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Multi-Way Conventional loudspeakers with crossovers

Weaker low-range response of 3-way speaker
Weaker low-range response of 3-way speaker
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Old 11th April 2018, 08:21 AM   #1
krasnypixel is offline krasnypixel  Slovakia
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Default Weaker low-range response of 3-way speaker

Hi guys,
Im new to this forum so apologies for asking maybe mundane question.

I have decided to build my second DIY audio project, 3 way ported loudspeaker.

Components selected for the build were
Lows - Dayton Audio RS225-8 8" Reference Woofer
Mids - HiVi F5 5" Bass/Midrange
Highs - Dayton Audio PT2C-8 Planar Tweeter

Im crossing the drivers using Eminence PXB3:3K5 crossover at 500/3500 hz with 2nd order slope for woofer, 1st order filter for midrange and 3rd order for tweeter

Box and port were calculated in WinISD software. Port is tuned for 30hz in 42 litres enclosure (7.5 cm (3in) diameter, cca 31c (12in) length - flared)

Midrange enclosure is separated from woofer, for the sake of the prototype building however, larger than suggested cabinet size was used (14 litres instead of 5 litres) and was properly damped.

After building prototype enclosure for the speaker and testing the speaker i was

a) Amazed by performance in mid and high range, clarity and separation of instruments is very nice, especially considering that the prototype build is rough.
b) Weak low-range performance. Bass is clear , however it lacks any depth and "punchiness" . Im not talking about groundshaking performance, but overall, the bass is weak.

This was confirmed by measurement which has shown 6-7db lower performance across the band, up to the 500hz crossover frequency.

When I adjusted preamplifier to +7db for lows and -7db for highs, sound started to appear more balanced, but I still was a little bit disappointed by the overall performance.

I was rather surprised by this issue, as this is my second build (first was 2way speaker) , and It was calculated the same way. First build has amazing bass considering that it uses only 4inch midwoofer drivers.

Could you please advise me what could I do wrong? Many thanks for your replies.
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Old 11th April 2018, 09:19 AM   #2
AllenB is offline AllenB  Australia
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By saying that you compensated for a measured result, I assume you have dealt with the primary effect of sound at lower frequencies radiating around the enclosure and spreading, rather than going forward.

There is a secondary effect of this, in that this rearward sound reflects off the walls behind and to the side and interferes with the direct sound. It is frequency dependent and is not simple to fix. Try rearranging your speaker location.

Then there are room issues at the lowest frequencies that will probably need attention. You might find interest in the multiple subs thread.

You can also try tilting your response downward at the high end. I can only guess at this one without more information but it is easy enough to try.
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Old 11th April 2018, 10:15 AM   #3
KaffiMann is offline KaffiMann  Norway
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Weaker low-range response of 3-way speaker
Are you certain the box is not leaking? Is everything nice and tight? Every single small crack sealed? Every wire coupled correctly? No phase cancellations? Bad room interaction (some rooms suck the life out of bass)?
May be better to go with something like Dayton Audio DS315-8 with that mid and tweet.
But -7db and+7db so 14db correction? Something is not right.

Last edited by KaffiMann; 11th April 2018 at 10:19 AM.
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Old 11th April 2018, 10:21 AM   #4
krasnypixel is offline krasnypixel  Slovakia
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Thank you both for replies,

I have tried switching polarity of drivers and actually achieved better performance with inverted polarity of the woofer (+/-2 db).

Woofer enclosure was glued together, however being perfectly honest, I did not check extremely thoroughly for possible small leaks as I thought that in the vented cabinet with such large vent, these would not have major impact on the bass reflex performance.
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Old 11th April 2018, 10:28 AM   #5
Jerms is offline Jerms  United Kingdom
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Woofer and mid sensitivity is about the same, tweeter is way more efficient. Tweeter would need attenuation to match the mid properly (by a lot.... 86-87 vs 94dB).

No mention of baffle step correction. Lows tend to flow around the enclosure instead of projecting forwards off the baffle. "The edge" software can model how this might manifest.

Placement of speakers in room is critical if rear ported. I have one in a corner and one near a door. All the bass in room comes from the corner one. The bass for the other tend to appear in the hallway.

HTH

J.
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Old 11th April 2018, 11:56 AM   #6
denibeni is offline denibeni
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This is a good example of how a premade crossover rarely works good.
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Old 11th April 2018, 12:44 PM   #7
fatmarley is offline fatmarley  England
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Quote:
Originally Posted by denibeni View Post
This is a good example of how a premade crossover rarely works good.
Yes, that's the problem.
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Old 11th April 2018, 02:18 PM   #8
DonVK is offline DonVK  Canada
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Quote:
Originally Posted by krasnypixel View Post
Components selected for the build were
Lows - Dayton Audio RS225-8 8" Reference Woofer
Mids - HiVi F5 5" Bass/Midrange
Highs - Dayton Audio PT2C-8 Planar Tweeter
Eminence PXB3:3K5 crossover at 500/3500 hz
Box and port : 42 litres enclosure (7.5 cm (3in) diameter, cca 31c (12in) length - flared)
Quote:
Originally Posted by krasnypixel View Post
Midrange enclosure is separated from woofer, for the sake of the prototype building however, larger than suggested cabinet size was used (14 litres instead of 5 litres) and was properly damped.
Is the woofer's space (volume) seperated from both the midrange and tweeter? You could be leaking through those other drivers.

Quote:
Originally Posted by krasnypixel View Post
a) Amazed by performance in mid and high range, clarity and separation of instruments is very nice, especially considering that the prototype build is rough.
b) Weak low-range performance. Bass is clear , however it lacks any depth and "punchiness" . Im not talking about groundshaking performance, but overall, the bass is weak.

This was confirmed by measurement which has shown 6-7db lower performance across the band, up to the 500hz crossover frequency.

Could you please advise me what could I do wrong? Many thanks for your replies.
The XO points are probably fine but, as you say the FR balance is off. The tweeter you are using has sensitivity of 94db and the woofer/mid is only 85db. That's a 9db difference that will make the speaker sound "bright" (by design) due to the relative differences. Installing an L-pad on the tweeter will fix this.

Second issue is the lack of bass. This might be from baffle step loss or it could be a mistuning, or even a leak. Are you able to post near field measurements for the woofer and its port ?
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Old 11th April 2018, 03:53 PM   #9
DonVK is offline DonVK  Canada
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A quick run on HornResp to check your design tuning (pic#1 and graph#1) and it looks fine. However it does not include bafflestep effects.

To check your LF tuning / construction use a s/w freq generator (like in REW) to look at the woofer movement (graph#3) at the box tuning freq (30Hz) the woofer will barely move. It's a very rough indicator of leaks and construction issues. Measurements are much, much better if you can provide it. I should add that a 12" port tube makes your box deep, or possibly limiting the space behind the tube to operate properly.
Attached Images
File Type: jpg kras br 42l input.jpg (58.3 KB, 203 views)
File Type: jpg kras br 42l fr.jpg (43.8 KB, 202 views)
File Type: jpg kras br 42l displ.jpg (44.5 KB, 201 views)

Last edited by DonVK; 11th April 2018 at 03:57 PM. Reason: port tube length
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Old 11th April 2018, 03:56 PM   #10
krasnypixel is offline krasnypixel  Slovakia
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Quote:
Originally Posted by DonVK View Post
Is the woofer's space (volume) seperated from both the midrange and tweeter? You could be leaking through those other drivers.



The XO points are probably fine but, as you say the FR balance is off. The tweeter you are using has sensitivity of 94db and the woofer/mid is only 85db. That's a 9db difference that will make the speaker sound "bright" (by design) due to the relative differences. Installing an L-pad on the tweeter will fix this.

Second issue is the lack of bass. This might be from baffle step loss or it could be a mistuning, or even a leak. Are you able to post near field measurements for the woofer and its port ?


Thanks for the answer. Yes, I thought that the tweeter may sound too bright, which (subjectively from listening point is not too big issue in this case.


I will try to check for possible air leaks from the cabinet and make near field measurements of the woofer and the vent


Im attaching links to the cabinet picture




https://1drv.ms/u/s!Ao7eEJyYPDPNg8scp3KdwwfvNKhFWA


https://1drv.ms/u/s!Ao7eEJyYPDPNg8sd2SMDLTD7JMMebA
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