@mikessi I wonder if they also use a different polymer for the surround vs diaphragm. The impedance curve is awfully clean with just one primary peak at Fs, but hopefully its not over smoothed like many companies do. The HF108 is also capable of going under 1k with a steep slope and still remaining clean. I have one in an Eminence 12" neo coax crossed @ 900 hz. It sounds pretty nice, even when its louder.
Alot of these big diaphragm 1" CDs can really go low. I look for the ones that really do well under 1k to adhere to my midband integrity protection scheme.
The CDX1-1430 is for example excellent over 3k on a nice small seos horn. Thats good for a hotter dome mid to pair up with. I wonder how good the $30 Hivi DMB-A is in a WG?
Alot of these big diaphragm 1" CDs can really go low. I look for the ones that really do well under 1k to adhere to my midband integrity protection scheme.
The CDX1-1430 is for example excellent over 3k on a nice small seos horn. Thats good for a hotter dome mid to pair up with. I wonder how good the $30 Hivi DMB-A is in a WG?
I was able to purchase a pair of these domes from Playback Distributions. They only had one pair. I bought the pair. These are the ones in their newer PMC hifi speakers
@profiguy -- from the audioXpress test bench:
Features for the SB Audience 44CDN-PK include a 1” throat exit designed for use with 1” horns, a 44.3mm (1.75”) diameter voice coil wound with flat copper-clad aluminum wire (CCAW) on a high temperature Kapton non-conducting former driving a single piece PEEK diaphragm and surround (Photo 2). Other features include a FEA-optimized neodymium (neo) ring magnet motor structure, a cast-aluminum damped rear chamber, a 60W AES power handling rating (120W maximum power handling defined 3dB over nominal), a 1.8kHz recommended crossover frequency (with a minimum 12dB/octave high-pass network), an annular phase plug design, and a 1W/1m 109dB sensitivity.
Features for the SB Audience 44CDN-PK include a 1” throat exit designed for use with 1” horns, a 44.3mm (1.75”) diameter voice coil wound with flat copper-clad aluminum wire (CCAW) on a high temperature Kapton non-conducting former driving a single piece PEEK diaphragm and surround (Photo 2). Other features include a FEA-optimized neodymium (neo) ring magnet motor structure, a cast-aluminum damped rear chamber, a 60W AES power handling rating (120W maximum power handling defined 3dB over nominal), a 1.8kHz recommended crossover frequency (with a minimum 12dB/octave high-pass network), an annular phase plug design, and a 1W/1m 109dB sensitivity.
If one intends only ever to play up to 95dB or so, maybe 100dB absolute peak, what's the lowest 2nd order point you would recommend for the d7608 with the rear chamber you've been working on? I just made payment for some woofers I hope to mate mine with, and am looking forward to starting to play with them
@mikessi I did two prints of the D7608 chambers out of ABS. They weren't pretty due to weird settings with new filament I previously haven't used, but functional. I took pictures before I stuck them in the small test boxes I made for my son's monitor project and for some reasons I couldn't find them in my phone, but the original chamber design worked well. At least I'll have those measurements once I transfer the whole folder from the laptop.
@stv I'd say its ok to post the files on here for people to print from. The design is close enough to print unmodified as long as the infill ratios are high enough. 50 - 60% is probably more than enough for adequately stiff walls. Might be a little resonant for standard PLA depending on grade. Printing it inverted (open side up) is likely the orientation that will yield the lowest print time. You will need to tweak the inside ID to fit exactly on the D7608 motor. I don’t recommend extending the inner center post of the back toroidal shape so that it touches the motor. I'd use a good quality contact adhesive to attach the chamber around the inner ID to motor edge so it can be removed later. You can also attach the chamber to the enclosure opening for the mid. Id personally do the later, as its a bit simpler to make dampening changes on the fly, not needing to be constantly re-glued.
People can post questions in the D7608 thread or here, but its probably more organized and logical to have it in the specific D7608 thread.
The lowest cutoff for the D7608 with a basic LR2 or BW2 filter is 600 hz for acceptable lower mid output / THD ie. 100 dB max in room SPL for the stereo pair. It will also depend on the mid's distance to floor, walls, speaker baffle width, crest factor and overall EQ the music was treated with. I can't overemphasize how much a wide baffle will reinforce the lower mid output.
Anyone who uses the design, please dont share or host the files outside of these forums. You're welcome to augment or adapt the design for your own personal needs but please don't repost a changed file without asking me first. This is to avoid any confusion.
Please feel free to post all measurements and other details of your build using the D7608 on here if you so wish. I just ask that the chamber model files aren't used commercially for profit.
Again, I'd like to thank stv for his time and efforts in getting this done for us.
@stv I'd say its ok to post the files on here for people to print from. The design is close enough to print unmodified as long as the infill ratios are high enough. 50 - 60% is probably more than enough for adequately stiff walls. Might be a little resonant for standard PLA depending on grade. Printing it inverted (open side up) is likely the orientation that will yield the lowest print time. You will need to tweak the inside ID to fit exactly on the D7608 motor. I don’t recommend extending the inner center post of the back toroidal shape so that it touches the motor. I'd use a good quality contact adhesive to attach the chamber around the inner ID to motor edge so it can be removed later. You can also attach the chamber to the enclosure opening for the mid. Id personally do the later, as its a bit simpler to make dampening changes on the fly, not needing to be constantly re-glued.
People can post questions in the D7608 thread or here, but its probably more organized and logical to have it in the specific D7608 thread.
The lowest cutoff for the D7608 with a basic LR2 or BW2 filter is 600 hz for acceptable lower mid output / THD ie. 100 dB max in room SPL for the stereo pair. It will also depend on the mid's distance to floor, walls, speaker baffle width, crest factor and overall EQ the music was treated with. I can't overemphasize how much a wide baffle will reinforce the lower mid output.
Anyone who uses the design, please dont share or host the files outside of these forums. You're welcome to augment or adapt the design for your own personal needs but please don't repost a changed file without asking me first. This is to avoid any confusion.
Please feel free to post all measurements and other details of your build using the D7608 on here if you so wish. I just ask that the chamber model files aren't used commercially for profit.
Again, I'd like to thank stv for his time and efforts in getting this done for us.
Here is the modifed version of the shell with the flat bottom. This makes it much easier to print. I highly suggest you use the "adaptive layer height" function in the slicer. This will greatly reduce the layer line effect on the curved surfaces of the model.
Attachments
The original drawing of the D7608 chamber looks like this -
The actual diameter of the chamber opening is on average 3.590", derived from measuring 8 different units. You'll want to leave yourself about 0.005" wiggle room, otherwise you'll be doing some filing or grinding. Doing a test print to verify if your printer is close would save you potential headaches because most printers aren't that accurate in final dimensions. The 91.4mm ID is actually 3.598", so it has some variance already built in.
The actual diameter of the chamber opening is on average 3.590", derived from measuring 8 different units. You'll want to leave yourself about 0.005" wiggle room, otherwise you'll be doing some filing or grinding. Doing a test print to verify if your printer is close would save you potential headaches because most printers aren't that accurate in final dimensions. The 91.4mm ID is actually 3.598", so it has some variance already built in.
That'd be great thank you! It's cool you'll be using D7608's. Will be interesting to hear your comparison to that mid dome you special ordered that's used in the speaker you heard at AXPONA
A taper fit could be beneficial if the taper is just right. I get a little concerned about using adhesive with this, mainly because it can become a little too aggressive of a fit.
I had an issue with a 75MX41 that wouldn't budge. The motor became distorted in shape from someone trying to pry. By the time I stepped in trying saving it, cutting a slit in the side of the chamber. After that, I used enclosure mounted chambers.
The little Visaton plastic half round chamber is actually a good fit for a universal type of enclosure for the D7608, but it doesn't have the toroidal shape. A good compromise is to use a piece of pyramid shaped foam glued to the inner back side with 3M spray contact adhesive.
I had an issue with a 75MX41 that wouldn't budge. The motor became distorted in shape from someone trying to pry. By the time I stepped in trying saving it, cutting a slit in the side of the chamber. After that, I used enclosure mounted chambers.
The little Visaton plastic half round chamber is actually a good fit for a universal type of enclosure for the D7608, but it doesn't have the toroidal shape. A good compromise is to use a piece of pyramid shaped foam glued to the inner back side with 3M spray contact adhesive.
I'd like to see the inner workings of that mid if at all possible and which manufacturer is involved. Looks like a well engineered product.
I'm looking at a small 3 way made from a pair of 8", a Visaton DSM50FFL and Seas 22TAF/G with the flats cut off to get closer to the mid and have similar faceplate cosmetics. Hmm... way too many ideas and not enough time...
Here's a slight chamfer/fillet. Should make it a little easier to fit.
All I have are a couple pictures of the back of the dome. If you just snap me a picture straight down the side (perpendicular to the side of the dome's back shell), I can use that picture to perfectly match the taper. Just send pic with a ruler along the top for dimensioning.
It will be about a month before it gets here. I know as much about it as you do at this point but should be fun to play with. I did speak with the loudspeaker designer at AXPONA. He said his waveguide was part of the magic. I will definitely put that to the test. The waveguide does allow the dome to be mounted a bit further back which should also help with Z offset in relation to the woofer.
After hearing a speaker with the D7608 I want to try to use it.
I have read most of the thread, and this is what I have taken as pointers:
Audax TW025A28 and TW034 work well (XO @3.5k). Would the metal dome be better?
Audax HM210C0 works well as mid-bass (XO +/-@600). What is the recommended closed volume?
This driver combination with WWMMT would have quite high sensitivity, but it would be perhaps larger than what I want to try now.
Other drivers have been suggested, but I like these and the price is good.
Any other woofer suggestions (for a 3 way)? Perhaps a 10/12 o a similar price that does not need a big enclosure (sealed)?
I have read most of the thread, and this is what I have taken as pointers:
Audax TW025A28 and TW034 work well (XO @3.5k). Would the metal dome be better?
Audax HM210C0 works well as mid-bass (XO +/-@600). What is the recommended closed volume?
This driver combination with WWMMT would have quite high sensitivity, but it would be perhaps larger than what I want to try now.
Other drivers have been suggested, but I like these and the price is good.
Any other woofer suggestions (for a 3 way)? Perhaps a 10/12 o a similar price that does not need a big enclosure (sealed)?
I'll be using the d7608 in a sealed tower speaker with sb26stcn for tweeter and dual ScanSpeak 22W/8534G00 for midbass. Had originally planned on doing a standmount with the 22W/4534G00, but someone offered to sell me 4 of the 8 ohm version, and I pivoted to this. Don't know if it'll be a 3 way or 3.5 way yet. Will probably try both