I've had the AC130MKII for a couple of years and finally got around to trying to do something with it, so I started working on a ported, 2-way system for my youngest sister's 30th B-Day next year. She has a small apartment with a 13' x 9' living room so a small tower would fit her needs nicely.
I've got the AC130MKII in a 14L test box (7" x 9.5" x 24") tuned to 50Hz for an F3 of 52Hz, teamed up with the Morel CAT408 1-1/8" dome tweeter and crossed over at 2.3kHz. The x-overs are 3d-order electrical with a good measure of eq to smooth out the bumpy response of these two drivers. There's still a bump at 800Hz which was helped by adding stuffing to the cabinet and lots of room/floor bounce ripples at low frequencies which go away when I take a nearfiled measurement.
The sound is very clear and natural for vocals, the bass is firm but slightly mild and the trebble is a touch on the bright side, which I hope to tone down a notch once the cloth grill is added.
Has anyone else used either of these two drivers? I'd be interested in seeing what kind of in-box frequency response you measured and what you used for the x-over for either driver if you're willing to share.
I've had the AC130MKII for a couple of years and finally got around to trying to do something with it, so I started working on a ported, 2-way system for my youngest sister's 30th B-Day next year. She has a small apartment with a 13' x 9' living room so a small tower would fit her needs nicely.
I've got the AC130MKII in a 14L test box (7" x 9.5" x 24") tuned to 50Hz for an F3 of 52Hz, teamed up with the Morel CAT408 1-1/8" dome tweeter and crossed over at 2.3kHz. The x-overs are 3d-order electrical with a good measure of eq to smooth out the bumpy response of these two drivers. There's still a bump at 800Hz which was helped by adding stuffing to the cabinet and lots of room/floor bounce ripples at low frequencies which go away when I take a nearfiled measurement.
The sound is very clear and natural for vocals, the bass is firm but slightly mild and the trebble is a touch on the bright side, which I hope to tone down a notch once the cloth grill is added.
Has anyone else used either of these two drivers? I'd be interested in seeing what kind of in-box frequency response you measured and what you used for the x-over for either driver if you're willing to share.
Any other suggestions are wellcome.
Thanks,
Louis
I have MDT40's, and they are xover'd about 1700 Hz, but they get a bit picky with the knee-treatment at rolloff. Otherwise they sound pretty good that low with no indication of strain. Your 408's are essentially the same tweeter with a round face.
Later,
Wolf
"Wolf, you shall now be known as "King of the Zip ties." -Pete00t "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith "We don't just make a crossover, we make a statement!" - Lawrence Fishburne for Cadillac
I have MDT40's, and they are xover'd about 1700 Hz, but they get a bit picky with the knee-treatment at rolloff. Otherwise they sound pretty good that low with no indication of strain. Your 408's are essentially the same tweeter with a round face.
Later,
Wolf
I played with crossing the CAT408 lower but found it sounding just a touch gritty unless the attenuation in the 1 to 1.5kHz range was greater than 20dB. I took some single tone HD distortion measurements (see attachment) and they seemed to correlate with what I was hearing so I opted for the higher XO point. Its probably a minor point and barely audible with both drivers playing simultaneously, due to masking.
I've had the AC130MKII for a couple of years and finally got around to trying to do something with it, so I started working on a ported, 2-way system for my youngest sister's 30th B-Day next year. She has a small apartment with a 13' x 9' living room so a small tower would fit her needs nicely.
I've got the AC130MKII in a 14L test box (7" x 9.5" x 24") tuned to 50Hz for an F3 of 52Hz, teamed up with the Morel CAT408 1-1/8" dome tweeter and crossed over at 2.3kHz. The x-overs are 3d-order electrical with a good measure of eq to smooth out the bumpy response of these two drivers. There's still a bump at 800Hz which was helped by adding stuffing to the cabinet and lots of room/floor bounce ripples at low frequencies which go away when I take a nearfiled measurement.
The sound is very clear and natural for vocals, the bass is firm but slightly mild and the trebble is a touch on the bright side, which I hope to tone down a notch once the cloth grill is added.
Has anyone else used either of these two drivers? I'd be interested in seeing what kind of in-box frequency response you measured and what you used for the x-over for either driver if you're willing to share.
Any other suggestions are wellcome.
Thanks,
Louis
If you are using the published specs for the AC130MKII they are incorrect and the sensitivity is a few dB lower so that is why your bass might be "mild". I really need to get FR of this driver since the T/S specs are so far off. Below is what I got using the WT3 on a few of the drivers, I got 2 of them about 2-3 years ago and a few just recently and they all measure very close to the same.
If you are using the published specs for the AC130MKII they are incorrect and the sensitivity is a few dB lower so that is why your bass might be "mild". I really need to get FR of this driver since the T/S specs are so far off. Below is what I got using the WT3 on a few of the drivers, I got 2 of them about 2-3 years ago and a few just recently and they all measure very close to the same.
The TS parameters for my four units measure fairly close to yours but the Vas I'm getting is closer to 14L using the box method. I also bought these about 2 years ago so I am not sure what would account for the difference.
Also, the freq. resp. in my 7" x 9.5' x 24", well stuffed, test box is the blue curve below; it is 1/3 octave smoothed. It looks pretty bad hence my overly complex x-over.
Finally bought a new WT3; zapped my old one by accidentally hooking it up to an xo with an amp hooked up.
So would you guys recommend a 4 ohm capable amp for this one or can most 8 ohm amps handle this kind of impedance; dips down to about 3.7 ohms and 10 degrees capacitive at 1kHz?
I connected the speaker to my Furman SP20A Amp, configured for bridged mode, and its not having any problems driving it at any volume. This Amp is rated for 8 ohm loads in bridged mode and when I've tried to use it with 4 ohm speakers in the past, it would start to intermittently shut down as the volume was increased.
Finally bought a new WT3; zapped my old one by accidentally hooking it up to an xo with an amp hooked up.
So would you guys recommend a 4 ohm capable amp for this one or can most 8 ohm amps handle this kind of impedance; dips down to about 3.7 ohms and 10 degrees capacitive at 1kHz?
Louis
Based on all of the two way speaker designs that I've done, it is very odd to see an impedance dip near the crossover point although most of my two way crossovers are much less complex in general. I think that the culprit in your case is the use of a series notch filter within the passband of the woofer and I think that this is pulling the impedance down due to the shunt to ground within a region that the amplifier isn't isolated by another series impedance (as is the case when using a series notch filter in the stopband since the components between the filter and the amp increase the impedance seen by the amp).
Personally I think that I would find it very frustrating to try to tweak a crossover as complex as yours by ear (there are just too many variables to work with). Now I know that not everybody tweaks crossovers the same way that I do but it seems like you are relying more on response plots to adjust your crossover than your ears but perhaps the drivers you are working with are very tough to work with when it comes to reaching a neutral presentation. I guess that if I was working on your crossover, I would simplify it a bit and then start tweaking by ear because it seems possible that some issues that you are mentioning could be due to tonal balance as others have suggested.
Based on all of the two way speaker designs that I've done, it is very odd to see an impedance dip near the crossover point although most of my two way crossovers are much less complex in general. I think that the culprit in your case is the use of a series notch filter within the passband of the woofer and I think that this is pulling the impedance down due to the shunt to ground within a region that the amplifier isn't isolated by another series impedance (as is the case when using a series notch filter in the stopband since the components between the filter and the amp increase the impedance seen by the amp).
Personally I think that I would find it very frustrating to try to tweak a crossover as complex as yours by ear (there are just too many variables to work with). Now I know that not everybody tweaks crossovers the same way that I do but it seems like you are relying more on response plots to adjust your crossover than your ears but perhaps the drivers you are working with are very tough to work with when it comes to reaching a neutral presentation. I guess that if I was working on your crossover, I would simplify it a bit and then start tweaking by ear because it seems possible that some issues that you are mentioning could be due to tonal balance as others have suggested.
Roman,
Actually I do both response measurements and listening; probably more of the latter. I listen to about 30 songs that I am now very familiar with on a variety of speakers, and if I am not happy with the sound, then I try to tweak the measured response to dial the measured spectrum up or down in the offending frequency segment which may also involve looking at what is going on in the x-over stopband response and the distortion. Then I do an A/B comparison, and if the changes hold up, then I widen my music selection and listen some more. On the x-over above, I spent about 3 months doing this; I am not happy with the complexity, but I am pleased with the sound.
I could probably go back and try to implement that series notch using a different topology.
Actually I do both response measurements and listening; probably more of the latter. I listen to about 30 songs that I am now very familiar with on a variety of speakers, and if I am not happy with the sound, then I try to tweak the measured response to dial the measured spectrum up or down in the offending frequency segment which may also involve looking at what is going on in the x-over stopband response and the distortion. Then I do an A/B comparison, and if the changes hold up, then I widen my music selection and listen some more. On the x-over above, I spent about 3 months doing this; I am not happy with the complexity, but I am pleased with the sound.
I could probably go back and try to implement that series notch using a different topology.
Louis
I apologize for the criticism. Your procedure seems very similar to mine when it comes to crossover tweaking. I guess that I've always compromised a bit sooner with my crossover designs while you seem to go a bit deeper at taming each part of the response, but in the end it is the sound that matters (as you know). However, I don't hold the belief that too many crossover parts degrade the sound like some who strive for minimalist crossover approaches do (although I do look at the budget in terms of crossover parts cost relative to overall design cost which is more of a concern for a project that others might build in the future).
As a general rule, I tend to use (p)arallel notch filters in the (p)assband and (s)eries notch filters in the (s)topband.
I apologize for the criticism. Your procedure seems very similar to mine when it comes to crossover tweaking. I guess that I've always compromised a bit sooner with my crossover designs while you seem to go a bit deeper at taming each part of the response, but in the end it is the sound that matters (as you know). However, I don't hold the belief that too many crossover parts degrade the sound like some who strive for minimalist crossover approaches do (although I do look at the budget in terms of crossover parts cost relative to overall design cost which is more of a concern for a project that others might build in the future).
Roman,
No need to appologize; I am relatively new to this fascinating hobby and always look forward to learning new things, even though I may not realize their significance when I first encounter new ideas and suggestions.
My current approach with x-overs is to do "whatever it takes" until I am happy with the sound. Unfortunately this drives up the complexity and cost, but since my builds are one-offs for family and friends, I am ok with that compromize. IMO that the contribution of xo components to signal degradation is at least one or more orders of magnitude below the degradation from the drivers themselves so I don't get too hung up by the number of parts, as long as they are reasonable quality, except for the loss in sensitivity that they may introduce.
Originally Posted by romanbednarek
As a general rule, I tend to use (p)arallel notch filters in the (p)assband and (s)eries notch filters in the (s)topband.
Agree with you in general; I'll take a closer look at an alternate way to shape the response without hurting the overall impedance (this is probably where a modeling program would be very beneficial).
Cabinet construction is coming along slowly. Building the 3/4" roundover with pine quarter-rounds is turning out to be a lot more work than I thought because they are not cut vey accurately; lots of sanding will be needed to get the cabinet edges to allign with the roundover.
Cabinet construction is coming along slowly. Building the 3/4" roundover with pine quarter-rounds is turning out to be a lot more work than I thought because they are not cut vey accurately; lots of sanding will be needed to get the cabinet edges to allign with the roundover.
Next step is sanding and veneer.
Louis
So... They have 'junk in the trunk'??
Wolf
"Wolf, you shall now be known as "King of the Zip ties." -Pete00t "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith "We don't just make a crossover, we make a statement!" - Lawrence Fishburne for Cadillac
Yeah, I guess I never thought of the shape in those terms, but junk-in-the-trunk seems appropriate. My wife keeps commenting how she likes the shape.... lets leave it at that
Started veneering the cabinets with the backs first, and unfortunately I decided to try epoxy rather than the more conventional glues. This stuff is really difficult to work with without a vaccum press. I am having to go back along the edges to touch up the glue where it did not adhere completely.
I may switch to contact cement or the heat glue for the front/sides.
I am having to go back along the edges to touch up the glue where it did not adhere completely.
That's good practice anyway ... use a paintbrush and paint a glue line on the bottom side of the veneer where it meets the cabinet. You'll realize why when you start trimming the veneer, greatly reduces chips.
Cold press veneer glue is always the best option for flat panels. For irregular panels you need a vacuum bagger of course. But cold press for me has always given the most fool-proof results. The Heat Lock glue is nice, but I'm finding that it can be delicate. I've had a few panels bubble with it after putting on a water based poly finish.
That's good practice anyway ... use a paintbrush and paint a glue line on the bottom side of the veneer where it meets the cabinet. You'll realize why when you start trimming the veneer, greatly reduces chips.
Cold press veneer glue is always the best option for flat panels. For irregular panels you need a vacuum bagger of course. But cold press for me has always given the most fool-proof results. The Heat Lock glue is nice, but I'm finding that it can be delicate. I've had a few panels bubble with it after putting on a water based poly finish.
I am painting a line of glue along the edge as you point out, and where I can lift it up a bit, I am pushing some glue between the cabinet and the veneer.
I veneered another curved cabinet using contact cement and I did not have any of these problems so this one feels like a step backwards for me.
I'll take a look at the cold press glue, but wouldn't that have similar application characteristics to epoxy?
I kept moving forward with the epoxy and built a sling out of a rubber floor matt to hold the veneer against the sides and then used sheets of mdf for clamping the front and sides flat. Overall, it worked out ok with a few areas still needing some touch up. I still need to veneer the tops, but first I want to test the drivers and the x-over in the final cabinet, to make sure nothing needs to be adjusted.
But first I need to rest; this speaker building is hard work
Any suggestions on how to finish rosewood?
Is this one of those woods that needs to be oiled?
AC130MKII and Morel CAT408
![$vboptions[bbtitle]](images/techTalkHeader-leftGray2.jpg)
![$vboptions[bbtitle]](images/techTalkHeaderRepeatGray3.jpg)
Reply With Quote
Originally Posted by Ludo
It was autographed by Kevin Schwantz at Willow Springs Raceway before he became famous, at least to roadracing fans.
