Pete B

Hi Russ, Interesting comments regarding your comparision of the 5012 to the LA. Do you happen to know if the 5012 woofer has a raised backplate? We discussed this in another thread as you might have noticed. It might be slightly better than the New LA woofer, mainly when pushed hard. I'd like to hear those 5012W's I'm curious now. Best regards, Pete B. >Hello, gks. > >I have a pair of 5012W's, made during the Jensen years. To me, >they sound exactly like the Advent Loudspeaker, though the >x-overs are different and the cabinets are slightly larger in >every dimension—about 1/2 inch. > >They never seem to draw much interest on eBay, and rarely come >up there. So I have this very nice pair, in very nice >condition, with new poly caps and pretty fresh woofer >surrounds, and I'm wondering what to do with them (since I >already have 4 Advents in a double system and two very lovely >Smaller Advents I recovered in white birch veneer and >refurbished with new tweeters and x-over components—AND >resting securely on beautiful stands I made myself). > >If you have the answer to THAT, you most certainly ARE and >expert, because anyone who knows what action I should take has >to be an expert. I am expert at many things, but knowing what >to do is not usually one of them ;-). > >Your original post was engaging. > >Best wishes. > >Russ Wollman > >

AR claimed 97 dB/2.83V/1m for these speakers and given the relatively typical box volume used I thought they must not have deep bass, or they will not make the efficiency rating. You cannot beat the bandwidth/volume/efficiency tradeoff as predicted by Thiele and Small theory. Sure enough the frequency response curve shows that the system produces an average of about 94 dB from about 150 Hz to 9 kHz. It is possible to make relatively efficient midranges and tweeters. The response steps down to an average of about 89 dB from about 120 Hz to 80 Hz, and it is down a significant 14 dB at 40 Hz and about 7 dB at 50 Hz. An interesting comparison is to the Large Advent which is down about 1 dB in the low 40s, ignoring baffle step losses. It is clear that the woofer is fairly typical with a sensitivity of about 89 dB in the passband. The modification that I've suggested pads the mid/tweeter section down by about 6 dB and since the problem is differing efficiencies, it should provide a good correction from the start of the woofer passband at 80 Hz on up into the tweeter range. There is a 5 dB dip in the frequency response at about 12 kHz which probably explains the lack of air. Keele also notes that the left system was down 5.5 dB at 10.6 k compared to the right and -4dB at 18.1 kHz. I wonder if there is a consistency problem with these tweeters. The vent seems to be tuned to 30 Hz and there is a layer of fabric in the port to lower the Q. This is generally considered to be a bad idea, and indeed Keele noted that the fabric added significant distortion flapping, with high output in the deep bass. Keele notes that the woofer is robust and handles a lot of power without a problem. I also found them to handle significant power without strain. I expect that the 310HO will be even worse as far as deep bass goes having a 10" woofer. I plan to measure and simulate, when I have the time.

I want to mention that I based this mod on the frequency response published for the AR 312 HO and therefore it should work well for that model also. They are very similar mainly 10" vs. 12" woofers.

I'll just mention that these speakers are nothing like the vintage ARs they're vented after all, could anything be more un-AR? This is an old friend from many years ago who I'd not spoken to in a long time, he upgraded his system after hearing mine, he was due for it anyway I suppose. He's not an audiophile and not obsessed with Audio. I asked him if I could offer his comments here about how weak they were in the bass, and he said "what you should say is that there's no deep bass WHAT SO EVER". He said I even tried an EQ and could not get low bass out of them. He said "my AR-15s have better bass and they're much smaller, I never liked the AR310HOs from the day I brought them home." We A/Bed them to my reference system and he said in normal language that the instruments sound all mixed together. I'd call it veiled or a lack of transparency in audio speak. I found them to sound boxy, and to have a shouty cupped hands quality, and no deep bass. They also seem to lack high end extension above 12 kHz. They do seem to have good driver integration and a smooth but colored sound in my opinion. I was expecting the lack of bass since I had read the review of the 312HO in Audio and seen the FR curve. Also noticed that there is damping in the port which is usually not recommended. He asked if we could fix them, I said probably but that I wanted to look into it first. I suggested selling them as is, but he wants to modify them. I decided to see what I could do while I had them in the system and here's an external mod that we both found to be a significant improvement: 1. Remove the biwire input strap on the + terminals. 2. Put a 20 ohm 10W resistor across the HI range terminals. 3. Put a 4 ohm 20W resistor from the woofer + to the HI range +. 4. Put a 10 uF poly or mylar cap from the woofer + to the HI range +. 5. Wire the Amp to the Woofer input terminals. He came to listen today and was impressed with the improvement, listened carefully, saying this is not subtle, it is a significant improvement. Now he's interested in substituting a better woofer. There's enough box volume to use the standard AR 11/12", however I've found a 12" woofer that should work well in a vented configuration. I will redo/modify the crossover as needed to work with the new woofer. I'm interested in listening impressions from people who might be interested in trying this minor mod.

Thanks again Dave, OK, I understand. As I mentioned back in the thread the original TV woofer voice coil was wound on a paper former, this compared to the Advent for example with a solid metal former did not handle much power at all. Played loud, the coil will overheat and deform, even burn the paper former. You probably have burnt and/or partially shorted windings or one that is badly deformed and not moving freely. The only way to bring them back to original condition is to find new/used woofers on e-bay for example. This is what I did because I wanted a completely stock pair for historical reasons. We can give you some tips for buying on e-bay if you'd like. Also keep in mind that not only do the paper former woofers burn out more easily, they heat up more easily under normal playing and the copper resistance goes up, you might be surprised by how much, which leads to what we call thermal compression. The woofer output fades by a few dB as they heat up. I believe that the Madisound 25F-EW is a good replacement, but remember that it is about 3 dB more efficient, and you might want to add/move one wire in the crossover to raise the tweeter level as compensation. We're fairly certain that the 1976 F-EW was used in the more efficient A-25XL. I'm also fairly certain that it has a better voice coil former, will handle more power, and will have less thermal compression. I believe that the stronger motor will result in slightly less bass output at the lowest end of the woofer range due to the stronger damping. I've not tried or tested the 25F-EW H085 version so this is what I expect based on the theory, T&S parameters, and published response curve for the 25F-W H085. Another alternative is to pad the H085 woofer with some series resistance to weaken the motor and make it more like the original while retaining the better thermal capacity. I worked out the resistor values for the F-EW that I have and they should work for the H085 if you'd like to try it. Nice thing about this is you can try it both ways. Pete B. >Pete, > >I definitely have the A25s with the larger tweeter. And the >reason I need woofers is because years ago a house sitter of >mine must have crank the music very loud for a long time >(while I was away). When I returned the speakers sounded >awful. The cones look fine but I'm just guessing that the >magnets were fried. I guess I should check that out but I >don't know what to look for. > >Could something else be causing the bad sound? >How could I check this out myself? > >Thanks for your generosity. > >Dave

Hi Dave, Thanks for your generous comments. Maybe it didn't come across in my last post but I was mistaken, thinking there was only one 25F-EW, there are two different H versions, H085 and H250. I purchased these A-25s recently and one had an 25F-EW H250 which is not what Madisound suggests and is simply the wrong woofer. I've not heard or measured the H085 but it looks very close to the FEW that was probably used in the A-25XL. You say you need new woofers, why are they damaged, or do you think they're the wrong ones? Are you sure you've got A-25s (1.5" tweeter, 5 pos switch) and not A-25XLs (1" tweeter 3 pos switch)? If you have A-25s and you want original woofers, then yes I'd look for 25TV-EW 8 ohm woofers on ebay. If you have A-25XLs or want to try an XL type woofer, then you can look for an old 25F-EW on ebay, or the new one from Madisound, but not the H250. Please let us know about your findings. >Pete, >I read your posts. Wow, you really are "the man" >when it comes to integrity of sound. I have two A25s that need >woofers. I found Madisound and was a litte distressed by your >review of their replacements. (My current woofers are not >coated paper but look more like the ones on Madisound's >website.) I also found woofers advertised as original used >with the model number of #25 TV-EW. Are these, in fact, the >correct item number? > >What are your thoughts? > >Thanks.

I've mentioned that the 25F-EW (H250) does not seem right. The one I have came in an A-25 system, and I thought it was the only version. I just noticed on the Madisound site that the 25F-EW that they suggest is the different H085 version. http://www.madisound.com/cgi-bin/index.cgi...=3D%25&pid=1035 Here's a picture, note the mostly uncoated paper cone and the different dust cap as compared to the early 25F-EW: http://www.madisound.com/images/product/H085.jpg And here is the H250 version, from 1990 (date code 48/90) that I've been talking about, note the fully coated cone: http://members.aol.com/basconsultants/25F-EWF.jpg http://members.aol.com/basconsultants/FEW2.jpg Here is an older 25F-EW, from 1976 (date code 42/76) that appears to have exactly the same cone as the original 25TV-EW: http://www.classicspeakerpages.net/dc/user_files/1495.jpg http://www.classicspeakerpages.net/dc/user_files/1494.jpg I believe that the H085 is probably the closest SEAS 10" to what was used in the A-25XL and is probably a good, but more efficient replacement for the old 25TV-EW. My comments about the F-EW only apply to the H250 version that I heard/measured.

Thanks for the interesting input Vern, I've never seen the insides of an A-50. Yeah, about marketing literature, I had to go work in the real world to learn about "dog and pony" shows: From: http://en.wikipedia.org/wiki/Dog-and-pony_show "The term has come to mean any type of presentation or display that is (1) somewhat pathetically contrived or overly intricate or (2) put on for purposes of gaining approval for a program, policy, etc." I was wondering, have you ever seen and F-EW type woofer with this type of cone used in any production Dynas: http://www.classicspeakerpages.net/dc/dcbo...d=141&page=#150 Best, Pete B.

A few comments about voice coils: Years ago in my early days experimenting with speakers I noticed that even some inexpensive but decent drivers such as the $2.49 CTS 4.5" driver used in the *ose 901 employed what appeared to be an aluminized paper voice coil former. Whereas many of the European drivers used a paper former. I was given a pair of A-25s where one of the woofer (25TV-EW) voice coils was burnt out. I know that it had a paper former because I removed it and it was burnt with the windings coming loose. I measured the gauge of the wire, counted the turns, and wound a new coil on aluminized paper and repaired the driver. I also used the Phillips AD8060 8" woofers in pairs and we would often smell something burning when we turned up the system. These failed more slowly, over many years, with the paper former just looking browned and cooked like toast, and the enamel on the wire completely black with the windings mostly shorted. A good heat conductor is needed to sink the heat out of the voice coil. This is well known today and even most tweeters employ solid aluminum voice coil formers or at least aluminized paper. Note also that the 1.5" tweeter in the A-25 had a paper only former, and the larger than usualy size helped to give it some thermal capacity. I believe that the 25F-EW woofer has a better former, either aluminum or aluminized paper as it has a higher power rating. The A-25XL system also has a higher power rating. Pete B.

Interesting Vern, Yes I'd agree about prototypes and spot checks, makes sense. I'd read about the partioned cabinets for the A-35 and 50 but have never had a look inside one. Thank you, Pete B.

Hi Vern, Thanks for the dates of those reviews. I might look them up one day. I do remember the old Dynaco literature that mentioned tuning each A-25 with a 5 Hz square wave. I think this was marketing hype, every A-25 I've seen has been stuffed the same way. I do also think they showed the tone burst tests. I do think I have that around here somewhere but I've not had my finger on it in some time. Best, Pete B.

Hi Vern, The new driver is about 3dB more efficient in the pass band piston range. By this we mean above the bass region where the box and fundamental resonance come into play and below frequencies where the cone does not approximate a point source very well, and/or has breakup modes. This is very roughly 150 to 400 Hz, and if this was all that was different, we could turn up the level on the tweeter to match it and we'd have a system that was 3 dB more efficient across the audio band. However, it measures even more efficient around 2kHz and up by about 5 to 6 dB so yes it will be much more forward in the presence region. The stronger magnet and lower Q reduces the low bass output, relative to the pass band, which I've not measured, but is probably around a few dB. +3dB in level for equal voltage input is twice the acoustic power. It's like driving the original woofer with an amplifier with twice the power. It would be nice to find a way to make this higher efficiency driver work and take advantage of the higher efficiency. If you were to compare a system with the replacement driver by matching levels in the piston range where it is 3 dB more efficient, as I did, you'd hear a few dB less bass around 60 Hz, and 2 to 3 dB more output around 2 to 4 kHz, going from memory here. It is more forward sounding and not in a good way at all. Turning the tweeter level all the way up on the original system made them sound much closer. I don't know about any 9-10 kHz resonance, it's probably inaudible if it's just a few cycles of ringing. Was this tone burst testing, as was common in the old days? I don't think I've seen any A-25 reviews in a very long time, except for those in Stereo Review for the A-25 and A-50 which are not very detailed and mostly praise them. I did look on the web recently. Who were the authors of these reviews? Pete B.

Post by Vern copied here, and my answer follows: >Hi Vern, > >Thanks again very much, nice of you to comment. >I mentioned about the sound differences in the other thread, >about 3 dB more output 200 to 500 Hz, and even more above, >about 5 dB more above 2 kHz. Hi Pete; Will this cause a boomier bass or more mid range presence? Original Dynaco A-25's were noted as having a extremely smooth response in this area. Is 3db double the output in this regard? In my reading of old Dynaco literature yesterday, I came across a report of a 9khz and a 10khz resonance, one each from two different sources. One source still tested and claimed outstanding transient response at the 10Khz, at the same time as it also showed a 10khz resonance photo. Can we hear this resonance as a screech, buzz or rattle? As always, Pete, a very informative write-up from you, thank you. Magnet is stronger so the Q is >lower resulting in less low bass. >Any film cap will do just fine, I didn't have a 1 uF so I used >a pair of .47 uF Panasonic Polys in parallel. > >I used Axons to replace the 5 uF, and would have used them for >the 1 uF if I had them. Anything over a 100V rating is fine. > >The cap just adds some "air" to the sound, not like >turning up the treble or the switch on back, because it's only >lifting the very high end. More like moving forward in your >seating location. It is subtle but important for realism. > >Pete B. > Have a good one. Vern

My reply to a few questions in another thread: I mentioned about the sound differences in the other thread, about 3 dB more output 200 to 500 Hz, and even more above, about 5 dB more above 2 kHz. Magnet is stronger so the Q is lower resulting in less low bass. Any film cap will do just fine, I didn't have a 1 uF so I used a pair of .47 uF Panasonic Polys in parallel. I used Axons to replace the 5 uF, and would have used them for the 1 uF if I had them. Anything over a 100V rating is fine. The cap just adds some "air" to the sound, not like turning up the treble or the switch on back, because it's only lifting the very high end. More like moving forward in your seating location. It is subtle but important for realism. Pete B.

Dynaco A-25 schematic: http://members.aol.com/basconsultants/DYNACO-A25-XO.htm Pete B.

Hi Vern, Just waanted to mention that if I sound cranky above it is not directed at you in anyway, just based on past exchanges with a few others. Always nice to hear from you. And all the best to everyone for the 4th! Pete B.

Hi Vern, I'd like to hear your impressions comparing the two and for any stacked combinations you try, should be an interesting read. I think many people did the double Advent because it was suggested by Kloss. There is almost "magic" when speakers are paired up, their SPLs add in the same way as in phase voltage sources, and therefore the acoustical power goes up by a factor of 4, or 6 dB, while pulling, if the amplifier can handle it, only twice the electrical power due to the load impedance being one half. The efficiency nearly doubles. Also, the maximum SPL goes up by a factor of 4 rather than just 2 because of this effect. The volume displacement is doubled, which raises Max SPL by 6 dB, not 3 dB as might be expected on an intuitive basis. This is highly unintuitive and part of the detailed explanation is that direct radiator drivers are so inefficent to start with. Many incorrectly associate this with mutual coupling which is not the reason. There are AES papers covering this in case anyone is thinking of challenging the claim. Pete B. This subject is often misunderstood and I often find people on the internet, sometimes professionals, who try to contest and debate the matter. I just came across this writeup about Professor W. B. Wadsworth who I was lucky enough to study Audio and Acoustics with: http://www.auditory.org/asamtgs/asa94mit/3pNS/3pNS3.html I was surprised to hear some years ago that often students at the best universities have little access to some of the world renouned professors who are shielded by graduate students. I did project work with Professor Wadsworth, many years after his work in the 1950s, and if he heard me mention something like mutual coupling, or back EMF showing that I didn't fully understand the material, he'd sit me down in his office and explain it until I did understand it, sometimes referring me to the literature. He thought it important to know the history and give credit to original ideas, he told me of the very early work by Rice and Kellogg for example: http://history.acusd.edu/gen/recording/loudspeaker.html I was lucky because he was a briliant and patient gentleman, even other professors would smile and say, he's on another level, his understanding was so deep.

Hi Vern, I tilted them years ago just to find the best listening angle. Yes, I do think being more on the tweeter axis helps with the directional tweeter. Forgot to mention that I'm not convinced it's the near linear phase property that provides the good sound since the frequency response also varies strongly with vertical angle. I never have heard doubles, I take it you have? How are they? Pete B.

I was recently asking about people's thoughts concerning tilt back for the Dyna A-25's. There was a reason. The Spica TC-50 claims to be, and is to some extent, a linear phase design. It uses a crossover that is a non-standard design and requires time delay on the tweeter, or advance on the woofer depending on how you look at it. I found, in simulation, that I could also obtain a fairly linear phase response with the A-25's by advancing the woofer in time as would be seen by tilting back the enclosure, or listening in a position that places the woofer closer to the listener. The Spica uses a first order network on the tweeter as does the A-25. It also uses an approximate 2nd order network on the woofer, however it too is nearly first order electrical as a result of the values chosen. Spica claims a Bessel response on the woofer, but that is not what I saw in simulation. I have noticed for years that the A-25's sound best tilted back and was not aware of this nearly linear phase characteristic. Pete B.

I did more work on these some time back and I've been meaning to post about it here. I did a quick simulation with approximate models of the drivers in order to determine the attenuation level of the 5 switch settings. I also determined the values for a voltage divider to match the newer, more efficient woofer to the old design. I just want to get these into good working order and plan to get back to them someday and really dig in with more acoustical measurements. I implemented the resistor divider for the new woofer and compared the two systems. The system with the newer woofer sounded as if the tweeter was significantly more efficient. This system on normal sounded like the original system full up. I thought it was a tweeter problem, then decided to measure the woofers above 2 kHz. I know these drivers fairly well and expected them to have similar cone behavior, which turned out to be wrong. The newer woofer is much more efficient above 2 kHz, between 3 and 5 dB as I recall, probably due to a stiffer cone. I had planned to buy a replacement woofer on e-bay, but wanted to determine what was needed to properly fit the newer woofer to the old design. I've decided that it's not worth the effort at this point since a more complicated crossover network will be required for the woofer. I finally purchased an original type woofer on e-bay, and will test it soon. Pete B.

I was mistaken, I visited and heard this same pair of A's again today. I looked close and what do you know the tweeter is an Audax not a Peerless. I was fairly certain but I did only see them from a distance the last time. This time I am certain that it looks like an Audax. Like one of the very popular fabric domes, no way to know the exact version without looking inside since there were many variations. These are the original tweeters as the speakers are with the original owner and he has never changed them. The midranges had been replaced since the last time with a driver from Snell that looks like a custom unit. The frame looks like a well known Pioneer, mid but not the cone or dustcap, looks like a custom unit. It does not have the hexagonal frame like the original. The owner is now biamping them with the matching Snell crossover and the system sounds very good especially for a vintage system. Pete B.

Here is a link to the frequency response of the Small Advent as measured by High Fidelity in the 1970s. Please note that Advent claimed that the Large and Small Advent were designed to have the same voicing, however the Small Advent was less efficient: Please note that I did not scan this, the Small Advent is the first curve, the other two are unrelated: http://members.aol.com/Debertin/spktwo.jpg Pete B.

I posted this on another forum and it applies to the A-25 because it uses such a large vent: I've been meaning to write more about aperiodic systems for some time now. Dick Pierce does a fine job here: ...a variovent can be accurately modeled using a standard vented model (4th order) with the following adjustments: 1. Since the vent diameter is relatively large and the vent length essentially the thickness of the panel it's mounted in, the actual vent mass is quite low, that results in a box resonance which is much higher than would be considered reasonable for a vented system, which means that a system aligned with such a port would indeed have a very strange response, if it were not for the fact that: 2. With the damping in the vent, the port losses are extremely high, the resulting Qp is VERY low (around 1-2 max), and thus the action of the port at box resonance (at the high frequency it has) is significantly attenuated to the point where the contribution to the system's total volume velocity is essentially attenuated to insignificance. The result is a vented system with a high Fb that has a very low Qb. Such systems, while still technically 4th order, approach 2nd order behaviour at and below resonance for a significant range. What advantage does this have? Well, with normal woofers, it's not dear. It has no efficiency advantage over properly designed closed boxes, it does not have the bandwidth or efficiency advantages of lower-loss vented systems. It might have an advantage when you are forced to use a high-resonance, high Qts woofer (just like some of the woofers Dynaudio makes, for example). But, magic it is not. Dick Pierce Loudspeaker and Software Consulting 17 Sartelle Street Pepperell, MA 01463 ----------------------------- I believe that Dick Pierce was referring to the A-25 which does have high port area, but there were others with much less area that might work better. The Audio Concepts sub based on the DV-12 woofer from many years ago is an example. I plan to measure the A-25 some day, but that will likely be far in the future. Pete B.

aroostookme writes: > >The one on the bottom not in a canister is the Snell A mid. >The other two in their original canisters are from the >Dahlquist 10's and have the same markings as the Snell A >mids. Your pictures are absolutely of the AD5060SQ version, the midrange or "squaker". The woofer version had a different edge and dust cap, at least the samples that I have. However, in the Dahlquist DQ-10 the rear chamber was removed (or perhaps they made a special order without the rear chamber) and it was mounted with the rear open with a piece of felt over the back. This has been clear in every picture that I've seen of DQ-10s. I don't know about the Snells but the pictures that you have there with the rear chamber look exactly like the stock AD5060SQ8. I don't know if a 4 ohm version was ever made and it would be good if you could measure the DC resistance. Pete B.

These 12" Auras would be high on my list for evaluation if I were to do a modernized acoustic suspension 3-way system. However, they are rather expensive. While these would work fine in a 4-way, I'd probably choose a driver with even more Xmax for such systems. Pete B.