Copying content from the original thread main post verbatim. Design by CJD; Original build thread author âkâ
D.A. Khanspire – An RS150/225 WMTMW
Edit: See also the Khancenter: http://divine-audio.com/khanspire
Edit: See also the In-Khan-Neatos: http://divine-audio.com/in-khan-neatos
NOTICE 11/29/10: Parts Express has discontinued the original RS Shielded drivers these were designed for. CJD has done some limited testing of the new unshielded 8 ohm drivers and believes that they are near drop-in replacements in the Khan designs. No alteration of the crossover is believed to be required in the standard sealed condition. Ported alternatives may require slight changes in the box size and tuning. See the Statements for ideas. Also note, the RS28F fabric dome tweeter can also be substituted without crossover modifications. If you have questions, please start a new thread in the main forum.
I’m here to announce a new project just getting off the ground. CJD has graciously agreed to help me design a new pair of front speakers. We’re currently in the early planning phases. This thread is more of a way for Chris and I to swap info, since our PM boxes are filling up and email access is limited during the day. And hopefully, the design process will go slow enough and I don’t wear out Chris’s patients by asking lots of questions for me to learn the art of speaker design.
So some of the goals and parameters:
1) I’ve listened to CJD’s big Dayton RS 3-ways a couple of times now and have really enjoyed them. CJD RS 3-ways Unfortunately, these are a little too big for my room. I don’t have the depth from the back wall for them. So, I want something with a very similar sound, just a step down.
2) I want an MTM. There have been several threads recently with comments about having more drivers in the midrange where the most music is.
3) I was originally thinking a wwmtm like Chris’s. But after seeing Jim’s beautiful Statements, I was hooked. (Hence the reason I was so willing to do the SketchUp model for Jim.) So, were going with a WMTMW just too look cool. The only limitation is that I’m going to need to limit the overall height to 55″, so that it is visually lower than my 50″ TV by a few inches. I think the dimensions are going to end up very similar at 54″x11″x14.5″ for around 100L gross.
4) I’m always going to have a sub. So, I don’t need a lot of extension. We’ve agreed upon a crossover in the 50-60hz range. Low Q, sealed RS225 in a 65L box gets us a F3 around 58hz, so this works good.
5) Good off-axis response for a nice wide sweet spot. My room has two recliners on either side of the famous basement pole. The pole is nearly centered on the TV, so my seat is not in the sweet spot.
6) Price for the drivers is ~$350/pr. I’m anticipating a total cost for the project to be around ~$700 – $800/pr. (Correct for when I built them)
7) Something that would be easy to build matching center and surrounds for.
Edit: Matching center design done here: http://htguide.com/forum/showthread.php4?t=28262
So, anyway I think that is everything so far. The current plan is for us to hammer out a design here, then for me to build the box and buy the drivers, drive the boxes up to Chris, Chris will do the testing and refine the crossovers, put together the cross-overs, leave them with Chris for a while to tweak, do some listening together for some final voicing, and them cross my fingers and hope that Chris lets me bring them home rather than keeping himself.
EDIT:
Speakers are done. I’m really enjoying them. They came out perfect. See this post for some listening impressions from the 2007 Iowa DIY:
http://htguide.com/forum/showpost.ph…&postcount=450
Cad Layout
(Use with a little caution. I tend to wing things in the shop.) Note that the tweeter is offset 1/2″ and the mids are offset 1/4″ from center. 1″ round over on the vertical edges, top horizontal edge optional. This is how I built mine. If I had to do it over, I might eliminate the brace below the lower woofer to allow for more crossover placement room. Also not shown in the Cad layout is some feet or stands to lift them up another 1-2″ to ear height.
It has been pointed out that the 54″ height in the front view does not match the side view. Use 54″. Also, the brace heights are approximate.
Pic of Khanspire (w/o drivers) next to CJD’s RS 3-ways
Updated/Final Crossover:
Notice pricing has increased for all the designs in this section of the forum. People should use the BOM’s and check with suppliers for current prices
Bill-of-Materials, as of 12/26/08
Upgraded parts highlighted in Yellow and are optional and will make very minor, if any, improvements. You don’t have to do all of the upgrades. If you like, you can pick and choose. The really expensive binding posts in the Upgraded are really overkill, but this is what I used.
Please consider buying as much from our forum sponsor as possible. However, I’ve heard that additional savings can be had by buying some of these parts from http://www.erseaudio.com/ . Their caps are supposedly good.
Woofer (Note the woofers are wired in parallel with reverse polarity)
Mid (Note the mids are wired in series.)
Tweeter
If you build these, please let CJD or I know to make sure you have the most current/correct info.
FAQ:
1. What is the Sensitivity and Ohm rating on these?
–>The design is rated nominally at 4 ohms and 90db sensitivity. The impedance dips a little bit below 4ohms, so a good amp should be considered to get the most out of these. But, I have listened to them in 2-channel mode using a Pioneer 1015TX, and didn’t notice any obvious problems (bass was a little less in pronounced, etc. but no protection faults or clipping). YMMV – especially if you drive 5 channels with all 4 ohm rated speakers. But, my Outlaw 7500 really makes them sing! They dynamics and punch is very impressive.
2. Is the roundover required?
–>The mids and tweeter were measured in box, with the roundover in place. So, the crossover does take into account the edge treatment. Some people claim that the roundover doesn’t make a difference. However, below is the simulated response of the mids and tweeter. You can see the difference the roundover makes. I think it can be quite a bit from 0″ to 1″ The difference between 0.75 to 1″ is small.
Driver 2 is the tweeter. The other 2 drivers are the mids.
Note that the roundover is only needed on the vertical edges. This is to smooth the mid and tweeter response. The top away is too far to impact these. The woofers don’t really benefit from the roundover due to the low frequencies they are playing.
3. What if I want more bass, can I build these ported?
–> Yes. I recommend that you use a 100L enclosure for the woofers, tuned to 24 hz. This is the similar the the Jim Holtz’s Statements. The easiest way to increase the box, is to build it 17″ deep with all other dimensions remaining the same. The port should be 3″ diameter, 4″ long with a precision flare at both ends.
BF_Brock built them ported as is very happy with them. See:
http://htguide.com/forum/showthread.php4?t=29004&page=1&pp=35
4. Why did you use both two different dampening materials on the inside (OC703 and PE Sonic Barrier)???
–> I had some OC703 on hand, so I used it. It should be even better than the Sonic Barrier at squashing internal reflections. However, the PE Sonic barrier will work great. Use the best / thickest you can on the back walls. For the budget minded, regular R13 fiberglass will work great. Other materials such as egg create foam, carpet padding, etc. are debated. Well respected people are both in favor and against these materials. I suggest sticking with the fiberglass, Sonic Barrier, Whisper Mat, or something you know to work well. Do a search if you have questions.
5. Can I use better crossover parts?
–> per CJD:
Inductors, stick to all air core with the appropriate impedance.
Caps, you could consider splitting the tweeter cap values in half and going with one high-end super fancy cap, one normal cap in parallel, OR just go fancy for the whole value.
Mid would be the next place to consider but it’s a battle of diminishing returns.
If you’re going these steps, hopefully you’re using a quality teflon insulated silver plated mil-spec wire (in the US I just source this from ApexJr – incredibly good prices) and real copper binding posts (Supras are – they’re $50… Cardas also does some). 12 or 14ga on the woofers, 14 or 16 on the rest. And running monoblocks right next to the speaker…
In other words… there are so many other places to throw away more performance (without even thinking about it perhaps) than you might gain from spending a ton of cash on tweeter caps…
5. How many other people have built the Khanspires?
–> So far, about two dozen. Me, bf_brock, FredT, phisch, RLHornbeck, jkrueger, Crackyflipside, HerrBender, and kirknelson. There are a few others that I’ve heard rumors of. If anyone else is out there, please step forward so CJD and I can collect royalties. (joke)
Link to Crackyflipside’s build thread
Link to RKHornbeck’s beautiful Khans with curved cabs
Jkrueger’s:
HerrBender’s
kirknelson’s
6. Can I change the box size?
You can not change the 11″ width! You can not change the spacing between the drivers!
You can reduce the depth and make them taller (either adding the extra height above or below the woofers). To keep the volume the same, I recommend: 62″Hx11Wx13″D.
You can’t reduce the depth any more than this, or you will not have sufficient space in the tunnel between the woofers.
7. I built these and they sound to bright!
Try experimenting with the stuffing in the mid chamber. It can make a very large difference. I have my walls lined with 1″ of OC703 and NO STUFFING. I have found that just a small bit of Acoustic Stuff stuffing in the mid chamber made them sound bright. If you use a different type of insulation, foam, padding, or whatever on the walls you will need to experiment with more or less stuffing to get them to sound right.
Also note, these speakers will never have a laid back or warm sound to them, but they shouldn’t sound bright.
8. What do I use for matching surrounds?
Lots of options. It depends on your needs and desires. JonMarsh’s Modula MT will work well, especially the in/on-wall version. CJD has put together a crossover for a small MT with the RS150/RS28 that would also work well. MarkK’s RS28/RS225 would also work well. And finally, coming Summer 2009, the In-Khan-Neatos. The plan is a RS180/RS150/RS28 in/on-wall 3-way.
9. Can these be used On-Wall behind an Acoustically Transparent Screen?
YES! On-wall is never perfect, but these will work. Phish and Crackflipside are actually doing just that.
CJD recommends some changes to the crossover. This will reduce the bass a little to account for the change in baffle step (maybe you don’t like that?) See here:
http://htguide.com/forum/showpost.php4?p=402628&postcount=526
Here are Phish’s completed speakers. WOW! Note that he centered up the drivers.
10. Should the tweeters be places on the inside or outside??
You should experiment and see what way you like better in your room. CJD recommends placing them on the outside:
Off-axis droop is less on the “wide” side of the tweeter – if you’ve got these closer to outside walls, this droop can actually help reduce initial energy from reflections through a rather critical upper midrange area, so you put the tweeters on the outside… counter intuitive, right? At the last Chicago DIY event I set up my MTM’s tweeter to the outside and of course some “ultra” audiophile type asked me why rather condescendingly (as in “why did you set those up wrong with the tweeter on the outside?”) – my reply: there’s 8 rows of chairs with lots of people… off-axis response is much smoother on the wide side, which means that, while the sweet spot isn’t as vise-like, it’s a better overall presentation for the group. He at least admitted he’d never even thought about that kind of thing…
11. Electrolytic caps in the woofer? What’s up with that?
In the BASIC Bom, I also switched the caps in the woofer circuit to electrolytic to save money. You have to wire the 100uf and 80uf together to get the 180uf speced. This saves about $34 per speaker. I consider this a big enough savings to warrant mentioning.
Discussions about caps get ugly real fast. I really don’t know the answer nor do I really care. Zaph and others use electrolytic caps, so they can’t be that bad. Some people would argue that they should be used throughout the crossover. The polypropylene I used are in the upgraded BOM.
12. Does this use the original RS28a tweeter with the ferro fluid, or the current version without the ferro fluid?
The Khans were designed with the current version of the RS28a tweeter that does not have the ferrofluid in them. These are better quality tweeters than the original version.
13. Can I use the RS28F (fabric dome) instead of the RS28A?
Yes. Minor difference in the response. You’ll get a little more top end above like 10khz, which some may actually like, but most won’t notice. If you put them behind a screen, probably a good idea.
