Hi
I finally got my test cabs up and running yesterday with some help from a more experienced speaker builder friend. They consist of scanspeak D3004/66000 tweeter, 15W4531G00 & 2 x 18w8531G00 per side.
The tweeter to 15w x-over is a passive design from Goran's (audioexcite) Revelation2 design and the 18W to 15W will be active (currently using basic DSP to get and idea of what sounds best first).
As expected for a first time listen, there were good and bad things that struck me. One of the good things is that they played nice and low and had a good sense of scale. What left me feeling somewhat underwhelmed however, was some of the dynamics from the bass. The 18W's are running in 40L each and have ports that are tuned to 33HZ. I played around with the x-over point between 140 to 650hz and found that they sounded happiest when crossed between 200 to 250hz. At the moment I have only used LR4 for this x-over. I should also mention that I don't think that the rear panel (screwed on) is completely sealed. In fact I'm fairly certain of this.
I noticed that when playing familiar music like dark side of the moon, deep bass (synths etc) rumbled through nicely and the higher bass coming from the 15w was good (including dynamics) but the thump from kicks drums etc sounded muted and a bit lifeless.
I am basically trying to get an idea of what the likely cause is and thought I would canvas the opinions of some of the people here? Do you think it is:
a) badly sealed cabs?
b) x-over type?
c) port tuning
d) something else?
Like I say, it's in the very early stages, but I would like some insight into this to help get things moving in the right direction. If I can get this sorted, I think they will make the basis of a very impressive pair of speakers (by my standards anyway😉)
Thanks
Paul
I finally got my test cabs up and running yesterday with some help from a more experienced speaker builder friend. They consist of scanspeak D3004/66000 tweeter, 15W4531G00 & 2 x 18w8531G00 per side.
The tweeter to 15w x-over is a passive design from Goran's (audioexcite) Revelation2 design and the 18W to 15W will be active (currently using basic DSP to get and idea of what sounds best first).
As expected for a first time listen, there were good and bad things that struck me. One of the good things is that they played nice and low and had a good sense of scale. What left me feeling somewhat underwhelmed however, was some of the dynamics from the bass. The 18W's are running in 40L each and have ports that are tuned to 33HZ. I played around with the x-over point between 140 to 650hz and found that they sounded happiest when crossed between 200 to 250hz. At the moment I have only used LR4 for this x-over. I should also mention that I don't think that the rear panel (screwed on) is completely sealed. In fact I'm fairly certain of this.
I noticed that when playing familiar music like dark side of the moon, deep bass (synths etc) rumbled through nicely and the higher bass coming from the 15w was good (including dynamics) but the thump from kicks drums etc sounded muted and a bit lifeless.
I am basically trying to get an idea of what the likely cause is and thought I would canvas the opinions of some of the people here? Do you think it is:
a) badly sealed cabs?
b) x-over type?
c) port tuning
d) something else?
Like I say, it's in the very early stages, but I would like some insight into this to help get things moving in the right direction. If I can get this sorted, I think they will make the basis of a very impressive pair of speakers (by my standards anyway😉)
Thanks
Paul
Hard to say without further clues, but your 33Hz tuning seems fairly high. My guess is that, with room influence, the low bass region will be too loud and the region 80-100Hz suffers. Speaking of the room, standing waves do of course interfere quite a bit in the region up to 200Hz, so don't count that out.
Could try leaving the bass at the 200-250 and overlapping the mids down to around 80-100……might fill in whats lacking?
Could just be a timing issue between drivers. The DSP you're using is probably lagging behind the passive tweeter xo, if separate. Or is the passive xo being fed through the DSP?
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The passive x-over is being fed through one channel of the DSP and the 18w's through the second channel so it hopefully should be ok timing wise.
FWIW, I used a single 18w/8531G00 in an ML-TL 2-way some years ago and found a 28-Hz tuning frequency was optimum, resulting in an f3 of 32 Hz and f10 of 23 Hz. The gross volume of the cabinet is ~50 liters.
Another Paul
Another Paul
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I have a TMWW using 2 of the 18w8531 woofers, both sharing a 52 liter cabinet tuned to 35 Hz. I have them crossed 2nd order electrical (IIRC they were 3rd acoustic) at roughly 275 Hz to a 7" Ellipticor midwoofer, bass from the 18w woofers is nothing short of spectacular. The crossover is a passive 3.5 way, but I didn't do a typical .5 way on the low pass filter, I used a separate crossover on each of the 18w woofers. The lower woofer starts rolling off at around 150 Hz, the upper is rolling off around 250 Hz. FWIW, my cabinet has a 1.5" front baffle, 3/4" everywhere else with ample bracing throughout. My port is a 3" x (IIRC?) 5.5" long.
I might say your woofer box is a smidge small, in your 140 L cabinet your f3 is 43 Hz, mine is 38 Hz. Not a huge difference but could be noticeable.
My initial guess in your situation, aside from cabinet size is that you need to attenuate your mid and tweeter a couple/few db with your DSP, possibly those are too loud and are stifling the bass. Or play with your DSP and play around with different roll offs on your 18w woofers. Your system should sound absolutely phenomenal, I've used all the drivers in your build at different times and you definitely have a winning combination there. If I had one gripe about the 18w, it's output, I can get them to "pop" accidentally from time to time (I actually already blew one of mine and had to replace it). They don't like the beginning of Pink Floyd, Hey You at higher SPL lol.
I might say your woofer box is a smidge small, in your 140 L cabinet your f3 is 43 Hz, mine is 38 Hz. Not a huge difference but could be noticeable.
My initial guess in your situation, aside from cabinet size is that you need to attenuate your mid and tweeter a couple/few db with your DSP, possibly those are too loud and are stifling the bass. Or play with your DSP and play around with different roll offs on your 18w woofers. Your system should sound absolutely phenomenal, I've used all the drivers in your build at different times and you definitely have a winning combination there. If I had one gripe about the 18w, it's output, I can get them to "pop" accidentally from time to time (I actually already blew one of mine and had to replace it). They don't like the beginning of Pink Floyd, Hey You at higher SPL lol.
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Thanks for the further replies everyone.
PKitt -, my cabs are built now so extending to 50L isn't an option but I take your point about maybe trying to tune the port a bit lower.
Mattsk8 - I am running the 18W in 40L per drive unit ( ie total woofer space is 80L per cabinet) so hopefully I should have adequate volume. Some of the very lower end of the bass is already impressive so maybe I do need to attenuate the mid and tweeter slightly and also lower the port tuning so that the main part of the bass is raised whilst the lowest registers of bass doesn't overwhelm the balance. (I hope that makes sense?)
Out of interest, why did you roll the woofers off at different frequencies? I am familiar with the principle of 2.5 ways and 3 ways but yours sounds like something in-between?
It is also reassuring to hear positive feedback from different people about the choice of units based on their first hand experience. I do have a good feeling about what these could be capable of, I just have a bit of work to get them to do full justice to the components used. Oh and Hey you is one of my favourite tracks of all time and certainly a test for most speakers (as is most of the the wall album 🙂).
PKitt -, my cabs are built now so extending to 50L isn't an option but I take your point about maybe trying to tune the port a bit lower.
Mattsk8 - I am running the 18W in 40L per drive unit ( ie total woofer space is 80L per cabinet) so hopefully I should have adequate volume. Some of the very lower end of the bass is already impressive so maybe I do need to attenuate the mid and tweeter slightly and also lower the port tuning so that the main part of the bass is raised whilst the lowest registers of bass doesn't overwhelm the balance. (I hope that makes sense?)
Out of interest, why did you roll the woofers off at different frequencies? I am familiar with the principle of 2.5 ways and 3 ways but yours sounds like something in-between?
It is also reassuring to hear positive feedback from different people about the choice of units based on their first hand experience. I do have a good feeling about what these could be capable of, I just have a bit of work to get them to do full justice to the components used. Oh and Hey you is one of my favourite tracks of all time and certainly a test for most speakers (as is most of the the wall album 🙂).
Apologies Mattsk8, I have just re read your post and realise that you stated that your crossover is 3.5 way, which I assume is the same principle as 2.5 way but with a mid thrown into the mix.
Based on that I would say your box(es) are too large and this is most likely killing the dynamics (that can make woofers sound tubby). I'm sharing a 52 liter cabinet for both of mine. Depending on where your port is, this would be fairly simple to test by filling the bottom of your cabinet with something. I'm not exaggerating when I say the bass from mine is absolutely phenomenal, some of the best bass I've heard from a woofer IF I don't include output. Maybe I need to do a WWMTMWW using 4 of these to bump the SPL a smidge lol.
Yes, correct. In my opinion it's easier to manipulate the .5 way by just using 2 crossovers (one per woofer) rather the standard way of just adding a coil on the lower woofer, more expensive but not a lot. It pretty much is the same principal as a conventional .5 way crossover, just gives me more options in the crossover (I hate chesty sounding midrange/midbass).
Edit: And we are 100% in agreement on Hey You, The Wall is such a fantastic album 😎
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I haven't had or built for these drivers, but I have noted that trying to do early listening tests on boxes that aren't perfectly sealed has always been a waste of time for me. Though I wish it were otherwise, and I try it every time... A specific sealing solution is probably dependent on the specifics of your build. I use rope caulk. For a big money build a separate fully built test box might be appropriate. I'd check that before drastically altering your plan.
I think I am starting to get a plan of action together now. I think the first step is to make sure the cabs are properly sealed.
Then I will try putting house bricks in to reduce the volume (quick calcs seem to indicate that each brick is approx 1.4L) to see if that helps. I hope so as less volume has the added advantages of more options for a more eye friendly speaker and/or greater amounts of internal bracing.
After that Some playing around with attenuating the mids and tweeter slightly (maybe even overlapping more as suggested by mountainman Bob) and then trying different port lengths (probably lower Fb).
Another question that has sprung to mind is whether to have separate chambers for each drive unit (as they are now) or to have a shared enclosure as Mattsk8 has? Is there any strong reason to go for one over the other?
If using a shared chamber is it simply a case of doubling the volume that one driver would use or is there a different calculation to be done to determine the correct volume?
Then I will try putting house bricks in to reduce the volume (quick calcs seem to indicate that each brick is approx 1.4L) to see if that helps. I hope so as less volume has the added advantages of more options for a more eye friendly speaker and/or greater amounts of internal bracing.
After that Some playing around with attenuating the mids and tweeter slightly (maybe even overlapping more as suggested by mountainman Bob) and then trying different port lengths (probably lower Fb).
Another question that has sprung to mind is whether to have separate chambers for each drive unit (as they are now) or to have a shared enclosure as Mattsk8 has? Is there any strong reason to go for one over the other?
If using a shared chamber is it simply a case of doubling the volume that one driver would use or is there a different calculation to be done to determine the correct volume?
Your brick idea is a good one, maybe cut up a Tshirt so you can wrap each brick to avoid some obnoxious rattling. I would seriously start with 8 bricks, if the bricks are 1.4 liters that would get you close to where my cabinet is. Mine is 52 liter, so basically 26 per woofer. You'll need to eat up 14 liters per cabinet (10 bricks) to be right where I'm at.
I don't know if you mentioned what DSP you're using so not sure how easy this is, but playing with the mid/tweeter attenuation is also a great idea. When you do the brick experiment, it might be a good idea to dial down the mid/tweet a bit (just for this experiment) so the bass is more pronounced, you'll be able to better hear the difference. Once you figure out if it's a cabinet volume issue, then fine tune the attenuation.
As far as your shared vs single cabinet per woofer question... That's a great question. Aside from actual subwoofers I've never played with this using woofers, and even with subwoofers I never did a direct, side by side comparison. Every time I build a speaker that used 2 woofers I always build a single cabinet for both woofers. Not because "that's the right way to do it", but just because it was easier. Would be interesting to compare 2 cabinets vs a single to listen for a difference. That said, I doubt that's your problem, not saying it is not the problem but I highly doubt it. If anything I would guess 2 cabinets would give better dynamics but that's just an untested guess.
I don't know if you mentioned what DSP you're using so not sure how easy this is, but playing with the mid/tweeter attenuation is also a great idea. When you do the brick experiment, it might be a good idea to dial down the mid/tweet a bit (just for this experiment) so the bass is more pronounced, you'll be able to better hear the difference. Once you figure out if it's a cabinet volume issue, then fine tune the attenuation.
As far as your shared vs single cabinet per woofer question... That's a great question. Aside from actual subwoofers I've never played with this using woofers, and even with subwoofers I never did a direct, side by side comparison. Every time I build a speaker that used 2 woofers I always build a single cabinet for both woofers. Not because "that's the right way to do it", but just because it was easier. Would be interesting to compare 2 cabinets vs a single to listen for a difference. That said, I doubt that's your problem, not saying it is not the problem but I highly doubt it. If anything I would guess 2 cabinets would give better dynamics but that's just an untested guess.
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One more thing... Not saying you're a moron, but double check the polarity on your woofers, make absolutely sure they're wired correctly. There is a possibility for one of the woofers to be accidentally wired out of phase, which would then nullify all the bass out of that side. Not saying I've ever done something like that 🤣
Many, many years ago, early in my speaker-building, I built a pair of 3-ways utilizing a pair of isobaric-configured woofers in each cabinet, and at one point in my evaluating them via listening, they sounded really weird. Turned out I had incorrectly connected the two woofers in one of the two cabinets.
Funny, in this build using the four 18w woofers I did exactly that, had one of the woofers out of phase on my very first listen. I remember thinking, "these woofers sound terrible, how is this possible?" haha 😅
Also it's great to hear from you @pkitt! Been a while! Not sure if you remember the Blues MTM project you designed the MLTL cabinet for me on (sounded fantastic BTW), but in that build, one of the HiVi L6 woofers had a voice coil out of phase from the factory. That took me a while to figure out, the trusty battery method for testing polarity finally showed me that issue. That's the only time I've ever had that happen.
The battery method! I built a tester, a AA holder, with a momentary switch and alligator clips on the leads, cause I got tired of running out of hands to do this one easily.
Thinking more about this, I can only think of positives that would come from using 2 different cabinets and no negatives (anyone feel free to correct me). The major plus would the potential to avoid a standing wave by using one box per woofer, verses both woofers in one box. I really don't think 2 different boxes is an issue at all.
