Originally Posted by more10
The plots do show "box modes", but not in the sense of "room modes" as you would have them if your point of observation is inside the "room" (i.e. cabinet).
Rather the effect of the baffle shape on 0° (= on axis) amplitude frequency response at wavelengths similar in size to the "baffle" dimension is plotted.
And that again is not the same as power response into all angles of the room, but it is also not a consequence of internal modes of the cabinet.
I´ve had these enclosure in my living room for a couple of weeks now.
As some may have noticed in my other thread (musically sub), I´m not satisfied with the low end.
I hoped the E-145 would reach down low in these huge enclosures, but unfortunatelly they have rather lost efficiency in the low end.
My idea would be, to reduce the internal volume from 8ft³ to 5-6ft³ and change the ports from 38hz tuning to aprox. 50hz. This smaller enclosure should gain 2-3db between 50-100hz and give me the punch I´m looking for.
Below 50hz I would use a dedicated sub.
What do you guys think of this idea
I think the only way to reduce the internal volume of this enclosure would be to put some bags filled with pebbles inside...
Before you do all that, why not try Rüdiger's idea and use the speaker you are happy with, but tuned to a higher Qts? If you don't mind the loss a series resistor brings, of course.
You like the midrange this very deep (for JBL) cone offers, and i agree with the advice given by others already that 2220 has a similar midrange quality but would not offer more bass.
The E145 was preceded by the K145. Same deep extended basket -- 100% compatible. That unit is superficially similar, but most E145 had a different (slightly thicker and larger) cone than K145 ex-factory. Your E145 most likely also has that thicker cone kit with the double roll suspension, right?
Now, quite a few K145s were not reconed with their original cone kit as it became obsolete. The E145 kit was used instead.
Most 2nd hand K145 have the common problem of lost energy in their AlNiCo circuit due to mechanical shock, temperature, and just age. That weakness might be your gain. All you need to do is avoid to re-mag such an AlNiCo speaker.
Your E145 will have a Qts close to 0.21, a fully magnetized K145 comes in at 0.23. If you get a second hand K145 with E145 cone kit, it's likely you will see a Qts of 0.4. I have seen K145 with a Qts in excess of 0.5
If a K145 has been re-magged already, use a rubber hammer and softly but not too softly tap the magnet to voice your bass response. The K145 has a design flaw in that the magnet is too shallow for the AlNiCo material used. That makes the magnet very sensitive to loss of energy, and hence allows the hammer procedure described. You would have to hammer a lot harder on the comparatively long magnet of a 2205, 2220 or 2231 ;-) so i don't recommend it
Now here's a free offer: i have two K145's with E145 cone kit for you to try out. They are not interesting as possible purchase, as one is 8, the other 16 ohms. But they would at least allow you to try the idea. If interested let me know, they are only 800km from you so cheap domestic shipping
Ralph
I´ve made the experience, using much thinner cables than usual delivers a "thicker" bass, due to less control through the amp.
Is this the same as your idea?
Which value would you suggest ?
I would try some of the Mundorf 25w cement resistors, or which would you use?
Why doesn´t the series resistor ruin the benefits of a low resistance inductor?
How would I "hide" them? Through them out of the network after testing and using a inductor with bigger resistence instead?You can experiment with big resistors in series, so you see what you have to expect. When your done with your experiment hide the resistors
What would that be?
Less power from the amp because higher resistance?
Or any loss in sound quality?
I understand your idea with the K-145.
But my worry would be, that it is very hard to find two drivers with an identical loss of magnet strength. Different sounding drivers would certainly hurt the soundstage though...
But thanks a lot for your kind offer!
Dang!
Your cabinets are just plain stunning.
Awesome work
Sound quality is more immediate if the coil is wired directly to the amp. Not necessarily always better, but often so. It's what i believe is the reason why active setups sound better than passive ones in many cases.
What i meant though, was the power that goes unused in the resistor. Kind of defeats the high efficiency idea you surely had in mind when starting this endeavour. While going for a lower flux density you have the coil directly coupled to the amp. Still would cost you a full dB in efficiency, i would estimate. But a nicer route than going for a resistor which Rüdiger if believe mainly brought up for a quick sanity check on the general idea.
Another hint as to Rüdiger's comment on a baffle. Recommended for the Smith horn actually was not a baffle as used by Westlake or TAD with the Smith horn. The original note by JBL suggested something only very few people can do (you can!). Namely a bent 5...15 cm high section of wood above and below the 2397. Sometimes such a circular baffle arrangement is sold together with that horn on eBay. Perhaps search Google-Pictures ...
No big problem getting similar magnet strength as i explained. I may sound a bit unconventional but works very well.
Or get some nice frames and start hunting for a pair of E-series cone kits :
http://www.ebay.de/itm/JBL-K145-Vint...IAAOSw-0xYiIpn
Could measure B accurately before putting the coils in instead of going the indirect route (via two times same Qts)
Here's my K145-16 with the E145-16 cone kit (number reads 64194). It has the same cone as yours i believe, just 16-Ohm so cone kit number may differ :
No need to decide now. Shoot me a PM if interested at any time now or later.
Ralph
I compared the data for the E145 with that of other speakers, 275 liters seems more plausible to me than 427 liters. But that is reading COFFEE GROUNDS.
Well defined filters do have a predictable amplitude response, phase response and step response. Known filter families are Butterworth, Bessel, Cauer, Chebyshev, Linkwitz-Riley.
For a certain filter characteristic you need a certain Q. Amplifier and speaker are fixed, cables and inductors are your adjustment screws. This plot shows the amplitude response for an underdamped, overdamped and correctly damped speaker.
Now imagine a speaker with open terminals (not connected to anything), excited by an air blast. The cone will oscillate some small time before it stops. Now short-circuit the terminals (connect them to each other) and excite the speaker again. The cone will stop almost immediately. Now connect the terminals with an 8 Ohm resistor and repeat the experiment. The speaker will stop quickly, but not as fast as when short-circuited.
When the generator resistance is small the speaker will be "tightly controlled". But the amplitude response is overdamped and your bass is gone.
Calculate the value of the required resistor, it should be something like 3.3 Ohms. Buy cheap cement resistors, take care that they don't burn anything. 3.3 Ohms is 3 pieces 10 Ohms each connected in parallel.
This is not meant to be the final solution.
Ruediger
@ Ralph:
If I´d be using K145 with magnet loss I think the sound would be less dynamic, right?
But this is the reason I picked the E145...
Besides that, I think the C8Re145 recone kit is obsolete.
Baffling the 2397 horn would look pretty odd, or I might have a wrong idea about it. Do you actually have a photo of that?
@ Rüdiger:
The graphs illustrate your intention quit well, I kind of understand it.
Its what I´ve had experienced with using much too thin wires "producing" more bass because of less control.
But I don´t understand the overdamped situation yet.
A low genereator resistance and tightly controlled speakers should be a "normal" situation in most cases I thought. So this would represent the natural behaviour of the speaker, not an overdamped.
In my simple understanding, a speaker cannot have to much control e.g. be overdamped, as this would simply be the most natural response I reckon. But every lack of control e.g. underdamping would add more artificial bass.
Don´t get me wrong, I´m not an expert and it´s just a guess.
What would be the final solution without the series resistors?
Thinner wire and a thinner wired series inductor?
I think most here try to make suggestions in response to the midrange transition and bass shyness issues you reported.
Both things you'd like to improve on. If you don't try the suggestions in your setup, you won't know. I mean, even if someone did give you concrete evidence that a suggestion did work in his/her environment, you still wouldn't know if it works in yours.
Fitting a resistor or making up four semicircular "baffles" for your horn from a piece of cardboard would do the trick. And probably take less time than it would for any of us here to produce a reasonably solid report on what such a change did in a system that is, after all, different from yours.
Ralph
I´ve ordered two 3,3ohms 40w cement resistors for testing, but they´ve not arrived yet and I won´t be at home the next week.
I believe baffling the midhorn would look pretty odd, I have no idea how to implement this idea to be good looking...
I will try the "resistor-test" for shure, but I allready have another idea in my mind if this won´t work for me.
Besides my love for the E-145, I think I could be open to a driver change.
Changing to a 10" & 15" combo might do the deal.
I would challenge to "problems"; gaining very low freq. and having a midrange-cone that is better suited for my 1,2khz crossover to the horn. The downside would be a loss in the midbass punch...
I could rebuild my enclosure to house a small subchamber for the 10" midrange. This would be some nasty work, but I have an idea how to do that and maintain the aesthetics.
The driver which come to my mind first are 2235h and 2123h.
The 2123 would work very well with my crossover network with a small change to one inductor.
But I´m looking for a thougher bassdriver than the 2235. The 2235 has 8,5mm xmax but only 11mm xmech, so it has some mechanically risks I don´t like.
Maybe the TAD TL-1603 would be a better choice
When housing a small subchamber for the midrange, my enclosures will still have 7 ft³ internal volume for the bassdriver.
I believe the JBL 2235h works best in 5-6 ft³, but 7 ft³ would be to much!?
Any idea if the TAD TL-1603 will like the 7 ft³ or is it to much as well?
Some previous conversations:
http://www.audioheritage.org/vbullet...42-2397-baffle
My mind drifts to "early great helm" images if the baffles get exaggerated (a bit).
Apart from the effect on Qes, the lossy effect of resistance is max where the impedance curve is lowest. And of course nearly no loss at resonance. That is perhaps where the resistor is most different compared to making the magnet a bit weaker
The baffle is odd, yes. Certainly is not something you'd see every day.
http://www.myaudioshop.com/speakers/...inal-prototype
And of course the larger frontal aspect with baffle might straight away be used for a larger horn that follows the same principles as 2397 (vanes inside, etc) such as the TH-4001.
Anyways, will be interested to see if (and what) the resistors do for you or not.
Ralph
EDIT: post crossed with Grumpy's, there's a similar old Pioneer/TAD picture there. Btw, TL1603 are not a lot cheaper than 1601B's ...
In case I would use a 2235h, what do you guys think about an enclosure bigger than 5 ft³ ?
Does this make any sense?
According to this article:
http://www.lansingheritage.org/html/.../1983-subs.htm
Greg Timbers writes about an 12 ft³ enclosure for the 2245h... Could I assume, that a 6ft³ for the 2235h would be they way to go?
I have built full range systems and dedicated subs using various JBL LF drivers, including the 2235X and 224X series. I saw that old GT article from the 80's back when it was new, and built a several subs based upon the information in it. I built the larger 12cf enclosures for a couple of 2245H drivers with the 30" long ports and used a JBL B63A crossover. I also built several subs using the 2235H drivers. The last one I built was for two 2235H drivers that had 6cf for each driver. It also used a JBL B63A crossover. I used that one as a center channel sub under the front center channel in my upstairs media system. I had several JBL/UREI 6290, Ashly FTX2000III and MFA8000 amps to power the bass and 6260's used on the mid/high frequencies. I was using JBL/UREI and Ashly active crossovers on those systems.
I also tried using a DBX 120X-DS as a crossover for added bass emphasis back when VHS had very compressed and limited VLF. I also tried using a DBX 1BX-DS to "unlimit" and "expand" those same bass limited VHS sources. That type of electronic "enhancement" is certainly not needed now days with the BluRay recordings available. My friends all thought that it sounded great with the old movies of that era. That was a few years ago, but I still have a few of those subs in use today. They have tremendous output capability even in the 30 ~ 20Hz range. Their LF response drops off quickly lower than 20Hz due to physical limitations and a steep 24dB LF filter I inserted into their line level input. I built the dual 2235H sub enclosure to look like a coffee table. It is hard to hide a 12cf sub otherwise. I had built a small dual width rack to sit on top of this sub and placed the center channel speaker on top of that under my flat screen. The center channel speaker was pretty large as it had all the drivers from a pair of JBL L7 speakers incorporated into it. That was the only way I could have a balanced output to match the other L7's and L5's I was using as L&R mains and surrounds at the time. They managed to blend with the combined output of the other speakers and provided the ULF for action movies. I had three JBL PSW-D115 subs placed in other positions around the room to provide a smoother and extended bass.
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