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Slap delay (also known as “Slapback”) is a very simple, but extremely efficient audio effect to add depth to your vocals. Even though this effect has been around since the 50s and is mostly associated with Elvis, blues, and rockabilly sounds, it can add fullness and depth to vocals in just about any genre.
But how do you do a slapback delay?
A slapback vocal delay is a delay with very little feedback (usually between 0% and up to 10%). Higher feedback creates a reverb sound but keeping the feedback below 10% creates a tighter sound that still adds depth and fullness to vocals.
That’s the quick answer but we’re going to take a deeper look at the history of the slapback, how modern producers can use it, and how to do it even if your DAW doesn’t have it present already.
A Quick History Of Slap Delay
As I already mentioned, the history of slap delay is closely connected to rockabilly, blues, and the legend Elvis Presley. However, when Elvis was recording he had to do a lot more work to pull off his slapback delay and this video shows you the machinery required to get that classic sound:
Understanding Basic Slap Delay
Slap delay is the use of a delay on your instruments or vocals, but the settings are particular to get the slap delay effect. It’s great for adding a degree of depth to your vocals and you can easily adjust how prominent the effect is.
This video does a great job showing how the effect can work (via a before and after in the blues genre) and the basics of executing it:
- Left and Right sided delays are linked as you do not want the delays to be offset on each side.
- The time of the delay is variable, but most commonly used within the 40-140ish ms range
- The feedback should start at zero, the basic slap delay effect only wants there to be one repeat of the vocal. However, you can experiment and push this up to 10% but beyond that, it’s not exactly a slapback anymore.
- Dry/Wet is at 100% because this effect is being placed on a return track. If you have the delay directly on the affected track then you may adjust this knob to change how much of the effect is mixing into the original vocals.
From these settings, you get one 100ms delayed repeat of your vocals from both L and R at the same time.
As you can hear, this effect is reminiscent of a short reverb effect but is different in the fact that it’s not a continuous release. Because of this, your track has a more open sound which reduces possible muddiness and creates some depth as a reverb would.
Another thing to note is that the delay timing may work best when synced to the main tempo of your song. Try factors such as ½, ¼, and ⅛ of your song tempo and see which mixes in rhythmically.
For example; at 100bpm, a quarter note works as a delay time of 600ms, you can then half or quarter this value a number of times to get delay times that are always on beat with your song.
To calculate these values for any BPM you have a quick formula to figure out the ms for 1 beat in milliseconds: 60,000 / BPM = 1 beat in milliseconds.
Here are some examples:
- 60,000 / 150 = 400ms
- 60,000 / 120 = 500ms
- 60,000 / 100 = 600ms
Advanced Variations on the Basic Slap Delay
There are multiple ways that you can shape and mold the basic slap delay effect to give it a distinct character and fit better in your song’s mix. Depending on how full your mix is, these may or may not be necessary but are always great to experiment with later after you have the basic under control.
Sculpting the Delay Using Filters
Using high and low pass filters on the slap effect of your track is a great way to add separation and depth to your vocals. Here are some sample settings I use for the high-pass and low-pass filters:
As a general guideline, when you use the high-pass filter you should expect the clarity of the delay to be enhanced. When you’re using the low-pass filter, you can expect the depth of the delay to be enhanced. With that in mind, you can experiment and EQ to find the perfect setup for your mix.
Stereo Slap for a Wider, Bigger Sound
In the basic version of the slap delay, we made sure to leave the Left and Right times synced which created one unison delay. However, you can differ the Left and Right outputs to create a bigger sound that covers more of the stereo field.
You want to have the delays between the Left and Right times only differing by a few milliseconds. To find the best number you will have to experiment with it in your track.
Here is an example of a slap delay with the settings described above:
Here are the differences to make a note of:
- The delay times of Left and Right are no longer forced to be synced together.
- The delay times of Left and Right are offset by only 5ms from each other.
If your delay effect does not specifically have a Left and Right timing, then you can pan one delay left and one delay right instead.
Because of the delay and the Left and Right timings being different, your ears will pick up the difference in the milliseconds of timing. As the times are only milliseconds apart they will easily be assumed to be the same audio, creating a wider stereo image.
Additional Slap Delay Effects
If the above effects are not doing your vocals justice, then you can add some further audio effects on top of the echo to give it extra flavor.
Even though I’ve spent a lot of time contrasting slapback delay with reverb, the reverb effect can actually work really well with slapback and they aren’t exclusive to each other. You can also try distortion and if you’re going for more of a rockabilly or punk flavor then some distortion pedals should already be in your repertoire.
What is great about adding these effects to the slap delay itself is that you still have the natural feel of the dry vocal that comes through first, followed by the added effect slightly behind. This gives you the best of both worlds kinds of approach.
What If I Don’t Have a Delay Effect In My DAW?
So far we’ve looked at DAW options that include a delay effect already which then makes it very easy to add your slapback.
But if you don’t have a delay effect, you don’t have to worry.
There are a multitude of delay effect VSTs and pedals, some that are free and some for a cost, but they will all work roughly the same with a few extra features spread between them.
VST Delay Plugins
We’ll start with the VST options since I’m going to assume you’ve already recorded and are in the mixing and master stage but we’ll also look at some pedals that can work too.
Voxengo’s Tempo Delay
Voxengo has a great range of free VST plugins and their delay VST is no different.
You have the ability to all variables of both Left and Right outputs independently which gives a whole range of nuances and shapes you can add to your slap delay around your vocals. You even have tremolo and filters for each side to apply some of the interesting slap delay enhancements and take things to the next level.
Of course, you don’t have to get fancy here and this free plugin can get you up and running with basic slapback delay too. You can read more about the product and download the plugin here.
Waves’s Manny Marroquin Delay
The Manny Marroquin Delay from Waves will give you everything you need for both basic and stereo delay slapback along with a handful of other effects like reverb, distortion, doubler, and phaser. These can all make great additions to your slapback delay and take you beyond the basic sound.
But Waves is in the business of creating premium VSTs and you’ll need to pay for those extra effects. This plugin isn’t going to break the bank or anything but if you’re just looking to add a basic slapback on your vocals or other instruments then you probably don’t need to spend a dime and Voxengo will handle everything you need.
I’m an especially big fan of the doubler and phaser effects (yes, phasers are for more than just Eddie Van Halen) which can add some serious fatness and sense of depth to your vocal sound if it’s feeling a little thin.
Again, you don’t want to start with those extra effects but once you’ve plumped things up with the basic slapback you can start to experiment a bit more and this plugin will give you some room to grow. You can check it out on Wave’s website here.
What About Pedals?
If you want to rock the slapback sound live or at the time of recording, you can use a pedal to create a similar effect.
Note that with these stomp pedals you will need an XLR to jack cable to go from the pedal to your audio interface. It’s also best to have a preamp. Because pedals may have high impedance, it can be hard to hear without the amplification.
Simple pedals can work and you don’t need anything too fancy here but just make sure you have your time low, feedback amount to zero (at least to start), and echo to taste but I usually keep this pretty low as well.
You’ll find plenty of pedals with a ton of settings but if you’re just looking for the basics it’s hard to go wrong with Donner’s Pure Analog Delay Pedal. It’s easy on the budget and extremely simple to use. It’s also built like a brick in the best way and I’m a big fan of their octave pedal which is constructed more or less the same way. You can check it out on Amazon by clicking here.
That’s far from the only pedal that will get you the slapback delay effect and there are dozens (and dozens) of pedals that include the right delay settings you need even if they aren’t marketed specifically as delay pedals.
Closing Thoughts
Slap delay is another simple yet powerful effect that can find its place in any vocal track. It’s up to you to figure out whether it will enhance your vocals or become too muddy, in which case you may choose to leave it out.
It’s a quick and easy way to add depth and width to your vocals whilst also preserving the upfront and natural sound of the audio, providing you don’t go too heavy on the delay!
The above pedals and VST’s are tried and trusted, they are great at what they do whatever the cost, but it’s important to experiment and find what works best for yourself and your needs.