so.. i built another cabinet for the zaph zrt 2-way kit i bought, the first one being a sealed 20L design which had anemic bass (rolled off too much <100hz). The one i just built is a 38L cabinet and i followed Zaph's enclosure plans dimensions very closely, only difference being in the bracing placement.
Well, this time round there is more bass but definitely not what i expected from a vented 18w-8531 floorstander design. I'm really clueless as to what's wrong, though i'm sure you guys will be able to enlighten me 😀
I went with the default 30Hz tuning recommended, and according to the tuning frequency response graph
, it should be at least +/- 3 dB down to 50Hz... but somehow i'm not hearing it. Woofer is verified to be in phase. Test tones revealed that the speaker sounds pretty flat down to 80Hz but starts to roll off until output at 40Hz is almost non-existent. I have heard more than a handful of ported bookshelves with < 7" woofer that has more meaningful output at 40Hz than the speaker i just built. I can't help but think i did something wrong since the 18w-8531 is so highly raved about everywhere 😕
I clamped the front baffle on while adjusting the amount of stuffing.
. With this method, there didn't seem to have much, if any, air leaks though i'm not sure if the amount of bass should be affected by that much?
After trying out different amounts of rockwool and acousta-stuf stuffing, it didn't seem to make much of a difference. If it's not the woofers that are faulty, i'm wondering if it's a bracing/port problem.
Circular cut-outs in 25mm bracing are 6.5" diameter. The only problem i can think of is how close the bracing is to the port, so there's not much air clearance near the port. I'm not sure if it affects anything. But even so, should the bass be affected by this much?
The biggest questions on my mind are:
1) Will the placement of braces relative to the port affect bass extension and output so much?
2) Will excessive stuffing/fill amount alter and shape bass response drastically?
Any suggestions are really appreciated, thank you!
Well, this time round there is more bass but definitely not what i expected from a vented 18w-8531 floorstander design. I'm really clueless as to what's wrong, though i'm sure you guys will be able to enlighten me 😀
I went with the default 30Hz tuning recommended, and according to the tuning frequency response graph
I clamped the front baffle on while adjusting the amount of stuffing.
After trying out different amounts of rockwool and acousta-stuf stuffing, it didn't seem to make much of a difference. If it's not the woofers that are faulty, i'm wondering if it's a bracing/port problem.
Circular cut-outs in 25mm bracing are 6.5" diameter. The only problem i can think of is how close the bracing is to the port, so there's not much air clearance near the port. I'm not sure if it affects anything. But even so, should the bass be affected by this much?
The biggest questions on my mind are:
1) Will the placement of braces relative to the port affect bass extension and output so much?
2) Will excessive stuffing/fill amount alter and shape bass response drastically?
Any suggestions are really appreciated, thank you!
Yea, it is. There is more bass with this design now, for sure. But really not i expect from a cabinet almost twice the internal volume. Any ideas what could be the problem?
Well, i asked because when we were talking about fixing your crossover, you never did say what method you used to fix it.
If you fixed it in the manner that you mentioned (snipping that jumper) then you have a series capacitor on your woofer, which would make it sound more like a midrange.
If you didn't snip the jumper and instead just hooked the woofer up to the other terminal, then it should be performing as it should.
If you fixed it in the manner that you mentioned (snipping that jumper) then you have a series capacitor on your woofer, which would make it sound more like a midrange.
If you didn't snip the jumper and instead just hooked the woofer up to the other terminal, then it should be performing as it should.
You'd need a very anaemic amplifier to cause bass issues with steady state test tones @ normal listening levels. My first guess would be the room, have you tried positioning the loudspeaker in a different place, or alternatively, you leave the loudspeaker where it is then you walk around into different locations? If you do this, then the bass at a fixed frequency will change considerably in level as you walk into and out of peaks/nulls created by room modes. It's possible you're in a very bad spot or have awful room acoustics. As a test, set the loudspeaker to produce something like 50hz and then walk around the room. If you're in a null then walking into other areas of the room should produce bass that is considerably louder.
If you want to rule out the crossover as the cause then remove it altogether and try the test tones with the 18W full range. The crossover should have minimal effect on the bass below 200hz, so removing it should ideally do nothing.
If you want to rule out the crossover as the cause then remove it altogether and try the test tones with the 18W full range. The crossover should have minimal effect on the bass below 200hz, so removing it should ideally do nothing.
You're getting too much mids. You'll need to shape the response to boost the bass, the mid-bass in particular (about 100Hz). A crossover is simply to determine the stop band of the woofer and the tweeter. Does nothing for the bass.
When the baffle is on, how close is the port to the lining? If the port is obstructed, you'll lose bass.
Are you sure the rest of the cabinet is sealed?
Are you able to provide impedance measurements? An impedance curve would show up what's happening.
Are you sure the rest of the cabinet is sealed?
Are you able to provide impedance measurements? An impedance curve would show up what's happening.
Hi cersepn,
I suspect your simulation is based on a half space response, not full space and will therefore not show the normal -6dB drop in level at low frequencies compared to mid/high frequencies. This drop in level at low frequencies is normally compensated for in the XO and is commonly described as the baffle step compensation or BSC.
Also, check the free air space around the internal end of the port (as chris661 suggests) since this can significantly degrade the port output.
Regards
Peter
I suspect your simulation is based on a half space response, not full space and will therefore not show the normal -6dB drop in level at low frequencies compared to mid/high frequencies. This drop in level at low frequencies is normally compensated for in the XO and is commonly described as the baffle step compensation or BSC.
Also, check the free air space around the internal end of the port (as chris661 suggests) since this can significantly degrade the port output.
Regards
Peter
Possibly, I'm using a nakamichi IA-1Z which is on loan. It's a multichannel AVR. There were some suggestions that it might the receiver set to "small speakers" and I thought that might be the answer, but I dont see any buttons on the int amp to change such a setting hmm
DrDyna;2684391 If you didn't snip the jumper and instead just hooked the woofer up to the other terminal said:
This could definitely cause the issue you've having at the moment, try seeing if it's got some sort of button for 'hifi direct' or something that would bypass everything. The nakamichi looks quite old though, I don't think the older products had so many options for sub integration then they do now.
If this is the case then it's doubtful that it's the room acoustics. Unless the previous speakers you've used had floor loaded bass drivers or something. But if we're comparing similar 2 ways with the bass unit positioned somewhere around the same height from off the floor, then it's probably not the room. Note that having bass boom isn't a reason for selecting a reduced BSC option loudspeaker. As you can see from Zaphs graphs of the transfer function of the crossover, the BSC only affects stuff at 200hz +. The reduced BSC option is for when you need to place the loudspeaker close to the rear wall etc.
Exactly, if you're comparing bass to bass it wont change anything. The low pass filter on the mid/bass only starts to adjust the mid level around 200hz with respect to baffle step. So with or without the crossover what's happening below 200hz should be exactly the same.
An unscientific way to see if the port is doing anything is to plug it with a sock 😛 Does plugging it reduce the bass? Or rather Zaph shows that the port should be tuned to around 30hz, this means the air speed in the port should be at its highest around 30hz. Whack a 30hz tone through the loudspeaker and see if lots of air seems to be moving in and out of the port. In an old ported pair of loudspeakers I had the curtains would flap from the air in the ports moving😛 If you don't seem to get anything, even if you turn it up then perhaps the ports are being a problem.
One other thing, ported loudspeakers 'unload' below the tuning frequency. In the case of the ZRT this should be around 30hz. If you play a 20hz tone through the ZRT the 18w should flap about all over the place in comparison to if you played a 35hz tone through it. If there is a sneaky high pass working somewhere in the nakamichi it will most certainly limit the amount of bass getting through at 20hz, so perhaps try that. Play a 35hz tone, see how much the cone moves, then try a 20 or even a 10hz tone, the cone should move considerably more. If it doesn't then there's a strong possibility that there's a high pass at work.
I think a BR box should be 100% airtight, apart from the porting ofcourse
a closed box is less critical
from specs, Fs28hz/0.36Qts, it ought to play fine bass
ofcourse somewhat restricted by its relaively small size
if you want FAT bass, try remove the port tube
or try make it shorter
maybe also stuff the bottom very hard
a closed box is less critical
from specs, Fs28hz/0.36Qts, it ought to play fine bass
ofcourse somewhat restricted by its relaively small size
if you want FAT bass, try remove the port tube
or try make it shorter
maybe also stuff the bottom very hard
so.. i built another cabinet for the zaph zrt 2-way kit i bought, the first one being a sealed 20L design which had anemic bass (rolled off too much <100hz). The one i just built is a 38L cabinet and i followed Zaph's enclosure plans dimensions very closely, only difference being in the bracing placement.
Well, this time round there is more bass but definitely not what i expected from a vented 18w-8531 floorstander design. I'm really clueless as to what's wrong, though i'm sure you guys will be able to enlighten me 😀
I went with the default 30Hz tuning recommended, and according to the tuning frequency response graph, it should be at least +/- 3 dB down to 50Hz... but somehow i'm not hearing it. Woofer is verified to be in phase. Test tones revealed that the speaker sounds pretty flat down to 80Hz but starts to roll off until output at 40Hz is almost non-existent. I have heard more than a handful of ported bookshelves with < 7" woofer that has more meaningful output at 40Hz than the speaker i just built. I can't help but think i did something wrong since the 18w-8531 is so highly raved about everywhere 😕
I clamped the front baffle on while adjusting the amount of stuffing.
. With this method, there didn't seem to have much, if any, air leaks though i'm not sure if the amount of bass should be affected by that much?
After trying out different amounts of rockwool and acousta-stuf stuffing, it didn't seem to make much of a difference. If it's not the woofers that are faulty, i'm wondering if it's a bracing/port problem.
Circular cut-outs in 25mm bracing are 6.5" diameter. The only problem i can think of is how close the bracing is to the port, so there's not much air clearance near the port. I'm not sure if it affects anything. But even so, should the bass be affected by this much?
The biggest questions on my mind are:
1) Will the placement of braces relative to the port affect bass extension and output so much?
2) Will excessive stuffing/fill amount alter and shape bass response drastically?
Any suggestions are really appreciated, thank you!
Firstly you seem to have all the holes in your bracing in a straight line, you should offset these in the future, also move the port to the rear, if that's an 8 inch use an 3 inch port , your port area looks pretty small...
It is possible that this speaker was designed for amplifiers with significant source impedance and this AVR amp undoubtedly acts like a voltage source. Try inserting some resistance in series with the output - 0.47 to 1 ohm should suffice, IIRC this will have the effect of increasing woofer QTS..
Another thing to consider is whether or not BSC is required based on cabinet geometry.. Google Edge...
All assuming that everything else is correct.. 😀
Another thing to consider is whether or not BSC is required based on cabinet geometry.. Google Edge...
All assuming that everything else is correct.. 😀
I would seriously bet that the speaker is doing what it was designed to.
However, you hear a loss of bass for a number of reasons.
1. As mentioned before, you will get a baffle step loss, but the baffle is pretty narrow, so I suspect that contribution is not large. This is the transition point from half-space to full-space that gives you up to a 6 dB loss in on-axis response. In your box I would estimate the F3 point is about 500 Hz or so.
2. No doubt the room is sucking out the bass, too. Try moving the speaker around the room to see if it performs differently or even in a different room.
One trick is to locate the speaker right at the listening position and walk around the room and hunt for the best sound. Now trade positions by moving the speaker to that spot and listen at the listening position.
You can verify the design by testing, too, but to get reliable frequency responses down into the bass region requires placing the speaker in a very large room or atrium.
The cabinet should be way off the ground or floor with the ceiling just as far above it. Few people have a room so large, so you are left with the difficult task of taking near field plots of the woofer and its port and splicing them together with the far field plot to get a relatively accurate picture of the total response.
The best solution for anemic bass in a bad room is multiple subs to override the nodes and even out the room response.
3. lastly, the easy way to determine port tuning is with impedance. A simple way to do this is with a simple AC voltmeter and a signal generator (PC based or whatever). Just take a voltage reading every 5 or 10 Hz to get a rough graph of the impedance about the suspected port tuning. You can add more data points once you have a rough idea where the twin peaks are in voltage. You do not need a loud SPL to do this. Just enough wattage to be audible. In 5 minutes you will have enough data to make a graph.
The point equidistant between those maximum points should be a voltage minims. That is the tuned port frequency.
Your graph should look like this where the orange line is the impedance:
You don't even need to graph it, just find the lowest voltage point between the two peaks an note the frequency. QED.
However, you hear a loss of bass for a number of reasons.
1. As mentioned before, you will get a baffle step loss, but the baffle is pretty narrow, so I suspect that contribution is not large. This is the transition point from half-space to full-space that gives you up to a 6 dB loss in on-axis response. In your box I would estimate the F3 point is about 500 Hz or so.
2. No doubt the room is sucking out the bass, too. Try moving the speaker around the room to see if it performs differently or even in a different room.
One trick is to locate the speaker right at the listening position and walk around the room and hunt for the best sound. Now trade positions by moving the speaker to that spot and listen at the listening position.
You can verify the design by testing, too, but to get reliable frequency responses down into the bass region requires placing the speaker in a very large room or atrium.
The cabinet should be way off the ground or floor with the ceiling just as far above it. Few people have a room so large, so you are left with the difficult task of taking near field plots of the woofer and its port and splicing them together with the far field plot to get a relatively accurate picture of the total response.
The best solution for anemic bass in a bad room is multiple subs to override the nodes and even out the room response.
3. lastly, the easy way to determine port tuning is with impedance. A simple way to do this is with a simple AC voltmeter and a signal generator (PC based or whatever). Just take a voltage reading every 5 or 10 Hz to get a rough graph of the impedance about the suspected port tuning. You can add more data points once you have a rough idea where the twin peaks are in voltage. You do not need a loud SPL to do this. Just enough wattage to be audible. In 5 minutes you will have enough data to make a graph.
The point equidistant between those maximum points should be a voltage minims. That is the tuned port frequency.
Your graph should look like this where the orange line is the impedance:
An externally hosted image should be here but it was not working when we last tested it.
You don't even need to graph it, just find the lowest voltage point between the two peaks an note the frequency. QED.
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You all seem to be forgetting that this is one of Zaph's designs. It is designed correctly and is not designed for an amplifier with a high source impedance.
The driver is a 6.5", that port should be fine unless you want to try and specifically make it chuff.
The driver is a 6.5", that port should be fine unless you want to try and specifically make it chuff.
Narrow it down (Divide and Conquer)
"Test tones revealed that the speaker sounds pretty flat down to 80Hz but starts to roll off until output at 40Hz is almost non-existent. I have heard more than a handful of ported bookshelves with < 7" woofer that has more meaningful output at 40Hz than the speaker i just built"
You must try a different amp or figure out your amp's settings 100% before you know it is not the source of the problem.
Not super easy to find a user manual, but the premise that you may be feeding the speakers only >80 hz is very plausible. See review TechnoFILE Looks at Nakamichi's IA-Tz amplifier for evidence this hardware has much capability for an older beast and 80hz is the SW cutoff on it.
My .02:
1. Rule out the amplifier, then
2. rule out the crossover, then
3. rule out the driver, then
4. rule out the box
Anyway, I am sure you can troubleshoot this if you don't skip steps in your process.
"Test tones revealed that the speaker sounds pretty flat down to 80Hz but starts to roll off until output at 40Hz is almost non-existent. I have heard more than a handful of ported bookshelves with < 7" woofer that has more meaningful output at 40Hz than the speaker i just built"
You must try a different amp or figure out your amp's settings 100% before you know it is not the source of the problem.
Not super easy to find a user manual, but the premise that you may be feeding the speakers only >80 hz is very plausible. See review TechnoFILE Looks at Nakamichi's IA-Tz amplifier for evidence this hardware has much capability for an older beast and 80hz is the SW cutoff on it.
My .02:
1. Rule out the amplifier, then
2. rule out the crossover, then
3. rule out the driver, then
4. rule out the box
Anyway, I am sure you can troubleshoot this if you don't skip steps in your process.
Seems like it might just have these options. Can't believe i didn't notice them until now
An externally hosted image should be here but it was not working when we last tested it.
I tried playing a 30Hz tone and there's close to nothing at all. Nothing coming out from the ports and very, very little air. That was why i felt it was the port with the problem. But now i think it's either the XO or amp. Will mess around with the amp settings and see how it goes.
Thanks for your advice, it is really helpful.
When i get back today i shall try two things:
1) Meddle with the amp settings
2) If it's not the amp then i will run the woofers full range (will that damage it, i hope not?). If the bass comes back then i know i have the XO wired up wrongly.
Thank you all for the help!
no, only your ears 😉
accidental short in the xo can happen
but ought to sound really strange
I remember once I worked with 6" woofer
it was quite a dilemma when I preferred it with port tube removed 😱not good😀
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