I do not know if these were a kit mod or a ‘factory’ mod and don’t know much about what transpired back then.
Got these 18 months ago in tired shape and have been avoiding working on them.
What they were is Dahlquist DQ-10 speakers, non-mirror imaged, film caps with replacement Audax tweeters and JVC replacement supertweeters. The crossovers were also modded with double bypass caps seemingly all around. A 1.0 and 0.1μF added to most caps. The 80μF ‘lytic for the midwoofer still original.
As received, these had dirty original grille cloth, a cracked chunk of hardboard for the dome midrange on one speaker and missing fuse holder caps. I pulled the midrange tweeter superstructure to fix the hardboard. Removed the grille cloth and shelved the project for other work because I knew I was going to mirror-image this pair and this repaired structure would be on the other side of the cabinet. Did my homework on these and found . There is not a lot about this upgrade because it was before the internet era.
Tomek is very interested in knowing how they sound so I finally agreed to work on them in Feb. Finished them for listening, not cosmetics, replacing the ‘lytic in the one I was mirroring.
Hooked em up and they are bright. Turned the tweeter control down and invited the boys over for a listen. and his copilot Terry dropped by for this listening, comparing my DQ-10s restored just like the pair I sold to Terry a couple years ago and these Randall Research DQ-10s. We also were going to audition some MM cartridges as Mark is loving his micro ridge retipped XSV-3000 Pickering. Has the power sound for good rock and roll. More on that in TT forum later.
Back to our day of listening. The RRs sounded bad with blurred sound and less bass. They made my 10s sound special. Talked about the differences and moved to the cartridges. The guys said the rig sounds really good, of course we were playing one of Mark’s favorite female vocalists at the time but it is compromised by the offset nature of the two pair of speakers being switched. They have heard double Dahlquist here previously.
The next couple days I was thinking about what F1nut said about bypass caps in the crossover, artifacts and was going to pm him, but he has left ak. I was even thinking that my 10s with polypropylene caps vs Mylar might have an influence. Still thinking about the issues and less bass hit me wrt phase. OK I screwed up and got that wrong. Here is the Crown OC-150a switch box I rarely use but perfect for this chore.
Here is the crossover in the regular DQ-10s. That is a film cap in red on the far end replacing the 80μF ‘lytic cap.
Now that the speakers, all 4 of them are in phase, it sounds good in here. Either pair has clear sound and differences are mostly top end. I need to listen more. Folks hate the Motorola piezo tweeter in the 10s because of reputation, not sound quality in this speaker. Since this horn tweeter will reproduce from a couple thousand to over 20 thousand and it can handle a lot of power it is used in lots of sound reinforcement speakers that just don’t sound that good…bad reputation. In the DQ-10 it crosses over at 12,000Hz and doesn’t screw up the sound as it adds sparkle. But wouldn’t a ribbon tweeter be better? And the dome tweeter can be upgraded, too. Enter the Randal Research mods.
I can switch pairs and the sound is similar, not like Sunday when the RRs were out of phase. I was surprised to hear the damage to the clarity by this simple issue. I had not heard that kind of sonic degradation from OOP before. And I know I’ve listened to speakers wired wrong for short periods of time. Interesting
SpongeSound