As many of you know already, I have been toying with the idea of adding a tweeter to my P-10 "Castle" microTowers for a little more "air" up top and I appreciate all the input I have recieved on that. I still might do it at some point, but... I have just had a bit of a "eureka" moment and thought that it made more sense to start a new thread.
I just looked at the frequency response graph for the CHR-70c and noticed that it's top end is significantly "hotter" than the rolled off top end of the EL70. It also appears that the form factor of these two drivers is nearly identical except for the shallower "depth" of the CHR.
So, my "big" idea is, replace the two "front" EL70 drivers on my Castle microTowers with CHR-70c drivers, and leave the top EL70 drivers in place.
Stupid?
The biggest challenge (for me) is how to deal with the impedance. EL70 is 4ohms and CHR-70 is 8ohms. Is there an easy way to deal with this (my amp will only go down to 4ohms). Perhaps add something in the chain to make the EL70 8ohms and then wire them parallel to the CHR-70 for a total 4ohm load?
Any other issues that are not obvious to me?
I just looked at the frequency response graph for the CHR-70c and noticed that it's top end is significantly "hotter" than the rolled off top end of the EL70. It also appears that the form factor of these two drivers is nearly identical except for the shallower "depth" of the CHR.
So, my "big" idea is, replace the two "front" EL70 drivers on my Castle microTowers with CHR-70c drivers, and leave the top EL70 drivers in place.
Stupid?
The biggest challenge (for me) is how to deal with the impedance. EL70 is 4ohms and CHR-70 is 8ohms. Is there an easy way to deal with this (my amp will only go down to 4ohms). Perhaps add something in the chain to make the EL70 8ohms and then wire them parallel to the CHR-70 for a total 4ohm load?
Any other issues that are not obvious to me?
Cogitech,
The tonal balance of the two drivers is likely to be different - I have CHR-70.2s and can attest to that they sound different vs EL-70.
The other thing is driver T&S and tuning - CHR-70.3 is different - please note that port length is slightly different for Micro Tower with CHR-70.
I tried mixing CHP-70 (gen 1) and CHR-70.2eN - didn't sound too good in the Lotus^2 cabinet. The timing was kind of off IIRC. Logic was same as your's - bass and midrange richness of paper cone, top end of aluminum cone.
One thing you can do is get the CHR-70.3 and run them in parallel and run one of the drivers as a .5 driver by (capacitor trick - not just 90 degree offset). I am not sure if top driver gives a full .5 driver effect - I rather enjoyed the headroom the top driver provided in my old Micro Tower. It might be noted that I had made it with 15 degree angle, so probably some of the dispersion was forward too. I was actually firing the driver on the front baffle towards the wall. No shortage of treble with the CHR-70 though and it's quite a powerhouse for its size. However I like the EL-70 more.
If you want to increased the liveliness of the EL-70 you can try placing a handful of acosutastuf (dense type) just beneath the drivers - different stuffing material has different effects on sound and I've found that some materials tend to suck midrange/top richness while others can enhance it. Of course, the amount matters too.
The tonal balance of the two drivers is likely to be different - I have CHR-70.2s and can attest to that they sound different vs EL-70.
The other thing is driver T&S and tuning - CHR-70.3 is different - please note that port length is slightly different for Micro Tower with CHR-70.
I tried mixing CHP-70 (gen 1) and CHR-70.2eN - didn't sound too good in the Lotus^2 cabinet. The timing was kind of off IIRC. Logic was same as your's - bass and midrange richness of paper cone, top end of aluminum cone.
One thing you can do is get the CHR-70.3 and run them in parallel and run one of the drivers as a .5 driver by (capacitor trick - not just 90 degree offset). I am not sure if top driver gives a full .5 driver effect - I rather enjoyed the headroom the top driver provided in my old Micro Tower. It might be noted that I had made it with 15 degree angle, so probably some of the dispersion was forward too. I was actually firing the driver on the front baffle towards the wall. No shortage of treble with the CHR-70 though and it's quite a powerhouse for its size. However I like the EL-70 more.
If you want to increased the liveliness of the EL-70 you can try placing a handful of acosutastuf (dense type) just beneath the drivers - different stuffing material has different effects on sound and I've found that some materials tend to suck midrange/top richness while others can enhance it. Of course, the amount matters too.
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Can these differences ever be "complimentary" or is this always a "bad thing"?
I did consider this, however based on my own experience tweaking the ports on my microTowers (which I have not been completely "open" about 😱) I have to simply say that there seems to be (for my needs) considerable flexibility in the tuning of this port, and I can easily do so if I feel that it is necessary.
Hmmm... I am not familiar with the Lotus^2. Is it a "Castle" style with one driver on top? I am thinking the Castle configuration may be rather forgiving, since a slight timing delay is what makes it work the way it does, with much of the signal of the top driver travelling up to the ceiling and then back down to your ears, while the signal from the front driver takes a shorter path (AFAIK).
Well, that is a new idea entirely, which would require changing out all the EL70s for CHR-70.3. Not sure I want to go that far.
Interesting. My microTowers are pretty well stuffed for me as far as bass response goes, but I never considered the impact of stuffing on the treble. Thanks for the tip!
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Whatever you do, make sure you can make the stuffing amount "right" again. IIRC you have a removable bottom, so taking the stuffing in and out should be easier.
Disclaimer: I shall not be held responsible if you manage to screw up the sound. 😀
I have just been doing some more research and it seems easy enough to add a 3.9ohm 10w resistor to the top EL70s and then run them parallel to the CHR70s.
I might just order two CHR-70c drivers and do this as an experiment. Worst case scenario I have a pair of CHR-70c for my next project 😀
I might just order two CHR-70c drivers and do this as an experiment. Worst case scenario I have a pair of CHR-70c for my next project 😀
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LOL
I will be very careful and put any removed stuffing into separate bags for each speaker. Or, perhaps I will just add some acoustistuff behind/below the drivers and leave everthing else in place...
I had a similar idea using el70s front and chp70s top where their rolled off treble might be an advantage?
I don't think the TS differences are different enough to make a huge change in tuning. I've measure the EL70 and CHR70.3's that I have and the Fs are w/i 2 Hz, QTS are very close (.625 / .659), as are Vas 3.7/ 3.2l).
It's an easy enough change to try. I'd just temporaily wire them in series and give it a go.
It's an easy enough change to try. I'd just temporaily wire them in series and give it a go.
I was thinking sort of the same thing, and I have easy, direct access to my ports via removable bottom panels, so if I have to adjust tuning it is a no-brainer.
Hmmmm. And I did just get some Christmas money from my folks... I feel a CSS order in my near future 🙂
what amp again?
almost any SS or even tube amp would have no issue with driving the series wiring load, but a lot might run into problems with the under 3ohms of the parallel load
a notable exception to the latter would be the Decware Zen amp - claimed to be stable @ 1 ohm (certainly was the case with Steve's OEM transformers, I'm not so sure about the latest sans part "kit" version in which a more conventional Edcor is recommended)
almost any SS or even tube amp would have no issue with driving the series wiring load, but a lot might run into problems with the under 3ohms of the parallel load
a notable exception to the latter would be the Decware Zen amp - claimed to be stable @ 1 ohm (certainly was the case with Steve's OEM transformers, I'm not so sure about the latest sans part "kit" version in which a more conventional Edcor is recommended)
Yamaha R-S300 (don't laugh, I think it is actually a pretty good "ampliceiver" based on some of the specifications, such as 0.04% THD @ 8ohm 50w+50w, THD 0.015% @ 25W, and a frequency response of 10Hz to 100kHz in "Pure Direct" mode). It sure sounds pretty damned fine to me, anyway 😀
In the manual it describes the use of the impedance selector switch, and states:
Switch Position "HIGH" - "If you use one set of speakers (A or B) the impedance of each speaker must be 8ohms or higher."
I guess a 12 ohm load would be fine, then.
I figured a parallel impedance of 2.6 ohms would be an issue, which is why I thought I might add a resistor to the EL70 to bring it up to 8 ohms and then run it parallel to the 8 ohm CHR70 for an impedance of 4 ohms (which the amp can handle when the impedance selector is set to "LOW".
However, in the specs of the amp, I see the following:
Dynamic power per channel (IHF) (8/6/4/2 ohm) --- 70/77/89/100
It seems odd to list a DPPC spec for 2 ohms. They must have tested it at 2 ohms to get this figure. But why tempt fate, right?
But what I should really be asking is; if I run a 4 ohm driver in series with an 8 ohm driver, will the output of the 4 ohm driver be 2x that of the 8 ohm driver, or will they simply work as a combined 12 ohm driver with (approximately) equal output? (overlooking minor sensitivity differences)
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if you had the drivers on hand I'd be tempted to say just install and listen- (I'd definitely not gamble on the parallel connection unless you're very confident on the amp's low impedance stability
The more I listen to different kinds of music, the more I realize that the default laid-back highs of the EL70s can be enhanced quite easily with EQ/treble-knob, and in most cases I don't even want "hot" highs.
However, I am very curious about how the CHR-70.3 would integrate, so at some point in the New Year I might just go ahead and order a pair and start playing with this idea.
Best case scenario; I love the results and I end up with a spare pair of EL70 for my next project. 😀
Worst case scenario; I don't like the results and I end up with a spare pair of CHR-70.3 for my next project 🙂
Talk about a "win - win" situation...
Thanks to all who have commented and offered help. I'll return to this thread in the New Year some time. In the meantime, my EL70s are doing a fabulous job with all the Christmas tunes at my house.
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How did you know I have my eye on FH3? 🙂
Well, one eye anyway. The other eye is on something completely different. I might actually take the time to learn Martin King's worksheets and design a new TL...
Just guessing. 😉
I just happen to have two pairs of EL70s, one pair of CHR70.3's, one pair of ERT26 and two sheets of 5x5 5/8 BB in the shop (and too many other drivers in the Fortress of Solitude). Any way I was actually wondering the very same as you (EL70/CHR70) since I planned on the Microtowers. The current plan is Microtowers, FH3, and Arro style MLTL (w/ ERT26) with driver swapping. If I like them all as much as I suspect, I'll be buying more of something.
I just happen to have two pairs of EL70s, one pair of CHR70.3's, one pair of ERT26 and two sheets of 5x5 5/8 BB in the shop (and too many other drivers in the Fortress of Solitude). Any way I was actually wondering the very same as you (EL70/CHR70) since I planned on the Microtowers. The current plan is Microtowers, FH3, and Arro style MLTL (w/ ERT26) with driver swapping. If I like them all as much as I suspect, I'll be buying more of something.
Exactly my thought. Too bad I live so far from you Planet 10 guys, I think I'd stand you to a beer or such.
Wow! That is a whole shed-load of fun awaiting you!
Good luck with all of those projects!
Yes. Fortunately winter in Texas does not prohibit building in the shop/garage. Finishing conditions are irregular, but building proceeds.
I'm particularly interested in how the combination of the EL70s and ERT26 with a first order XO sound. I'm hoping that it will add just that little bit of sparkle and harmonic that the EL70 could use at the high end.
I'm also suspecting that the ERT26 may be s secret weapon inexpensive tweeter for a conventional 2/3 way.
I'm particularly interested in how the combination of the EL70s and ERT26 with a first order XO sound. I'm hoping that it will add just that little bit of sparkle and harmonic that the EL70 could use at the high end.
I'm also suspecting that the ERT26 may be s secret weapon inexpensive tweeter for a conventional 2/3 way.
Wow! That is a whole shed-load of fun awaiting you!
Good luck with all of those projects!
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