Help with Dunlavy SC-IV signature
Hello to all. I friend recently gave me a pair of SC-IV as they were too big for his room and he did not like their sound. The speakers sounded very bright to me but I attributed that to the cheap surround sound receiver he was using. I expected them to sound way better on my gear. No such luck. I tried them with a Moon P5 and Ayre v3 and they made my ears bleed, same with aMusical Fidelity M6PRX and Pre. I finally put then on a Nakamichi CA7 and PA7 with the tone controls all the way back and they started to sound way better. My current speakers are Martin Logan Expression 13A and Von Schweikert VR4 Get III. I added a Behringer DEQ2496 and turned the mids and highs down 7db and now they sounded very good. I have had Vanderstein 5A, Magnepan 3.7i and Utopias among others and I have never encountered something this bad. It's as if an equalizer was turned all the way up in the mids and highs. I removed one of the crossovers and to the eye they look ok I would have to remove them and measure everything to know for sure. Has anyone run into this before ? should I rebuild the crossover to see if it will improve ? What other measurements should I take ? Thanks in advance for your assistance.
Duntech/DAL crossovers - The crossover board on my Duntech Princess was accessed by a removable panel on the back of the cabinet. Once opened the board could be slid out since mounted on drawer rollers. A friend of mine with design background was curious to see that crossover so I opened it up for him. He exclaimed, "All it needs is a transformer and it would be as complex as an amplifier." I don't have an electronics background but that board was stuffed with parts and looked complex to me! |
@cerberus79 Somebody messing with the crossovers would explain a lot of things. John and team measured every single raw driver and entered all the measurements into a computer, computer-selected a set of matched drivers to build a pair of speakers, then tweaked every crossover in real-time to get the measurements he wanted, that were within a certain tolerance of his reference. Every single completed speaker, even within a matched pair, has slightly different values for the crossover components. |
@cerberus79, good that you got to the bottom of the problem, even after no longer owning the speakers. I enjoyed a pair of Duntech Princess speakers for 19 years and would like to clarify a few points here. John Dunlavy began his speaker business, Duntech, in Texas before moving it to Australia. That company continues in business under other ownership. His Duntech models were high quality in design, components, and build. John believed in time and phase coherency and based his designs on that. But my Princesses were rated at 90 dB which may have misguided some. The manual recommended at least 200 wpc "for musical enjoyment" and I found that to be true. The best match I found was with VTL 300 monos, and later Parasound JC-1 mono amps. At one point John returned to the US to begin building a new Duntech model. My assumption was his concern over the high shipping costs from OZ because of size and weight, so a model built in the US could be more competitive. However it was not a sales success and John separated from Duntech to begin another company, Dunlavy Audio Labs (DAL), located in Colorado Springs. There he designed and began building a new line of speakers, based upon their sibling Duntech models. These were the SC series mentioned here by others. The DAL speakers became highly successful for both home and studio applications. So I'm not surprised that your buyer found inappropriate crossover modifications to be the culprit for the poor performance. John's engineering prowess led to the crossover designs which were critical to the sonic success all of his models. When John's health began failing he sold DAL, but the continuation of the brand was not successful and the company closed after about a year. For those with adequate space and appropriate components I believe both Duntech and DAL models can provide great musical satisfaction, when found used in good condition.
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I have had a bunch of great speakers in the last 10 years including Vandersteen 5, 5a, Utopias, Electras, Magnepan 3.7i, Ariel 10t, Von Schweikert VR4 GenIII, B&W 802 D2, Tyler, Martin Logan Summit X, Martin Logan Expressions 13a, Reference 3a and more. The Dunlavy speakers were terrible. As it turns out the person that purchased them from me informed me that changes had been made to the crossovers. I suspected that but it was difficult to confirm because Dunlavy speakers of the same model can have different crossovers as they are voiced individually. The new owner has much experience in this area and was able to correct the issue. The speakers now sound very good. |
It appears from my research that these speakers do not have a common crossover. The crossovers were voiced to the pair, with that in mind I am going to remove but not disassemble the crossover and make a schematic of it. I am also going to get some speaker analysis software and measure their output. It was suggested to me that a simple resistor change in the Mid and Tweeter section might solve the issue. |
@petg60 I agree with you about running these with a good SS amp due to impedance dropping to around 3 Ohms. All of my auditions with these speakers were done with SS amps. I think "problem" is with the speaker, not his electronics up stream. I have visited Dunlavy Labs here in Colorado Springs many years ago. They are no longer in business and John Dunlavy has passed away. May he Rest in Peace! His speakers are used as references for mastering among many other applications. I finally settled with Thiel speakers and I could have easily accepted Dunlavy speakers too. Both use first-order x-overs and true to the source material. May not be a bad idea to contact Duntech and find out if they have any suggestions. |
@cerberus79 This is hard to believe, but I trust you have done your home work. Dunlavy speakers are anything but bright. May I ask you what kind of source material you used to find out these speakers sounded "bright"? Also, these are very efficient speakers with sensitivity of 92 dB. Have you tried this with a tube amp? Before you try to work on the crossover or any other parts, I would try to see if the problem remains with a tube amp. They have first order crossovers and drivers are designed to handle "leakage." If the drivers are changed, that may explain this problem. Also try moving the speakers to short-wall if these are currently placed along the long-wall. |
https://www.diyaudio.com/community/threads/dunlavy-sc-iv-schematics.325058/ This may prove helpful. Good luck. |
Your have experienced ears. The recording engineer who nudged me into this hobby had modified Duntech Sovereign's and me with little practical experience. He passed and years later I heard that general presentation again at a small shop with Dunlavy IV's. It wasn't about the scale of the big Sovereign's, I was told the time and phase is what I was glomming onto. Vandersteen's and Avalons get this. IMO these are well worth investigating. Sounds like monkeys under the hood or aged out components. I know nothing but this might be a good place to get some direction. Good luck with it. |
Especially unbalanced unless somebody messed up before. Check that tweeters are the originals and nothing is changed on the crossovers. Searching on internet and Agon you can find useful info about their crossovers and how they should look. Tone controls all the way back is not a good sign. |
