Burn in took care of "hotness" and harshness in the sound it seems. Mids are now very smooth, soundstage is wide, and voices are a joy to listen to. I reverted all resistor changes back to original values, so entire XO is as on zaph's site. It's just so disappointing to hear such big speaker with two very expensive revelator drivers perform so poorly below 100Hz. If I didn't have ZD5 next to it, probably would not have even noticed this deficiency. Measurements also confirm this. Can't blame it on the room either, it's rather small and the same ZD5 is residing in. I tried taking out some stuff at the bottom, no significant changes in bass response below 100Hz. I have very little hope any change in XO can fix something that woofers simply don't produce. You can see how vent struggles to push up something around 30Hz that just isn't there. I will leave it to play for another week, but have little faith that additional burn in will fix this.
I still have couple of weeks before I need to make a decision to just scrap the box and return all the components back to vendor.
I still have couple of weeks before I need to make a decision to just scrap the box and return all the components back to vendor.
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Not hot then.
Do you have impedance graphs that show how the port tuning effects the impedance? Maybe that will give an extra clue as to what is happening to the bass? Have you tried to measure what is coming out of the bass port. Have you checked the driver impedances ?
I ask as it is not unknown to get a 4 ohm driver and an eight ohm driver by mistake? It shouldn't happen with expensive drivers from a reputable supplier, but it can.
Do you have impedance graphs that show how the port tuning effects the impedance? Maybe that will give an extra clue as to what is happening to the bass? Have you tried to measure what is coming out of the bass port. Have you checked the driver impedances ?
I ask as it is not unknown to get a 4 ohm driver and an eight ohm driver by mistake? It shouldn't happen with expensive drivers from a reputable supplier, but it can.
I have installed the port on only one of them out of desperation. The other one is still sealed 38L enclosure according to specs. I cannot hear any difference in bass between the two since the port tuning is at 30Hz where nothing is being played anyway. ScanSpeak box says it's 8ohm, but that kind of mistake would probably mess up everything and not just the lower end. Everything above 100Hz plays perfectly fine.
I'd like to make this suggestion again.
Disconnect the woofers from the crossover and drive them individually, directly from an amp. See if there is any info below 40Hz or so (with them both mounted in your speaker box). You would have to have a very incorrect box to not get at least this low. It will sound odd but just listen to the bass.
If you have good bass then look at the crossover. May just be a balance of things but may also be out of spec components.
Good luck!
Disconnect the woofers from the crossover and drive them individually, directly from an amp. See if there is any info below 40Hz or so (with them both mounted in your speaker box). You would have to have a very incorrect box to not get at least this low. It will sound odd but just listen to the bass.
If you have good bass then look at the crossover. May just be a balance of things but may also be out of spec components.
Good luck!
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Here is an in-shop test of my ZRT-2.0 woofer done just now. Direct to amp in 35L box, vented and closed for comparison. About 1.2m from back wall so not too much room gain. Microphone distance about 1.4m.
<edit> These were built in 2014 btw.
<edit> In your case there may be some passive diaphragm effect from the unpowered woofer. I do not know how much though.
<edit> These were built in 2014 btw.
<edit> In your case there may be some passive diaphragm effect from the unpowered woofer. I do not know how much though.
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Thanks for taking the time to do this. Yours seem to perform much better below 100Hz. There is still some faint hope that this low end develops last after prolonged play time. My ZD5 has also been built long time ago. I am leaving them playing for next couple of weeks and then I will have to make a decision. I am also waiting for response from Scan Speak.
I would first make sure the driver itself is within tolerances by measuring T/S parameters of every unit then work on analyzing enclosure related issues, then wiring/crossover.
Box and crossover are made exactly to specs, and I'd like to avoid investigating anything related to the design. I have limited expertise and measurement equipment, and that's the reason I went for what was supposed to be a proven design. All I can conclude so far is that drivers perform less than optimal in sub-100Hz region with or without crossover, and that's already been more/less proven with measurements above.
I will try to setup something for T/S measurement.
Honestly, If I didn't have ZD5 right next to them, I probably wouldn't even notice low-end deficiency.
I will try to setup something for T/S measurement.
Honestly, If I didn't have ZD5 right next to them, I probably wouldn't even notice low-end deficiency.
Image from Zaph's website (ZRT2.5); "Near field bass response, sealed enclosure, no crossover".
http://www.zaphaudio.com/ZRT-2.5way-measured-FR-nearfield-sealed.gif
Graph is near field but your results should be similar. I would agree to testing for T/S parameters.
http://www.zaphaudio.com/ZRT-2.5way-measured-FR-nearfield-sealed.gif
Graph is near field but your results should be similar. I would agree to testing for T/S parameters.
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I started more intensive burn-in at 14 Hz with both boxes open to allow for more cone excursion. Maybe sealed boxes need more time to loosen up due to restricted cone movement? Also, there is not that much material which has low end frequencies, so just wanted to speed up things in case this is the culprit.
This is the reply from Soundimports. If I understood correctly, ZRT2.5 in 38L is expected to have less lower end than ZD5??? I guess I better start packing the drivers, as ZRT2.5 turns out to be the downgrade from ZD5...
It's important to verify the tuning with an impedance plot like others have said. Port tuning isn't as predictable as simulations lead you to believe (at least in my experience) and you don't want it too low. Usually my speakers end up tuned lower than predicted and I need to shorted the port length.
I just went through this with an 18W8531G00 in 33L. Here are my measurements, lengths include the full flair length.
I just ported both ZRT boxes - ZD5 still running circles around them. If I close my eyes, I could swear the extra low end comes from ZRT, but it's not! Just did a proper A/B listen to both, and EVERYTHING is slightly better in ZD5 - a true reference to beat. Even the XT25 blows the Illuminator tweeter out of the water, so no point in beating a dead horse anymore... Anyone needs a ZRT box to play with?🙂 The rest is going back to where it came from. Trust me, if you never heard ZD5, ZRT would make you very happy 🙂
I shortened ports from 10cm to 5.5cm, 4.6cm internal diameter, which should be tuning at around 37Hz - still no significant change.