didn't solve the geometry problem but I assume that in this design I would have needed to change the CTC spacing in order to time align via slanting. I find the CTC distance to be critical. CTC affects the off axis performance greatly, wheras the diffraction tends to be more on axis.

The cosmetic design represents a departure from the usual stepped baffle confuguration. The surfaces are fairly complex. I am a fan of stepped baffles. They are much more complex than I would have been able to acheive by hand, without the use of a CNC. The depths have been milled to the exact specification that I gave Nik.

I recognize that this design will have a "unique" diffraction signature, without felt step treatments. I have tried the felt step treatments on previous designs but always found them to be unattractive, at best. I have measured the effect of felt on diffraction. The difference is notable, but not show-stopping.

This design will produce output down to 40hz. I don't have a decibel meter but I can safely say that they sounded clean at painful levels. While it produces enough output @40hz for a large bedroom,(15'x15'x8') it will not likely satisfy for HT in a living room(14'x23'x8'). I tested this design out last night in the living room crossed at 60hz to my subs. I can tell you that I was extremely happy with the sound.

Its size has been designed in such a way as to provide the option for large bookshelf mounting or medium stands.

--Bonus (If I feel ambitious in the near future...) I may try a DC bias on the tweeter.

[fjhuerta]

Is that a Dayton RS100?

[brianpowers27]

Nope, you are close though.

[AJINFLA]

Next time I may try the alternate approach which involes pointing the drivers at the ceiling, by slanting the baffle. I didn't solve the geometry problem but I assume that in this design I would have needed to change the CTC spacing in order to time align via slanting. I find the CTC distance to be critical. CTC affects the off axis performance greatly, wheras the diffraction tends to be more on axis.

I take it that you did not come away from the (long) discussion at PE with any further understanding of the issues . That's generally what happens when I toss a penny on the track in front of the moving locomotive. A bit of squeaking and maybe a few sparks, but the train keeps right on rolling along the track with momentum, undeterred.

As always, I am aligning on the z-axis.

As always, what is your point of origin (0,0,0) and where on the z-axis have you "aligned" what to? For what purpose?

The cosmetic design represents a departure from the usual stepped baffle confuguration. The surfaces are fairly complex. I am a fan of stepped baffles. They are much more complex than I would have been able to acheive by hand, without the use of a CNC. The depths have been milled to the exact specification that I gave Nik.

Nik does cnc to spec? For reasonable prices? Hmm, may have to investigate :W

I recognize that this design will have a "unique" diffraction signature, without felt step treatments. I have tried the felt step treatments on previous designs but always found them to be unattractive, at best. I have measured the effect of felt on diffraction. The difference is notable, but not show-stopping.

One should also recognize that recent research by Geddes seems to indicate that diffraction perception is also level dependent, not just signature depending on shape. Perhaps at the levels you listen at it will be not as perceptible.

This design will produce output down to 40hz.

I've got a 1.5" tweeter that will produce output to 100hz .
SPL and IMD levels won't be too good in room however.

I may try a DC bias on the tweeter.

Hey, why not. If it sounds better to ya, even without changing the soundfield, I see no harm :B.

cheers,

AJ

[brianpowers27]

I take it that you did not come away from the (long) discussion at PE with any further understanding of the issues . That's generally what happens when I toss a penny on the track in front of the moving locomotive. A bit of squeaking and maybe a few sparks, but the train keeps right on rolling along the track with momentum, undeterred.

One always has to ask "which one?", when considering the large multitude of screaching PE discussions. It could have been any of the following:

--Location of nulls and driver selection...
--Dipole discussion...
--Diffraction signature...
--Group Delay...
--Impressions of a quasi TP...
--Various HD and Fletcher Munson...
--Alignment of AC...
--Capcitors...
--Mills Resistors...
--Etc..

As always, I enjoy the way that you cause a train wreck right in the middle of a concurring discussion. :W I do not claim to know any more than anyone else when it comes to finding the right balance in design. I surely have broken many rules with this design and I do with reverance to the almighty LDC. ;x(

I know as well as you do that not all speakers are meant to be listened to on axis. While I wait for the budget pot to accumulate you will have to bear with me. I know that you are eagerly awaiting the "Ultimate Di-pole/bi-pole" speakers. But alas, I can't build much of anything ultimate with a $50 budget and no active electronics I am willing to surrender. I may however surrender my time over to various h-fram and U-Fram woofer configurations in an attempt to make something that resembles a di-pole-bipole woofer configuration.

The time alignment really doesn't solve all problems but it does seem to facilitate design by allowing symmetrical xo orders. Without having to compensate for extra z axis spacing, the simulated off axis response tends to be smoother along the x axis. I figure that since I seldom enjoy these speakers down in the semi-anechoic man cave, I should account for some level of off-axis performance.

With my mediocre woodworking skills I will need to rely upon the outside world to execute many of the woodworking ideas I have in mind.

I am working on sorting through the vast body of research that is available today. You seem to have already conquered most of Geddes, Linkwitz and Kreskovsky's work. Keep in mind that I have only really seriously been at this thing for a few short months now (<6). Believe it or not, I did read many of the articles that you have posted along the way. Between you and DDF, I have been given an immense body of work regarding various acoustical and psychoacoustical principles to chew on. :T

BTW: Did you try the DC bias trick?

[ThomasW]

The pair:

[1Michael]

That there is the strangest baffle I have ever seen. Does it work?

[JonMarsh]

A DC bias on the tweeter will tend to push the VC in the gap. IF it is misaligned to begin with, and if the DC bias pushes in the right direction, it MAY lower even order distortion.

OTOH, most even order distortion is due to the fact that the field is not symmetric in the gap. Just look at all the test results from ZAPH, myself, and many others- 2nd order harmonic distortion usually dominates. Yes, it's more Euphonic than high order, but it's still distortion, and contributes to higher levels of intermodulation distortion.

That's one reason I still use a rather old 7" woofer in designs from time to time- the HiVi D6.8- it has reasonably low levels of 3rd order harmonic distortion, but on top of that, the 2nd order is 10 dB lower than the 3rd, not 10 dB higher!

Just a few more thoughts to chew on... :W

[LING GOWA]

Let's see ya put a grill on that puppy! LOL. Looks great, amazing cutting.

[brianpowers27]

I still have a little work to do on this guy. I feel like everything was right except for the woofers lowpass filter. It is slightly too capacitive and sounds chesty. I will likely need to add some bsc compensation and rework the lowpass. The loss of sensitivity will then require some padding for the mid and tweeter.

[AJINFLA]

One always has to ask "which one?"
--Group Delay...
--Impressions of a quasi TP...
--Various HD and Fletcher Munson...

I know as well as you do that not all speakers are meant to be listened to on axis.

Speaker radiate a polar field. "On" what axis do you refer?

I know that you are eagerly awaiting the "Ultimate Di-pole/bi-pole" speakers.

I do? I thought it was your ears that were to be the beneficiary...

The time alignment really doesn't solve all problems

What is aligned in time? To where?

BTW: Did you try the DC bias trick?

When my speakers polar field, thermal compression, diffraction, spatial reproduction and other such trivial minutiae, have been developed to perfection, like those now biasing caps, maybe I'll focus on tricks. That have been around since '93. :W

I feel like everything was right except for the woofers lowpass filter. It is slightly too capacitive and sounds chesty.

How thick is the baffle? Might that have to do with the tunnels behind the drivers instead?
A thick baffle would look a lot like what Thiel does, were I to have one cnc'd for a monopole.

cheers,

AJ

[brianpowers27]

Speaker radiate a polar field. "On" what axis do you refer?
1. What is aligned in time? To where?





2. How thick is the baffle? Might that have to do with the tunnels behind the drivers instead?
A thick baffle would look a lot like what Thiel does, were I to have one cnc'd for a monopole.

cheers,

AJ

1. Time aligned as always on the x axis originating at the tweeter :B As always, I have built a monopole with a fair balance between on axis response and power response.
2. THe baffle was created with 2.5" mdf. Nik removed a large amount of material to create extra space. The mounting of the woofer is fairly standard. The space behind woofer is about 7.5"x7.5" x 10". I would really have to show you what I mean. No doubt there is some tunnel resonance but I don't think it is huge. I used rockwool to combat the tunnel.

I know that the filter is capactive because I designed it that way. Originally I tried to squeeze out some extra juice in the 100-300hz range by oversizing the capcitor /inductor ratio. Due to miscalculations on the effect of BSC in the space the peak manifested differently. I will most likely add a 4-6db BSC filter and reduce the capcitance.

3. AJ - POst some links to your projects. Your helping/heckling :P has got me curious. There is no better insight into your philosophy than seeing what you actually build.

[mpotoka]

The pair:

Uhhh--where'd you get that picture from? Were you at the GTG on Saturday?

[ThomasW]

Uhhh--where'd you get that picture from? Were you at the GTG on Saturday?

https://www.htguide.com/forum/special/albums/944248-dirk-s-photos-from-indiyana-09#post944248

[brianpowers27]

On the stand

[ThomasW]

You might consider covering the baffles with a layer of high-wool content felt gasket material. That will go a long way toward solving the problematic diffraction effects created by having drivers fire into the edges of stepped baffles...

If you search this forum you'll find plenty of discussion about high-wool content felt gasket material.

PS: yes I know it's ugly, BUT it does wonders...

[brianpowers27]

You might consider covering the baffles with a layer of high-wool content felt gasket material. That will go a long way toward solving the problematic diffraction effects created by having drivers fire into the edges of stepped baffles...

If you search this forum you'll find plenty of discussion about high-wool content felt gasket material.

PS: yes I know it's ugly, BUT it does wonders...

I totally hear you. I have spent some time testing various baffle configurations and the amelerioration with felt. I have a big roll of SAE13? .75"x1"t felt sitting in the basement.

I am sure that you understand the need for WAF. These may end up as the main speakers in the living room. In that case, felt is out of the question. I just can't imagine any way to do it that still looks good.

Now speakers that go into the recording room/ man cave have an entirely different set of parameters.

[ThomasW]

Make a felt pad and cover it with grill cloth. Attach it to the baffle with Velcro

[AJINFLA]

1. Time aligned as always on the x axis originating at the tweeter :B As always, I have built a monopole with a fair balance between on axis response and power response.

Hmm. Your answers don't seem to address my actual question so I think this only adds to our confusion. Rather than a question, let me state what I think you have done. You have taken 3 physically separated drivers, assigned a "reference" point on each - where the VC attaches to the diaphram (really a circle, not a point ). You then pick an arbitrary point in space that is equidistant to all three. This is what you refer to as "time" alignment. What I would call that is "distance" alignment to a point. The purpose of which, I am not sure. The second part of your answer is a separate issue altogether.
I think the whole issue of "time" alignment is a source of great confusion, as indicated by John K's article, which hopefully you read.

2. THe baffle was created with 2.5" mdf. Nik removed a large amount of material to create extra space. The mounting of the woofer is fairly standard. The space behind woofer is about 7.5"x7.5" x 10". I would really have to show you what I mean. No doubt there is some tunnel resonance but I don't think it is huge. I used rockwool to combat the tunnel.

Yes, picture would certainly be helpful. I'm sure there is some scalloping behind the driver, but based on the width of the loudspeaker, perhaps only a modest angle could be obtained at the sides? It may be nothing, or it may well be contributing to the chestiness. There is rockwool even inside the scalloping?

I know that the filter is capactive because I designed it that way. Originally I tried to squeeze out some extra juice in the 100-300hz range by oversizing the capcitor /inductor ratio. Due to miscalculations on the effect of BSC in the space the peak manifested differently. I will most likely add a 4-6db BSC filter and reduce the capcitance.

The whole idea of applying a fixed eq filter to a loudspeakers LF without first measuring some responses in room at the intended placement seems a bit bizarre to me.

AJ - POst some links to your projects. Your helping/heckling :P has got me curious. There is no better insight into your philosophy than seeing what you actually build.

Sorry about the perceived heckling. I mistakenly thought you might have wanted various questions asked about the why's of the design. I was just curious as to what you have posted. The intent was for both of us to have a better understanding.
I'm a terrible record keeper and most of my stuff is just cobbled together on a whim. I'm afraid there would be not much for you to learn from seeing what I did, other than maybe what not to do.
Btw, a couple of guys in attendance at your DIY have heard my monstrosities. Perhaps you might reference them for some insight, rather than me, the builder.
As far as the diffraction goes, if you are happy with the sound..and the wife is happy with the looks, then I see no problem :W .

cheers,

AJ

[brianpowers27]

AJ,

You are absolutely right. I took a point in time and distance aligned the drivers to this point. The drivers are slightly offset from the center otherwise the distance to the drivers would be approximately the same while moving left to right, provided you don't stand up/sit down. This provides a relatively time aligned design on the vertical axis. I have used a 3rd order tweeter/mid xo to provide better off axis response on the horizontal axis.

The drivers do not have a significant scalloping behind them. Nik has planed the width of the baffle being the driver and the cavity to about .75" from the full 2.5".

Everyone knows and loves you point of view, even if it does come accross as heckling. :T I don't mind the questions. I do take it in stride because I tend to ask some of the same questions as others.

I do recall hearing one of your designs down at DIY Lexington. At the time, I didn't exactly know what I was listening for. If my memory serves correct, you brought a dipole consisting of the coax 12" along with another 12. The room was nearly anechoic so it was hard to find the truth behind a dipole design. By the end of the day my ears were shot and I didn't have much intelligent left to say.

I do not always have the luxury of custom tailoring each speaker to the specific room ahead of time. I like to move them around to different areas and experiment with the performance in various rooms. I am planning on making the BSC easily adjustable so that I can achieve a more tailored sound. I tend to find ways to transform the overall acoustics of the room as well, when possible.

[brianpowers27]

Photos of the back. Note woofer cavity: I am feeling much to lazy to labor over more photos now. I may do so at a later time.

[fbov]

At least I'm seeing wire nuts... you could have used some Saturday!

Sadly I missed listening to these; my accomodations were cheap but not convenient! I like the look in your (presumed) living room.

Frank

[Dennis H]

What is aligned in time? To where?

C'mon AJ, we all know it's aligned at the sweet spot. We know you're a big fan of coax drivers but they have their own problems which may or may not be bigger than the phase problems of using separate drivers. There's no need to beat up on people every time they mention time alignment just because they don't share your coax fetish. And there's no need to play dumb and say 'well I was just asking a question'.

[JonMarsh]

Well, AJ does have a bit of a point, in that a physical alignment of some part of the driver may not produce a time alignment of the impulse response. To know that for certain, you really need to take some specific care in measurement, if thats your goal.

To an extent, we can fudge things a bit in the phase/transition in the crossover to make up for that- look at the NeoD CC, for example, as regards midrange to midwoofer alignment- obviously not possible physically with the baffle design I used, but I placed a higher premium on diffraction issues, and fixed the other stuff elsewhere. Different strokes for different folks.

Still, I acknowledge AJ is being a bit sly- but he's also being polite about it. IMO. We all come from different backgrounds with different expectations about what is needed and how to get there. You might argue that at times AJ uses the Socratic method rather than a straight forward exposition of his point of view. That way, his views aren't imposed on the other party in the dialog, and he's more likely to learn where they're really coming from.

[JonMarsh]

Is that a Dayton RS100?

Maybe it should have been a Dayton RS-100? :W
I have four of the RS100-4 on the way to test for use in my current project- let me know if you're interested in the results. I have high expectations. :W :B

[AJINFLA]

C'mon AJ, we all know it's aligned at the sweet spot.

How do we know that? I can't make sense of that Dennis. I can see, as Jon noted, alignment of the impulse to the tip of a mic. That is easily understood. Where the mic is, is almost never given in these discussions and even if it was, how does that become a sweet spot? We have 2 pinna attached to our non stationary heads. You think it's possible to "align" multiple drivers on each stereo side to each pinna (never mind reflections) in "time"? How about "almost" aligned, or "nearly" aligned? But then I might ask why?

We know you're a big fan of coax drivers but they have their own problems which may or may not be bigger than the phase problems of using separate drivers.

That isn't quite accurate. I am a big fan of polar field uniformity and have been for a long while. The fact that a coaxial (coincident/triaxial/unity,etc) type arrangement allows for greater symmetry and uniformity of the polar field is what I am a "fan" of. Coaxial is just the means to an end. "Time" alignment not so much :W. I have always noted coaxials as having their own issues, but this is sidetracking our alignment in time issue.

There's no need to beat up on people every time they mention time alignment just because they don't share your coax fetish.

Beat up? Jon's got it. I like to see what the other persons point of view is, because our definitions and meaning of the same words or phrases may be different (clearly Brian's and mine do. I view distance and time as separate entities). Especially when it involves audio. Subjective and scientific definitions tend to diverge. Are we in "synergy" on this? :rofl:

And there's no need to play dumb and say 'well I was just asking a question'.

Play dumb? :B

cheers,

AJ

[AJINFLA]

I do recall hearing one of your designs down at DIY Lexington.

Ouch. I want to say it was the long drive, but reality is that memory is one of the first things to go in old age. I didn't realize you were there. My bad.

At the time, I didn't exactly know what I was listening for.

For me it is always how real does it sound. Or how much do they not sound like speakers (I'm the opposite of audiophiles. I don't want to hear speakers or capacitors or equipment). Yes, it depends on the recording, but if you have enough familiarity with the instruments heard at live events, you should reference your memory of it. Wolf seemed to either have enough familiarity with the recordings and/or instruments to determine that something was amiss, though he could not specify what, so it may be difficult to trace.

If my memory serves correct, you brought a dipole consisting of the coax 12" along with another 12.

Yes and a 15 as well . Couldn't go cardioid mode without it. Did you stand behind them?

The room was nearly anechoic so it was hard to find the truth behind a dipole design. By the end of the day my ears were shot and I didn't have much intelligent left to say.

Yes. The rooms DIY event are generally held in make it impossible to judge true SQ, not to mention the very brief time exposure. If you recall I was speed tracking to get as many different type tracks in.

I do not always have the luxury of custom tailoring each speaker to the specific room ahead of time. I like to move them around to different areas and experiment with the performance in various rooms. I am planning on making the BSC easily adjustable so that I can achieve a more tailored sound. I tend to find ways to transform the overall acoustics of the room as well, when possible.

Don't forget your HK has a bass knob :W . I prefer for the speakers to adapt to the rooms acoustics rather than vice versa.

[brianpowers27]

Maybe it should have been a Dayton RS-100? :W
I have four of the RS100-4 on the way to test for use in my current project- let me know if you're interested in the results. I have high expectations. :W :B

I have seen the plots at Zaph's site. I chose the rs125 on account of displacement rather than distortion.

AJ. I didn;t stand behind them. Like I said I was not ready to evaluate a dipole vs monopole.

I was also very tired at the event and like all old people get, I was falling asleep by the end of Lex.

[Dennis H]

I view distance and time as separate entities).

Well, dang, why didn't you tell me you were using flux capacitors in your speakers, AJ? Now it all makes sense.

[AJINFLA]

Hey, only da best for me Dennis. If I can't charge 'em, I flux 'em.

AJ. I didn;t stand behind them. Like I said I was not ready to evaluate a dipole vs monopole.

Well, that would have been both at once. Cardioid, hence...
Hmm, now I wonder if anyone there actually understood why I was asking them to stand/listen behind my speakers (other than the obvious "because they suck less that way")??

cheers,

AJ

[brianpowers27]

Hey, only da best for me Dennis. If I can't charge 'em, I flux 'em.

Well, that would have been both at once. Cardioid, hence...
Hmm, now I wonder if anyone there actually understood why I was asking them to stand/listen behind my speakers (other than the obvious "because they suck less that way")??

cheers,

AJ

How can we know what we are really looking for when we are not operating the equipment in a real room?