Mid/high drivers

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I'm building a sort of FAST speaker, where a subwoofer driver will be handing off to a mid/high driver with an active crossover around 300-500Hz. My subwoofer driver can cleanly handle 100db peaks through most of it's frequency range, so I'm struggling to find a single driver with good off-axis response that can do the same.

Oh, and of course, as if that weren't hard enough, it has to be cheap.

My current winning candidate seems to be the Tang Band W2-852SH. It seems to have great off-axis response for its size. With the exceptionally low Q, I can jam it into a tiny rear chamber to push the impedance peak nearly to the crossover point at 400Hz. This will really reduce the power consumption on the low end of its bandwith, where it will be experiencing a lower crest factor, and generally higher RMS power than up high. The weakness is that in sims it seems to run out of excursion a bit earlier than I would have hoped.

The FaitalPRO 3FE25 looks nice with incomparable efficiency for the price range, but the off-axis is quite poor. Pushing the impedance peak into the bandwidth creates a bit too much hump with it's higher electrical Q. I might be able to work this into baffle step compensation though, but that narrow listening window and gnarly breakup modes in the upper midrange really make me hesitant.

Dayton Audio's RS75-4 seems good. The sensitivity is a bit meh and the frequency response needs more active correction than others. I wish it had a stronger motor so I could have a larger impedance peak at the bottom of the frequency range. The manufacturer's specs claim a suspiciously small Sd for a 3", which sims into distortion before reaching the volumes I need.

CDT Audio claims to have basically the perfect thing for me, but each driver blows my budget for the entire enclosure. I know I can find what I need in my price range if I really do some digging, but I don't know where to look to find it.

Have any of you toyed with a similar idea? What other drivers might suit my needs? Any and all help would be greatly appreciated!
 
frugal-phile™
Joined 2001
Paid Member
Even the stock versions of our favorite mid/tweeters are out of your price range (FF85wKeN/Alpair 7.3eN) i'd guess. There are lots of choices for cheap FRs, but often you get what you pay for. There are some decent choices thou. After our experience with the Vifa TC9 i hesitate to suggest anything i haven't tried.

If you are crossing that high you probably want a woofer, not a subwoofer, as most of the latter don't go high enuff. You want something that extends at least 2 octaves beyond the XO point (ie 1.2-2 kHz). Some of the helper woofers we use are actually more extended than some so-called FRs (response to 5-10k).

And i'd really hesitate to try to get sealed box response to roll off at the XO, the Q of the box will likely be too high.

dave

PS: The SS 10F was mentioned… a good driver, but our experience is that the similarily priced FF85wKeN eats it for breakfast. We have yet to do compares with the (much cheaper) stock version, but we have all the pieces in place to do that comparison.

PPS: like Geddes i don't pay much attention to the measured distortion
 
I'm building a sort of FAST speaker, where a subwoofer driver will be handing off to a mid/high driver with an active crossover around 300-500Hz. My subwoofer driver can cleanly handle 100db peaks through most of it's frequency range, so I'm struggling to find a single driver with good off-axis response that can do the same.

Oh, and of course, as if that weren't hard enough, it has to be cheap.

My current winning candidate seems to be the Tang Band W2-852SH. It seems to have great off-axis response for its size. With the exceptionally low Q, I can jam it into a tiny rear chamber to push the impedance peak nearly to the crossover point at 400Hz. This will really reduce the power consumption on the low end of its bandwith, where it will be experiencing a lower crest factor, and generally higher RMS power than up high. The weakness is that in sims it seems to run out of excursion a bit earlier than I would have hoped.

As far as I know: small enclosure reduces excursion but not power consumption. Having an active cross ~400Hz would be a bigger help than any shenanigans with rear chamber size. Also: I'd suggest using a a fairly wide baffle >30cm, so that you don't have baffle losses occurring above the crossover point.

Have any of you toyed with a similar idea? What other drivers might suit my needs? Any and all help would be greatly appreciated!

Yea, I've made a couple of big dumb FAST systems, like the pictured design, with the full-ranger mounted in a sub-enclosure of the bass box. The FR fires into a heavily stuffed line that exits the rear of the box. This means the FR benefits from the large shared baffle, and I also just like the look of a single box.

The best budget is no budget.

Other drivers that might suit your needs: old TV speakers. Get them for free - take advantage of the (literally) tons of once high $ TVs that are being thrown out to be replaced by flat screens. In my experience, good TV speakers are better than equivalents from boomboxes / micro 'hifi' systems.

About 18 months ago I made a FAST for a friend, intending to use Fostex drivers, but I found some equivalent salvaged units that actually sounded better. These were from a small Phillips TV that was in hard rubbish. Some enterprising types had already cracked the TV open to recycle all the copper.

A trick to get extra dispersion from a full range driver: add a rear-firing tweeter. These can also be obtained for free, or looted from broken equipment - I have a couple of pairs of tweeters that measure perfectly >4kHz, and that are salvage (I picked up 4 tweeters for $5 as part of a bulk buy. I grabbed the nicest looking pairs from a box of ~20).
 

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As far as I know: small enclosure reduces excursion but not power consumption.

Shrinking the chamber puts a hump in the response at the lower cutoff. It also pushes the impedance peak upward in frequency. This is how I'm increasing efficiency. I'm increasing sensitivity and increasing impedance so it uses less current. The tradeoff is reduced low-end extension. This is perfectly fine for me because I'm trying to turn a full-range into a mid-range.
 
Even the stock versions of our favorite mid/tweeters are out of your price range (FF85wKeN/Alpair 7.3eN) i'd guess. There are lots of choices for cheap FRs, but often you get what you pay for. There are some decent choices thou. After our experience with the Vifa TC9 i hesitate to suggest anything i haven't tried.

In what way do these drivers outperform the competition? Manufacturer data suggests worse off-axis response than the Daytons and some Visaton options, with minimal improvements in efficiency. Excursion is clearly better, but low end isn't much of a concern for me.

If you are crossing that high you probably want a woofer, not a subwoofer, as most of the latter don't go high enuff. You want something that extends at least 2 octaves beyond the XO point (ie 1.2-2 kHz). Some of the helper woofers we use are actually more extended than some so-called FRs (response to 5-10k).

And i'd really hesitate to try to get sealed box response to roll off at the XO, the Q of the box will likely be too high.

PPS: like Geddes i don't pay much attention to the measured distortion
Why would I need a full two octaves? I, like you and Geddes, don't worry much about distortion. Plus with the crossover, the magnitude of breakup nodes will be negligible compared to the mid/tweeter's output at those frequencies.
 
frugal-phile™
Joined 2001
Paid Member
Manufacturer data suggests worse off-axis response than the Daytons and some Visaton options, with minimal improvements in efficiency.

Manufacturer data (other than T/S) tells you only a little about the total performance of the driver. Further, there is no manufacturer data for the modified versions of the drivers i mentioned.

Why would I need a full two octaves?

A driver is still working well past the XO. I usually like even larger overlap. But then i like to stick to 1st order XOs so as to preserve phase & keep things simple.

dave
 
This gives an underdamped response which can affect things higher up.

dave

In what way? If the frequency response curve is smooth, the impulse response is necessarily smooth as well since they can be derived from each other. The Q factor of the box is only a small part of the final acoustic slopes in a multi-way enclosure. The acoustic slopes determine the group delay, not the Q factor.
 
frugal-phile™
Joined 2001
Paid Member
But the FR is not smooth, you have an underdamped bump at the bottom. This is similar to the problems caused by drivers with a significant ring up high… even if you notch that frequency out to get flat FR it can still cause audiable problems.

Often, another consequence of putting a midTweeter into a small box, or even having the sides too close to the driver, is a cuppiness in the drivers sound.

I typically use a heavily aperiodically damped, oversize midTL.

dave
 
Manufacturer data (other than T/S) tells you only a little about the total performance of the driver. Further, there is no manufacturer data for the modified versions of the drivers i mentioned.

I am not familiar with the modified versions of these drivers. Where can I find some data on them?


A driver is still working well past the XO. I usually like even larger overlap. But then i like to stick to 1st order XOs so as to preserve phase & keep things simple.

dave

I plan to be using an LR4, so I won't need as much overlap. I can also use the individual driver roll-offs as part of the final acoustic slopes.
 
frugal-phile™
Joined 2001
Paid Member
I am not familiar with the modified versions of these drivers. Where can I find some data on them?

planet_10 hifi | drivers
FF85wKeN
Alpair 7.3eN

I plan to be using an LR4, so I won't need as much overlap. I can also use the individual driver roll-offs as part of the final acoustic slopes.

I avoid LR4 XOs, something about them just doesn't sound right.

In a FAST with its low XO point it is pretty easy to keep the driver centre-to-centre distance below a ¼ wavelength of the XO frequency. Using an XO that maintains phase (not anything over 1st order, unless it is one of the more exotic digital XOs) you are almost guaranteed phase coherence. If you are careful with the speaker design you can get away with 1st order PLLXO which is dirt cheap and adds no electronics artifacts.

Remember, XOs are inherently evil.

dave
 

This has a nice explanation, but I'm looking for some hard data. Where can I find T/S parameters, frequency response, polar pattern, some objective measure of improved performance?


I avoid LR4 XOs, something about them just doesn't sound right.

In a FAST with its low XO point it is pretty easy to keep the driver centre-to-centre distance below a ¼ wavelength of the XO frequency. Using an XO that maintains phase (not anything over 1st order, unless it is one of the more exotic digital XOs) you are almost guaranteed phase coherence. If you are careful with the speaker design you can get away with 1st order PLLXO which is dirt cheap and adds no electronics artifacts.

Remember, XOs are inherently evil.

dave

Lol, that's why I initially posted this to the multi-way forum. I'm one of those heretics that believes in crossovers! *hides from pitchforks*
 
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