I have a similar idea in mind, so far I bought a pair of FE87E, mounted in a small enclosure, sounds better than most satellite. I think I should be able to cross around 100-200Hz to a woofer housed in a separate enclosure. I think it would be closer to 200Hz.
HareBrained said:
really? 4L sealed at 80Hz crossover for the CHR-70? From henkjan's comments and the simple calcs I've run, it looks like a sealed 4L CHR-70 should be crossed at 100Hz (maybe even 120Hz). Also, I think incremental power handling of the CHR-70 is largely offset by the incremental reduction in efficiency (according to the specs, 15w vs 22w continuous and 85 vs 86db... the '5' is the 6w driver). The CHR-70 is certainly more versatile than the '6', but the '6' seems perfect for a small ported box (at the expense of... well... expense).
the 4 liters sealed I used is WITH the use of a high pass cap, which will lower the f3. I will put the sims of this here later (don't have them on this PC) to show the effect of the cap. it does not only act as a high pass (an electical engineer will be able to explain this properly).
the X-over of 100 or 120Hz I mentioned was taking into account that if the X-over is done from a HT receiver, you'll want to cross well above the f3 of the sat otherwise the filter curves will be asymetrical. in case you only put a LP on the sub, you can match that to the f3 of the sat, so a lot lower
the X-over of 100 or 120Hz I mentioned was taking into account that if the X-over is done from a HT receiver, you'll want to cross well above the f3 of the sat otherwise the filter curves will be asymetrical. in case you only put a LP on the sub, you can match that to the f3 of the sat, so a lot lower
I really need to learn more about crossovers 😕 my sims look like planet10's... which may work fine with 4L sealed at f3 of 80Hz, if I can run them full range and put a low-pass on the sub at 12db/oct 80Hz (I think my HT receiver will allow this)... otherwise, the alpair 6 reaches a bit lower in a ported enclosure of the same volume and it should allow me to use the HT crossover with reasonable success. I think I understand the likely tradeoffs here now for a compact sat with 80Hz xover... 4L sealed with the CHR-70 should be no problem, 3L is possible, but a bit trickier with the xover due to the cap (2L even more so)... ported alpair 6 is a pricier, but seemingly simpler 3L option (from a xover perspective).
Henkjan said:
can you try to explain what is going on here? I am at a loss without more details... the sim looks good, but is contrary to my (admittedly minimal) understanding of what a series cap does. The size you chose (680uF) is well below the 80Hz crossover mentioned... in selecting this capacitance, you appear to be further attenuating an already attenuated signal to get a bump at a slightly higher frequency. Given the bass bump smaller enclosures give without filtering, I'm surprised your plots show no bump at all. Was the value selected to push the low end up and match the baffle step? A layman's explanation would be nice, and pointing somewhere for more reading would be even better 🙂 Thanks!
maybe someone with a decent education in EE can explain what is really happening.... what stayed in my head is that there is an interaction between the voice coil and the cap, which leads to a lower impedance below the resonance which in turn leads to a higher output there, in addition to flattening the bump of the qb=1.0 enclosure.. applying this to a box with qb<1 will lead to a bass that extends lower but at cost of some spl in the low end (this is what I did with the Black Beauty, f3 is about the same, but f6 is significantly lower)
This was (to me at least) introduced by the german magazine Hoby Hifi, and they also gave a formula to calculate the right value of the cap. the owner of this site http://www.12vhifi.nl/closed.html made a nice javascript calculator for it, so that is what I use. so don't use formula's for a normal high pass filter...
This was (to me at least) introduced by the german magazine Hoby Hifi, and they also gave a formula to calculate the right value of the cap. the owner of this site http://www.12vhifi.nl/closed.html made a nice javascript calculator for it, so that is what I use. so don't use formula's for a normal high pass filter...
ok... maybe not the best source, but clears up some of what you are saying:
http://sound.westhost.com/lr-passive.htm#s3.1
the javascript in the website you provided approximates what a good value should be, but really needs to be validated/adjusted with measurements. apparently there are some concerns with the long-term stability of bipolar caps, and even if that is not a concern, spending roughly $10-12 USD on a large bipolar cap eliminates the value proposition of the CHR-70 vs the Alpair 6. At equal cost for the total solution, the A6 without the need for the capacitor might be the better sounding system at 3L, no? I've heard neither, so I'm looking for opinions here, not trying to be argumentative. Thanks!
http://sound.westhost.com/lr-passive.htm#s3.1
the javascript in the website you provided approximates what a good value should be, but really needs to be validated/adjusted with measurements. apparently there are some concerns with the long-term stability of bipolar caps, and even if that is not a concern, spending roughly $10-12 USD on a large bipolar cap eliminates the value proposition of the CHR-70 vs the Alpair 6. At equal cost for the total solution, the A6 without the need for the capacitor might be the better sounding system at 3L, no? I've heard neither, so I'm looking for opinions here, not trying to be argumentative. Thanks!
OK... got some 4 chr-70s at a price I couldn't refuse. I've decided my infatuation with tiny speakers is ridiculous, and that I'd rather have easy to build speakers that sound really good. anyway...
So, my intended use is for combined music and HT in a medium sized room (12ft on listening axis by 25ft, 8ft ceilings). I like the looks and simplicity of a 4L sealed, but am concerned with excursion in a HT setup. I'm seeing xmax at about 11W when run full range, but that is at ~95dB. Does this sound right?
I guess I am asking if I do not want to wake up the neighbors, is there any really chance that I would get to xmax? I have a HT receiver with decent xover/bass mgmnt, and a separate crossover on the sub amp, I think tehre are a few options, but I'm not sure which I am likely to get the best integration with. Speakers will be close to the wall, and the sub is a cheap pio 10" HTIB type with a pot for xover control. receiver is HK247. Also, if replacing the sub is the best option with a xover for the purpose, please advise on that as well. Thanks!
So, my intended use is for combined music and HT in a medium sized room (12ft on listening axis by 25ft, 8ft ceilings). I like the looks and simplicity of a 4L sealed, but am concerned with excursion in a HT setup. I'm seeing xmax at about 11W when run full range, but that is at ~95dB. Does this sound right?
I guess I am asking if I do not want to wake up the neighbors, is there any really chance that I would get to xmax? I have a HT receiver with decent xover/bass mgmnt, and a separate crossover on the sub amp, I think tehre are a few options, but I'm not sure which I am likely to get the best integration with. Speakers will be close to the wall, and the sub is a cheap pio 10" HTIB type with a pot for xover control. receiver is HK247. Also, if replacing the sub is the best option with a xover for the purpose, please advise on that as well. Thanks!
Enjoy building out your system! I am surprised no one mentioned TB speakers? They make great 3" drivers that sound really nice in small sealed boxes. I love Fostex and never heard the Alpairs (they do look nice)... but the TBs are great for smaller applications and sound really good.
Godzilla
Godzilla
You picked up a quad of CHR70s - how exactly to you intend to run them?
Remember they are (nominally) 4 ohms impedance, with 85dB sensitivity; like many lower price ranged HT receivers, the HK 247 is rated at 8 ohms. This could cause some issues when operating at the current levels the CHR70s would want to draw at higher SPLs - indeed your receiver might well run into grief before the drivers X-maxed out, even with careful tuning of the bass management.
If you're planning on using 2 CHR (or EL)70's per enclosure, I'd definitely suggest wiring in series, rather than parallel. At a recent VI DIY get together, we heard Bob Reimer's dual EL70 in 3/4 cu ft PE enclosure, as well as 2 pairs of the Planet10 bi-pole microtowers - all were wired in series, which was a very comfortable load for all the amps at hand.
For a HT rig with these drivers, I'd be inclined to think towards multiple woofers (i.e at least 2), XO as high as 120-150HZ. Set the receiver to run the L&R mains as large, and use the woofer amp's speaker level inputs and passive HP filter to the CHR's. The stereo woofers needn't be killer 18" HT subs, but of course you could certainly add that as well.
Was hoping to avoid stereo subs if possible (prefer 80hz cross to sub, but 100hz is likely ok in my room). Not opposed to 2-per cabinet for the mains and center... are 4-ohm rear channels likely to cause a problem? What are the indicators of amp strain? (prior to smoke, that is) 😉
My experience with multi-channel (i.e. more than 2), amplifiers is limited to a single model of Denon AVR1600 or some such, in a long since abandoned attempt to get the whole HT thing working. So I could be talking out of my a$$ (certainly wouldn't be the first time for that), but I've always been told to avoid going under the manufacturers' rated loudspeaker impedance specs when using all 5 or plus on board channels. There is generally a single common power supply stage which can be overtaxed by the high current draw of multiple low impedance speaker loads, particularly if they are of only moderate sensitivity.
In the best case scenario, you could probably expect compressed dynamics, increased levels of noticeable clipping distortion, and hopefully nothing more than blown main AC fuse. I'd guess the "worser" cases would depend on the sophistication of the amplifier's protection circuitry, and blind luck, but there is a lot of smoke in both the amp and voice coils of even a 4" full range driver.
Honestly, I don't want to be alarmist - you might not encounter any problems at all, but having once worked as a paper pusher in an audio shop warranty repair shop, I would never bet against Dr Murphy making a visit.
As for stereo "subs", I'll opine somewhat pedantically for a moment - at frequencies as high as 100-120Hz, I'd prefer to classify them as woofers. Regardless of the semantics, there has been some very interesting information recently by Earl Geddes, and others, as to the efficacy of multiple (small) woofers
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interesting tidbit from the FAQs on the HK website... it looks like it should be fairly obvious if the load is too much (enters standby mode), and would assume it keeps track somewhere in persistent storage of how many times it does this:
Question: Can my surround-sound receiver handle a 4-ohm load?
Answer: All Harman Kardon Audio/Video receivers can handle most 4 and 6 ohm speakers on the market today. However, there are some manufacturers' speakers that have a minimum impedance well below the 4 and 6 ohm nominal impedance. In this situation, the receiver will protect itself by going into standby mode. This will not damage the speakers or the electronics, but it is an indication that the speaker in question is not compatible with our receiver. Note: The continued use of the receiver with speakers that cause it to shut down can result in eventual failure of the receiver which is not covered by the warranty.
Answer: All Harman Kardon Audio/Video receivers can handle most 4 and 6 ohm speakers on the market today. However, there are some manufacturers' speakers that have a minimum impedance well below the 4 and 6 ohm nominal impedance. In this situation, the receiver will protect itself by going into standby mode. This will not damage the speakers or the electronics, but it is an indication that the speaker in question is not compatible with our receiver. Note: The continued use of the receiver with speakers that cause it to shut down can result in eventual failure of the receiver which is not covered by the warranty.
Anyone know the minimum impedance for the CHR-70s (specs say 4ohm minimum between 100Hz and 1K)... does this hold true in practice (for a small sealed enclosure if that matters)???
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without... if the sims are on, I should get close to 95dB running full range without it, which I think should be plenty for my room and listening levels. If the sims are off, I'll need to look at xover options. No problems with excursion with an appropriate crossover, obviously, but I'm of the mindset to keep it simple until I need otherwise. Should be fairly obvious with a little meter if I think 95dB is enough for my listening... if not, time order the xover bits.
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