I am 90% of the way through building a Zaph ZRT: Zaph|Audio - ZRT - Revelator Tower
This speaker is a floorstanding two way ported design.
A friend built the cabinets for me out of baltic birch plywood, following the design on Zaph's site.
The braces/shelves have been ventilated, but the holes are not particularly large or numerous compared to most builds I have seen. The hole coverage area is perhaps 10%; see photo attached.
My question: Am I likely to have problems if I do not increase the number of holes in the braces?
I understand that the woofers have to see a certain air mass; would undersized holes in the braces change the effective volume/air mass? Would other problems arise?
The braces are not removable and it will be difficult to add more holes at this stage. Do I need to add more holes?
Thanks!
This speaker is a floorstanding two way ported design.
A friend built the cabinets for me out of baltic birch plywood, following the design on Zaph's site.
The braces/shelves have been ventilated, but the holes are not particularly large or numerous compared to most builds I have seen. The hole coverage area is perhaps 10%; see photo attached.
My question: Am I likely to have problems if I do not increase the number of holes in the braces?
I understand that the woofers have to see a certain air mass; would undersized holes in the braces change the effective volume/air mass? Would other problems arise?
The braces are not removable and it will be difficult to add more holes at this stage. Do I need to add more holes?
Thanks!
You need to lose around 50% of the shelf brace material to allow good airflow. A shelf brace combines a cross brace and horizontal brace so needs material around the perimeter as well as a + in the centre to join the opposite panels in each direction.
If you can't do that then get a jigsaw or small handsaw and join the dots so the complete middle is open.
The 18W8531 does move quite a bit of air.
If you can't do that then get a jigsaw or small handsaw and join the dots so the complete middle is open.
The 18W8531 does move quite a bit of air.
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Are there any other improvements which I can make to the cabinet at this stage?
Right now, it has a lining of acoustic foam, and nothing else. I will be stuffing the cabinet at the bottom, per the plans.
Is there anything else that I can do to improve the cabinet? Other lining materials?
Are there any other improvements which I can make to the cabinet at this stage?
Right now, it has a lining of acoustic foam, and nothing else. I will be stuffing the cabinet at the bottom, per the plans.
Is there anything else that I can do to improve the cabinet? Other lining materials?
The way it is now you run the risk of having the "tuning" of the spaces+the holes (think of them as ports) effecting how the driver behaves, they become individual little resonant cavities instead of one big one that's tuned the way you intended.
The area of the brace is around 437cm² so 50% cut out would give around 218cm². This looks OK as is larger than the SD of the 18W which is 150cm².
I think the minimum required would be a bit more than the SD of the driver. However, a single large hole would work differently to several quite small holes so put more holes in than you actually need to make up the area.
I hope I haven't confused things.
I think the minimum required would be a bit more than the SD of the driver. However, a single large hole would work differently to several quite small holes so put more holes in than you actually need to make up the area.
I hope I haven't confused things.
Thanks for the help everyone!
I managed to connect all the holes using a dremel, essentially making one very large hole in the middle of each brace. I wired everything up and have been listening for two days.
The speakers sound fairly good, with one major caveat: lack of bass.
They seem to roll off very sharply in the lower octaves (perhaps below 100 hz); bass instruments are almost nonexistent compared with the output from my Odin kit, which is of a similar size.
Any idea as to what could cause the bass to be rolling off so sharply?
I managed to connect all the holes using a dremel, essentially making one very large hole in the middle of each brace. I wired everything up and have been listening for two days.
The speakers sound fairly good, with one major caveat: lack of bass.
They seem to roll off very sharply in the lower octaves (perhaps below 100 hz); bass instruments are almost nonexistent compared with the output from my Odin kit, which is of a similar size.
Any idea as to what could cause the bass to be rolling off so sharply?
These should have bags of bass as I have tried the 18W8531 in a 37 litre BR. In that size the bass was too extended for the driver and lost a lot of control and my preference was for 28-32 litres.
Double check your crossover wiring and driver connections. You may want to try some shorter ports as the Fb as designed is very low at 30Hz which suited his room loading. I have tuned (Fb) this driver between 33Hz-38Hz depending on the design. If your port is easily changed you can try a few different lengths to see if that is the issue.
Woofer polarity measures the same on both speakers.
The crossovers were wired correctly as far as I could see. They were assembled by Madisound. The connections seem reasonably secure although they are through quick connects.
Is there any potential defect in the bass crossover that could cause a loss of low bass (e.g. if i somehow bridged or shorted something or if the wrong component was used)?
Could anything else be causing it? Too much padding in the box? (I used 1-2 layers of acoustic foam, per the design). I tried removing the stuffing from the bottom of the line and that did not have much of an effect.
The crossovers were wired correctly as far as I could see. They were assembled by Madisound. The connections seem reasonably secure although they are through quick connects.
Is there any potential defect in the bass crossover that could cause a loss of low bass (e.g. if i somehow bridged or shorted something or if the wrong component was used)?
Could anything else be causing it? Too much padding in the box? (I used 1-2 layers of acoustic foam, per the design). I tried removing the stuffing from the bottom of the line and that did not have much of an effect.
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I am watching this also Monroe as I have been saving my pennies for this design. I am hesitant to shell out $1000 for the parts if the performance is not there. I hope you solve the issue because my heart has been set on building these too. I built a trial version using Daytons rs180 as practice for the real towers and there is a huge bass improvement in 2 woofers over 1.
You mean that when you apply battery (+) on red input binding post, woofers move outwards for both cabinets?
Salas: yes, both woofers move outward when the battery is applied to the woofer terminals.
I have also tried listening to just one channel at a time to determine whether the response is similar from cabinet to cabinet or to determine whether there might be interference. They sound the same.
I have tried listening through two different amplifiers (a Marantz solid state amp rated at 25 watts in class A and twice that or so in AB, and a Consonance push pull el34 tube amp at ~40 watts) and have found that the speakers exhibit a similar lack of bass response with both amps.
I don't know if it's of any significance, but strangely, with the tube amp, the sound is clearer when the speakers are plugged into the 4 ohm tap than the 8 ohm tap (the ZRTs are 8 ohm speakers I believe). There is mild but audible distortion on the 8 ohm tap which prompted me to try the 4 ohm. I only ever ran the amp with the 4 ohm tap for the Odins.
I have done some cursory measurements using a built in laptop mic and a sweep tone and found that levels roll off sharply below 100 Hz - at least on the chart. I don't think that these measurements are particularly meaningful given the low quality uncalibrated microphone: the measurement program shows a similar rolloff for the Odins even though they have audibly louder bass.
I have also tried listening to just one channel at a time to determine whether the response is similar from cabinet to cabinet or to determine whether there might be interference. They sound the same.
I have tried listening through two different amplifiers (a Marantz solid state amp rated at 25 watts in class A and twice that or so in AB, and a Consonance push pull el34 tube amp at ~40 watts) and have found that the speakers exhibit a similar lack of bass response with both amps.
I don't know if it's of any significance, but strangely, with the tube amp, the sound is clearer when the speakers are plugged into the 4 ohm tap than the 8 ohm tap (the ZRTs are 8 ohm speakers I believe). There is mild but audible distortion on the 8 ohm tap which prompted me to try the 4 ohm. I only ever ran the amp with the 4 ohm tap for the Odins.
I have done some cursory measurements using a built in laptop mic and a sweep tone and found that levels roll off sharply below 100 Hz - at least on the chart. I don't think that these measurements are particularly meaningful given the low quality uncalibrated microphone: the measurement program shows a similar rolloff for the Odins even though they have audibly louder bass.
Voices sound ok. They might be a little bit heavy on the high side - alternately it may just seem that way because of the lack of low bass. It may also be that I am used to the way they sound with the Odins, which i believe have a little bit of a dip in the response near the crossover point.
For the crossovers on the ZRT I went with the 2.7 mH 'upgrade' coil from Madisound (14 AWG copper foil), and I believe that they put the right value on.
I note that the resistance of the copper foil coil is .370, compared with .168 for the steel laminate that is specified in the regular crossover and in Zaph's design. Could that be making a difference?
For the crossovers on the ZRT I went with the 2.7 mH 'upgrade' coil from Madisound (14 AWG copper foil), and I believe that they put the right value on.
I note that the resistance of the copper foil coil is .370, compared with .168 for the steel laminate that is specified in the regular crossover and in Zaph's design. Could that be making a difference?
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