Lots are selling homebrew cabinets.
Selling modified drivers alone would be hard,, indeed.
Building something for them, and "proving" the mods you did improved the experience, that might work!
Lots of karaoke places would love to go that low!
(just not in my backyard, ok!?)
And I believe some are starting to have systems not for karaoke, but actual real music or home theater systems!
Selling modified drivers alone would be hard,, indeed.
Building something for them, and "proving" the mods you did improved the experience, that might work!
Lots of karaoke places would love to go that low!
(just not in my backyard, ok!?)And I believe some are starting to have systems not for karaoke, but actual real music or home theater systems!
+1 that is indeed a beautiful K. Jessman makes really nice stuff. I wish he was in VA or WV so shipping to me and Freddi would not be much. Heck we could drive over to pick up the goodies.
That is a pretty low Qts, you probably want to minimize the Z chamber volume to the extent possible to control cone motion - so a shallow Z just enough to clear magnets and basket. Possibly add volume filler blocks in cavity space on backside of K aperture to ensure high frequency bandwidth. Use thick material for K aperture. I would even recommend making it CLD - sandwich thin rubber sheeting or even use pliable latex caulking to bond two 0.5in thick plywood sheets together. Add wood screws liberally to clamp structure together and prevent delamination in future. Are you going single driver each or dual 18in in push pull??
Dayton RS225-8 & AMT KaZba
Well, the RS225-8's finally got here - they are beautiful drivers. Superb build quality, and what's more - some T/S parameters that are exceptional and hard to find even in other drivers at a higher price point. Nice cast frame, well made rubber surround, super hard anodized aluminum cone and phase plug. So I installed them into the KaZba and took the opportunity to widen the K-aperture and add ribs to its backside to strengthen it. There is no comparison between these and the cheap $10 drivers I previously had in here.
Here is a photo of the drivers installed inside with the AMT dipole tweeter on top, without the K-apertures:
I established a baseline response sans K-aperture and here is what the XO response looks like with some minor EQ'ing, LR4 @ 700Hz:
This is the corresponding HD - which looks excellent for how wide the bandwidth is:
And this is the impulse response - exceptionally tight:
Here is a detail of the frequency response and minimum phase at 5dB/increment and 1/48th oct smoothing with 4ms gate window applied (measurements at 0.5m and 0.71 volts)):
Ok, now we add the new K-apertures, and here a photo:
ANd this is what we get for frequency response as seen in the XO traces (magenta trace) - a bandpass peak appears at 250Hz and a dip appears near 350Hz, but the 700Hz XO region appears to be intact. The cyan trace is response with just the rear side K-aperture installed:
Here is the corresponding HD with both K-apertures - with an obvious increase in the harmonic distortion, I assume from the K-panel vibration:
and here is the corresponding impulse response:
As is typical of K-apertures, there is a strong dip/peak in the mid-bass, the good news is that it now extends above the initial dip from widening the aperture so that I can cross higher up with the AMT (the original goal). Listening to it, I am not sure I can really hear the anomalous response from 250-350Hz - which sometimes happens due to room modes. The aperture however, made the presentation of the sound more uniform over a wider range of off-axis listening angles, it visually decreased the cone excursion on kick drums. The sound of percussive instruments seemed to be tighter and this can be seen on the IR's which have less overshoot.
I think I have established that one can make a very successful Z-baffle dipole wideband (able to XO at 700Hz) bass unit using two 8in drivers in a fairly compact cabinet that can reach respectable low bass extension with clean harmonic distortion. I have sort of shown that a K-aperture can be applied to such a Z-baffle to make it a KaZba - but at the expense of coloration in mid bass, with usual advantages of afforded by K-apertures (wide dispersion, improved impulse, better cone motion control). The lesson learned here is the the KaZba cabinet needs to be made of sturdy non-resonant materials to resist the pressures involved to keep HD low.
Since I did not build it out of thick 3/4in ply (needed in this case), I think the added HD and coloration in the midbass is not worth it for me at this point and I would prefer to go to an open Z-baffle. However, if it were made of sturdy ply, I would go with the K-apertures (if HD goes down as I assume it would).
The neat thing for me was to see that I can have an all dipole speaker from 30Hz to 20kHz, and it sounds very good. Well, almost all speakers based on the Heil AMT sound very or exceptionally good. This is no different and reminds me why the Heil AMT is still the King of tweeters. Worth every penny...
Well, the RS225-8's finally got here - they are beautiful drivers. Superb build quality, and what's more - some T/S parameters that are exceptional and hard to find even in other drivers at a higher price point. Nice cast frame, well made rubber surround, super hard anodized aluminum cone and phase plug. So I installed them into the KaZba and took the opportunity to widen the K-aperture and add ribs to its backside to strengthen it. There is no comparison between these and the cheap $10 drivers I previously had in here.
Here is a photo of the drivers installed inside with the AMT dipole tweeter on top, without the K-apertures:
I established a baseline response sans K-aperture and here is what the XO response looks like with some minor EQ'ing, LR4 @ 700Hz:
This is the corresponding HD - which looks excellent for how wide the bandwidth is:
And this is the impulse response - exceptionally tight:
Here is a detail of the frequency response and minimum phase at 5dB/increment and 1/48th oct smoothing with 4ms gate window applied (measurements at 0.5m and 0.71 volts)):
Ok, now we add the new K-apertures, and here a photo:
ANd this is what we get for frequency response as seen in the XO traces (magenta trace) - a bandpass peak appears at 250Hz and a dip appears near 350Hz, but the 700Hz XO region appears to be intact. The cyan trace is response with just the rear side K-aperture installed:
Here is the corresponding HD with both K-apertures - with an obvious increase in the harmonic distortion, I assume from the K-panel vibration:
and here is the corresponding impulse response:
As is typical of K-apertures, there is a strong dip/peak in the mid-bass, the good news is that it now extends above the initial dip from widening the aperture so that I can cross higher up with the AMT (the original goal). Listening to it, I am not sure I can really hear the anomalous response from 250-350Hz - which sometimes happens due to room modes. The aperture however, made the presentation of the sound more uniform over a wider range of off-axis listening angles, it visually decreased the cone excursion on kick drums. The sound of percussive instruments seemed to be tighter and this can be seen on the IR's which have less overshoot.
I think I have established that one can make a very successful Z-baffle dipole wideband (able to XO at 700Hz) bass unit using two 8in drivers in a fairly compact cabinet that can reach respectable low bass extension with clean harmonic distortion. I have sort of shown that a K-aperture can be applied to such a Z-baffle to make it a KaZba - but at the expense of coloration in mid bass, with usual advantages of afforded by K-apertures (wide dispersion, improved impulse, better cone motion control). The lesson learned here is the the KaZba cabinet needs to be made of sturdy non-resonant materials to resist the pressures involved to keep HD low.
Since I did not build it out of thick 3/4in ply (needed in this case), I think the added HD and coloration in the midbass is not worth it for me at this point and I would prefer to go to an open Z-baffle. However, if it were made of sturdy ply, I would go with the K-apertures (if HD goes down as I assume it would).
The neat thing for me was to see that I can have an all dipole speaker from 30Hz to 20kHz, and it sounds very good. Well, almost all speakers based on the Heil AMT sound very or exceptionally good. This is no different and reminds me why the Heil AMT is still the King of tweeters. Worth every penny...
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hi X - - interesting work - it could be aperture flex contributing to the increased THD.
your AMT looks great and very nice summation with the Z-baffle
how about 2-back to back little fullrange ? - would that give a taste of the AMT's goodness?
based on baffle dimensions and aperture area, do you see a way to predict the cavity peak frequency?
here's a standard Karlson K12 with its slit vents sealed - the woofer is a DVC type sold by MCM and used in a Marshall Leach 2.1 project - I've not measured it as a direct radiator. As is, it probably would make a good helper woofer for fullrange crossed around 100Hz
your AMT looks great and very nice summation with the Z-baffle
how about 2-back to back little fullrange ? - would that give a taste of the AMT's goodness?
based on baffle dimensions and aperture area, do you see a way to predict the cavity peak frequency?
here's a standard Karlson K12 with its slit vents sealed - the woofer is a DVC type sold by MCM and used in a Marshall Leach 2.1 project - I've not measured it as a direct radiator. As is, it probably would make a good helper woofer for fullrange crossed around 100Hz
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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Sound clip with AMT
Here is a sound clip from the RS225 KaZba with AMT. Change the .asc to .mp3 in order to play the HQ 320kbit 48kHz sound clip. Same test track used for Subjective Blind Comparo thread. And also a drum solo for you to hear the dynamics and percussive accuracy.
Here is a sound clip from the RS225 KaZba with AMT. Change the .asc to .mp3 in order to play the HQ 320kbit 48kHz sound clip. Same test track used for Subjective Blind Comparo thread. And also a drum solo for you to hear the dynamics and percussive accuracy.
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My amp only goes to 70w max at 4ohms and that is far from xmax. I will have to run a sim to know. A single RS225 in a sealed box can go to 105dB. An OB is going to have losses. A pair of them would then be 3dB more for 108dB. So probably 100dB or so?
I think a single full range like PA130-8 in an open baffle can work very well on top of this. For more air add a super tweeter (dome or ring) and cross above 6khz. Tweeter does not need to be dipole.
However they will never be as good as the Heil AMT as the principle of operation is completely different. The very light membrane of the AMT coupled with its squeezing air operation makes for very sharp attack and quick decay. The CSD of an AMT is probably better than a dynamic cone or dome can ever achieve.
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A few questions:
Are the dimensions of the RS225 KazBa, the same as you used for the 10 buck speakers?
What are your X-over points?
I believe the Heil AMT is not available anymore or at least not at parts express.
There are some Dayton and Boston AMTs for sale there as well as some other ribbon tweeters. Which do you think might work, and could the RS225 go high enough without distortion to meet up with any of the possible replacement tweeters?
Are the dimensions of the RS225 KazBa, the same as you used for the 10 buck speakers?
What are your X-over points?
I believe the Heil AMT is not available anymore or at least not at parts express.
There are some Dayton and Boston AMTs for sale there as well as some other ribbon tweeters. Which do you think might work, and could the RS225 go high enough without distortion to meet up with any of the possible replacement tweeters?
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The RS225-8 required a slightly larger cutout, but that was resolved with a utility knife in foam core/cardboard laminate.
The XO point was 700Hz. The RS225-8 is an exceptionally good driver and capable of going up very high with low distortion. It's one of the few true woofers that sound almost like a full range when played full range.
I am not sure you can go high enough to XO with one of the budget AMT's which have a 3.5kHz XO point if using a K aperture. Without the K aperture and simply a Z baffle, the RS225-8 has no problem. Heil AMT is still available on eBay. I think that is how the company does its sales now.
There are also other pleated ribbon AMT's out there that will get down to 1kHz like the Beyma TPL-150. You will need to remove the rear chamber for it to be a dipole. That driver is highly regarded as well but I have not seen another AMT that can reach 600Hz.
There is this model from Dayton that can XO at 2.5kHz. It looks like you just need to pull off the rear felt pad to get a dipole. The transducer is quite simple - just two grill plates separated by a Nd magnet pair sandwiching the pleated diaphragm in between.
http://www.parts-express.com/dayton-audio-amt1-4-air-motion-transformer-tweeter--275-090
Pdf spec sheet:
http://www.parts-express.com/pedocs/specs/275-090s.pdf
Looking at the response, I think it will be smoother if you take off the rear chamber to reduce HF resonances. I always get a chuckle looking at impedance curve of an AMT. Flat.
The XO point was 700Hz. The RS225-8 is an exceptionally good driver and capable of going up very high with low distortion. It's one of the few true woofers that sound almost like a full range when played full range.
I am not sure you can go high enough to XO with one of the budget AMT's which have a 3.5kHz XO point if using a K aperture. Without the K aperture and simply a Z baffle, the RS225-8 has no problem. Heil AMT is still available on eBay. I think that is how the company does its sales now.
There are also other pleated ribbon AMT's out there that will get down to 1kHz like the Beyma TPL-150. You will need to remove the rear chamber for it to be a dipole. That driver is highly regarded as well but I have not seen another AMT that can reach 600Hz.
There is this model from Dayton that can XO at 2.5kHz. It looks like you just need to pull off the rear felt pad to get a dipole. The transducer is quite simple - just two grill plates separated by a Nd magnet pair sandwiching the pleated diaphragm in between.
http://www.parts-express.com/dayton-audio-amt1-4-air-motion-transformer-tweeter--275-090
Pdf spec sheet:
http://www.parts-express.com/pedocs/specs/275-090s.pdf
Looking at the response, I think it will be smoother if you take off the rear chamber to reduce HF resonances. I always get a chuckle looking at impedance curve of an AMT. Flat.
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wonder how a Kemo bug repellant tweeter would do for a PA130 helper? - have no idea how its supposed to measure
down lower than their graph
L010 Piezo Loudspeaker
down lower than their graph
L010 Piezo Loudspeaker
You need something that will go down to 10kHz to help the PA130 - your bug repellent tweeter looks more like ultrasonic territory.
Try the $30 Dayton AMT as super tweeter. You need to use an AMT type transducer to get the same feel - a piezo sounds cold and harsh and tinny by comparison.
http://www.parts-express.com/dayton-audio-amt-mini-8-air-motion-transformer-tweeter-8-ohm--275-095
The Aurum Cantus Aerostriction is probably the closest in price point and capability to Heil AMT. They can cross at 900Hz.
http://www.parts-express.com/aurum-cantus-ast30100-aero-striction-tweeter--276-442
Try the $30 Dayton AMT as super tweeter. You need to use an AMT type transducer to get the same feel - a piezo sounds cold and harsh and tinny by comparison.
http://www.parts-express.com/dayton-audio-amt-mini-8-air-motion-transformer-tweeter-8-ohm--275-095
The Aurum Cantus Aerostriction is probably the closest in price point and capability to Heil AMT. They can cross at 900Hz.
http://www.parts-express.com/aurum-cantus-ast30100-aero-striction-tweeter--276-442
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>>> I think a single full range like PA130-8 in an open baffle can work very well on top of this. For more air add a super tweeter (dome or ring) and cross above 6khz. Tweeter does not need to be dipole.
I've been listening to the PA130-8 for about a month or so and really enjoy it on open baffle. It's on an 18" square sitting on top of an H-frame. It's an excellent combo in my small apartment. I don't use a tweeter but personally enjoy a soft top end. I would imagine others would prefer additional tweet. I'd add a piezo before spending the money on anything more expensive. I don't like dome tweeters and my favorite tweeters are 1" compression drivers crossed above 8kHz for their lifelike reproduction and impact.
The PA130-8 has a clean, clear detailed midrange. It's easy to hear voices separated out on lush harmonies. It's not perfect (it's a little forward and gets fatiguing on extended sessions) but I find myself turning back to it again and again so it must be doing something right. I think it's a great little driver regardless of cost. Considering cost, it's one of my favorites.
I've been listening to the PA130-8 for about a month or so and really enjoy it on open baffle. It's on an 18" square sitting on top of an H-frame. It's an excellent combo in my small apartment. I don't use a tweeter but personally enjoy a soft top end. I would imagine others would prefer additional tweet. I'd add a piezo before spending the money on anything more expensive. I don't like dome tweeters and my favorite tweeters are 1" compression drivers crossed above 8kHz for their lifelike reproduction and impact.
The PA130-8 has a clean, clear detailed midrange. It's easy to hear voices separated out on lush harmonies. It's not perfect (it's a little forward and gets fatiguing on extended sessions) but I find myself turning back to it again and again so it must be doing something right. I think it's a great little driver regardless of cost. Considering cost, it's one of my favorites.
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