Woofer replacement for Khanspires

[Stian-]

Hello All!

Damn, did it again, Rammstein does no good to my woofers or my wallet... :M

Ive built and used a set of Khanspires for about 8months, and recently i did some rather expensive upgrades to the crossovers, the speakers was good before with Dayton caps and ordinary bipolar on bass. Upgraded with Jantzen Z-Silver and Z-Superior caps complete in mid and tweet section, and a combination of mundorf and jantzen crosscap on bass. Let me just say, the change in the audio where great, everything just opened up a lot more and sounded much clearer. Anyway, im really happy with them, but i got a big problem.. The RS225 just cant handle my abuse.. They just simply cant! Ive built a new amplifier, this one is capable of pushing out about about 350w at 4ohm, and till now ive blown 3pcs of RS225, and those really dont come to cheap.

So, does any one have a suggestion for a worthy replacement? Pricetag upto 200USD each as long as the coil can handle some abuse, and the sound is in the class and clarity of RS woofers or potentially better. Cone needs to have about same color as RS woofers or it will not be so good looking. It will need to fit the cabinet size and also the crossover.

I have looked at a couple alternatives:
Seas L22RNX/P H1252 - 125w RMS power handling, but i think it might be to little.
Morel H8.1 - 3" voice coil with 180w RMS powerhandling

Now, the Morel really is interesting, but it have 3.8db higher sensitivity, which would mean that it will take over much more of the sound and create imbalance? Or?
The Seas also have somewhat higher sensitivty(its measured in 2.83v/1m - Not the same as 1w/1m so im not sure how to compare the two sensitive-wise), and is recommended for passive cabinet.

Thanks,
Stian

[5th element]

I don't know what the rest of your system is like, but you might be far better off keeping the RS225s and building some subs instead.

The RS225s can be had for less than $60 a pop, so really they do come cheap, especially when you're advocating spending $200 each, for a total of $800, for replacement woofers. That's 13 RS225s plus some spare cash!

Even if you replaced all 4 RS225s now, that'd leave you with $560 for subs.

One of these

http://www.parts-express.com/bash-500w-digital-subwoofer-plate-amplifier--300-752

plus one of these

http://www.parts-express.com/dayton-audio-um12-22-12-ultimax-dvc-subwoofer-2-ohms-per-coil--295-512

should be a good starting point and you could add in a second sub at a later date when funds permit.

The sub option allows you to keep the sound you obviously like from the current setup and means you don't have to mess about into the unknown with trying to find a suitable replacement driver. It should also guarantee a decent amount of success as cutting the bass to the mains (by applying a highpass), at say 80Hz, will significantly reduce the low bass demands placed upon the RS225s and make their job far easier. This will make them sound better at high output levels, that and you'll most likely get more bass extension too.

One of the problems with hifi drivers is that they are all (generally) similar in concept and construction, so buying another 8" hifi driver to replace the RS225s could simply result in more dead drivers. I know frying RS225s seems to be a rather common thing to happen, but I also get the impression that people really like to hammer them. Often the trouble with cooking drivers isn't in the coils ability to handle power, but is with the motor/magnets capability of conducting heat away from the coil to ensure it is kept cool. What happens is you start listening when everything is at room temperature, then as time goes on the entire motor/magnet/phase plug and cone will start to heat up, then the air inside the cabinet also heats up. As the ambient temperatures rise as does the peak coil temp, then the glues/resins/insulators break down and poof you have a dead driver. You may replace the driver with another one, but if the overall efficiency is the same then there's the same amount of heat needing to go somewhere and if it cannot be transfered successfully to the outside in some effective way, then any similar driver stands the risk of going poof.

Subs and a highpass will reduce the power going to the RS225s, so from my point of view, is probably the safest bet. That's if you can fit them in, but there are a number of tiny sub options nowadays too if you need small.

[Stian-]

They're already high-passed at 60hz 12db/octave with a couple of JL Audio W6-12`s - 80hz is to high with the crossover built into my receiver, i could maybe try a active crossover before the amplifier or something with 24db/octave. The JL`s they do most of the really low end. Well, there are lots of woofers with bigger voicecoils, which then again means they have more space to spread the heat, i have absolutely no doubt that there are many woofers with a lot better powerhandling out there than these..

I have no interest of needing to replace a driver each time my wife is out shopping.... Haha :-)
And also, im not from USA and have no local shop to go to buy RS225, so the price of each woofer is often doubled when i have to pay for shipping to norway, 25% taxes, importcosts etc., it is expensive. Cost me around 550USD when i bought the complete parts set for khanspires from PE(excluding some crossover coils on woofer) only in shipping.

[5th element]

I must apologise, when you mentioned your budget in USD, I took that to mean you were in the US. I should have paid more attention to the location thingy!

RS225s can be had for relatively low cost from Europe Audio I think? I'm guessing it isn't that much more expensive to you than to me in the UK. The RS225s are still cheap compared to others! But this is missing the point.

60Hz really isn't that high. Which is why I mentioned high passing further up as there is a lot of high energy content in a lot of music around 100-200Hz, snare drums, high toms, high bass, singers fundamentals, all will go into the RS225 with a 60Hz cross. Maybe it'd be worth loading the files that cook your loudspeakers into Audacity and running an FFT on it so we can see where a lot of the energy content is and then that might give you more ideas as to what might help fix things.

I have no doubt that other drivers would be more robust than the RS225, but if you consider for a moment that your RS225s are being cooked because they aren't going loud enough then this is a matter of efficiency. Looked at another way, if they went louder more easily then you wouldn't need to turn up the volume as much and less power would be required to hit the same SPL. Things wouldn't get as hot and things wouldn't start breaking. If you were to replace the drivers with something else of similar end sensitivity, then the same amount of power needs to be conducted away as heat, which is already pushing the RS225 beyond its limits. Maybe a scanspeak revelator would survive, but it wont be by a considerable margin and if one day you decided, oh I want 3dB more (which subjectively isn't that much louder)...that's twice the average power than cooked your current drivers and even a revelator wouldn't survive that for extended periods.

If you really do want to listen at very high levels for long periods of time, already have subs and a big power amplifier, then what you really need are more sensitive main loudspeakers. Each extra 3dB sensitivity the mains have means you need half the power for the same SPL, which is a big deal when you really want high SPLs.

I use the RS225s and have never blown one and I do like to turn it up every once in a while too. Others might have more practical advice to give, but maybe what you need is a variable highpass, switch it to say 100-120Hz when you really want to crank it, then lower it back down to 60Hz for the quieter listening sessions.

[cjd]

Before we go too far down this road, exactly how are they being destroyed? Voice coil melt-down? Over excursion? If it's excursion, either increase the slope of the crossover to the sub, or raise the frequency. And if you built ported, plug that port!

The tweeter is the most likely weak link in the Khanspire, which isn't necessarily saying much - however, it's crossed low enough that it is likely to see reasonable power levels, so both excursion and voice-coil heat level issues are more likely to arise here.

I don't know that any other drivers are drop-in - they might be, I just don't know. Frequency response, SPL, and impedance need to match up to be easily swapped.

Do you have any idea how hard you're pushing these? What kind of SPL? There's a point at which, if you keep this up, it won't matter - you'll be deaf before long.

The Seas has better midrange, not quite as good on the bass vs the RS225. I have no experience with the Morel, but the extra power handling isn't even going to buy you 3dB (I think - someone check my math? I'm doing it lazy today)

In the end, if you're trying to push things this (unknown?) loud for this long, you may need a system based around pro drivers.

The other thing to double check, if you can, is the distortion on the amplifier (and I'm not really sure what else - amps seem to be outside my area of success.) It is possible that there's something not quite where it should be that's inducing problems. Even the source may be worth investigating - I know Johnloudb recently traced distortion issues to his iPhone (or iPod?) - inadequate drive capability. That's not to say that it's likely, but it's always worth checking everything.

C

[Stian-]

Yes, could buy them from EA, would probably be a little cheaper with shipping, but way higher than to UK due to that Norway is not a EU country... :/

I know that much of the problem is in the efficiency of the drivers, but adding drivers with higher sensitivity would also cause more sound from the woofers vs mid/tw and the sound would not be so balanced in the speakers... right?

Ive had a look at the Revelator, it is interesting but that pricetag.. wow. But hey, they are really a close match to the RS225 when considering sensitivity and also seems to fit the cabinet volume really well.

Another alternative is to convert to ported instead of closed cabinet for the woofers, that would cause a lot less stress on the drivers, wouldnt it? According to WinISD calculations it will atleast below 50hz area, but then again it will rise the efficiency.

[Stian-]

Hello cjd, did not notice your post before just now. At the moment, they're not ported, built mostly by book with correct cabinet volume and width of frontbaffel.

No idea what kind of SPL levels we are talking, dont have equipment to measure that.

It seems to be melt-down but it could also be over excursion, as i can drive them into over excursion at anytime if i want to(once i hear sounds that is like this i immediatly turn down the volume a couple notches, but this usually dont happend when i have crossed at 60hz), but they where not at this when it broke this time, and vc seems to be melted due to the (very-nice)smell of it. Ive never burned a tweeter, yet atleast ;-) and the tweeter are still crystal clear at the levels of RS225 brakes down.

Amplifier have extremely low distortion, so theres no problems in that area, and i dont think source either since i only play flac quality files through my computer into a yamaha receiver and then out to the amplifier. I never, ever never use my phone as source...

I have been looking at Seas L22RN4X and theres also a pretty good match and i could have them on my doorstep within a couple days, ive compared them a little bit in WinISD, and i think these might fit good. They have a xmax of 14mm, and in the cabinet they would require 160w each to achieve xmax at 40hz, vs. the RS225 which reaches xmax at only 41w each at 40hz. They have almost 1db higher sensitivity but i dont think i will notice much of that. They will atleast fix the issue of over excursion i believe. They handle a little bit of more power also but not by much. 4 layer VC.

Ive attached a couple files

This one shows Xmax limits at 40hz


This one shows Maximum power vs frequenzy. This shows that the seas can receive their max power from just above 30hz, while the rs225 can receive max power from just under 60hz


This one shows Sensitivity. Pretty close but 1db higher in the 100-200hz area.


At what level are the RS225 crossed to mid?

Thanks,
Stian

[5th element]

Ah not in the EU, must remember that, my geography and politics suck >.<

It's the efficiency of the loudspeakers overall that's being problem, not just the RS225s. You'd need to replace the entire main loudspeakers with something 95dB+ for 8 ohms. But as CJD mentioned, how loud are you listening? Your hearing can't last long at levels like that and most, if not all, stuff I crank sounds great for 5 minutes then I need to turn it down. This isn't because of the loudspeakers croaking or the amps clipping, it's my ears...too loud just starts to sound bad after too long.

One answer is simple - turn it down. No more cooked woofers! Then again, if you've got a huge space to fill with sound, there's a reason why pro stuff exists for filling concert halls.

The Revelators are nice and are probably reasonably close to the RS225 too spec wise, but it's highly likely that you'd cook those as the difference in power handling wont buy you many more safe dBs.

If the ported version was tuned correctly it could net you higher efficiency around the 60-80Hz point, but that's not really ideal for RS225s, especially as you've got a highpass at 60Hz already. Getting more output between 35-50Hz isn't what you need I don't think.

As CJD said though, are these dying due to fried coils or over excursion. One results in mechanical failure from smacking the coil against the backplate, the other results in thermal failure from the non metalic parts breaking down. With a 60Hz highpass on 8" I'd be quite surprised if you were breaking them from overexcursion.

[5th element]

RS225s have 8mm of one way xmax for 16mm peak to peak. The SEAS drivers list theirs as a peak to peak figure of 14mm so in reality only have 7mm of one way xmax, 1mm less than the RS225s. Linear excursion might not be the issue, but if you broke them this time without the high pass in place then that could make sense. I simulated the RS225 in a large sealed box and with a 2nd order highpass in place you'd fry them way before you'd break them from smacking the coil into the back plate. Without the highpass you'd destroy things mechanically before they melted, especially at lower frequencies.

[---k---]

If you built them correctly and you are playing them at levels that are destroying the woofers, then you will destroy whatever woofers you put in them. You're expectations are too high. You should consider building a pair of speakers that better fits your needs.

[TEK]

Hi Stian

It seems to be some differences between your experiences of the speakers and what other is expecting from them.
Are you located in Trondheim? I think I have a SPL meter laying around. I also have a mic and some equipment, If you want to do some measurments you can borrow my equipment (I have little experience using it yet so you will probably have to do some work learning to take measurments - I cant help you much there). Let me know if your interested.

Also, maybe you could fill us inn with some information regarding:
- room size
- what amp and receiver you are using
- receiver volum level you are listening on when breaking your woofers
- what EQ settings are you using (receiver + PC)?

Regarding that last question about EQ - if you have a large room and using room correction, and maybe have added some bass in the computer as well - that might introduse extra load on the woofers. Just trying to figure out if there is any factors here that are special, as it seems to me that other expects the tweeters to give way before the woofers...

[agrippa]

If you built them correctly and you are playing them at levels that are destroying the woofers, then you will destroy whatever woofers you put in them. You're expectations are too high. You should consider building a pair of speakers that better fits your needs.

In my industrial arts/math class I teach I have my students build speakers from time to time. The first thing I have them do was identify the purpose of their project. Such as music type, volume played, room size, equipment used, source (cd, mp3, so on). In a few cases some students ended up building pro audio designs. Which is what I would recommend to you. Either that or do as others have told you and cross the sub over at a higher frequency. The particular driver that you are having an issue with is a good one. I have used them in several designs including a line array fro a church organ. They can handle a good deal ... believe it.

Side note: I had a one kid who was a DJ. He wanted duel purpose speakers. Pro audio for his business and something that could play refined as it were. I convinced him that he needed 2 sets. In order to do what he wanted 2 sets of speakers ended up being cheaper than one set that could do it all. Just a thought. Maybe you need 2 sets to do different things... heck 3 sets is even better. ha