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Ambience tweeters

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Hmmm, a lot of variables in that topic. There were a few 60s/70s speakers (maybe an EV?)  with a tweeter on the rear but the idea never caught on since most customers wanted to tuck the boxes up against the wall or in a bookcase. The spacing from the speaker to the wall becomes more critical in that the "correct" distance for the "ambient tweeter" may be the wrong distance for optimum bass response. I'd rather spend the max I could afford on a good front mounted tweeter than divide the budget in half for two mediocre units.

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I've never heard them.  Do you have a link to an article or info?

 

Actually, in a liquor store I was once in, there were 2 Radio Shack supplementary tweeters of the kind Stereophile added to the Bozak Concert Grand for their review.  They were just plunked on a couple of shelves on opposite sides of the store (not near the main speakers), among all those diffusing/reflecting bottles!  They did sound fairly spacious and airy, I guess. 

 

Of course there were speakers in the past that were rear firing; Bose 901, some JBL Aquarius (as the name implied, they sounded best with a little vegetable aid), the Empire Royal Grenadier, etc.  PWK's response to these was that it would be hard to avoid a diffuse, reverberant field if the listener was far enough from the speakers.  He considered normal listening distance to be 16 feet.  I found that to be true in fairly "live" rooms, like my parents' old living room.  Here is a Realtor's picture of it, using the customary, deceptive, wide angle lens.  Back when I listened in that room, it had a large Persian rug, and diffusing wooden Venetian blinds, so it wasn't that "live" then.  The sound was marvelous!

image.jpeg.3b7842c5b3da65d3ea176c6406d1b570.jpeg

 

So ... when my wife and I moved into a new house, we built a music room/home theater of the same dimensions as my parents' room -- and, by coincidence, PWK's.  The sound is quite good, but not as spacious sounding as my parents' living room.  We are gradually removing absorbing materials from the room, bit by bit, while leaving the diffusers and vases, etc. in place. 

 

I heard of a guy who aimed the big mid/treble horn of the Altec A7 (I see the number 511B gliding through the mist of memory) toward the wall.

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Here is a link with a basic discussion on rear mounted "ambience" super tweeters: https://forum.audiogon.com/discussions/rear-firing-tweeters

 

I tend to trust the experience and knowledge of the people on this forum, hence the question.

 

I am considering using a couple of super tweeters in this application to possible give my Cornwalls a more open, "less confined-to-the-box sound".  The rear tweeter would be reversibly mounted on a 45 degree angle near the top, rear of the cabinet with an empirically determined (read: by ear) 6dB/octave crossover point (single capacitor) around 10,000Hz.

 

The Fostex FT17H may have potential:

 

https://www.madisoundspeakerstore.com/bullet-tweeters/fostex-ft17h-horn-super-tweeter/

 

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Crossed at 10kHz - you will see very little additional energy at the listener's position.

Above 10 kHz there is little energy to begin with (in the recording and playback).

 

BTW, in the 1970s, Infinity did this with their EMIT tweeters on some models. I had some, and noticed zero difference (they had a knob to dial them up or down).

 

Good Luck,

-Tom

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1 hour ago, Klipschguy said:

6dB/octave crossover point (single capacitor) around 10,000Hz.

 

Isn't 10K a little high?  As you say, you will determine this empirically.  My guess as a starting point might be just above the highest fundamental (4,186 Hz on the piano?), or split the difference??  The JBL Paragon crossed over to the 075 supertweeter at 7K.  The presence/absence of the tweeter was quite audible, yet didn't screw up the fundamentals.  I think at the HiFi fair they ran it turned up quite a bit.

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4 hours ago, garyrc said:

 

Isn't 10K a little high?  As you say, you will determine this empirically.  My guess as a starting point might be just above the highest fundamental (4,186 Hz on the piano?), or split the difference??  The JBL Paragon crossed over to the 075 supertweeter at 7K.  The presence/absence of the tweeter was quite audible, yet didn't screw up the fundamentals.  I think at the HiFi fair they ran it turned up quite a bit.

 

Well, 10KHz may indeed be a little high.  But, I don't think one would want too much overlap with the K77.  Of course, with a 1st order network the rear firing tweeter would only be down 6dB at 5KHz and 12dB at 2500Hz.  I would just have to grab a handful of different value caps, and listen to which one sounds the best - it should be pretty obvious with a little trial and error.  I would think the effect should be subtle for the best performance; after all, the Cornwall is a pretty well balanced speaker as is.  But then again, the whole idea may just be a bust, which is why I was asking...

 

BTW, lovely room you have there, Gary.  Thank you for posting.

 

Andy

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2 hours ago, Klipschguy said:

 

Well, 10KHz may indeed be a little high.  But, I don't think one would want too much overlap with the K77.  Of course, with a 1st order network the rear firing tweeter would only be down 6dB at 5KHz and 12dB at 2500Hz.  I would just have to grab a handful of different value caps, and listen to which one sounds the best - it should be pretty obvious with a little trial and error.  I would think the effect should be subtle for the best performance; after all, the Cornwall is a pretty well balanced speaker as is.  But then again, the whole idea may just be a bust, which is why I was asking...

 

BTW, lovely room you have there, Gary.  Thank you for posting.

 

Andy

I have a pair of super tweeters on top of my KLF-10's. I have tried them on every spot on top of the cabinet where they will fit. I have pointed them backwards, forwards, sideways, and tilted them at every possible angle.

 

Because your Cornwalls are already playing full-range, a supplemental tweeter in a front firing position anywhere near the other drivers is gonna cause "comb filtering", sharp dips in the frequencies being reproduced by both the main drivers and the extra tweeter, where they are experiencing destructive interference/phase cancelling. You can put it flush with the front face, or aligned with the diaphragms of the CW's drivers, or anywhere in between, they will still interfere. If you move the tweeter all the way to the back of the speaker, you might lose the original comb filtering, but you will get reflections off the top of the cabinet and a whole different set of interferences.  

 

The idea of a rear-pointing tweeter comes from the premise that with a large enough shift in time alignment, the external tweeter's outgoing information will be so far behind the information coming out of the mains that it will no longer interfere. In all the testing I did, this did seem to be the case, the comb filtering was eliminated. And, even if the external tweeters are pointing at a far back wall, a side wall, or a ceiling, you will get significant sound reinforcement and don't worry, you won't notice the delay.

 

But that doesn't mean all your problems are solved. For me, any back, or up, or side, or back-at-an-angle position didn't sound good enough. You do get nice high-frequency reinforcement and a more airy treble, but the downside is this: It diffuses the presence and forwardness of your midrange image. The little bit of midrange reinforcement that those tweeters are giving will soften your midrange and make it lose its focus.

 

Of course at this point you're thinking: "Well, I'll just give those tweeters a steep crossover slope, way up high, and that'll fix it". You're right, it will, but then you'll soon be realizing that with all that time, effort, and money spent on building crossovers, those tweeters are sounding pretty sweet and you bet they'd sound better pointing right at you. And you're back at square one. 

 

IMHO, the idea of a big shift in time alignment has merit. But I didn't like pointing them backwards. What I did was pointed them forward, place them as far to the back of the speaker cabinet as they would go, and I also lifted them up off the surface of the cabinet by a few inches. They are far back enough to lose most comb filtering, and up off of the cabinet enough, to not have significant reflections. It's easy to tell if you're getting reflections: With the tweeter in a interference producing position, sit in a chair up close between the speakers and listen to music while moving your head around. You won't just hear changes due to off-axis issues, you will find zones of extreme high frequency cancellation all over the place as you move your head around. In the position I now have my super tweeters, I no longer hear that. And I sit close to my speakers, as they are on either side of my desk in a near-field setup.

 

It's known that having the driver array of a speaker close together is better for time alignment and under normal circumstances, you wouldn't want your tweeter sitting so high, far from the other drivers, but in this case, we are trying to separate, so, at least for me, it works. The added lift is added distance. It's not the perfect solution, nothing is. But the forward, powerfully present midrange of a Klipsch horn driver was not something I wanted to compromise. 

 

Now, the KLF-10's are 16 inches deep, giving me a decent distance for a decent time shift. CW's may be deep enough too. You can always buy a low priced pair to try, mine were 20 bucks from Parts Express and I'm still enjoying them. I'll eventually get a pair of ribbons or something else nice. In the images, those are the tweeter covered by a microfiber cloth for a bit of attenuation, sitting on a 4x4 block with padded feet. And note that I didn't even get into the whole issue of how the tweeter will affect your speaker's impedance profile...

 

1086441939_2020-04-0822_56_09.thumb.jpg.f409a2cb147e500ac4e0631541029eb1.jpg247251109_2020-04-0822_57_30.thumb.jpg.84958e6477718c4fb1c8c5bfc9f7f341.jpg

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15 hours ago, Klipschguy said:

What do you all think about rear mounted ambience tweeters in home applications?

 

If you've got your speakers out into the room it'll probably have the effect you're seeking.  Otherwise, no.

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MechEngVic,

 

Thank you for the detailed response and sharing your own experience with an add-on super tweeter.  One thing for sure, I do not want to smear the midrange in any way as this area of sound is by far the most important aspect of a speaker's design (my opinion, of course). 

 

My preference would be for the sound presentation to have more depth and height and not be quite so localized to the corners.  I think a bigger room would help as I am only back about 14 feet from the Cornwalls in my dedicated music room.  As your post describes, it is all about compromise. 

 

Andy

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I'd like to say that I'm not a fan of the otherwise legitimate "it in the room" speaker positioning.  It's my opinion that speakers which don't have well-controlled directivity need such positioning, and those that do don't.  I was never a fan of Klipsch back in the day, compared to JBL, especially their "pro" stuff.  A few years ago I found myself with a very difficult room and decided well-controlled directivity would be a good ally.  Ordered a pair of Forte IIIs without even driving an hour to hear them, and am totally elated.  I played around some with positioning and found the best results roughly 8" from the rear wall.  Perfect.  Looks good and unobtrusive.  I highly doubt "ambiance tweeters" wood do a single "good thing" for me.

 

Just some expressed thoughts...

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ive never added an ambiance tweeter to more expensive standard front firing speakers but did add a tweeter to some cheaper small surrounds a long time ago that helped some for ambiance.  there are many speakers that have rear firing tweeters & mids, they are called bi-polar or di-pole & have a very wide open sound stage that fills the room eliminating the "sweet spot" that direct radiating speakers have.  a popular brand was sold by radio shack called linaeum which is a ribbon tweeter that fires front & rear, they had a line of speakers with the ribbon tweeters but you could also buy just the tweeter to use with other speakers, they actually sound very good. 

 

as for bi-polar speakers, most here have never heard them nor will consider giving them a chance, aside from the numerous klipsch speakers i own, i also have a bunch of definitive technology brand bi polar speakers & they are excellent speakers for both music & movies, but they really shine for home theater, the wide sound stage & ambiance they produce is very impressive, they fill the entire room & the sound is excellent in all seating positions. they have a very good cabinet build with bracing & very thick boards, no need for cabinet mods in these & you will never have cabinet glue/vibration issues with them like many klipsch models!  & they dont need to be out in the middle of the room, def tech suggests ~6-12" from the back wall so they still have corner loading for improved bass.  def tech was founded by one of the original guys from polk & have been around for 20+ years & get just as good of reviews from their owners as klipsch.  there are benefits to rear firing tweeters if they are designed right, but just adding a tweeter to the rear of a direct radiating speaker may not have the same results.  

 

 

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I was at a dealers last fall and he demo'd an interesting spin for added depth. He had one of these free standing tweeters at the top rear of each speaker directed at the wall for reflectance. I A/B'd it and felt it made a noticeable and satisfying change to the sound, adding significant depth. Facing forward did not have the same impact or interest. Amazingly, they are named "Taket Batpro2."  They are all over Fleabay at about $450/pair.  They are about the size of a pack of cards, have 100dB effeciency and a 5 step attenuator. I thought in the right circumstance I might try a pair, but with La Scalas and my current room acoustics, it would less than satisfactory. Just throwing it our for what its worth.

 

Mike

 

 

 

Taket Batpro 2.jpg

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3 hours ago, michaelwardjoines said:

I was at a dealers last fall and he demo'd an interesting spin for added depth. He had one of these free standing tweeters at the top rear of each speaker directed at the wall for reflectance. I A/B'd it and felt it made a noticeable and satisfying change to the sound, adding significant depth. Facing forward did not have the same impact or interest. Amazingly, they are named "Taket Batpro2."  They are all over Fleabay at about $450/pair.  They are about the size of a pack of cards, have 100dB effeciency and a 5 step attenuator. I thought in the right circumstance I might try a pair, but with La Scalas and my current room acoustics, it would less than satisfactory. Just throwing it our for what its worth.

 

Mike

 

 

 

Taket Batpro 2.jpg

Correct me if I'm wrong, but don't these emit sound from both sides front and rear?

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What could be interesting to experiment is to use an active crossover and a small class D amp - the active crossover in parallel with the main amp and only filtering the output for the add-on tweeters... that way you could continuously play with cutoff frequency and level - now to know if it would sound good? would probably be very different from the single cap, first order filtering - better or worse I don't know. 

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There is a much easier experiment. 

 

Turn you speaker cabinet toward the wall and play a 10kHz tone (with the volume knob set at its usual position). Sit at the listener's spot and honestly ask yourself: "do I hear anything, anything at all"?

 

I think you might be surprised and guess what, you just saved a bunch of money.

 

Good luck,

-Tom

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