Ricci

This would be an interesting design. If you can try to use at least a 6" port for each driver. (180cm2 area). Dual opposing the driver will keep cabinet vibration down from the reciprocating driver mass.

Rev 2 to Rev 10...Lot's of refinement along the way it seems. Good luck!

On 7/6/2020 at 12:06 PM, Kyle said:

I tend to think its a glue problem, or primer problem. 

Agreed. Could be a loose shorting ring even. There's a lot going on in the motor and gap area. Could be the spiders not glued fully also. 

Hey...Welcome to the site. 

The first info needed will be details help anyone give advice going forward. 

Budget?

Planned use? Live sound / HT / Car audio etc...

Size? Restrictions, shape, etc.

Weight? Is this an issue?

Amplification? Will it be an NU1000 or multiple LG 14000's?

What frequency range of coverage is desired? 

Kipman I'll try to look into the user data limits with Kyle. It may be that you've maxed yours out rather than a hard limit on the size of the pics.

The car audio guys have been strapping multiple amps together to drive a single load for years. It's rare in pro audio anymore. Seems to be mostly back in the 80's and 90's. I've always heard that it can get messy if the amps gains aren't matched correctly. No hands on experience with this though.

8 hours ago, radulescu_paul_mircea said:

In the last 2 editions of Voice Coil magazine they measured the Eminence drivers, the 18" and the 21". 

Yep...The 21 Klippel data is from Eminence. I would've preferred to see it done by RedRock but a lot of the time RR seems to cut the data capture off before a long stroke driver is really pushed. They don't seem to ever go past 15mm so the data may not have been as indicative. The Eminence data certainly looks great. The Xmax based on the Klippel defined limits for subs is almost 19mm based on all 3 criteria. I was surprised by the suspension behavior. I knew the spider choice and arrangement was good but I thought the triple roll surround would start to tighten earlier.

On 5/9/2020 at 11:30 AM, Jesal said:

Hi Josh,

I'm building a couple of your CKRAM's.

Is it ok to use the circle cutout from  Baffle G (19.5") to use as Front Panel C (20.5")?

Or would this affect the response too much? Just trying to save some materials.

Should be fine. It'll only have a minor effect that would probably require measurements to notice. 

You would be looking at just 1dB or so. It won't be a huge amount. Also it would slightly change the tuning and relationship of the back chamber to the front expansion. 

Hmmm. They seem to work fine for me. Do you mean the amp test links in the first post? 

Here's my wish-list for amplifier power testing.

If it were me I'd not test full power sine waves any longer than 5 seconds or maybe 10sec if you really want something a bit longer. There's no point. Even the most dense EDM music has breaks and is not anywhere near 100% duty cycle averaged over 10 seconds. If somebody really needs sustained multi KW power it's probably not for music or HT and it's time to look at an AETechron. Definitely no need for 2 minute full power tests IMHO. Plus as you say that'll get expensive when things go BANG! 

I'd like to see a few different frequencies tested. 1kHz has been standard for years so I get that but on these huge tour amps that are used for subs I don't think it represents the use very well. Is anyone dumping 10+kW peaks at 1kHz? That's not a concert or theater I'd want to attend. I'd like to see 50Hz or 63Hz used to sim kick drums and typical music bass and 10 or 16Hz for judgment of the deep bass power. Most amps wilt at those deep frequencies. There's almost always less power in the bass. Some amps hold up better than others but it's hard to tell from the 1kHz testing.

Like I mentioned earlier I'd like to see something like this. 

1kHz: 1 cycle burst (Short term output)/ 6.5 cycle CEA-2010 signal burst (Typical music content output) / 5 second sine wave power vs time (long term output)

50Hz: Repeat above. 

10Hz: Repeat above

16kHz: Repeat above to gauge HF capability. 

The duration of the short term signals is longer for the bass frequencies as it should be. 1 cycle at 50Hz is 20ms and the CEA-2010 burst is 130ms. At 10Hz one cycle is 100ms and it's 650ms for the CEA-2010 burst, so it will be much tougher at the deeper frequencies. At 1kHz there is likely to be no difference between a 1 cycle or 6.5 cycle test. They are both so short in duration .I don't see anything less than a full wave cycle as useful data for the bass range though. The CEA-2010 signal is included in REW's tone generator, Clio and Don Keele's Igor pro program. It wouldn't be hard to sample it for use in other ways. 

Thanks for the data and discussion. Keep up the good work. 

MomoTon,

The bracing should be fine. 

You can't reduce the width of the cabinet really. The 21.5" frame diameter of the drivers plus the wall thickness doesn't leave much to gain there. The depth could be reduced as well as the enclosure height but you will be reducing volume for the ported chamber and the ports. You will have to change the port size/length in order to maintain the same tunings and low bass efficiency will be reduced and vent velocity would go up most likely due to smaller vent area. 

I look forward to seeing your finished project with the CF. This sounds like an adventurous build. 

Yep...Based on previous tests on various clones the burst power is huge and should meet spec but true sustained power is about 4kw give or take which will eventually throttle back even more. There really isn't enough in the AC line to support more sustained power in most cases unless on 240v with large breaker so most of the big "tour" grade amps cap out at about the same sustained power. Even multiple speakers really cannot handle that kind of sustained power anyway. Some of the old "iron" amps would do sustained power for at least a few seconds but the power ratings were lower and again you better bring a stout AC line.

IMHO amp power ratings should be based on duration of a 1 cycle minimum for burst, 6.5 cycle shaped CEA-2010 signal as a short term rating and minimum 3 seconds sustained for long term. 

That's one thing that the name brand tour amps seem to do better than the clones is protections from blowing into tough loads. 

On 4/13/2020 at 12:45 PM, peniku8 said:

The Voltage meter on the Pmillet is really accurate down to maybe 15Hz. I've compared it to my HoldPeak true RMS meter and they're always within 1%. I did measure it but forgot to save and post the data here, but I can do it right now. I'm typing this in the studio sitting here with all the equipment. Distortion was 0.002% loopback of my audiointerface and 0.003 with the pmillet I think in the loop. But I have a wierd issue where distortion increases up to like 1% at 19dbU. It's 0.002 when I measure the loopback at -5dbU, idk why that is. But I have a plethora of devices connected to the interface and can't take it out.

The case was 40€, the heating elements 9€ each inlcuding shipping from China (like wtf). I got them from Ebay here. Switches, connectors, cables, busbars maybe 60 total. 250€ total what is like 280$ or so. Acrylic you can get scraps at shops for like 5$ a pound.

Good stuff and thanks. The load bank investment wasn't bad at all. 

Usually when you see distortion creep up abruptly in electronics something in the chain is at the onset of clipping. 

Measurements for the Pmillet look quite good. 

I look forward to your amp tests!

Looks ok to me. I don't think you need the center puck if not using the star pattern. It's only used to anchor and align the star pattern bracing. 

Personally I'd leave the small braces in. They are for locking the baffle in place with the main brace and the port panel. There's not a lot of baffle area there and the baffle is swiss cheese. Not critical but I like to be sure the cab's are rock solid especially the baffle area. YMMV 

Excellent work. I look forward to your amp testing!

How do you feel about the Pmillet unit so far? 

Also about how much money do you have into the test load unit? 

Both of these drivers are really good. The 18Ipal has similar xmax. It's basically a dead heat in that department. The BMS probably has the lowest functional power handling due to the lightest, smallest voice coil. The 18Ipal is the most efficient (lowest Qts)

In a small room like yours and with relatively low volume playback,I'd recommend at least 2 compact sealed subs. 3 or 4 would be even better if you can spread them out around the room. This will even the response out over a wide listening area. If you can take a tape measure and figure out how big you would like the enclosures to be. Is a 21" cube ok? 18"? Smaller?

There are a number of popular cost effective drivers if you want to DIY? Are you looking to DIY or are you looking to buy a complete sub? 

If going DIY you'll want DSP and you'll need an amp. It's cheaper to have the DSP in the amp. The Behringer NX3000DSP or 6000 version are popular and cost effective. The fans are LOUD though but they can be modded with quieter fans. The amp that Kipman linked seems like a good option also. 

You'll also want to be able to measure your response in room to help dial in the dsp for the subs and integrate them into the rest of the sound system. REW is popular and free. All you need is a decent measurement mic and a sound card. The Umik system is poplar too. It's surprisingly cheap to get a setup going. $100 can do it. 

40 minutes ago, kipman725 said:

I have appeared to miss read the specs and just quoted the voice coil size.  

by distortion I was referring to high frequency THD which is limited by air non linearity and not low frequency distortion so I can confidently make this statement because the phase plug design of the AXI2050 allows extension to 20 kHz while the M200 has no phase plug and the BMS has a mid-range optimized phase plug: http://www.bmsspeakers.com/fileadmin/bms-data/product_data_2014/bms_4599nd_preliminary.pdf

I'm building an old school style big stack of horns system at the moment for medium scale stuff so I have got a bit per-occupied with getting low distortion at high SPL.

I'm planning to do some tests on mine but don't know when I'll get around to it. I'm more concerned with distortion in the lower midrange than the highs. I can't hear much past 16kHz anyway these days, so the HD of anything past 7 or 8kHz are probably of little audible consequence for me. 

The dual diaphragm mid CD's are intriguing for very high output pro apps but require a super tweeter past 8kHz or so. It makes them less useful for synergy or multi entry horn designs. 

8 hours ago, kipman725 said:

 There is a lot of information about the AXI2050 in the horn loudspeakers book, one thing to note though is that although it has a 5" diaphragm the effective surface area of the diaphragm is less than a conventional compression driver (its still obviously huge though).  Another thing to note if using these drivers at high SPL is that distortion performance in the midrange is worse than dedicated midrange drivers like the community M200 (still available), M4 (sadly out of production) and the BMS dual diaphragm mid range. 

Kolbrek's comments about the driver were part of the reason I looked into it. 

Actually that's not quite right. The voice coil diameter is 5" but the diaphragm itself is 7" diameter. The surface area and coil diameter is far greater than the usual 4" cd. Some of the dual diaphragm mids may be close or better it but those also do not cover the full bandwidth. 

Do you have links to detailed distortion measurements for these drivers? I've not seen any. CD's are notoriously difficult to compare as well since the lense used has such a profound effect on the behavior. 

22 hours ago, peniku8 said:

B&C have optimized phase plugs inside their CD's to help with that issue and if you built some into your horn throat it should help. Would probably be too much effort for a single DIY project thou and I have no clue what those would look like.

They all have "optimized" phase plugs. Including the Celestions.

What I mean is that the Axi2050 is supposed to be good compared to most 2" exit cd's in the 10-20kHz octave but the physics mean that while it may be good for a 2" cd it will never be as smooth in this octave as is possible with a smaller diaphragm and smaller exit. Most of the top octave output for large cd's is resonance/ breakup / beaming. Just goes with the territory. There are a lot of positives for the larger cd's though. Higher output, power handling, lower distortion, deeper extension. etc. As usual it's all tradeoffs. 

Also gating can allow for useful measurements of high and mid frequencies in room. 

4 hours ago, Droogne said:

I never had the K402, because they were so goddamn expensive over here in Europe. 

 

For CD I just use a JBL 2447, but I'm definetly gonna replace them. Same for the 12P80Fe. Good drivers I'm sure, but both very heavy (10+ kg each) which limits the portability. Getting the 110x80x60cm cabin down will be extremely difficult to start with, the weight will make it a lot harder to manouver them.

 

However, I would probably go for a BMS4595 (I need a 1.5" throat..). The Radian if I can find a second hand. Maybe make a 1.4 to 1.5" adapter so I can have a wider pick of drivers.

The celestion look pretty cool! A more high end version of the BMS? (or at least when looking at the price  ). 

Gotcha...I thought I saw 402's in some pictures you posted. They are expensive. I bought a used pair and they were not cheap. I got quoted a new pair and it was much more. I hate to think what it would cost to get them landed over in the EU after VAT. Luckily I don't really care about looks for the warehouse system. 

I do like the weight savings of neo drivers. The 2445 JBL "tweeters" are over 30lbs. 

The Axi2050 is different from any of the other cd's out there. It's a relatively newly patented diaphragm shape. Supposedly it gets really wide bandwidth with no crossover and less breakup than normal diaphragm shapes / materials. I've heard that as usual for a 2" exit cd the air above 14 or 15kHz isn't as good as a smaller cd or a Be unit but the midrange is supposed to be very good. Also it has huge surface area and claims to be able to get down to 300Hz. 

What is slightly irritating is I contacted PE about the Axi2050 6 months ago and they said it could not be special ordered from Celestion due to it being OEM only. Now it is on their website for sale. 😒 Oh well...I still paid less for it delivered all of the way from the UK. 

What kind of help are you needing with REW? 

2 hours ago, klipsch said:

Thank you Ricci. Guess I should try to learn akabak and hornresp and such to get a better idea of what I should expect with experimentation.  The tic tac toe pattern just seems easier to attach and remove. Maybe in practice, it is not. I still planned to put the small center circle in front of the dust cap as you've designed it. 

I was thinking of rotating the ckrams on their sides and using them as speaker stands.

Should work just fine. 

So you currently have a single 12P80Fe in each? Did you ever decide on a cd? Also do you still have your K-402's? 

I picked up a set of K-402's last year to replace my JBL 2360's with 2445J's. Ended up deciding on the Axi2050 and picking those up too. I had it narrowed to those vs the Radian 950bePB. I was set to try the Radian but it turned out to be much more expensive and with a longer lead time than the Celestion. Unfortunately I haven't gotten my shit together and made the switch yet. 

12 hours ago, klipsch said:

@Ricci Instead of the "8 point star" design as the throat braces, would a "tic-tac-toe" pattern work as well?   Something very rough like this?

 

 

Sure... there are many ways to skin the cat. I encourage experimentation. 

I went with the star pattern for the simple fact that all 8 "exits" would be identical. It was easier to model in Akabak. Also it doesn't have the center "pocket" in front of the driver center. I thought this might cause turbulence. Does it matter? Probably not. The original front had this type of bracing pattern. 

Don't put anything in the horn/slot section. The front phase of the driver. Sorry I worded that badly.