Yesterday I had a most interesting visit with Martin. We listened to his OB’s using the same Goldwood 18” H-frames that I reported on to begin this thread, combined with either the Fostex F120a or the Jordan JX92s. Of equal interest to me: he had passive XO’s rather than the active XO with bi-amplification. And he presented both solid state and tube amplification!
(While the main attraction was the Fostex/Jordan comparison, Martin also showed off a pair of Alpair 10 (IIRC) with gold colored cones in small ported enclosures which he has recent completed. The Alpairs were quite handsome in nicely veneered cabinets! I guessed the bass extension to be around 50 Hz. They hadn’t fully broken in, so the sound was promising, but still rough.)
We began with the F120a and SS amp. I have said before that I found the F120a disappointing--see my comments about the Metronome I built this summer using the F120a. (see http://www.diyaudio.com/forums/full-range/85410-metronome-61.html pages 60-62.) I will say that my Mets with the F120a are either growing on me, or else the drivers are continuing to improve; I believe that the latter is the case-- where I was using a treble boost of 8 dB at 10 KHz, I have decreased the treble boost to 4 dB (at 10 KHz.) That change occurred as the drivers aged from 450 hrs to 800 or 900 hrs. Martin has fewer hours on his F120a’s, so I was not terribly surprised when they sounded less than wonderful. Percussive notes were just wrong. Cymbals and triangles lacked the proper ‘ring’ and brushes were mushy. My ‘fix’ was to apply a treble boost, but since Martin’s pre-amp has no tone controls, the only thing we could do is to switch amplifiers. Changing over to a tube amp was a revelation! Suddenly everything sounded right--with the exception of the bass, which was now rather weak. In the past, while auditioning speakers, I have listened to the same speaker where the amp was switched from SS to tubes; the time that comes to mind was using McIntosh gear driving PMC FB-1+ speakers. In that case, the differences between SS and tubes were very minor. Here, it was like night and day--percussive notes were now crisp and detailed. After hearing this, I may re-consider buying a tube amp.
And as to the bass: I say the same as I did at the start of this thread: full, rich bass; lots of detail & nuance. The H-frames with the Goldwood drivers do bass the way it was meant to be--at least for music. Can’t say if the HT folks would like them or not, since we didn’t listen to any explosions or cannon fire.
The F120a’s were then switched out for the Jordan JX92s. If the tubes provided more in the high end for the F120a’s, would they cause the JX92s’s to burn your ears off? In a word, NO. Driven by the tube amp, the Jordans seemed to have more bass than the Fostex. Is there a small difference in the XO which might cause this? I don’t know, but the bass, while still weak, was closer to acceptable. And the mids/highs were better than the Fostex. Switching to the SS amp resulted in very minor changes in the mids/highs, but the bass came back. When I heard the Jordans before, I found them a bit bland--they did nothing wrong, but they just didn’t grab me. This time I found them much more engaging. It might be that the balance between the Jordans and the Goldwoods is different with the passive XO, or perhaps the drivers have more hours on them now. Either way, I found the Jordans to be quite pleasing! In fact, we spent the remainder of the time listening to Eva Cassidy’s Live at Blues Alley through the Jordans.
Summary of Observations:
1) The F120a isn’t as wonderful as might be hoped.
2)The JX92s is really a nice driver.
3) There may be a point to using tubes, but the amount of goodness they impart depends greatly on the driver they are connected to. And there may be some draw backs (as in, where did the bass go?)
4) Passive XO can be used for many OB configurations without ruining the performance of the full range driver.
5) For truly musical and stunning bass for ridiculously little money, the H-frame with either a Goldwood 18” or an Eminence Alpha 15a is the way to go!
Cheers, Jim
(While the main attraction was the Fostex/Jordan comparison, Martin also showed off a pair of Alpair 10 (IIRC) with gold colored cones in small ported enclosures which he has recent completed. The Alpairs were quite handsome in nicely veneered cabinets! I guessed the bass extension to be around 50 Hz. They hadn’t fully broken in, so the sound was promising, but still rough.)
We began with the F120a and SS amp. I have said before that I found the F120a disappointing--see my comments about the Metronome I built this summer using the F120a. (see http://www.diyaudio.com/forums/full-range/85410-metronome-61.html pages 60-62.) I will say that my Mets with the F120a are either growing on me, or else the drivers are continuing to improve; I believe that the latter is the case-- where I was using a treble boost of 8 dB at 10 KHz, I have decreased the treble boost to 4 dB (at 10 KHz.) That change occurred as the drivers aged from 450 hrs to 800 or 900 hrs. Martin has fewer hours on his F120a’s, so I was not terribly surprised when they sounded less than wonderful. Percussive notes were just wrong. Cymbals and triangles lacked the proper ‘ring’ and brushes were mushy. My ‘fix’ was to apply a treble boost, but since Martin’s pre-amp has no tone controls, the only thing we could do is to switch amplifiers. Changing over to a tube amp was a revelation! Suddenly everything sounded right--with the exception of the bass, which was now rather weak. In the past, while auditioning speakers, I have listened to the same speaker where the amp was switched from SS to tubes; the time that comes to mind was using McIntosh gear driving PMC FB-1+ speakers. In that case, the differences between SS and tubes were very minor. Here, it was like night and day--percussive notes were now crisp and detailed. After hearing this, I may re-consider buying a tube amp.
And as to the bass: I say the same as I did at the start of this thread: full, rich bass; lots of detail & nuance. The H-frames with the Goldwood drivers do bass the way it was meant to be--at least for music. Can’t say if the HT folks would like them or not, since we didn’t listen to any explosions or cannon fire.
The F120a’s were then switched out for the Jordan JX92s. If the tubes provided more in the high end for the F120a’s, would they cause the JX92s’s to burn your ears off? In a word, NO. Driven by the tube amp, the Jordans seemed to have more bass than the Fostex. Is there a small difference in the XO which might cause this? I don’t know, but the bass, while still weak, was closer to acceptable. And the mids/highs were better than the Fostex. Switching to the SS amp resulted in very minor changes in the mids/highs, but the bass came back. When I heard the Jordans before, I found them a bit bland--they did nothing wrong, but they just didn’t grab me. This time I found them much more engaging. It might be that the balance between the Jordans and the Goldwoods is different with the passive XO, or perhaps the drivers have more hours on them now. Either way, I found the Jordans to be quite pleasing! In fact, we spent the remainder of the time listening to Eva Cassidy’s Live at Blues Alley through the Jordans.
Summary of Observations:
1) The F120a isn’t as wonderful as might be hoped.
2)The JX92s is really a nice driver.
3) There may be a point to using tubes, but the amount of goodness they impart depends greatly on the driver they are connected to. And there may be some draw backs (as in, where did the bass go?)
4) Passive XO can be used for many OB configurations without ruining the performance of the full range driver.
5) For truly musical and stunning bass for ridiculously little money, the H-frame with either a Goldwood 18” or an Eminence Alpha 15a is the way to go!
Cheers, Jim
Albert,
Amazing set up!
Did you mean Goldwood 1858 or you are bringing a new player, the Goldwood 1585?. In the latter case, would you share with us why did you chose it over the alpha 15 and the Goldwood 1858?
Antonio
The MCM Plate amplifiers have second order crossovers, and are very reasonably priced (the 200 watt amp goes for $99), which is why I am considering them.
Bill
Sorry for the typo mistake.
I only have the goldwood 1858 by now, I thought you better ask Godzilla for the Alpha 15. The reason, to choose the 1858 from the very start, is to stack with the original design. Don't forget I'm a old newbie.
Albertli,
Yes, I am also an old newbie and for the same reason I am thinking about going for the original design and to copy exactly Martin's crossover to avoid complications. However, my main concern with the Goldwood is that they might be too much if the room is not big enough.
I have read Godzilla comments on the Alpha 15. I am sure both are equally good and only an A-B comparison might reveal some differences. If I remember correctly another member was on the process of building both to compare them.
One question albertli. Have you tried placing the H frames very close to the wall, for example a foot or less? Does this affect the sound considerably? does the bass disappear or become boomy? I know Martin recommends at least two feet, but I would like to now if someone has actually tried placing them closer to the wall..
Thanks
Antonio
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I have all the parts for the Alpha 15 and plan to cut wood this weekend. Might be Thanksgiving before I get some serious listening time, though. Then I can make the comparison with the Goldwoods.
I also have some high power L-pads laying around and will try to throw a couple in this weekend to see if they have a noticeable effect on the sound. While I have the equipment to measure, it is disruptive to move everything so will use the ear/brain perceptual system for now.
Might also hook up the Aleph 2 clones I have in place of the VT-130, although the BAT preamp gripes about driving the Alephs, with their lower input impedance. Will keep everyone posted, but the bottom line is that I have a few powered subwoofers that might be going up for sale soon.
Craig
I also have some high power L-pads laying around and will try to throw a couple in this weekend to see if they have a noticeable effect on the sound. While I have the equipment to measure, it is disruptive to move everything so will use the ear/brain perceptual system for now.
Might also hook up the Aleph 2 clones I have in place of the VT-130, although the BAT preamp gripes about driving the Alephs, with their lower input impedance. Will keep everyone posted, but the bottom line is that I have a few powered subwoofers that might be going up for sale soon.
Craig
F120A feedback
It appears that quite a few folks have not been overly satisfied with the F120A. My pair is from an older stock from Madisound going back a few years. A conversation with Adam at Madisound noted that they were going out of production and that they were being manufactured only when enough orders made it sensible to build some quantity of them. It was also noted that they were using parts on hand and that once the parts ran out they would no longer be made.
I don't know if this is still the case or not. However, I suppose it's entirely possible that later manufacturing runs where not at the same level of construction quality which may account for the lackluster performance. The older pair I have do sound very nice and immediately blew away the FX120 drivers I was using... and those are pretty decent for the money and very similar to the F120A using many of the same core components.
Regards, KM
It appears that quite a few folks have not been overly satisfied with the F120A. My pair is from an older stock from Madisound going back a few years. A conversation with Adam at Madisound noted that they were going out of production and that they were being manufactured only when enough orders made it sensible to build some quantity of them. It was also noted that they were using parts on hand and that once the parts ran out they would no longer be made.
I don't know if this is still the case or not. However, I suppose it's entirely possible that later manufacturing runs where not at the same level of construction quality which may account for the lackluster performance. The older pair I have do sound very nice and immediately blew away the FX120 drivers I was using... and those are pretty decent for the money and very similar to the F120A using many of the same core components.
Regards, KM
Check out this paper from Adire about "woofer speed" and the effects of mass loading versus coil inductance. http://www.adireaudio.com/Files/WooferSpeed.pdf
I've just discovered this thread and have read all 36 pages with great interest. I would love to mate a Lowther driver in an OB with an Alpha 15 H frame but realise there would be a rather large sensitivity mismatch. So what if I use a DX2 which has a slightly lower sensitivity of 97dB and use 2 Alpha's in an H-Frame, one above the other.
Martin, any thoughts on this - Also how would I go about modelling 2 drivers in your mathcad H-Frame worksheet and is this even possible. I did simulate the DX2 combined with 2 Apha's in the 3 driver mathcad worksheet and got a pretty flat response of 97dB rolling off to 95dB at 50Hz and 90dB at 36Hz. This is a pretty good result but I'd just like a tad more bass extension which I what I am hoping to achieve with the dual driver H frame.
Thanks,
Graham
Martin, any thoughts on this - Also how would I go about modelling 2 drivers in your mathcad H-Frame worksheet and is this even possible. I did simulate the DX2 combined with 2 Apha's in the 3 driver mathcad worksheet and got a pretty flat response of 97dB rolling off to 95dB at 50Hz and 90dB at 36Hz. This is a pretty good result but I'd just like a tad more bass extension which I what I am hoping to achieve with the dual driver H frame.
Thanks,
Graham
A DX2 and a pair of Alpha 15A woofers in an OB would work very well. I think I looked hard at that combination once and it worked even with a passive crossover. You can find measured T/S properties for most of the Lowther drivers on my site under the "General Speaker Related Articles" link.
You can model two drivers in an H frame or U frame using the same technique as shown in my modeling two drivers write-up under the "General Speaker Related Articles" link. Model the drivers in parallel and enter the equivalent driver properties in the H frame worksheet. Then model the actual H frame geometry and it should give you the correct result. The bass extension will be lower but at the expense of a little efficiency.
I really don't know anything about the Lowther DX65 so I can't be too specific, but my guess is that it would work in an OB paired with one or probably more 15" woofers.
The 16 ohm impedance of the woofer is going to mean very large inductors and caps if a passive crossover is going to be used, this might be a problem and very expensive (but if you are using a Lowther that is all relative). If you are going to use an active crossover then that point becomes a non-issue.
I personally would not spend too much on the woofer, a 15" driver covering only up to 100 to 200 Hz is not that special or demanding so a less expensive Goldwood or Eminence should work well. In a reasonably sized OB you are probably not going to get much below 40 Hz so spending more for the AE driver seems like a waste to me. It would not hurt to use an AE driver but I don't see much benefit.
What about H frame with 12' drivers.
Thank you all for your previous answers to my questions.
For the sake of experimenting and due to current WAF problem, I am considering building the H frame JX92s combo but with 12" drivers. I have been checking parts express and have found some 12" drivers with Qs above 1 but low SPL (90 or less) or higer SPL but smaller Qs
Example:
Parts-Express.com: Goldwood GW-212/8 12" OEM Woofer 8 Ohm | woofer gw-212/8 12" woofer goldwood woofer GOLDWOOD WOOFER shielded woofer midbass goldwood pismo series PismoWoof123008 12 IN WOOFER
Is this one suitable? Any suggestions?
Many thanks
Antonio
Thank you all for your previous answers to my questions.
For the sake of experimenting and due to current WAF problem, I am considering building the H frame JX92s combo but with 12" drivers. I have been checking parts express and have found some 12" drivers with Qs above 1 but low SPL (90 or less) or higer SPL but smaller Qs
Example:
Parts-Express.com: Goldwood GW-212/8 12" OEM Woofer 8 Ohm | woofer gw-212/8 12" woofer goldwood woofer GOLDWOOD WOOFER shielded woofer midbass goldwood pismo series PismoWoof123008 12 IN WOOFER
Is this one suitable? Any suggestions?
Many thanks
Antonio
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Thanks Martin, I modelled the dual Alpha H-Frame and found that SPL increased to 90dB and bass extension was about 7Hz better on the lower end than with a single driver. The 200Hz rolloff on the other hand seems a bit trickier to get right with 2 drivers. A 2nd order Linkwitz-Riley filter with a low pass frequency of 200Hz seems to give around the same rolloff point as with the single driver, but the slope is much more gradual and at 1KHz is still about 68dB. I guess I need to play around with the simulations a bit more, but all in all a very positive outcome. Thanks once again.....
Graham
Both the Eminence Alpha 15A and the Goldwood GW-1858 are just over 94 dB/W/m efficient. That efficiency is what you should have for the H frame driver for it to mate easily with the Jordan full range driver using a passive crossover. If you are going to use an active crossover, and can apply boost to the bass driver, then the lower efficiency Goldwood option you have linked would probably work.
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