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Dual 15" mid/highs upgrade

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Jack_The_Ripper View Drop Down
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    Posted: 16 June 2018 at 5:05pm
I have a simple question I know generally when upgrading drivers you need to check the TS parameters to see if drivers will work well in cabinets but I have a pair of dual 15" + 1.4" cabs and was wondering considering i'll be using them above 100hz (always on top of my subs) is matching TS parameters of standard drivers and new drivers as necessary as it would be if using the cabs full range? 

I know driver xmax is an issue when upgrading but if say for example I put B&C 15NW76 drivers in and Faital Pro HF146 compression drivers should I expect too many problems? The external dimensions of my dual 15"+1.4" mid/highs is 1218mm high x 558mm wide x 522mm deep, they're 15mm plywood and have a front to back and side to side brace in the middle inside. I'm planning on running them biamped.


Edited by Jack_The_Ripper - 16 June 2018 at 5:13pm
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djkeet View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote djkeet Quote  Post ReplyReply Direct Link To This Post Posted: 16 June 2018 at 5:17pm
I would have thought so cause its still a matter of efficiency
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jack_The_Ripper Quote  Post ReplyReply Direct Link To This Post Posted: 16 June 2018 at 5:32pm
Yeah but you can control sound level with biamping them and any eq in the louadspeaker processor that's needed to make the drivers work together to give you a good sound right?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote njw Quote  Post ReplyReply Direct Link To This Post Posted: 16 June 2018 at 10:02pm
IMO, a 2x15 plus comp cab is always going to be a compromise, more so when using it as a mid top (I've done it and was never happy with the results!). Personally I would be looking at using a dedicated mid top cab with 10 or 12" mid range drivers rather than upgrading the 15's you have. Just my two penneth. Smile 

 P.S What are you running underneath the 2x15 cabs?

 


Edited by njw - 16 June 2018 at 10:04pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mini-mad Quote  Post ReplyReply Direct Link To This Post Posted: 16 June 2018 at 10:21pm
Cut the bottom of the cab off and turn it into a single 15+1.4HF

...and then have a sub or two under them.

Double 15s are way to many compromises at once if you ask me. Stupidly big to get up on tripods for small gigs and f##king stupid having them on the floor as the HF just hits just below your chest making anyone standing in from of them a huge defuser and killing the sound for everyone behind.

And if your at the point of getting them up on subs anyway, why the hell do you own double 15s in the 1st place(???)...

A double 10 or 12 would be fine as they are much smaller boxes... but a double 15 is a bit stupid you ask me.


.....but EVEN if they are purely for "big gigs" why the hell don't you own a proper mid top box?

If it sounds like a gorilla is trying to escape, turn it down.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hemisphere Quote  Post ReplyReply Direct Link To This Post Posted: 17 June 2018 at 8:46am
lol

Asks about T/s parameters, gets told to saw his tops in half. "That escalated quickly!"

Switching the CD may be a problem if you've already got one well matched to the horn in the cabinet and don't know how to match a CD to that horn. Of course you can EQ the response to be flat but the less EQ you have to apply the better, partly due to the sound quality but also because of how much it can eat in to the headroom of the driver. Let's say you need to EQ up part of the lower end of the CD's response by 6dB to get a flat response for the system - you've just reduced the power capacity of the driver by 75%.

Choosing the right CD isn't so much about T/s parameters as they're rarely available (although when they are available that can help the process). You'd need to look at the published response plot and take an understanding of how the horn used in that plot would impact the response of a driver and cross that with understanding of how the horns you're looking at would.

You could make simulations of the HF horn candidates in Hornresp to get some idea about this but it's a complicated process. It may be easier just to take the model number of the HF horn in your cabinet and search or ask for recommended drivers, and if none of those are suitable or available to you then look for drivers that seem to have similar performance.

Choosing the right bass drivers you need to look at a few things: power handling and xmax obviously should be equal or greater, but if you're crossing to 1.4's they also need to play high, which is asking a lot and many (most, depending on where you're crossing) 15" drivers can't do it, so you need to be sure the drivers you're buying will sound good at the crossover point. Just because the spec sheet shows frequency response is flat at the crossover doesn't mean it will sound good, and manufacturers' published 'recommended maximum crossover' points will be anywhere from optimistic to total horseshit. Most CD's will sound better if they're not crossed too low also, so it's a balancing act.

Smaller voice coil and lighter cone (lower Mms) are good indicators of high frequency performance in a 15. Crossing your subs at 150Hz will also help things and allow more flexibility on driver choice for the midtops. A 15" that plays well up high might have a slightly lower xmax and power handling than your existing drivers but still be a better choice if you don't mind crossing your subs higher.

You also need to check that they work well with the port tuning of the box. Different drivers in the same box, even those which look fairly suitable can have up to 10Hz -3dB point variation and a few dB of peak around the tuning frequency, depending mostly on how they perform in small boxes, which is easy enough to test.

You can get a good idea of which drivers will work best by roughly simulating your box size and port dimensions in WinISD - doesn't need to be exact, just near enough, then simulate your current drivers and any alternative candidates and pick ones that perform similarly. 

You'll also need to check the excursion plots and the port noise plots, with the power input at the highest level you'll be using. It could be that everything about an alternative driver looks suitable but then you find it exceeds it's xmax far too quickly compared to the old drivers, or the ports will be very noisy (30m/s is the rule of thumb max, but higher is not such a big problem.. check what the current driver is doing and only really worry if it exceeds that by a fair bit, but try and keep it equal or lower.

A lot of this  low frequency/port stuff is only really relevant if you plan to run your midtops without subs sometimes. If you'll never do that then just worry about the high end performance and crossover points, and see how the low crossover point effects power handling and overexcursion.


Edited by Hemisphere - 17 June 2018 at 9:08am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jack_The_Ripper Quote  Post ReplyReply Direct Link To This Post Posted: 17 June 2018 at 10:20am
The 15" drivers i've been thinking about today are the RCF 15MB405 because they're highly efficient, have excellent midrange clarity and seem as though they'd sound nice with a more efficient and powerful compression driver than is in the dual 15" cabs as standard.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hemisphere Quote  Post ReplyReply Direct Link To This Post Posted: 17 June 2018 at 11:01am
Looks like a great option to me.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jack_The_Ripper Quote  Post ReplyReply Direct Link To This Post Posted: 17 June 2018 at 11:20am
The RCF 15MB405 looks like a good option for driver upgrade you mean? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hemisphere Quote  Post ReplyReply Direct Link To This Post Posted: 17 June 2018 at 11:45am
Yes. It seems just the thing for what you're after. 100dB, 1100W AES - You wanted 130dB continuous right? You've almost got that from just the one driver (obviously you should avoid putting 4kw of amp power into these but technically it has that capacity).

Two of them in a 2x15" midtop would be a beast with enough amp power behind it, and it'll need a very strong CD to match two of them. The Faital you suggested will have no chance. 139dB peaks from the pair of 15's, 129dB peak from the CD. Unless you plan to underpower them which is a legit option and would help with clarity (less cone movement, less THD, less IMD).

Generally I agree smaller drivers and other arrangements are more practical and I prefer the sound of smaller drivers as a rule of thumb, but that RCF looks like an excellent option for ultra-high power closed box/reflex tops. If that's what you've got and you're happy with that format, you could do a lot worse.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 17 June 2018 at 11:45am
Originally posted by Jack_The_Ripper Jack_The_Ripper wrote:

The 15" drivers i've been thinking about today are the RCF 15MB405 because they're highly efficient, have excellent midrange clarity and seem as though they'd sound nice with a more efficient and powerful compression driver than is in the dual 15" cabs as standard.


It looks fine. The RCF offers a rise around 400 Hz and peaks at 2 kHz. There are no dips between the 1 Khz - 2 kHz range so your midrange will not suffer under the given scenario.

Best Regards,  



Edited by Elliot Thompson - 17 June 2018 at 11:46am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rish Quote  Post ReplyReply Direct Link To This Post Posted: 17 June 2018 at 1:31pm
Originally posted by mini-mad mini-mad wrote:

Cut the bottom of the cab off and turn it into a single 15+1.4HF

...and then have a sub or two under them.

Double 15s are way to many compromises at once if you ask me. Stupidly big to get up on tripods for small gigs and f##king stupid having them on the floor as the HF just hits just below your chest making anyone standing in from of them a huge defuser and killing the sound for everyone behind.

And if your at the point of getting them up on subs anyway, why the hell do you own double 15s in the 1st place(???)...

A double 10 or 12 would be fine as they are much smaller boxes... but a double 15 is a bit stupid you ask me.


.....but EVEN if they are purely for "big gigs" why the hell don't you own a proper mid top box?


Mini mad , have you ever listened to a faital 15fh560. You will be amazed my friend with right processing and amplification. Dont be too quick to ditch 15" drivers for mid high duties. 

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