4 Pi vs DIY Sound Group's Fusion Sentinel 15" - Page 7 - AVS Forum
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Old 04-24-2013, 01:33 PM
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Originally Posted by Ash R View Post

Oh well yeah, Parham uses a slight downward tilt. So does Linkwitz and Geddes to my knowledge.

So you dont think a greater then 3 db difference across the entire treble will have a large effect on actual and perceived sound quality?

I'm not saying one sounds better then the other either.
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Old 04-24-2013, 01:35 PM
 
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Originally Posted by moxxy*mig View Post

I'm not coctostan but, at least to my knowledge, the source of horn honk hasn't been clearly identified. My understanding of the current thinking (i.e. Geddes) is that HOMs are the source of honk, and the amount of...annoyance they cause is level-dependent.

I think Parham says basically the same thing about HOM being level dependent, but he seems to think tube amps can do it too (presumably at lower power). Maybe I misunderstood his meaning but that's what I take from this statement:

"As an aside, you can use the constant current method to expose reflections and standing wave modes. The impedance spikes created by those reflections are sometimes damped well enough by a voltage source that they aren't immediately obvious. That doesn't mean they won't show up with a vengeance if used on a tube amp with low damping, or even because of parameter shifts, like what happens at high power."
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Old 04-24-2013, 01:42 PM
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Do you think the reflections cause horn honk? That's really what I'm driving at.

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You know what, never mind. I realize this is being perceived as trolling so we're getting nowhere. That was never my intention.

It is trolling...but that doesn't mean you are a troll. biggrin.gif Feel free to discuss but there is a certain amount of respect expected. I don't know you so I will assume you are a nice guy with a passion for this hobby just like me.
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I'm not coctostan but, at least to my knowledge, the source of horn honk hasn't been clearly identified. My understanding of the current thinking (i.e. Geddes) is that HOMs are the source of honk, and the amount of...annoyance they cause is level-dependent.

Oh, and their existence hasn't been conclusively identified in measurements. (yet) On this point my knowledge is probably lacking.

FWIW, I think coctostan was trying to redirect the thread back to the OPs Q. I wonder if he's made plans to have audition either design?

Yeah, if you want to discuss horn honk go to DIYaudio and look at probably the longest thread in the entire DIY world. My opinion is that all of the different approaches offered to mitigate horn honk have done the job collectively. Better CDs than in the past, well designed crossovers, less horn diffraction (whether done via L'Cleach, Geddes OS, SEOS, minphase, Parham caternary), better understanding of comb filtering, designing with off-axis response in mind. These are all improvements over old school horns and frankly I don't think there is any more discussion. Everyone was looking for this single needle in a haystack when horn honk was more like a recipe of ingredients causing one large problem.

I'm actually less interested in steering the thread back on topic and more interested in people gaining the perspective that designs are not good and bad or better and worse. They are choices. Big V8 or turbo inline 6. iPhone or Android. You will notice that I never come into a thread asking if someone should go with SEOS and tell them SEOS is the way to go without question (nor do I in PMs). At most I will say that I personally like the SEOS approach and that there are other excellent approaches like Pi, Geddes, etc. There are others I have less experience with like an Iwata or L'Cleach horn. I will point out tangible issues with certain design paradigms or when I feel a design is simply obsolete. At some point the SEOS and Pi paradigms might become obsolete too.

Anyone who will tell you that SEOS or Pi sounds better than one or the other is full of it (knowingly or not). Unless Mr. Parham has heard a SEOS design and compared it in a DBT against one of his Pi's he couldn't say one way or the other honestly. He can say that his experience and understanding dictated his design choices resulting in what he believes should be superior. Of course, he might sit down and prefer the SEOS in a DBT (and vice versa with anyone involved with the SEOS design).
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Old 04-24-2013, 01:59 PM
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Yeah, if you want to discuss horn honk go to DIYaudio and look at probably the longest thread in the entire DIY world. My opinion is that all of the different approaches offered to mitigate horn honk have done the job collectively. Better CDs than in the past, well designed crossovers, less horn diffraction (whether done via L'Cleach, Geddes OS, SEOS, minphase, Parham caternary), better understanding of comb filtering, designing with off-axis response in mind. These are all improvements over old school horns and frankly I don't think there is any more discussion. Everyone was looking for this single needle in a haystack when horn honk was more like a recipe of ingredients causing one large problem.

I'm actually less interested in steering the thread back on topic and more interested in people gaining the perspective that designs are not good and bad or better and worse. They are choices. Big V8 or turbo inline 6. iPhone or Android. You will notice that I never come into a thread asking if someone should go with SEOS and tell them SEOS is the way to go without question (nor do I in PMs). At most I will say that I personally like the SEOS approach and that there are other excellent approaches like Pi, Geddes, etc. There are others I have less experience with like an Iwata or L'Cleach horn. I will point out tangible issues with certain design paradigms or when I feel a design is simply obsolete. At some point the SEOS and Pi paradigms might become obsolete too.

Anyone who will tell you that SEOS or Pi sounds better than one or the other is full of it (knowingly or not). Unless Mr. Parham has heard a SEOS design and compared it in a DBT against one of his Pi's he couldn't say one way or the other honestly. He can say that his experience and understanding dictated his design choices resulting in what he believes should be superior. Of course, he might sit down and prefer the SEOS in a DBT (and vice versa with anyone involved with the SEOS design).

Couldn't have worded it a better way biggrin.gif
I'm honestly looking for a reason to buy something SEOS, just to hear what you guys have put so much effort into, but I just have no room for ANYTHING, especially after the FTW-21's arrive.
When I bought the 4Pi's, the SEOS project was still midway through, so nothing was available for purchase. I had a chance to get cabinets built for me and I went forward with it.

I've been following the "hey guys we need a little... " thread since the very beginning, it's crazy really.
Regardless of what you chose, I think it's pretty damn cool we can compare the two, and say that the DIY guys collectively made something that's up to par with some greatly respected products.
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Old 04-24-2013, 02:08 PM
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Thanks. It really is important. There are bad designs out there and some are just obsolete (then again there are people using vinyl still). The key is that none of this is cut and dry. Pi speakers are awesome. That much I can say with confidence. I can say the same thing about the SEOS speakers I've seen and heard. Someone else might disagree and I respect that.

BTW, Ash, if you Wayne thinks the SEOS-12 is used to low (and he might be right), I wonder what he thinks of the JTR Noesis which uses a 7" deep 60deg horn down to something like 500hz. It certainly drops into modal territory but by all reviews it is certainly not an objectionable design...and is in fact highly regarded. I myself am skeptical of how low that horn is used, but designing speakers (or any engineering project really) is a practical and not theoretical exercise.
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Old 04-24-2013, 02:11 PM
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This is actually of interest to me, in the context of the thread's original question. Lots of different opinions around as to the merits of a downward FR tilt, and what's the "best" to shoot for with different types of speakers (particularly controlled directivity vs. not so much).

When I finally get around to building my SEOS12/DNA360/TD12X speakers (woofers arriving next week, still have to order the rest) I'll likely want to play with this by way of equalization. I'm a music guy first, with HT trailing behind by a bit.

Anybody have any thoughts on flat vs. tilted, particularly in CD designs and particularly geared toward a satisfying music experience?
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Old 04-24-2013, 02:14 PM
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first things first.... there is no right or wrong.... there is only subjective bias as to what *sounds* right or wrong to the individual listener.... the standard that ruler flat response is the ideal and correct result..... it's a bunch of baloney...... every speaker designer makes their own choices to produce their speakers that voice what they think is the best compromise given the parts and drivers used in the design.... every sound engineer does their own thing to alter the mix of the music we'll ultimately playback on our systems...... every live venue sounds different because of the sound system setup.... half the guys running the sound boards at live shows I've attended are idiots that wouldn't know good sound if it smacked them upside the head smile.gif... whoops! there I go with my own feelings and not respecting the right for folks to make their own choices about what sounds right and wrong to them.....audio is very subjective and what one person likes may be nails on a chalkboard to someone else.

A speaker building friend of mine has very rolled off hearing above 10K... all the speakers he's built purposely had a rising response above 8K and sometimes were more than 20dB hot at 20K... he loved them because he could now hear the highs.... I ran screaming from the room with blood leaking from my ears smile.giffrown.gif.... I don't like a ruler flat frequency response. It does not sound at all "real" or "natural" to me. I have my own "house curve" that I look for because of me being extremely sensitive in the < 2K- > 8K range. You bet your a$$ I can hear a 5dB difference at 4kHz. That is extremely audible to me based on the listening tests I've done playing with EQ settings. However, if someone has a speaker that has a massive peak in the midrange, or rolls off at 8K 96dB per octave so there is no sound at all in the treble, or is so forward and bright sounding that it is painful, if it sounds good to their ears, that's all that matters... it's "right" to them.... if a waveguide has resonances that another waveguide doesn't have or if one loads the response differently than the other and the person listening likes the way one sounds over the other, that's right to them... I have my own opinion about whether or not the peaks and valleys in a waveguide (be they "honk", distortion, standing waves, HOM, natural loading differences, whatever) response is right or not.... but if someone else either doesn't hear them or does and doesn't care about them because it sounds better to them, who am I to argue?

There's all kinds of other things that play into what is important to one listener and irrelevant to another... and some of it actually has to do with the frequency response of the speaker! smile.gif hehehe. I'll leave the debate that all amplifiers sound the same as something that can be endlessly beaten to death in another thread... but I've done enough blind listening tests between equipment over the years to feel pretty confident that I'd hear a difference and have a preference if I were to hook the same pair of speakers to my digital music fed into my high end DAC and then on into my various tube, hybrid, and solid state amps compared to having the same music fed through a $200 Onkyo receiver on to the speakers.... now, depending on the speakers, there are circumstances I might prefer the Onkyo to be hooked up to them rather than a more revealing piece of gear wink.gif seeing others have that light bulb moment is cool, too even with modestly different electronics... it doesn't have to be huge dollar differences.... I got a kick out of swapping out our nanny's $hitty Sony receiver, putting a Sherwood R972 receiver in its place, and watching her jaw hit the floor when we re-played the same tunes....

it's not purely just frequency response and distortion... there's more at play than just that, imo... whether we can measure it currently with today's measurement methods and equipment is up for debate... but I've used EQ from lots of devices before (to name but a few: Tact, Lyngdorf, Audyssey Pro, Trinnov, numerous pro EQ units, and lately Dirac Live filters on the PC before the digital audio is sent out USB or through Lynx AES16)... and even with different CDs on the same waveguide EQ'ed to as close to teh same frequency response possible, I still hear differences... sometimes subtle, sometimes not, but they are there to my ears at normal sane volume levels, not even ear bleeding SPL levels.... so, as an example, Erich may not hear a lick of difference between an EQ'ed DNA360 and BMS4550 CD playing a test tone in his system... that very well may be true for him... I may have a different experience when I do my own controlled listening test in my system....and depending on if I hear a difference and where that difference is, it may be extremely subtle and not worth mentioning or it may be a huge deal to me (and at the same time may not even be noticed by others).... neither of us is wrong.... I was at an audio get together a couple years ago and there was a piece of gear oscillating at ultra high frequencies and it was coming through the ribbon tweeter speakers.... it was driving me utterly insane.... I kept asking "Can you not hear that?" and none of the 15 other guys could hear a thing.... if a tree falls in the woods............

So some levity and rationality should likely enter this discussion at some point....

endlessly arguing about comparisons between two products without hearing the two items in the same system you are familiar with and with your own ears is honestly pointless, imho. There was some objective discussion about the options and how you can go about getting a pair of each speaker built asked about by the OP... beyond that, it really is a trust your own ears not someone else's kind of deal, imo..... unless you know the person who's giving their opinion and you know whether they hear things in a similar manner to how you do or not, it's all just a bunch of fluff and supposition. it makes for pages of ranting and hiding behind keyboards and beating a dead horse.....but beyond that, I'm not sure it ever truly gets resolved purely based on the subjective nature of what is being asked....It sucks that folks can't just drive down the road to a local place to hear any combination of gear they want and do their own comparisons for free... welcome to life in the internet world.... not that it would ever really exist for these DIY kinds of things anyways... the final word for me has always been hearing something in my own system to see how my gear and my room affect my overall opinion. So I pay my money and give it a go....
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.... But to set the record straight of Wayne's "profit" business. He makes his plans available to the DIY crowd free for the asking including the crossover schematic. You can spend hours sourcing all the components and waiting for sales on the components like I did. In the end I think I saved about $150 per speaker versus his kit with assembled crossovers, mostly because of a fourth of July 20% off sale on the woofer. Even though I didn't spend a nickel with Wayne he answered every construction question I had on his forum and didn't hold back any secret sauce. Not much profit in that...

I'd like to second this sentiment. Wayne was extremely helpful through out my build even though I did not buy a complete kit. He gives away the plans for free which is not an option at least for some of the SEOS designs.


I've seen some of the un-cleansed Wayne postings.... That's not for me to weigh one way or the other about. It is what it is. I have my own opinion about how both camps have reacted to the requests for comparison....

but I will say, no matter your opinion about the content of what Wayne posted and any motivation there was behind said postings, he did respond to every email I've sent him the same day it was sent..... and all I bought from him was a single pair of H290C waveguides to build a set of his 3Pi speakers. He emailed the crossover schematic the day I asked for it.... completely for free. No questions asked. No delay. That was not my experience with all SEOS offerings, FWIW.... The schematic also came with the complete plans for the speaker including cut list for the cabinet.... and he answered *in-depth* every question I had about the plans fully knowing that I had all the parts beside the waveguides to build his speaker and would not be buying anything other than the waveguides from him. Did he make some money selling me a H290C waveguide? Yes.... but he didn't get rich on 2 $50 waveguides for his time invested, that's for sure. Jeff also answered my questions once I had the crossover schematic for the Zephyrs.... and I've seen the other SEOS designers answer questions about their designs here on the forum.... as a person on the outside looking in who bought stuff from both camps, for what I paid for each, that makes them both about even in my books for my money invested. Which will be "better", the Zephyrs or the 3Pi? Who knows. That's why I bought the parts and schematic I needed beyond what was already here in my garage to make both and see for myself..... they may be more similar than different and what works for me likely won't work for you.... I'll find out before too awful long....

Shane
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Old 04-24-2013, 02:18 PM
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To the OP,

I have just personally built 2 of the 4Pi kits in their basic configuration (Emminence compression driver and woofer) and am very happy with them. I had been lusting over them for a couple years before I got the space and $$$ to buy them back in December. I actually bought 3 kits for my LCR but have not put the 3rd kit together yet. The quality of the components from the drivers to the crossovers are very high. Even though most seem to go for the JBL woofer upgrade, let's not forget that the Emminence woofer is a great woofer. I did not go for the upgrade because the difference between the two, from Wayne's accounts, was in the distortion at high SPLs. These speakers have so much headroom in my basement living room theater that I was not concerned enough with that difference to justify the added cost. Going from my Klipsch RF-82s to these 4 Pi's was a huge upgrade. Even without running a center channel, movie and TV dialog is very much improved. Overall, things just sound much better than with my Klipsch's.

Now for my comparison between 4 Pi's and SEOS designs. I think that the aesthetics of the 4 Pi design are rather poor and prefer the looks of the SEOS designs. I think they both employ design philosophies that I agree with. I bought the 4 Pi's because I had been reading about them and Wayne's design philosophy for years and was comfortable with what he is selling. I had not been keeping up with the rallying thread here or the econowave thread simply because the post count had gotten so high that I did not have time to get through them and I was, therefore, less comfortable with what was going on in the SEOS design. I also bought the 4 Pi's because they came with assembled crossovers on a PCB. For me, that was just a really nice to have item. Now that some have been actually building the SEOS designs and posting their impressions of them I would feel much more comfortable with buying a SEOS design.

In fact, if I made the purchase today, I would likely have chosen the SEOS design based on aesthetics over the 4 Pi. I think both designs are great values and both are an obviously huge upgrade over the Klipsch speakers I was previously using. I really don't think there is a bad decision to be made.

SXRDork: SXRD is a technology. My name is Vann. Usernames are for life...
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Old 04-24-2013, 02:34 PM
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Preorder for the plastic SEOS-15 coming up this week. I finished taking pictures of all the big give aways that I had sitting around. We're ready to rock and roll on another one.

It's raining today, so I will have a good deal of time to start getting caught up on packaging. If there's time, I'll start working on the preorder page.

I almost missed this..... any more elaboration on where packaging is in the grand scheme and when to expect some of the group buy stuff to be going out? Thank you.
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Erich,

I know it's your busy time of the year.... but can you give an overall update of where we are with the BMS group buy shipments, the Poland pallet shipments, and how it all flows in with regular DIY Sound Group orders? Are you 1 week behind clearing just regular DIY sound group orders? 2 weeks? more?

When should we expect the BMS and Poland stuff to start shipping?

Thank you.

Shane
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Old 04-24-2013, 02:42 PM
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"Do you think the reflections cause horn honk? That's really what I'm driving at."

i'll bite. the simple answer is no.

the primary reason for horn honk is sharp impedance mismatches somewhere between the compression driver and your ear.

the effect can be easily heard by rolling up a magazine into about a 2" diameter tube and talking through it. the transition from the air in tube to the air in the room is a total impedance mismatch, hence honk.

the primary sources tend to be:
1. down near the throat of the horn where many horns in the past used "diffraction slots" or other significant discontinuities in the flare to shape the wave, and
2. at the edge of the mouth where many horns had sharp angles to the the baffle, and
3. significant mismatch between the exit angle of the compression driver and entry angle of the horn throat

but like it was said, there is a long list of contributors and sometimes missing one or two can still work great.

all the good horns mentioned avoid these problems. the only example that i can think of that runs to the contrary is the horn in the older jbl k2. it had a bit of a diffraction slot, but no horn honk.

the seos is well matched to the cd, has no diffraction slot, has no discontinuities in the flare, and has a nice large roundover. once you have these, you are well on your way to a good horn and flare shape becomes a matter of choice based on the application. constant directivity was the choice made for the seos. size sets the frequency to which it will hold directivity. ~900hz seems to be about where the 12" seos comes in, which is rather amazing and should be fine for directivity matching to any 15" woofer.

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Old 04-24-2013, 02:48 PM
 
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But the reflections do cause impedance mismatches, don't they? Maybe it's the other way around but in either case I can see sharp spikes right at those frequencies. Isn't that the point (or at least one of them)?
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Old 04-24-2013, 02:57 PM
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"But the reflections do cause impedance mismatches, don't they?"

no. it is the other way around.

the easiest way to see it is to think of a horn on a baffle with sharp edges from the horn to the baffle. the air in the horn presents a different load on the c.d. than the air in front of the baffle. when the sound transitions from the horn to the room, it will hit an apparent "wall" at the mouth of the horn. when this happens, some of the sound is reflected off this invisible wall back into the horn where it is then reflected again before making its way out of the horn.

large roundovers largely eliminate that impedance mismatch.

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Old 04-24-2013, 03:04 PM
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Hey anti suck. I think Wayne is more interested in power response than most of the SEOS guys. Like myself, I target a flat direct sound on axis. Because its got directivity, there ends up less "brightness" in the room, is my logic. Also, these designs often use lots of toe in, so you end up with a sloping response on the listening axis. Bill goes so far as to measure and design on this axis. That's my perspective. Designing for power response or direct response both have pros and cons.
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Old 04-24-2013, 03:08 PM
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Quote:
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I agree, it just seems counterproductive to have the h290c vs seos argument for about the 50th time. This thread was supposed to be about the difference between two speaker designs.



vs



Pretty easy to see where all of the SQ difference between the two designs are, and why this horn argument is ridiculous....

These measurements were made with the original Eminence horn.

Parham recently released a mod for the H290C based 4Pi speakers that supposed to address the on-axis hump at the crossover region.


My guess though if Parham could cross them lower, he would if only to match directivity of the woofer better.
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Old 04-24-2013, 03:19 PM - Thread Starter
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Quote:
Originally Posted by SXRDork View Post

To the OP,

I have just personally built 2 of the 4Pi kits in their basic configuration (Emminence compression driver and woofer) and am very happy with them. I had been lusting over them for a couple years before I got the space and $$$ to buy them back in December. I actually bought 3 kits for my LCR but have not put the 3rd kit together yet. The quality of the components from the drivers to the crossovers are very high. Even though most seem to go for the JBL woofer upgrade, let's not forget that the Emminence woofer is a great woofer. I did not go for the upgrade because the difference between the two, from Wayne's accounts, was in the distortion at high SPLs. These speakers have so much headroom in my basement living room theater that I was not concerned enough with that difference to justify the added cost. Going from my Klipsch RF-82s to these 4 Pi's was a huge upgrade. Even without running a center channel, movie and TV dialog is very much improved. Overall, things just sound much better than with my Klipsch's.

Now for my comparison between 4 Pi's and SEOS designs. I think that the aesthetics of the 4 Pi design are rather poor and prefer the looks of the SEOS designs. I think they both employ design philosophies that I agree with. I bought the 4 Pi's because I had been reading about them and Wayne's design philosophy for years and was comfortable with what he is selling. I had not been keeping up with the rallying thread here or the econowave thread simply because the post count had gotten so high that I did not have time to get through them and I was, therefore, less comfortable with what was going on in the SEOS design. I also bought the 4 Pi's because they came with assembled crossovers on a PCB. For me, that was just a really nice to have item. Now that some have been actually building the SEOS designs and posting their impressions of them I would feel much more comfortable with buying a SEOS design.

In fact, if I made the purchase today, I would likely have chosen the SEOS design based on aesthetics over the 4 Pi. I think both designs are great values and both are an obviously huge upgrade over the Klipsch speakers I was previously using. I really don't think there is a bad decision to be made.

Thank you for this!
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Old 04-24-2013, 03:24 PM
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17+ years ago, jbl came out with the 3677. 15" woofer, 90x40 horn bi-radial horn (like the eminence h290), 1.2khz crossover. ;-)

http://www.jblpro.com/BackOffice/ProductAttachments/3677SpecSheet.pdf

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Old 04-24-2013, 03:34 PM
 
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Quote:
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"But the reflections do cause impedance mismatches, don't they?"

no. it is the other way around.

the easiest way to see it is to think of a horn on a baffle with sharp edges from the horn to the baffle. the air in the horn presents a different load on the c.d. than the air in front of the baffle. when the sound transitions from the horn to the room, it will hit an apparent "wall" at the mouth of the horn. when this happens, some of the sound is reflected off this invisible wall back into the horn where it is then reflected again before making its way out of the horn.

large roundovers largely eliminate that impedance mismatch.

Agreed; Impedance mismatches cause reflections. That's one of the things to avoid. The 1/4 and 1/2 wave modes are reflections from the apparent "wall" at the mouth of the horn. There are other reflections possible too, like from a sharp edge or a mismatch between driver and horn. We want to avoid those too. That is my understanding anyway.
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Old 04-24-2013, 03:41 PM
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Re: JBL 3677

I also had thought about buying these but the added height and width of the cabinets was undesirable to me...

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Old 04-24-2013, 03:50 PM
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Seems like the 4pi is designed with a drooping high-end response in an effort to combat "horn honk". Is that a fair statement? And is a rolled-off high end the ideal situation, wouldn't that remove some of the "sparkle" and "air" to music?
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They do not sound rolled off to my ears and I like some sparkle in the voicing. Vocals are very lifelike and cymbols are crisp. I would say they are voiced fairly neutral.
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Old 04-24-2013, 04:51 PM
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Originally Posted by hometheaterdoc View Post

I almost missed this..... any more elaboration on where packaging is in the grand scheme and when to expect some of the group buy stuff to be going out? Thank you.

Most of the BMS stuff should be finished up this evening or by tomorrow morning. Yours just got done about an hour or so ago. I should be able to get your SEOS-24's done as well later this evening. I bought a SEOS-24 with a 1.5" throat like you did. It looks like we will have to drill our own bolt holes. No big deal though. Iwatas need a box that I'll have to pick up tomorrow or Friday.

I've got to catch up on something for Coctostan and PassingInterest that took much longer than it should have, then I'll feel more comfortable about starting the SEOS-15 preorder. I have a decent number of kits to package up, but most people know it will take me about a week to get them done, so I will have some spare time to get the preorder posted.
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Old 04-24-2013, 04:55 PM
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Good to hear Erich. Thanks for getting the 4550 off to Matt. I know you're busy. wink.gif

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Old 04-24-2013, 05:01 PM
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Excellent, Erich! Thanks so much for the update! I got my tracking info just now. Perfect.

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Old 04-24-2013, 05:54 PM
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Quote:
Originally Posted by djkest View Post

Seems like the 4pi is designed with a drooping high-end response in an effort to combat "horn honk". Is that a fair statement? And is a rolled-off high end the ideal situation, wouldn't that remove some of the "sparkle" and "air" to music?


I have not heard that the HF roll-off is to combat honkinnes.
With proper toe in, both the Sentinel and the 4pi would have similar HF roll off slope.
4pi sound terrific to my ears. I do not feel they lack sparkle or air.
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Old 04-24-2013, 06:06 PM
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Hey anti suck. I think Wayne is more interested in power response than most of the SEOS guys. Like myself, I target a flat direct sound on axis. Because its got directivity, there ends up less "brightness" in the room, is my logic. Also, these designs often use lots of toe in, so you end up with a sloping response on the listening axis. Bill goes so far as to measure and design on this axis. That's my perspective. Designing for power response or direct response both have pros and cons.
Thanks for your perspective tux. I'll be using Bill's crossover, it will be interesting to see how that translates.
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Old 04-24-2013, 06:19 PM
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This is actually of interest to me, in the context of the thread's original question. Lots of different opinions around as to the merits of a downward FR tilt, and what's the "best" to shoot for with different types of speakers (particularly controlled directivity vs. not so much).

When I finally get around to building my SEOS12/DNA360/TD12X speakers (woofers arriving next week, still have to order the rest) I'll likely want to play with this by way of equalization. I'm a music guy first, with HT trailing behind by a bit.

Anybody have any thoughts on flat vs. tilted, particularly in CD designs and particularly geared toward a satisfying music experience?[/quote]

I am totally in the same boat as you. I am planning a SEOS15/TD15M/BMS4550 build. I have everything coming except for the SEOS15's and with Erich's announcement on the plastic SEOS15's coming, I am pumped.

I am planning on going active for these just to experiment with the different tilts, crossovers, etc. I have never used active before, so I am excited to both learn about something new and also discover what I like as far as response. I have found that I like a flatter response for music but I like the top end a little more subdued for movies, though it certainly differs based on the content.

This has been a very lively discussion and interesting to follow. I am definitely in the court that every design or for that matter has its set of compromises that are made based on what the desired end result is. Once you define what result you want then you can discuss which compromises are "Good" or "Bad" based on how they contribute or take away from your goal. Coctostan really summed it up nicely I thought.
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Old 04-24-2013, 07:13 PM
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"Seems like the 4pi is designed with a drooping high-end response in an effort to combat "horn honk". Is that a fair statement?"

no. the drooping high end response is that way because it sounds better (to many).

...


"I also had thought about buying these but the added height and width of the cabinets was undesirable to me..."

the polyimide drivers are a little better as well.

...

"Anybody have any thoughts on flat vs. tilted, particularly in CD designs and particularly geared toward a satisfying music experience?"

if you plan to listen on axis, a downward tilt might be preferred. if you plan to listen off axis (speakers aimed such that they cross in front of the primary listening position), then a flatter on axis response might be the way to go because off axis will have a little less energy up there as it is.

Listen. It's All Good.
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Old 04-24-2013, 07:55 PM
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Quote:
Originally Posted by Ash R View Post

Agreed; Impedance mismatches cause reflections. That's one of the things to avoid. The 1/4 and 1/2 wave modes are reflections from the apparent "wall" at the mouth of the horn. There are other reflections possible too, like from a sharp edge or a mismatch between driver and horn. We want to avoid those too. That is my understanding anyway.

Ash, you should check out the SEOS-15 then. It has a 1/4 mode around 900hz which pushes any impedance matching issues below the crossover region. Like LTD mentioned, the larger mouth radius (compared to the H290C) also lessens this effect as can be seen on the SEOS-12 measurements. There is also the SEOS-18 which has a 1/4 mode around 800hz.

Since you have met Wayne in person, maybe you can ask him his opinion of the JTR Noesis. It uses a BMS coax CD on a 7" deep 60deg horn with a crossover in the 500hz range, below its 1/4 wave mode. I haven't heard it and I've never tried something that extreme. The horn used also has a more abrupt mouth transition (vs the very gradual SEOS transition). Interestingly, the Noesis has been getting rave reviews across the board. I haven't auditioned them myself. I don't think Wayne peruses AVS and he probably isn't aware of the Noesis. Do you live near him?
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Old 04-24-2013, 08:39 PM
 
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I have pm'd and emailed Wayne too much, I'm sure. As others have said, he always gives thorough responses. I don't think it's right to post private emails but I can tell you he puts a high priority on keeping standing waves out of the picture, not just in his waveguide but in everything: the cabinet and drivers too.

He choses drivers that sweep clean (some have standing waves on the cone, itself). He puts woofer and port where standing waves are less a problem. He designs crossovers that deal with what's left.

I was going to post this earlier but things got heated so I didn't. Wayne linked me to many documents on crossover design. You might have already seen them. Seems like there are a ton.

http://www.pispeakers.com/Speaker_Crossover.pdf
http://www.pispeakers.com/Speaker_Crossover_Lab.pdf

Wayne did tell me about the SEOS15 and said the same as you, that it was probably more like the H290C. He is pretty convinced that waveguides need to be long enough to compensate for poor loading. As you said earlier, he also says, it's all about a balance of "competing priorities".
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Old 04-24-2013, 09:12 PM
 
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I don't know anything about the Noesis but something you said about it connects a dot with something Parham wrote about conical horns and waveguides. To paraphrase, his way of looking at them is the throat size and wall angle set the cutoff and mouth size then becomes a function of length, which sets the strength of reflections and ripple. I think I have that right (by emails and forum posts) but here is one that talks about it that can be used to check my facts:

http://audioroundtable.com/forum/index.php?t=msg&&th=18483&goto=76359#msg_76359

(Read past the crossover part)

I think the implication of this is a waveguide with narrower wall angle can be used at lower frequency. I do not know by how much though. It just clicked with me when you said the other horn was 60 degrees.
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