| audiobomber |
I'm likely going to build the 8L JX92 monitors shown on the Jordan site. I see there's a circuit suggested for frequency compensation. I assume this is BSC?
I'm not crazy about putting a resistor and inductor in series with the woofer. Can this circuit be implemented at line level instead?
Dan |
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| Dave Jones |
| quote: | Originally posted by audiobomber
I'm likely going to build the 8L JX92 monitors shown on the Jordan site. I see there's a circuit suggested for frequency compensation. I assume this is BSC?
I'm not crazy about putting a resistor and inductor in series with the woofer. Can this circuit be implemented at line level instead?
Dan |
I have just built a pair of Jx92S monitors in sealed 8 liter boxes. The speakers are near a wall. The recommended BSC with the 4 Ohm resistor is too much. It sounds best with 1 Ohm, but quite acceptable with no BSC at all.
Why are you not crazy? :-) Don't worry that the passive filter will degrade the sound. |
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| audiobomber |
| quote: | Originally posted by Dave Jones
I have just built a pair of Jx92S monitors in sealed 8 liter boxes. |
Cool, how do you like them?
| quote: | Originally posted by Dave Jones
Why are you not crazy? :-) Don't worry that the passive filter will degrade the sound. |
Having just gone from a passive to an active crossover in my main system, I have fresh experience of what an inductor does to the sound. And a resistor is going to eat up the amp's damping factor. If I can implement a BSC circuit between the amp and preamp, I'm sure it will sound better.
OTOH, like you said, maybe I don't need frequency compensation at all. |
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| Dave Jones |
| quote: | Originally posted by audiobomber
Cool, how do you like them?
Having just gone from a passive to an active crossover in my main system, I have fresh experience of what an inductor does to the sound. And a resistor is going to eat up the amp's damping factor. If I can implement a BSC circuit between the amp and preamp, I'm sure it will sound better.
OTOH, like you said, maybe I don't need frequency compensation at all. |
What do you mean "what an inductor does to the sound"? It does what it's supposed to do. Doesn't it?
Concerning damping factor, remember that the inductor effectively takes the resistor out of the circuit at frequencies where the impedance is very high. Again, I wouldn't worry about it.
I reiterate, when the speakers are near a wall, it sounds best (to me) with a 1 Ohm resistor in parallel with the 1.5mH inductor - better than without the BSC circuit. Your ears may vary.
I skipped a question. How do I like them? Let's put it this way: I slept with them last night, and I still respected them this morning. |
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| Stocker |
| an inductor in the line level signal in an active preamp will have different effect than a similar value inductor in line to a speaker. |
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| Josephjcole |
| quote: | Originally posted by audiobomber
I'm likely going to build the 8L JX92 monitors shown on the Jordan site. I see there's a circuit suggested for frequency compensation. I assume this is BSC?
I'm not crazy about putting a resistor and inductor in series with the woofer. Can this circuit be implemented at line level instead?
Dan |
If you look halfway into this post there is message explaining a BSC ciruit done line level for a fostex 167.
Joe
this post |
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| audiobomber |
| quote: | Originally posted by Dave Jones
What do you mean "what an inductor does to the sound"? |
An inductor is a filter. It resists AC voltage changes. This causes the bass to sound fatter and slower and less dynamic.
Concerning damping factor, remember that the inductor effectively takes the resistor out of the circuit at frequencies where the impedance is very high.
The problem of decreased damping factor worsens as frequency decreases (woofer motion increases at lower frequencies, more momentum is harder to stop when signal stops.)
I reiterate, when the speakers are near a wall, it sounds best (to me) with a 1 Ohm resistor in parallel with the 1.5mH inductor - better than without the BSC circuit.
I don't doubt that. I still think a line-level BSC is a better way to go.
I slept with them last night, and I still respected them this morning.
:D |
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| audiobomber |
| quote: | Originally posted by Josephjcole
If you look halfway into this post there is message explaining a BSC ciruit done line level for a fostex 167.
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That's a good start, thanks Joe. Too bad they didn't give a formula. |
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| planet10 |
An active BSC circuit
http://www.t-linespeakers.org/tech/...bstepcompo.html
and a clipping from Paul Joppa (posted a couple places -- this is from the Full Range Forum)
| quote: | Line level equalizer for baffle step (long)
[ Full-Range Driver Forum ]
Written by Paul Joppa at 20 Apr 2004 22:52:44:
A little while ago, Jon Ver Halen asked me to look into a line level equalizer that would provide the same equalization as the popular LR and LCR speaker level filters that are often used for single-driver speakers. Bass reflex and to some extent TQWT designs seem to be especially common applications. This started as a commercial project, but it turned out to be so simple that I thought it would be better to just put it in the public domain. Here is the result:
In the midband the gain is reduced to R2/R1+R2, and is -6dB when R1 = R2. C2 provides the low frequency boost by restoring the gain to unity at the lowest frequencies. C1 is optional, and provides some treble boost (restores the gain to unity at the highest frequencies).
The LF time constants are R2*C2 and (R1+R2)*C2. The HF time constants are R1*C1 and (R1 || R2)*C1, where R1 || R2 means R1 in parallel with R2. Frequency is 1/(2*pi*time constant).
To make the calculations simpler, I assumed that the source impedance (Rsource) is much lower than R1 or R2, the load impedance (Rload) is much higher than R1 or R2, and the capacitance of the load (Cload) is much smaller than C1, which is itself much smaller than C2.
In practice, as long as Rsource is less than half of R1 || R2, and Rload is more than twice R1 + R2, the response will be within a dB of the predicted values. The greatest practical difficulty is with Cload. It must be less than 10% of C1 in order for it to affect the performance by less than 1dB. Most of its effect is above the HF corner frequencies, so it might be reasonable to use a Cload as high as 20% of C1. If C1 is not used, then the only limitation is the (R1 || R2)*Cload time constant, which will cause a treble rolloff.
As an example, I determined parameters for two implementations (one active, one passive) to match Martin King's revised speaker level circuit, shown at:
http://www.quarter-wave.com/Project04/Project04.html
His speaker-level circuit has approximately 5.2dB midband cut, with low frequency corners at 220 and 400Hz and high frequency corners at 10kHz and 18kHz.
The active implementation assumes a tube gain stage to make up the 5dB loss, and a direct-coupled cathode follower so that Cload is very small and Rload is essentially infinite. Here are the values:
Rsource = 15k
R1 = 220k
C1 = 68pF
R2 = 270k
C2 = 0.0015uF
Cload = 10pF
I compared this using the PSpice circuit simulation program to a model of King's circuit, assuming a constant 8 ohm speaker impedance (roughly what he measured, above 200Hz). The match is good, except this circuit is 1dB down at 20kHz due to the 10pF input capacitance of the cathode follower.
For a passive implementation between preamp and power amp, the Cload would be larger. Most tube amps have around 100pF input capacitance, and the cable will have more. A frequently used number is 1000pF for long cables, but with short cables of 3 feet or less, a Cload of 200pF might be achievable. Then you could use the following values:
Rsource < 2k ohm
R1 = 10k
C1 = 1500pF
R2 = 12k
C2 = 0.033uF
Rload > 50k
Cload = 200pF
A minimum load of 12k is presented to the source, which is on the low side but achievable with most gear; in the midband the load is 22k.
For experimenters, a useful modification would be make R1 a variable resistance, or replace both R1 and R2 with a linear taper potentiometer. This way the magnitude of the boost can be adjusted, to compensate for room acoustics for instance.
I hope this is useful to the community.
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dave |
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| audiobomber |
That's the ticket! Thanks Dave.
And a big thank you to Paul for his generosity.
Dan |
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| audiobomber |
| quote: | Originally posted by Dave Jones
Concerning damping factor, remember that the inductor effectively takes the resistor out of the circuit at frequencies where the impedance is very high. |
Sorry, just ignore what I said about this in my other response. I was misreading what you said.
I agree the resistor is taken out of the circuit at low frequencies, but it will still compromise the amp's control of the mid and high frequencies, and it will waste power (lower efficiency). A line-level circuit won't.
I've been playing around with the components in my speaker crossovers a lot, and anything I've inserted between a driver and the power amp is a compromise. Between the amp and preamp, if it's done right, is much less intrusive. |
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| DIAR |
| I prefer my GM MLTL without any BSC. I tried resistor (various) and choke (1,5 mH) combo but it killed the sound. Adding a good quality (4,7 uF) capacitor parallel with resistor and choke helped much but not enough. |
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| MJK |
| quote: | | An inductor is a filter. It resists AC voltage changes. This causes the bass to sound fatter and slower and less dynamic. |
| quote: | | The problem of decreased damping factor worsens as frequency decreases (woofer motion increases at lower frequencies, more momentum is harder to stop when signal stops.) |
A couple of comments on the statements above :
1. Lets assume that the baffle step for a reasonably sized cabinet occurs at 400 Hz. Depending on the actual width of the enclosure this frequency might be slightly higher or lower, but this frequency is a reasonable starting place for discussion.
2. The inductor in the BSC circuit is sized to become active at 400 Hz and then a resistor is placed in parallel to pad down the mid range and high end, above this frequency, the desired dB amount to rebalance the SPL response.
3. Below 100 Hz all of the signal passes throught the inductor, it is equivalent to an additional length of speaker cable and contributes only a small additional DC resistance. Considering the high impedance of the driver/enclosure system below 100 Hz, it should be obvious that the inductor has no impact on the bass performance. The driver output and motion is not changed for a given input signal, turning up the volume will obviously increase the driver motion.
4. Above 400 Hz, the impedance of the inductor is rising and all of the signal transitions to pass through the parallel resistor. The SPL of the driver is shelved down to be consistent with the bass output from the driver/enclosure system. In fact, adding a BSC circuit corrects a local phase shift that arises due to the baffle step phenominon.
Conclusion :
A BSC circuit should have no effect on a speakers bass performance or an amps damping factor unless it has been incorrectly sized and implemented. If for arguements sake, we assume that there is some small degradation to the signal from the BSC circuit my experience is that the improvements in overall system SPL performance are so large that this assumed degradation is not significant. If your BSC is resulting in a "fatter and slower and less dynamic" performance the problem is in the midrange response, not the bass response, which would lead me to believe that the parallel resistor value is too large.
Hope that helps, |
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| audiobomber |
| quote: | Originally posted by MJK
3. Below 100 Hz all of the signal passes throught the inductor, it is equivalent to an additional length of speaker cable and contributes only a small additional DC resistance.
4. Above 400 Hz, the impedance of the inductor is rising and all of the signal transitions to pass through the parallel resistor. |
I agree with you on everything you said Martin, with an exception. IME an inductor has more effect on the sound than its small DCR would indicate. I have heard my speakers with an inductor in the circuit and without (replaced by an active cct in front of the amp) and there is an easily noticeable difference in speed, detail and dynamics, all in favour of the active circuit. Same goes for the resistor on my tweeter. It noticeably degrades performance vs a line-level XO.
| quote: | Originally posted by MJK
If your BSC is resulting in a "fatter and slower and less dynamic" performance the problem is in the midrange response, not the bass response, which would lead me to believe that the parallel resistor value is too large. |
My comments on the effects of an inductor and resistor between the amp and the driver are based on my experiences with an active vs. a passive crossover, not on a BSC cct. Nevertheless, I firmly believe that speaker-level components (caps, resistors, inductors) are not as transparent as line-level components. And this was apparent even when I used top quality parts in the passive crossover.
I certainly don't doubt your statement that BSC benefits outweigh the losses. All I'm saying, is that a line-level beats a speaker-level circuit for sound quality and efficiency.
Dan |
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| MJK |
| A crossover and a BSC are two completely different animals with totally different functions. In my variable BSC design, I can completely remove the circuit from the system and then gradually bring it back with the twist of a dial. Powered by a SS amp, I do not hear any degradation in the sound or the transient performance of the speaker driver. The only thing heard is the gradual rebalancing of the SPL response resulting in a significant performance improvement. This is true of the Lowther drivers I use which I believe would quickly reveal any sonic degradation resulting from the BSC circuit. |
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| morbo |
MJK, sorry for the slight veer off-topic, but when you say:
| quote: | | A crossover and a BSC are two completely different animals with totally different functions. In my variable BSC design, I can completely remove the circuit from the system and then gradually bring it back with the twist of a dial. |
what about when you crossover right at the BSC frequency at a slope close to the BS drop off rate? Is this what you mean by your variable BSC design? I am very interested in how yoy accomplish what you describe with dial. |
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| MJK |
| quote: | | what about when you crossover right at the BSC frequency at a slope close to the BS drop off rate? Is this what you mean by your variable BSC design? I am very interested in how yoy accomplish what you describe with dial. |
All of my recent speaker designs are single driver full range enclosures. If you look under the General Speaker Related Articles link on my site you will find the documentation for the variable BSC I use with my Lowther ML TL speakers.
I used a BSC on my two way Focal TL, it was placed ahead of the crossover as an add on fix after the fact. Probably not an optimal design but it worked out very well in that particular situation. You can find that schematic under my Project #1. |
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| audiobomber |
| quote: | Originally posted by MJK
A crossover and a BSC are two completely different animals with totally different functions. . |
They're different, but they're similar too.
- they're both filters
- they both insert an inductor between the amp and LF driver
- they both insert a resistor between the amp and the mid/high frequency driver
Where we disagree is on the effect of the latter two points. |
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| MJK |
| quote: | | Where we disagree is on the effect of the latter two points |
I agree, we disagree. No point in continuing the discussion. |
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| soongsc |
| I think some degradation using different components might cause sound degradation. Designs based on ideal components should be good regardless what names you give it. I have found that foil inductors preserve the liveness of music. This I think was because the phase is preserved throughout the long wiring of the inductor. |
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| salas |
Wire is wire and not a little symbol on our schematics.
Imagine how many metres of magnet wire we use in a 1.5 mH when we make such a fuss for maybe 2 metres of speaker wire.
But I prefer the correct balance of tone and accept the little veil of the coil. Regarding great coils I have used Alphacore too and yes they are very good. We just must be sure we are final with design and then splash out on Alphacores and Mundorfs. Such components go a longway towards making coils and caps those innocent symbols on paper as they should be... They must be doing their corrections without shouting I am here!
Guys I must also let you know I have some cryoed copper foil speaker cable now in my system and I think that is the way to go...wish they will make some coil like that in some earthy price. |
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| planet10 |
| quote: | Originally posted by salas
Guys I must also let you know I have some cryoed copper foil speaker cable now in my system and I think that is the way to go...wish they will make some coil like that in some earthy price. |
You could just make a coil and send it to someone like PEARl for cryo teatment. There is also one in Oz -- there is a link off Joe Rassmessen's new domain.
dave |
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| Dave Jones |
If I might be allowed to return to reality for a minute...
I've got a pair of new JX92S's in 8 liter sealed boxes. They are placed a few inches from the back wall, which puts the the baffle about a foot from the wall. One of the speakers is very close to a corner. The coil is 1.5mH. I started with a 4ohm resistor, as recommended on the Jordan web site. The result was a very muffled sound. Not too surprising I guess, considering the placement. Omiting the BSC entirely was not perfect either. Edgy. After a number of iterations, I've converged on 1 2/3 ohms (2 ohms in parallel with 10 ohms). I think I could go a tad lower. I've ordered some non-inductive 1.5ohm resistors from PE, which I think will do just fine. But I ordered pairs of 2.0 and 1.2 for good measure. |
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| soongsc |
| I think salas is right. Perhaps the first thing to try is to get an AlphaCore foil inductor. This is probably the most reasonable approach from an engineering point of view. Which if done on such basis, you will save yourself lots of trouble and $$$ in the long run. |
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| Dave Jones |
| What is the advantage of a foil inductor over wire? |
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| soongsc |
This is related to the skin effects of signal at different frequencies. If you have the thickness of the foil about or less than the thickness of the high frequency skin depth, and use foil width to achieve the necessary cross section area, then you will minimize phase shifts throughout the audible range.
This site has some accurate description of wire relate issues.
http://www.st-andrews.ac.uk/~www_pa...fect/page1.html
Since the inductor has the most wire length in normal home applications, then that is where we normally should take care of first. |
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| Colin |
| quote: | Originally posted by Dave Jones
If I might be allowed to return to reality for a minute...
Omiting the BSC entirely was not perfect either. Edgy. |
Hi Dave
Are you listening off-axis, with the drivers toed in 30 degrees, to cross well in front of the listening position? I've found getting well back from the crossed axis of the drivers helps tame the HF.
Having said that, I'm running the JX92S full range and the extra body in the bass seems to balance out the treble, so the above may not apply in your case.
FWIW, I've heard a single JX92S in the 8 litre reflex which Ted suggests on his site, that seemed to balance out ok using his recommended BSC circuit. Nothing like a little practical experiment, though. Be interested to hear how you get on. |
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| soongsc |
Dave,
Have you also check signal polarity throughout your system? Some amplifiers and players might invert the signal without telling you. Swapping at the speaker will help you identify which is right. |
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| audiobomber |
| quote: | Originally posted by salas
We just must be sure we are final with design and then splash out on Alphacores and Mundorfs. |
I had a lot of success with Solen Hepta-Litz inductors. I definitely preferred the Hepta-Litz to Alpha-core in my XO. Plus the Hepta-Litz DCR is closer to plain wire inductors than foil inductors, which can be important if you're substituting/upgrading from a normal air-core. |
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| planet10 |
| quote: | Originally posted by soongsc
Have you also check signal polarity throughout your system? Some amplifiers and players might invert the signal without telling you. Swapping at the speaker will help you identify which is right. |
All this concern about inverting & non-inverting has me baffled... given that the abs phase of the software is essentially random (if any attention was paid in the 1st place) there is no right way. A switch is required so that the abs phase can be checked for each track (if you are lucky an album will be consistent from track-to-track)
dave |
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| soongsc |
| quote: | Originally posted by audiobomber
I had a lot of success with Solen Hepta-Litz inductors. I definitely preferred the Hepta-Litz to Alpha-core in my XO. Plus the Hepta-Litz DCR is closer to plain wire inductors than foil inductors, which can be important if you're substituting/upgrading from a normal air-core. |
Yes, I have though about Litz wiring too! What guage size wiring do these inductors have? Are they smaller than the AlphaCore's? |
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| soongsc |
| quote: | Originally posted by planet10
All this concern about inverting & non-inverting has me baffled... given that the abs phase of the software is essentially random (if any attention was paid in the 1st place) there is no right way. A switch is required so that the abs phase can be checked for each track (if you are lucky an album will be consistent from track-to-track)
dave |
In software, the polarity is determined by the sign bit of a word. Software designers don't change it unless specifically required. So whatever is sampled through the A/D is used. For hardware designers, generally designers feel the signal is a sine wave and polarity has no significance, so phase inverting designs might imerge to reduce part count.
If you can hear the difference, then check polarity, if not, there might be some other disortions in the system that mask the polarity effects. |
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| planet10 |
| quote: | Originally posted by soongsc
In software, the polarity is determined by the sign bit of a word. Software designers don't change it unless specifically required. So whatever is sampled through the A/D is used. |
That assumes the mix is digitized... much of the software we get -- often the best stuff included -- never gets digitized (ie LP), and if it does, just before it gets made into a CD/SACD/DVD-A. The stuff that gets digitized usually goes thru at least an analog mic pre-amp and could be either in or out of absolute phase.
dave |
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| soongsc |
| quote: | Originally posted by planet10
That assumes the mix is digitized... much of the software we get -- often the best stuff included -- never gets digitized (ie LP), and if it does, just before it gets made into a CD/SACD/DVD-A. The stuff that gets digitized usually goes thru at least an analog mic pre-amp and could be either in or out of absolute phase.
dave |
I guess you're right in this aspect, but normally if the phases are mixed up, the total mixed recording would sound weird as in most pop music with complicated instrumentation. I guess we just need to select what is used as a reference. I normally like Reference Recordings, other good recordings are in quantities these days. |
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| audiobomber |
| quote: | Originally posted by soongsc
Yes, I have though about Litz wiring too! What guage size wiring do these inductors have? Are they smaller than the AlphaCore's? |
They come in 16ga (7 x 26 AWG), to 10ga (7 x 20 AWG) sizes. www.solen.ca |
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| soongsc |
| quote: | Originally posted by audiobomber
I had a lot of success with Solen Hepta-Litz inductors. I definitely preferred the Hepta-Litz to Alpha-core in my XO. Plus the Hepta-Litz DCR is closer to plain wire inductors than foil inductors, which can be important if you're substituting/upgrading from a normal air-core. |
Have you compared both the Hepta-Litz and the Alpha-core against each other? How different do they sound? (assuming DCR is corrected for) |
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| audiobomber |
| quote: | Originally posted by soongsc
Have you compared both the Hepta-Litz and the Alpha-core against each other? How different do they sound? (assuming DCR is corrected for) |
Yes, I compared 12ga Hepta vs. 12ga Alpha. The Solen closer to no inductor. The Goertz seemed to slow the bass a little, and it was slightly sibilant.
I did not compensate for DCR. IIRC, Solen was .12 ohms and Goertz was .08 ihms. |
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| soongsc |
| quote: | Originally posted by audiobomber
Yes, I compared 12ga Hepta vs. 12ga Alpha. The Solen closer to no inductor. The Goertz seemed to slow the bass a little, and it was slightly sibilant.
I did not compensate for DCR. IIRC, Solen was .12 ohms and Goertz was .08 ihms. |
What frequency range was this for? From the DCR it seems like a 0.5mH or so value? |
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| audiobomber |
| quote: | Originally posted by soongsc
What frequency range was this for? From the DCR it seems like a 0.5mH or so value? |
I was trying to do a first-order two-way. The inductors were .39mH. |
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| soongsc |
| quote: | Originally posted by audiobomber
I'm likely going to build the 8L JX92 monitors shown on the Jordan site. I see there's a circuit suggested for frequency compensation. I assume this is BSC?
I'm not crazy about putting a resistor and inductor in series with the woofer. Can this circuit be implemented at line level instead?
Dan |
I haven't read the whole thread, but I think the compensation suggested for the JX92s varies with volume, so it is not a BSC, but rather a compensation to flatten out resonance impedance so that power can flow through and maintain good low freqjency response.
I have a few JX92s that I havent' had the time to get to yet, but I'm just starting to work it out.
I just recently got to understand what Mr. Jordans recommendations, and really appreciate those designs shedding light on lots of questions. |
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| Colin |
Yeah, Ted always refers to them as frequency compensation, not BSC.
I've heard it applied to the 8 litre reflex and it does work, filling out the bass and improving overall balance on that particular design. The 48" MLTL seems to be well enough balanced without it, although I do use them close to the wall. Out in the room, you may have other preferences.
Colin |
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| soongsc |
| quote: | Originally posted by Colin
Yeah, Ted always refers to them as frequency compensation, not BSC.
I've heard it applied to the 8 litre reflex and it does work, filling out the bass and improving overall balance on that particular design. The 48" MLTL seems to be well enough balanced without it, although I do use them close to the wall. Out in the room, you may have other preferences.
Colin |
Without the compensation circuit, the power curve looks like a band pass filter. with the circuit, it looks like trade-off some efficiency to gain greater power bandwidth. At least this is the trend analysis shows. I've just begun to try some things out with other drivers. |
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| Jim Griffin |
To understand what frequency compensation (or baffle step comp) can do to help out the JX92S (or any driver in a box for that matter), take a look at the data from my JX92S Mini-monitor as measured by Dennis Murphy at the 2001 Washington, DC DIY speaker meeting. Observe the plots at the bottom of the page on the 2001 Atlanta DIY best of show speaker (my Mini-monitor) at this link:
http://murphyblaster.com/content.php?f=DIY_2001.html
Room effects limit the accuracy of these data to 200 Hz and above. You can see a 3-4 dB and up fall off in the 200-800 Hz range which is flatten by the BSC circuit.
For what it is worth, the 2004 Atlanta DIY Best of Show speaker (this one with a JX92S and an Aurum Cantus G2si ribbon tweeter) addresses both the BSC issue and any roughness of the JX92S in the treble range. You can see data and read my report at:
http://www.creativesound.ca/pdf/JX92SG2siDesignPak.pdf
Notice that the version with the ribbon extends between 200 to more than 30,000 Hz within +/- 2.5 dB. Quite nice!
Jim |
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| soongsc |
Hi Jim,
Your data seems to match my initial analysis. I think people call this BSC just for convenience. In reality, since the values recommended varies with box volume and not baffle dimensions, it is not really a BSC. |
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| soongsc |
| quote: | Originally posted by Jim Griffin
To understand what frequency compensation (or baffle step comp) can do to help out the JX92S (or any driver in a box for that matter), take a look at the data from my JX92S Mini-monitor as measured by Dennis Murphy at the 2001 Washington, DC DIY speaker meeting. Observe the plots at the bottom of the page on the 2001 Atlanta DIY best of show speaker (my Mini-monitor) at this link:
http://murphyblaster.com/content.php?f=DIY_2001.html
|
Jim,
I know that the data for the JX92S alone had some ripple at the high end, and also some rolloff at 30deg off axis. What is the audible difference between you JX92S system and the one with the Aurum Cantus G2si ribbon tweeter? Does the 30deg off axis response look that different? |
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| Jim Griffin |
"I know that the data for the JX92S alone had some ripple at the high end, and also some rolloff at 30deg off axis. What is the audible difference between you JX92S system and the one with the Aurum Cantus G2si ribbon tweeter? Does the 30deg off axis response look that different?"
I don't have a 30 degrees off plot of the ribbon version. But in the pdf on the Creative Sound Solutions site that I referenced earlier in this thread you can see that the 15 degrees off axis performance is very flat.
Listening to the 'with ribbon version' reveals very wide dispersion--inherent with the ribbon tweeter. You don't have to toe-in the speakers to get the best sound as you would with the JX92S covering the treble range. Of course the JX92S is intended to have a 15 degrees toe-in for best treble sound but it is clear that the beaming of the radiator rolls off any high frequency dispersion. The ribbons don't have that issue until a much wider angle.
I would say that if you wish to have excellent dispersion yet capture the magic of the JX92S, then the speaker with the ribbon tweeter would give you the best of both worlds.
Jim |
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| soongsc |
| quote: | Originally posted by Jim Griffin
[B
I don't have a 30 degrees off plot of the ribbon version. But in the pdf on the Creative Sound Solutions site that I referenced earlier in this thread you can see that the 15 degrees off axis performance is very flat.
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It would be interesting to see a 30deg off axis plot. I also looked at the Aurum site, and their waterfall plot of the driver does not show the decay time in msec as usual, but rather indicates "periods", do you know what time scale "periods" refer to? |
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| erictoucan |
If you look up the phase difference with JX92S. You will find there is some 300 degrees apart between 20Hz and 20 kHz. So, I used RLC to correct the phase. It works very well with 0.5mH, 4ohm and 8-12 uF in parallel and the whole circuit in series the 92S. Enjoy the difference:-). you will find to add an impedence correction circuit at the input of speaker to balance the impedence will improve the sound too.
I do not want to write too much for someone does not read. So e-mail to me at erictoucan@yahoo.co.uk. We can talk in more details.
Do not be afraid of correction circuit will degrade the sound. You will get more than what you loss. When the phase is more corrected, you will find things sounding extreme precisely positioned and a lot better than the better two ways system |
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| Colin |
Hi - That compensation circuit sounds interesting. I'll get some components and give it a go and report back.
BTW, don't be afraid to post here, rather than on email, as I'm sure there's a number of us interested in the details.
I've recently been experimenting with a JX53 linear array and am beginning to realise how freq compensation can modify the sound in the particular cabinet I've used (an Augsperger TL design which at present sounds too 'light').
Colin |
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